Disturbance in sodium regulating hormones in chronic obstructive uropathy.

Serum atrial natriuretic peptide (ANP), plasma renin activity (PRA), angiotensin II (AII) and aldosterone levels have been studied in patients with chronic bilateral ureteric obstruction resulting from high pressure chronic retention of urine (HPCR), both in the obstructed state and during the post-obstructed period. Increased ANP levels observed during chronic obstruction fell rapidly following urinary tract decompression by urethral catheterisation. Serum ANP resurged briefly within 24 h but stabilised thereafter at a lower level. PRA was initially suppressed but rose after catheterisation, the increase lagging behind the changes seen for ANP. Rising levels of AII and aldosterone followed this trend but, unlike PRA, levels were not completely suppressed in the obstructed state. The observed hormonal changes probably reflect homeostatic mechanisms directed to the maintenance of sodium and water balance during obstruction and to limitation of the diuresis following its relief.