Guideline-discordant biopsy in suspected bilateral Wilms tumor and its surgical complications: a case report from a low-resource setting and review of current protocols

Wilms tumor (WT) is the most common malignant renal tumor in children. Paediatricians are typically the first point of contact for children presenting with an abdominal mass and may prematurely refer them for biopsy or upfront nephrectomy. Such interventions can unnecessarily delay chemotherapy and increase the risk of procedural complications. We report the case of an 18-month-old girl with suspected bilateral Wilms tumor who underwent a bilateral renal biopsy at an outside facility prior to referral. The right-sided biopsy was non-diagnostic, while the left-sided sample confirmed WT. The patient subsequently developed a draining sinus at the right biopsy site with purulent discharge, later intraoperatively confirmed as a pelviureteric fistula complicated by a refractory Escherichia coli infection. This complication significantly delayed both neoadjuvant chemotherapy (NACT) and definitive surgery. The two major international cooperative groups governing WT management—the Children’s Oncology Group (COG) and the SIOP Renal Tumour Study Group (SIOP-RTSG)—discourage routine diagnostic biopsy in children with typical imaging findings, allowing only narrowly defined exceptions. Crucially, neither recommends routine biopsy for bilateral disease at initial presentation. While emerging evidence supports the safety of image-guided biopsy in specific unilateral cases, these findings should not be extrapolated to bilateral tumors. This case with confirmed bilateral Wilms tumor reinforces existing guideline recommendations to avoid routine biopsy in suspected bilateral disease at initial presentation. Protocols such as COG AREN0534 permit selective biopsy later in the treatment course, guided by the patient’s response to initial chemotherapy, prior to definitive surgery. This report highlights the significant morbidity and treatment delays associated with guideline-discordant biopsies performed outside specialized paediatric oncology centers.