Baseline renal function and renal ultrasound findings in patients with obstetric fistulas (RENFRU): a prospective cohort study

Objective To describe and compare baseline renal anatomy and renal function in patients with obstetric fistulas, and to evaluate whether preoperative renal testing and imaging may aid with operative decision making. Design A prospective cohort study. Setting Fistula Care Centre in Malawi. Population Women with an obstetric fistula. Methods Baseline creatinine testing and renal ultrasounds were performed. Surgeons completed a short questionnaire on the usefulness of creatinine and renal ultrasound on operative decision making. Main outcome measures Baseline creatinine and renal ultrasound findings. Results Four surgeons performed operations on 85 patients. The mean creatinine in patients with vesicovaginal fistulas (VVF) was 0.60 ng/ml versus patients with uretero-vaginal fistulas (UVF) (0.79 ng/ml, P = 0.012). When a grade 3 or more hydronephrosis is absent on renal ultrasound, the negative predictive value of the presence of UVF is 93.3% (95% confidence interval [CI] 88.6-96.2) with a specificity of 97.2% (95% CI 90.3-99.6). In cases of UVF, surgeons found the renal ultrasound results useful or very useful 87.5% of the time, and the creatinine useful or very useful 75% of the time. Conclusion In this pilot study, most patients with obstetric fistulas presented with a normal creatinine. In the absence of a grade 3 hydronephrosis or above on renal ultrasound, the probability of not having a UVF is 93.3%. Surgeons should consider performing preoperative renal ultrasound testing in all patients with an obstetric fistula, particularly in women with a prior laparotomy, as this population has risk factors for ureterovaginal fistula. Tweetable abstract Most patients with obstetric fistulas have normal renal function. Preoperative renal ultrasounds should be performed.