Stabilization of Renal Deterioration Caused by Bladder Volume Dependent Obstruction

Abstract

Previously published data from our unit show the detrimental effect of excessive bladder filling at normal pressure on renal function in chronically dilated renal units. Synchronous cystometry and dynamic renography identified a critical volume of filling that prevents upper tract drainage. In this followup study we determined whether maintaining bladder volume below this critical level would halt renal deterioration. Followup data were collected on 20 patients in the original study. All had progressive renal function deterioration for which no other cause was identified. Creatinine measured nearest to the time of the study renogram served as a baseline and subsequent values were used to monitor renal function. Data were analyzed by the paired Student t test. Complete data were obtained on 14 patients with a mean age of 34.4 years (range 22 to 70). The mean glomerular filtration rate at entry to this part of the study was 42 ml per minute per 1.73 m(2) (range 18 to 69). Four patients had a neuropathic bladder, 4 had posterior urethral valves, 4 had bladder exstrophy, 1 had radiation cystitis, 1 had a solitary pelvic kidney and detrusor failure, 5 had a native bladder and 9 underwent cystoplasty. Drainage was via the native urethra and a Mitrofanoff channel in 7 cases each. Mean followup was 27 months (range 3 to 39). There was no significant difference in mean +/- SD creatinine at baseline vs latest followup (168 +/- 72 vs 185 +/- 90 micromol/l, p >0.05). In patients with bladder volume dependent renal obstruction function can be stabilized by consistently maintaining bladder volume below the critical level.