Single-cell RNA sequencing reveals transdifferentiation of parathyroid chief cells into oxyphil cells in patients with uremic secondary hyperparathyroidism

The parathyroid gland is one of the main organs that regulate calcium and phosphorus metabolism. It is mainly composed of chief cells and oxyphil cells. Oxyphil cell counts are low in the parathyroid glands of healthy adults but are dramatically increased in patients with uremia and secondary hyperparathyroidism (SHPT). Increased oxyphil cell counts are related to drug treatment resistance, but the origin of oxyphil cells and the mechanism of proliferation remain unknown. Herein, three types of parathyroid nodules (chief cell nodules, oxyphil cell nodules and mixed nodules, respectively) excised from parathyroid glands of uremic SHPT patients were used for single-cell RNA sequencing (scRNA-seq), other molecular biology studies, and transplantation into nude mice. Through scRNA-seq of parathyroid mixed nodules from three patients with uremic SHPT, we established the first transcriptomic map of the human parathyroid and found a chief-to-oxyphil cell transdifferentiation characterized by gradual mitochondrial enrichment associated with the uremic milieu. Notably, the mitochondrial enrichment and cellular proliferation of chief cell and oxyphil cell nodules decreased significantly after leaving the uremic milieu via transplantation into nude mice. Remarkably, the phenotype of oxyphil cell nodules improved significantly in the nude mice as characterized by decreased mitochondrial content and the proportion of oxyphil cells to chief cells. Thus, our study provides a comprehensive single-cell transcriptome atlas of the human parathyroid and elucidates the origin of parathyroid oxyphil cells and their underlying transdifferentiating mechanism. These findings enhance our understanding of parathyroid disease and may open new treatment perspectives for patients with chronic kidney disease.

Effects of AST-120 on mortality in patients with chronic kidney disease modeled by artificial intelligence or traditional statistical analysis

Chronic kidney disease (CKD) imposes a substantial burden, and patient prognosis remains grim. The impact of AST-120 (AST-120) on the survival of CKD patients lacks a consensus. This study aims to investigate the effects of AST-120 usage on the survival of CKD patients and explore the utility of artificial intelligence models for decision-making. We conducted a retrospective analysis of CKD patients receiving care in the pre-end-stage renal disease (ESRD) program at Taichung Veterans General Hospital from 2000 to 2019. We employed Cox regression models to evaluate the relationship between AST-120 use and patient survival, both before and after propensity score matching. Subsequently, we employed Deep Neural Network (DNN) and Extreme Gradient Boosting (XGBoost) models to assess their performance in predicting AST-120's impact on patient survival. Among the 2584 patients in our cohort, 2199 did not use AST-120, while 385 patients received AST-120. AST-120 users exhibited significantly lower mortality rates compared to non-AST-120 users (13.51% vs. 37.88%, p < 0.0001) and a reduced prevalence of ESRD (44.16% vs. 53.17%, p = 0.0005). Propensity score matching at 1:1 and 1:2 revealed no significant differences, except for dialysis and all-cause mortality, where AST-120 users exhibited significantly lower all-cause mortality (p < 0.0001), with a hazard ratio (HR) of 0.395 (95% CI = 0.295-0.522). This difference remained statistically significant even after propensity matching. In terms of model performance, the XGBoost model demonstrated the highest accuracy (0.72), specificity (0.90), and positive predictive value (0.48), while the logistic regression model showed the highest sensitivity (0.63) and negative predictive value (0.84). The area under the curve (AUC) values for logistic regression, DNN, and XGBoost were 0.73, 0.73, and 0.69, respectively, indicating similar predictive capabilities for mortality. In this cohort of CKD patients, the use of AST-120 is significantly associated with reduced mortality. However, the performance of artificial intelligence models in predicting the impact of AST-120 is not superior to statistical analysis using the current architecture and algorithm.

