OXYBUTYNIN LOWERS ELEVATED RENAL PELVIC PRESSURES IN A RAT CONGENITALUNILATERAL HYDRONEPHROSIS

We investigated whether oxybutynin could lower elevated renal pelvic p ressures measured in a rat with an inbred unilateral congenital hydron ephrosis. Simultaneous renal pelvic and bladder pressures were measure d in 8 hydronephrotic rats and compared to those of 10 hydronephrotic rats treated with intravenous injection of 1.6 mg./kg. oxybutynin. Pre ssures were recorded at different urinary flow rates and during bladde r filling and emptying. Hydronephrotic rats not given oxybutynin showe d significantly higher renal pelvic pressures (e.g. p-bladder at 50% c apacity = 8.9 +/- 3.1 cm. H2O, corresponding p-pelvis = 20.8 +/- 2.1 a t very high urinary flow rates) than rats treated with oxybutynin. The latter had renal pelvic pressures similar to rats with normal non-hyd ronephrotic kidneys (e.g. p-bladder at 50% capacity = 10.1 +/- 3.5 cm. H2O, corresponding p-pelvis = 6.3 +/- 1.1 at very high urinary flow r ates). Renal pelvic pressures were, moreover, lower than corresponding bladder pressures in contrast to the untreated hydronephrotic pelvic pressure that exceeded bladder pressure. This effect of oxybutynin in lowering elevated renal pelvic pressures in the obstructed kidney has not been described before and suggests a possible role for oxybutynin in this condition.