Whole-Body Transformation in Obese Patients Undergoing Metabolic Surgery: Insights From Automated Multiorgan...

This study assesses whether automated segmentation allows evaluation of subtle changes in volume and intrinsic tissue characteristics in an obese patient population undergoing metabolic surgery.

Multiorgan segmentation and intrinsic Hounsfield Unit (HU) analyses were performed in 1877 preoperative/postoperative computed tomography (CT) examinations, processing nine compartments, organ systems, and musculoskeletal structures as follows: subcutaneous, peritoneal/retroperitoneal fat, skeletal muscle and liver, spleen, kidneys, pancreas, and first lumbar vertebral body. Statistical assessments utilized Wilcoxon signed-rank test and generalized linear mixed model comparisons successively using volumes and HU as dependent values, preoperative/postoperative state as fixed factor, and gender, age as covariates.

Metabolic surgery led to significant reductions of subcutaneous, retroperitoneal/peritoneal fat volumes averaging 25% and 29%, respectively, p<0.001. Subcutaneous and retroperitoneal/peritoneal fat compartments differed significantly in HU, p<0.001. Postoperative reduction in fat tissue was accompanied by a significant increase in corresponding median HU, increasing by 6% and 8%, respectively, p<0.001. Volumes of liver, spleen, pancreas, and kidneys were significantly impacted by metabolic surgery with intraindividual shrinkages of 7-11% postoperatively, p<0.001. Core striated musculature showed significant decreases in volume, averaging 4%, and a simultaneous significant increase in HU following metabolic surgery, averaging 4%. Throughout, gender was a significant covariate with larger volumes preoperatively, a more substantial volume loss postoperatively, as well as a higher HU increase, all observed in males.

Simultaneously, operator-independent and automated compartmental quantitative segmentation allows for assessment of subtle changes in volume and intrinsic structural tissue characteristics over time in patients undergoing metabolic surgery. Our results underline the complex transformation of fat, organs, and muscles after surgery-induced weight loss.