Question: Maine Subscriber Answer: If your physician documents that the patient is eating but still losing weight, then yes, use 579.3 (Other and unspecified postsurgical nonabsorption). Otherwise -- for instance, if the patient has lost appetite -- use 783.21 (Loss of weight). Patients frequently have trouble digesting and absorbing their food after gastric surgery. The reduced size of the stomach causes inadequate mixing of food with digestive juices (579.3). Bacterial contamination in a cut-off "blind loop" in the small intestine (due to a gastroenterostomy) may cause maldigestion (579.2, Gastric surgery that allows food to enter into the upper small intestine with minimal digestion may reveal mild celiac disease (which, when severe, would merit 579.0,Celiac disease).