[A rare case of complex pyelocutaneous fistula following microwave ablation for recurrent renal cell carcinoma successfully managed with radical nephrectomy]

Abstract

A complex pyelocutaneous fistula developed after microwave ablation for recurrent clear cell renal carcinoma following partial nephrectomy. The fistula persisted despite prolonged drainage, antibiotics, ureteral stenting, and other conservative measures. Definitive management required laparoscopic radical nephrectomy with complete excision of the fistulous tract and involved psoas tissue. Histopathology showed chronic inflammation without residual malignancy. This case supports early consideration of radical nephrectomy for refractory, anatomically complex pyelocutaneous fistulas.

1. Introduction

Postoperative recurrence of renal cell carcinoma remains a significant clinical challenge. Owing to its minimally invasive nature and proven therapeutic efficacy, ablative therapy has been endorsed by the European Association of Urology (EAU) as an important alternative for managing such recurrent lesions¹.² Nevertheless, this modality is not without risk, with bleeding and hematuria being the most frequently encountered complications³.⁴ We describe an exceptionally rare case of a complex pyelocutaneous fistula that developed after microwave ablation in a patient with recurrent clear cell renal carcinoma following partial nephrectomy. This report aims to enhance clinicians’ awareness and management of this uncommon yet clinically consequential complication.

2. Case report

A 52-year-old male underwent laparoscopic partial nephrectomy of the right kidney in August 2021 following a CT scan revealing a lower pole mass in the right kidney (Fig. 1A). Postoperative pathology demonstrated clear cell carcinoma of the right kidney.

Fig. 1.

(A)CT scan in 2021 showing a right renal lower pole mass (48.5 × 47.5 mm). (B) MRI in 2024 demonstrating tumor recurrence with extension to the right psoas major muscle.

At the July 2024 follow-up, MRI revealed recurrence of the right renal tumor with metastasis to the right psoas muscle (Fig. 1B). The patient underwent microwave ablation therapy in August 2024. Postoperatively, a right ureteral stent was placed due to right ureteral stricture and hydronephrosis. In March 2025, removal of the ureteral stent led to an immediate right renal pelvic fistula at the lower pole, causing perirenal effusion and subsequent infection. Given the perirenal urine leakage and infection, an ultrasound-guided percutaneous nephrostomy (PCN) tube was placed for urinary diversion and drainage.

Despite the aforementioned interventions, the renal pelvic leak persisted and progressively evolved into a pyelocutaneous fistula, resulting in the formation of a right lumbar cutaneous opening (Fig. 2A–D).

Fig. 2.

MRI findings of the pyelocutaneous fistula after percutaneous nephrostomy (PCN) placement. (A) Coronal MRI demonstrates fluid signal extending from the right renal collecting system toward the posterolateral pararenal region (arrows). (B) Coronal MRI further delineates the fistulous extension along the pararenal space, with the PCN catheter in situ. (C) Axial MRI shows a tract-like extension toward the right lumbar soft tissues adjacent to the nephrostomy tract (arrows). (D) Axial MRI demonstrates inflammatory changes around the right psoas major region and adjacent tissues (arrows), consistent with a complicated fistulous process.

Physical examination revealed a skin fistula opening below the right nephrostomy tube, with purulent discharge and exudate. The surrounding skin exhibited erythema, elevated temperature, and marked tenderness (Fig. 3A). Notably, according to the patient's report and subsequent clinical evaluation, the cutaneous fistula opening developed only after PCN placement and was located inferior to the nephrostomy site, suggesting that the nephrostomy tract may have served as a low-resistance pathway for fistula extension to the skin.

Fig. 3.

Skin Fistula Opening and Healing Process. (A). A skin fistula opening is visible below the right nephrostomy tube, with purulent discharge and exudate, surrounded by erythematous and edematous skin. (B). The skin fistula opening is largely healed on postoperative day 10. (C). The skin fistula opening is completely healed at 1 month postoperatively.

