Colonic transit time in long-term dialysis patients

Intestinal Dysmotility and Associated Disorders in Intestinal Muscle of Methylglyoxal-Treated Mice

BACKGROUND

Peritoneal dialysis (PD) is a renal replacement therapy approach to treat end-stage renal failure. However, complications such as gastrointestinal dysmotility occur in patients undergoing PD, and the mechanisms underlying these complications have not been elucidated. We hypothesized that inflammation and dysfunction of the interstitial cells of Cajal (ICC) contribute to the PD-induced gastrointestinal dysmotility.

METHODS

Mice were intraperitoneally administered a dialysate containing methylglyoxal (40 mM) every other day for 2 weeks to mimic the gastrointestinal complications in patients undergoing long-term PD. The gastrointestinal transit capacity was evaluated using fluorescent dyes that were forcibly administered orally. To evaluate the inflammation and function of the ICC in the intestinal muscles, we performed real-time polymerase chain reaction and immunohistochemical staining and measured spontaneous contractions ex vivo.

KEY RESULTS

The intestinal transit capacity was significantly reduced in the methylglyoxal-treated group compared to that in the control group. In the inflammatory evaluation, the number of neutrophils and macrophages in the intestinal muscles significantly increased in the methylglyoxal-treated group compared to the control group. Moreover, the mRNA expression levels of Tnf, Il1b, and Il6 were upregulated in the intestinal muscle from the methylglyoxal-treated group. The mRNA expression of Kit, an interstitial cell of Cajal marker, was significantly decreased in the methylglyoxal-treated group. In addition, the frequency of spontaneous contractions, an index of ICC function, was decreased in the methylglyoxal-treated group.

CONCLUSIONS AND INFERENCE

Our data suggest that the PD-induced gastrointestinal dysmotility might be due to inflammation and dysfunction of the ICC in intestinal muscles.

Global, regional, and National Burden of chronic kidney disease attributable to dietary risks from 1990 to 2021

Background

Dietary risks are increasingly reported as a cause of chronic kidney disease (CKD). However, the trends in the burden of CKD attributable to dietary risks have yet to be fully elucidated.

Methods

This study extracted two major indicators related to CKD caused by dietary risks from the Global Burden of Disease (GBD) database for the years 1990 to 2021, including deaths and disability-adjusted life years (DALYs). It used estimated annual percentage change (EAPC) and percentage change to assess the trends in the burden of CKD caused by dietary risks. The relationship between Socio-demographic Index (SDI) and disease burden was also further analyzed. Additionally, we utilized the contemporary age-period-cohort model from NORDPRED to project future burden of CKD attributable to dietary risks.

Results

In 2021, globally, the number of deaths due to CKD caused by dietary risks was 317,010, and the number of DALYs was 7,971,281, approximately 2-3 times that of 1990, and it was expected to continue to rise before 2040. The global death rates and DALY rates of CKD related to dietary risks had increased, with EAPCs of 0.63 (95% CI: 0.57 to 0.69) and 0.39 (95% CI: 0.35 to 0.42), respectively. From a gender perspective, men were more likely to suffer from CKD due to dietary risks. From an age pattern perspective, in 2021, the number of deaths due to CKD caused by dietary risks peaked among men aged 70-74 and women aged 85-89. Additionally, the highest number of DALYs due to CKD caused by dietary risks was observed among men and women aged 65-69. In terms of socioeconomic factors, from 1990 to 2021, as the SDI increased, the age-standardized death rates and DALY rates due to CKD caused by dietary risks generally decreased. Among the seven dietary habits related to dietary risks, low vegetable intake, low fruit intake, and high sodium intake had the greatest impact.

Conclusion

In summary, over the past 32 years, the burden of CKD attributable to dietary risks has rapidly increased globally, and it is expected to continue rising until 2040. Therefore, interdisciplinary actions involving education, policy, and healthcare should be taken to mitigate this growing trend.

Gastrointestinal disease in end-stage renal disease

When kidney function declines to a point where it can no longer maintain life and requires renal replacement therapy (i.e. renal transplant or dialysis), it is called end-stage renal disease (ESRD). Patients with ESRD often experience a range of gastrointestinal (GI) symptoms, with prevalence rates reported as high as 77%-79%. These symptoms and pathologies arise from various factors, including electrolyte imbalance, fluid imbalance, toxin buildup, uremia, medications, dietary and lifestyle restrictions, and the effects of dialysis. GI diseases in patients with renal failure can be further categorized into upper GI, small bowel, and lower GI issues. Common conditions include gastroesophageal reflux disease, nausea and vomiting, dysmotility within the esophagus and stomach, upper GI bleeding, peptic ulcer bleeding, angioectasia, irritable bowel syndrome, mesenteric ischemia, angiodysplasia, diverticular disease, constipation, pancreatitis, and diseases associated with peritoneal dialysis peritonitis and peritoneal stenosis. This review assesses the existing literature on the different GI diseases among individuals with ESRD, shedding light on their pathophysiology and prevalence.

Benefits and Pitfalls of Uraemic Toxin Measurement in Peritoneal Dialysis

Chronic kidney disease is a global health burden with a rising incidence and prevalence in developed and developing nations. Once established, it results in a progressive accumulation of a myriad of uraemic toxins. Peritoneal dialysis (PD) uses the body's peritoneal membrane to remove these toxins across a semipermeable membrane to restore and maintain homeostasis. Traditionally, dialysis adequacy has been measured through clearance of urea and creatinine. However, numerous studies have shown marginal links comparing the clearance of urea and creatinine with clinical outcomes reflected in the recent changes to the ISPD guidelines on dialysis adequacy. Instead, attention has focused on protein-bound uraemic toxins (PBTs). Produced by gut bacteria, these molecules are highly protein-bound and poorly removed by either dialysis or absorptive agents. Elevated concentrations of molecules such as p-cresyl sulfate and indoxyl sulfate have been associated with abnormal cellular function and poor patient outcomes. However, widespread use of these measures to determine dialysis adequacy has been limited by the need for specialized techniques required for measurement. Altering the gut microbiome to reduce generation of PBTs through increased dietary fiber might be an alternate approach to better patient outcomes, with some initial positive reports. This report explores advantages and limitations of measuring uraemic toxins in PD, now and in the foreseeable future.

Association between constipation and incident chronic kidney disease in the UK Biobank study

Despite previous studies supporting a close relationship between constipation and chronic kidney disease (CKD), the potential impact of constipation on incident CKD and the role of laxatives remains uncertain. We analyzed longitudinal data from the UK Biobank, which links baseline assessment data with follow-up data from hospital episode statistics and general practice records. Constipation was defined with diagnostic codes or regular use of laxatives at baseline as reported in the questionnaire. Cox proportional hazard models were used to evaluate the association between constipation and incident CKD. After excluding individuals with pre-existing CKD or missing covariates, 118,020 participants with general practice follow-up data were included in the main analysis. Over a median follow-up of 7.4 years, 6,833 (5.8%) patients developed CKD. Constipation was significantly associated with increased risk of CKD development in the multivariable adjusted models (hazard ratio [HR] 1.51, 95% confidence interval [CI] 1.37-1.67) for ICD-defined constipation, HR 1.34, 95% CI 1.23-1.47 for constipation defined by ICD codes or laxative use). Patients with ICD-defined constipation, even when taking laxatives, were found to have a higher risk of incident CKD than those without constipation (HR 1.42, 95% CI 1.08-1.85). We found no moderating effects of laxative use on the association between constipation and incident CKD. Constipation is independently associated with incident CKD in the large population-based longitudinal cohort. These findings highlight constipation as a potential risk factor or predictor of CKD development. Further research is warranted to elucidate the role of laxatives in controlled study designs.

Intestinal transport of organic food compounds and drugs: A scoping review on the alterations observed in chronic kidney disease

BACKGROUND AND AIMS

Around 850 million people worldwide are affected by chronic kidney disease (CKD). Patients with CKD often develop malnutrition and sarcopenia and changes in the pharmacokinetics of drugs. A reduced kidney function partially explains the prolonged half-life of certain drugs due to decreased renal clearance, which leads to an increased risk of adverse effects. While the intestine plays a fundamental role in this context, a systematic review of the effects of CKD on intestinal transport is lacking. We aimed to systematically summarize all the available evidence on intestinal transport of organic food components (carbohydrates/sugar, proteins/amino acids, fats, vitamins) and drugs (including drug transporters) in CKD.

METHODS

We conducted a systematic search of all the articles published until the 1st of April 2024, on five databases i.e. Embase, PubMed, Web of Science Core Collection, Cochrane Library, and Scopus. This systematic review was registered on the Open Science Framework (OSF) (osf.io/5e6wb) and was carried out according to the PRISMA 2020 guidelines.

