A 74-year-old woman presented to the hospital with fever, nausea, lethargy, and abdominal pain. Her past medical history was significant for end-stage renal disease, resulting from bilateral nephro-ureterectomy for chronic pyelonephritis secondary to chronic reflux nephropathy. She was febrile with temperature of 38.3 °C, and physical examination showed tense suprapubic tenderness without involuntary guarding. The laboratory work-up demonstrated a leukocytosis (WBC 16,000/mm3, normal 4,000–11,000/mm3). Blood cultures were negative. Computed tomography (CT scan) of the abdomen and pelvis was performed because of the persistent suprapubic pain, and it showed a thickened bladder wall with a small-sized urinary bladder (Fig. 1a, b). A straight urinary catheter was cautiously inserted, and purulent fluid was drained out. A presumptive diagnosis of pyocystis was entertained. A flexible cystoscopy was subsequently performed. Purulent fluid and tissue debris were noted within the bladder, and were aggressively irrigated out. Suprapubic and Foley urinary catheters were placed. Fluid culture grew Escherichia coli, Citrobacter freundii and Enterococcus faecalis. Continuous neomycin bladder irrigation was applied via the suprapubic catheter, and then drained through the Foley catheter. Systemic intravenous piperacillin-tazobactam 2.25 g every 12 h was administered simultaneously. She received 4 weeks of antimicrobial therapy, via both intravenous and intravesical routes, to control the infection. The patient was eventually discharged without additional antibiotics.

Fig. 1
figure 1

Computed tomography abdomen and pelvis with intravenous contrast demonstrates a small urinary bladder with thickened cystic wall in both axial (a) and coronal (b) views (white arrows)

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Pyocystis, also known as vesical empyema, is the accumulation of pus in the urinary bladder, especially a defunctionalized bladder in patients with end-stage kidney disease, supravesical urinary diversion without radical cystectomy or bladder irradiation [1]. Pyocystis syndrome gained attention in the 1960s after urinary diversion procedures became the standard treatment for a variety of lower urinary tract pathologies. The reported incidence of this complication ranged from 10 % to as high as 67 % in patients with supravesical urinary diversion procedures [2, 3]. It is reported to be rare in dialysis patients, but its actual incidence in that patient population is not known [3, 4]. There are many postulated mechanisms of pathogenesis of pyocystis. The widely accepted one is the collection, liquefaction and decomposition of shed bladder epithelium. As part of wear and tear, the lining bladder epithelium is shed continuously, and then expelled out by urine flow. In anuric patients, the shed epithelial cells accumulate, and, when infected, pyocystis is typically ensued [1–4].

The presenting symptoms are usually similar to those in patients presenting with a lower urinary tract infection, including fever, suprapubic pain, purulent urethral discharge or sepsis. Microbiologically, the causal microorganisms are routine urinary pathogens, such as E. coli, Proteus spp., Serratia spp. and Enterococcus spp. [2, 3]. Diagnosis is based on symptoms of lower urinary tract infection, purulent discharge via the urethra or during catheterization, supported by CT scan imaging studies showing a characteristic thickened, hypertrophied, and cystic appearance of the bladder wall (Fig. 1a, b) [3, 4]. Despite the familiar clinical presentation of urinary tract infection, the diagnosis is usually delayed or missed, as it is mistakenly assumed that urinary bladder infection does not develop in anuric patients. Its treatment is unique, and routinely requires combined systemic and intravesical antibiotic administration in order to eradicate the infection. The duration of therapy is usually 2–4 weeks, and it is determined by the clinical response. Cystectomy is often performed in recalcitrant cases with multiple recurrences in spite of optimal antimicrobial therapy [3, 4].

In conclusion, pyocystis is a forgotten complication of a non-functioning bladder in anuric patients or patients with supravesical urinary diversion without primary cystectomy. It is important for practicing physicians to recognize pyocystis disease because its treatment differs from that of the usual cystitis. Urinary catheterization, and combined systemic and intravesical antibiotic therapy are required to treat this locally infected bladder. Cystectomy is the last option for resistant cases of pyocystis.