Screening for the cystic fibrosis transmembrane conductance regulator (CFTR) gene should be performed on all men with congenital bilateral absence of the vas deferens (CBAVD). CBAVD is found in nearly all men with
cystic fibrosis, and a large percentage of men with CBAVD carry the mutated CFTR gene. CBAVD is the most common cause of obstructive azoospermia. CBAVD is diagnosed by physical examination and does not require a scrotal ultrasound or vasogram.