RESULTS

From 9205 articles identified, 68 met the inclusion criteria. Absorption of organic food compounds seems to be altered, in general, and reduced for vitamins. The expression of intestinal efflux drug transporters may be altered in CKD.

CONCLUSIONS

Despite alterations in intestinal transport is suggested to be altered in CKD, the lack of recent studies, the paucity of human data and the heterogeneity of the methodologies used underscore the need for more research on the effect of CKD and uremia on intestinal transport.

[Nutrition for patients on dialysis]

Dietary recommendations for patients on dialysis are changing as our understanding of enteral microbiotal metabolism and bioavailability of nutrients from food improves.A diet low in phosphate and potassium is recommended for patients on hemodialysis. However, the absolute content does not reflect bioavailability: How much phosphate or potassium is taken up depends on food source (plant vs. animal) and to which grade it is processed. While both are nearly 100% bioavailable from industrially processed foods (additives such as dipotassium-phosphate and other salts), a much lower proportion is taken up from unprocessed plant foods high in fibre (ca. 20-40%). The DIET-HD study showed no significant association between dietary potassium and serum potassium in > 8 000 dialysis patients; and those with the highest low-processed, fresh plant-food consumption have the best survival. Dietary fibre improves colon transit time and thereby lessens symptoms of constipation. A diet low in sodium improves blood pressure and volume management in dialysis patients. The energy and protein requirements on dialysis are high: 25-35 kcal and 1-1,2 g protein per kg body weight per day (in relation to "ideal" body weight, if patient is overweight). Protein energy wasting is associated with higher stages of kidney disease, and malnutrition is associated with worse survival on dialysis. Nutritional status should be assessed on a regular basis using validated scores, and malnutrition should be addressed and treated.

The effect of synbiotic supplementation on plasma levels of advanced glycation end products and cardiovascular risk factors in hemodialysis patients: A double-blind clinical trial

There is increasing evidence supporting the relationship between imbalance of gut microbiota and development of chronic kidney and cardiovascular diseases. This study aimed to investigate the effect of synbiotic supplementation on plasma levels of advanced glycation end products (AGEs) and cardiovascular risk factors in hemodialysis (HD) patients. In this randomized, double-blind, placebo-controlled clinical trial, 36 HD patients were randomly allocated into two groups to receive two synbiotic supplements (n = 19) or placebo (n = 17) daily for 12 weeks. Levels of AGEs, fibrinogen, hemoglobin A1c (HbA1c), and other measures were assessed at the beginning and end of the study. The data were analyzed using independent t-tests, paired t-tests, and analysis of covariance (ANCOVA). At the end of the study, the plasma levels of AGEs increased significantly in both the synbiotic (p < .001) and control (p = .001) groups, but the difference between the groups was not significant (p = .272). Plasma levels of fibrinogen decreased specifically within the synbiotic group (p = .007), and a statistically significant disparity between the groups persisted at the study's conclusion (p = .016). The mean levels of blood urea nitrogen (BUN) decreased (p < .05) in both groups, but there was no difference between the two groups at the end of the study (p = .116). No significant differences were observed in other measured biomarkers. Synbiotic supplementation improved plasma fibrinogen and BUN levels in HD patients, but did not significantly improve AGEs and HbA1c. Further investigations are needed to investigate the effect of probiotics on AGEs in HD patients at different stages of kidney disease.

Insights into the gut-kidney axis and implications for chronic kidney disease management in cats and dogs

Chronic kidney disease (CKD) in cats and dogs presents significant clinical challenges, with emerging research highlighting the pivotal role of the gut-kidney axis in its pathogenesis and management. Gut dysbiosis, characterized by alterations in the gut microbiome composition and function, contributes to microbial dysmetabolism of key nutrients causing uremic toxin accumulation and disruptions in amino acid, bile acid and fatty acid profiles. These disturbances in turn exacerbate renal dysfunction and systemic inflammation. Recent research in veterinary medicine, particularly in cats, supports the gut microbiome and microbial-derived metabolites as novel therapeutic targets. Potential therapeutic strategies targeting the gut microbiome and microbial dysmetabolism, including dietary management, probiotics, adsorbents, and addressing constipation, offer promising avenues for intervention to restore metabolic balance and preserve renal function. This review highlights the microbial influence on renal health and focuses on potential therapeutic strategies available to veterinarians to optimize the management of CKD in cats and dogs.

Chronic kidney disease and physiologically based pharmacokinetic modeling: a critical review of existing models

INTRODUCTION

Physiologically based pharmacokinetic (PBPK) modeling is a paradigm shift in this era for determining the exposure of drugs in pediatrics, geriatrics, and patients with chronic diseases where clinical trials are difficult to conduct.

AREAS COVERED

This review has collated data regarding published PBPK models on chronic kidney disease (CKD), including the drug and system-specific input model parameters and model evaluation criteria. Four databases were used from 13th June 2023 to 10th July 2023 for identifying the relevant studies that met the inclusion/exclusion criteria. Alterations in plasma protein (albumin/alpha-1 acid glycoprotein), gastric emptying time, hematocrit, small intestinal transit time, the abundance of cytochrome (CYP) 450 enzymes, glomerular filtration rate, and physicochemical parameters for different drugs were explicitly elaborated from earlier reported studies. Moreover, model evaluation depicted that models in CKD for most of the included drugs were within the allowed two-fold error range.

EXPERT OPINION

This review will provide insights for researchers on applying PBPK models in managing patients with different levels of CKD to prevent undesirable side effects and increase the effectiveness of drug therapy.

Gutted: constipation in children with chronic kidney disease and on dialysis

Functional constipation is a common problem in otherwise healthy children. Children with chronic kidney disease (CKD) and on dialysis have additional disease-related risk factors including the uremic milieu, fluid and dietary restrictions, and decreased physical activity, as well as treatment-related risk factors such as dialysis therapy and polypharmacy that contribute to and compound the problem. Constipation causes significant distress for children and their caregivers. In children on peritoneal dialysis, severe constipation can impede catheter function and ultrafiltration. Accumulating evidence points to a possible bidirectional relationship between constipation and CKD, potentially mediated by gut dysbiosis with consequent increased generation of gut-derived uremic toxins and disruption of intestinal epithelium integrity leading to translocation of noxious luminal contents into the circulation inducing systemic inflammation. Effective management of constipation is required but there is little published data on the safety and effectiveness of treatments in adults or children with CKD. In this review, we discuss the diagnosis and epidemiology of functional constipation, provide an overview of its pathophysiology, summarize the therapeutic management, and reflect on the challenges in children with CKD.

Constipation in Patients With Chronic Kidney Disease

Constipation is a frequent symptom in patients with chronic kidney disease (CKD). This review outlines the mechanisms and management of constipation in patients with CKD from a physician's perspective. Common causes of constipation in patients with CKD include concomitant medications, low dietary fiber intake, water-restricted diet, lack of physical activity, altered gut microbiota, and reduced gastrointestinal motility. Constipation has a negative impact on overall health, and, in particular, the presence of constipation has been associated with worsening kidney function and increased risk of developing advanced stages of CKD. Although lifestyle and dietary modifications may not always be practical for patients with CKD, they are recommended because they are beneficial as they lower mortality in patients with CKD. The use of laxatives containing magnesium salts, bulking agents, and osmotic laxatives may have insufficient efficacy and may be associated with adverse effects. In contrast, lactulose and lubiprostone have been shown to exhibit reno-protective effects. Linaclotide and plecanatide have very limited systemic absorption and appear safe in patients with CKD. Tenapanor reduces paracellular intestinal phosphate absorption in addition to blocking sodium uptake by enterocytes, and provides additional benefit in patients patients with CKD who have hyperphosphatemia and constipation. Prucalopride leads to improvements in bowel function and constipation-related symptoms in cases in which response to conventional laxatives are inadequate. However, the dose of prucalopride should be reduced to 1 mg once daily for patients with CKD. In conclusion, there are important advances on the impact and treatment of constipation in patients with CKD.

Effect of external therapies of traditional Chinese medicine on constipation in patients with CRF: A meta-analysis

OBJECTIVE

The purpose of this study was to evaluate the curative effect of external therapies of traditional Chinese medicine on constipation in patients with chronic renal failure and to provide scientific theoretical basis for clinical practice.

