Hereditary and acquired cystic disease of the kidney

Relationship between disease awareness and severity of kidney disease in autosomal dominant polycystic kidney disease patients

INTRODUCTION

Polycystic kidney disease (PKD) is responsible for 5%-10% of end-stage renal disease. We examined the relationship between renal and extrarenal findings, disease severity, and the level of consciousness of PKD patients.

METHODS

Patients were asked to answer the questionnaire about PKD. Disease severity was determined according to estimated glomerular filtration rate, and disease awareness was assessed by adapting the Disease Perception Scale to PKD. Awareness of patients was evaluated comparatively with chronic kidney disease stage, age, region, and symptoms.

RESULTS

One out of five patients does not know that this disease is inherited. Mean awareness scores of the patients decreased significantly with increasing age. Awareness scores were significantly higher in patients with flank pain, hematuria, and urinary tract stones.

CONCLUSION

Although PKD is the most common hereditary kidney disease, the rate of patients' knowledge on this subject is low. Increased awareness might lead to better treatment in those patients.

Imaging of Peritoneal Dialysis Complications in Children

Worldwide, peritoneal dialysis (PD) is the preferred renal replacement therapy option for children with end-stage renal disease who are awaiting transplantation. PD involves the instillation of a specifically formulated solution into the peritoneal cavity via a PD catheter, with two-way exchange of solutes and waste products along a concentration gradient. This exchange occurs across the peritoneal membrane. The PD catheter has intraperitoneal, abdominal wall, and external components. Enormous efforts have been directed to augment the efficiency and longevity of the peritoneum as a dialysis system by preventing PD-related infectious and noninfectious complications, which may otherwise result in technique failure and a subsequent temporary or permanent switch to hemodialysis. Imaging has an instrumental role in prompt diagnosis of PD complications and in guiding the management of these complications. The main imaging techniques used in the setting of PD complications-namely, conventional radiography, US, CT, MRI, and peritoneal scintigraphy-as well as the benefits and limitations of these modalities are reviewed. The authors also describe the frequently encountered radiologic findings of each complication. Familiarity with these features enables the radiologist to play a crucial role in early diagnosis of PD complications and aids the pediatric nephrologist in tailoring or discontinuing PD and transitioning to hemodialysis if necessary. Online supplemental material is available for this article. ^©RSNA, 2022.

A possible critical dosing period of p-cumylphenol for development of cystic kidneys in rat neonates

In accordance with a previous report on cystic kidneys induced in rat neonates when dosed with p-cumylphenol (PCP) for 18 days from postnatal day (PND) 4, 3 rat neonates were dosed with PCP once a day for 14 days, either from PND 14, 21, 28, 35, or 42 as W2, W3, W4, W5, and W6 groups, respectively, to investigate whether dosing periods in different PNDs influenced the development of cystic renal tubules. The lesion was striking in the W2 group and at a lesser magnitude in the W3 group, whereas either kidney was unaffected when dosing was initiated beyond PND 28. These findings, together with the results from the previous study, suggested that PND 14-28 is a critical dosing period for PCP to develop cystic kidneys in rat neonates. The lining epithelium of the cystic tubules was immunohistochemically positive for AQP2. This finding and the anatomical location indicated that the cystic tubules were of collecting duct origin. Either obstruction, fluid accumulation, or reparative hyperplasia of the lining epithelium was unlikely to be involved in the formation of cystic tubules lined with a monolayer of cuboidal or columnar epithelium with a high nuclear density. Thus, the follow-up investigation on PCP suggested a critical dosing period of PND 14-28 in rat neonates for the development of cystic dilation of renal collecting ducts. This study further supports that additive hyperplasia of the lining epithelium is a fundamental basis of this unique lesion.

Cancer Screening in End-Stage Kidney Disease

The incidence of cancer is higher in patients with end-stage kidney disease (ESKD) than among the general population. Despite this, screening for cancer is generally not cost-effective and may worsen quality of life in these patients. This is due to high mortality rates (patients are not living long enough to reap the benefits of screening), the inaccuracy of cancer screening tests, and the increased risks associated with therapy in patients with ESKD. Specific groups of patients with ESKD who have a longer-than-expected life expectancy or higher-than-expected cancer risk may benefit from screening. These groups include patients on peritoneal dialysis, patients on home hemodialysis, Black and Asian-American patients, transplant-eligible patients, and those at higher risk of cancer including patients with acquired cystic kidney disease, those who have been previously exposed to cytotoxic agents or aristolochic acid, and patients with a genetic predisposition to cancer. In this narrative review, we will examine the prevalence of and risk factors for cancer in patients with ESKD and the effectiveness of cancer screening, and discuss specific situations in which cancer screening may be effective.

Mutational screening of PKD1 and PKD2 in Indian ADPKD patients identified 95 genetic variants

BACKGROUND

Mutation screening of autosomal dominant polycystic kidney disease (ADPKD) cases imply the major involvement of PKD1 mutations in 85% of patients while rest of the cases harbor mutation in PKD2, DNAJB11 and GANAB. This essentially indicates that individual's genotype holds the key for disease susceptibility and its severity.

METHODS

For finding genetic variability underlying the disease pathophysiology, 84 Indian ADPKD cases, 31 family members (12 susceptible) and 122 age matched control were screened for PKD1 and PKD2 using Sanger sequencing, PCR-RFLP and ARMS-PCR.

RESULTS

Genetic screening of Indian ADPKD cases revealed total 67 variants in PKD1 and 28 variants in PKD2. Among the identified variants in PKD1 and PKD2 genes, 35.79% were novel variants and 64.2% recurrent. Further, subcategorization of PKD1 variants showed 14 truncation/frameshift, 21 nonsynonymous, 25 synonymous and 7 intronic variants. Moreover, we observed 40 families with PKD1 pathogenic variants, 7 families with PKD2 pathogenic variants, 9 families with PKD1 & PKD2 pathogenic variants, and 26 families with PKD1/PKD2/PKD1-PKD2 non-pathogenic genetic variants.

CONCLUSION

Present study represented genetic background of Indian ADPKD cases which will be helpful in disease management as well as finding the genetically matched donor for kidney transplant.

