Gastric outlet obstruction

Gastric outlet obstruction Microchapters
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Overview
Classification
Pathophysiology
Causes
Differentiating Gastric outlet obstruction from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Diagnosis
Treatment Medical Therapy Surgery

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Sudarshana Datta, MD [2]

Synonyms and keywords: GOO

Overview

Gastric outlet obstruction occurs due to pathologies that cause intrinsic or extrinsic obstruction of the pylorus and antrum. Infiltration, scar formation or inflammation of the gastric outlet leads to intrinsic obstruction, while malignancy of neighboring structures such as the pancreas, gallbladder, liver and duodenum may lead to extrinsic obstruction of the gastric outlet. Common causes of GOO include PUD, gastric polyps, caustic ingestion, duodenal stricture, systemic amyloidosis of the gastrointestinal tract, eosinophillic gastroenteritis and obstruction by gallstones. Five percent of all cases of peptic ulcer disease (which is the most common benign cause of GOO) worldwide, develop gastric outlet obstruction. GOO presents as nausea, vomiting, dehydration, electrolyte abnormalities, weight loss, malnutrition, fullness of epigastrium, early satiety and bloating. Laboratory studies of patients may show hypokalemic hypochloremic metabolic alkalosis which is a characteristic feature due to vomiting. In case of of GOO due to suspected PUD, tests for H pylori should also be performed in patients. Barium upper GI studies help in the determination of site of obstruction, visualization of the gastric silhouette, presence of gastric dilation, pylorus narrowing, presence of ulcers, tumors and differentiation from gastroparesis. Upper endoscopy performed in patients may help with visualization of the gastric outlet, biopsy sampling in case of intraluminal pathology and thereby helps rule out the presence of malignancy in patients with symptoms of peptic ulcer disease. Surgery is the primary modality of treatment for patients with GOO. It is required for more than 75 percent of patients, with scarring, fibrosis and tumors. The aims of surgery in case of GOO include relief of obstruction, relief in patients with failure to respond to medical therapy or failure to improve even after 72 hours of therapy and correction of PUD symptoms. Various types of surgical procedures performed in cases of GOO are vagotomy and antrectomy, gastrojejunostomy (vagotomy and antrectomy with Billroth II reconstruction), balloon dilatation, pylorotomy, pyloroplasty and laparoscopic techniques. Care must be taken to look out for various complications arising after surgery such as perforation, anastomotic leak, dilation and dysmotility of stomach, edema of the gastric wall and postgastrectomy syndromes.

Classification

Gastric outlet obstruction (GOO) may be due to any underlying condition that results in mechanical obstruction to emptying of gastric contents. GOO is classified based on the underlying cause into benign GOO and malignant GOO. Statistically, benign GOO comprises 37 percent of cases and includes peptic ulcer disease whereas malignant GOO comprises of the remaining 53 percent of cases.

Pathophysiology

It is understood that GOO is the result of multiple intrinsic (lumen & wall) or extrinsic (involving neighbouring structures) pathologies that involve the antrum and the pylorus.

• Intrinsic obstruction: Conditions involving infiltration, scar formation or inflammation of antrum and the pylorus may lead to intrinsic obstruction and GOO.
• Extrinsic obstruction: Any malignancy of neighboring structures such as duodenum, liver, gallbladder and pancreas may lead to extrinsic obstruction of gastric outlet.

Causes

Causes of GOO may be classified as benign and malignant.

Benign causes

Benign causes of GOO can either be congenital or acquired. The acquired causes of GOO may further be categorized into acute or chronic. The acquired acute causes of GOO results from edema and inflammation of antrum and the pylorus. The acquired chronic causes of GOO results from intrinsic obstruction due to fibrosis and scar formation. In general, benign causes of GOO include:

• GI causes such as PUD: 5% cases (most commonly affecting pylorus and initial part of the duodenum), gastric polyps, duodenal stricture ,gastro-duodenal tuberculosis, caustic ingestion, obstruction by gallstones (Bouveret syndrome), and pancreatic pseudocyst formation.

Congenital causes of gastric outlet obstruction include:

• Pyloric stenosis:It is due to hypertrophy of pyloric smooth muscles (circular). Pyloric stenosis is the most common cause of GOO in children with boys more commonly affected than girls.
• Annular pancreas

Malignant causes

• Malignancies involving neighboring structures may lead to GOO:
  • Pancreas: Pancreatic cancer
    • Most common malignancy leading to extrinsic obstruction of the pylorus
    • Occurence in one fifth of patients
  • Stomach: Gastric cancer, Zollinger-Ellison Syndrome
  • Duodenum: Duodenal cancer, ampullary cancer
  • Bile duct: Cholangiocarcinoma
  • Secondary metastasis to the gastric outlet by other primaries