METHOD

We searched the English database of PubMed, EMBASE, the Cochrane Library and the Web of Science and Chinese database of CNKI, Wan fang database, VIP Database and China Biomedical Literature Database up to December 2022. Randomized controlled trials (RCTs) involving constipation in patients with CRF that compared external therapies of traditional Chinese medicine and routine treatment to routine treatment were eligible for the analysis. A meta-analysis of the outcome indicators including total efficiency, weekly defecation times, defecation time, defecation difficulty score, patient-assessment of constipation quality of life and adverse events of treatment were performed. The analysis was performed by using Review Manager version 5.3.

RESULT

A total of 23 studies were included, with 1764 patients. Meta-analysis results showed that compared with the control group, the test group could significantly increase weekly defecation times(MD = 0.94, 95%CI(0.70, 1.18), Z = 7.74, P < 0.00001), reduce defecation time(MD = -2.92, 95%CI(-3.69, -2.16), Z = 7.49, P < 0.00001), reduce defecation difficulty score(MD = -1.92, 95%CI(-2.45, -1.39), Z = 7.11, P < 0.00001), improve the quality of life in patients with constipation(MD = -7.57, 95%CI(-10.23, -4.91), Z = 5.58, P < 0.00001) and obtain a higher total effective rate of treatment(OR = 4.53, 95%CI(3.27, 6.29), Z = 9.07, P < 0.00001). In terms of safety, there was no statistical significance in the incidence of adverse events between two groups(OR = 0.35, 95%CI(0.04, 2.95), Z = 0.96, P = 0.34).

CONCLUSION

The combination of external therapies of traditional Chinese medicine and routine treatment could achieve an excellent curative effect, and there was no specific adverse event. However because of the limited level of current evidence, more high-quality trials are needed in the future.5.

Saliva as Biomarker for Oral and Chronic Degenerative Non-Communicable Diseases

Saliva is a very complex fluid and it is essential to maintain several physiological processes and functions, including oral health, taste, digestion and immunological defenses. Saliva composition and the oral microbiome can be influenced by several factors, like diet and smoking habits, and their alteration can represent an important access point for pathogens and, thus, for systemic illness onset. In this review, we explore the potentiality of saliva as a new tool for the early detection of some pathological conditions, such as oral diseases, chronic degenerative non-communicable diseases, among these chronic kidney disease (CKD). We also examined the possible correlation between oral and systemic diseases and oral and gut microbiota dysbiosis. In particular, we deeply analyzed the relationship between oral diseases and CKD. In this context, some salivary parameters can represent a new device to detect either oral or systemic pathologies. Moreover, the positive modulation of oral and gut microbiota induced by prebiotics, postbiotics, or symbiotics could represent a new possible adjuvant therapy in the clinical management of oral diseases and CKD.

Gut microbiome studies in CKD: opportunities, pitfalls and therapeutic potential

Interest in gut microbiome dysbiosis and its potential association with the development and progression of chronic kidney disease (CKD) has increased substantially in the past 6 years. In parallel, the microbiome field has matured considerably as the importance of host-related and environmental factors is increasingly recognized. Past research output in the context of CKD insufficiently considered the myriad confounding factors that are characteristic of the disease. Gut microbiota-derived metabolites remain an interesting therapeutic target to decrease uraemic (cardio)toxicity. However, future studies on the effect of dietary and biotic interventions will require harmonization of relevant readouts to enable an in-depth understanding of the underlying beneficial mechanisms. High-quality standards throughout the entire microbiome analysis workflow are also of utmost importance to obtain reliable and reproducible results. Importantly, investigating the relative composition and abundance of gut bacteria, and their potential association with plasma uraemic toxins levels is not sufficient. As in other fields, the time has come to move towards in-depth quantitative and functional exploration of the patient's gut microbiome by relying on confounder-controlled quantitative microbial profiling, shotgun metagenomics and in vitro simulations of microorganism-microorganism and host-microorganism interactions. This step is crucial to enable the rational selection and monitoring of dietary and biotic intervention strategies that can be deployed as a personalized intervention in CKD.

Comparison of gastrointestinal symptoms and findings in renal replacement therapy modalities

Objective

Chronic kidney disease (CKD) affects gastrointestinal system (GIS) and causes histological, functional and mucosal changes. There are scarce data investigating GIS symptoms and findings in patients with CKD stage III-V, receiving hemodialysis (HD) and peritoneal dialysis (PD). In this study, we aimed to evaluate the frequency of gastrointestinal symptoms and findings and compare between renal replacement therapies.

Method

A total of 290 patients (97 in CKD stage III-V, 92 PD, 101 HD) were included in this study. Gastrointestinal complaints, diseases, background characteristics of patients and drugs they used were questioned by interviews, forms were filled and examinations of patients were performed. Results of upper GIS endoscopy, colonoscopy, abdominal ultrasonography and tomography of patients were evaluated.

Results

The most common signs were dyspepsia (50%), nausea (45%) and epigastric pain (44%) among all patients, generally. Gastrointestinal disorders like gastritis (62%) and gastroesophageal reflux (39%) were frequent in patients. Prevalence of patients with weight loss was 20% in predialysis and 8% in PD and the ratio was higher in predialysis group statistically significantly (p = 0,016). The prevalence of gastritis was 70% in PD, 55% in HD and the prevalence of hemorrhoids was 24% in PD and 12% in HD. The prevalence of gastritis and hemorrhoids was higher in the PD group than in the HD group statistically significantly (p = 0.043, p = 0.028), otherwise, there wasn’t a difference between the PD and predialysis groups, statistically significantly.

Conclusion

This study showed that; gastrointestinal symptoms and disorders were very common in CKD, besides this; while gastritis and hemorrhoids were more frequent in the PD, esophagitis and hiatal hernia were more frequent in the HD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02893-6.

Microbiota and glomerulonephritis: An immunological point of view

Glomerular injury is the major cause of chronic kidney diseases (CKD) worldwide and is characterized by proteinuria. Glomerulonephritis (GN) has a wide spectrum of etiologies, the intensity of glomerular damage, histopathology, and clinical outcomes that can be associated with the landscape of the nephritogenic immune response. Beyond impaired immune responses and genetic factors, recent evidence indicates that microbiota can be contributed to the pathogenesis of GN and patients' outcomes by impacting many aspects of the innate and adaptive immune systems. It is still unknown whether dysbiosis induces GN or it is a secondary effect of the disease. Several factors such as drugs and nutritional problems can lead to dysbiosis in GN patients. It has been postulated that gut dysbiosis activates immune responses, promotes a state of systemic inflammation, and produces uremic toxins contributing to kidney tissue inflammation, apoptosis, and subsequent proteinuric nephropathy. In this review, the impact of gastrointestinal tract (GI) microbiota on the pathogenesis of the primary GN will be highlighted. The application of therapeutic interventions based on the manipulation of gut microbiota with special diets and probiotic supplementation can be effective in GN.

The prevalence of constipation in end-stage kidney disease patients: A cross-sectional observation study

The aim of our study was to determine the prevalence, distribution, and risk factors for constipation in peritoneal dialysis (PD) and hemodialysis (HD) patients in our center. In this cross-sectional study, 858 dialysis patients over 18 years of age (681 HD cases and 177 PD cases from our hospital) were enrolled. A constipation assessment scale (CAS) questionnaire was used to evaluate constipation status. Logistic regression analysis was performed to define independent risk factors for CAS scores. The prevalence of constipation in HD and PD patients was 52.7% and 77.4%, respectively. The mean CAS score in HD and PD patients was 1.73 ± 2.31 and 2.42 ± 2.34, respectively. Age ≥ 65 and diabetic kidney disease for renal failure were independent risk factors associated with constipation in the HD population (OR = 1.67, 95% CI: 1.15-2.90, P = .019; OR = 3.31, 95% CI: 1.65-6.11, P < .001, respectively). In the PD population, only serum prealbumin was independently associated with constipation (OR = 0.88, 95% CI: 0.79-0.96, P = .007). The multivariable logistic regression analysis demonstrated that PD modality, age ≥ 65 and diabetic kidney disease for renal failure were independent risk factors for constipation (OR = 2.15, 95% CI: 1.41-3.32, P < .001; OR = 1.65, 95% CI: 1.13-2.33, P = .003; OR = 3.19, 95% CI: 1.76-5.093, P < .001, respectively). The prevalence of constipation in PD patients was higher than that in HD patients in our center. PD modality for renal replacement therapy, age ≥ 65 and diabetic kidney disease for renal failure were closely associated with constipation in dialysis patients.