Chloroquine attenuates lithium-induced NDI and proliferation of renal collecting duct cells

Lithium is widely used in psychiatry as the golden standard for more than 60 yr due to its effectiveness. However, its adverse effect has been limiting its long-term use in clinic. About 40% of patients taking lithium develop nephrogenic diabetes insipidus (NDI). Lithium can also induce proliferation of collecting duct cells, leading to microcyst formation in the kidney. Lithium was considered an autophagy inducer that might contribute to the therapeutic benefit of neuropsychiatric disorders. Thus, we hypothesized that autophagy may play a role in lithium-induced kidney nephrotoxicity. To address our hypothesis, we fed mice with a lithium-containing diet with chloroquine (CQ), an autophagy inhibitor, concurrently. Lithium-treated mice presented enhanced autophagy activity in the kidney cortex and medulla. CQ treatment significantly ameliorated lithium-induced polyuria, polydipsia, natriuresis, and kaliuresis accompanied with attenuated downregulation of aquaporin-2 and Na⁺-K⁺-2Cl^- cotransporter protein. The protective effect of CQ on aquaporin-2 protein abundance was confirmed in cultured cortical collecting duct cells. In addition, we found that lithium-induced proliferation of collecting duct cells was also suppressed by CQ as detected by proliferating cell nuclear antigen staining. Moreover, both phosphorylated mammalian target of rapamycin and β-catenin expression, which have been reported to be increased by lithium and associated with cell proliferation, were reduced by CQ. Taken together, our study demonstrated that CQ protected against lithium-induced NDI and collecting duct cell proliferation possibly through inhibiting autophagy.

Polycystin 2 is increased in disease to protect against stress-induced cell death

Polycystin 2 (PC2 or TRPP1, formerly TRPP2) is a calcium-permeant Transient Receptor Potential (TRP) cation channel expressed primarily on the endoplasmic reticulum (ER) membrane and primary cilia of all cell and tissue types. Despite its ubiquitous expression throughout the body, studies of PC2 have focused primarily on its role in the kidney, as mutations in PC2 lead to the development of autosomal dominant polycystic kidney disease (ADPKD), a debilitating condition for which there is no cure. However, the endogenous role that PC2 plays in the regulation of general cellular homeostasis remains unclear. In this study, we measure how PC2 expression changes in different pathological states, determine that its abundance is increased under conditions of cellular stress in multiple tissues including human disease, and conclude that PC2-deficient cells have increased susceptibility to cell death induced by stress. Our results offer new insight into the normal function of PC2 as a ubiquitous stress-sensitive protein whose expression is up-regulated in response to cell stress to protect against pathological cell death in multiple diseases.

Prevalence, risk factors and disease knowledge of polycystic kidney disease in Pakistan

Polycystic kidneys disease refers to cyst(s) formation in kidneys with severe consequences of end stage renal disease thus have higher mortality. It is a common genetic disease occurring either as autosomal dominant polycystic kidney (ADPKD) or autosomal recessive polycystic kidney disease (ARPKD) with prevalence rates of 1/1000 and 1/40,000 respectively. Dominant forms presenting in later (>30) while recessive in earlier ages (infancy) and affecting both sexes and almost all race. The patient experiences many renal as well as extra-renal manifestations with marked hypertension and cyst formation in other organs predominantly in liver. Due to genetic basis, positive family history is considered as major risk factor. Ultrasonography remains the main stay of diagnosis along with family history, by indicating increased renal size and architectural modifications. Initially disease remains asymptomatic, later on symptomatic treatment is suggested with surgical interventions like cyst decortications or drainage. Dialysis proved to be beneficial in end stage renal disease. However renal transplantation is the treatment of choice.

Pathologic characterization of renal epithelial neoplasms arising in nonfunctioning kidneys

Nonfunctioning kidneys secondary to various etiologies display different histopathological features. Studies focused on incidence and types of renal neoplasms using the new World Health Organization and International Society of Urological Pathology classification system in various types of nonfunctioning kidneys are very limited. We identified 311 nephrectomies of nonfunctioning kidneys and categorized them into 5 categories: acquired cystic kidney disease (ACKD, n = 61); end-stage renal disease, nonspecific (ESRD, n = 63); adult polycystic kidney disease (APKD, n = 49); failed transplant kidney (FTK, n = 96); and those caused by obstructive conditions in the kidney (OCK, n = 42). ACKD (70%) and ESRD (43%) had higher cancer incidences than the other 3 groups (APKD = 2%, FTK = 0%, and OCK = 5%). Besides clear cell renal cell carcinoma (RCC) and papillary RCC, clear cell papillary RCC had a much higher incidence within ACKD patients (13/61) compared to other groups. ACKD-associated RCC was only identified in ACKD patients. ACKD patients had significantly longer dialysis duration compared to ESRD, APKD, and FTK. Although they had similar risk for clear cell RCC and papillary RCC, ACKD patients had a much higher risk for ACKD-associated RCC and clear cell papillary RCC than ESRD patients. Although most RCCs arising in these nonfunctioning kidneys were early pT1 stage, 6 ACKD patients and 3 ESRD patients had higher-stage diseases, which can be fatal if not treated appropriately. Therefore, precise clinicopathological classification of these nonfunctioning kidneys is important for predicting kidney cancer risk. These results indicate the need for active monitoring of the patients with high-risk nonfunctioning kidney diseases and appropriate surgical treatment when necessary.

Polycystin 2: A calcium channel, channel partner, and regulator of calcium homeostasis in ADPKD

Polycystin 2 (PC2) is one of two main protein types responsible for the underlying etiology of autosomal dominant polycystic kidney disease (ADPKD), the most prevalent monogenic renal disease in the world. This debilitating and currently incurable condition is caused by loss-of-function mutations in PKD2 and PKD1, the genes encoding for PC2 and Polycystin 1 (PC1), respectively. Two-hit mutation events in these genes lead to renal cyst formation and eventual kidney failure, the main hallmarks of ADPKD. Though much is known concerning the physiological consequences and dysfunctional signaling mechanisms resulting from ADPKD development, to best understand the requirement of PC2 in maintaining organ homeostasis, it is important to recognize how PC2 acts under normal conditions. As such, an array of work has been performed characterizing the endogenous function of PC2, revealing it to be a member of the transient receptor potential (TRP) channel family of proteins. As a TRP protein, PC2 is a nonselective, cation-permeant, calcium-sensitive channel expressed in all tissue types, where it localizes primarily on the endoplasmic reticulum (ER), primary cilia, and plasma membrane. In addition to its channel function, PC2 interacts with and acts as a regulator of a number of other channels, ultimately further affecting intracellular signaling and leading to dysfunction in its absence. In this review, we describe the biophysical and physiological properties of PC2 as a cation channel and modulator of intracellular calcium channels, along with how these properties are altered in ADPKD.

