Curcumin Therapy to Treat Vascular Dysfunction in Children and Young Adults with ADPKD: A Randomized Controlled Trial.

BACKGROUND AND OBJECTIVES: Clinical manifestations of autosomal dominant polycystic kidney disease (ADPKD), including evidence of vascular dysfunction, can begin in childhood. Curcumin is a polyphenol found in turmeric that reduces vascular dysfunction in rodent models and humans without ADPKD. It also slows kidney cystic progression in a murine model of ADPKD. We hypothesized that oral curcumin therapy would reduce vascular endothelial dysfunction and arterial stiffness in children/young adults with ADPKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In a randomized, placebo-controlled, double-blind trial, 68 children/young adults 6-25 years of age with ADPKD and eGFR>80 ml/min per 1.73 m2 were randomized to either curcumin supplementation (25 mg/kg body weight per day) or placebo administered in powder form for 12 months. The coprimary outcomes were brachial artery flow-mediated dilation and aortic pulse-wave velocity. We also assessed change in circulating/urine biomarkers of oxidative stress/inflammation and kidney growth (height-adjusted total kidney volume) by magnetic resonance imaging. In a subgroup of participants ≥18 years, vascular oxidative stress was measured as the change in brachial artery flow-mediated dilation following an acute infusion of ascorbic acid. RESULTS: Enrolled participants were 18±5 (mean ± SD) years, 54% were girls, baseline brachial artery flow-mediated dilation was 9.3±4.1% change, and baseline aortic pulse-wave velocity was 512±94 cm/s. Fifty-seven participants completed the trial. Neither coprimary end point changed with curcumin (estimated change [95% confidence interval] for brachial artery flow-mediated dilation [percentage change]: curcumin: 1.14; 95% confidence interval, -0.84 to 3.13; placebo: 0.33; 95% confidence interval, -1.34 to 2.00; estimated difference for change: 0.81; 95% confidence interval, -1.21 to 2.84; P=0.48; aortic pulse-wave velocity [centimeters per second]: curcumin: 0.6; 95% confidence interval, -25.7 to 26.9; placebo: 6.5; 95% confidence interval, -20.4 to 33.5; estimated difference for change: -5.9; 95% confidence interval, -35.8 to 24.0; P=0.67; intent to treat). There was no curcumin-specific reduction in vascular oxidative stress or changes in mechanistic biomarkers. Height-adjusted total kidney volume also did not change as compared with placebo. CONCLUSIONS: Curcumin supplementation does not improve vascular function or slow kidney growth in children/young adults with ADPKD. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Curcumin Therapy to Treat Vascular Dysfunction in Children and Young Adults with ADPKD, NCT02494141. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2022_02_07_CJN08950621.mp3.

α-lipoic acid in patients with autosomal dominant polycystic kidney disease.

OBJECTIVES: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease characterized by multiple and bilateral cystic dilation of renal tubules. Hypertension, endothelial dysfunction, systemic inflammation, and accelerated atherosclerosis are alterations found at a very early stage of the disease and are responsible for increasing both cardiovascular risks and progression toward end-stage renal disease. The aim of the study was to evaluate the effects of the use of 1.6 g α-lipoic acid (ALA) daily for 3 and 6 on the main markers of systemic inflammation, endothelial dysfunction, and atherosclerosis, as well as on nutritional, cardiovascular, and psychocognitive parameters, in ADPKD patients with CKD stage G2/G3 Kidney Disease Improving Global Outcomes chronic kidney disease (KDIGO) compared to controls. METHODS: This was a controlled, longitudinal, prospective, interventional study with 59 patients with ADPKD. Of the patients, 33 were treated with ALA (1.6 g/d) for 6 mo and 26 were controls. Clinical, laboratory (inflammation and metabolic indexes), instrumental parameters (intima media thickness (IMT), renal resistive index (RRI), flow-mediated dilation (FMD), ankle-brachial index (ABI), and psycho-cognitive tests (Mini-Mental State Examination [MMSE], Hamilton Depression Rating Scale [HAM-D], Beck Depression Inventory-II [BDI-II]) were evaluated at baseline (T0), 3 mo (T1), and 6 mo (T2). RESULTS: Patients treated with ALA at T1 and T2 showed a significant reduction in serum glucose, insulin, homeostatic model assessment-insulin resistance, and serum uric acid (P = 0.013, P = 0.002, P = 0.002, P <0.001; respectively) and significantly higher values of base excess (P < 0.001), compared with the control group. Moreover, the results showed a significant increase in bicarbonates (P = 0.009) and FMD (P < 0.001), and a significant reduction of C-reactive protein (P <0.001) and RRI (P = 0.013). On the other hand, we did not assess a significant difference in IMT and ABI at T1 and T2. Psychocognitive tests (BDI-II, HAM-D, and MMSE) were significantly improved (P = 0.007, P < 0.001, P < 0.001; respectively) in patients treated with ALA for 6 mo compared with the control group. A significant difference in nicotinamide adenine dinucleotide phosphate oxidase 2 concentrations was observed between T0 and T2 only in ADPKD patients treated with ALA (P = 0.039, P = 0.039; respectively), although we did not find a significant difference in interleukin-6, interleukin -1ß, and tumor necrosis factor-α concentrations in either group. CONCLUSIONS: We suggest an early and careful monitoring of traditional and non-traditional cardiovascular risk factors in patients with ADPKD. Moreover, we suggest the use of ALA, an anti-inflammatory and antioxidant nutraceutical with few side effects. Additionally, it is important to evaluate the cognitive abilities, psychological health, and quality of life of patients with ADPKD, especially at the early stage of disease.

