Agenesis of the ductus deferens is a rare cause of infertility or subfertility and can be associated with cystic fibrosis or unilateral renal agenesis.

Terminology

The term vas deferens is still widely used and is synonymous with ductus deferens. The plural of ductus deferens is ductus deferentes.

Epidemiology

Bilateral absence occurs in about 0.1% of all males, but 98% of males with cystic fibrosis ¹. The seminal vesicles are also absent in about 50%.

Up to 40% of unilateral ductus agenesis may be associated with ipselateral renal agenesis and up to 10% of bilateral ductus agenesis may be associated with a single kidney ².

Diagnosis

Azoospermia or hypospermia (<1 ml) are typical and are associated with an acid pH, especially if the seminal vesicles are absent. If the underlying cause is cystic fibrosis, genetic analysis may reveal a CFTR mutation.

On palpation the intra-scrotal portion of the ductus deferens is absent.

Clinical presentation

Patients are subfertile or infertile depending on whether one or both ducts are absent. About 7% of cases of obstructive azoospermia are due to bilateral absence of the ductus deferens ³.

Other patients may present with respiratory symptoms due to underlying cystic fibrosis.

Pathology

Advances in genetic testing have revealed strong links with cystic fibrosis varying with race, up to 78% for bilateral agenesis and 46% for unilateral agenesis ⁴. These cases could be considered to be a genital form of cystic fibrosis. There are more than 50 known cystic fibrosis mutations.

For those with unilateral renal agenesis, the genetics are not yet known.

Development of the epididymis and seminal vesicles may also be affected.

Radiographic features

Scrotal US can confirm the absence of the ductus deferentes and assess the epididymides for aplasia or hypoplasia. The seminal vesicles are best assessed by transrectal ultrasound or MRI, and the kidneys by US, CT or MRI.

Treatment and prognosis

Azoospermic males can be offered surgical sperm retrieval for in-vitro fertilisation.

Those with CFTR mutations require management of respiratory disease, which can vary widely in severity. They and their partners should also receive genetic counselling.

Those patients with unilateral renal agenesis will have normal life expectancy if the single kidney is normal.

Differential diagnosis

Primary ciliary dyskinesia can also cause infertility and bronchiectasis.

Practical points

Radiology trainees are most likely to encounter this condition in their exams and should know the points of difference between cystic fibrosis and primary ciliary dyskinesia as causes of infertility or subfertility.