Intestinal Ischemia Michele Young, MD Chief GI Phoenix VA Hospital Banner/VA GI Fellowship Program Director

Outline Types Anatomy Pathophysiology Acute Mesenteric Ischemia Mesenteric Vein Thrombosis Focal Segmental Ischemia Colon Ischemia Chronic Mesenteric Ischemia Vasculitides

Types TYPE FREQUENCY (%) Colon ischemia 75 Acute mesenteric ischemia 25 Focal segmental ischemia <5 Chronic mesenteric ischemia

Anatomy – Celiac Axis Supplies stomach, duodenum, pancreas, and liver Three branches: left gastric, common hepatic, splenic Common hepatic: gastroduodenal, right gastroepiploic, anterior superior pancreaticoduodenal Splenic: pancreatic and left gastroepiploic

Anatomy – Celiac Axis AIPD, anterior inferior pancreaticoduodenal artery; ASPD, anterior superior pancreaticoduodenal artery; CP, caudal pancreatic artery; DP, dorsal pancreatic artery; GD, gastroduodenal artery; H, common hepatic artery; LG, left gastric artery; PIPD, posterior inferior pancreaticoduodenal artery; PM, pancreata magna; RGE, right gastroepiploic artery; S, splenic artery; TP, transverse pancreatic artery.

Anatomy – Superior Mesenteric Artery (SMA) Anterior and posterior inferior pancreaticoduodenal Middle colic Right colic Ileocolic

Anatomy - SMA AIPD, anterior inferior pancreaticoduodenal artery; COL, colic branches; IL, ileal branches; IC, ileocolic artery; JEJ, jejunal branches; MC, middle colic artery; PIPD, posterior inferior pancreaticoduodenal artery; RC, right colic artery.

Anatomy – Inferior Mesenteric Artery (IMA) Left colic Sigmoid branches Superior rectal Supply distal transverse to proximal rectum Distal rectum: internal iliac

Anatomy - IMA AOR, arc of Riolan; ASC, ascending branch of the left colic artery; CA, central artery; DSC, descending branch of the left colic artery; LMC, left branch of middle colic artery; MA, marginal artery; MC, middle colic artery; RMC, right branch of middle colic artery; S, sigmoid branches; SR, superior rectal artery

Pathophysiology Bowel can tolerate 75% reduction of blood flow and oxygen consumption for 12 hours Collaterals open immediately After hours, vasoconstriction reduces collateral flow (NOMI) Hypoxia, reperfusion injury ROS by xanthine oxidase Microvascular injury by PMNs

Acute Mesenteric Ischemia CAUSE FREQUENCY (%) SMA embolus 50 Nonocclusive mesenteric ischemia 25 SMA thrombosis 10 Mesenteric venous thrombosis Focal segmental ischemia 5

Clinical Features Acute abdominal pain in patient with CV risks Rapid and forceful bowel evacuation (SMAE) Pain out of proportion to exam Some more indolent (MVT) Unexplained abdominal distention (sign of infarction) or GI bleeding (NOMI) Physical findings worsen with progressive loss of bowel viability Infarction: 70-90% mortality

Diagnosis Labs Plain films CT CT angiography 75% have WBC > 15 50% have metabolic acidosis Plain films Poorly sensitive (30%) and nonspecific Formless loops of small intestine Ileus, thumbprinting, pneumatosis Portal or mesenteric vascular gas CT Colon dilatation Bowel wall thickening Lack of enhancement of arterial vasculature Ascites CT angiography Better evaluation of vessels Selective mesenteric angiography Gold standard Prompt laparotomy if angiography not available

Portal Gas

Treatment General Superior Mesenteric Artery Embolus Resuscitation, Broad-spectrum antibiotics Superior Mesenteric Artery Embolus Cardiac origin Major: proximal to ileocolic Intra-arterial papaverine Surgical revascularization Minor and no peritoneal signs Intra-arterial papaverine (or thrombolytics) Anticoagulation

SMA Embolus Pre and post treatment

Treatment Nonocclusive Mesenteric Ischemia Vasoconstriction from preceding cardiovascular event Angiography Narrowing of SMA branch origins Irregularities in intestinal branches Spasm of arcades Impaired filling of intramural vessels SMA infusion of papaverine for 24 hours Surgery if peritoneal signs are present

NOMI Pre and post treatment

Treatment Acute Superior Mesenteric Artery Thrombosis Severe atherosclerotic narrowing Often superimposed on chronic mesenteric ischemia Demonstrated on aortography Management same as SMA embolism

Mesenteric Vein Thrombosis Age: mid-60s to 70s 20% mortality Manifest as colon ischemia, acute mesenteric ischemia, or focal segmental ischemia Causes Arterial hypertension Neoplasms Coagulation disorders Estrogen

