Polycystic kidney disease patients on renal replacement therapy: data from the Catalan Renal Registry

Primary prevention of cardiovascular disease events with renin-angiotensin system blockade in autosomal dominant polycystic kidney disease dialysis patients: A nationwide cohort study

Although renin-angiotensin system (RAS) blockade has been shown to reduce cardiovascular disease (CVD) in the general population and high-risk subjects, their protective effect in autosomal dominant polycystic kidney disease (ADPKD) patients under dialysis was still unknown. By using the database from 1995 to 2008 Taiwan National Health Insurance Research Database (Registry for Catastrophic Illnesses), we included 387 ADPKD patients who received dialysis therapy, aged ≥ 18 year-old, and with no evidence of CVD events in 1997 and 1998. We utilized Cox proportional hazards regression analysis and propensity score matching to evaluate adjusted hazard ratios for all-cause mortality and CVD events in users (n=231) and nonusers (n = 156) of an angiotensin-converting enzymes inhibitor (ACEI) / angiotensin II receptor blocker (ARB) during the 12 years of follow-up. All study subjects were followed up for more than 3 months. There was no significant difference between the ACEI/ARB treatment group and the control group in incident CVD events except ischemic stroke and transient ischemic accident (TIA). The results remain similar between groups before and after propensity score matching. Moreover, there was no significant difference in outcomes between ACEI/ARB treatment over 50% of follow-up period and without ACEI/ARB treatment after propensity score matching. This nationwide cohort study failed to prove the protective effects of long-term ACEI or ARB on incident CVD events among APKD dialysis patients. Further larger scale, multicenter and randomized control trials are warranted to show the causal association.

Renal replacement therapy in ADPKD patients: a 25-year survey based on the Catalan registry

Background

Some 7-10% of patients on replacement renal therapy (RRT) are receiving it because of autosomal dominant polycystic kidney disease (ADPKD). The age at initiation of RRT is expected to increase over time.

Methods

Clinical data of 1,586 patients (7.9%) with ADPKD and 18,447 (92.1%) patients with other nephropathies were analysed from 1984 through 2009 (1984–1991, 1992–1999 and 2000–2009).

Results

The age at initiation of RRT remained stable over the three periods in the ADPKD group (56.7 ± 10.9 (mean ± SD) vs 57.5 ± 12.1 vs 57.8 ± 13.3 years), whereas it increased significantly in the non-ADPKD group (from 54.8 ± 16.8 to 63.9 ± 16.3 years, p < 0.001). The ratio of males to females was higher for non-ADPKD than for ADPKD patients (1.6–1.8 vs 1.1–1.2). The prevalence of diabetes was significantly lower in the ADPKD group (6.76% vs 11.89%, p < 0.001), as were most of the co-morbidities studied, with the exception of hypertension. The survival rate of the ADPKD patients on RRT was higher than that of the non-ADPKD patients (p < 0.001).

Conclusions

Over time neither changes in age nor alterations in male to female ratio have occurred among ADPKD patients who have started RRT, probably because of the impact of unmodifiable genetic factors in the absence of a specific treatment.

Altered expression pattern of polycystin-2 in acute and chronic renal tubular diseases

Polycystin-2 represents one of so far two proteins found to be mutated in patients with autosomal-dominant polycystic kidney disease. Evidence obtained from experiments carried out in cell lines and with native kidney tissue strongly suggests that polycystin-2 is located in the endoplasmic reticulum. In the kidney, polycystin-2 is highly expressed in cells of the distal and connecting tubules, where it is located in the basal compartment. It is not known whether the expression of polycystin-2 in the kidney changes or whether it can be manipulated under certain instances. Therefore, the distribution of polycystin-2 under conditions leading to acute and chronic renal failure was analyzed. During ischemic acute renal failure, which affects primarily the S3 segment of the proximal tubule, a pronounced upregulation of polycystin-2 and a predominantly combined homogeneous and punctate cytoplasmic distribution in damaged cells was observed. After thallium-induced acute injury to thick ascending limb cells, polycystin-2 staining assumed a chicken wire-like pattern in damaged cells. In the (cy/+) rat, a model for autosomal-dominant polycystic kidney disease in which cysts originate predominantly from the proximal tubule, polycystin-2 immunoreactivity was lost in some distal tubules. In kidneys from (pcy/pcy) mice, a model for autosomal-recessive polycystic kidney disease in which cyst formation primarily affects distal tubules and collecting ducts, a minor portion of cyst-lining cells cease to express polycystin-2, whereas in the remaining cells, polycystin-2 is retained in their basal compartment. Data show that the expression and cellular distribution of polycystin-2 in different kinds of renal injuries depends on the type of damage and on the nephron-specific response to the injury. After ischemia, polycystin-2 may be upregulated by the injured cells to protect themselves. It is unlikely that polycystin-2 plays a role in cyst formation in the (cy/+) rat and in the (pcy/pcy) mouse.

