A L Poulsen1, K Steven. 1. Department of Urology, Herlev Hospital, University of Copenhagen, Denmark.
Abstract
OBJECTIVES: To assess acid-base metabolism after bladder substitution with the ileal Kock reservoir, using capillary blood-gas analysis, measurement of the renal excretion of ammonium and titratable acid and the evaluation of renal function by plasma clearance of 51Cr-labelled ethyl-enediamine tetra-acetic acid (51Cr-EDTA). PATIENTS, SUBJECTS AND METHODS: The investigation comprised both a cross-sectional study, with initial measurements after surgery, and a longitudinal study, with pre-operative measurements, both groups of patients being followed for 2 years after inclusion. The cross-sectional study included 26 patients (median age 66 years, range 44-75), with a median post-operative follow-up of 1.2 years (range 0.3-3.7), and 16 control subjects (median age 62 years, range 34-80), and the longitudinal study comprised seven patients (median age 57 years, range 42-68). RESULTS: The median values for capillary blood pH, carbon dioxide pressure, standard bicarbonate and standard base excess were significantly lower in patients with a bladder substitute than in the control subjects. An acid-base chart showed that the values for 44% of patients and none of the controls were within the area representing mild metabolic acidosis. This difference could not be attributed to differences in renal function because the 51Cr-EDTA clearance was normal and similar in the two groups of patients and among patients and controls. Nevertheless, the median values for each of the variables measured by blood-gas analysis were within the reference interval of the normal population. Net acid excretion was similar in patients with a bladder substitute and control subjects, but urinary pH was significantly higher in the patients. Accordingly, the renal excretion of ammonium was significantly higher and the excretion of titratable acid significantly lower in patients after ileal bladder substitution. CONCLUSIONS: The results are consistent with the hypothesis that bladder substitution with the ileal Koch reservoir results in an acid load to the body, caused mainly by ammonium reabsorption in the reservoir. The acid load is compensated by an increased renal excretion of ammonium but causes a mild metabolic acidosis in about half the patients.
OBJECTIVES: To assess acid-base metabolism after bladder substitution with the ileal Kock reservoir, using capillary blood-gas analysis, measurement of the renal excretion of ammonium and titratable acid and the evaluation of renal function by plasma clearance of 51Cr-labelled ethyl-enediamine tetra-acetic acid (51Cr-EDTA). PATIENTS, SUBJECTS AND METHODS: The investigation comprised both a cross-sectional study, with initial measurements after surgery, and a longitudinal study, with pre-operative measurements, both groups of patients being followed for 2 years after inclusion. The cross-sectional study included 26 patients (median age 66 years, range 44-75), with a median post-operative follow-up of 1.2 years (range 0.3-3.7), and 16 control subjects (median age 62 years, range 34-80), and the longitudinal study comprised seven patients (median age 57 years, range 42-68). RESULTS: The median values for capillary blood pH, carbon dioxide pressure, standard bicarbonate and standard base excess were significantly lower in patients with a bladder substitute than in the control subjects. An acid-base chart showed that the values for 44% of patients and none of the controls were within the area representing mild metabolic acidosis. This difference could not be attributed to differences in renal function because the 51Cr-EDTA clearance was normal and similar in the two groups of patients and among patients and controls. Nevertheless, the median values for each of the variables measured by blood-gas analysis were within the reference interval of the normal population. Net acid excretion was similar in patients with a bladder substitute and control subjects, but urinary pH was significantly higher in the patients. Accordingly, the renal excretion of ammonium was significantly higher and the excretion of titratable acid significantly lower in patients after ileal bladder substitution. CONCLUSIONS: The results are consistent with the hypothesis that bladder substitution with the ileal Koch reservoir results in an acid load to the body, caused mainly by ammonium reabsorption in the reservoir. The acid load is compensated by an increased renal excretion of ammonium but causes a mild metabolic acidosis in about half the patients.