# Gastric Outlet Obstruction

> Gastric outlet obstruction for NEET-PG Medicine, covering benign and malignant causes, succussion splash, hypochloraemic alkalosis and initial treatment.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/gastric-outlet-obstruction
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Harrison's Principles of Internal Medicine; Sleisenger and Fordtran's Gastrointestinal and Liver Disease; Bailey and Love's Short Practice of Surgery
- How to cite: "Gastric Outlet Obstruction", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/gastric-outlet-obstruction

## Direct answer

Gastric outlet obstruction is a mechanical blockage at the pylorus or duodenum that stops gastric contents entering the small intestine. Peptic ulcer disease is the commonest benign cause, and gastric and pancreatic head cancers are the key malignant causes. Patients vomit undigested food hours after meals, and the loss of gastric acid causes hypochloraemic, hypokalaemic metabolic alkalosis. Treatment starts with nasogastric decompression and electrolyte correction, then targets the cause.

## What you must remember

- **Commonest benign cause:** peptic ulcer disease with pyloric or duodenal scarring.
- **Malignant causes:** gastric adenocarcinoma, and carcinoma of the pancreatic head or periampullary region.
- **Other causes:** caustic injury with stricture, Crohn disease and anastomotic stricture after gastric surgery.
- **Succussion splash:** a sloshing sound heard on shaking the upper abdomen, indicating fluid retained in a dilated stomach.
- **Vomiting pattern:** large volumes of undigested food, often hours after meals, rather than bile-stained vomit from gastritis.
- **Acid-base picture:** hypochloraemic, hypokalaemic metabolic alkalosis, with low urinary chloride.
- **Initial management:** nasogastric decompression with saline and potassium correction before definitive treatment.

## Approach to suspected obstruction

A 60-year-old presents with vomiting of food eaten many hours earlier, weight loss and a succussion splash, and his serum potassium is low. The management order matters, because correcting the derangement comes before the definitive procedure. The steps below set out that sequence.

1. **Confirm the obstruction:** upper GI endoscopy shows the lesion and allows biopsy of any mass or ulcer.
2. **Correct the derangement:** pass a nasogastric tube and give intravenous normal saline with potassium replacement before intervention.
3. **Identify the cause:** test for H. pylori, biopsy suspicious lesions and use CT of the abdomen to look at a pancreatic or periampullary mass.
4. **Choose definitive therapy:** endoscopic balloon dilatation for benign stricture, and stenting or surgical bypass such as gastrojejunostomy for malignant obstruction.
5. **Monitor electrolytes:** recheck potassium and chloride after treatment, since the alkalosis corrects only once chloride and fluid are replaced.

Each step depends on the one before it, so an unstable patient is resuscitated before imaging or surgery. Persistent vomiting that does not settle with decompression points to a cause that needs definitive treatment.

## Where the exam tests obstruction

Questions here test whether you treat the physiology before the lesion.

- **Trap:** giving acid suppression alone for vomiting with a succussion splash — **Correct:** obstruction needs decompression, electrolyte correction and endoscopic diagnosis first.
- **Trap:** replacing potassium without saline — **Correct:** chloride loss drives the alkalosis, so normal saline is given along with potassium.
- **Trap:** attributing weeks of vomiting of undigested food to gastroenteritis — **Correct:** persistent symptoms suggest obstruction, and endoscopy is needed to exclude malignancy.

## Frequently asked questions

### What is a succussion splash in gastric outlet obstruction?

A succussion splash is a sloshing sound heard when the upper abdomen is shaken and listened to with a stethoscope. It indicates fluid retained in a dilated stomach and is a classic bedside sign of gastric outlet obstruction.

### Why does gastric outlet obstruction cause hypochloraemic alkalosis?

Repeated vomiting of gastric contents loses hydrogen ions, chloride and potassium, producing hypochloraemic, hypokalaemic metabolic alkalosis. Low urinary chloride indicates chloride depletion, and this type of alkalosis responds to saline.

### Which investigation confirms gastric outlet obstruction and its cause?

Upper gastrointestinal endoscopy confirms gastric outlet obstruction and allows biopsy of the obstructing lesion. CT of the abdomen helps assess a pancreatic or periampullary mass that may be causing the obstruction.

### How is gastric outlet obstruction treated initially?

Initial treatment of gastric outlet obstruction is nasogastric decompression with intravenous saline and potassium correction, which relieves distension and corrects the alkalosis. Definitive treatment then depends on the cause, such as endoscopic dilatation for benign stricture or surgery for malignant obstruction.