Uraemic solutes as therapeutic targets in CKD-associated cardiovascular disease

Chronic kidney disease (CKD) is characterized by the retention of a myriad of solutes termed uraemic (or uremic) toxins, which inflict damage to several organs, including the cardiovascular system. Uraemic toxins can induce hallmarks of cardiovascular disease (CVD), such as atherothrombosis, heart failure, dysrhythmias, vessel calcification and dysregulated angiogenesis. CVD is an important driver of mortality in patients with CKD; however, reliance on conventional approaches to managing CVD risk is insufficient in these patients, underscoring a need to target risk factors that are specific to CKD. Mounting evidence suggests that targeting uraemic toxins and/or pathways induced by uraemic toxins, including tryptophan metabolites and trimethylamine N-oxide (TMAO), can lower the risk of CVD in patients with CKD. Although tangible therapies resulting from our growing knowledge of uraemic toxicity are yet to materialize, a number of pharmacological and non-pharmacological approaches have the potential to abrogate the effects of uraemic toxins, for example, by decreasing the production of uraemic toxins, by modifying metabolic pathways induced by uraemic toxins such as those controlled by aryl hydrocarbon receptor signalling and by augmenting the clearance of uraemic toxins.

Phosphate clearance in peritoneal dialysis

In renal failure, hyperphosphatemia is common and correlates with increased mortality making phosphate removal a key priority for dialysis therapy. We investigated phosphate clearance, removal and serum level, and factors associated with phosphate control in patients undergoing continuous ambulatory (CAPD), continuous cyclic (CCPD) and automated (APD) peritoneal dialysis (PD). In 154 prevalent PD patients (mean age 53.2 ± 17.6 year, 59% men, 47% anuric), 196 daily collections of urine and 368 collections of dialysate were evaluated in terms of renal, peritoneal and total (renal plus peritoneal) phosphorus removal (g/week), phosphate and creatinine clearances (L/week) and urea KT/V. Dialytic removal of phosphorus was lower in APD (1.34 ± 0.62 g/week) than in CAPD (1.89 ± 0.73 g/week) and CCPD (1.91 ± 0.63 g/week) patients; concomitantly, serum phosphorus was higher in APD than in CAPD (5.55 ± 1.61 vs. 4.84 ± 1.23 mg/dL; p < 0.05). Peritoneal and total phosphate clearances correlated with peritoneal (rho = 0.93) and total (rho = 0.85) creatinine clearances (p < 0.001) but less with peritoneal and total urea KT/V (rho = 0.60 and rho = 0.65, respectively, p < 0.001). Phosphate removal, clearance and serum levels differed between PD modalities. CAPD was associated with higher peritoneal removal and lower serum level of phosphate than APD.

Flow Cytometry of CD14, VDR, Cyp27 and Cyp24 and TLR4 in U937 Cells

Chronic Kidney Disease (CKD) patients present a micro inflammation state due to failure renal function. The calcitriol has been described as an anti-inflammatory factor that might modulates the inflammatory response in CKD patients. However, these patients have deficiency of Calcitriol due to failure renal function. But, synthesis of this vitamin has been reported in extra renal production, as in monocytes. In this context, it has been reported that the supplementation with 25 vitamin D (calcidiol or inactive form of vitamin D) induces monocytes to downregulate inflammation, due to the intracellular 1α-hidroxilase that converts calcidiol to calcitriol in these cells. Besides some reports used RT-qPCR, Western Blot or immunofluorescence techniques to investigate the expression of inflammatory and vitamin D machinery biomarkers in several disease, in the present study we used flow cytometry technique to evaluate the effect of 25 vitamin D on CD14, Toll-like receptor 4 (TLR4), vitamin D receptor (VDR), 1-α hydroxylase (CYP27), 24 hydroxylase (CYP24) in monocytes lineage (U937). The U937 culture was incubated with healthy or CKD serum and treatment with/without 25-vitamin D (50 ng/ml for 24 h) to evaluate CD14, TRL4, VDR, CYP27 and CYP24 expression. This protocol showed the advantage to investigate the effect of treatment with 25 vitamin D on the intracellular and cell membrane biomarkers expression quickly and simultaneously. In addition, this technique is not laborious, but easy to perform and to interpret compared to RT-qPCR, western blot or immunofluorescence.

