Adult polycystic kidney disease: studies of the defect in urine concentration.

Adult polycystic kidney disease: Studies of the defect in urine concentration. Patients with adult polycystic kidney disease with and without renal insufficiency and some of their family members in whom cysts were not demonstrable by radiography underwent tests of maximal urine concentrating ability (U max ). Ten of the twelve family members without demonstrable cysts (Group I) had U max exceeding 900 mOsm/kg. Eleven of the 13 subjects with polycystic kidneys but without renal insufficiency (Group II) had U max below 700 mOsm/kg after 24 hours of dehydration and excess exogenous vasopressin. Patients with polycystic kidney and renal insufficiency (Group III) excreted urines of osmolalities which were only slightly higher than that of plasma after dehydration and vasopressin. The nature of the defect in U max was further characterized by examining the capacity to maximally concentrate the urine (T c H 2 O ) during conditions of increasing osmolar clearance (C Osm ) and the capacity to maximally dilute the urine (C H 2 O ) in the presence of increased delivery of sodium to the diluting site. Group II patients had varying inabilities to maximally concentrate the urine, while this function was uniformly abnormal in all patients in Group III. Nevertheless, all patients were able to elaborate a maximally dilute urine and to increase C H 2 O with increasing distal delivery. It is concluded that the defect in U max is not the result of diminished glomerular filtration rate nor a defect in sodium reabsorption in the ascending limb of Henle's loop. This defect, which is aggravated by increased osmotic load per nephron in Group III patients, may result from alterations in collecting duct function or medullary architecture due to the presence of cysts. Polykystose renale de l'adulte: Demonstration d'un defaut de concentration. Des malades adultes atteints de polykystose renale avec et sans insuffisance renale et quelques membres de leurs families chez lesquels des kystes n'etaient pas mis en evidence par la radiographie ont subi des epreuves de concentration urinaire maximale (Umax). Dix des douze membres d'une famille sans kystes demontrables (groupe I) avaient un Umax depassant 900 mOsm/kg. Onze des treize sujets ayant des reins polykystiques sans insuffisance renale (groupe II) avaient un Umax inferieur a 700 mOsm/kg apres 24 heures de deshydratation et sous exces de vasopressine exogene. Les malades ayant des reins polykystiques et une insuffisance renale (groupe III) excretaient des urines dont l'osmolalite etait a peine superieure a celle du plasma apres deshydratation et vasopressine. La nature du deficit de Umax a ete caracterisee par l'etude de la capacite maximale de concentrer l'urine dans des conditions de clearance osmolaire (Cosm) augmentee et de la capacite maximale de diluer l'urine (C H 2 O ) en presence d'une augmentation du debit de sodium au segment de dilution. Les malades du groupe II avaient un deficit variable de la concentration maximale de l'urine alors que cette fonction etait uniformement alteree chez tous les malades du groupe III. Cependant tous les malades etaient capables d'elaborer une urine diluee au maximum et d'augmenter le debit d'eau libre en fonction de l'augmentation du debit distal. Il est conclu que le deficit de Umax est le resultat d'alterations de la permeabilite a l'eau du canal collecteur qui, chez les malades du groupe III est combinee a une augmentation de la charge osmotique par nephron.