Renal Reabsorption of Folates: Pharmacological and Toxicological Snapshots.

Folates are water-soluble B9 vitamins that serve as one-carbon donors in the de novo synthesis of thymidylate and purines, and in the conversion of homocysteine to methionine. Due to their key roles in nucleic acid synthesis and in DNA methylation, inhibiting the folate pathway is still one of the most efficient approaches for the treatment of several tumors. Methotrexate and pemetrexed are the most prescribed antifolates and are mainly used in the treatment of acute myeloid leukemia, osteosarcoma, and lung cancers. Normal levels of folates in the blood are maintained not only by proper dietary intake and intestinal absorption, but also by an efficient renal reabsorption that seems to be primarily mediated by the glycosylphosphatidylinositol- (GPI) anchored protein folate receptor α (FRα), which is highly expressed at the brush-border membrane of proximal tubule cells. Folate deficiency due to malnutrition, impaired intestinal absorption or increased urinary elimination is associated with severe hematological and neurological deficits. This review describes the role of the kidneys in folate homeostasis, the molecular basis of folate handling by the kidneys, and the use of high dose folic acid as a model of acute kidney injury. Finally, we provide an overview on the development of folate-based compounds and their possible therapeutic potential and toxicological ramifications.

Comparison of Different Selection Strategies for Tolvaptan Eligibility among Autosomal Dominant Polycystic Kidney Disease Patients.

BACKGROUND: Tolvaptan can slow down renal function decline in autosomal dominant polycystic kidney disease (-ADPKD). While there is consensus across international recommendations that the drug should only be used in patients with high risk of rapid progression, identification criteria for rapid progression vary. Here, we investigated different assessment strategies using a real-life ADPKD cohort. METHODS: Observational retrospective cohort analysis. The study included 131 ADPKD patients aged 19-78 years who were referred to the Hannover Medical School outpatient clinic for evaluation of tolvaptan treatment. Six different assessment strategies for tolvaptan eligibility were tested for each patient. Comparative analysis for different assessments was performed in the total study population, the subpopulation with available computed tomography/magnetic resonance imaging data, and the genotyped subpopulation. RESULTS: Comparing 6 assessment strategies revealed strong variations in the individual selection processes resulting in treatment recommendations for 14.5-64.9% of patients. The highest patient number was selected by the Scottish and the lowest by the Japanese approach. Few patients had positive recommendations by all 6 systems, but strong congruency was observed between the Scottish, U.K. and Canadian patient selection. The lowest number of overlapping patients was found between the Japanese and the ERA-EDTA selection. Important discrepancies were also found between the ERA-EDTA and the U.S. system due to different emphases on parameters of kidney function versus kidney volume. Limitations of the study included the restricted sample size, heterogeneity in parameter availability and lack of outcome data. CONCLUSIONS: The study draws attention to important discrepancies between different decision algorithms for tolvaptan eligibility in ADPKD patients.

