Perioperative Hemoglobin Decline After Deep Endometriosis Surgery: Association with Surgery Duration and Exploratory Analyses of Operative Extent

Background/Objectives: Deep endometriosis surgery may require bowel and multiorgan procedures, but reported blood loss and complications do not fully characterize postoperative hemoglobin decline, a relevant consideration for patient blood management. We aimed to quantify the frequency of a hemoglobin decline of ≥3 g/dL and its association with surgery duration, with secondary exploratory analyses of operative extent. Methods: This retrospective single-center study in Opole, Poland, linked registry and laboratory records for first eligible surgeries during 2020–2025. Decline was the last preoperative hemoglobin within 7 days minus the recorded nadir through postoperative day 3. The ≥3 g/dL threshold was operational, not a validated minimum clinically important difference. Multivariable models examined binary and continuous decline; exploratory analyses assessed operative extent. Results: Among 424 patients, preoperative hemoglobin was <12 g/dL in 41/419 (9.8%) and <13 g/dL in 152/419 (36.3%). Of 416 with both measurements, 156 (37.5%) met the endpoint, whose ascertainment depended on available recorded postoperative measurements. Each additional hour was associated with higher odds (odds ratio [OR], 1.61; 95% confidence interval [CI], 1.35–1.91), including without preoperative hemoglobin (OR, 1.50; 95% CI, 1.28–1.76). Continuous decline was 0.20 g/dL greater per hour (95% CI, 0.13–0.26). Among 379 patients with resection-multiplicity data, unadjusted endpoint frequencies were 14.5%, 38.3%, and 54.9% after no, one, and multiple full-thickness resections. Conclusions: Longer duration was associated with greater decline. Exploratory operative-extent gradients require prospective evaluation with standardized sampling before informing monitoring. Preoperative anemia remains relevant because the same decline produces a lower postoperative concentration.