Urine Osmolality and Renal Outcome in Patients with Chronic Kidney Disease: Results from the KNOW-CKD

BACKGROUND

Urine osmolality indicates the ability of the kidney to concentrate the urine and reflects the antidiuretic action of vasopressin. However, results about the association between urine osmolality and adverse renal outcomes in chronic kidney disease (CKD) are conflicting. We investigated the association between urine osmolality and adverse renal outcomes in a nationwide prospective CKD cohort.

METHODS

A total of 1,999 CKD patients were categorized into 3 groups according to their urine osmolality tertiles. Primary outcome was a composite of 50% decline in the estimated glomerular filtration rate (eGFR), initiation of dialysis, or kidney transplantation.

RESULTS

During a mean follow-up of 35.2 ± 19.0 months, primary outcome occurred in 432 (21.6%) patients; 240 (36.4%), 162 (24.3%), and 30 (4.5%) in the lowest, middle, and highest tertiles, respectively. Low urine osmolality was independently associated with a greater risk of CKD progression (hazard ratio [HR], 1.71; 95% confidence interval [CI], 1.12-2.59). This association was particularly evident in patients with CKD stages 3-4 (per 10 mosm/kg decrease; HR, 1.02; 95% CI, 1.00-1.03). Adding urine osmolality to a base model with conventional factors significantly increased the ability to predict CKD progression (C-statistics, 0.86; integrated discrimination improvement [IDI], 0.021; both p < 0.001). However, adding both urine osmolality and eGFR did not further improve the predictive ability compared with the addition of eGFR only (C-statistics, p = 0.29; IDI, p = 0.09).

CONCLUSIONS

Low urine osmolality was an independent risk factor for adverse renal outcomes in CKD patients, but its predictive ability did not surpass eGFR. Thus, kidney function should be considered while interpreting the clinical significance of urine osmolality.

Acute pancreatitis in children on chronic maintenance dialysis

Patients on dialysis are exposed to a series of factors that are known to be associated with risk of acute pancreatitis (AP), including medications, hyperparathyroidism, hypercalcemia, and hypertriglyceridemia; the role of the dialysis modality itself is still debated. Data regarding AP in children on chronic dialysis are scarce. Data from the Italian Registry of Pediatric Chronic Dialysis (IRPCD) confirm that children on dialysis have a significant increased relative risk (RR) for AP as compared with the general pediatric population (RR 60.4; 95% CI 3.2-214). Diagnosis of AP in patients on dialysis may be troublesome, because it can mimic other acute intraabdominal conditions and the role of serum pancreatic enzyme assays may be confounding. In this setting, instrumental imaging is mandatory. Conservative management such as fluid, bowel rest, and antibiotics is the mainstay of AP management, as necrotizing forms are rare. Mortality in the series of 12 patients from the IRPCD was high (25%), but deaths were not directly related to AP. Adult case series confirm that mortality among patients on dialysis who develop AP is highly variable (8-58%), but higher as compared to 10% mortality from AP in non-renal failure patients.

Mutational screening of PKD2 gene in the north Indian polycystic kidney disease patients revealed 28 genetic variations

Polycystic kidney disease (PKD) is a systemic disorder which adds majority of renal patients to end stage renal disease. Autosomal dominant polycystic kidney disease (ADPKD) is more prevalent and leading cause of dialysis and kidney transplant. Linkage analysis revealed some closely linked loci, two of which are identified as PKD1, PKD2 and an unidentified locus to ADPKD. This study was performed using PCR and automated DNA sequencing in 84 cases and 80 controls to test potential candidature of PKD2 as underlying cause of PKD by in silico and statistical analyses. Two associated symptoms, hypertension (19%) and liver cyst (31%) havemajor contribution to PKD. Gender-based analysis revealed that familial female patients (27%) and familialmale patients (33%) are more hypertensive. Liver cyst, the second major contributing symptom presented by large percentage of sporadic males (46%). Genetic screening of all 15 exons of PKD2 revealed eight pathogenic (c.854_854delG, c.915C>A, c.973C>T, c.1050_1050delC, c.1604_1604delT, c.1790T>C, c.2182_2183delAG, c.2224C>T) and eight likely pathogenic (g.11732A>G, c.646T>C, c.1354A>G, g.39212G>C, c.1789C>A, c.1849C>A, c.2164G>T, c.2494A>G)DNA sequence variants. In our study, 27.38% (23/84) cases shown pathogenic / likely pathogenic variants in PKD2 gene. Some regions of PKD2 prone for genetic variation suggested to be linked with disease pathogenesis. This noticeable hot spot regions hold higher frequency (50%) of pathogenic / likely pathogenic genetic variants constituting single nucleotide variants than large deletion and insertion that actually represents only 41.08% of coding sequence of PKD2. Statistically significant association for IVS3-22AA genotype was observed with PKD, while association of IVS4+62C>T was found insignificant.

Severity of diverticulitis in patients with polycystic kidney disease without transplantation

BACKGROUND

Patients with polycystic kidney disease (PKD) who have had a kidney transplant have an increased risk of diverticular disease and complicated diverticulitis. Literature is limited regarding the severity of diverticulitis in patients with PKD who have not had a transplant. We aim to assess whether patients with PKD, with and without renal transplant, have a similar course of diverticulitis.

METHODS

A retrospective review of all adult PKD patients at our institution diagnosed with diverticulitis between 2000 and 2016 was conducted. Patients without documented PKD and diverticulitis were excluded. We compared PKD patients with and without renal transplantation.