Epidemiology of peritoneal dialysis outcomes

Peritoneal dialysis (PD) is an important home-based treatment for kidney failure and accounts for 11% of all dialysis and 9% of all kidney replacement therapy globally. Although PD is available in 81% of countries, this provision ranges from 96% in high-income countries to 32% in low-income countries. Compared with haemodialysis, PD has numerous potential advantages, including a simpler technique, greater feasibility of use in remote communities, generally lower cost, lesser need for trained staff, fewer management challenges during natural disasters, possibly better survival in the first few years, greater ability to travel, fewer dietary restrictions, better preservation of residual kidney function, greater treatment satisfaction, better quality of life, better outcomes following subsequent kidney transplantation, delayed need for vascular access (especially in small children), reduced need for erythropoiesis-stimulating agents, and lower risk of blood-borne virus infections and of SARS-CoV-2 infection. PD outcomes have been improving over time but with great variability, driven by individual and system-level inequities and by centre effects; this variation is exacerbated by a lack of standardized outcome definitions. Potential strategies for outcome improvement include enhanced standardization, monitoring and reporting of PD outcomes, and the implementation of continuous quality improvement programmes and of PD-specific interventions, such as incremental PD, the use of biocompatible PD solutions and remote PD monitoring.

The use of peritoneal dialysis (PD) can be advantageous compared with haemodialysis treatment, although several barriers limit its broad implementation. This review examines the epidemiology of peritoneal dialysis (PD) outcomes, including clinical, patient-reported and surrogate PD outcomes.

Peritoneal dialysis (PD) has distinct advantages compared with haemodialysis, including the convenience of home treatment, improved quality of life, technical simplicity, lesser need for trained staff, greater cost-effectiveness in most countries, improved equity of access to dialysis in resource-limited settings, and improved survival, particularly in the first few years of initiating therapy.

Important barriers can hamper PD utilization in low-income settings, including the high costs of PD fluids (owing to the inability to manufacture them locally and the exorbitant costs of their import), limited workforce availability and a practice culture that limits optimal PD use, often leading to suboptimal outcomes.

PD outcomes are highly variable around the world owing in part to the use of variable outcome definitions, a heterogeneous practice culture, the lack of standardized monitoring and reporting of quality indicators, and kidney failure care gaps (including health care workforce shortages, inadequate health care financing, suboptimal governance and a lack of good health care information systems).

Key outcomes include not only clinical outcomes (typically defined as medical outcomes based on clinician assessment or diagnosis) — for example, PD-related infections, technique survival, mechanical complications, hospitalizations and PD-related mortality — but also patient-reported outcomes. These outcomes are directly reported by patients and focus on how they function or feel, typically in relation to quality of life or symptoms; patient-reported outcomes are used less frequently than clinical outcomes in day-to-day routine care.

Gut–Kidney Axis Investigations in Animal Models of Chronic Kidney Disease

Chronic kidney disease (CKD) is an incurable disease in which renal function gradually declines, resulting in no noticeable symptoms during the early stages and a life-threatening disorder in the latest stage. The changes that accompany renal failure are likely to influence the gut microbiota, or the ecosystem of micro-organisms resident in the intestine. Altered gut microbiota can display metabolic changes and become harmful to the host. To study the gut–kidney axis in vivo, animal models should ideally reproduce the disorders affecting both the host and the gut microbiota. Murine models of CKD, but not dog, manifest slowed gut transit, similarly to patient. Animal models of CKD also reproduce altered intestinal barrier function, as well as the resulting leaky gut syndrome and bacterial translocation. CKD animal models replicate metabolic but not compositional changes in the gut microbiota. Researchers investigating the gut–kidney axis should pay attention to the selection of the animal model (disease induction method, species) and the setting of the experimental design (control group, sterilization method, individually ventilated cages) that have been shown to influence gut microbiota.

The quality of life and comfort levels of hemodialysis patients with constipation: A descriptive and cross-sectional study

INTRODUCTION

This study was conducted to determine the constipation-related quality of life, bowel habits, and comfort levels of constipated hemodialysis patients. It is known that the prevalence of constipation is high in hemodialysis patients.

METHODS

This was a cross-sectional and correlational study. The study included 164 hemodialysis patients who were determined to have constipation by examining the constipation statuses of 385 patients based on the Rome-IV criteria. The study was reported according to the STrengthening the Reporting of OBservational studies in Epidemiology Declaration.

FINDINGS

It was determined that as the constipation-related quality of life of the patients increased, their comfort levels also increased. Constipation-related quality of life increased in parallel with an increasing Bristol Stool Scale (BSS) score and an increasing number of bowel movements. The BSS scores of the patients were found to have a significant positive correlation with the patients' bowel movement frequencies and a significant negative correlation with their constipation frequencies. There was a negative correlation between years of dialysis and bowel movement frequencies. The presence of a previous gastrointestinal system complaint, the presence of an impact of constipation on the patient's dialysis session, and comfort levels were determined to be significant predictors of constipation-related quality of life that explained 26.3% of the total variance in constipation-related quality of life.

DISCUSSION

In patients receiving hemodialysis treatment, constipation is an important and frequently encountered problem. Constipation leads to a reduction in quality of life and hemodialysis-related comfort.

Chronic Kidney Disease: Role of Diet for a Reduction in the Severity of the Disease

Chronic kidney disease affects ~37 million adults in the US, and it is often undiagnosed due to a lack of apparent symptoms in early stages. Chronic kidney disease (CKD) interferes with the body's physiological and biological mechanisms, such as fluid electrolyte and pH balance, blood pressure regulation, excretion of toxins and waste, vitamin D metabolism, and hormonal regulation. Many CKD patients are at risk of hyperkalemia, hyperphosphatemia, chronic metabolic acidosis, bone deterioration, blood pressure abnormalities, and edema. These risks may be minimized, and the disease's progression may be slowed through careful monitoring of protein, phosphorus, potassium, sodium, and calcium, relieving symptoms experienced by CKD patients. In this review, the current Kidney Disease Outcomes Quality Initiative (KDOQI) recommendations are highlighted, reflecting the 2020 update, including explanations for the pathophysiology behind the recommendations. The Dietary Approaches to Stop Hypertension, the Mediterranean diet, and the whole foods plant-based diet are currently being examined for their potential role in delaying CKD progression. Biological explanations for why the whole foods plant-based diet may benefit CKD patients compared to diets that include animal products are examined. Strong evidence continues to support the importance of diet meeting the daily requirement in the prevention and progression of kidney disease, and medical nutrition therapy with a registered dietitian is a critical aspect in medical intervention for CKD.

A Physiological Approach to Pharmacokinetics in Chronic Kidney Disease

The conventional approach to approximating the pharmacokinetics of drugs in patients with chronic kidney disease (CKD) only accounts for changes in the estimated glomerular filtration rate. However, CKD is a systemic and multifaceted disease that alters many body systems. Therefore, the objective of this exercise was to develop and evaluate a whole-body mechanistic approach to predicting pharmacokinetics in patients with CKD. Physiologically based pharmacokinetic models were developed in PK-Sim v8.0 (www.open-systems-pharmacology.org) to mechanistically represent the disposition of 7 compounds in healthy human adults. The 7 compounds selected were eliminated by glomerular filtration and active tubular secretion by the organic cation transport system to varying degrees. After a literature search, the healthy adult models were adapted to patients with CKD by numerically accounting for changes in glomerular filtration rate, kidney volume, renal perfusion, hematocrit, plasma protein concentrations, and gastrointestinal transit. Literature-informed interindividual variability was applied to the physiological parameters to facilitate a population approach. Model performance in CKD was evaluated against pharmacokinetic data from 8 clinical trials in the literature. Overall, integration of the CKD parameterization enabled exposure predictions that were within 1.5-fold error across all compounds and patients with varying stages of renal impairment. Notable improvement was observed over the conventional approach to scaling exposure, which failed in all but 1 scenario in patients with advanced CKD. Further research is required to qualify its use for first-in-CKD dose selection and clinical trial planning for a wider selection of renally eliminated compounds, including those subject to anion transport.

Gut Microbiome-Derived Uremic Toxin Levels in Hemodialysis Patients on Different Phosphate Binder Therapies

Introduction

Constipation is prevalent in patients with kidney failure partly due to the use of medication, such as phosphate binders. We hypothesized that serum levels of gut microbiome-derived uremic toxins (UTOX) may be affected by the choice of phosphate binder putatively through its impact on colonic transit time. We investigated two commonly prescribed phosphate binders, sevelamer carbonate (SEV) and sucroferric oxyhydroxide (SFO), and their association with gut microbiome-derived UTOX levels in hemodialysis (HD) patients.

