Infected Renal Cyst: Elusive Diagnosis and Percutaneous Management

Abstract

Background: Benign renal cysts are relatively common in older adults, usually found incidentally on CT. However, an infected renal cyst is a rare complication. While a course of antibiotic therapy is generally the first-line treatment, indications for definitive operative intervention include chronic pain, recurrent urinary tract infection, hematuria, abscess formation, and/or impaired renal function.

Case Presentation: A 61-year-old male urologist with no significant medical history was hospitalized at an outside facility for fever, chills, and abdominal pain. Initial diagnosis was pyelonephritis in the setting of a recently passed stone, with absence of hydronephrosis and a large, simple right renal cyst, but he failed to improve with intravenous antibiotics and developed intractable hiccups. Serial CT scans demonstrated onset of mild upper pole hydronephrosis and no change in the benign-appearing simple cyst. Interventional radiology planned drainage of the upper pole calices with a diagnosis of infundibular stenosis, but upon insistence of a urology consultant who suspected occult infection of the cyst, drains were placed into the collecting system and the cyst, with the return of a jet of purulent fluid upon cyst puncture.

Conclusion: The patient subsequently recovered and was discharged and seen at our facility where he was definitively treated with percutaneous endoscopic marsupialization of the cyst into the collecting system and fulguration of the infected cyst wall with complete resolution.

Introduction and Background

Renal cysts are commonly found incidentally and have a prevalence of 5% in the general population. As they are not a risk for malignancy, benign simple renal cysts (Bosniak I and II) only require intervention when causing symptoms (e.g., infection, hemorrhage, and mass effect). Infection is a rare complication of simple benign renal cysts with a prevalence of around 2.5%.^1,2 Treatment falls into three categories: antibiotic therapy, percutaneous treatment, and surgical management. Definitive management of cysts can be attempted percutaneously, endoscopically, and through decortication, usually through a laparoscopic approach.

Presentation of the Case

A 61-year-old male urologist with a known history of a simple right renal cyst presented to an outside facility with sudden onset of fever, chills, and abdominal pain and thought he may have seen a small stone pass in his urine. His white blood cell (WBC) count was elevated to 30,000 and his urinalysis demonstrated positive nitrite with moderate leukocyte esterase, greater than 50 WBCs, and 10–20 red blood cells per high-powered field with too many to count bacteria. CT was relatively unremarkable except for the known 8 × 8 × 9 cm simple renal cyst without evidence of stranding or infection or hydronephrosis (Figs. 1 and 2). The HU inside the cyst was calculated as 5 and did not enhance with contrast. He was diagnosed with pyelonephritis in the setting of a possibly recently passed stone. This was initially suspected given his characteristic presentation of colicky right flank pain radiating to the right groin, nausea, vomiting, subjective chills, and fever. His urine grew Escherichia coli, but over the next 10 days, he failed to improve with intravenous antibiotics and developed intractable hiccups with persistent fevers and an elevated WBC count. The second and third CT scans, with contrast, also read the cyst as simple. A WBC scan specifically stated that there was increased activity in the upper pole of the right kidney, “compatible with pyelonephritis, but there does not appear to be any activity associated with the previously identified right renal cyst.”

FIG. 1.

CT axial image of IRC. IRC, infected renal cyst.

FIG. 2.

CT coronal image of IRC.

Serial CT scans demonstrated onset of mild upper pole hydronephrosis and no change in the benign-appearing simple cyst. Interventional radiology planned drainage of the upper pole calices with a diagnosis of infundibular stenosis. However, upon insistence of a urology consultant who suspected occult infection of the cyst, drains were placed into the collecting system and the cyst, which resulted in the return of a jet of purulent fluid (Fig. 3). After drainage, he rapidly improved clinically with resolution of fevers, abdominal pain, and improved WBC count. He remained hospitalized for anasarca secondary to his septic state, which was treated with a loop diuretic. Clear yellow urine came out from both upper pole percutaneous nephrostomy tubes and the renal cyst, indicating a communication between the cyst and the renal collecting system. His condition improved and he was discharged home on oral ciprofloxacin, diuretics, and potassium.

FIG. 3.

