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The vas deferens is seldom palpated during routine physical examination, though absence of the vas has important implications.
A man of 45 with moderate obesity came for routine vasectomy under local anaesthesia after an initial outpatient consultation at which no physical examination had been performed. The right vas was successfully ligated; the surgeon then explored the other side but had to abandon the operation because of persistent patient discomfort and inability to find the vas. At a second operation, performed under general anaesthesia, absence of the left vas was confirmed. An ultrasound scan subsequently demonstrated absence of the ipsilateral kidney.
John Hunter first described basence of the vas deferens in a cadaver in 17371, and an association with ipsilateral renal agenesis has been noted2,3. The reported prevalence of unilateral absence of the vas deferens is between 0.06% and 0.8%4,5. Unilateral renal agenesis is less common, with an estimated prevalence of 0.1%6. However, of patients with unilateral absence of the vas deferens, up to 80% have ipsilateral renal agenesis4. Even when the kidney is present, it may be affected by a wide range of anomalies such as ectopia, malrotation, fusion and polycystic disease. Abnormalities in the solitary contralateral kidney occur in nearly 10% of such patients, ranging from ureteric obstruction to vesicoureteric reflux4. In addition, ipsilateral absence of the adrenal gland has been reported in 15-25% of patients with renal agenesis7.
Developmentally the Wolffian duct, which ultimately forms the vas deferens, is derived from the mesonephric duct. The ureteric bud which likewise develops from the mesonephric duct forms the ureter, renal pelvis, calyces, and collecting tubules. Thus congenital absence of the Wolffian duct precludes formation of a ureteric bud and results in renal agenesis. As in the case presented, the testicle is usually present in patients with a congenitally absent vas, since the testis is derived from the genital fold and not the mesonephric duct.
This case highlights the difficulties which may result from a congenitally absent vas deferens during vasectomy, which is increasingly performed as a day-case ambulant procedure in family planning clinics. We recommend that, when the vas cannot be felt on one side, on clinical examination, the patient should undergo scrotal exploration under general anaesthesia, to allow a thorough search before the vas is declared congenitally absent. All such patients should have imaging of the renal tracts. Because of the association between congenital absence of the vas deferens and defects in the cystic fibrosis transmembrane conductance regulator gene, these patients should also undergo genetic cystic fibrosis screening8.
Absence of the vas deferens may be a useful warning sign in patients with blunt abdominal trauma requiring emergency surgery. Such patients should be assumed to have ipsilateral renal agenesis until proved otherwise.