25-vitamin D reduces inflammation in uremic environment

Chronic kidney disease (CKD) is characterized by loss of renal function and a consequent increase of serum uremic toxins, which contribute to inflammation status. Deficiency of 25-vitamin D, often found in patients with CKD, has been included as an inflammatory factor since it might modulate the immune system. The aim of this study was to investigate the role of 25-vitamin D on inflammatory pathways in healthy and uremic environment. Toll-like receptor 4 (TLR4), oxidative stress (ROS), vitamin D receptor (VDR), 1-α hydroxylase (CYP27), 24 hydroxylase, cathelicidin, and MCP-1 were evaluated in monocytes exposed to a uremic serum pool compared with healthy pool. The human monocytes lineage (U937) was incubated with or without 25-vitamin D (50 ng/ml for 24 hours). TRL4, VDR, CYP27, CYP24, and ROS were evaluated by flow cytometry. We used ELISA to measure IL-6, TNF-α, IL-10, cathelicidin, and MCP-1 in the cell culture supernatant. We observed a higher expression of TRL-4, IL-6, TNF-α, IL-10, cathelicidin and MCP-1 in monocytes incubated with uremic serum when compared with serum from healthy individuals. Supplementation of 25-vitamin D was able to reduce the expression of TRL4, cathelicidin, and MCP-1 in the uremic environment. There was no difference in the expression of VDR, CYP27 and CYP24 intracellular enzymes. This in vitro study showed that the uremic pool activates inflammatory response in monocytes, which was reversed by 25-vitamin D supplementation; this finding suggests that 25-vitamin D has an anti-inflammatory role in the uremic environment.

The effects of intradialytic exercise on hemodialysis adequacy: A systematic review

Dialysis adequacy is an independent predictor of high mortality rates in hemodialysis patients. Intradialytic exercise is a potential strategy to increase uremic solute removal by increasing blood flow to low perfusion tissue beds. The purpose of this review is to establish the efficacy of intradialytic exercise for hemodialysis adequacy. Additionally, this review aims to provide practical information to aid health care professionals implement intradialytic exercise for dialysis adequacy. Database and hand searches identified 15 published interventional studies that implemented intradialytic exercise for dialysis adequacy as a primary outcome measure in adult maintenance hemodialysis patients. Data pertaining to dialytic solute clearance of urea, creatinine, beta₂ microglobulin, phosphate, and potassium were extracted. Mean differences, normalized to percentages, and effect sizes were calculated and reported. The current data pertaining to the use of intradialytic exercise for improving dialysis adequacy in terms of Kt/V_urea or small molecule uremic toxin clearance are equivocal. Limited data showed that intradialytic exercise has no effect middle molecule toxin (beta₂ - microglobulin) clearance. Intradialytic exercise favored increased phosphate removal showing medium to large effects for reduced serum concentrations, reduced rebound and increased clearance. In summary, supervised light to moderate intradialytic aerobic cycling appears to be beneficial for increasing phosphate removal and may be an adjunct therapy for patients failing to meet clinical phosphate targets. Further work is required to establish the effect of intradialytic exercise on Kt/V_urea and other middle molecule and protein bound solutes. Research aimed at establishing the most effective exercise prescription for improved solute clearance is warranted.

Unique aspects of peripheral artery disease in patients with chronic kidney disease

Peripheral artery disease (PAD) represents a major health care burden. Despite the advent of screening and interventional procedures, the long-term clinical outcomes remain suboptimal, especially in patients with chronic kidney disease (CKD). While CKD and PAD share common predisposing factors, emerging studies indicate that their co-existence is not merely an association; instead, CKD represents a strong, independent risk factor for PAD. These findings implicate CKD-specific mediators of PAD that remain incompletely understood. Moreover, there is a need to understand the mechanisms underlying poor outcomes after interventions for PAD in CKD. This review discusses unique clinical aspects of PAD in patients with CKD, including high prevalence and worse outcomes after vascular interventions and the influence of renal allograft transplantation. In doing so, it also highlights underappreciated aspects of PAD in patients with CKD, such as disparities in revascularization and higher peri-procedural mortality. While previous reviews have discussed general mechanisms of PAD pathogenesis, focusing on PAD in CKD, this review underscores a need to probe for CKD-specific pathogenic pathways that may unravel novel biomarkers and therapeutic targets in PAD and ultimately improve the risk stratification and management of patients with CKD and PAD.

A need for a paradigm shift in focus: From Kt/Vurea to appropriate removal of sodium (the ignored uremic toxin)

