1417 Gastric Outlet Obstruction Caused by Infiltrative Pancreatic Cancer Mimicking Benign Peptic Ulcer Disease

Abstract

INTRODUCTION: Gastric outlet obstruction (GOO) is a known complication of peptic ulcer disease (PUD) and pancreatic cancer. Pancreatic cancer causing GOO can sometimes be missed on endoscopic ultrasound (EUS) due to limited access, thus presenting a diagnostic challenge. We report a case of pancreatic cancer causing GOO which was missed on EUS and GOO was attributed to the duodenal ulcers. CASE DESCRIPTION/METHODS: A 59-year-old man with medical history of diabetes and PUD presented with epigastric pain and persistent vomiting for last 2 months associated with weight loss. He had upper endoscopy 4 weeks prior that revealed multiple ulcers in second part of the duodenum. Exam was remarkable for epigastric tenderness. Laboratory data showed hypokalemic metabolic alkalosis and acute kidney injury. Liver function tests were normal. Considering patient's clinical presentation an underlying malignancy was high on differential. CT abdomen showed GOO with duodenal narrowing and a normal pancreas. Endoscopy showed duodenal bulb stricture which could not be traversed. Biopsy showed inflamed duodenal mucosa. EUS showed no pancreatic pathology. GOO was attributed to the duodenal ulcers noted on prior endoscopy and a Roux-en-Y gastrojejunostomy was performed. He returned 12 weeks later with painless jaundice and elevated liver enzymes. MRI abdomen revealed a 2.5 cm infiltrative pancreatic head tumor extending to the pancreaticoduodenal groove resulting in dilatation of the duodenal stump and bile duct. The patient underwent Whipple's pancreaticoduodenectomy. The histopathology showed pancreatic adenocarcinoma with distal involvement of the duodenal margin. DISCUSSION: Pancreatic cancer is the second most common malignancy causing GOO. EUS is the most sensitive diagnostic modality for pancreatic cancer with a sensitivity of 94%. However, its accuracy can be limited in setting of duodenal stricture and infiltrating type of the pancreatic lesion. The best station to evaluate the head and genu of the pancreas is second part of the duodenum. In case of duodenal stricture, EUS cannot be stationed properly and can miss an infiltrating pancreatic head lesion causing the GOO, which can be attributed to some other co-existent etiology like PUD, especially in the setting of normal liver tests and CT abdomen. This case also highlights the utility of MRI which is more sensitive than CT in diagnosing small pancreatic lesions and sometimes might be the only revealing modality in instances where EUS is limited by duodenal stricture.