Clinical History
A male patient presented with a history of urolithiasis, benign prostatic hyperplasia on tamsulosin therapy, long-term catheterisation after previous episodes of acute urinary retention.
The patient currently presents with septic fever, profound dehydration, poor hygiene, vague pelvic and inguinal pain, enlarged nontender prostate at digital rectal exploration.
Laboratory changes included leukocytosis, elevated (63 mg/L) C-reactive protein.
Imaging Findings
Four months earlier multidetector CT (Fig.1) showed contracted urinary bladder with indwelling Foley catheter, multiple calculi, circumferential mural thickening consistent with detrusor hypertrophy from outlet obstruction. Thin hyperenhancement along the urothelium was consistent with active urinary infection confirmed by urinalysis.
Currently, replacement of malfunctioning catheter relieved bladder distension with turbid urine. Urgent CT (Fig.2) requested to investigate urosepsis showed marked mural thickening of the urinary bladder with persistent urothelial enhancement, appearance of inflammatory stranding of the perivesical fat planes, and development of a sizeable (7.5x6x5.5cm) abscess collection attached to the bladder dome, characterised by nonenhancing hypoattenuating content (measuring 10-15 Hounsfield Units) and enhancing peripheral rim. Cystoscopy confirmed severely inflamed bladder mucosa without suspicious changes. Urine cultures revealed polymicrobial infection, haemocultures were positive for methicillin-resistant Staphylococcus aureus.
After poor improvement under intravenous antibiotics, surgical drainage of the bladder wall abscess was performed, plus prostatic adenomectomy and partial cystolithotomy (Fig.3).
Discussion
Urinary tract infections (UTI) account for hundreds of thousands of outpatient and emergency visits, and result from ascending bacterial infection from the urethra in the vast majority of cases. According to the European Association of Urology guidelines, complicated UTI are those associated with structural or functional genitourinary tract abnormalities or with impaired host defence mechanisms, which result in higher risk of acquiring infection or failing therapy. Compared to uncomplicated UTI, the spectrum of pathogens is wider (with Enterobacteriaceae as the commonest organisms) and antibiotic resistance is much more likely. In descending order of frequency, predisposing factors include intermittent or long-term catheterisation, indwelling stent, voiding dysfunction and bladder outlet obstruction, , obstructive uropathy from any cause, recent instrumentation, post-surgical setting, chemical or radiation injury [1].
Clinically, severity is graded according to the presence of local (such as dysuria, urgency, frequency, pelvic pain) or general symptoms, signs of systemic inflammatory response (SIRS, including fever or hypothermia, leukocytosis, tachycardia, tachypnoea), sepsis with organ failure, or septic shock. The latter two conditions represent severe situations with considerable (20-40%) mortality, favoured by advanced age, diabetes, renal impairment, immunosuppression [1-3].
Although the majority of UTIs are diagnosed clinically and confirmed by laboratory studies and urine culture, complicated UTIs are increasingly encountered due to the growing number of patients with the above-mentioned risk factors. Particularly when signs of sepsis are present, complicated UTIs usually warrant early imaging, particularly with contrast-enhanced multidetector CT, to direct the urological management [1, 3].
As this case exemplifies, currently CT investigation of complicated UTI may depict a diffuse, more or less irregular thickening and hyperenhancement of the bladder urothelium consistent with consistent with acute cystitis, which is similar to that described in infectious pyeloureteritis, and associated perivisceral fat inflammatory stranding [3].
Furthermore, mural abscesses of the urinary bladder may occasionally develop in patients with chronic UTI, history of permanent or intermittent catheterisation. As this case exemplifies, bladder abscesses appear as intramural or exophytic fluid-like collections with enhancing ring, without an appreciable communication with the bladder lumen. Diagnosing this rare occurrence is important because long-term catheterisation and drainage (either percutaneous or surgical) is required to relieve the septic focus [4-6].
Differential Diagnosis List
Mural abscess of the urinary bladder complicating acute bacterial cystitis.
Uncomplicated urinary tract infection
Acute prostatitis
Prostate / seminal vesicle abscess
Bladder diverticulum
Emphysematous cystitis
Urinary tuberculosis
Schistosomiasis
Urachal abscess
Bladder carcinoma
Fournier’s gangrene
Final Diagnosis
Mural abscess of the urinary bladder complicating acute bacterial cystitis.
