Prostatic Inflammation

Type

Etiology

I. Acute prostatitis

Bacterial

II. Chronic prostatitis

Bacterial

III. Chronic nonbacterial/Chronic pelvic pain syndrome

Not known

IV. Asymptomatic prostatitis

Several causes

Table 21.2

Pathological classification of prostatitis [3]

Acute inflammation (observed in type I of clinical classification)
Chronic inflammation (observed in types II and IV of clinical classification)
Chronic inflammatory cells
Granulomatous inflammatory infiltrate (observed in type II of clinical classification and type IV if asymptomatic)
Specific granulomatous disease (or infective granuloma, Mycobacterium)
Nonspecific granulomatous
Granuloma secondary to prostatic surgery/resection
Granulomatous prostatitis secondary to systemic disease (e.g., Wegener)

Diagnosis of prostatitis is sometimes difficult to make and imaging is currently underutilized [4]. Imaging can aid in the diagnosis of prostatitis and its complications: transrectal ultrasound is the first imaging available worldwide, then CT and MRI may be used in particular cases. Only in selected cases, (such as prostatic abscess) color Doppler ultrasound may be required. Abdominal-pelvis CT and MRI may be indicated in severe infections to evaluate pelvic organs, associated pathologies, and/or upper urinary tract. Contrast-enhanced multiparametric magnetic resonance is indicated to study the prostate gland in men who have infection and harbor the high risk of associated malignancy [5]. Needle biopsy may be required mostly to rule out cancer only in selected cases with persistent PSA elevation and/or in cases with granulomatous prostatitis.

21.1 Acute Prostatitis

Acute prostatitis (AP) is often diagnosed on the basis of positive infectious culture, and it is usually associated with urinary tract bacterial infection. AP is diagnosed clinically and treated without specific imaging; anyway abdominal ultrasound is usually done to evaluate the kidney and upper urinary tract. The most frequently isolated pathogens are the following, E. coli, Proteus, Enterobacter, Klebsiella, and Pseudomonas, but sometimes it is not possible to identify any bacteria in urine or blood culture. Acute bacterial prostatitis appears in US as a hypoechoic rim around the prostate, and color Doppler shows an increased flow (Figs. 21.1 and 21.2).

Fig. 21.1

Acute prostatitis in the peripheral zone (small arrows) and anterior zone (big arrows)

Fig. 21.2

(b, c) Acute prostatitis: subcapsular hypoechoic rim (arrowheads) and fine hypoechoic linear septum (arrows) due to edema and ducts dilatation. (a) Color power Doppler shows an increased flow

21.1.1 Prostatic Abscess

Prostatic abscess is a complication of acute bacterial prostatitis frequently observed in patient with diabetes and immune weakness (Fig. 21.3). Prostatic abscess appears hypoechoic with well-defined or irregular wall that is typically associated with prostatitis and located in the anterior zone with well-defined borders. Color Doppler ultrasound reveals perilesional vascularity (Fig. 21.4). In contrast prostatic cancer is hypoechoic and typically located in the peripheral zone or heterogeneous ill-defined borders, and color Doppler reveals vascularity within the lesion. In large prostatic abscess, the fluid collection may extend over the prostatic capsule in the perirectal and retrovesical spaces. In these cases, abdominal contrast CT and MRI may be indicated to evaluate pelvic organs (Fig. 21.5). Also in severe infections or upper urinary tract infection, the CT is recommended.

Fig. 21.3

Prostatic abscess appears hypoechoic with irregular content (arrowheads), anechoic (arrow), and irregular wall (*) that are typically associated with acute prostatitis (arrowheads), located in the anterior and peripheral zone

Fig. 21.4

Prostatic abscess: color Doppler ultrasound reveals perilesional vascularity

Fig. 21.5

Prostatic abscess (ab) extending beyond prostatic capsule (pr) in the perirectal tissue at CT (a, b), TRUS (c, d), and the same case after 3 months follow-up after transperineal drainage (e, f longitudinal and axial view)

Ultrasound-guided drainage is very useful to further characterize the mass, may be useful to relieve symptoms and obtain bacterial culture, and therefore guides antibiotic therapy (Video). Transperineal echo-guided approach is preferred versus the transrectal approach since the rectal contamination is avoided. Furthermore, placement of drain is possible using the transperineal approach in patients with large cavity. Usually a small nephrostomy tube is left in place in the abscess cavity to flush saline solution and antibiotics [6]. Ultrasound monitoring is very useful to monitor abscess after treatment, to demonstrate residual or new fluid pockets after drainage, and to show location, size, and fluid content of the abscess during antibiotic treatment (Figs. 21.5 and 21.6).

Fig. 21.6

(a) Ultrasound monitoring of small prostatic abscess (*) after 14 days of antibiotic treatment (b) and 30 days (c)

Differential diagnosis between infected midline cyst and prostatic abscess is shown in (Fig. 21.7): well-defined borders of the cyst facilitate the diagnosis and differentiation from abscess, that is, irregular in shape and lobulated in borders.

Fig. 21.7

Differential diagnosis between infected midline cyst (a) with regular shape (arrows) and prostatic abscess (b) with irregular shape and lobulated borders (arrowheads)

21.2 Chronic Bacterial Prostatitis

The diagnosis of chronic forms relies on the presentation of pelvic or perineal pain, typically lasting for longer than 3 months after acute bacterial infection. The prevalence of prostatitis ranges between 5 and 11 % [2]. Prostatitis occurs at any age and its incidence increases with age. Chronic bacterial prostatitis is associated to BPH complication and urinary tract obstruction, urethral catheter, and urinary retention. Bacteria (most commonly Escherichia coli) invade the prostate by an ascending urethral infection, by reflux of infected urine into prostatic ducts, or by lymphatic/hematogenous spread. In chronic bacterial prostatitis, any characteristic ultrasound pattern can be detected. Color Doppler may detect diffuse increased enhancement of contrast; however, TRUS and contrast-enhanced color Doppler are not used in routine clinical practice since no studies regarding this issue have been performed. Prostatic calculi and hyperechoic areas should be described in the ultrasound report. Hyperechoic area that may be interpreted as post-inflammatory signature does not have posterior acoustic shadow compared to hyperechoic image linked to calculi (Fig. 21.8). The relationship between chronic prostatic inflammation, prostatic calculi, and infection was suspected in the past. Kim et al. [7] studied the relationship between inflammation and prostatic calculus and clinical parameters of benign prostatic hyperplasia in 225 patients. They showed that prostatic calculi had no significant association with chronic inflammation. Chronic inflammation was associated with the volume of the prostate and storage symptoms; thus, it is not only presumed to be related to the progression of BPH, but may also be one of the causes of lower urinary tract symptoms. This hypothesis was supported by Ficarra [8] that proposed the prostatic calculi as “marker” of chronic inflammation linked to BPH.