Hormonal changes related to reduced renal blood flow and low urine output under prolonged increased intra-abdominal pressure in pigs.

OBJECTIVE: To investigate effects of prolonged increased intra-abdominal pressure (IAP) on diuresis, renal blood flow, and hormones that influence renal function, in particular endothelin. DESIGN: Experimental study. SETTING: Haukeland University Hospital, Norway. ANIMALS: 21 domestic pigs. METHODS: The TAP was maintained at normal (n = 7) or at 20 mmHg (n = 7) or 30 mmHg (n = 7) for three hours. MAIN OUTCOME MEASURES: Urine output, renal venous pressure, renal artery blood flow (transit-time flowmetry), renal cortex blood flow (microspheres), and renin, aldosterone, atrial natriuretic factor (ANF), adrenaline, noradrenaline, cortisol, and endothelin-1 (ET-1) in renal venous blood. RESULTS: An IAP of 20 mmHg was followed by no significant changes in the variables studied. An IAP of 30mmHg was associated with anuria, considerably reduced renal blood flow and increased renal vascular resistance. The renin activity and the blood concentrations of ET-1, aldosterone, noradrenaline, adrenaline, and cortisol increased during the three hours that IAP was at 30 mmHg. CONCLUSION: An IAP of 20 mmHg did not influence renal haemodynamics or diuresis. The low renal blood flow observed at an IAP of 30 mmHg probably results from reduced arteriovenous pressure difference and vasoconstriction. Increased concentrations of endothelin, angiotensin II, and noradrenaline may account for the vasoconstriction. The anuria can be explained by low renal blood flow and increased reabsorption of sodium in renal tubules caused by aldosterone.