Non-traumatic Abdominal Emergencies

Appendicitis & Diverticulitis - Gut Inflamed

• Appendicitis: Inflammation of appendix.
  • Clinical: RLQ pain (McBurney's), fever, ↑WBC. Alvarado score aids diagnosis.
  • Imaging:
    • USG (children/pregnant): Non-compressible, blind-ended tube >6mm diameter, target sign, periappendiceal fat stranding, ± appendicolith.
    • CT (adults): Gold standard. Similar findings to USG; superior for complications (abscess, perforation).
• Diverticulitis: Inflammation of a diverticulum (sigmoid colon most common).
  • Clinical: LLQ pain, fever, altered bowel habits.
  • Imaging (CT):
    • Segmental bowel wall thickening >4mm, pericolic fat stranding, engorged vasa recta.
    • Diverticula present. Complications: Abscess, fistula, perforation (Hinchey classification).

⭐ An appendicolith, seen in ~30% of acute appendicitis cases, significantly increases the risk of perforation and gangrene.

Cholecystitis & Pancreatitis - Biliary Blues & Pancreas Pangs

Acute Cholecystitis:

• Gallbladder (GB) inflammation, mostly calculous.
• USG: Key initial imaging.
  • Findings: GB wall thickening >3mm, pericholecystic fluid, sonographic Murphy's sign, gallstones.
• HIDA scan: Confirmatory if USG equivocal; non-visualization of GB.
• Complications: Gangrene, perforation, emphysematous cholecystitis.

Acute Pancreatitis:

• Pancreatic inflammation. Common causes: gallstones, alcohol (📌 I GET SMASHED).
• Diagnosis: 2 of 3 (pain, amylase/lipase >3x ULN, imaging findings).
• CECT: Optimal after 48-72 hrs for severity (Balthazar score, CTSI) & complications (necrosis, collections).
  • Findings: Pancreatic enlargement, peripancreatic fat stranding, fluid collections, necrosis (non-enhancing areas).

⭐ CT Severity Index (CTSI): Balthazar grade + Necrosis score (0-10). Score >6 indicates severe pancreatitis.

Bowel Obstruction & Ileus - Intestinal Impasse

Bowel Obstruction (BO): Mechanical blockage. SBO vs LBO.

• SBO Causes: 📌 "ABC": Adhesions (commonest), Bulges (hernias), Cancer.
• LBO Causes: CRC (commonest), volvulus, diverticular stricture.
• Clinical (BO): Colicky pain, vomiting, distension, obstipation. Sounds: high-pitched → absent.
• X-ray (SBO): Central loops >3 cm, step-ladder air-fluid levels, valvulae conniventes.
• X-ray (LBO): Peripheral colon >6 cm (caecum >9 cm), haustra.
• CT (BO): Gold standard. Site, cause, complications (ischemia, strangulation).

Ileus (Paralytic): Functional; ↓peristalsis, no mechanical block.

• Causes: Post-op, peritonitis, ↓K+, opioids, sepsis.
• Clinical (Ileus): Mild pain, distension, N/V, absent bowel sounds.
• X-ray (Ileus): Generalized gas, dilated SB & LB; air in rectum.

⭐ Sigmoid volvulus: X-ray shows "coffee bean" sign (inverted U-loop).

Ischemia & Perforation - Vascular & Viscus Vexations

• Mesenteric Ischemia: Life-threatening ↓ blood supply.
  • Types:
    • Arterial: Superior Mesenteric Artery (SMA) embolism (e.g., Atrial Fibrillation), SMA thrombosis (atherosclerosis).
    • Venous: Superior Mesenteric Vein (SMV) thrombosis (hypercoagulable states, portal hypertension).
    • Non-Occlusive Mesenteric Ischemia (NOMI): Systemic hypoperfusion (shock, vasopressors).
  • CT Findings: Bowel wall thickening (>3mm) or paper-thin wall, absent/↓mural enhancement, pneumatosis intestinalis (gas in bowel wall), portal/mesenteric venous gas, vascular occlusion (thrombus/embolus), mesenteric edema/fat stranding.
  • 📌 Clinical hallmark: "Pain out of proportion to physical examination findings".
• Bowel Perforation: Discontinuity of bowel wall.
  • Common Causes: Peptic ulcer disease (PUD), diverticulitis, appendicitis, ischemia, malignancy, trauma, iatrogenic.
  • CT Findings:
    • Pneumoperitoneum: Free extraluminal air; most sensitive sign.
    • Location: Anteriorly, subdiaphragmatic, outlining falciform ligament, perihepatic.
    • Other signs: Focal bowel wall defect, extraluminal oral contrast, adjacent fluid collection/abscess, phlegmon, localized fat stranding.

⭐ On CT, small amounts of pneumoperitoneum are best visualized using lung window settings (e.g., Window Width: 1500 HU, Window Level: -600 HU).

High‑Yield Points - ⚡ Biggest Takeaways

• Appendicitis: CT is gold standard (appendix >6mm, fat stranding); US in children/pregnant.
• Acute Cholecystitis: US is initial (wall >3mm, fluid, sonographic Murphy's); HIDA if equivocal.
• Acute Pancreatitis: CECT for severity and necrosis.
• Diverticulitis: CECT for wall thickening, fat stranding, complications.
• Bowel Obstruction: X-ray is initial; CT for level, cause, ischemia.
• Renal Colic: NCCT KUB is gold standard for stones.
• Mesenteric Ischemia: CTA is crucial; look for pneumatosis, portal venous gas.