Hemodialysis for chronic renal failure was introduced and developed in Seattle, WA, in the 1960s. Using Kiil dialyzers, weekly dialysis time and frequency were established to be about 30 hours on 3 time weekly dialysis. This dialysis time and frequency was associated with 10% yearly mortality in the United States in 1970s. Later in 1970s, newer and more efficient dialyzers were developed and it was felt that dialysis time could be shortened. An additional incentive to shorten dialysis was felt to be lower cost and higher convenience. Additional support for shortening dialysis time was provided by a randomized prospective trial performed by National Cooperative Dialysis Study (NCDS). This study committed a Type II statistical error rejecting the time of dialysis as an important factor in determining the quality of dialysis. This study also provided the basis for the establishment of the Kt/V_urea index as a measure of dialysis adequacy. This index having been established in a sacrosanct randomized controlled trial (RCT), was readily accepted by the HD community, and led to shorter dialysis, and higher mortality in the United States. Kt/V_urea is a poor measure of dialysis quality because it combines three unrelated variables into a single formula. These variables influence the clinical status of the patient independent of each other. It is impossible to compensate short dialysis duration (t) with the increased clearance of urea (K), because the tolerance of ultrafiltration depends on the plasma-refilling rate, which has nothing in common with urea clearance. Later, another RCT (the HEMO study) committed a Type III statistical error by asking the wrong research question, thus not yielding any valuable results. Fortunately, it did not lead to deterioration of dialysis outcomes in the United States. The third RCT in this field ("in-center hemodialysis 6 times per week versus 3 times per week") did not bring forth any valuable results, but at least confirmed what was already known. The fourth such trial ("The effects of frequent nocturnal home hemodialysis") too did not show any positive results primarily due to significant subject recruitment issues leading to inappropriate selection of patients. Comparison of the value of peritoneal dialysis and HD in RCTs could not be completed because of recruitment problems. Randomized controlled trials have therefore failed to yield any meaningful information in the area of dose and or frequency of hemodialysis.

Short, Thrice-Weekly Hemodialysis is Inadequate Regardless of Small Molecule Clearance

Chronic hemodialysis sessions, as developed in Seattle in the 1960s, were long procedures with minimal intra- and interdialytic symptoms. Over the next three decades, financial and logistical pressures related to the overwhelming number of patients requiring hemodialysis created an incentive to shorten dialysis time to four, three, and even two hours per session in a thrice weekly schedule. This method spread rapidly, particularly in the United States, after the National Cooperative Dialysis Study suggested that time of dialysis is of minor importance as long as urea clearance multiplied by dialysis time and scaled to total body water (Kt/Vurea) equals 0.95–1.0. This number was later increased to 1.3, but the assumption that hemodialysis time is of minimal importance, as long as it is compensated by increased urea clearance, remained unchanged. Patients accepted short dialysis as a godsend, believing that it would not be detrimental to their well being and longevity.

However, Kt/Vurea measures only removal of low molecular weight substances and does not consider removal of larger molecules. Nor does it correlate with the other important function of hemodialysis, namely ultrafiltration. Whereas patients with substantial residual renal function may tolerate short dialysis sessions, patients with little or no urine output tolerate short dialyses poorly because at a given interdialytic weight gain the ultrafiltration rate is inversely proportional to dialysis time. Rapid ultrafiltration is associated with cramps, nausea, vomiting, headache, fatigue, hypotensive episodes during dialysis, and hangover after dialysis; patients remain fluid overloaded with subsequent poor blood pressure control leading to left ventricular hypertrophy, diastolic dysfunction, and high cardiovascular mortality.

Short, high-efficiency dialysis requires high blood flow, which increases demands on blood access. The classic, wrist arteriovenous fistula, the access with the best longevity and lowest complication rates, provides “insufficient” blood flow and is replaced with an arteriovenous graft fistula or an intravenous catheter. Moreover, to achieve high blood flows, large diameter intravenous catheters are used; these fit veins “too tightly” and so predispose to central-vein thrombosis.

Longer hemodialysis sessions (5–8 hours, thrice weekly), as practiced in some centers, are associated with lower complication rates and better outcomes. Frequent dialyses (four or more sessions per week) with total weekly dialysis time sufficient to allow gentle ultrafiltration rates provide the best clinical results, but are associated with increased costs which are not properly reimbursed in the USA at present. Therefore, it is my strong belief that before a more appropriate reimbursement is available, a wide acceptance of longer, gentler dialysis sessions, in the current thrice weekly schedule, would improve overall hemodialysis results, decrease access complications, hospitalizations and mortality, particularly in anuric patients.

Kt/Vurea should be abandoned as a measure of dialysis quality. The formula suggests that it is possible to decrease t as long as K is proportionately increased, but this is not true. The use of rigid, quantitative guidelines (e.g., spKt/Vurea of 1.3 per dialysis) assumes that all patients behave identically in response to therapeutic maneuvers, like the mean of the group, but this is also not true. The individual, clinical approach assumes that there are differences among patients, which require adjustment of dialysis schedule for each patient.

