Prostatitis

Prostatitis refers to an infection or inflammation of the prostate gland that presents as several syndromes with varying clinical features. Prostatitis is a clinical diagnosis and imaging is useful to evaluate abscess formation. 

Pathology

The National Institutes of Health (NIH) have classified prostatitis into four distinct syndromes ¹:

• I: acute bacterial prostatitis
• II: chronic bacterial prostatitis
• III: chronic prostatitis and chronic pelvic pain syndrome (CPPS)
  • further subclassified as inflammatory or non-inflammatory
• IV: asymptomatic inflammatory prostatitis

Radiographic features

Ultrasound

Focal hypoechoic region in the peripheral zone of the gland. Discrete fluid collection suggests abscess formation. Color Doppler ultrasound demonstrates increased flow in the periphery of the abscess. 

CT 

Contrast-enhanced CT is the best imaging tool if abscess is suspected and will demonstrate a diffusely enlarged, edematous gland with predilection for peripheral zone involvement.

When an abscess is present it is seen as a rim-enhancing, unilocular or multilocular, hypodensity in the peripheral zone. Central zone involvement is encountered in status post-transurethral resection of the prostate (TURP) patients. The infection can extend through the capsule into the periprostatic tissues, seminal vesicles, and peritoneum.

MRI

The prostate will be diffusely enlarged, often with associated inflammatory changes of periprostatic fat and of the seminal vesicles ⁶.

Acute prostatitis

• T1: peripheral zone iso- or hypointense to transition zone
• T2: hyperintense
• T1 C+ (Gd): diffusely enhancing ⁶

Treatment and prognosis

Antibiotics are the mainstay of treatment for bacterial prostatitis. In cases of chronic non-bacterial prostatitis, diuretics and anti-inflammatory medications may be needed instead.

Complications

• prostatic abscess
• emphysematous prostatitis

Differential diagnosis

• granulomatous prostatitis can be mistaken for prostatic carcinoma, especially on transrectal ultrasound ^3,4