Granulomatous prostatitis

Granulomatous prostatitis is a nodular form of chronic prostatitis. It is usually diagnosed on biopsy.

Pathology

Causes

• idiopathic
• infection
• iatrogenic
  • Bacillus Calmette–Guérin (BCG) vaccine
  • post-radiotherapy
• systemic disease:
  • sarcoidosis
  • autoimmune

Subtypes

Several classification systems exist. A frequently used classification specifies the following subtypes:

• non-specific granulomatous prostatitis (NSGP): considered one of the commonest subtypes ^4,5
• infectious
• indeterminate

An alternate classification system has also been described:

• non-specific granulomatous prostatitis
• tubercular granulomatous prostatitis
• postsurgical granulomatous prostatitis
• allergic granulomatous prostatitis
• xanthogranulomatous prostatitis

Histology

Histological appearances are related to the underlying subtype ⁷.

Radiographic features

General features

Often there is no definite imaging finding to allow the diagnosis of granulomatous prostatitis to be made or, indeed, to differentiate it from prostatic carcinoma ².

Widening of the prostatic urethra, however, may be a useful feature in differentiation from cancer ¹.

Ultrasound

Ultrasound findings are divided into a hypoechoic nodule (~70%) or a diffusely hypoechoic peripheral zone (~30%)

MRI

Three morphological MRI patterns have been described which are diffuse, nodular (tumor-like), and cystic with mural nodule ³.

Signal characteristics include 

• T2: affected regions hypointense
• C+ (Gd): no enhancement following Gd-DTPA

History and etymology

It was first described by F H Tanner and J R McDonald in 1943 ¹³.