Impaired endocytosis may represent an obstacle to gene therapy in polycystic kidney disease

BACKGROUND

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease and a frequent cause of chronic renal failure. The cloning of the PKD1 and PKD2 genes, which are mutated in the great majority of patients with this disease, opens up the opportunity for somatic gene therapy by introduction of the wild-type gene or cDNA. Several publications have provided evidence, that many portions of the nephron and the collecting duct can form cysts, including the proximal tubule. Alterations in the proximal tubule may prevent the efficient endocytosis of filtered proteins and thus contribute to proteinuria, a frequent symptom in patients with polycystic kidney disease. At the same time this may also negatively affect various gene therapy strategies, since endocytosis is important for the uptake of foreign DNA at least under some circumstances. In the (cy/+) rat, a widely used animal model for ADPKD, cysts almost exclusively develop from proximal tubules, and we have therefore investigated whether proteinuria and defective endocytosis also occur in this model.

METHODS

Proteinuria was demonstrated by direct measurement and by protein gel electrophoresis of urines from 16 week-old (cy/+) rats. Endocytosis was investigated by injection of FITC-dextran and immunohistochemical staining with anti-ClC-5 and anti-megalin antibodies.

RESULTS

Similar to the observations made in ADPKD patients, proteinuria also develops in the (cy/+) rat. Using FITC-labeled dextran as an in vivo tracer for renal tubular endosomal function, we could show that portions of cyst-lining epithelia from proximal tubules have lost the ability to endocytose, which is necessary for the reabsorption of albumin and lower-molecular-weight proteins. By immunohistochemistry the expression of other proteins implicated in endocytosis, such as the chloride channel ClC-5 and the albumin receptor megalin, correlated well with the presence and absence of FITC-dextran in cyst wall epithelia.

CONCLUSION

These data indicate that proteinuria and albuminuria in the (cy/+) rat model for ADPKD are due to a loss of the endocytic machinery in epithelia of proximal tubular cysts. Such a defect may also reduce the efficacy of certain gene therapy protocols.

Rapid MR imaging detection of renal cysts: age-based standards

PURPOSE

To establish age-based standards for renal cysts depicted at magnetic resonance (MR) imaging and to compare these standards with existing standards for ultrasonography (US).

MATERIALS AND METHODS

Three radiologists reviewed subsecond T2-weighted single-shot fast spin-echo kidney MR imaging findings in 528 patients (248 men, 280 women) selected from consecutive abdominal MR studies without regard to clinical indication. Age, sex, and number and diameter of cysts were noted. Results were analyzed with nonparametric tests and were compared with published US results.

RESULTS

Men (mean, 2.0; 95% CI: 1.5, 2.5) had more renal cysts than women (mean, 1.2; 95% CI: 0.9, 1.5) (P < .001). Number and diameter of cysts increased with age (P < .001). Of 528 patients, 330 (62.5%) had at least one renal cyst, and 315 (59.7%) had cysts of 10 mm or less. MR imaging findings were comparable to published US criteria for type 1 autosomal dominant polycystic kidney disease (ADPKD) if only cysts larger than 1 cm were considered: Only one subject in the group of 18-29-year-old subjects had at least two renal cysts, and five of 493 subjects aged 30-59 years had at least two cysts in each kidney.

CONCLUSION

Compared with reported US results, MR imaging depicted an increased number of simple renal cysts in healthy individuals because of its increased sensitivity for cysts smaller than 1 cm. If only simple renal cysts larger than 1 cm are considered, US criteria for type 1 ADPKD can be applied to MR imaging.

