Addressing the need for predictive tools in postoperative abdominal wall complications after nephrectomy - Evaluation of a novel abdominal bulge grading system using computed tomography.

Background: Abdominal bulging affects up to one-fourth of patients after flank incision, with half experiencing impaired quality of life. Identifying patients at risk for morbid bulge could improve preventive and supportive care. Purpose: To characterise muscular changes related to postoperative abdominal bulging and design a visual scoring system to grade bulge on postoperative CT scans. Material and Methods: Patients treated with open partial nephrectomy via a flank incision between 2005 and 2016 at the University Hospital of Umeå were included. Pre- and postoperative CT scans of the first 50 consecutive patients were used to characterise imaging features of the postoperative abdominal wall. From these features, a four-tiered scoring system for abdominal bulge was designed. Two independent observers tested the system on CT scans from the 50 next patients. Inter-rater reliability was assessed using Fleiss' Kappa. Results: Common features of abdominal bulging were extracted and a four-tier visual score ranging from normal abdominal wall to severe bulge was developed. Among the patients, ∼70% had a normal abdominal wall, ∼25% had bulge score 1, ∼7% score 2, and ∼1% score 3. Inter-rater agreement was 73.5%, with Fleiss' Kappa 0.44. Conclusion: Features of bulge were reduced muscle thickness and ipsilateral gravitational slump affecting part or all of the lateral abdominal wall. The proposed scoring system demonstrated only moderate inter-rater reliability in this pilot setting. Further research on postoperative abdominal wall changes is needed before implementing imaging-based assessments in clinical care.