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.