A 51-year-old woman reported with a 2-month history of purulent discharge from her right flank. There was a cutaneous opening over the right flank with discoloration of the surrounding skin and nodules adjacent to the opening due to granulation tissue [Figure 1]. She had expulsion of purulent, foul-smelling discharge from the right flank with occasional fever spikes. There had been no prior intervention or trauma. Ultrasound of the right kidney with a 1-7 MHz curvilinear transducer revealed a large calculus at the ureteropelvic junction, causing dilatation of the renal pelvicalyceal system with echogenic debris noted within [Figure 2]. A linear fistulous tract was seen from the upper pole of the right kidney up to the skin surface [Figure 3]. A computed tomography (CT) urography study was performed, which supported the ultrasound results and indicated a nonexcreting right kidney. This patient underwent a total right nephrectomy with excision of the fistula tract. Microscopic examination revealed foamy histiocytes, multinucleated giant cells, and inflammatory cells in the renal parenchyma suggesting xanthogranulomatous pyelonephritis (XGP).
Nephrocutaneous fistulas are rare, with the most common predisposing factors being surgical procedures, urolithiasis, XGP, and genitourinary tuberculosis. Majority of the fistulas manifest with spontaneous drainage via the lumbar region following the path of least resistance. Ultrasonography reveals hypoechoic regions filled with pus, perirenal collection, and fatty infiltration of the kidney in the diffuse XGP. CT reveals renal enlargement with several parenchymal hypodensities, which along with calyceal dilatation and parenchymal loss, result in “bear's paw” sign.
Therapeutic approaches are influenced by the kidney function and the patient's capacity to tolerate the surgery, which can include total nephrectomy, partial nephrectomy, or isolated antimicrobial treatment. Spontaneous nephrocutaneous fistula develops after a longstanding inflammatory process which generally culminates in a nonfunctioning kidney. In such situations, radical nephrectomy with tract excision is recommended.
Conflict of interest
There are no conflicts of interest.
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The authors certify that he has obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Author contributions statement
Dr. Varun Nimje: Conceived the original idea, data collection, drafted the manuscript, critical revisions to the manuscript and final approval to the manuscript.
Dr. Shubham Bodhankar: Assisted in drafting the manuscript, Critical feedback to the manuscript, final approval to the manuscript.
Dr. Tushar Yadav: Critical revisions to the manuscript, final approval to the manuscript.
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