RESULTS

A total of 41 patients were identified. Mean age was 60 (± 12), and 56% were female. Fourteen patients had undergone renal transplantation. Five (19%) non-transplant patients had complicated diverticulitis, compared to 43% (n = 6) transplanted (p = 0.33). Fifteen (56%) non-transplant and 8 (57%) transplant patients had recurrent diverticulitis (p = 1.00). Three (11%) non-transplant and 5 (36%) transplanted patients had recurrent complicated diverticulitis. Eight (30%) non-transplant and 7 (50%) transplant patients underwent surgery (p = 0.31). All 8 non-transplant patients underwent sigmoid resection with primary anastomosis without diversion. In the transplant group, 3 Hartmann procedures and 1 sigmoid resection with and 3 without diversion were performed. There was one in-hospital death in each group.

CONCLUSION

In our group of patients, there was no difference in rate of recurrent diverticulitis, diverticulitis complications, or operative intervention in patients with PKD with and without renal transplant. The renal transplant group had a higher rate of recurrent, complicated diverticulitis.

Urine Concentrating Capacity, Vasopressin and Copeptin in ADPKD and IgA Nephropathy Patients with Renal Impairment

Background

Autosomal Dominant Polycystic Kidney Disease (ADPKD) patients have an impaired urine concentrating capacity. Increased circulating vasopressin (AVP) concentrations are supposed to play a role in the progression of ADPKD. We hypothesized that ADPKD patients have a more severely impaired urine concentrating capacity in comparison to other patients with chronic kidney disease at a similar level of kidney function, with consequently an enhanced AVP response to water deprivation with higher circulating AVP concentrations.

Methods

15 ADPKD (eGFR<60) patients and 15 age-, sex- and eGFR-matched controls with IgA nephropathy (IgAN), underwent a water deprivation test to determine maximal urine concentrating capacity. Plasma and urine osmolality, urine aquaporin-2 (AQP2) and plasma AVP and copeptin (a surrogate marker for AVP) were measured at baseline and after water deprivation (average 16 hours). In ADPKD patients, height adjusted total kidney volume (hTKV) was measured by MRI.

Results

Maximal achieved urine concentration was lower in ADPKD compared to IgAN controls (533±138 vs. 642±148 mOsm/kg, p = 0.046), with particularly a lower maximal achieved urine urea concentration (223±74 vs. 299±72 mmol/L, p = 0.008). After water deprivation, plasma osmolality was similar in both groups although change in plasma osmolality was more profound in ADPKD due to a lower baseline plasma osmolality in comparison to IgAN controls. Copeptin and AVP increased significantly in a similar way in both groups. AVP, copeptin and urine AQP2 were inversely associated with maximal urine concentrating in both groups.

Conclusions

ADPKD patients have a more severely impaired maximal urine concentrating capacity with a lower maximal achieved urine urea concentration in comparison to IgAN controls with similar endogenous copeptin and AVP responses.

Endovascular Treatment of Intracranial Aneurysms in Patients With Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Little is known about the outcome of endovascular treatment for intracranial aneurysms in patients with autosomal dominant polycystic kidney disease (ADPKD).

OBJECTIVE

To present clinical outcomes in terms of safety, effectiveness, and renal functions to assess contrast-induced nephropathy in endovascular coil embolization for intracranial aneurysms in ADPKD patients.

METHODS

Nineteen ADPKD patients (female:male, 15:4; mean age, 49.8 years; range, 20-67 years) had 26 aneurysms (mean size, 5.86 mm; range, 2.5-11.6 mm) and underwent 22 endovascular treatment sessions from 2001 to 2013. Four patients presented with ruptured aneurysms. Periprocedural complications, clinical outcomes with modified Rankin Scale scores, laboratory findings, and chronic kidney disease (CKD) stage before and after treatment were documented. Acute renal impairment was defined as serum creatinine (Cr) elevation by ≥ 0.5 mg/dL or 25% relative to baseline.

RESULTS

Symptomatic periprocedural complications developed after 1 endovascular procedure (1 of 22, 4.5%), and good clinical outcomes (modified Rankin Scale scores, 0-1) were achieved in 90% of patients (17 of 19). Overall, acute renal impairment occurred in 9.1% of treatment sessions (2 of 22). Acute renal impairment developed in 25% of high-risk patients (baseline Cr > 2.0 mg/dL) and 33.3% of baseline CKD stage 5 sessions but in none of the low-risk patients (baseline Cr ≤ 2.0 mg/dL) and in no CKD stage 1 to 4 sessions.

CONCLUSION

With appropriate management, coil embolization may be safe and effective for intracranial aneurysms in ADPKD. There is a concern about contrast-induced nephropathy in patients with CKD stage 5 or high serum Cr level (>2.0 mg/dL).

Outcomes of living kidney donors with medullary sponge kidney

BACKGROUND

Patients with medullary sponge kidney (MSK) commonly encounter recurrent nephrolithiasis. The existing knowledge on safety of donors with MSK has not been studied.

METHODS

We conducted a retrospective cohort study at a tertiary referral hospital to assess the outcomes of living kidney donors with MSK. All adults with MSK (N = 26) who underwent nephrectomy as living kidney donors between January 2000 and September 2014 were included. Non-donors with MSK (N = 78) were randomly selected by matching the year of birth and the comorbidity score with a ratio of 1:3 for comparison.

RESULTS

The incident rates of symptomatic stone were 0.7, 0.4 and 4.9 events/100 patient-years in donors, recipients and non-donors, respectively. After adjusting for history of kidney stones and baseline estimated glomerular filtration rate (eGFR), the kidney stone-related event was significantly lower in donors than in non-donors (hazard ratio 0.14; 95% confidence interval 0.01-0.66). One recipient of MSK living donor had symptomatic stone at median follow-up time of 8.4 years (interquartile range 5.6-12.4 years). None of MSK donors had hypercalciuria, hypocitraturia or hyperoxaluria prior to kidney donation. At 5 years after the index surgery date, there was no significant difference in eGFR between donors and non-donors (76.1 versus 70.9 mL/min/1.73 m², P = 0.12).

CONCLUSIONS

These findings are reassuring for the safety of MSK kidney donors with normal kidney function, low kidney stone risk and no significant comorbidity.