Nephrostogram of nephrostomy tube placed within the upper right renal collecting system. The drainage catheter is placed in the IRC.

Physical Examination and Follow-Up

He followed up at our facility and we removed the patient's nephrostomy drain. He continued to drain urine, however, from the cyst drain. He was therefore offered definitive management of the cyst and elected for a percutaneous endoscopic approach.

Utilizing our standard prone positioning, cystoscopy was initially performed with placement of a guidewire and then an open-ended catheter into the right ureter. Retrograde ureteropyelography through the ureteral catheter defined a right ureter without filling defects, but with kinks and areas of stenosis as well as a fistulous communication between the collecting system and the renal cyst. Even after clamping the percutaneous drain, the cyst could not be filled. Of note, the previous drain into the cyst had been placed near the liver and colon and anteriorly where there was no adjacent parenchyma. Rather than dilating this tract, a fresh renal access was created. The cyst was filled as best as possible by placing contrast medium through the percutaneous tube and through the ureteral catheter simultaneously. This allowed needle and then guidewire access into the cyst. The new tract was dilated using a balloon dilator to 30F and a sheath was placed directly into the cyst.

Nephroscopy revealed that large portions of the cyst were necrotic, with multiple areas of thick, white, fibrous, and inflamed tissue. Methylene blue injected through the ureteral catheter could be seen entering the cyst in a necrotic and fluffy area of white tissue (Fig. 4). Eventually, dissecting through this tissue, the fistulous communication was found, entering the lower pole infundibulum and renal pelvis.

FIG. 4.

Endoscopic view within the abscess cavity.

A balloon infundibulopyeloplasty was performed to open the communication widely to provide drainage. The necrotic areas of the abscess wall were then vaporized with an Olympus bipolar button device, and then portions of the wall were excised and sent for pathology. The remainder of the non-necrotic cyst wall was fulgurated to destroy any fluid-forming capacity and allow coapation and adhesion of the wall to itself to promote involution. A ureteral stent was placed percutaneously for maximal drainage of the cyst into the collecting system, and the patient was left without percutaneous drains. The patient's stent was removed as an outpatient, and the patient has had no recurrence of the cyst or symptoms at eight-month follow-up.

Discussion and Literature Review

Most guidelines dictating the treatment of infected renal cysts (IRCs) are based on patients with autosomal dominant polycystic kidney disease (ADPKD), who commonly manifest symptoms from the extreme nature of their cystic disease. In a systematic review of 60 articles detailing the treatment of 85 ADPKD patients with IRCs, initial management predominately included antimicrobials, specifically quinolone-based therapies due to their heightened ability to penetrate the cysts. Percutaneous treatment consisting of cyst puncture, drainage, cyst aspiration, and surgical management is reserved for either failed medical therapy or obstructive emergencies.³ Operative management, including open surgery, laparoscopy, and endoscopic management, is largely determined by severity of symptoms, size, and relative position within the kidney. Given the size and position of the cyst within the renal pelvis, it was decided that the best and least invasive approach for our patient was to undergo percutaneous endoscopic marsupialization of the diverticulum/cyst, fulguration of the cyst wall, and marsupialization of the cyst into the collecting system with balloon infundibuloplasty. Key points in the management were insistence on drainage due to a strong index of suspicion despite a normal appearance on CT, creating a fresh tract into the cyst through the parenchyma to prevent a urinary fistula into the retroperitoneum, use of a bipolar button device to minimize bleeding and effectively resect the infected cyst wall tissue, and draining the cyst into the collecting system without a nephrostomy tube to prevent fluid accumulation and fistula formation into the retroperitoneum, respectively.

Conclusion

In this report, we discuss the elusive diagnosis of an IRC. A strong index of suspicion prevented further delay in treatment, and attention to specific points in management resulted in an improved outcome.

Abbreviations Used

ADPKD

autosomal dominant polycystic kidney disease

CT

computed tomography

HU

Hounsfield units

IRC

infected renal cyst

WBC

white blood cell

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Cite this article as: Gupta M, Sherman A, Rosen DC, Chandhoke R (2020) Infected renal cyst: elusive diagnosis and percutaneous management, Journal of Endourology Case Reports 6:2, 89–91, DOI: 10.1089/cren.2019.0128.