Acute Mesenteric Ischemia and Infarction

1. Acute Mesenteric Ischemia and Infarction Dr. Sajad Ali (MBBS., MS.) Gastrointestinal & Laparoscopic surgeon Dr Ahmed Abanamy Hospital

2. A First Big Distinction… • Mesenteric Ischemia – ischemia of the small bowel, usually 2/2 an acute cause involving the SMA or SMV. • Ischemic colitis – ischemia of the colon, rarely with a known acute precipitating cause.

3. Superior Mesenteric Artery (SMA) Largest caliber vessel + 45-degree angle makes it most commonly occluded Aorta Celiac Trunk SMA IMA

4. Superior Mesenteric Artery (SMA) • Emboli occlude past the middle colic, causing small bowel ischemia Middle Colic SMA Jejunal & Ileal Arteries Occlusion Point Right Colic Ileocolic

5. Etiologies of Acute Mesenteric Ischemia (AMI) • SMA Occlusion (at least 60% of cases) • Embolism: MI, Afib, Endocarditis, Valve d/o • Thrombosis: Atherosclerosis – plaque rupture • Nonocclusive Mesenteric Ischemia (NOMI) • Atherosclerosis + shock + vasopressors • Mesenteric Venous Thrombosis (MVT) • Primary clotting disorder

6. Etiologies of Acute Mesenteric Ischemia (AMI) • Focal small bowel ischemia - rare • Partial malrotation, volvulus, mesenteric hematoma, strangulated hernia • Unknown • ?Mesenteric small vessel disease

7. History & Physical Classic Presentation: • Rapid onset of severe, unrelenting periumbilical pain • Pain out of proportion to findings on physical examination. • Nausea and vomiting • Forceful/urgent bowel evacuation • Risk factors for acute mesenteric ischemia

8. History & Physical SMA Thrombosis: • Prodrome of postprandial pain/nausea and weight loss • Presentation with classic symptoms Non-occlusive Mesenteric Ischemia: • Unexplained decline in clinical status or failure to follow expected recovery

9. History & Physical Mesenteric Venous Thrombosis: • Fever • Abdominal distension • Hemoccult positive stool

10. Laboratory Findings • Anion gap metabolic acidosis • Elevated arterial/venous lactate • Leukocytosis • Hemoconcentration • Elevated LDH, amylase, AST, and CPK • Elevated K and Phos are late signs

11. Radiology • Plain films – thumbprinting, thickened bowel (<40% sensitivity) • CT – thickened/dilated bowel, intramural hematoma, pneumatosis (64% sensitivity) • MRI – promising but untested to date • Mesenteric angiography – test of choice; can identify the type of AMI

12. Differential Diagnosis Other serious conditions to consider: • Pancreatitis • Acute Diverticulitis • Acute Cholecystitis • Small bowel obstruction • Perforation of a viscous • Ruptured aneurysm

13. Treatment • Resuscitation with fluids/blood products • Anticoagulation • Infusion of a vasodilator • Glucagon systemically OR • Papaverine through a catheter

14. From Ischemia to Infarction • Marked by peritoneal signs, fever • Emergent laporatomy • Restoration of interrupted blood flow with arteriotomy or bypass graft • Resection of infarcted bowel • Second-look in 24-48 hours • Vasodilators and careful pressor use

15. A Word on Ischemic Colitis • Presentation: less & more focal pain (usually left-sided), more bloody diarrhea, >90% are over 60 years old. • Etiology rarely identified: ?small vessel disease +/- hypoperfusion • Episodes usually self limited except when stricture or gangrene develops • Colonoscopy is initial evaluation of choice