Diagnosis and evaluation of renal cysts

Renal cysts are commonly encountered in clinical practice. Although most cysts found on routine imaging studies are benign, there must be an index of suspicion to exclude a neoplastic process or the presence of a multicystic disorder. This article focuses on the more common adult cystic diseases, including simple and complex renal cysts, autosomal-dominant polycystic kidney disease, and acquired cystic kidney disease.

Clinical and ultrasonographical characterization of childhood cystic kidney diseases in Egypt

BACKGROUND

Renal cystic disorders (RCD) constitute an important and leading cause of end-stage renal disease (ESRD) in children. It can be acquired or inherited; isolated or associated with extrarenal manifestations. The precise diagnosis represents a difficult clinical challenge.

METHODS

The aim of this study was to define the pattern of clinical phenotypes of children with renal cystic diseases in Pediatric Nephrology Center, Cairo University. We have studied the clinical phenotypes of 105 children with RCD [45 (43%) of them had extrarenal manifestations].

RESULTS

The most common disorders were the presumably inherited renal cystic diseases (65.7%) mainly nephronophthisis and related ciliopathies (36.2%), as well as polycystic kidney diseases (29.5%). Moreover, multicystic dysplastic kidneys accounted for 18% of study cases. Interestingly, eight syndromic cases are described, yet unclassified as none had been previously reported in the literature.

CONCLUSION

RCD in this study had an expanded and complex spectrum and were largely due to presumably inherited/genetic disorders (65.7%). Moreover, we propose a modified algorithm for clinical and diagnostic approach to patients with RCD.

Should patients with autosomal dominant polycystic kidney disease be screened for cerebral aneurysms?

Autosomal dominant polycystic kidney disease is a genetic disorder affecting 1 in 1000 people worldwide and is associated with an increased risk of intracranial aneurysms. It remains unclear whether there is sufficient net benefit to screening this patient population for IA, considering recent developments in imaging and treatment and our evolving understanding of the natural history of unruptured aneurysms. There is currently no standardized screening protocol for IA in patients with ADPCKD. Our review of the literature focused on the above issues and presents our appraisal of the estimated value of screening for IA in the setting of ADPCKD.

Soluble klotho and autosomal dominant polycystic kidney disease

BACKGROUND AND OBJECTIVES

Fibroblast growth factor 23 (FGF23) levels are elevated in patients with autosomal dominant polycystic kidney disease (ADPKD) and X-linked hypophosphatemia (XLH), but only the latter is characterized by a renal phosphate wasting phenotype. This study explored potential mechanisms underlying resistance to FGF23 in ADPKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

FGF23 and klotho levels were measured, and renal phosphate transport was evaluated by calculating the ratio of the maximum rate of tubular phosphate reabsorption to GFR (TmP/GFR) in 99 ADPKD patients, 32 CKD patients, 12 XLH patients, and 20 healthy volunteers. ADPKD and CKD patients were classified by estimated GFR (CKD stage 1, ≥90 ml/min per 1.73 m(2); CKD stage 2, 60-89 ml/min per 1.73 m(2)).

RESULTS

ADPKD patients had 50% higher FGF23 levels than did XLH patients; TmP/GFR was near normal in most ADPKD patients and very low in XLH patients. Serum klotho levels were lowest in the ADPKD group, whereas the CKD and XLH groups and volunteers had similar levels. ADPKD patients with an apparent renal phosphate leak had two-fold higher klotho levels than those without. Serum klotho values correlated inversely with cyst volume and kidney growth.

CONCLUSIONS

Loss of klotho might be a consequence of cyst growth and constrain the phosphaturic effect of FGF23 in most patients with ADPKD. Normal serum klotho levels were associated with normal FGF23 biologic activity in all XLH patients and a minority of ADPKD patients. Loss of klotho and FGF23 increase appear to exceed and precede the changes that can be explained by loss of GFR in patients with ADPKD.

Factors related to the absence of anemia in hemodialysis patients

BACKGROUND

A small number of hemodialysis (HD) patients have normal hemoglobin (Hb) levels without the need for erythropoiesis-stimulating agents (ESAs). The factors associated with this condition have been little studied. The objective of this prospective study was to determine these factors in a prevalent population of HD patients.

MATERIALS AND METHODS

All patients who had normal Hb levels and who had not received ESAs in the last 6 months (non-ESA group) were included. Epidemiological and laboratory data were collected and we performed an abdominal ultrasound to assess hepatic and renal cysts. This group was compared to a control group of 205 prevalent HD patients on ESA therapy (control group).

RESULTS

We included 45 patients (16% from the whole group) in the non-ESA group. In this group, there was a higher proportion of men (76.5 vs. 61%), patients were younger (61.1 ± 14.7 vs. 67.5 ± 15.2 years), had a longer duration of renal replacement therapy (RRT) (9.4 ± 8.3 vs. 5.3 ± 5.8 years) and had a higher prevalence of adult polycystic kidney disease (APKD) and hepatitis C virus (HCV) liver disease (42.2 vs. 10.2%), p < 0.01. In the non-ESA group, HCV+ patients had a lower prevalence of APKD (2.2 vs. 38.4%) and hepatic cysts (2.2 vs. 19.2%), but significantly higher endogenous erythropoietin levels (55.8 ± 37.1 vs. 30.9 ± 38.4 mU/ml). No significant differences in anemia, iron metabolism, insulin, IGF-1 and renin were found between non-ESA and control groups. Non-ESA patients had a significantly higher number of renal (90.6 vs. 36.5%) and hepatic cysts (12.5 vs. 3.4%), and these were also larger in size (3.3 ± 2.4 vs. 1.5 ± 0.8 cm). In the multivariate Cox analysis, independent predictor factors for absence of anemia in HD patients were number of renal cysts >10 cysts (95% CI 1.058-1.405; p = 0.00), HCV+ liver disease (95% CI 1.147-1.511; p = 0.05) and time on RRT (95% CI 1.002-1.121; p = 0.05).

CONCLUSIONS

The absence of anemia in HD patients is not infrequent. Its frequency is higher in men and younger patients with long-term RRT, in patients with HCV+ liver disease and in APKD. It is associated with increased endogenous erythropoietin production and the presence of renal and hepatic cysts.