Preoperative blood tests, urinalysis, biochemical markers, and tumor markers showed no significant abnormalities. After ruling out surgical contraindications, the patient underwent laparoscopic radical nephrectomy of the right kidney combined with adhesiolysis of the psoas major muscle. Intraoperatively, extensive fibrotic adhesions were observed in the perirenal and psoas major muscle regions, accompanied by scar tissue proliferation. The perirenal fascia was tightly fused with surrounding tissues, presenting significant difficulty in separation. The patient recovered well postoperatively. The fistula site had largely healed (Fig. 3B), and the patient was discharged on the 10th postoperative day. At the one-month follow-up, the original skin fistula site had completely healed (Fig. 3C). Postoperative pathology (Fig. 4A and B) revealed no evidence of malignant disease.

Fig. 4.

Histopathological findings of the nephrectomy specimen and perirenal tissue (H&E). (A) Kidney specimen shows chronic inflammatory cell infiltration with prominent fibrosis, without evidence of residual or recurrent malignancy. (B) Perirenal soft tissue demonstrates dense fibrotic/inflammatory changes consistent with chronic inflammation, with no malignant cells identified.

3. Discussion

This case describes a highly complex postoperative course following recurrent RCC treated with microwave ablation, culminating in a pyelocutaneous fistula and definitive completion radical nephrectomy. To our knowledge, the literature contains scarce reports of pyelocutaneous fistula after percutaneous microwave ablation. We suspect that ablation-related injury to the collecting system and adjacent tissues, compounded by persistent urine leakage and infection, promoted tissue necrosis and tract formation, ultimately leading to extension through the abdominal wall.⁵

The MRI was obtained after an ultrasound-guided percutaneous nephrostomy (PCN) tube was placed in March 2025 for urinary diversion. Importantly, the cutaneous opening appeared only after PCN placement and was located inferior to the nephrostomy site, supporting the likelihood that the nephrostomy tract provided a low-resistance pathway for extension of the fistulous process to the skin.

Persistent fistulas with ongoing infection and inadequate drainage seldom resolve with conservative measures such as prolonged catheter drainage or ureteral stenting.⁵ In addition, there is no standardized strategy for managing this specific complication. In our patient, once infection was controlled and the tract extent was delineated on imaging, completion radical nephrectomy with complete excision of the fistula tract and adjacent infected, adherent iliopsoas tissue achieved definitive source control. Repeated interventions and chronic inflammation had resulted in marked perirenal fibrosis with adhesions involving the perirenal space and the psoas major muscle,⁶ findings that were confirmed intraoperatively and substantially increased the technical complexity and operative risk of dissection. Pathology demonstrated chronic inflammation, fibrosis, and necrosis in the involved kidney and fistula region, without residual or recurrent tumor, confirming that symptoms were driven by post-ablation complications rather than malignancy.

4. Conclusion

Pyelocutaneous fistula after renal microwave ablation is exceedingly rare yet clinically consequential. In this patient, the fistula emerged only after PCN placement with the cutaneous opening inferior to the nephrostomy site, supporting the nephrostomy tract as a low-resistance conduit; when conservative measures fail amid infection and dense adhesions, completion radical nephrectomy with complete fistula-tract excision provides definitive source control and durable resolution.

CRediT authorship contribution statement

Lianpeng Gao: Writing – review & editing, Writing – original draft. Bo Zhu: Writing – review & editing, Data curation. Xiaoxia Li: Writing – original draft. Yuyun Wu: Writing – review & editing. Wenbo Zhou: Writing – original draft, Data curation. Jiongming Li: Writing – review & editing, Supervision.

Ethics statement

This case report complied with institutional ethical standards. Written informed consent was obtained from the patient for publication.

Data availability statement

All relevant data are within the manuscript and its Additional files.

Funding sources

This work was supported by the Zhou Li-qun Expert Workstation of the Yunnan Provincial Department of Science and Technology (Grant No. 202505AF350061).

Conflict of interest statement

The authors have no conflicts of interest to declare.