Posttesticular or obstructive etiologies are associated with normal gonadotropin and testosterone levels and are present in up to 40% of azoospermic men (47,86). Ejaculatory dysfunction is associated with oligospermia or aspermia but rarely azoospermia (86). Obstructive causes include congenital absence or obstruction of the vas deferens or ejaculatory ducts, acquired obstruction of these ducts, or ductal dysfunction, including retrograde ejaculation (47,86). In the absence of congenital bilateral absence of the vas deferens (CBAVD) or hypogonadism, men with low volume ejaculate should have a postejaculatory urinalysis to check for retrograde ejaculation, which is associated with diabetes and surgery to the bladder or prostate (44,47). Sperm may be isolated from the neutralized urine of men with retrograde ejaculation and processed for insemination or for ART (30). Transrectal ultrasound may be of use to diagnose
Table 32.6 Genetics and Male Infertility
Congenital bilateral Cystic fibrosis F508, R117H 66 absence of vas (CFTR gene) deferens (CBAVD)
Nonobstructive Karyotype 47, XXY 15–30 azoospermia AZFa, AZFba, 10–15 AZFc
Severe (<5 M/mL) Karyotype 47, XXY 1–2 oligozoospermia Translocation 0.2–0.4 Y chromosome Partial AZFb, 7–10 microdeltions AZFc
CFTR, cystic fibrosis transmembrane conductance regulator; AZF, azoospermia factor. aAZFb the most severe (DAZ gene—deleted in azoospermia) causes the most severe defects of spermatogenesis; AZFc causes the mildest defects of spermatogenesis. From Hirsh A. Male infertility. BMJ 2003;327:669–672, with permission.
ejaculatory duct obstruction or unilateral vasal agenesis (to demonstrate contralateral atresia) but is generally not needed for CBAVD (86). Renal imaging is necessary when either unilateral or bilateral vasal absence is diagnosed as a result of the 10% to 25% incidence of renal agenesis. Most men with CBAVD will have seminal vesicle agenesis, so almost all will have low semen volume, low pH, and low fructose levels (86). Spermatogenesis can be expected to be normal in CBAVD, so generally diagnostic biopsy is not indicated (92). In some cases, testicular biopsy may be indicated to differentiate between testicular and posttesticular causes. At least two-thirds of men with CBAVD have mutations of the cystic fibrosis transmembrane conductance regulator gene (CFTR). However, because many CFTR mutations are undetectable, CBAVD patients should be assumed to have a mutation and thus testing of the female partner’s carrier status should be performed (86).