Methods

Weekly blood samples were collected from 16 anuric HD participants during the 5-week observational period. All participants were on active phosphate binder monotherapy with either SFO or SEV for at least 4 weeks prior to enrollment. Eight UTOX (7 gut microbiome-derived) and tryptophan were quantified using liquid chromatography-mass spectrometry. Serum phosphorus, nutritional, and liver function markers were also measured. For each substance, weekly individual levels, the median concentration per participant, and differences between SFO and SEV groups were reported. Patient-reported bowel movements, by the Bristol Stool Scale (BSS), and pill usage were assessed weekly.

Results

The SEV group reported a 3.3-fold higher frequency of BSS stool types 1 and 2 (more likely constipated, p < 0.05), whereas the SFO group reported a 1.5-fold higher frequency of BSS stool types 5–7 (more likely loose stool and diarrhea, not significant). Participants in the SFO group showed a trend toward better adherence to phosphate binder therapy (SFO: 87.6% vs. SEV: 66.6%, not significant). UTOX, serum phosphorus, nutritional and liver function markers, and tryptophan were not different between the two groups.

Conclusion

There was no difference in the gut microbiome-derived UTOX levels between phosphate binders (SFO vs. SEV), despite SFO therapy resulting in fewer constipated participants. This pilot study may inform study design of future clinical trials and highlights the importance of including factors beyond bowel habits and their association with UTOX levels.

Efficacy of Lactulose versus Senna Plus Ispaghula Husk Among Patients with Pre-Dialysis Chronic Kidney Disease and Constipation: A Randomized Controlled Trial

Background

Constipation is a common problem among patients with advanced chronic kidney disease (CKD), leading to a loss of quality of life. Pharmacologic treatments are in common use, but whether lactulose and senna plus ispaghula husk is effecive to treat constipation among patients with pre-dialysis CKD remains unknown.

Objective

The aim of the study was to compare efficacy of lactulose and senna plus ispaghula husk to treat constipation among patients with pre-dialysis CKD.

Methods

A study was conducted among patients with pre-dialysis CKD receiving a diagnosis of constipation by ROME IV criteria. All subjects were randomly assigned to receive either lactulose or senna plus ispaghula husk daily for 14 days. After a 7-day washout period, the patients were switched to the other substance for another 14 days. Primary outcome was complete spontaneous bowel movement (CSBM) weekly, assessed using a stool diary after each laxative. Secondary outcome measure was the change of stool appearance using the Bristol stool form scale (BSFS).

Results

A total of 22 patients underwent randomization. Baseline CSBM and BSFS were 3.4 ± 1.4 and 2.3 ± 1.2 time/week, respectively. At the end of the study, the mean CSBM weekly increased in the lactulose group (mean difference 1.3 ± 1.6, P < 0.001) and the senna plus ispaghula husk group (mean difference 2.1 ± 2.1, P < 0.001) from baseline. Comparing CSBM between lactulose and senna plus ispaghula husk exhibited no significant difference (95% CI -1.2 to 0.06; P = 0.276). BSFS was significantly changed after using ispaghula husk with senna, the mean ± SD of BSFS changed to 1.7 ± 1.8 (p = 0.001) and after use lactulose, the mean ± SD of BSFS changed to 1.6 ± 1.8 (p = 0.001). No significant BSFS change was observed between groups regarding stool appearance. No serious adverse event in either group was found.

Conclusion

Lactulose and senna plus ispaghula husk were similar in efficacy to treat constipation among patients with pre-dialysis CKD.

Trial Registration

Thai Clinical Trials number is TCTR20200818006. Retrospectively Registered 18 August 2020.

Intestinal microbiota and kidney diseases

Large microbial communities reside in the gut as an endogenous organ and interact with the host physiology through symbiotic relationships, affecting health. Recent advances in high-throughput sequencing techniques have made it possible to better understand these complex microbial communities and their effects on hosts. Animal and clinical studies have provided considerable evidence to show that the microbiota plays an important role in chronic kidney disease, acute kidney injury, nephrolithiasis, and kidney transplantation by altering the functions of the intestinal barrier, regulating local and systemic inflammation, controlling production of metabolic components, and affecting immune responses. Although the exact mechanism underlying the microbial shift and its impact on disease progression remains uncertain, the kidney-gut interaction clearly plays a significant role in onset and progression of kidney disease and, therefore, holds promise as a therapeutic target. Here, we review recent literature pertaining to the bidirectional relationship between microbes and humans in various kidney diseases and discuss the future direction of microbial research in nephrology.

Dysbiosis-Related Advanced Glycation Endproducts and Trimethylamine N-Oxide in Chronic Kidney Disease

Chronic kidney disease (CKD) is a public health concern that affects approximately 10% of the global population. CKD is associated with poor outcomes due to high frequencies of comorbidities such as heart failure and cardiovascular disease. Uremic toxins are compounds that are usually filtered and excreted by the kidneys. With the decline of renal function, uremic toxins are accumulated in the systemic circulation and tissues, which hastens the progression of CKD and concomitant comorbidities. Gut microbial dysbiosis, defined as an imbalance of the gut microbial community, is one of the comorbidities of CKD. Meanwhile, gut dysbiosis plays a pathological role in accelerating CKD progression through the production of further uremic toxins in the gastrointestinal tracts. Therefore, the gut-kidney axis has been attracting attention in recent years as a potential therapeutic target for stopping CKD. Trimethylamine N-oxide (TMAO) generated by gut microbiota is linked to the progression of cardiovascular disease and CKD. Also, advanced glycation endproducts (AGEs) not only promote CKD but also cause gut dysbiosis with disruption of the intestinal barrier. This review summarizes the underlying mechanism for how gut microbial dysbiosis promotes kidney injury and highlights the wide-ranging interventions to counter dysbiosis for CKD patients from the view of uremic toxins such as TMAO and AGEs.

The Impact of CKD on Uremic Toxins and Gut Microbiota

Numerous studies have indicated that the progression of chronic kidney disease (CKD) to end-stage renal disease (ESRD) is strictly associated with the accumulation of toxic metabolites in blood and other metabolic compartments. This accumulation was suggested to be related to enhanced generation of toxins from the dysbiotic microbiome accompanied by their reduced elimination by impaired kidneys. Intestinal microbiota play a key role in the accumulation of uremic toxins due to the fact that numerous uremic solutes are generated in the process of protein fermentation by colonic microbiota. Some disease states, including CKD, are associated with the presence of dysbiosis, which can be defined as an "imbalanced intestinal microbial community with quantitative and qualitative changes in the composition and metabolic activities of the gut microbiota". The results of studies have confirmed the altered composition and functions of gut microbial community in chronic kidney disease. In the course of CKD protein-bound uremic toxins, including indoxyl sulfate, p-cresyl glucuronide, p-cresyl sulfate and indole-3-acetic acid are progressively accumulated. The presence of chronic kidney disease may be accompanied by the development of intestinal inflammation and epithelial barrier impairment leading to hastened systemic translocation of bacterial-derived uremic toxins and consequent oxidative stress injury to the kidney, cardiovascular and endocrine systems. These findings offer new therapeutic possibilities for the management of uremia, inflammation and kidney disease progression and the prevention of adverse outcomes in CKD patients. It seems that dietary interventions comprising prebiotics, probiotics, and synbiotics could pose a promising strategy in the management of uremic toxins in CKD.

The Microbiome and p-Inulin in Hemodialysis: A Feasibility Study

Background

The intestinal microbiome is an appealing target for interventions in ESKD because of its likely contribution to uremic toxicity. Before conducting clinical trials of microbiome-altering treatments, it is necessary to understand the within-person and between-person variability in the composition and function of the gut microbiome in patients with ESKD.

Methods

We conducted a multicenter, nonrandomized, crossover feasibility study of patients on maintenance hemodialysis consisting of three phases: pretreatment (8 weeks); treatment, during which the prebiotic, p-inulin, was administered at a dosage of 8 g twice daily (12 weeks); and post-treatment (8 weeks). Stool samples were collected 1-2 times per week and blood was collected weekly for 28 weeks. The gut microbiome was characterized using 16S ribosomal-RNA sequencing and metabolomic profiling.

Results

A total of 11 of the 13 participants completed the 28-week study. Interparticipant variability was greater than intraparticipant variability for microbiome composition (P<0.001 by UniFrac distances) and metabolomic composition (P<0.001 by Euclidean distances). p-Inulin was well tolerated by 12 of 13 participants. Adherence to the frequent sample collection and self-aliquoting of stool samples were both 96%. A change in the microbiome composition from pretreatment to post-treatment was evident by the overall shifts in weighted UniFrac distances (P=0.004) and a progressive decrease in prevalence of high intraclass correlations, indicating an increase in intraparticipant microbiome diversity during and after p-inulin treatment. An effect of p-inulin on the metabolomic profile was not evident.

