This document discusses acute mesenteric ischemia and infarction. It begins by distinguishing mesenteric ischemia, which involves the small bowel, from ischemic colitis, which involves the colon. It then describes the etiologies of acute mesenteric ischemia, particularly superior mesenteric artery occlusion, embolism, thrombosis, nonocclusive mesenteric ischemia, and mesenteric venous thrombosis. The document outlines the classic presentation, laboratory findings, diagnostic imaging, differential diagnosis, and treatment approaches for acute mesenteric ischemia and infarction.

1. Acute Mesenteric
Ischemia and Infarction
Dr. Muhammad Noman Rashid
Senior Registrar
Department of Interventional Cardiology
Ziauddin Medical University 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
Celiac Trunk
IMA
SMA
Aorta

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

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

16. References
 Netter FH, Atlas of Human Anatomy
 Oldenburg et al. Arch Intern Med 164:1054 2004
 Scott JR et al. AJR 113:2 “Acute Mesenteric
Infarction” 1971
 UptoDate Online: Article on “Acute Mesenteric
Ischemia”
 UptoDate Online: Article on “Ischemic colitis”