The patient was a k/c/o operated periampullary Ca with recurrence.That explains the pneumobilia due to incompetent sphincter of  Oddi secondary to operation and gastric outletobstruction is due to recurrence.

                                                Gastric outlet obstruction
Gastric outlet obstruction (GOO) is not a single entity; it is the clinical and pathophysiological consequence of any disease process that produces a mechanical impediment to gastric emptying. Inflammation, scarring, or infiltration of the antrum and pylorus are associated with the development of GOO.

Within the pediatric age group, pyloric stenosis constitutes the most important cause of GOO. Pyloric stenosis occurs in 1 per 750 births. It is more common in boys than in girls and also is more common in first-born children. Pyloric stenosis is the result of gradual hypertrophy of the circular smooth muscle of the pylorus.

The major benign causes of GOO are PUD, gastric polyps, ingestion of caustics, pyloric stenosis, congenital duodenal webs, gallstone obstruction (Bouveret syndrome), pancreatic pseudocysts, and bezoars.

Duodenum is intimately related to the gallbladder, liver, and pancreas; therefore, a malignant process of any adjacent structure may cause outlet obstruction due to extrinsic compression.

Pancreatic cancer is the most common malignancy causing GOO. Outlet obstruction may occur in 10-20% of patients with pancreatic carcinoma. Other tumors that may obstruct the gastric outlet include ampullary cancer, duodenal cancer, cholangiocarcinomas, and gastric cancer. Metastases to the gastric outlet also may be caused by other primary tumors .An enlarged stomach with a narrowing of the pyloric channel or first portion of the duodenum helps differentiate GOO from gastroparesis

Gastrojejunostomy remains the surgical treatment of choice for GOO secondary to malignancy

 

                                                                PNEUMOBILIA

The causes of pneumobilia include an incompetent Sphincter of Oddi (e.g. post sphincterotomy, or following passage of a gallstone), gallstone ileus, trauma, a duodenal ulcer perforating into the common bile duct, and secondary to surgery (e.g. cholecystoenterostomy)

Another well-documented cause of pneumobilia is a surgically created anastomosis between the biliary tract and the bowel, the Whipple procedure, and choledocho-jejunostomy, endoscopic retrograde cholangiopancreatography with papillosphincterotomy or surgical transduodenal sphincteroplasty

When gas is observed in the lumen of the biliary ducts or gallbladder, it is necessary to distinguish emphysematous cholecystitis from a biliary enteric communication or an incompetent sphincter of Oddi. The demonstration of gas in the wall of the gallbladder confirms the diagnosis of emphysematous cholecystitis,while reflux of barium into the biliary tree would indicate a biliary enteric communication. The presence of pneumobilia in association with emphysematous cholecystitis suggests that the cystic duct is patent.

                                                                   PORTOMESENTERIC VEIN GAS

Portomesenteric vein gas is most commonly caused by mesenteric ischemia but may have a variety of other causes. The primary factors that favor the development of this pathologic entity are intestinal wall alterations, bowel distention, and sepsis.

The radiographic criterion for portal vein gas is a branching area of low attenuation extending to within 2 cm of the liver capsule.

At CT, portal vein gas appears as tubular areas of decreased attenuation in the liver, predominantly in the left lobe . These low-attenuation areas are caused by the accumulation of gas in the intrahepatic portal veins, from where it is carried by centrifugal blood to the hepatic periphery.

Intrahepatic portal vein gas must be differentiated from air in the biliary tree (pneumobilia). In the latter condition, the air is located centrally(ie, it does not extend to within 2 cm of the liver capsule) , and a confluence of air is seen in the common hepatic duct. Pneumobilia also has a left lobe predilection at CT because of its more ventral location. In contrast, collections of portal vein gas are smaller and more numerous and are seen in the liver periphery. However, it is possible for pneumobilia and portal v