Objective: To evaluate the effects of different degrees of intratesticular hematoma (ITH), a major consequence of blunt testis trauma, on testis microstructure and function. We determined a cutoff point for significant vs nonsignificant ITH. Methods: Seventy male rats were divided into 7 equal groups. The control group remained intact. Sham groups consisted of rats given an intratesticular injection of normal saline in both testicles with volumes equivalent to 40% (group II), 30% (group III), and 10% (group IV) of testis volume. Bilateral ITH was created by the intratesticular injection of autologous blood equivalent to 40% (group V), 30% (group VI), and 10% (group VII) of testicular volume. After 60 days of recovery, testes volume, microstructure, semen parameters, and serum testosterone were recorded. Results: The most severe destructive effects were observed in groups V and VI. Testes, tubule, and epithelium volumes were reduced between 16.6% and 58.8%. The number of the spermatogenic, Sertoli, and Leydig cells was reduced between 47.5% and 73.1% in group V. Significant volume-dependent decreases in spermatozoa counts were seen in all groups except group IV after injection of different amounts of normal saline or blood. This reduction was most prominent after injections equivalent to 40% of testis volume (groups II and V). There was a nonsignificant trend toward lower testosterone level in groups V and VI. Conclusion: ITH has significant volume-dependent detrimental effects on testis microstructure, semen parameters, and testosterone level. ITH equivalent to 10% of testis volume may be relatively well-tolerated, but the effects can be significant when ITH is ≥30% of testis volume.
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