Survival after end-stage renal disease in autosomal dominant polycystic kidney disease: contribution of extrarenal complications to mortality

Autosomal dominant polycystic kidney disease (ADPKD) accounts for 8% to 10% of patients with end-stage renal disease (ESRD) in the United States and Europe. Progressive expansion of multiple bilateral renal cysts leads to massive enlargement of the kidneys and progressive renal failure. Extrarenal manifestations of ADPKD, such as liver cysts, intracranial aneurysms, cardiac valvular disease, and perhaps diverticulosis, have been documented extensively in cross-sectional studies, but little is known about their natural history. It is thought that extrarenal aspects of ADPKD contribute to increased mortality, yet survival on dialysis of the ADPKD population surpasses that of the general dialysis population. To address this issue, we analyzed the relative risk and causes of death after ESRD in ADPKD versus nondiabetic controls using data from the United States Renal Data System. Relative risk of death from any cause, including the major extrarenal manifestations of ADPKD, was determined as a function of ESRD treatment modality (dialysis or transplantation). We found a lower total mortality rate in ADPKD ESRD patients compared with nondiabetic control ESRD patients (relative risk of death in ADPKD = 0.57; P < 0.001). Mortality rates of extrarenal complications except for polycystic liver disease were similar or lower in ADPKD patients than in nondiabetic controls. Mortality secondary to extrarenal complications was substantially lower than that secondary to cardiovascular or cerebrovascular disease.

Autosomal dominant polycystic kidney disease types 1 and 2: assessment of US sensitivity for diagnosis

PURPOSE

To estimate the sensitivity and specificity of ultrasonography (US) in the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) types 1 and 2, as compared with those of genetic linkage analysis.

MATERIALS AND METHODS

A renal US and DNA analysis for ADPKD was performed in 319 patients who were at risk, 161 of whom were younger than 30 years, from 54 families with ADPKD. The sensitivity of US for diagnosis was estimated by comparing the US results with genotypes inferred from linkage studies.

RESULTS

The sensitivity of US in individuals younger than 30 years who were at risk was 95% for ADPKD type 1 but only 67% for ADPKD type 2. The sensitivity of US for either ADPKD type 1 or ADPKD type 2 in individuals aged 30 years or older who were at risk was 100%. The overall sensitivity in individuals younger than 30 years was 93%. For both ADPKD types 1 and 2 in all patients, US demonstrated a sensitivity of 97%, a specificity of 100%, and an accuracy of 98%.

CONCLUSION

US is the first-line imaging technique that should be used in the diagnosis of ADPKD. The sensitivity in individuals aged 30 years or older is 100%, but if there is a clinical suspicion of ADPKD type 2 in individuals younger than 30 years, linkage analysis should also be considered.

Echocardiographic evaluation in patients with autosomal dominant polycystic kidney disease and end-stage renal disease

Cardiovascular abnormalities have been considered important extrarenal manifestations of autosomal dominant polycystic kidney disease (ADPKD). However, little is known about their prevalence in patients with ADPKD undergoing hemodialysis (HD). To investigate whether cardiac abnormalities are more prevalent in these patients, clinical and echocardiographic manifestations of cardiovascular disease were evaluated in a group of 32 patients with ADPKD and a matched control group of 32 patients without diabetes treated by chronic HD for more than 6 months. Predialysis systolic and diastolic blood pressure (BP), prevalence of hypertension, and number of patients requiring antihypertensive medications were lower in the ADPKD group than controls. There was no difference in the prevalence of cardiac events, including cardiac failure, ischemic heart disease, and arrhythmia. Systolic dysfunction, diastolic patterns, and left ventricular hypertrophy were similar in the two groups. In patients with ADPKD, simple regression analysis showed left ventricular mass (LVM) index was correlated with hemoglobin level and predialytic systolic and diastolic BPs. In multiple regression analysis, predialysis systolic BP was the only independent variable linked to LVM index. The prevalence of aortic, mitral, and tricuspid valve disease did not differ between groups. In conclusion, the occurrence of cardiovascular complications in patients with ADPKD is similar to that of HD patients with other primary renal diseases, although hypertension is less prevalent.

Autosomal dominant polycystic kidney disease with anticipation and Caroli's disease associated with a PKD1 mutation. Rapid communication

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal hereditary disorder. Clinical expression of ADPKD shows interfamilial and intrafamilial variability. We screened for mutations the 3' region of the PKD1 gene, from exon 43 to exon 46, in a family showing anticipation and Caroli's disease and have found a 28 base pairs deletion in exon 46 (12801del28) and a new DNA variant in exon 43 (12184 C to G conserving Ala 3991) segregating with the disease. The mutation should result in a protein 44 amino acids longer then the wild-type PKD1. This PKD1 mutation manifests as typical adult-onset disease in the father, but in the proband, a 26-year-old man, ADPKD was diagnosed as a newborn and was associated with Caroli's disease at the age of 18 years. A renal biopsy performed in childhood disclosed a predominance of glomerular cysts. Mutation 12801del28 is the first molecular defect associated with Caroli's disease and the PKD1 phenotype. The finding of the same mutation in two different members of the same family with different expression of the disease indicates that the phenotypic variation in ADPKD must be due to modifying factors that may radically affect the course of the disease.