Gastrointestinal Tract Imaging

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).

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).

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.

• 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.