What are the differential diagnoses and management approaches for gastric outlet obstruction secondary to an antral mass?

Differential Diagnoses for Gastric Outlet Obstruction Secondary to Antral Mass

The most common cause of gastric outlet obstruction from an antral mass is gastric adenocarcinoma, but the differential must include pancreatic cancer with duodenal invasion, gastric lymphoma, duodenal/ampullary neoplasms, and less commonly cholangiocarcinoma or gallbladder cancer with extrinsic compression. 1, 2, 3

Primary Malignant Causes

Gastric Adenocarcinoma

• Antral carcinoma accounts for approximately 15% of all gastric outlet obstruction cases and represents the most common primary gastric malignancy causing obstruction 3
• Presents with progressive dysphagia, postprandial vomiting, early satiety, and weight loss 1, 2
• Diagnosis requires upper endoscopy with multiple biopsies to confirm malignancy and assess resectability 4

Pancreatic Adenocarcinoma

• Locally advanced pancreatic cancer is one of the two most frequent causes of malignant gastric outlet obstruction, along with gastric cancer 1, 2, 5
• Typically involves the head of pancreas causing extrinsic compression or direct invasion of the duodenum 1, 3
• Accounts for approximately 6% of gastric outlet obstruction cases in some series 3

Gastric Lymphoma

• Can present as an antral mass causing obstruction 2
• Requires tissue diagnosis via endoscopic biopsy to differentiate from adenocarcinoma 4
• Treatment approach differs significantly from adenocarcinoma, making accurate diagnosis critical

Other Malignancies

• Duodenal or ampullary neoplasms can cause obstruction at the level of the pylorus or proximal duodenum 1, 2
• Cholangiocarcinoma (particularly hilar tumors with recurrence) can cause gastric outlet obstruction through tumor mass effect in the antral region 6
• Gallbladder and bile duct cancers are less frequent causes 2
• Retroperitoneal lymphadenopathies from metastatic disease can cause extrinsic compression 2

Benign Causes (Less Likely with Antral Mass)

While the question specifies an antral mass suggesting malignancy, consider:

• Cicatrizing chronic duodenal ulcer (accounts for 65.7% of all gastric outlet obstruction but typically presents without a discrete mass) 3
• Severe peptic ulcer disease with pyloric stenosis 3

Diagnostic Algorithm

Initial Assessment

• Obtain complete blood count for anemia (suggesting chronic bleeding from malignancy) and leukocytosis 4
• Check comprehensive metabolic panel for electrolyte abnormalities (hypochloremic, hypokalemic metabolic alkalosis from vomiting) and renal function 4
• Measure serum bicarbonate, arterial pH, and lactate to exclude intestinal ischemia 4

Imaging Studies

• CT scan with oral and IV contrast is essential to determine location, cause, and extent of obstruction, assess for metastatic disease, and evaluate resectability 4
• CT helps differentiate between primary gastric tumor versus extrinsic compression from pancreatic or other malignancies 1
• Assess for ascites, peritoneal carcinomatosis, and liver metastases which impact treatment decisions 4

Endoscopic Evaluation

• Upper endoscopy is mandatory to visualize the obstruction, obtain multiple biopsies for histologic diagnosis, and assess feasibility of endoscopic intervention 4, 7
• Endoscopy differentiates intrinsic mucosal lesions from extrinsic compression 1
• Endoscopic ultrasound may be valuable for staging depth of invasion and evaluating extrinsic masses 2, 5

Management Based on Diagnosis

For Resectable Disease

• Surgical resection remains the treatment of choice when curative resection is feasible 2
• Neoadjuvant chemotherapy may be considered for locally advanced but potentially resectable disease 1

For Unresectable/Metastatic Disease

Patients with life expectancy >2 months who are surgically fit should undergo surgical gastrojejunostomy (preferably laparoscopic approach) 1, 4, 7

• Provides more durable symptom relief with lower reintervention rates compared to stenting 1, 7
• Laparoscopic approach preferred over open due to lower blood loss and shorter hospital stay 1

Patients with life expectancy <2 months or poor surgical candidates should receive endoscopic self-expanding metal stent (SEMS) placement 1, 4, 7

• Allows faster resumption of oral intake and shorter hospital stays 1, 7
• Antral location is associated with significantly lower stent efficacy (29.4% success) compared to duodenal location (70.2% success) 8

EUS-guided gastroenterostomy is an emerging alternative that combines minimal invasiveness with durable results 2, 5

• May be considered in centers with appropriate expertise 1

Contraindications to Stenting

• Do not place enteral stents in patients with multiple luminal obstructions or severely impaired gastric motility due to limited benefit 1, 4
• Consider venting gastrostomy for symptom relief in these patients 1, 4, 7

Critical Pitfalls

• Drain ascites before venting gastrostomy placement to reduce infectious complications 1, 4
• Severe uncontrolled pain after stent placement requires immediate endoscopic stent removal 1, 4, 7
• Poor nutritional status, ascites, and poor functional status predict surgical gastrojejunostomy failure 1
• Antral stent location has markedly worse outcomes than duodenal stenting 8