Gastrointestinal Tract Imaging

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GIT Imaging Toolkit - Modalities & Marvels

  • X-ray (Plain): Initial; detects obstruction (air-fluid levels), perforation (free air), calcifications.
  • Barium Studies:
    • Single contrast: Lumen, gross morphology.
    • Double contrast (air + barium): Mucosal detail (ulcers, polyps).

    ⭐ Double contrast barium studies are superior for mucosal detail visualization.

  • Ultrasound (USG): Bowel wall, appendicitis, intussusception, fluid. No radiation.
  • CT Scan: Primary modality. Oral/IV contrast. Inflammation, tumors, obstruction, perforation. CT Enterography (small bowel).
  • MRI: Superior soft tissue. Rectal cancer staging, fistulae, IBD. MR Enterography (small bowel, no radiation). Abdominal X-ray showing fecal loading

Upper GIT Scans - Gullet to Gut Woes

  • Barium Swallow (Esophagus):
    • Assesses dysphagia, odynophagia, GERD, motility disorders (e.g., achalasia).
    • Identifies: Strictures, webs, diverticula (Zenker's: posterior pharyngoesophageal outpouching), masses, hiatus hernia.

    ⭐ Bird's beak sign on barium swallow is characteristic of achalasia cardia.

    • Esophageal cancer: Presents as apple-core lesion or irregular, ulcerated filling defect.
  • Barium Meal (Stomach & Duodenum):
    • For epigastric pain, dyspepsia, PUD, gastric outlet obstruction (GOO), suspected masses.
    • Detects: Ulcers (contrast-filled craters), gastric carcinoma (linitis plastica "leather bottle", polypoid mass), pyloric stenosis (string sign).
  • Barium Meal Follow Through (BMFT - Small Bowel):
    • Evaluates malabsorption, chronic diarrhea, Crohn’s disease, SBO.
    • Crohn’s: Kantor's string sign, skip lesions, cobblestoning, fistulae, rose thorn ulcers.
  • CT Enterography/Enteroclysis:
    • Superior for small bowel wall/extraluminal detail: Crohn's, tumors, obscure GI bleed. Enteroclysis (NJ tube for contrast). Barium swallow showing bird beak sign in achalasia

Lower GIT Insights - Bowel Disorder Decode

  • Inflammatory Bowel Disease (IBD):
    • Crohn's Disease: Terminal ileum common, skip lesions, transmural inflammation, cobblestoning, string sign (Kantor's), fistulas. CT/MRI enterography for assessment.
    • Ulcerative Colitis (UC): Rectum invariably involved, continuous proximal spread, superficial (mucosal/submucosal) inflammation, loss of haustra, toxic megacolon risk.

      ⭐ Lead pipe appearance of the colon on barium enema is classic for chronic Ulcerative Colitis. Lead pipe colon on barium enema

  • Bowel Obstruction:
    • Small Bowel Obstruction (SBO): Dilated small bowel loops >2.5 cm, central distribution, multiple air-fluid levels, valvulae conniventes visible. Common causes: adhesions, hernias.
    • Large Bowel Obstruction (LBO): Dilated large bowel >6 cm (cecum >9 cm), peripheral distribution, haustra visible. Common causes: malignancy, volvulus.
  • Other Key Conditions & Signs:
    • Appendicitis: CT is gold standard: appendiceal diameter >6 mm, wall thickening/enhancement, periappendiceal fat stranding, appendicolith. Graded compression US also used.
    • Diverticulitis: CT findings include segmental bowel wall thickening, pericolic fat stranding; crucial for detecting complications (abscess, perforation, fistula).
    • Colorectal Cancer (CRC): "Apple core" lesion on barium studies or CT. CT colonography for screening; MRI for local staging of rectal cancer.

Acute GIT Alerts - Red Flag Radiology

  • Pneumoperitoneum: Sign of perforation. Free subdiaphragmatic air (X-ray), Rigler's, falciform ligament sign.

    ⭐ Rigler's sign (air on both sides of the bowel wall) on an abdominal X-ray indicates pneumoperitoneum.

  • Bowel Obstruction: Dilated loops (SB >3 cm, LB >6 cm, cecum >9 cm), multiple air-fluid levels.
  • Bowel Ischemia: Pneumatosis intestinalis (air in wall), portal venous gas, bowel wall thickening, thumbprinting.
  • Perforation: GIT breach. Extraluminal air or leaked contrast.
  • Volvulus: Bowel twisting. Coffee bean sign (sigmoid AXR), whirl sign (CT).
  • Intussusception: Telescoping bowel. Target/doughnut sign (US/CT), common in children.

High‑Yield Points - ⚡ Biggest Takeaways

  • Barium swallow for dysphagia; double contrast for mucosal detail.
  • CT abdomen: staging GI malignancies, detecting perforation, obstruction, ischemia.
  • MRCP: gold standard for non-invasive biliary and pancreatic duct imaging.
  • Apple core lesion (barium): classic for colorectal carcinoma.
  • Key barium signs: Bird's beak (achalasia), String sign (Crohn's), Rat-tail (esophageal Ca).
  • Pneumoperitoneum (X-ray/CT): indicates bowel perforation (e.g., Rigler's sign).
  • Small bowel obstruction: dilated loops (>2.5 cm), air-fluid levels on X-ray/CT.

Practice Questions: Gastrointestinal Tract Imaging

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Mark the correct statement regarding inflammatory bowel disease.

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Flashcards: Gastrointestinal Tract Imaging

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What is the imaging of choice for diagnosing appendicitis in adults?_____

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What is the imaging of choice for diagnosing appendicitis in adults?_____

CT scan

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