<prompt> Semen analysis of a young man who presented with primary infeility revealed low volume, fructose negative ejaculate with azoospermia. Which of the following is the most useful imaging modality to evaluate the cause of his infeility?Colour duplex ultrasonography of the scrotumTransrectal ultrasonographyRetrograde urethrographySpermatic venography  <response>: Sperms are produced in testes and then stored and mature within the epididymis. Vas deferens carries the sperms from epididymis to the urethra where they open by separate openings into the prostatic urethra. Just before opening each vas deferens is joined by ducts of seminal vesicles. Vas deferens and seminal vesicle ducts join to form the ejaculatory duct. The secretions of seminal vesicles form a large pa of seminal fluid and contain fructose and a coagulating enzyme called the vesiculase. Now coming to the question. Semen analysis forms an impoant pa of infeility assessment. Low ejaculatory volume is caused by retrograde ejaculation into the bladder or obstruction of the vas deferens or the ejaculatory duct Azoospermia may be seen in testicular failure or obstruction of vas deferens Absence of fructose suggests seminal vesicles agenesis or obstruction. A semen that is low in volume with azoospermia and absence of fructose suggests - either obstruction of the ejaculatory ducts or congenital absence of the vas deferens and seminal vesicles. The anatomy of the vas deferens seminal vesicles can be investigated by vasography where contrast medium is injected into the vas deferens or TRUS Trans rectal ultrasonography, however TRUS is superior to vasography and is the investigation of choice. Also know Semen specimen should be obtained following at least 3 days of abstinence and examined within 1 to 2 hrs. At least 2 specimens are examined several weeks apa. Ref : Smiths Urology 17e p691-709 