Conclusions

The intraparticipant stability of the gut microbiome under no-treatment conditions, the tolerability of p-inulin, the signals of increased diversity of the microbiome with p-inulin treatment, and the willingness of participants to provide stool samples all support the feasibility of a larger trial to investigate interventions targeting the gut microbiome in patients with ESKD. Whether or not p-inulin has sufficient efficacy as an intervention requires evaluation in larger studies.

Clinical Trial registry name and registration number

Gut Microbiome and p-Inulin in Hemodialysis, NCT02572882.

Clostridioides difficile Infection in Chronic Kidney Disease-An Overview for Clinicians

Increased incidence of Clostridioides difficile infection (CDI), occurrence of severe and complicated CDI, and more frequent occurrence of drug-resistant, recurrent or non-hospital CDI has become a worldwide clinical problem. CDI is more common in patients with chronic kidney disease (CKD) than in the general population. CDI seems to be associated with frequent hospitalization, frequently used antibiotic therapy, dysbiosis, and abnormalities of the immune system observed in CKD patients. Dysbiosis is a common disorder found in CKD patients. It may be related to insufficient fiber content in the diet, reduced amount of consumed fluids and often reduced physical activity, constipation, impaired gastrointestinal motility, multidrug pharmacotherapy, and uremic milieu in CKD stage 5. In patients with CKD the clinical manifestations of CDI are similar to the general population; however, more frequent recurrence of CDI and higher prevalence of severe CDI are reported. Moreover, the increase in CDI related mortality is observed more in CKD patients than in the general population. The aim of this review paper is to summarize the current knowledge concerning the epidemiology, pathogenesis, clinical picture, and prevention and treatment in CKD patients.

Microbiome modulation as a novel therapeutic approach in chronic kidney disease

PURPOSE OF REVIEW

Gut dysbiosis has been implicated in the pathogenesis of chronic kidney disease (CKD). Interventions aimed at restoring gut microbiota have emerged as a potential therapeutic option in CKD. This review summarizes the current evidence on gut microbiota-targeted strategies in patients with CKD.

RECENT FINDINGS

A growing number of studies have shown that plant-based diets, low-protein diets, prebiotic, probiotic, and synbiotic supplementation, and constipation treatment may lead to favorable alterations in the gut microbiota. Current evidence suggests that the implementation of both plant-based and low-protein diets has potential benefits for the primary prevention of CKD, and for slowing CKD progression, with minimal risk of hyperkalemia and/or cachexia. The use of prebiotics, probiotics, and synbiotics and laxatives may have beneficial effects on uremic toxin generation, but their evidence is limited for the prevention and treatment of CKD. Recent advances in diagnostic technologies (e.g., high-throughput sequencing and nanotechnology) could enhance rapid diagnosis, monitoring, and design of effective therapeutic strategies for mitigating gut dysbiosis in CKD.

SUMMARY

Plant-based and low-protein diets, prebiotic, probiotic, and synbiotic supplementation, and constipation treatment represent novel gut microbiota-targeted strategies in the conservative management of CKD, which could improve clinical outcomes in CKD.

Chronic Kidney Disease, Gut Dysbiosis, and Constipation: A Burdensome Triplet

Gut dysbiosis has been implicated in the progression of chronic kidney disease (CKD). Alterations in the gut environment induced by uremic toxins, the dietary restriction of fiber-rich foods, and multiple drugs may be involved in CKD-related gut dysbiosis. CKD-related gut dysbiosis is considered to be characterized by the expansion of bacterial species producing precursors of harmful uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, and the contraction of species generating beneficial short-chain fatty acids, such as butyrate. Gut-derived uremic toxins cause oxidative stress and pro-inflammatory responses, whereas butyrate exerts anti-inflammatory effects and contributes to gut epithelial integrity. Gut dysbiosis is associated with the disruption of the gut epithelial barrier, which leads to the translocation of endotoxins. Research on CKD-related gut dysbiosis has mainly focused on chronic inflammation and consequent cardiovascular and renal damage. The pathogenic relationship between CKD-related gut dysbiosis and constipation has not yet been investigated in detail. Constipation is highly prevalent in CKD and affects the quality of life of these patients. Under the pathophysiological state of gut dysbiosis, altered bacterial fermentation products may play a prominent role in intestinal dysmotility. In this review, we outline the factors contributing to constipation, such as the gut microbiota and bacterial fermentation; introduce recent findings on the pathogenic link between CKD-related gut dysbiosis and constipation; and discuss potential interventions. This pathogenic link needs to be elucidated in more detail and may contribute to the development of novel treatment options not only for constipation, but also cardiovascular disease in CKD.

Laxative use in patients with advanced chronic kidney disease transitioning to dialysis

BACKGROUND

Constipation is highly prevalent in patients with chronic kidney disease (CKD), particularly among those with end-stage renal disease (ESRD), partly due to their dietary restrictions, comorbidities and medications. Laxatives are typically used for constipation management; however, little is known about laxative use and its associated factors in patients with advanced CKD transitioning to ESRD.

METHODS

In a retrospective cohort of 102 477 US veterans transitioning to dialysis between October 2007 and March 2015, we examined the proportion of patients who filled a prescription for any type of laxative within each 6-month period over 36 months pre- and post-transition to ESRD. Factors associated with laxative use during the last 1-year pre-ESRD period were identified by multivariable logistic regression.

RESULTS

The proportion of patients prescribed laxatives increased as patients progressed to ESRD, peaking at 37.1% in the 6 months immediately following ESRD transition, then remaining fairly stable throughout the post-ESRD transition period. Among laxative users, stool softeners were the most commonly prescribed (∼30%), followed by hyperosmotics (∼20%), stimulants (∼10%), bulk formers (∼3%), chloride channel activator (<1%) and several combinations of these. The use of anticoagulants, oral iron supplements, non-opioid analgesics, antihistamines and opioid analgesics were among the factors independently associated with pre-ESRD laxative use.

CONCLUSION

The use of laxatives increased considerably as patients neared transition to ESRD, likely mirroring the increasing burden of drug-induced constipation during the ESRD transition period. Findings may provide novel insight into better management strategies to alleviate constipation symptoms and reduce medication requirements in patients with advanced CKD.

Association between pill burden and interdialytic weight gain in patients with hemodialysis: A multi-center cross-sectional study

High daily pill burden affects quality of life and mortality. High interdialytic weight gain (IDWG) is associated with increased mortality. We examined the association between pill burden and IDWG in hemodialysis patients. This cross-sectional study was conducted in six dialysis centers in Japan in June 2017. The exposure was the number of daily tablets, and outcome was defined as 1 day of relative IDWG divided by post-dialysis weight from the previous session. Among 188 outpatients (mean age, 68.7 [SD, 10.3] years; men, 67.0%; median dialysis vintage, 76.0 [interquartile range, 36.5, 131.5] months), the mean number of daily tablets was 19.7 ± 9.9, and mean relative weight gain was 3.5 ± 1.2%. Multiple linear regression analysis showed a regression coefficient of 0.021 (95% confidence interval: 0.004-0.039), indicating that one additional tablet prescription increased the IDWG by 0.021%. In hemodialysis patients, the daily pill burden was a significant, independent risk for increased relative IDWG.

Laxative Use and Change in Estimated Glomerular Filtration Rate in Patients With Advanced Chronic Kidney Disease

OBJECTIVES

Constipation is highly prevalent in advanced chronic kidney disease (CKD), due in part to dietary (e.g., fiber) restrictions, and is often managed by laxatives; however, the effect of laxative use on kidney function in advanced CKD remains unclear. We aimed to examine the association of laxative use with longitudinal change in estimated glomerular filtration rate (eGFR) in patients with advanced CKD.

DESIGN AND METHODS

In a retrospective cohort of 43,622 US veterans transitioning to end-stage renal disease (ESRD) from 2007 to 2015, we estimated changes in eGFR (slope) by linear mixed-effects models using ≥2 available outpatient eGFR measurements during the 2-year period before transition to ESRD. The association of laxative use with change in eGFR was examined by testing the interaction of time-varying laxative use with time for eGFR slope in the mixed-effects models with adjustment for fixed and time-varying confounders.

RESULTS

Laxatives were prescribed in 49.8% of patients during the last 2-year pre-ESRD period. In the crude model, time-varying laxative use was modestly associated with more progressive eGFR decline compared with non-use of laxatives (median [interquartile interval] -7.1 [-11.9, -4.3] vs. -6.8 [-11.6, -4.0] mL/min/1.73 m²/year, P < .001). After multivariable adjustment, a faster eGFR decline associated with laxative use (vs. non-use of laxatives) remained statistically significant, although the between-group difference in eGFR slope was minimal (median [interquartile interval] -8.8 [-12.9, -5.9] vs. -8.6 [-12.6, -5.6] mL/min/1.73 m²/year, P < .001). The significant association was no longer evident across different types of laxatives (i.e., stool softeners, stimulants, or hyperosmotics).

