A Unique Presentation of an Infected Renal Cyst: A Case Report and Literature Review

Renal cysts are prevalent conditions and are often diagnosed incidentally. The infection of renal cysts is an uncommon presentation. It is even more rare in solitary simple cysts than in autosomal dominant polycystic kidney disease (ADPKD). Patients with infected renal cysts can have variable presenting symptoms; however, almost universally, they have flank pain. Here, we report a case of a solitary renal cyst infection in the absence of flank pain, a relatively rare condition. A 60-year-old male patient presented to our emergency department (ED) for ongoing periumbilical/lower abdominal pain, chills, and high-grade fever. He was initially seen in urgent care and thought to have a urinary tract infection (UTI). He was discharged on trimethoprim-sulfamethoxazole (TMP-SMX). He was hemodynamically stable in the ED and did not have flank pain. Urine culture showed Escherichia coli. Computed tomography (CT) showed changes concerning for possible early pyelonephritis of the right kidney area and an enlarged right upper pole renal cyst compared to previous imaging. The urology team was consulted, and the enlarging cyst was considered secondary to hemorrhage. The patient continued to have high-grade fevers and worsening abdominal pain during his stay despite being on culture-directed intravenous antibiotics. Consequently, the cyst was aspirated, and cultures grew E. coli with a similar antimicrobial susceptibility pattern as the one found in the urine. After the procedure, the fever and abdominal pain significantly improved. This case report describes a patient with an infected solitary renal cyst with a unique presentation. Imaging modalities can be misleading and delay the diagnosis. Appropriate source control via cyst aspiration and/or drain insertion is crucial for successful treatment.