Effect of a Full Bladder on Urine Production in Humans

Abstract

Objective: To demonstrate the reduction in urine production in healthy humans 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 empty at the start and once pre-filled to 60% of the maximum bladder capacity. Glomerular filtration rate, effective renal plasma flow, urine content of catecholamines, blood pressure, pulse rate, plasma arginine vasopressin (AVP) and plasma concentration of renine and electrolytes were analysed together with serum osmolality. Results: Three subjects failed to reach maximum bladder capacity during the ?full bladder? test and were excluded. The urine 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 significant 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.