Metabolic consequences and tubular function after augmentation cystoplasty in children with neurogenic bladder

Background: While many studies have reported the renal outcomes and metabolic consequences of augmentation cystoplasty (AC), few have focused on changes in renal tubular function. This study investigated the prevalence of metabolic disturbances, renal tubular function, and 24-hour urine chemistry, aiming to evaluate the association between metabolic alterations and urolithiasis after AC. Methods: We investigated serum biochemistry, blood gas, and 24-hour urinary metabolic profile of children who underwent AC between January 2000 and December 2020. The assessed outcomes included metabolic complications, tubular function, and magnesium status. Associations between 24-hour urinary metabolic parameters and urolithiasis formation were also examined. Results: A total of 25 patients with a mean follow-up period of 13.8 ± 5.7 years were enrolled. The mean age at AC was 7.5 ± 4.4 years, and 22 and 3 patients underwent AC using the ileum and colon, respectively. There were no abnormalities in serum levels of sodium, potassium, chloride, and calcium. Hypomagnesemia (magnesium <1.7 mg/dL) due to renal loss was observed in one patient (4.0%). Six (24.0%) patients had increased urinary β2-microglobulin levels and normal serum levels. The ratio of the maximum rate of tubular phosphate reabsorption to the glomerular filtration rate was low in three (12.0%) patients. Four (16.0%) patients had normal serum magnesium levels but urinary magnesium excretion <40 mg/d. Urolithiasis occurred in 11 patients (44.0%). The most common 24-hour urine metabolic abnormality was hypomagnesiuria (72.0%). No urinary metabolic parameters or daily protein intake were associated with urolithiasis. Conclusion: AC for children is safe and does not significantly impact the metabolic profile. Excretions of 24-hour urinary calcium, uric acid, magnesium, and the sodium-to-potassium ratio were not associated with urolithiasis. However, a high prevalence of 24-hour urine magnesium excretion <88 mg/1.73 m2 was noted. Further prospective studies are needed to investigate longitudinal changes in renal tubular function and 24-hour urine metabolic profiles, particularly magnesium status.