To examine the impact of renal failure on the composition of gut microbiota we are studying patients with renal failure due to polycystic kidney disease (PKD). PKD is the fourth leading cause of kidney failure, and is the most common genetic kidney disease. Compared to patients with renal failure due to diabetic nephropathy, hypertension, and glomerulonephritis, patients with PKD have virtually no major co-morbid medical conditions or associated medical interventions (i.e. antimicrobial or anti-inflammatory therapies) that could potentially alter the gut microbiota, and confound the interpretation of data.