Nomogram for predicting the feasibility of natural orifice specimen extraction after laparoscopic rectal resection

Background and Aim The goal of this study was to develop a preoperative nomogram for predicting the feasibility of trans-anal natural orifice specimen extraction (NOSE) for rectal cancer. Methods The analysis included 201 patients who underwent trans-anal NOSE and 457 patients who failed to undergo trans-anal NOSE in Shanghai East Hospital. The data collected included age, gender, body mass index, presence of tumor obstruction, distance from anal verge; maximum tumor diameter and anteroposterior thickness of mesorectum (AP) measured by magnetic resonance imaging; interspinous diameter, intertuberous diameter (IT), anteroposterior diameter of the inlet (API), anteroposterior diameter of the midplane, anteroposterior diameter of the outlet (APO), sacral length and pelvic depth (PD) measured by computed tomography. Results The multivariate analysis suggested that a lower body mass index (P < 0.001), no tumor obstruction (P = 0.005), a shorter distance from anal verge (P < 0.001), a smaller tumor size (P < 0.001), a thinner AP (P < 0.001), a wider and shallower bony pelvis (API/PD, P < 0.001), and a wider and shorter pelvic outlet (IT/APO, P < 0.001) were significantly associated with an increased probability of trans-anal NOSE. Successful NOSE patients had a decreased time to liquid intake (P < 0.001), a shorter postoperative hospital stay (P < 0.001), and fewer wound infections (P = 0.045). No significant difference in the rate of mortality or recurrence was observed. The nomogram model presented an area under the receiver operating characteristic curve of 0.81 (95% CI, 0.78 to 0.85) and good calibration. Conclusion We developed a nomogram model that has some predicative value for the feasibility of laparoscopic rectal resection with trans-anal NOSE, utilizing clinical and radiologic parameters, available in most institutions.