Last revised by Daniel J Bell on 31 Aug 2021

Azoospermia refers to complete absence of sperm in the semen. It accounts for 5-10% of male infertility 1.

It can be obstructive or non-obstructive, e.g. primary testicular failure. This differentiation is of utmost importance, as obstructive azoospermia can be corrected by surgical intervention 1,2.

Sonographic features that may be present with azoospermia include:

  • ectasia of rete testes: anechoic tubular structures in mediastinum testes
  • tubular ectasia of epididymis: multiple anechoic tubular structures in epididymal head (the differential for this feauture includes spermatocele, epididymal cyst)
  • inflammatory epididymal mass: enlarged heterogenous epididymis head
  • testicular volume: small sized testes (<7 mL) is seen in primary testicular failure. However, testicular volume is usually larger (>13 mL) in obstructive azoospermia 2.

Sonographic features that may present on transrectal ultrasound include:

  • absence of ductus deferens
  • dilated ductus deferens (diameter >1.5 mm) 
  • hypoplastic seminal vesicles (transverse diameter <7 mm and length <16 mm) 2,3
  • dilated seminal vesicles (transverse diameter >15 mm and length >25 mm) 2,3
  • inflammatory cyst(s) in ejaculatory duct

Vasography (vasculodeferentography) has rare application now, however, theoretically stays the gold standard to evaluate obstructive azoospermia.

Similar features like absence or ductus deferens or seminal vesicle can be seen on MRI. Epididymal and seminal vesicle cysts can also be well seen. Endorectal MRI is the preferred modality.

Patients with primary testicular failure (non-obstructive azoospermia) benefit from intracytoplasmic sperm injection. Obstructive azoospermia patients benefit from surgical correction such as vasoepididymostomy. Also, we can obtain sperm directly from epididymis or seminal vesicle, in cases of obstructive azoospermia.

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Cases and figures

  •  Case 1: ejaculatory duct obstruction
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