Asymptomatic Urolithiasis Complicated by Nephrocutaneous Fistula

Abstract

Asymptomatic spontaneous nephrocutaneous fistula is a rare and severe complication of chronic urolithiasis. We report a case of 56-year-old woman with a nephrocutaneous fistula (NFC) which developed from a superinfected urinoma following calyceal rupture due to an obstructing calculus in the left ureter. The patient was clinically asymptomatic and came to the emergency department for a painless left flank fluctuating mass. This urinoma was superinfected, with a delayed development of renal abscesses and perirenal phlegmon found on contrast-enhanced uro-computed tomography (CT), responsible for left renal vein thrombophlebitis and left psoas abscess. Thereafter, a 99 mTc dimercaptosuccinic acid (DMSA) scintigraphy revealed a nonfunctional left kidney, leading to the decision of left nephrectomy. Chronic urolithiasis complications are rare and only few cases are reported in medical literature. A systematic medical approach helped selecting the best imaging modality to help diagnosis and treatment. Indeed, uro-CT scan and renal scintigraphy with 99 mTc-DMSA are the most sensitive imaging modalities to investigate morphological and functional urinary tract consequences of NFC, secondary to chronic urolithiasis.

Keywords: Calyceal rupture; hydronephrosis; nephrectomy; nephrocutaneous fistula; surinfected urinoma; thrombophlebitis.

Figure 1

(a) Contrast-enhanced abdominal computed tomography obtained to characterize the initial ultrasound imaging findings. Contrast-enhanced abdominal computed tomography reformation in a coronal plane with soft tissue window shows the communication (red arrow) between the perinephric abscess and the posteroinferior aspect of the left kidney. Hydronephrosis (white arrow) and cortical atrophy suggest chronic obstructive uropathy. Perinephric fat infiltration extends into the left psoas muscle (yellow arrow). (b) Contrast-enhanced abdominal computed tomography in axial plane at the renal level with soft tissue window shows heterogeneous thickening adjacent to the superior pole of the left kidney, with confluent cortical abscesses and an intense inflammatory stranding of the perirenal fat (white arrow). This infiltration extends into the parietal lumbar abscess (red arrow) which fistulizes to the skin (white arrowhead). (c) Contrast-enhanced abdominal computed tomography in axial-oblique plane at the level of the left renal vein with soft tissue window shows the occlusion of the proximal aspect of this vein (red arrow), surrounded by inflammatory changes in the adjacent fat, consistent with thrombophlebitis. (d) Contrast-enhanced abdominal computed tomography reformation in the coronal plane with soft tissue window shows the obstructing left ureteral calculus (white arrow). (e) Three-dimensional volume-rendered image in coronal plane from the excretory phase of the abdominal and pelvic computed tomography shows the left lumbar ureteral calculus (green spot) and no excretion of contrast into the left collecting system. By comparison, the right collecting system is well delineated by the normal excretion of intravenously administered iodinated contrast media. (f) Three-dimensional volume-rendered abdominal computed tomography image reveals a small red spot corresponding to the nephrocutaneous fistula (white arrow) can be depicted at the level of the left dorsolumbar fluctuating mass. Based on these images and on the clinical presentation, the radiologist concludes to a nephrocutaneous fistula related to an infected urinoma secondary to an obstructing left ureteral stone and pelvicalyceal rupture.

Figure 2

A 56-year-old woman presents to the emergency department for a left painless dorsolumbar fluctuating mass which was progressively growing over 3 months. Ultrasonography was the first imaging study obtained. A long-axis view of the left kidney shows subcutaneous and parietal multiloculated heterogeneous hypoechoic collections, compatible with abscess adjacent to the left kidney (red arrow). Moderate left hydronephrosis is also present (white arrowheads).

Figure 3

Ultrasonography and computed tomography showed an infected urinoma with left pelvicalyceal rupture, secondary to an obstructive calculus with nephrocutaneous fistula. The calculus was endoscopically removed and a left ureteral stent was placed, with an antibiotic coverage. The clinical condition of the patient did not improve after antibiotic therapy. A planar image from 99 mTc-dimercaptosuccinic acid cortical renal scintigraphy was performed to estimate the remaining left kidney function and shows the uptake percentages of the radionuclide by the normal right kidney (Roi 1) and by the nonfunctional left kidney (Roi 2), estimated to 4%. The miniscule remaining left renal function leads to the decision to perform total left nephrectomy.

Figure 4

This patient undergoes a left nephrectomy for infected urinoma with nonfunctional kidney, secondary to an obstructive calculus, calyceal rupture, and nephrocutaneous fistula. A picture of the pathological specimen of the left ureter at the level of the obstruction shows a left ureteral obstruction by a conglomerate of microstones (white arrowheads). The proximal ureter (white arrow) is surrounded by an intense chronic fibroinflammatory process while the distal ureter is normal (red arrow).