Macropuncture study of polycystic disease in adult human kidneys

Solute composition, volume, and hydrostatic pressure were measured in cysts from eight patients with the adult form of polycystic kidney disease (PCKD). Five azotemic patients had elective nephrectomies in preparation for renal transplantation, two nonazotemic patients had their polycystic kidneys removed several weeks after a successful renal allograft, and one nonazotemic cadaver was inadvertently nephrectomized as a potential kidney donor. In all patients, the pattern of solute concentrations in cyst fluid segregated into two principal groups: Proximal cysts had sodium, potassium, chloride, hydrogen ion, creatinine, and urea values virtually equal to their respective sera, whereas distal cysts had sodium and chloride concentrations lower and potassium, hydrogen ion, creatinine, and urea concentrations greater than serum. In the two subjects who received renal allografts and were not azotemic, creatinine and urea concentrations in the proximal cysts reflected nonazotemic values, indicating redistribution of these solutes across proximal cyst walls after the extracellular fluid was normalized. By contrast, distal cysts maintained steep concentration gradients for creatinine and urea. Transmural hydrostatic pressures were similar in proximal and distal cysts and were not different from normal intratubular pressures. These studies provide strong support for the view that cysts are massively enlarged segments of nephrons and collecting tubules that qualitatively maintain their basic solute transport functions throughout the life of the patient.