The non-neoplastic kidney in tumor nephrectomy specimens: what can it show and what is important?

Surgical nephrectomy is a procedure that has been performed for nearly 100 years. In the presence of a normal contralateral kidney, such as in a renal transplant donor or child with Wilms tumor, it is a benign procedure without deleterious consequences on the remaining kidney. However, many adults and some children postnephrectomy will develop chronic kidney disease. The non-neoplastic kidney in tumor resections may harbor a large number of developmental and acquired diseases predictive of this outcome or that convey other medically significant information. Examination of the non-neoplastic kidney is a fertile opportunity to identify these unsuspected conditions that may ultimately dictate the subsequent clinical course and influence the medical care provided. This review discusses the consequences of unilateral and partial nephrectomy, and illustrates many conditions that may be encountered in the non-neoplastic cortex with a discussion of their clinical implications.

Renal cystic diseases and renal neoplasms: a mini-review

The past two decades have witnessed recognition of several new types of renal cell carcinoma, each with distinct cytogenetic abnormalities. Included are several genetic and acquired cystic kidney diseases associated with development of renal cell carcinoma, the topic of this review. The risk in patients with autosomal dominant polycystic kidney disease is not accurately known but may be slightly increased. The risk for patients with von Hippel-Lindau disease is substantial, and death from renal cancer is common. For patients with tuberous sclerosis complex, the challenge is recognition of the occasional malignancy arising in a field of many benign tumors. Patients with end-stage kidney disease and acquired cystic kidney disease may develop a variety of renal cell carcinoma types. Progress in understanding the molecular basis of renal cyst formation and neoplastic disease has fostered development of targeted therapies that now hold promise for a group of neoplasms whose cure was traditionally dependent on surgical approaches.

Cystin localizes to primary cilia via membrane microdomains and a targeting motif

Primary cilia are dynamic, complex structures that contain >500 proteins, including several related to polycystic kidney disease. How these proteins target to cilia and assemble is unknown. We previously identified Cys1 as the gene responsible for disease in Cys1(cpk) mice, a mouse model of autosomal recessive polycystic kidney disease; this gene encodes cystin, a 145-amino acid cilium-associated protein. Here, we characterized the localization of cystin in the embryonic kidney and liver, in isolated renal collecting ducts, and in an inner medullary collecting duct mouse cell line. Because endogenous levels of cystin expression are low, we generated inner medullary collecting duct cell lines that stably express enhanced green fluorescence protein-tagged constructs of wild-type cystin or various truncation mutants. We determined that cystin is myristoylated at its G2 residue and that N-myristoylated cystin fractionates with membrane microdomains. Furthermore, the N-myristoylation signal is necessary but not sufficient to target cystin to the primary cilium. Analysis of deletion and chimeric constructs identified an AxEGG motif that is necessary to target and retain cystin in the cilium. Derangement of these localization motifs may lead to cystic kidney disease.

Advances in management of polycystic liver disease

The focus of this review is polycystic liver disease, a genetic disorder characterized by multiple macroscopic liver cysts that initially bud from biliary epithelium but subsequently lack communication with the biliary tree. There are two main clinical presentations: polycystic liver associated with autosomal dominant polycystic kidney disease and isolated polycystic liver disease. Both of these forms of polycystic liver disease exhibit an autosomal dominant pattern of inheritance. Clinical manifestations of polycystic liver disease are related to either mass effect of the volume of hepatic cysts or to complications arising within the cysts. Polycystic liver disease rarely progresses to hepatic failure or clinical complications of portal hypertension. Management is directed at counseling patients and families, treating complications and reducing cyst load by surgical techniques: cyst fenestration, hepatic resection or, rarely, hepatic transplantation. Recent research suggests that blockade of cyst secretion or inhibition of epithelial cells might be useful in halting progression of disease--these observations are discussed in this review.

Diagnosis of autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and accounts for 5 - 10% of end stage renal disease. Mutations of two genes, PKD1 and PKD2, account for ∼ 85 and ∼ 15% of cases, respectively.

OBJECTIVE

This paper reviews the clinical features of ADPKD, highlights the current roles for image- and molecular-based diagnostics, and the potential for new innovations to improve the clinical diagnostics for ADPKD.

METHODS

This paper reviews the literature on the clinical features, differential diagnosis, and image- and molecular-based diagnostics for ADPKD.

RESULTS/CONCLUSION

At present, presymptomatic diagnosis of ADPKD in subjects born with 50% risk is typically performed by renal ultrasonography. Renal MRI, with improved sensitivity for detecting smaller cysts, is a promising modality. There is also a clear role for molecular diagnostics, especially in patients with equivocal imaging results, in those with a negative family history and in younger at-risk subjects with a negative ultrasound study being evaluated as a living-related kidney donor. Also, several classes of promising disease-modifying drugs are being tested in clinical trials and, if proved effective, some of them will be used in early disease. Therefore, it is likely that there will be an increased demand for accurate and early diagnosis of ADPKD in the not so distant future.

Ciliary dysfunction in polycystic kidney disease: an emerging model with polarizing potential

The majority of different cell types in the human body have a cilium, a thin rod-like structure of uniquely arranged microtubules that are encapsulated by the surface plasma membrane. The cilium originates from a basal body, a mature centriole that has migrated and docked to the cell surface. The non-motile cilia are microtubule-based organelles that are generally considered sensory structures. The purpose of this review is to discuss the practicality of the ciliary hypothesis as a unifying concept for polycystic kidney disease and to review current literature in the field of cilium biology, as it relates to mechanosensation and planar cell polarity. The polycystins and fibrocystin localization at the cilium and other subcellular localizations are discussed, followed by a hypothetical model for the cilium's role in mechanosensing, planar cell polarity, and cystogenesis.

