GASTRIC OUTLET OBSTRUCTION (GOO) Note Complete

GASTRIC OUTLET OBSTRUCTION (GOO)

Definition

Partial or complete obstruction of the distal stomach, pylorus, or proximal duodenum, preventing normal gastric emptying into the duodenum.

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Etiology

A. Congenital causes

• Infantile hypertrophic pyloric stenosis (most common in infants)

• Duodenal atresia

• Annular pancreas

• Preduodenal portal vein

• Gastric/duodenal webs or membranes

B. Acquired causes

1. Benign causes

• Peptic ulcer disease (most common in adults)

• Chronic pancreatitis (fibrosis, pseudocyst compression)

• Postoperative adhesions or anastomotic strictures

• Ingestion of corrosives

• Gallstone impaction (Bouveret syndrome)

• Crohn’s disease

• Tuberculosis (gastroduodenal)

2. Malignant causes

• Carcinoma of the stomach (antral carcinoma)

• Carcinoma of the pancreas (head region)

• Duodenal carcinoma

• Lymphoma involving pylorus

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Pathophysiology

• Obstruction → gastric stasis → accumulation of food, fluid, and secretions → gastric dilatation

• Persistent vomiting → loss of H⁺, Cl⁻, K⁺ → hypochloremic, hypokalemic metabolic alkalosis

• Dehydration → hypovolemia → renal compensation (paradoxical aciduria)

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Clinical Features

Symptoms

• Vomiting – projectile, non-bilious, of undigested food; may be late after meals

• Fullness / bloating / early satiety

• Epigastric pain (relieved by vomiting)

• Weight loss and dehydration

• Constipation and reduced urine output

Signs

• Visible gastric peristalsis (from left to right across epigastrium)

• Succussion splash (sloshing sound >6 hrs after meal)

• Epigastric distension

• Signs of dehydration: sunken eyes, dry tongue, hypotension

• Palpable lump (in carcinoma or hypertrophic pyloric stenosis)

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Investigations

Laboratory

• Electrolyte imbalance: ↓Na⁺, ↓K⁺, ↓Cl⁻, ↑HCO₃⁻ (metabolic alkalosis)

• Hemoconcentration (↑Hct)

• Renal function tests – elevated urea/creatinine due to dehydration

Imaging

• Plain X-ray abdomen:

• Greatly distended stomach with fluid level, no gas beyond pylorus

• Barium meal:

• Delayed gastric emptying, “string sign” (narrow pylorus), or “beak-like narrowing”

• Endoscopy:

• Visualize site of obstruction; exclude malignancy; can take biopsy

• CT scan:

  • Defines cause and extrinsic compression (pancreatic malignancy, pseudocyst)

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Management

1. Initial (Stabilization)

• Nil per oral (NPO)

• Nasogastric decompression

• IV fluids – correct dehydration and electrolyte imbalance

• Correct metabolic alkalosis

• Proton pump inhibitors / H₂ blockers

• Nutritional support

2. Definitive treatment

a. Benign causes:

• Peptic ulcer-related:

  • Endoscopic balloon dilatation (first-line if fibrosis mild)

  • Surgery if refractory:

    • Truncal vagotomy + antrectomy (Billroth I/II)

    • Gastrojejunostomy

• Hypertrophic pyloric stenosis:

  • Ramstedt’s pyloromyotomy

• Chronic pancreatitis / pseudocyst:

  • Treat underlying cause or cyst drainage

b. Malignant causes:

• Resectable:

  • Subtotal/total gastrectomy or pancreaticoduodenectomy (depending on origin)

• Unresectable:

  • Palliative gastrojejunostomy or endoscopic stenting

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Complications

• Severe dehydration and shock

• Metabolic alkalosis with paradoxical aciduria

• Aspiration pneumonia

• Nutritional deficiencies

• Gastric perforation (rare, late stage)

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Summary Table

Feature	Benign	Malignant
Onset	Gradual	Rapid
Vomiting	Large, non-bilious, food particles	Small, may contain altered blood
Pain	Relieved by vomiting	Persistent
Visible peristalsis	Prominent	Often absent
Weight loss	Moderate	Marked
Endoscopy finding	Scarring, ulcer	Mass, irregular ulcer