CONCLUSIONS

There was a clinically negligible association of laxative use with change in eGFR during the last 2-year pre-ESRD period, suggesting the renal safety profile of laxatives in advanced CKD patients.

The Efficacy of Lactobacillus-Containing Probiotic Supplementation in Hemodialysis Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVES

This study was performed to determine the effects of probiotic supplementation on cholesterol-triglyceride ratio, an indirect marker of insulin resistance, protein-bound uremic toxins, biomarkers of inflammation, and microbial translocation in end-stage renal disease patients on hemodialysis.

METHODS

Fifty-six patients aged 39-75 years were assigned into two groups to receive either probiotic sachets (n = 28) or a placebo (n = 28) in a randomized double-blinded placebo-controlled clinical trial. The patients in the probiotic group received twice daily sachets that contained a mixture of three viable and freeze-dried strains: Lactococcus lactis subsp. Lactis LL358, Lactobaccillus salivarius LS159, and Lactobaccillus pentosus LPE588 at high dose (100 billion; 1 × 10¹¹ cfu/day) for 6 months.

RESULTS

A total of 50 patients were available for final analysis. Probiotic supplementation did not have a significant influence on cholesterol-triglyceride ratio. Probiotic supplementation for 6 months caused a significant decrease in serum levels of indoxyl sulfate. Compared with the placebo, probiotic supplementation did not result in significant changes in hemoglobin levels, blood urea nitrogen, blood glucose, serum p-cresyl sulfate, inflammatory, and microbial translocation markers. No clinically significant changes in body composition were observed between the two groups during the study period. The probiotic supplementation was well tolerated by all subjects with minimal adverse effects during the 6-month-long study.

CONCLUSION

Our results suggest that high-dose multistrain lactobaccillus probiotic supplementation over 6 months as a monotherapy did not significantly decrease markers of insulin resistance, cholesterol-triglyceride ratio, and most of the studied markers, with the exception of levels of indoxyl sulfate in patients on HD.

The Effects of Nutrition on the Gastrointestinal Microbiome of Cats and Dogs: Impact on Health and Disease

The gastrointestinal (GI) microbiome of cats and dogs is increasingly recognized as a metabolically active organ inextricably linked to pet health. Food serves as a substrate for the GI microbiome of cats and dogs and plays a significant role in defining the composition and metabolism of the GI microbiome. The microbiome, in turn, facilitates the host's nutrient digestion and the production of postbiotics, which are bacterially derived compounds that can influence pet health. Consequently, pet owners have a role in shaping the microbiome of cats and dogs through the food they choose to provide. Yet, a clear understanding of the impact these food choices have on the microbiome, and thus on the overall health of the pet, is lacking. Pet foods are formulated to contain the typical nutritional building blocks of carbohydrates, proteins, and fats, but increasingly include microbiome-targeted ingredients, such as prebiotics and probiotics. Each of these categories, as well as their relative proportions in food, can affect the composition and/or function of the microbiome. Accumulating evidence suggests that dietary components may impact not only GI disease, but also allergies, oral health, weight management, diabetes, and kidney disease through changes in the GI microbiome. Until recently, the focus of microbiome research was to characterize alterations in microbiome composition in disease states, while less research effort has been devoted to understanding how changes in nutrition can influence pet health by modifying the microbiome function. This review summarizes the impact of pet food nutritional components on the composition and function of the microbiome and examines evidence for the role of nutrition in impacting host health through the microbiome in a variety of disease states. Understanding how nutrition can modulate GI microbiome composition and function may reveal new avenues for enhancing the health and resilience of cats and dogs.

Gut-Derived Metabolites and Their Role in Immune Dysfunction in Chronic Kidney Disease

Several of the uremic toxins, which are difficult to remove by dialysis, originate from the gut bacterial metabolism. This opens opportunities for novel targets trying to decrease circulating levels of these toxins and their pathophysiological effects. The current review focuses on immunomodulatory effects of these toxins both at their side of origin and in the circulation. In the gut end products of the bacterial metabolism such as p-cresol, trimethylamine and H₂S affect the intestinal barrier structure and function while in the circulation the related uremic toxins stimulate cells of the immune system. Both conditions contribute to the pro-inflammatory status of patients with chronic kidney disease (CKD). Generation and/or absorption of these toxin precursors could be targeted to decrease plasma levels of their respective uremic toxins and to reduce micro-inflammation in CKD.

Ameliorating Chronic Kidney Disease Using a Whole Food Plant-Based Diet

Novel approaches to ameliorating chronic kidney disease (CKD) are warranted as most patients are undiagnosed until they begin displaying symptoms of kidney failure. There is increasing evidence that a whole food plant-based (WFPB) diet may offer benefits that slow the progression of CKD, decrease the incidence cardiovascular disease, decrease rates of diabetes and obesity, and reduce inflammation and cholesterol, which in turn can delay kidney failure and the initiation of dialysis. While animal-based protein ingestion promotes an acidic environment, inflammation and renal hyperfiltration, study authors report plant-based protein can be alkaline-producing and anti-inflammatory and can contain renoprotective properties. Although there may be benefits to adopting a WFPB diet, macronutrient and micronutrient content should be carefully considered and adjusted to avoid malnutrition in CKD patients. Further research needs to be done in order to establish the biological plausibility and feasibility of a WFPB in individuals with diagnosed CKD.

Association of subjective global assessment of nutritional status with gut microbiota in hemodialysis patients: a case-control study

BACKGROUND

Protein-energy wasting (PEW) is prevalent and associated with adverse outcomes in patients with chronic kidney disease (CKD). However, the pathogenesis of PEW in CKD patients has not been fully identified. The gut microbiota has been implicated in the regulation of host metabolism and energy balance. Therefore, we aimed to explore the association between nutritional status and the composition of the gut microbiota in hemodialysis patients.

METHODS

Gut microbial diversity and taxonomy were examined in 88 hemodialysis patients with PEW (n = 22) and normal nutritional status (n = 66) who were matched 1:3 for age and sex. Nutritional status was assessed by using the 7-point subjective global assessment (SGA) score (1-3 = severe PEW; 4-5 = moderate PEW and 6-7 = normal nutrition). The gut microbiota was assessed by 16S ribosomal RNA gene sequencing.

RESULTS

Patients with normal nutritional status had a significantly higher body mass index and physical activity and serum albumin levels, but significantly lower levels of inflammatory cytokines than patients with PEW. The most striking finding was that the α-diversity of the gut microbiota was significantly lower in patients with PEW. In a multivariate analysis, the SGA score was independently and positively associated with α-diversity (P = 0.049). Patients with or without PEW were different with respect to the principal coordinate analysis of β-diversity. Notably, the relative abundance of Faecalibacterium prausnitzii, a butyrate-producing bacteria, was markedly reduced in patients with PEW.

CONCLUSION

In hemodialysis patients, PEW assessed with the SGA was associated with gut dysbiosis.

A Risk Analysis of Continuous Ambulatory Peritoneal Dialysis-Related Peritonitis

Objective

We studied the clinical characteristics that influence the risk of dialysis-related peritonitis complication in incident Chinese patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

Methods

A single center, retrospective, observational cohort study was carried out to examine the risk factors of developing a first episode of dialysis-related peritonitis.

Results

Between 1995 and 2004, 246 incident CAPD patients were recruited for analysis. During the study period of 897.1 patient-years, 85 initial episodes of peritonitis were recorded. The median peritonitis-free time for diabetic subjects was significantly worse than for nondiabetic subjects (49.0 ± 10.5 vs 82.3 ± 12.6 months, p = 0.0019). The difference was due mainly to a higher likelihood of developing peritonitis with gram-negative organisms in patients with diabetes mellitus ( p = 0.038). Low serum albumin concentration was also associated with worse peritonitis-free survival. There was a nonsignificant trend toward an increased risk for peritonitis in the group of patients with cerebrovascular disease. According to multivariate Cox proportional hazards model for the analysis of time to first peritonitis episode, the two independent risk factors were presence of diabetes mellitus and initial serum albumin concentration. In particular, diabetes mellitus was associated with a hazard ratio of 1.50 and a 95% confidence interval of 1.05 – 2.40 ( p = 0.030) to develop an initial peritonitis. Lower serum albumin level at the start of CAPD was a significant predictor of peritonitis, with hazard ratio of 1.67 for every decrease of 10 g/L, and 95% confidence interval 1.08 – 2.60 ( p = 0.021).