Physiology and pathophysiology of the vasopressin-regulated renal water reabsorption

To prevent dehydration, terrestrial animals and humans have developed a sensitive and versatile system to maintain their water homeostasis. In states of hypernatremia or hypovolemia, the antidiuretic hormone vasopressin (AVP) is released from the pituitary and binds its type-2 receptor in renal principal cells. This triggers an intracellular cAMP signaling cascade, which phosphorylates aquaporin-2 (AQP2) and targets the channel to the apical plasma membrane. Driven by an osmotic gradient, pro-urinary water then passes the membrane through AQP2 and leaves the cell on the basolateral side via AQP3 and AQP4 water channels. When water homeostasis is restored, AVP levels decline, and AQP2 is internalized from the plasma membrane, leaving the plasma membrane watertight again. The action of AVP is counterbalanced by several hormones like prostaglandin E2, bradykinin, dopamine, endothelin-1, acetylcholine, epidermal growth factor, and purines. Moreover, AQP2 is strongly involved in the pathophysiology of disorders characterized by renal concentrating defects, as well as conditions associated with severe water retention. This review focuses on our recent increase in understanding of the molecular mechanisms underlying AVP-regulated renal water transport in both health and disease.

Management of polycystic liver disease

The adult forms of polycystic liver disease are characterized by autosomal dominant inheritance and numerous hepatic cysts, with or without renal involvement. Mutations in two distinct genes predispose to renal and liver cysts (PKD1 and PKD2), and mutations in two different genes yield isolated liver cysts (PRKCSH and SEC63). Mutations at certain loci of PKD1 may predispose to more severe renal cystic disease or cerebral aneurysms. Risk factors for severe hepatic cystic disease include aging, female sex, pregnancy, use of exogenous female steroid hormones, degree of renal cystic disease, or severity of renal dysfunction (in patients with mutations in PKD1 or PKD2). Although liver failure or complications of advanced liver disease is rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Treatment options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Analysis of PKD1 for genomic deletion by multiplex ligation-dependent probe assay: absence of hot spots

Autosomal dominant polycystic kidney disease is largely due to mutations in PKD1. PKD1 has an unusual genomic structure, including a 2.5-kb polypyrimidine sequence in intron 21, which has been postulated to lead to a high rate of spontaneous genomic mutation events. In addition, the majority of the gene is duplicated three to six times at 97-99% identity elsewhere in the genome. To identify genomic mutations in PKD1, we developed a multiplex ligation-dependent probe assay (MLPA) in which sites of variation between PKD1 and its copies were positioned at the ligation sites of the MLPA probe sets. Thirteen probe sets covered PKD1 exons 2 through 46, at an average spacing of 2.5 kb. Analysis of 27 independent PKD patient samples showed no evidence for genomic deletions confined to PKD1. Analysis of 15 tuberous sclerosis patient samples in which deletions in TSC2 extended into PKD1 showed no evidence of clustering of breakpoints near the polypyrimidine tract.

Role of primary cilia in the pathogenesis of polycystic kidney disease

Cysts in the kidney are among the most common inherited human pathologies, and recent research has uncovered that a defect in cilia-mediated signaling activity is a key factor that leads to cyst formation. The cilium is a microtubule-based organelle that is found on most cells in the mammalian body. Multiple proteins whose functions are disrupted in cystic diseases have now been localized to the cilium or at the basal body at the base of the cilium. Current data indicate that the cilium can function as a mechanosensor to detect fluid flow through the lumen of renal tubules. Flow-mediated deflection of the cilia axoneme induces an increase in intracellular calcium and alters gene expression. Alternatively, a recent finding has revealed that the intraflagellar transport 88/polaris protein, which is required for cilia assembly, has an additional role in regulating cell-cycle progression independent of its function in ciliogenesis. Further research directed at understanding the relationship between the cilium, cell-cycle, and cilia-mediated mechanosensation and signaling activity will hopefully provide important insights into the mechanisms of renal cyst pathogenesis and lead to better approaches for therapeutic intervention.

Screening, diagnosis, and treatment of cancer in long-term dialysis patients

Some have suggested that the American Cancer Society guidelines for cancer screening be applied to patients who are on long-term dialysis and have used cancer screening as a means of assessing delivered preventive health care to patients with ESRD. However, cancer screening is effective only when it leads to survival benefit (usually expressed as days of life saved) without incurring high financial costs. Certain cancers such as human papillomavirus-associated cervical and tongue cancer and urologic malignancies are more common among dialysis patients, yet because the expected remaining lifetime of most dialysis patients is shorter than the time lived to develop malignancy, cancer screening in dialysis patients as applied to the general population is ineffective from the perspective of both cost and survival benefit. Cancer screening in dialysis patients is therefore best provided in an individual patient-focused manner. The occurrence, diagnosis, and treatment of cancer as well as issues related to cancer screening in dialysis patients are discussed.

Renal cystic diseases: diverse phenotypes converge on the cilium/centrosome complex

Inherited renal cystic diseases constitute an important set of single-gene disorders that frequently progress to end stage renal disease (ESRD). Transmitted as autosomal dominant, autosomal recessive, or X-linked traits, renal cystic diseases are phenotypically diverse with respect to age at onset, rate of disease progression, and associated extra-renal manifestations. These disorders involve defects in a set of gene products commonly referred to as cystoproteins that, while functionally distinct, appear to co-localize, at least in part, with the cilia/centrosome complex. Therefore, investigations are increasingly focused on the role of this complex in the pathogenesis of renal cystic disease. Sorting out the functional relationship between these cystoproteins and the cilia/centrosome complex will undoubtedly provide a better understanding of renal cystic disease pathogenesis and, potentially, identify new targets for therapeutic intervention.

Diagnostic Approach in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common Mendelian disorder of the kidney and affects all racial groups worldwide. It is characterized by focal development of renal and extrarenal cysts in an age-dependent manner. Typically, only a few renal cysts are detected in most affected individuals before 30 yr of age. However, by the fifth decade of life, hundreds to thousands of renal cysts will be found in the majority of patients. ADPKD is genetically heterogeneous. Mutations of two genes, PKD1 and PKD2, account for approximately 85 and 15% of cases, respectively. Although the clinical manifestations of these two genotypes overlap completely, patients with PKD1 have much more severe renal disease compared with those with PKD2, as evidenced by their ESRD occurring approximately 15 yr earlier. Renal ultrasonography commonly is used for the assessment of ADPKD, and age-dependent ultrasound diagnostic criteria with high sensitivity and specificity have been established for individuals who are born with 50% risk for PKD1. Although these diagnostic criteria are used widely for genetic counseling and for the evaluation of at-risk individuals as living-related kidney donors to their affected relatives, their application to individuals who are at risk for PKD2 or have undefined genotype needs to be refined further. Molecular genetic testing is available for ADPKD and may be useful for evaluation of at-risk individuals with equivocal imaging results, younger at-risk individuals as a living-related kidney donor, and individuals with atypical or de novo renal cystic disease.

