Gastric Ultrasound: Clinical Indications and Pathological Findings

Part 1: Clinical Indications for Gastric Ultrasound

A. Pre-anesthetic / Aspiration Risk Assessment (POCUS)

• Unreliable historian (cognitive impairment, dementia, delirium)
• Language barriers (patient cannot accurately report last meal)
• Pediatric patients (parents may be unsure or fasting instructions unclear)
• Non-compliant patients / altered mental status

• Diabetes mellitus (diabetic gastroparesis - autonomic neuropathy slows emptying)
• Acute or chronic opioid use (opioids significantly delay gastric motility)
• Pregnancy (progesterone relaxes the lower esophageal sphincter; mechanical compression by the uterus)
• Morbid obesity (increased intra-abdominal pressure and altered anatomy)
• End-stage renal disease and end-stage liver disease
• Neuromuscular disease
• Gastroesophageal reflux disease (GERD)
• Abdominal infection / peritonitis / ileus (pain and infection impair gastric motility)

• Any emergency situation where fasting cannot be confirmed and NPO guidelines cannot be followed
• Trauma patients, acute abdomen, bowel obstruction

• Whether to perform standard induction vs. Rapid Sequence Intubation (RSI)
• Whether to use an endotracheal tube vs. a supraglottic airway device (laryngeal mask)
• Whether to insert a nasogastric tube pre- or peri-operatively for decompression
• Whether to postpone or cancel an elective procedure

• Critically ill patients with enteral tube feeding (evaluating residual gastric volume)
• Patients on mechanical ventilation requiring procedures

B. Diagnostic / Structural Indications

• Epigastric pain or discomfort - evaluation of gastric wall
• Palpable epigastric mass - characterize a gastric mass
• Persistent/unexplained vomiting - rule out pyloric obstruction or hypertrophic pyloric stenosis (classically in neonates)
• Suspected gastric outlet obstruction
• Follow-up of known gastric tumors or post-surgical stomach
• Suspected peptic ulcer disease - especially in pediatric patients (water-filled sonography)
• Evaluation of perigastric lymph nodes (staging of malignancy)
• Hypertrophic pyloric stenosis in infants - ultrasound is the gold standard (pyloric muscle thickness > 3 mm, pyloric channel length > 15 mm)

Part 2: Pathological Changes Detectable on Gastric Ultrasound

1. Gastric Content Assessment Findings (POCUS)

2. Gastric Carcinoma

• Early gastric carcinoma: mild, flat or polypoid wall thickening with hypoechoic change; layers 1-3 disturbed but layer 4 (muscularis propria) intact
• Advanced gastric carcinoma: severe, extensive wall thickening, hypoechoic change, complete disruption of all 5 layers of the gastric wall ("pseudo-layering" pattern); mucosal irregularity and discontinuity; perigastric lymphadenopathy
• Invasion depth can be assessed by layer disruption - T staging correlates with the deepest disrupted layer
• Pictorial Essay: Sonography of the Stomach provides detailed layer-by-layer correlation

3. Benign Gastric Ulcer

• Increased wall thickness around the ulcer site
• Asymmetric thickening of mucosa and muscularis
• Gastric spasm and wall deformity
• The ulcer crater itself appears as an outpouching dense echo or arc with posterior acoustic artifact or shadowing
• With water-filling technique: ulcer visible as a mucosal defect
• Surrounding edematous mucosal thickening
• Loss of normal multilaminar gut signature at ulcer site (particularly visible in H. pylori gastritis)

4. Gastritis

• Mucosal thickness > 4 mm in the gastric antrum is suggestive of gastritis
• Marked transmural gastric wall thickening (especially in H. pylori-associated gastritis)
• Loss of the normal 5-layer gut signature (particularly in inflammatory or erosive forms)
• Mucosal irregularity at the posterior antral wall
• Perigastric lymph nodes may be enlarged
• Findings typically resolve after appropriate antibiotic therapy (documented on follow-up US)

5. Gastric Lymphoma

• Segmental or circumferential hypoechoic wall thickening - often marked (5 mm to > 25 mm)
• Preservation of the mucosal interface (echogenic layer 1) within the thickened wall - this is a characteristic distinguishing feature from carcinoma
• "Giant fold" appearance: marked circumferential thickening with preserved mucosal echogenicity
• Complete loss of normal wall layering in transmural involvement
• Reduced wall echogenicity and reduced motility
• Regional lymphadenopathy is common
• Ulcerated lymphoma: irregular mucosal surface or large mucosal defect

6. Gastric Leiomyoma / GIST (Gastrointestinal Stromal Tumor)

• Well-defined, hypoechoic submucosal mass
• Leiomyosarcoma / malignant GIST: bulky mass, irregular margins, areas of necrosis (heterogeneous echogenicity), invasion of adjacent structures (spleen, pancreas)
• Differentiation between benign and malignant stromal tumors based on: size, margin regularity, necrosis, growth pattern

7. Gastric Adenoma

• Round to oval, echogenic mass (unlike the hypoechoic tumors above)
• Important to identify as it is a dysplastic/premalignant lesion

8. Hypertrophic Pyloric Stenosis (Infants)

• Gold standard imaging - highly sensitive and specific
• Thickened pyloric muscle > 3 mm
• Elongated pyloric channel > 15-17 mm
• Failure of the pylorus to open ("closed ring" appearance)
• Real-time US shows no passage of gastric contents through the pylorus

9. Gastric Outlet Obstruction

• Dilated, fluid-filled stomach
• Antral wall thickening (benign vs. malignant cause)
• Sometimes a small ulcer crater visible at the pyloric canal in chronic peptic obstruction

10. Perigastric / Extramucosal Findings

• Perigastric lymphadenopathy - important for staging malignancy
• Ascites adjacent to the stomach wall
• Invasion of adjacent organs (pancreas, liver, spleen) in advanced malignancy

Summary Table

Gastric Ultrasound

Clinical Indications

• Uncertain fasting status (altered mental status, language barrier, pediatrics)
• Delayed gastric emptying: diabetes, opioid use, pregnancy, morbid obesity, GERD
• Emergency/urgent surgery where NPO cannot be confirmed

• Epigastric pain, palpable mass, persistent vomiting
• Suspected pyloric stenosis (infants) - US is gold standard
• Suspected gastric outlet obstruction
• Staging/follow-up of gastric tumors

Pathological Findings on Ultrasound

• Grade 0 = empty (no content) - low aspiration risk
• Grade 2 = clear fluid in both positions, CSA > 10 cm² - high volume
• Solid/hyperechoic content in any position = full stomach, high risk