Table 1.

Candidates for sperm retrieval, grouped according to the type and etiology of azoospermia.

Obstructive Azoospermia	Non-obstructive Azoospermia (Testicular Failure)
Congenital Ductal Obstructions:	Congenital Testicular Failure:
Congenital bilateral absence of the vas deferens	Testicular dysgenesis/cryptorchidism
Young's syndrome (clinical triad of chronic sinusitis, bronchiectasis, and obstructive azoospermia)	Genetic abnormalities (Klinefelter syndrome, Y chromosome microdeletions*)
Stenosis or atresia of the ejaculatory ducts	Germ cell aplasia (Sertoli cell-only syndrome)
Midline prostatic cysts (utricular and Müllerian cysts)	Spermatogenic (maturation) arrest
Ejaculatory duct cysts
Seminal vesicle cysts
Acquired Ductal Obstructions:	Acquired Testicular Failure:
Post-infection (epididymitis, prostatitis, seminal vesiculitis)	Testicular trauma
	Testicular torsion
Post-vasectomy	Post-inflammatory (e.g., mumps orchitis)
Post-surgical (epididymal cysts, hernia repair, scrotal surgery, bladder neck surgery, prostatectomy)	Exogenous factors (steroid medications, cytotoxic drugs, irradiation, heat)
Iatrogenic (urologic endoscopic instrumentation)	Systemic diseases (liver cirrhosis, renal failure)
	Testicular tumor
	Varicocele
	Post-surgical (surgeries that may compromise testicular vascularization, resulting in testicular atrophy)
Idiopathic:	Idiopathic (unknown etiology)
Idiopathic epididymal obstruction

^*The likelihood of obtaining sperm at sperm retrieval is virtually zero when complete AZFa and/or AZFb Yq microdeletions are found.