Structural Changes in the Subcutaneous Compartment in Morbid Obesity

Abstract

Most of the excess fat that accumulates in the morbidly obese is accommodated in the subcutaneous compartment (SCC), specifically in the adipose tissue lobules of the panniculus adiposus which enlarge and expand the SCC. However, the fibroelastic septa that are attached to the skin on one side of the SCC and to the deep fascia on the other invest each lobule and thereby offer resistance to the enlarging lobules. We report observations made during pathologic examinations of the abdominal wall SCC that were surgically excised by abdominal dermo-panniculectomy from 48 morbidly obese subjects after gastroplasty and weight loss. Lobules were large but varied notably upwards in size and, to some extent, shape. Simultaneously upon incision of the SCC, the lobules bulged above and the septa retracted below the same cut surfaces. Light microscopy revealed disruptions of septal elastic fibers, calcification of septa and septal arteries and necrosis of adipocytes, all sparsely distributed. Certain questions and facts emerge from these observations. Are the variations in lobule sizes normal, or do they reflect uneven fat deposition or mobilization during weight gain or loss respectively? Is there any correlation between lobule and adipocyte sizes? The tightly coupled phenomena of lobule-bulging and septal-retraction indicate that the lobules and septa are subjected to compressional and tensile stresses respectively in the intact, non-incised SCC. The histologic changes might be consequences of these stresses. Studies of the variations in body fat distribution and in adipocyte size have contributed to an understanding of obesity pathogenesis. The relevance of the present findings is unknown at this time, but these appear to have potential implications for studies of the morphogenesis of obesity. Confirmation of these findings, particularly the lobule variations, is required so that these can be compared with those in never-obese subjects and in morbidly obese subjects without prior weight loss.