background: The aim of this study was to estimate whether or not the size of an endometrioma is related to the thickness of the ovarian parenchyma inadvertently excised along with the cyst wall.methods: We performed a retrospective study including 35 women who had undergone endometrioma cystectomy, using an ovarian tissue sparing procedure. In total 38 specimens were studied by three pathologists as three women presented bilateral localizations, and all cyst diameters measured at least 30 mm. For each endometrioma, serial sections were performed, and on each section four different sites were randomly chosen to measure the thickness of glandular epithelium and stroma, of subjacent fibrosis, depending on the cyst, and of the ovarian parenchyma removed with the cyst. The diameter of the ovary was measured preoperatively either by MRI or ultrasound, and the area of the internal wall was then calculated. The relationships between the mean thickness of ovarian parenchyma removed and the variables were estimated and a multiple regression model identified independent predictors for ovarian parenchyma thickness.results: Adjacent ovarian tissue was found in 37 cases (97%). The mean thickness of ovarian tissue removed was 1173 + 711 mm and that of the cyst wall was 851 + 499 mm. The thickness of the ovarian parenchyma removed presented a direct proportional relationship with cyst diameter (P ¼ 0.015), and consequently with cyst wall area (P ¼ 0.032). This relationship with cyst diameter was independent after adjustment on other variables (P ¼ 0.032).conclusion: Endometrioma cystectomy even though performed with an accurate surgical technique leads to significant ovarian tissue removal, the thickness of which increases proportionally with cyst diameter.

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