The relationship between urodynamic bladder compliance and urinary fibrosis markers in children with neurogenic bladder dysfunction.

Background: Decreased bladder compliance is an important risk factor for upper urinary tract in children with neurogenic bladder dysfunction (NBD). Urodynamics is the gold standard in determining bladder compliance.

Objective: To investigate the relationship between low bladder compliance and urinary fibrosis markers in NBD.

Study design: Spina bifida patients with NBD, who admitted between March 2021 and July 2021 were included. Patients with low compliant bladders, no renal scar, no recurrent urinary tract infections formed low compliance, LC group. Normal compliance, NC group, was comprised of patients with normocompliant bladders and the same characteristics. Control group (Group C) consisted of patients for outpatient surgery and had no known bladder dysfunction. Compliance was calculated with the formula ΔV/ΔP and a value of under 15 ml/cmH2O was accepted as low. Age, gender, urine density, serum urea, creatinine levels and urodynamic parameters were noted. Urinary type 1, type 3 collagen and its precursor procollagen type 3 and serum type 1 and 3 collagen were determined by ELISA.

Results: 72 patients were included (LC group, n:31, NC group, n:24, C group n:17, mean age 7,39 ± 1,24 years). No significant difference was observed in the comparison of age, gender, urine density and serum urea and creatinine values. No significant difference was observed between the LC and NC groups for urodynamic parameters, except for bladder compliance. Urinary collagen type 1 in LC group (11,71 ± 3,02 ng/ml) was found to be significantly higher than that of the C group (9,45 ± 1,97 ng/ml) (p = 0,03). Urinary procollagen type 3 was significantly higher in LC group (103,15 ± 24 ng/ml) when compared to C group (82,42 ± 22,26 ng/ml) (p = 0.016). Urinary collagen type 1 level above 9.20 ng/ml was 80,6 % sensitive and 70,6 % specific and urinary procollagen type 3 level above 78 ng/ml was 87 % sensitive and 70,6 % specific in predicting low compliance.

Discussion: This study seems to be the first study in the literature to evaluate bladder fibrosis and compliance, biochemically, by measuring urinary collagen levels in NBD. Urinary fibrosis markers are not currently an alternative to urodynamics for bladder compliance, but they may have potential to reduce the need for urodynamics with this indication.

Conclusion: Determination of urinary collagen levels may be a marker of bladder wall fibrosis and may indirectly show decreased bladder compliance. It is plausible to say that invasive methods such as urodynamics may be less preferred for defining bladder compliance, instead, urinary biomarkers may have merit for this purpose in the future.