We investigated the prognostic importance of noninvasive factors in predicting sperm retrieval failure in idiopathic nonobstructive azoospermia (iNOA). We studied 193 patients with nonobstructive azoospermia who underwent microsurgical testicular sperm extraction. The Chi-square test and Mann–Whitney U tests for clinical parameters and seminiferous tubule distribution were used for between-group comparisons. A logistic regression analysis was conducted to identify predictors of retrieval failure. Area under the receiver operating characteristic curve for each variable was evaluated, and the net clinical benefit was calculated using a clinical decision curve. Patients with iNOA had a lower sperm retrieval rate than those with known causes. Moreover, testicular volume was an independent factor affecting sperm extraction outcomes (odds ratio = 0.79, P < 0.05). The testicular volume cut-off value was 6.5 ml (area under the curve: 0.694). The patients with iNOA were categorized into two groups on the basis of the distribution of seminiferous tubules observed. The sperm retrieval rate and testicular volume were significantly different between the groups with a uniform or heterogeneous tubule distribution. There was also a significant association between a uniform tubule distribution and testicular volume. In conclusion, a testicular volume of more than 6.5 ml effectively predicts microsurgical testicular sperm extraction failure due to a uniform tubule distribution in patients with iNOA.

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