Yinang formulation versus placebo granules as a treatment for chronic kidney disease stages III-IV in patients with autosomal dominant polycystic kidney disease: study protocol for a double-blind placebo-controlled randomized clinical trial.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common potentially life-threatening inherited kidney diseases. It is the fourth most common cause of end-stage renal disease requiring renal replacement therapy. There are few management options for controlling disease progression. Hence, identification of alternative treatments for patients is important. The Chinese herbal yinang formulation (YNF), which is derived from a Chinese patent medicine, appears to have a satisfactory effect in treating ADPKD. Because a considerable proportion of ADPKD patients presenting with chronic kidney disease (CKD) stages III-IV are diagnosed with the spleen, kidney deficiency, and blood stasis syndrome according to the diagnostic criteria of traditional Chinese medicine (TCM), we hypothesize that YNF may be a complementary drug for ADPKD patients with the corresponding syndrome. Therefore, we have designed a strict clinical trial to evaluate the safety and efficacy of YNF for ADPKD patients with CKD stages III-IV exhibiting the TCM syndrome of spleen, kidney deficiency, and blood stasis. METHODS/DESIGN: This is a multi-center prospective double-blind randomized controlled trial. The total target sample size is planned to be 72 participants, with a balanced treatment allocation (1:1). The experimental intervention will be YNF plus conventional therapy and the control intervention will be a placebo plus conventional therapy for 24 weeks. An additional 24 weeks of follow-up will be conducted after treatment completion. The primary outcome will be the estimated glomerular filtration rate (eGFR). Changes in total kidney volume (TKV), serum creatinine (Scr), blood urea nitrogen (BUN), TCM symptoms, and pain will be the secondary outcomes. Adverse events (AEs) will be monitored throughout the trial. DISCUSSION: This study will be the first placebo-controlled randomized controlled trial to assess whether YNF plus conventional therapy has a beneficial effect on eGFR, TKV, Scr, and BUN, and whether it can alleviate TCM clinical symptoms, reduce ADPKD-related pain, and reduce the frequency of AEs for ADPKD patients with CKD stages III-IV with the spleen, kidney deficiency, and blood stasis syndrome. The results of this trial may provide an evidence-based recommendation for clinicians. TRIAL REGISTRATION: Chinese Clinical Trials Register, ChiCTR-INR-16009914 . Registered on 18 November 2016.

Nutritional therapy in autosomal dominant polycystic kidney disease.

CKD-related nutritional therapy (NT) is a crucial cornerstone of CKD patients' treatment, but the role of NT has not been clearly investigated in autosomal dominant polycystic kidney disease (ADPKD). Several clinical studies have focused on new pharmacological approaches to delay cystic disease progression, but there are no data on dietary interventions in ADPKD patients. The aim of this paper is to analyze the evidence from the literature on the impact of five nutritional aspects (water, sodium, phosphorus, protein intake, and net acid load) in CKD-related ADPKD extrapolating-where information is unavailable-from what occurs in CKD non-ADPKD patients Sodium intake restriction could be useful in decreasing the growth rate of cysts. Although further evidence is needed, restriction of phosphorus and protein intake restriction represent cornerstones of the dietary support of renal non-ADPKD patients and common sense can guide their use. It could be also helpful to limit animal protein, increasing fruit and vegetables intake together with a full correction of metabolic acidosis. Finally, fluid intake may be recommended in the early stages of the disease, although it is not to be prescribed in the presence of moderate to severe reduction of renal function.

Long-term effect of coffee consumption on autosomal dominant polycystic kidneys disease progression: results from the Suisse ADPKD, a Prospective Longitudinal Cohort Study.

