Studies on experimental bladder outlet obstruction in the cat: long-term functional effects.

Experimental bladder outlet obstruction in cats induces a significant increase in the in vivo leakage pressure. The effects of obstruction on the detrusor function were analyzed, using control, 3, 6 and 12 month obstructed cats. The in vivo leakage pressures were substantially increased in all obstructed groups. From a previous study on the short-term effects of obstruction in the cat; although there was an immediate increase in pressure, there were no significant differences between control bladders and two week obstructed bladders in: bladder weight, peak pressure response to field stimulation and bethanechol, and emptying of the in vitro whole bladder model. In this current study, although there was no direct relationship between duration of obstruction and severity of the impaired pharmacological response of the isolated whole bladder, there was a direct relationship between the magnitude of the increase in bladder weight, leakage pressure, and impaired functional response of the in vitro whole bladder. In this regard the cats were separated into four groups: controls and shams (average bladder weight 2.95 gm.), obstructed group 1 with bladder weights less than 6.0 gm. obstructed group 2 with bladder weights between 6 and 10 gm., and obstructed group 3 with bladder weights greater than 10 gm. The results can be summarized as follows: A) In vivo leakage pressures were significantly increased in all obstructed groups, and progressively higher in proportion to the bladder weights. B) Bladder capacity significantly increased in all, being greatest in obstructed group 3. C) The magnitude of the response to field stimulation of obstructed groups 1 and 2 were significantly greater than the response of control bladders at virtually all frequencies. The frequency response curve of obstructed group 3 was similar to control. D) The ability of the bladder to empty in response to field stimulation was significantly reduced in all obstructed groups. The magnitude of the decrease was proportional to the increase in bladder weight. E) There were no differences between control and obstructed bladders in the pressure response to bethanechol or KCl; the ability of both bethanechol and KCl to empty the bladder was reduced in the obstructed groups. In general, the presence of bladder enlargement was accompanied by significant alterations in the ability of the in vitro bladder to empty in response to field stimulation, bethanechol, and KCl.(ABSTRACT TRUNCATED AT 400 WORDS)