Conclusions

Our results confirm the susceptibility of diabetic CAPD and hypoalbuminemic patients to peritonitis, and highlight the role of further studies in reducing this complication.

Particular aspects of gastroenterological disorders in chronic kidney disease and end-stage renal disease patients: a clinically focused review

Besides renal disease, gastrointestinal (GI) disorders are frequently reported in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Related gastrointestinal symptoms tend to increase as the renal disease progresses. Also, in patients with ESRD, the modality of dialysis is related to particular forms of GI disorders.The kidney can interact with the digestive organs through functional endogenous systems such as the 'kidney-colon axis' and the 'kidney-liver axis'. Digestive diseases are one of the visible manifestations of the disturbance between hemostatic, hemodynamic and immunological balance in such patients.No clear management guidelines currently exist for many of the gastrointestinal problems that accompany renal failure. This review aims to describe the particular aspects of GI diseases present in CKD/ESRD. We focus our discussion in the specificities of epidemiology, diagnosis, and prognosis of such disorders between the different segments of the digestive system.

Constipation in CKD

Constipation is one of the most common gastrointestinal disorders among patients with chronic kidney disease (CKD) partly because of their sedentary lifestyle, low fiber and fluid intake, concomitant medications (e.g., phosphate binders), and multiple comorbidities (e.g., diabetes). Although constipation is usually perceived as a benign, often self-limited condition, recent evidence has challenged this most common perception of constipation. The chronic symptoms of constipation negatively affect patients' quality of life and impose a considerable social and economic burden. Furthermore, recent epidemiological studies have revealed that constipation is independently associated with adverse clinical outcomes, such as end-stage renal disease (ESRD), cardiovascular (CV) disease, and mortality, potentially mediated by the alteration of gut microbiota and the increased production of fecal metabolites. Given the importance of the gut in the disposal of uremic toxins and in acid-base and mineral homeostasis with declining kidney function, the presence of constipation in CKD may limit or even preclude these ancillary gastrointestinal roles, potentially contributing to excess morbidity and mortality. With the advent of new drug classes for constipation, some of which showing unique renoprotective properties, the adequate management of constipation in CKD may provide additional therapeutic benefits beyond its conventional defecation control. Nevertheless, the problem of constipation in CKD has long been underrecognized and its management strategies have scarcely been documented. This review outlines the current understanding of the diagnosis, prevalence, etiology, outcome, and treatment of constipation in CKD, and aims to discuss its novel clinical and therapeutic implications.

Constipation in chronic kidney disease: it is time to reconsider

Constipation is highly prevalent in patients with chronic kidney disease (CKD) and is primarily characterized by decreased intestinal motility. This chronic disorder affects the quality of life of patients. However, nephrologist and dialysis clinicians have long had a disproportionately limited understanding of constipation. Accumulating evidence has revealed a relationship between constipation and cardiovascular disease and CKD. The pathogenesis of constipation in CKD patients is multifactorial: decreased physical activity, comorbidities affecting bowel movement, such as diabetes mellitus, cerebrovascular disease, and hyperparathyroidism, a restricted dietary intake of plant-based fiber-rich foods, and multiple medications, including phosphate binders and potassium-binding resins, have all been implicated. CKD is associated with alterations in the composition and function of the gut microbiota, so-called gut dysbiosis. Recent studies showed that CKD-related gut dysbiosis decreased intestinal motility via intestinal inflammation or the increased generation of gut-derived uremic toxins, such as indoxyl sulfate and p-cresyl sulfate. Furthermore, the gastrointestinal secretion of mucin was found to be decreased in CKD animal models, which may delay colonic transit by diminished lubrication in the alimentary tract. Thus, CKD-related gut dysbiosis may play a role in constipation, but limited information is currently available. Since constipation is often intractable, particularly in CKD patients, every available means needs to be employed in its treatment. The effects of probiotics, prebiotics, and synbiotics on the composition of the gut microbiota and gut-derived uremic toxins have been increasingly reported. However, their effects on stool consistency or frequency in CKD patients remain unclear. Some laxatives may be beneficial for improving not only bowel habits but also gut dysbiosis. Further studies are required to elucidate the CKD-specific pathogenesis of constipation and develop novel effective treatment options.

The gut–kidney–heart axis in chronic kidney disease

The recent explosion of scientific interest in the gut microbiota has dramatically advanced our understanding of the complex pathophysiological interactions between the gut and multiple organs in health and disease. Emerging evidence has revealed that the gut microbiota is significantly altered in patients with chronic kidney disease (CKD), along with impaired intestinal barrier function. These alterations allow translocation of various gut-derived products into the systemic circulation, contributing to the development and progression of CKD and cardiovascular disease (CVD), partly mediated by chronic inflammation. Among potentially toxic gut-derived products identifiable in the systemic circulation, bacterial endotoxin and gut metabolites (e.g., p-cresyl sulfate and trimethylamine-N-oxide) have been extensively studied for their immunostimulatory and atherogenic properties. Recent studies have also suggested similar biological properties of bacterial DNA fragments circulating in the blood of patients with CKD, even in the absence of overt infections. Despite the accumulating evidence of the gut microbiota in CKD and its therapeutic potential for CVD, the precise mechanisms for multidirectional interactions between the gut, kidney, and heart remain poorly understood. This review aims to provide recent evidence on the associations between the gut microbiota, CKD, and CVD, and summarize current understanding of the potential pathophysiological mechanisms underlying the “gut–kidney–heart” axis in CKD.

Gastrointestinal Microbiota in Patients with Chronic Kidney Disease: A Systematic Review

Emerging evidence suggests that gastrointestinal (GI) microbiota dysbiosis is associated with chronic kidney disease (CKD) and metabolite concentrations. The purpose of this systematic review was to evaluate and contextualize the research characterizing GI microbiota in patients with CKD. We searched for full-text, peer-reviewed, English studies in PubMed, Cumulative Index to Nursing and Allied Health Literature, Web of Science, and Google Scholar using a combination of MeSH terms and keywords. Eleven of the 20 studies examined GI microbiota in patients with CKD, and 9 studies focused on the effect of interventions on GI microbiota or metabolites. Available data characterizing GI microbiota in patients with CKD suggest a decline in saccharolytic bacteria and an increase in fermenters of nitrogen-containing compounds, serving as a source for circulating uremic toxins. However, studies examined limited sets of predetermined microbes, which do not reflect the entire GI microbial community and its influence on host physiology. We recommend further studies examining the entire microbial community and the potential role in regulating host physiology in CKD.

Constipation in Peritoneal Dialysis Patients

Constipation in peritoneal dialysis (PD) is an infrequent but potentially serious condition affecting the mechanical properties of dialysis techniques and predisposing to bacterial intestinal translocation and eventual enteric peritonitis. Despite the importance of the problem, published literature is scarce, consisting mostly of uncontrolled single-center trials. This inconsistency may be attributed to the large number of clinical, radiological, and endoscopic tools that have been used in the studies with a lack of generally accepted core primary outcomes.

The current narrative review discusses the pathophysiological associations between chronic kidney disease, PD, and constipation with related complication.

Clinical features of hypermagnesemia in patients with functional constipation taking daily magnesium oxide

Although magnesium oxide is widely used as a laxative, alterations in serum magnesium concentrations among patients taking daily magnesium oxide have not been clarified. The present retrospective, cross-sectional study investigated the risk factors for hypermagnesemia in patients taking daily oral magnesium oxide. Of 2,176 patients administered daily magnesium oxide, 193 (8.9%) underwent assays of serum magnesium concentrations and were evaluated. High serum magnesium concentration and hypermagnesemia were defined as serum magnesium concentrations ≥2.5 mg/dl and ≥3.0 mg/dl, respectively. Of the 193 patients taking daily magnesium oxide, 32 (16.6%) had high serum magnesium concentration and 10 (5.2%) had hypermagnesemia. Factors associated with hypermagnesemia included chronic kidney disease (CKD) grade 4 (p = 0.014) and magnesium oxide dosage (p = 0.009). Factors associated with high serum magnesium concentration included magnesium oxide dosage >1,000 mg/day (p = 0.004), CKD grades 4 (p = 0.000) and concomitant use of stimulant laxatives (p = 0.035). Age, however, was not associated with hypermagnesemia or high serum magnesium concentration. In conclusion, renal function and magnesium oxide dosage, but not age, were associated with hypermagnesemia and high serum magnesium concentration in patients with functional constipation taking daily magnesium oxide.