BACKGROUND: Previous in vitro experiments of human polycystic kidney disease (PKD) cells reported that caffeine is a risk factor for the promotion of cyst enlargement in patients with autosomal dominant PKD (ADPKD). The relentless progression of ADPKD inclines the majority of physicians to advocate minimization of caffeine consumption despite the absence of clinical data supporting such a recommendation so far. This is the first clinical study to assess prospectively the association between coffee consumption and disease progression in a longitudinal ADPKD cohort. METHODS: Information on coffee consumption and disease progression was collected at each follow-up visit using standardized measurement methods. The main model for the outcomes, kidney size (height-adjusted total kidney volume, htTKV) and kidney function (estimated glomerular filtration rate, eGFR), was a linear mixed model. Patients entered the on-going Swiss ADPKD study between 2006 and June 2014 and had at least 1 visit every year. The sample size of the study population was 151 with a median follow-up of 4 visits per patient and a median follow-up time of 4.38 years. RESULTS: After multivariate adjustment for age, smoking, hypertension, sex, body mass index and an interaction term (coffee*visit), coffee drinkers did not have a statistically significantly different kidney size compared to non-coffee drinkers (difference of -33.03 cm3 height adjusted TKV, 95% confidence interval (CI) from -72.41 to 6.34, p = 0.10). After the same adjustment, there was no statistically significant difference in eGFR between coffee and non-coffee drinkers (2.03 ml/min/1.73 m2, 95% CI from -0.31 to 4.31, p = 0.089). CONCLUSION: Data derived from our prospective longitudinal study do not confirm that drinking coffee is a risk factor for ADPKD progression.

Nutraceutical for Autosomal Dominant Polycystic Kidney Disease Therapy.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disorder caused by mutations of either PKD1 or PKD2 gene. Cyst formation initiates from a combination of abnormal cell proliferation along with enhanced fluid secretion. ADPKD is characterized by the progressive enlargement of cysts which destroy the renal parenchymal cells, resulting in renal failure. Currently, there is no effective treatment for this disease. Interestingly, several relevant therapeutic effects of herbal medicine relevant to pathogenic process of ADPKD have urged the researchers to search for potential candidate herb as nutraceutical for ADPKD therapy. Up to now, several natural compounds, such as triptolide, curcumin, ginkolide B, and steviol (stevia extract) have been shown to be able to retard cyst progression in ADPKD. The detailed mechanism of these compounds showed that triptolide enhanced calcium restoration, curcumin inhibited ERK & p-STAT3 pathways, ginkolide B inhibited Ras/MAPK pathway, and steviol activated AMPK, which inhibited CFTR channel and mTOR pathway in cell and mouse models of PKD. In addition, they are currently inpreclinical and clinical studies, respectively. This review focuses on the pathophysiology of ADPKD and the recent therapeutic approaches, especially a potential use of nutraceutical for the treatment of autosomal dominant polycystic kidney disease.

Analysis of data from the ERA-EDTA Registry indicates that conventional treatments for chronic kidney disease do not reduce the need for renal replacement therapy in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a major cause of end-stage kidney failure, but is often identified early and therefore amenable to timely treatment. Interventions known to postpone the need for renal replacement therapy (RRT) in non-ADPKD patients have also been tested in ADPKD patients, but with inconclusive results. To help resolve this we determined changes in RRT incidence rates as an indicator for increasing effective renoprotection over time in ADPKD. We analyzed data from the European Renal Association-European Dialyses and Transplant Association Registry on 315,444 patients starting RRT in 12 European countries between 1991 and 2010, grouped into four 5-year periods. Of them, 20,596 were due to ADPKD. Between the first and last period the mean age at onset of RRT increased from 56.6 to 58.0 years. The age- and gender-adjusted incidence rate of RRT for ADPKD increased slightly over the four periods from 7.6 to 8.3 per million population. No change over time was found in the incidence of RRT for ADPKD up to age 50, whereas in recent time periods the incidence in patients above the age of 70 clearly increased. Among countries there was a significant positive association between RRT take-on rates for non-ADPKD kidney disease and ADPKD. Thus, the increased age at onset of RRT is most likely due to an increased access for elderly ADPKD patients or lower competing risk prior to the start of RRT rather than the consequence of effective emerging renoprotective treatments for ADPKD.

Pharmacological management of polycystic kidney disease.

