Beyond complications: the mayo adhesive probability (MAP) score as an imaging biomarker of surgical complexity in percutaneous nephrolithotomy.

The Mayo Adhesive Probability (MAP) score was originally developed to predict adherent perinephric fat in partial nephrectomy. Its role in percutaneous nephrolithotomy (PNL) remains poorly characterized. We aimed to investigate whether MAP score is associated with markers of procedural difficulty and perioperative outcomes in patients undergoing PNL. We retrospectively evaluated 556 consecutive adult patients who underwent PNL between 2020 and 2025. MAP scores were calculated using preoperative non-contrast computed tomography and patients were categorized into low-MAP (< 3) and high-MAP (≥ 3) groups. Procedural difficulty markers included prolonged operative time (> 120 min), multiple access tracts (≥ 2), postoperative hemoglobin decrease ≥ 2 g/dL, residual stone fragments > 4 mm, secondary intervention, tubeless drainage, and trifecta failure. Trifecta failure was defined as the presence of residual stones, postoperative complications, or need for secondary intervention. Multivariable logistic regression analyses were adjusted for age, sex, stone size, stone density, Guy's score ≥ 3, hydronephrosis grade, and skin-to-stone distance. Among 556 patients, 310 had MAP scores < 3 and 246 had MAP scores ≥ 3. Patients with MAP ≥ 3 had significantly longer operative times (107.8 ± 47.7 vs. 97.7 ± 38.0 min, p = 0.007), greater hemoglobin decrease (2.17 ± 1.22 vs. 1.67 ± 1.07 g/dL, p < 0.001), higher rates of multiple access tracts (18.7% vs. 9.7%, p = 0.003), residual stones (35.0% vs. 22.6%, p = 0.002), Clavien-Dindo grade ≥ II complications (26.0% vs. 17.4%, p = 0.018), and trifecta failure (44.3% vs. 29.8%, p < 0.001). On multivariable analysis, MAP ≥ 3 independently predicted prolonged operative duration (OR 1.82, 95% CI 1.12-2.94, p = 0.015), hemoglobin decrease ≥ 2 g/dL (OR 2.42, 95% CI 1.62-3.60, p < 0.001), residual stones (OR 1.79, 95% CI 1.17-2.75, p = 0.007), trifecta failure (OR 1.75, 95% CI 1.17-2.61, p = 0.006), and Clavien-Dindo grade ≥ II complications (OR 1.43, 95% CI 1.05-2.17, p = 0.008). MAP score was not independently associated with secondary intervention, tubeless drainage, or overall postoperative complications. A high MAP score is independently associated with several markers of procedural difficulty during PNL, including prolonged operative time, clinically significant bleeding, residual stones, trifecta failure, and clinically relevant complications. These findings suggest that MAP score may function as an imaging biomarker of procedural burden and may complement existing stone-complexity scoring systems in preoperative risk stratification.