Oral iron supplementation: Potential implications for the gut microbiome and metabolome in patients with CKD

Patients with chronic kidney disease (CKD) and loss of kidney function are at increased risk for morbidity and mortality. The risks of CKD are attributed to "uremia," an increased concentration of uremic retention solutes (toxins) in the plasma. Recently, a colo-renal axis became clearly apparent and uremia has been associated with an altered gut microbiome composition and metabolism. There is a high prevalence of anemia in patients with CKD, for which patients are often treated with oral or intravenous iron. Recent in vivo and in vitro studies have reported adverse effects of oral iron supplementation on the gut microbiota composition, gut metabolome, and intestinal health, which in turn may result in an increased production of uremic toxins. It may also affect circulating levels of other microbe-derived molecules, that can act as mediators of immune regulation. Changes in body iron levels have also been reported to exert subtle effects on host immune function by modulating immune cell proliferation and differentiation, and by directly regulating cytokine formation and antimicrobial immune effector mechanisms. Based on the foregoing it is conceivable that oral iron supplementation in iron deficient predialysis CKD patients adversely changes gut microbiota composition, the gut and systemic metabolome, and host immunity and infection. Future studies are needed to confirm these hypotheses and to assess whether, compared to IV iron supplementation, oral iron supplementation negatively impacts on morbidity of CKD, and whether these adverse effects depend on the iron bioavailability of the iron formulation to the microbiota.

Dose Targeting Metrics in Conventional and Intensive Maintenance Dialysis

Hemodialysis has come a long way since its early days and is a life sustaining therapy for millions of people with end-stage kidney disease throughout the world. Although thrice weekly hemodialysis remains the most common form of renal replacement therapy, other therapies such as more frequent, prolonged dialysis modalities have seen a rise recently. In this review, we compare and contrast methods for measuring the dialysis dose, with a focus on small molecule clearance (Kt/V_urea ) among various dialysis modalities. We also describe newer on-line methods to measure dialysis and limitations to current adequacy measurement. Distinguishing dialysis adequacy from adequate treatment of the patient is also emphasized.

The urea decomposition product cyanate promotes endothelial dysfunction

The dramatic cardiovascular mortality of patients with chronic kidney disease is attributable in a significant proportion to endothelial dysfunction. Cyanate, a reactive species in equilibrium with urea, is formed in excess in chronic kidney disease. Cyanate is thought to have a causal role in promoting cardiovascular disease, but the underlying mechanisms remain unclear. Immunohistochemical analysis performed in the present study revealed that carbamylated epitopes associate mainly with endothelial cells in human atherosclerotic lesions. Cyanate treatment of human coronary artery endothelial cells reduced expression of endothelial nitric oxide synthase, and increased tissue factor and plasminogen activator inhibitor-1 expression. In mice, administration of cyanate, promoting protein carbamylation at levels observed in uremic patients, attenuated arterial vasorelaxation of aortic rings in response to acetylcholine without affecting the sodium nitroprusside-induced relaxation. Total endothelial nitric oxide synthase and nitric oxide production were significantly reduced in aortic tissue of cyanate-treated mice. This coincided with a marked increase of tissue factor and plasminogen activator inhibitor-1 protein levels in aortas of cyanate-treated mice. Thus, cyanate compromises endothelial functionality in vitro and in vivo. This may contribute to the dramatic cardiovascular risk of patients suffering from chronic kidney disease.

Interaction between intradialytic exercise and hemodialysis adequacy

BACKGROUND/AIMS

According to mathematical modeling, intradialytic exercise of sufficient intensity and duration implemented in the second half of dialysis should be as efficacious as increasing dialysis time for dialysis adequacy. This assumption has not been tested in vivo.

METHODS

In this controlled trial, 11 hemodialysis (HD) patients (mean (SD) age 56 (13) years) were recruited. Each patient completed three trial arms in a randomized order: routine care (CONT), increased HD time of 30 min (TIME), and intradialytic exercise (EXER), 60 min of cycling at 90% of the lactate threshold in the last 90 min of HD. The primary outcome was eKt/Vurea. Secondary outcomes included reduction and rebound ratios of urea, creatinine, phosphate and β2-microglobulin. Outcomes were calculated from blood sampling collected pre-, post- and 30 min post-HD and confirmed with dialysate sampling.

