Clinical History
A male patient presented with a history of non-Hodgkin lymphoma previously treated with chemo- and radiotherapy, a cardiac pacemaker, and ischemic heart disease treated with coronary stenting one year earlier, recurrent urinary infections over 6 months.
Currently the patient presents with fever (38°C), urinary frequency, distended abdomen and pelvic pain. Urgent laboratory studies revealed mild leukocytosis and raised C-reactive Protein.
Imaging Findings
Bladder distension was relieved by positioning of a Foley catheter, yielding 500 ml of turbid urine. Digital rectal examination revealed enlarged, markedly tender prostate suggesting acute prostatitis.
The next day, the attending urologist requested urgent CT (Fig.1) to investigate impending urosepsis. As depicted by multiplanar reconstructions, the key CT finding was marked, moderately asymmetric prostatic enlargement (measuring approximately 10x8x9 cm), occupied by confluent nonenhancing hypoattenuating (17-19 Hounsfield Units) regions, with peripheral and septal enhancement. The prostatic abscess displaced upwards the urinary bladder, which showed mild circumferential mural thickening and mucosal hyperenhancement consistent with urinary infection. Additionally, similar infectious enlargement involved the left seminal vesicle. Urine culture diagnosed infection from antibiotic-resistant extended-spectrum beta-lactamase-positive Escherichia coli.
Surgical transperineal evacuation of the abscess was successfully performed (post-surgical status shown in Fig.2). Two months later, CT obtained for oncologic follow-up (Fig.3) confirmed persistent resolution of the surgically treated large prostatic abscess and normalised seminal vesicle.
Discussion
After the widespread use of broad-spectrum antibiotics, prostatic abscess (PA) has become a very uncommon disorder. The majority of reported cases occurred in the 5th-6th decades of life. Whereas in the preantibiotic era Neisseria was the leading causative organism, currently 60-80% of cases result from E.coli infection. PAs may result from unrecognized or inappropriately treated bacterial prostatitis (BP), and commonly develop in patients with predisposing factors such as indwelling catheters, bladder outlet obstruction, diabetes or immune suppression, recent instrumentation of the lower urinary tract or transrectal prostate biopsy [1-3].
The clinical manifestations of PAs are commonly non-specific such as fever, dysuria or frequency, dull pelvic or perineal pain, rectal tenesmus, prostatic tenderness at digital rectal examination, or acute urinary retention, and therefore largely overlap with those of acute BP. Laboratory studies may be generically consistent with an urinary tract infection, and prostate-specific antigen (PSA) levels are often moderately raised thus suggesting prostate carcinoma. Urine cultures may be, and become positive only when the abscess opens into the urethra or bladder [1-3].
However, the differential diagnosis between PA and acute BP is crucial since it impacts treatment. Transrectal ultrasound (TRUS) may detect a PA as single or multiple hypoechoic areas with thick walls, floating echogenic speckles in the cavity, and poorly defined periphery with increased colour Doppler signals [3, 4].
Compared to TRUS, as this case exemplifies CT with multiplanar image reconstruction provides a more comprehensive visualization of PAs, which appear as more or less symmetric prostate enlargement, occupied by single, septated or multiple fluid-like, non-enhancing demarcated collections, often with an peripheral enhancement. Furthermore, multidetector CT may depict signs of possible extraprostatic penetration with involvement of the prevesical space, rectum, perineum or ischiorectal fossa, and sometimes coexistent abdomino-pelvic infectious sites such as hepatic or renal abscesses. Finally, CT consistently allows monitoring PA during conservative or interventional treatment [5-7].
In conclusion, a PA should be suspected when acute symptoms related to the lower urinary tract persist or worsen after 48 hours of intensive antibiotic therapy. Hospitalization and prompt aggressive management of PAs are required to prevent development of urosepsis, which is associated with a non-negligible (3-16%) mortality. The mainstay treatment is parenteral antibiotics plus TRUS-guided or percutaneous transperineal aspiration, which usually obviates transurethral resection or surgical incision and drainage [1, 3, 4].
Differential Diagnosis List
Prostatic abscess
Acute bacterial cystitis / prostatitis
Benign prostatic hyperplasia
Prostate carcinoma
Perianal abscess
Rectal tumour