Differentiating Gastric outlet obstruction from Other Diseases

Gastric outlet obstruction must be differentiated from other conditions that cause abdominal pain, heartburn, bloating, nausea and vomiting such as:

Differential Diagnosis
Disease	Symptoms									Diagnosis	Other findings
	Pain			Nausea & Vomiting	Heartburn	Belching or Bloating	Weight loss	Loss of Appetite	Stools	Endoscopy findings
	Location	Aggravating Factors	Alleviating Factors
Gastric outlet obstruction (GOO)	Epigastric pain	Food	-	✔	✔	✔	✔	✔	Black stools in case of Peptic Ulcer Disease(PUD)	Determines the site of obstruction Helps in the visualization of the gastric silhouette Differentiation of GOO from gastroparesis where gastric dilation is not associated with the narrowing of the pylorus	Sodium chloride load test Presence of >400 mL NaCl solution in stomach after half an hour, is diagnostic of GOO. Needle-guided biopsy Helps in the evaluation of patients for metastasis
Acute gastritis	Epigastric pain	Food	Antacids	✔	✔	✔	-	✔	Black stools	Pangastritis or antral gastritis Erosive (Superficial, deep, hemorrhagic) Nonerosive (H. pylori)	-
Chronic gastritis	Epigastric pain	Food	Antacids	✔	✔	✔	✔	✔	-	H. pylori gastritis Atrophy Intestinal metaplasia Lymphocytic gastritis Enlarged folds Aphthoid erosions	-
Atrophic gastritis	Epigastric pain	-	-	✔	-		✔	✔	-	H. pylori Mucosal atrophy Autoimmune Mucosal atrophy	Diagnosed by: Antiparietal and anti-IF antibodies Achlorhydria and hypergastrinemia Low serum cobalamine
Crohn's disease	Abdominal pain	-	-	-	-	-	✔	✔	Chronic diarrhea often bloody with pus or mucus Rectal bleeding	Thickened antral folds Antral narrowing Hypoperistalsis Duodenal strictures	Fever Fatigue Anemia (pernicious anemia)
GERD	Epigastric pain	Spicy food Tight fitting clothing	Antacids Head elevation during sleep	✔ (Suspect delayed gastric emptying)	✔	-	-	-	-	Esophagitis Barrette's esophagus Strictures	Other symptoms: Dysphagia Regurgitation Nocturnal cough Hoarseness
Peptic ulcer disease	Epigastric pain sometimes extending to back Right upper quadrant pain	Duodenal ulcer Pain aggravates with empty stomach Gastric ulcer Pain aggravates with food	Antacids Duodenal ulcer Pain alleviates with food	✔	✔	-	-	-	Black stools	Gastric ulcers Most ulcers are at the junction of fundus and antrum 0.5-2.5cm Duodenal ulcers Found in the first part of duodenum <1cm	Other diagnostic tests Serum gastrin levels Secretin stimulation test Biopsy
Gastrinoma	Abdominal pain	-	-	✔ (suspect gastric outlet obstruction)	✔	-	-	-	Black stools	Useful in collecting the tissue for biopsy	Diagnostic tests Serum gastrin levels Somatostatin receptor scintigraphy CT and MRI
Gastric Adenocarcinoma	Abdominal pain	-	-	✔	✔	✔	✔	✔	Black stools, or blood in stools	Esophagogastroduodenoscopy Multiple biopsies are taken to establish the diagnosis and determine histological variant.	Other symptoms Dysphagia Early satiety Frequent burping
Primary gastric lymphoma	Abdominal pain Chest pain	-	-	-	-	-	✔	-	-	Useful in collecting the tissue for biopsy	Other symptoms Painless swollen lymph nodes in neck and armpit Night sweats

Epidemiology and Demographics

The epidemiology of GOO is as follows:

• The incidence of peptic ulcer disease (which is the most common benign cause of GOO) is approximately 10-19 per 100,000 individuals worldwide.
• Five percent of all cases of peptic ulcer disease worldwide, develop gastric outlet obstruction.
• The incidence of gastric outlet obstruction is less than 5 per 100,000 patients worldwide.
• In the United States, peptic ulcer disease requires an average of 2000 surgeries annually.
• Pancreatic cancer is the most common malignant cause of GOO.
• The incidence of GOO in cases with pancreatic cancer is approximately 20% of all cases.

Diagnosis

History

The following history is relevant in patients with GOO:

• History of peptic ulcer disease or its complications
• History of abdominal pain and weight loss in cases of pancreatic cancer

Symptoms

The clinical presentation of GOO is categorized into early and late stage symptoms. The early stage symptoms include nausea and vomiting (characteristic feature). Vomiting is intermittent, non bilious, occurs after one hour after consuming meal and contains undigested particles of food leading to dehydration.

