Effect of a full bladder on urine production in humans

Objective: To demonstrate the reduction in urine production in healthy huma ns upon bladder distension and to identify the factors responsible for this reduction. Materials and Methods: Twelve healthy females were investigated twice in a cross-over designed experiment: once with the urinary bladder e mpty at the start and once pre-filled to 60% of the maximum bladder capacit y. Glomerular filtration rate, effective renal plasma flow, urine content o f catecholamines, blood pressure, pulse rate, plasma arginine vasopressin ( AVP) and plasma concentration of renine and electrolytes were analysed toge ther with serum osmolality. Results: Three subjects failed to reach maximum bladder capacity during the "full bladder" test and were excluded. The uri ne production in the ''full-bladder" test was significantly lower than the "empty-bladder" test (p = 0.024). In the "full-bladder" test a significant increase in mean blood pressure was found (p = 0.01). No further significan t changes were demonstrated. Conclusions: Acute bladder distension causes a reduction in urine production or a "pooling of urine" in the upper urinary tract in healthy humans. The mechanism is unknown.