Differential Diagnoses for Gastric Outlet Obstruction
Primary Malignant Causes
Malignancy is now the most common cause of gastric outlet obstruction in adults, accounting for approximately 60% of cases. 1
Most Common Malignant Etiologies:
- Antral gastric adenocarcinoma represents the most common primary gastric malignancy causing obstruction (approximately 15% of all GOO cases), presenting with progressive dysphagia, postprandial vomiting, early satiety, and weight loss 2
- Locally advanced pancreatic cancer (particularly head of pancreas) is one of the two most frequent causes of malignant GOO, causing extrinsic compression or direct invasion of the duodenum 2
- Gastric lymphoma requires tissue diagnosis via endoscopic biopsy to differentiate from adenocarcinoma, as treatment approaches differ significantly 2
- Duodenal or ampullary neoplasms can cause obstruction at the pylorus or proximal duodenum 2
- Peritoneal carcinomatosis from various primary malignancies 1
Benign Causes
Peptic Ulcer Disease-Related:
- Cicatrizing chronic duodenal ulcer historically was the most common cause (accounting for 55-65% in older series), but has dramatically decreased with widespread use of H2 blockers and proton pump inhibitors 1, 3, 4
- Pyloric channel ulcers with associated edema and scarring 5
Structural/Anatomic:
- Congenital hypertrophic pyloric stenosis (primarily pediatric population, 9.4% in some series) 4
- Congenital bands (rare, approximately 3% of cases) 4
Inflammatory:
- Crohn's disease with stricture formation 1
- Eosinophilic gastroenteritis 3
- Caustic ingestion with subsequent stricture 3
Other Benign Causes:
- Gastric polyps (large or multiple) 3
- Gastrointestinal stromal tumors (GIST) 3
- Bezoars causing mechanical obstruction 3
- Endometriosis involving the gastric outlet 1
Critical Diagnostic Pitfall
Benign peptic ulcer disease can mimic malignancy on imaging, showing irregular pyloric wall thickening with marked enhancement on contrast-enhanced CT and increased FDG uptake on PET/CT, making tissue diagnosis via endoscopic biopsy mandatory 5. Multiple biopsies should be obtained to exclude malignancy, as inflammatory changes can obscure underlying neoplasm 2.
Functional Causes to Exclude
While not true mechanical obstruction, gastroparesis and adynamic ileus can present with similar symptoms and must be differentiated from mechanical GOO through imaging and endoscopy 1. These conditions are caused by impaired gastric motility rather than anatomic obstruction and require entirely different management approaches 1.