RESULTS

Exercise was not as efficacious as increased HD time for eKt/Vurea (EXER vs. CONT, mean change (95% CI): 0.03 (-0.05 to 0.12); TIME vs. CONT: 0.15 (0.05-0.26)). Exercise was less efficacious at improving reduction ratios of urea and creatinine. However, exercise was more efficacious than increased dialysis time for phosphate reduction ratio (EXER vs. CONT: 8.6% (0.5-16.7); TIME vs. CONT: 5.0% (-1.0 to 11.1)).

CONCLUSION

This study utilized a rigorously controlled in vivo design to test mathematical models and assumptions regarding dialysis adequacy. Intradialytic exercise towards the end of HD cannot replace the prescription of increased HD time for dialysis adequacy, but may be an adjunctive therapy for serum phosphate control.

Combination of maintenance hemodialysis with hemoperfusion: a safe and effective model of artificial kidney

OBJECTIVE

To investigate whether the combination of maintenance hemodialysis (MHD) with hemoperfusion (HP) could improve the clearance rate of middle and large molecule uremic toxins so as to improve the quality of life of MHD patients and reduce their mortality rate.

METHODS

This study was a prospective, randomized, controlled clinical trial. 100 MHD patients were selected and then randomly divided into two groups after four weeks of run-in period. Group 1 received HD alone 2 times a week and the combined treatment of HD with HP (HD+HP) once a week, whereas Group 2 was given HD alone 3 times a week. This study was followed up for a mean of 2 years. The primary outcome was the death of patients. Secondary end points included normal clinical data, leptin, high sensitive C-reactive protein (hsCRP), interleukin-6 (IL-6), ß(2) microglobulin (ß(2)-MG), immunoreactive parathyroid hormone (iPTH), tumor necrosis factor-α (TNF-α) and the index of dimensions of Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36 Chinese Edition ).

RESULTS

At the end of the two-year observation, the serum concentration of leptin, hsCRP, iPTH, IL-6, ß(2)-MG and TNF-α, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), cardiothoracic ratio, left ventricular mass index (LVMI), the EPO doses and the types of antihypertensive drugs used were lower with Group 1 than with Group 2 (p<0.05); Group 1 had higher hemoglobin (Hb), ejection fraction (EF), and body mass index (BMI) (p<0.05). No statistical difference between the two groups was observed in terms of serum albumin, serum iron (SI), total iron binding capacity (TIBC), cardiac output (CO), Kt/V, early/atrial mitral inflow velocities (E/A) (p>0.05). Besides, the SF-36 indicated that the total score of overall dimentions of Group 1 was higher than Group 2 (p<0.05) and the quality of life of Group 1 was evidently better than Group 2. The Kaplan-Meier Survival Curves for the 2-year observation period showed that patients in Group 1 had obvious survival advantage while Log-rank test results showed p<0.05. No serious adverse incidents occurred during the HD+HP treatment.

CONCLUSIONS

HD+HP was superior to HD in regularly eliminating middle and large molecule uremic toxins accumulated in the body. These findings suggest a potential role for HD+HP in the treatment to improve the quality of life and survival rate of MHD patients.

Treatment time and ultrafiltration rate are more important in dialysis prescription than small molecule clearance

Chronic hemodialysis sessions, as developed in Seattle in the 1960s, were long procedures with minimal intra- and interdialytic symptoms. Over the next three decades, dialysis duration was shorten to 4, 3, even 2 h in thrice weekly schedules. This method spread rapidly, particularly in the United States, after the National Cooperative Dialysis Study suggested that the time of dialysis is of minor importance as long as urea clearance multiplied by dialysis time and scaled to total body water (Kt/V(urea)) equals 0.95-1.0. This number was later increased to 1.3, but the assumption that hemodialysis time is of minimal importance remained unchanged. However, Kt/V(urea) measures only the removal of low molecular weight substances and does not consider the removal of larger molecules. Nor does it correlate with the other important function of hemodialysis, namely ultrafiltration. Rapid ultrafiltration is associated with cramps, nausea, vomiting, headache, fatigue, hypotensive episodes during dialysis, and hangover after dialysis; patients remain fluid overloaded with subsequent poor blood pressure control leading to left ventricular hypertrophy, diastolic dysfunction, and high cardiovascular mortality. Kt/V(urea) should be abandoned as a measure of dialysis quality. The formula suggests that it is possible to decrease t as long as K is proportionately increased, but this is not true. Time of dialysis should be adjusted in such a way that patients would not suffer from symptoms related to rapid ultrafiltration, would not have other uremic symptoms and most patients would have blood pressure controlled without antihypertensive drugs.