Objective: The aim of this study was to measure the diameter of seminiferous tubules (ST) during microdissection testicular sperm extraction (TESE) using a micrometer fixed to one of the eyepieces of the operating microscope to find a correlation between the extracted ST diameter and TESE outcome.
Design: A prospective comparative study.
Setting: Adam International Andrology and Infertility Clinic, Giza, Egypt.
Patient(s): Two hundred sixty-four patients with nonobstructive azoospermia (NOA) were included.
Intervention(s): Patients underwent TESE using the open surgical technique. The STs were measured using the micrometer, and the tubule with the largest diameter was excised and freshly examined under an inverted microscope. If no spermatozoa were found, another sample was taken from the second most dilated tubule area and then at random until sperm were found or a maximum six samples were harvested. If no spermatozoa were detected, the contralateral testis was operated upon.
Main outcome measure(s): The TESE outcome in relation to ST diameter.
Result(s): The total sperm recovery rate was 105 out of 264 (39.8%). When ST measured >or=300 microm the sperm retrieval rate was 16 out of 19 (84.2%). When ST diameter was <300 microm, the sperm retrieval rate was 36.3% (89 out of 245).
Conclusion(s): During microdissection TESE, the best cutoff level of the ST diameter for harvesting testicular spermatoza is 110 microm with sensitivity 86.0% and specificity 74.4% (AUC 0.653, 95% confidence interval 0.608-0.663). When ST diameter is 300 microm or more a single tubule biopsy is usually sufficient to harvest enough testicular spermatozoa for intracytoplasmic sperm injection or sperm freezing with minimal tissue excision.