Intolerance to a fatty diet is one of the conditions of postcholecystectomy syndrome (PCS), a collective term for abdominal symptoms such as abdominal pain and dyspepsia that occur after surgery in patients with a history of cholecystectomy. Abdominal pain or “dyspepsia” (a feeling of fullness in the upper abdomen or right upper abdomen, abdominal rumbling, nausea, vomiting, constipation, fat intolerance, or diarrhea) occurs within a few weeks after surgery in half of PCS patients, and within months or years after surgery in the other half. These symptoms are nonspecific and vary depending on the underlying etiology, but often include pain in the right upper abdomen or epigastrium, most often after meals, and are sharp. So, what etiology can cause a patient to be intolerant to a fatty diet? The following is a brief description: “post-cholecystectomy syndrome” is limited to anatomical and physiological disturbances of the extrahepatic bile ducts that continue or are new after biliary surgery. Cholecystitis can be cured in 90-95% of patients after cholecystectomy, but in a minority of patients, symptoms can persist or recur, and some patients develop new symptoms that are inconsistent with their preoperative complaints, showing that not all of these conditions are due to cholecystectomy. The vast majority of PCS is due to preoperative diagnostic errors, i.e. symptom onset not due to biliary disease, and in some cases disease of adjacent organs (bile duct, liver, pancreas, duodenum) can produce the same symptoms as preoperatively, although of course postoperative symptom relief is unlikely. Most of the stones after cholecystectomy occur because the intraoperative investigation is not careful, and the tiny stones falling into the common bile duct from the cystic duct are not detected. The other case is due to careless surgery or unavoidable complications of the surgery itself. In most cases, common bile duct stenosis is not detected due to blunt intraoperative injury to the common bile duct, and is only detected when PTC or ERCP is performed after the onset of symptoms. Sclerosis and stricture of the duodenal papilla and sclerosis and stricture of the pancreatic duct and episodes of pancreatitis may be due to damage to the sphincter of Oddi by forcing a metal probe through the papilla during duodenal and common bile duct dissection. Injury can also lead to chronic inflammation due to cholesterol deposition in the terminal bile duct mucosa. The incidence of PCS is not significantly related to: gallbladder function as demonstrated on oral cholecystography; the size and number of stones in the gallbladder; and cholecystitis without stones. In recent years, the diagnosis of these diseases has been clarified because the diagnosis is more accurate and better than before. There are a number of PCS in category 2, the cause of which has not been clarified. Recent studies have shown that the bile duct wall of PCS patients is particularly sensitive to changes in pressure, and as soon as 1 to 2 ml of saline is injected into the common bile duct, the biliary pressure increases rapidly and severe pain occurs. In patients with bile reflux prior to cholecystectomy, the postoperative appearance of increased reflux may be related to pyloric sphincter dysfunction. In addition, persistent pain in PCS may be related to psychological factors and sometimes the possibility of intestinal adhesions or scarring of the gallbladder bed should be considered.