Infertility affects ∼7% of all men. Despite much progress, mainly in genetics, its etiology remains obscure in ∼50% of cases. To fill this gap, imaging of the male genital tract (MGT) has progressively expanded, providing useful information in the assessment of MGT abnormalities.METHODS
A critical, systematic review of the available literature was performed using Medline, with no restrictions regarding date of publication (i.e. from inception date until March 2014), along with analysis of previous reports in color Doppler ultrasound (CDUS) atlas textbooks. Normal anatomy and sonographic characteristics of the MGT have also been summarized.RESULTS
Testicular volume (TV) is tightly associated with both sperm and hormonal parameters. Ultrasound (US) offers a greater accuracy in TV measurement than Prader orchidometer (PO). However US- and PO-derived TV are closely related, making PO-derived TV informative enough in the work-up of the infertile man in everyday clinical practice. US-derived TV might play an independent role in specific clinical conditions (i.e. large hydrocele, inguinal testis, enlarged epididymis). Scrotal US may detect signs of testicular dysgenesis, often related to an impaired spermatogenesis and to a higher risk of malignancy, or testicular lesions suggestive of malignancy. A decreased testis vascularization is characteristic of testicular torsion, whereas hyperemia is often observed in epididymo-orchitis or in some malignant conditions (i.e. lymphoma, leukemia). The impact of varicocele detection and surgical correction on sperm parameters/fatherhood is debated. At present, the clinical management of varicocele is mainly based on physical examination. However, CDUS is useful in assessing venous reflux, when palpation is unreliable and/or in detecting recurrence/persistence after surgery. Epididymis head and/or tail dilation is suggestive of MGT obstruction or inflammation and both are related, along with echo-texture abnormalities, to impaired sperm parameters. Scrotal and transrectal US (TRUS) are useful in detecting congenital uni- or bilateral absence of vas deferens (CBAVD), which may be associated with epididymis, seminal vesicles (SV) or kidney abnormalities/agenesis. TRUS plays a key role in assessing obstructive azoospermia and detecting distal CBAVD or anomalies related to ejaculatory ducts obstruction, such as ejaculatory duct abnormalities, prostate median cysts or SV enlargement/emptying impairment. TRUS findings lead to operational decision-making, such as testicular sperm extraction in the case of CBAVD, cyst aspiration in the case of a large prostatic median cyst, and surgical treatment if ejaculatory duct abnormalities are observed. TRUS may reveal prostate volume reduction (suggestive of hypogonadism) or enlargement, which can be related to aging or even metabolic abnormalities. Finally, TRUS may reveal prostate and SV echo-texture abnormalities suggestive of inflammation or SV stasis.CONCLUSIONS
MGT-CDUS is a useful tool in detecting abnormalities related to impaired male reproductive health. However, it suffers from a lack of standardization and often produces subjective/vague diagnoses. To fill this gap, the European Academy of Andrology has promoted an ongoing multicenter study aimed at defining the MGT-CDUS characteristics of healthy, fertile men.