Mesenteric Vein Thrombosis Acute Pain out of proportion to exam, n/v Lower GI bleeding suggests infarction Diagnosis CT is study of choice (finds >90%) Mesenteric arteriography Slow or absent filling of mesenteric veins Failure of arterial arcades to empty Prolonged blush in involved segment Treatment Incidental: up to six months of anticoagulation (AC) Peritonitis: surgery, papaverine, post-op heparin No peritoneal signs: heparin followed by 3-6 mos AC

Mesenteric Vein Thrombosis Subacute Abdominal pain for weeks to months but no infarction Chronic Asymptomatic May develop GI bleeding from varices Treatment: control bleeding

Focal Segmental Ischemia Involves small bowel Causes Atheromatous emboli Strangulated hernias Immune complex disorders Trauma Segmental venous thrombosis Radiation therapy Oral contraceptives Usually adequate collaterals to prevent infarction Presentation: enteritis, stricture, acute abdomen Chronic can resemble Crohn's

Focal Segmental Ischemia Radiologic studies Smooth tapered stricture Abrupt change to normal distally Dilated proximally Treatment: resection

Colon Ischemia TYPE FREQUENCY (%)* Reversible colopathy and transient colitis >50 Transient colitis 10 Chronic ulcerating colitis 20 Stricture Gangrene 15 Fulminant universal colitis <5

Colon Ischemia Most common form of intestinal ischemia 7.2 cases per 100,000 person-years Female predilection Most > 60 years old Young pt: vasculitis, coagulation disorders, cocaine, medications Right colon ischemia May have small intestinal ischemia

Medications Penicillins Alkaloid and taxanes Constipation-Inducing Agents Pseudoephedrine Diuretics Oral contraceptive pills Amphetamines (R sided) Cocaine (L sided) Kayexelate Magnesium citrate Sodium phosphate Bisacodyl Glycerin enemas NSAIDs Sumatriptan Alosetron

Pathology Mild: mucosal and submucosal hemorrhage and edema More severe: ulcerations, crypt abscesses, pseudopolyps, pseudomembranes, iron-laden macrophages, submucosal fibrosis (stricture) Most severe: transmural infarction

Clinical Features Sudden cramping Mild left lower quadrant pain Urgent desire to defecate Hematochezia within 24 hours Location: Sigmoid 23% Descending-to-sigmoid 11% Cecum-to-hepatic flexure 8% (worse prognosis) Descending 8% Pancolonic 7%

Diagnosis CT scan If nonspecific, colonoscopy within 48 hours Unprepped, low air Colon single-stripe sign Line of erythema with erosion or ulceration along the longitudinal axis of the colon Milder course

Colonoscopy

Treatment NPO, IVF, antibiotics EKG, Holter, echo Colonic infarction Laparotomy and resection Serosa can be misleading Segmental Ulcerating Colitis Recurrent fevers and sepsis Continuing or recurrent bloody diarrhea Persistent or chronic diarrhea with protein-losing colopathy Treat by resection

Treatment Ischemic Stricture Universal Fulminant Colitis Dilation or resection  Universal Fulminant Colitis Colectomy with ileostomy Isolated Ischemia of the Right Colon Check CTA for concurrent AMI Carcinoma/Obstructive Lesions (<5%) Lesion distal, increased intracolonic pressure proximal Irritable Bowel Syndrome Colon ischemia 3.4 to 3.9x more common ?Hypersensitivity of the colonic vasculature Complicating Aortic Surgery Up to 7% of surgeries (60% for ruptured aneurysm) Colonoscopy within 2-3 days if high risk Ex: ruptured aneurysm, prolonged cross-clamping time, post-op diarrhea

Chronic Mesenteric Ischemia “Intestinal angina” Mesenteric atherosclerosis Pain from small bowel ischemia Blood stolen to meet increased gastric demand from food

Clinical Features Gradual cramping discomfort within 30 minutes of eating, resolves over hours Fear of eating, weight loss Nonhealing antral ulcers without H. pylori 1/3 to ½: cardiac, cerebral, peripheral vascular disease Exam Abdomen soft and nontender Bruit common but nonspecific

Diagnosis Gastric tonometry exercise testing (GET) NG tube and arterial line Patient on PPI Obtain gastric juice and arterial blood fasting, during, after exercise Measure gastric-arterial Pco2 gradients Increase after exercise indicates ischemia Combine with duplex U/S Angiography Should show occlusion of ≥2 splanchnic arteries Does not make diagnosis in itself

Treatment Revascularization Need occlusive involvement of ≥2 major arteries Surgical if healthy Otherwise percutaneous +/- stent