The late stage symptoms include abdominal fullness, malnutrition, weight loss, bloating, and early satiety.

Physical Examination

In the late stages of GOO, patients may develop signs of malnutrition and incomplete obstruction. Signs of malnutrition include weight loss and signs of dehydration. Signs of incomplete obstruction include findings such as abdominal mass, visible gastric peristalsis, fullness of epigastrium and a tympanitic mass on percussion. {{#ev:youtube|UVJYQlUm2A8}}

Laboratory Findings

Laboratory investigations suggestive of GOO include Hypokalemic hypochloremic metabolic alkalosis (due to vomiting). In order to assess the severity and etiology of GOO, other investigations such as CBC, electrolyte panel, tests for H Pylori and liver function tests may be done.

Imaging Findings

Imaging studies such as plain radiographs, contrast upper gastrointestinal (GI) studies and Computed Tomography (CT) with oral contrast may be used for evaluating patients with symptoms of GOO.

X ray

An x-ray (obstruction series or barium study) may be helpful in the diagnosis of GOO. Findings on an x-ray suggestive of GOO include gastric dilatation. Findings on barium or Gastrografin study help in the determination of site of obstruction, visualization of the gastric silhouette, Gastric dilation, narrowed pylorus, presence of ulcers and tumors. GOO may also be differentiated from gastroparesis in which gastric dilation is not associated with the narrowing of the pylorus.

• Nuclear gastric emptying study:
  • Radionuclide is given orally and its passage is measured over a certain duration.

Computed tomography (CT) with oral contrast

CT with oral contrast or CT-guided biopsy may be done in suspected cases with equivocal findings on X Ray and Barium Upper GI studies. Findings of CT are variable and include those of the underlying condition.

Other Diagnostic Studies

Endoscopy

Upper endoscopy may be helpful in the diagnosis of GOO. An upper endoscopy aids in visualization of the gastric outlet, biopsy sampling in case of intraluminal pathology. In addition, Endoscopic biopsy helps rule out the presence of malignancy in patients with symptoms of Peptic Ulcer Disease (PUD) :

Sodium chloride load test

In sodium chloride test, the patient is infused with 750 mL of sodium chloride solution into the stomach via a nasogastric tube (NGT). After half an hour if > 400 mL is left in the stomach, the diagnosis of GOO is made.

Needle-guided biopsy

Needle guided biopsy is used to evaluate patients for metastasis, in order to detect the primary tumor on histology.

Treatment

Medical Therapy

• Medical therapy may be given to all patients prior to surgery in cases of gastric outlet obstruction. Medical therapy primarily involves supportive care in preparation of surgery with hydration, NG tube decompression, correction ofelectrolyte imbalances.
• Endoscopic stent placement for advanced GI cancer causing GOO.

• In patients with benign Gastric Outlet Obstruction due to peptic ulcer disease, medical therapy with proton pump inhibitors or histamine-2 (H2) blockers is given in patients to treat acute inflammation and edema.

• For the treatment of strictures in patients with GOO due to advanced stage cancer, endoscopic pneumatic balloon dilatation and use of self-expandable metallic stents are preferred techniques.

Surgery

Surgery is the primary modality of treatment for patients with GOO. It is required for more than 75 percent of patients, with scarring, fibrosis and tumors. The aims of surgery in case of GOO include relief of obstruction, patients with failure to respond to medical therapy or failure to improve even after 72 hours of therapy, and correction of PUD symptoms.

Guidelines for surgery

Surgery should be considered only in patients who are able to tolerate the surgical procedure. Major resections of the tumor must be done in the absence of metastatic disease. In the case of metastatic disease, extent of surgery needs to be determined.

Types of surgical procedures

The types of surgical procedures performed in cases of GOO are as follows:

• Vagotomy and antrectomy, gastrojejunostomy (vagotomy and antrectomy with Billroth II reconstruction), balloon dilatation, pylorotomy, pyloroplasty, robotic-assisted pyloroplasty, vagotomy and pyloroplasty, truncal vagotomy and gastrojejunostomy and laparoscopic surgery (laparoscopic truncal vagotomy, laparoscopic gastrojejunostomy, laparoscopic pyloromyotomy, laparoscopic gastrojejunostomy).The advantages of laparoscopy include fast GI transit recovery time, fewer blood transfusions, low mortality and brief hospital stay.
• Endoscopic surgery (Endoscopic gastroenteric anastomosis) is preferred in cases of malignant obstruction. The advantages include high success rate, brief hospital stay and low mortality.

Contraindications to surgery

Contraindications to surgery include severe malnutrition and advanced unresectable cancer.

Complications of surgery

Complications arising after surgery include perforation due to stenting, stent reocclusion, stent migration, stomach dilation, gastric wall edema, anastomotic leak and postgastrectomy syndromes.