Authors from Ulm have a further look at their model of orthotopic bladder replacement and particularly at the problem of mild metabolic acidosis due to proton reabsorption, which they describe as a common problem after ileal neobladder. They ascribe it to the mucus production of the neobladder, and its internal surface or diuresis, but suggest further investigation to characterize the different influences further.
To assess the extent and mechanism of renal reabsorption and excretion in patients with an ileal neobladder, as mild metabolic acidosis cause by proton reabsorption is common after such surgery, and long-term pharmacological correction is often necessary.
PATIENTS AND METHODS
The study comprised 30 patients (29 men and one woman) with ileal neobladders after oncological surgery; before surgery all had normal retention values. Before and after withdrawing the transurethral catheter, serum creatinine and urea were analysed and used to assess the effect of the neobladder on retention values, expressed as the percentage change from baseline (Δ creatinine and urea).
There was a significant correlation between the Δ−creatinine and Δ−urea values (P < 0.001; r = 0.66); 15 patients (50%) showed resorption of creatinine and urea, eight (27%) excreted creatinine into the neobladder and resorbed urea from it at the same time, and three (10%) showed the reverse response, i.e. creatinine resorption and urea excretion. Interestingly, four patients (13%) excreted both creatinine and urea into the neobladder.
We assume that there was both a resorptive and excretory function. Probably the metabolic state (resorption or secretion) of the neobladder depends on its mucus production and on the internal surface, or on diuresis. Further investigation is required to characterize these different influences.