INTRODUCTION: Autosomal-dominant polycystic kidney disease (ADPKD) represents a therapeutic challenge as effective treatment to retard the growth of cysts in the kidneys and the liver has not been available despite decades of intense basic and clinical research. AREAS COVERED: Several clinical trials have been performed in recent years to study the effect of diverse drugs on the growth of renal and hepatic cysts, and on functional deterioration of the glomerular filtration rate. The drug classes that have been tested in randomized clinical trials include the mammalian target of rapamycin (mTOR) inhibitors, sirolimus and everolimus, the somatostatin analogues (octreotide, lanreotide, pasireotide), and most recently, the vasopressin V2 receptor antagonist, tolvaptan. The results with the mTOR inhibitors were disappointing, but more encouraging with the somatostatin analogues and with tolvaptan. Additional drugs are being tested, which include among others, the SRC-ABL tyrosine kinase inhibitor, bosutinib, and the traditional Chinese herbal medication, triptolide. Additional therapeutic strategies to retard cyst growth aim at blood pressure control via inhibition of the renin-angiotensin system and the sympathetic nervous system. EXPERT OPINION: Given the accumulated knowledge, it is currently uncertain whether drugs will become available in the near future to significantly change the course of the relentlessly progressing polycystic kidney disease.

A defect in vasopressin secretion in autosomal dominant polycystic kidney disease.

A nephrogenic defect in urine concentration is well established in patients with polycystic kidney disease, but Ho et al. report a defect in the increase of plasma vasopressin in response to dehydration. On a cellular level, transient receptor potential channels responsible for osmoperception could interact with TRPPs encoded by the polycystic genes PKD1 and PKD2.

Autosomal dominant polycystic kidney disease is associated with central and nephrogenic defects in osmoregulation.

Autosomal dominant polycystic kidney disease (ADPKD) is associated with a urine-concentrating defect attributed to renal cystic changes. As PKD genes are expressed in the brain, altered central release of arginine vasopressin could also play a role. In order to help determine this we measured central and nephrogenic components of osmoregulation in 10 adults and 10 children with ADPKD, all with normal renal function, and compared them to 20 age- and gender-matched controls. Overnight water deprivation caused a lower rise in urine osmolality in the patients with ADPKD than controls, reflecting an impaired release of vasopressin and a peripheral defect in the patients. The reactivity of plasma vasopressin to water deprivation, as found in controls, was blunted in the patients with the latter showing lower urine osmolality for the same range of plasma vasopressin. The maximal urine osmolality correlated negatively with total kidney volume. Defective osmoregulation was confirmed in the children with ADPKD but was unrelated to number of renal cysts or kidney size. Thus, patients with ADPKD have an early defect in osmoregulation, with a blunted release of arginine vasopressin. This reflects expression of polycystins in hypothalamic nuclei that synthesize vasopressin, and this should be considered when evaluating treatments targeting the vasopressin pathway in ADPKD.

Volumetric analysis of MRI data monitoring the treatment of polycystic kidney disease in a mouse model.

OBJECT: The human condition autosomal dominant polycystic kidney disease (ADPKD) is characterized by the growth of cysts in the kidneys that increase renal volume and lead to kidney failure. Mice studies are performed for treatment development monitored with imaging. The analysis of the imaging data is typically manual, which is costly and potentially biased. This paper presents a reliable and reproducible method for the automated segmentation of polycystic mouse kidneys. MATERIALS AND METHODS: Treated and untreated mice have been imaged longitudinally with high field anatomic MRI. The region of interest (ROI) of the kidneys in the images is identified and restored for artifacts. It is then analyzed statistically and geometric models are estimated for each kidney. The statistical and geometric information are provided to the graph cuts algorithm that delineates the kidneys. RESULTS: The accuracy of the analysis has been demonstrated by showing consistency with results obtained with previous methods as well as by comparing with manual segmentations. CONCLUSION: The method developed can accelerate and improve the accuracy of kidney volumetry in preclinical treatment trials for ADPKD.

Evaluation and management of pain in autosomal dominant polycystic kidney disease.

Transient episodes of pain are common in autosomal dominant polycystic kidney disease (ADPKD). A small fraction of patients have disabling chronic pain. In this review, we discuss the etiologies of pain in ADPKD; review how ADPKD patients should be assessed; and discuss medical, surgical, and other management options.

The effect of eicosapentaenoic acid on renal function and volume in patients with ADPKD.

