Benign prostate hyperplasia is hyperplasia of the transitional zone of the prostate gland. On EU, BPH usually shows indentation on the urinary bladder base and, sometimes, elevation of the urinary bladder base away from the symphysis pubis as well as hooking appearance of the most distal segment of the ureter by elevation effect. However, the distinction of the transitional zone and central zone of the prostate gland could not be clearly shown on images. Thus, the transitional and central zones of the prostate gland are named as “central gland” even on computed tomography (CT) or magnetic resonance imaging (MRI). On CT, the central gland is occasionally distinguishable from the peripheral zone after contrast medium administration by its higher density. BPH usually shows an enlarged prostate gland with its central part protruding into the urinary bladder showing a smooth outline. The similar density of the intravesicular protruding part with visible contiguity with the central gland of the prostate gland on CT could make the diagnosis of BPH confident. On magnetic resonance image (MRI), the anatomical differentiation of the central gland from the peripheral zone is best identified on T2-weighted image (T2WI) by the surgical capsule showing a dark line. Sagittal or coronal T2WI of MRI could clearly delineate the anatomical relationship of the intravesicular protrusion of the enlarged central gland of the prostate and thus suggest the diagnosis of BPH.

Prostate TB could appear as prostate abscess with or without calcifications on images. If prostate abscess is associated with calcifications on images, prostate TB should be taken into consideration first [1]. On the other hand, in the absence of concurrent prostate calcification, it may not be possible to differentiate prostate TB abscess from prostate pyogenic abscess by prostate imaging findings alone. However, prostate TB often comes from upper urinary tract TB. Thus, the presence of renal or ureteral TB findings in addition to prostate abscess may imply the diagnosis of prostate TB.

Tuberculosis (TB involvement of the seminal vesicles leads to TB abscess formation, calcifications, and caseous necrosis. Therefore, TB involvement of the seminal vesicles appears as calcification and abscess formation with variable degrees of dirty adjacent fat on computed tomography (CT) [1]. On seminal vesiculography, the caseous materials by TB become filling defects in seminal vesicles. Nonetheless, in the absence of calcification of the seminal vesicles, the imaging appearance of abscesses of the seminal vesicle by bacteria or TB infection could be similar and lack clear distinction [1]. In contrast, abscess in the seminal vesicles with calcifications or concurrent findings of TB involvement on other sites including prostate or urinary tract should alert the readers of the possibility of TB infection.

TB orchitis usually occurs with epididymitis at the same time [2]. Unilateral TB epididymo-orchitis is more common than bilateral diseases [2]. TB epididymo-orchitis appears as intratesticular focal or diffuse low-echogenicity areas with epididymal involvement on ultrasound (US) [2]. US findings of TB epididymo-orchitis are nonspecific. Nonetheless, pyogenic orchitis usually has more blood flow than TB orchitis. Since male genital TB usually results from renal TB via infected urine, most cases of genital TB have detectable renal TB lesions as well. Thus, imaging findings of renal TB in the presence of nonspecific scrotal US findings may support the diagnosis of TB epididymo-orchitis.

Magnetic resonance imaging (MRI) is better than computed tomography (CT) and transrectal ultrasound (TRUS) for localizing and local staging of prostate cancer. Prostate cancers in peripheral zones usually show low signal intensity areas or nodules on T2-weighted images (T2WI) of MRI [3]. In contrast, normal peripheral zone of the prostate gland shows high signal intensity on T2WI of MRI [3]. Diffusion-weighted image (DWI) and apparent diffusion coefficient (ADC) of MRI could also help in localizing prostate cancer by showing water restriction of prostate cancers [4]. If prostate cancers in peripheral zones do not abut the prostate capsule, confinement in the prostate gland of the tumors could be assured. When a prostate cancer abuts the prostate capsule, recognition of a normal dark line of prostate capsule on T2WI of MRI confirmed tumor confinement in the prostate gland.

Magnetic resonance imaging (MRI) is the best imaging modality for identifying and assessing extracapsular extension of prostate cancers. Other imaging modalities such as transrectal ultrasound and computed tomography are insensitive for this purpose. On MRI, the evaluation of presence or absence of extracapsular extension relies mostly on T2-weighed images with or without fat-suppression techniques [4]. Other pulse sequences of MRI could however provide complimentary information. The loss of normal dark line of prostate capsule at the site of prostate cancer on T2WI MRI suggests the prostate cancer at least abutting the prostate capsule with possible extracapsular extension. Nonetheless, a gross extra-prostate mass, triangular appearance, irregular surface, large bulging appearance, and loss of prostate-rectal or prostate-seminal angle suggest the diagnosis of extracapsular extension on MRI [3–5]. When extracapsular extension of prostate cancer is present, it would have neurovascular bundle involvement at the same time. The right neurovascular bundle is located at the right posterior-lateral aspect of the prostate gland, so-called 5 o’clock location, and the left neurovascular bundle, at the left posterior-lateral aspect, 7 o’clock location. If the neurovascular bundle is not involved by the tumor, several small dots and nodules with some surrounding fat could be recognized in the expected positions mentioned above. On the other hand, extracapsular extensions of prostate cancer in either 5 or 7 o’clock location with loss of normal visualization of neurovascular bundles suggest tumor invasion upon MRI. The use of endorectal coils in MRI provides better signal to noise ratio in recognizing prostate capsule and neurovascular bundles [5]. Nonetheless, some patients could not tolerate the inserted endorectal coils despite of its theoretical advantages.

Normal seminal vesicles appear as tubules with smooth wall having high signal intensity content (i.e., semen) on T2-weighted images (T2WI) of magnetic resonance image (MRI). When prostate cancer involves the seminal vesicles, the tumor part in the seminal vesicles would lose normal high signal intensity appearance and is replaced by low signal intensity area on T2WI [3]. The remaining normal part of seminal vesicles would however keep the high signal intensity appearance on T2WI. Furthermore, the tumor invasion part of the seminal vesicles could also have heterogeneous contrast enhancement to highlight its presence on enhanced T1 fat-suppressed images. On the other hand, normal parts of the seminal vesicles have no contrast enhancements which enable their differentiation from the tumor invasion part of the seminal vesicles. Functional MRI such as diffusion-weighted image (DWI) and apparent diffusion coefficient (ADC) is helpful in identifying tumor invasion of the seminal vesicles and lymph node metastasis. Because malignant neoplasms usually restrict water diffusion, seminal vesicles and lymph nodes involved by prostate cancer could appear persistent high signal intensity on high-b-value DWI and low signal intensity on ADC, even of small sized lymph nodes.