Gastric outlet obstruction
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:
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Overview
GASTRIC OUTLET OBSTRUCTION: Pyloric obstruction
Gastric outlet obstruction (GOO,) is the result of any pathology that provides mechanical obstruction to emptying of gastric contents. Two important causes of GOO include: Benign: 37 percent of cases, includes peptic disease Malignant: 53 percent of cases
Location of the stomach: Left upper quadrant of the abdomen Parts of the stomach: Cardia Body Antrum Pylorus
History History of PUD or its complications: Indigestion Anorexia nausea, vomiting epigastric pain
History of abdominal pain and weight loss in cases of pancreatic cancer
Clinical presentation: Nausea Vomitting: characteristic feature Intermittent Occurs one hour after ingestion Nonbilious Contains undigested particles of food Intolerance to solids, followed by liquids Dehydration Electrolyte abnormalities
Late stages: Weight loss Malnutrition: more pronounced in patients with malignancy Abdominal distension Features of incomplete obstruction: gastric retention: presenting as early satiety bloating fullness of epigastrium Aspiration pneumonia: due to dilatation of stomach, loss of contractility and accumulation of undigested food contents
Etiology
Benign causes:
Acquired: PUD: 5 % cases ( most commonly affecting pylorus and initial part of the duodenum): Acute- edema and inflammation Chronic- due to intrinsic obstruction as a result of fibrosis and scar formation Gastric polyps Caustic ingestion Obstruction by gallstones (Bouveret syndrome) Complication of acute pancreatitis: pancreatic pseudocyst formation bezoars
Congenital: Pyloric stenosis: most common cause in children more common in boys> girls due to hypertrophy of pyloric circular smooth muscles Congenital duodenal webs
Malignant causes- Malignancies involving neighbouring structures: Pancreas: Pancreatic cancer: most common malignancy leading to extrinsic obstruction of the pylorus, occurs in one fifth of patients Stomach: Gastric cancer Duodenum: Duodenal cancer Ampullary cancer Bile duct: Cholangiocarcinomas Secondary metastases to the gastric outlet by other primaries Epidemiology Incidence: less than 5% in patients with PUD. PUD is the most common benign cause of GOO. In the US, five percent PUD cases require an average of 2000 surgeries annually. Pancreatic cancer is the most common malignant cause of GOO Incidence of GOO in cases with pancreatic cancer is approximately 20%.
PHYSICAL EXAM
-Signs of chronic dehydration and malnutrition -Abdominal examination: Abdominal mass may be present Location: Epigastrium LUQ Percussion: Tympanitic mass
-LABS- Characteristic feature due to vomiting: Hypokalemic hypochloremic metabolic alkalosis Complete Blood Count (CBC): may show anemia Electrolyte panel Liver function tests: in case of malignancy Test for H pylori for diagnosis of PUD
Imaging Studies Plain abdominal radiography Contrast upper gastrointestinal (GI) studies (Gastrografin or barium) Computed tomography (CT) with oral contrast
Plain radiographs: obstruction series (ie, supine abdomen, upright abdomen, chest posteroanterior), may be used to determine: Presence of gastric dilatation
Diagnostic Procedures
Upper endoscopy can vizualize the following structures: Gastric outlet Biopsy sample may be taken for intraluminal pathology
Sodium chloride load test Procedure: Pateint is infused with 750 mL of sodium chloride solution into the stomach via a nasogastric tube (NGT) In case > 400 mL is left in the stomach after half an hour, the diagnosis of GOO may be made.
Nuclear gastric emptying study: The radionuclide is given orally and its passage is measured over a certain duration.
Barium upper GI studies:
Help in determination of site of obstruction
Help in the visualization of the gastric silhouette: can note gastric dilatation, presence of ulcers, tumors
Differentiates GOO from gastroparesis:
Goo: gastric dilatation with narrowed pylorus
Gastroparesis: general dilatation
Endoscopic biopsy Helps rule out the presence of malignancy in patients with symptoms of peptic ulcer diease CT-guided biopsy: Useful in pancreatic cancer
Needle-guided biopsy: Helps in evaluating the patient for metastasis
Historical Perspective
Classification
Pathophysiology
Gastric Outlet Obstruction (GOO) may be caused by intrinsic or extrinsic pathologies that involve the antrum and the pylorus.
- Intrinsic obstruction:
- Infiltration, scar formation or inflammation of these structures leads to intrinsic obstruction, resulting in GOO.
- Extrinsic obstruction:
- Malignancy of any of these neighboring structures may lead to extrinsic obstruction of the gastric outlet: