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.