BACKGROUND: Soy protein ameliorates rat polycystic kidney disease with concomitant renal enrichment of omega3-polyunsaturated fatty acids. A study was conducted to examine the effects of eicosapentaenoic acids (EPA) on renal volume and function in patients with autosomal dominant polycystic kidney disease (ADPKD). METHODS: Non-azotemic patients were randomized to either a control group (n = 20) or an EPA group (n = 21). EPA capsules (2.4 g/day) were administered in the EPA group for 2 years. Twenty-four hours of urine was collected for the creatinine clearance (Ccr) measurement every year. At baseline and 24 months, fatty acid compositions in erythrocytes were measured and computerized tomographies were obtained for calculation of renal volume by the modified ellipsoid and volumetric methods. RESULTS: In the EPA group, the EPA concentration (1.80 +/- 0.99 versus 4.40 +/- 1.79 area%, P < 0.001) and the omega3/omega6 ratio in the erythrocyte increased, but docosahexaenoic acid (DHA) (6.76 +/- 1.19 versus 5.64 +/- 1.45 area%, P < 0.010) concentration decreased. Ccr decreased by 8.5 +/- 9.5 and 9.0 +/- 13.0 ml/min/1.73 m(2)/2 years in the control and EPA groups, respectively (NS). The increases in renal volume calculated by either method were not significantly different between the two groups. CONCLUSIONS: A beneficial effect of EPA on renal function and kidney volume in ADPKD patients could not be confirmed in the present study. Administration of EPA with DHA supplementation and/or longer intervention might be necessary to demonstrate preventive effects of omega3-polyunsaturated fatty acids on progression of ADPKD.

Expression of the polycystin-1 C-terminal cytoplasmic tail increases Cl channel activity in Xenopus oocytes.

Expression of the polycystin-1 C-terminal cytoplasmic tail increases Cl(-) channel activity in Xenopus oocytes. Background. Cyst expansion in autosomal-dominant polycystic kidney disease (ADPKD) is characterized by active Cl(-) secretion in excess of solute reabsorption. However, the connections between elevated epithelial Cl(-) secretion and loss-of-function or dysregulation of either ADPKD gene polycystin-1 (PC1) or polycystin-2 (PC2) remain little understood. Methods. Cl(-) transport in Xenopus oocytes expressing the CD16.7-PKD1 (115-226) fusion protein containing the final 112 amino acid (aa) of the PC1 C-terminal cytoplasmic tail, or in oocytes expressing related PC1 fusion protein mutants, was studied by isotopic flux, two-electrode voltage clamp, and outside-out patch clamp recording. Results. Expression in oocytes of CD16.7-PKD1 (115-226) increased rates of both influx and efflux of (36)Cl(-), whereas CD16.7-PKD1 (1-92) containing the initial 92 aa of the PC1 C-terminal cytoplasmic tail was inactive. The increased Cl(-) transport resembled CD16.7-PKD1 (115-226)-stimulated cation current in its sensitivity to ADPKD-associated missense mutations, to mutations in phosphorylation sites, and to mutations within or encroaching upon the PC1 coiled-coil domain, as well as in its partial suppression by coexpressed PC2. The NS3623- and 4, 4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS)-sensitive (36)Cl(-) flux was not blocked by injected ethyleneglycol tetraacetate (EGTA) or by the cation channel inhibitor SKF96365, and was stimulated by the cation channel inhibitor La(3+), suggesting that CD16.7-PKD1 (115-226)-associated cation conductance was not required for (36)CI(-) flux activation. Outside-out patches from oocytes expressing CD16.7-PKD1 (115-226) also exhibited increased NS3623-sensitive Cl(-) current. Conclusion. These data show that CD16.7-PKD1 (115-226) activates Cl(-) channels in the Xenopus oocyte plasma membrane in parallel with, but not secondary to, activation of Ca(2+)-permeable cation channels.

Pain management in polycystic kidney disease.