Polycystic disease of the liver

Autosomal dominant polycystic disease is genetically heterogeneous with mutations in two distinct genes predisposing to the combination of renal and liver cysts (AD-PKD1 and AD-PKD2) and mutations in a third gene yielding isolated liver cysts (the polycystic liver disease gene). Transcription and translation of the PKD1 gene produces polycystin-1, an integral membrane protein that may serve as an extracellular receptor. Mutations occur throughout the PKD1 gene, but more severe disease is associated with N-terminal mutations. The PKD2 gene product, polycystin-2, is an integral membrane protein with molecular characteristics of a calcium-permeant cation channel. Mutations occur throughout the PKD2 gene, and severity of disease may vary with site of mutation in PKD2 and the functional consequence on the resultant polycystin-2 protein. Polycystic liver disease is genetically linked to protein kinase C substrate 80K-H (PRKCSH). The PRKCSH gene encodes hepatocystin, a protein that moderates glycosylation and fibroblast growth factor receptor signaling. More prominent in women, hepatic cysts emerge after the onset of puberty and dramatically increase in number and size through the child-bearing years of early and middle adult life. Although liver failure or complications of advanced liver disease are rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Interventional and surgical options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Polycystic disease of the liver

Autosomal dominant polycystic disease is genetically heterogeneous with mutations in two distinct genes predisposing to the combination of renal and liver cysts (AD-PKD1 and AD-PKD2) and mutations in a third gene yielding isolated liver cysts (the polycystic liver disease gene). Transcription and translation of the PKD1 gene produces polycystin-1, an integral membrane protein that may serve as an extracellular receptor. Mutations occur throughout the PKD1 gene, but more severe disease is associated with N-terminal mutations. The PKD2 gene product, polycystin-2, is an integral membrane protein with molecular characteristics of a calcium-permeant cation channel. Mutations occur throughout the PKD2 gene, and severity of disease may vary with site of mutation in PKD2 and the functional consequence on the resultant polycystin-2 protein. Polycystic liver disease is genetically linked to protein kinase C substrate 80K-H (PRKCSH). The PRKCSH gene encodes hepatocystin, a protein that moderates glycosylation and fibroblast growth factor receptor signaling. More prominent in women, hepatic cysts emerge after the onset of puberty and dramatically increase in number and size through the child-bearing years of early and middle adult life. Although liver failure or complications of advanced liver disease are rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Interventional and surgical options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Adrenal insufficiency due to isolated adrenocorticotropin deficiency complicated by autosomal recessive polycystic kidney disease

We describe a 29-old-year Japanese man with autosomal recessive polycystic kidney disease who was frequently hypoglycemic. Insulinoma as a cause of hypoglycemia was denied because the ratio of plasma immunoreactive insulin to glucose was low. Adrenal insufficiency was diagnosed because of the low urinary excretion of 17-hydroxycorticosteroids, and both blunted responses of plasma cortisol to an intravenous injection of adrenocorticotropin and of plasma adrenocorticotropin to an intravenous injection of human corticotropin releasing hormone were observed, although basal plasma concentrations of cortisol and adrenocorticotropin were normal. The elusion profile of plasma sample from our patient chromatographed on a Sephadex G-75 column showed two peaks of (1-39)-ACTH and beta-lipotropin, with no evidence of high molecular weight form of ACTH. The plasma concentrations of thyroid stimulating hormone and growth hormone were within the normal range. These findings indicated that this patient with autosomal recessive polycystic kidney disease was associated with adrenal insufficiency due to isolated adrenocorticotropin deficiency.

Molecular pathology and genetics of congenital hepatorenal fibrocystic syndromes

The hepatorenal fibrocystic (HRFC) syndromes are a heterogeneous group of severe monogenic conditions that may be detected before birth. Commonly, HRFC syndromes present in the neonatal and paediatric age, with consistent developmental abnormalities mostly involving the liver and kidney. The changes include the proliferation and dilatation of epithelial ducts in these tissues with abnormal deposition of extracellular matrix. In this review, we examine the clinical features and differential diagnoses of this group of syndromes, including autosomal recessive polycystic kidney disease (ARPKD), juvenile nephronophthisis (NPHP), Meckel-Gruber syndrome (MKS), Bardet-Biedl syndrome (BBS), and Jeune asphyxiating thoracic dystrophy (JATD). Extrahepatic manifestations include mostly bone and central nervous system abnormalities, dysmorphic features, and developmental delay. Previously, it has been suggested that ARPKD, JATD, and Ellis-van Creveld syndrome (EvC) may arise from defects in differentiation in a common developmental pathway. We review recent molecular advances in the recessive HRFC syndromes and discuss this hypothesis.

Recurrent fetal loss associated with bilineal inheritance of type 1 autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a common Mendelian disorder that affects approximately 1 in 500 to 1,000 live births. Mutations in one of two genes, PKD1 and PKD2, account for the disease in most ADPKD families. Despite the relative high frequency of PKD1 mutant alleles, compound heterozygotes or diseased homozygotes have not been described.

METHODS AND RESULTS

We report a family with type 1 ADPKD in which the marriage between affected first-degree cousins resulted in two live-born heterozygous offspring and two fetuses lost in late pregnancy. Genetic analysis with PKD1 and PKD2 flanking markers showed that this family is PKD1 linked (z(max) = 1.66 and -2.54 at thetas = 0.0 for intragenic markers for PKD1 [ie, KG8] and PKD2 [ie, SPP1], respectively).

CONCLUSION

Given a 25% chance for mutant homozygosity in the offspring of this family, our findings suggest that homozygosity of PKD1 mutations in humans is embryonically lethal, as recently documented in Pkd1 knockout mice.