Differential diagnosis of azoospermia and etiologic classification of obstructive azoospermia: role of scrotal and transrectal US.

Purpose: To evaluate the usefulness of scrotal and transrectal ultrasonography (US) in the differential diagnosis of azoospermia and the etiologic classification of obstructive azoospermia.

Materials And Methods: This study was approved by the institutional ethics committee, and all patients provided written informed consent. Between April 2006 and November 2008, 100 infertile men (mean age, 32 years; range, 22-51 years) with azoospermia were evaluated at scrotal and transrectal US, with an emphasis on abnormal US findings of the seminal tract and measurement of testicular volume. On the basis of the results of percutaneous epididymal sperm aspiration, testicular fine-needle aspiration cytology, or testicular biopsy, 97 patients with azoospermia were divided into obstructive or nonobstructive groups. The remaining three patients had Klinefelter syndrome and did not undergo testicular biopsy. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of different indexes for discrimination between obstructive and nonobstructive azoospermia. Cases of obstructive azoospermia were further classified according to obstructive causes.

Results: Seminal tract abnormalities were more common in obstructive (92.2% [59 of 64 patients]) than in nonobstructive (2.8% [one of 36 patients]; P < .001) azoospermia. Testicular volume was significantly larger for obstructive (median, 16.0 mL; range, 8.4-27.5 mL) than for nonobstructive (median, 8.6 mL; range, 0.9-21.0 mL; P < .001) azoospermia. The area under the ROC curve for discrimination between the groups through combined assessment of the seminal tract and testicular volume at scrotal and transrectal US was 0.96. Sensitivity, specificity, and accuracy for combined assessment in discriminating between obstructive and nonobstructive azoospermia were 95.3% (61 of 64 patients), 97.2% (35 of 36), and 96.0% (96 of 100), respectively.

Conclusion: Scrotal US and transrectal US are effective imaging modalities for distinguishing obstructive from nonobstructive azoospermia and can provide meaningful diagnostic information for determining the etiologic classification of obstructive azoospermia.