Pain is a common complaint in patients with autosomal-dominant polycystic kidney disease, and a systematic approach is needed to differentiate the etiology of the pain and define an approach to management. A thorough history is the best clue to the multifactorial causes of the pain, superimposed upon an understanding of the complex innervation network that supplies the kidneys. The appropriate use of diagnostic radiology (especially MRI) will assist in differentiating the mechanical low back pain caused by cyst enlargement, cyst rupture and cyst infection. Also, the increased incidence of uric acid nephrolithiasis as a factor in producing renal colic must be considered when evaluating acute pain in the population at risk. MRI is not a good technique to detect renal calculi, a frequent cause of pain in polycystic kidney disease. If stone disease is a possibility, then abdominal CT scan and/or ultrasound should be the method of radiologic investigation. Pain management is generally not approached in a systematic way in clinical practice because most physicians lack training in the principles of pain management. The first impulse to give narcotics for pain relief must be avoided. Since chronic pain cannot be "cured," an approach must include techniques that allow the patient to adapt to chronic pain so as to limit interference with their life style. A detailed stepwise approach for acute and chronic pain strategies for the patient with autosomal dominant polycystic kidney disease is outlined.

Modification of disease progression in rats with inherited polycystic kidney disease.

The most common inherited form of human polycystic kidney disease (PKD), autosomal dominant PKD (ADPKD), is a leading cause of chronic renal failure, but has a variable clinical presentation, with end-stage renal disease occurring in only 25% to 75%. Several findings are consistent with the idea that factors in addition to the primary mutation can affect the progression of cystic change and chronic renal failure in PKD. Epithelial cell proliferation is a central element in the pathogenesis of renal cysts. We postulated that the superimposition of a growth-promoting stimulus might promote more intense proliferation of cystic epithelial cells in inherited cystic disease. To study this, we subjected Han:SPRD rats, with a form of ADPKD that resembles human ADPKD, from 4 until 10 weeks of age to diets designed to promote tubule cell growth. The diets included supplemental NH4Cl (280 mmol/L in drinking water), limited dietary K+ (0.016% of diet; control diet was 1.1% K+), and increased dietary protein (50%; control diet was 23% protein). Treatments designed to promote cell growth caused more aggressive PKD in males and females, worsened azotemia in males, and resulted in azotemia in females (which normally develop PKD but not azotemia at the ages studied). NH4Cl, K+ restriction, and increased dietary protein each caused greater kidney enlargement in males (kidney weight/body weight ratios increased by 35%, 78%, and 105%, respectively) and worsened azotemia in males (serum urea nitrogen values increased by 63%, 514%, and 224%, respectively); in contrast, decreased dietary protein (4%) caused less severe PKD in males (kidney weight/body weight ratios decreased by 43%) and lessened azotemia in males (serum urea nitrogen values decreased by 49%). Similarly, NH4Cl and K+ restriction caused greater kidney enlargement in females (kidney weight/body weight ratios increased by 206% and 203%, respectively) and caused azotemia in females (serum urea nitrogen values increased by 177% and 430%, respectively). On the basis of these results, we conclude that growth-promoting stimuli can alter the expression of hereditary renal cystic disease. These findings demonstrate that the progression of hereditary renal cystic disease can be altered by factors in addition to the primary genetic defect.

Dietary protein restriction, blood pressure control, and the progression of polycystic kidney disease. Modification of Diet in Renal Disease Study Group.

In the Modification of Diet in Renal Disease Study, a follow-up (mean, 2.2 yr) of 200 study participants with autosomal dominant polycystic kidney disease (ADPKD) was conducted to determine the effect of lowering protein intake and blood pressure on the rate of decline in GFR. The rate of decline was faster in participants with ADPKD than in persons with other diagnoses, reflecting, in part, faster disease progression in the ADPKD group. Baseline characteristics that predicted a faster rate of decline in GFR in persons with ADPKD were greater serum creatinine (independent of GFR), greater urinary protein excretion, higher mean arterial pressure (MAP), and younger age. In patients with initial GFR values between 25 and 55 mL/min per 1.73 m2, neither assignment to a low-protein diet group nor assignment to a low blood pressure group significantly reduced the rate of decline of GFR in ADPKD participants. Similarly, the decline in GFR was not related to achieved protein intake or MAP. In participants with GFR values between 13 and 24 mL/min per 1.73 m2, assignment to the low MAP group led to a somewhat more rapid decline in GFR. However, the more rapid decline in GFR did not appear to be due to a detrimental effect of low blood pressure or the antihypertensive agents used to reach the low blood pressure goal. Lower protein intake, but not prescription of the keto acid-amino acid supplement, was marginally associated with a slower progression of renal disease.