Mesenteric Ischemia

Overview

Definition

Mesenteric ischemia is a condition caused by hypoperfusion of the intestine, resulting in ischemia and necrosis. Mesenteric ischemia is categorized based on the time course:

• Acute mesenteric ischemia: caused by a sudden decrease in blood flow
• Chronic mesenteric ischemia: episodic, recurrent, or constant intestinal hypoperfusion

Anatomy

The main vessels affected in mesenteric ischemia include:

• Superior mesenteric artery ( SMA SMA Spinal muscular atrophy (SMA) is a spectrum of autosomal recessive syndromes characterized by progressive proximal muscle weakness and atrophy, possibly due to degeneration of the anterior horn cells in the spinal cord and motor nuclei in the lower brainstem. Spinal Muscular Atrophy (SMA)):
  • Most commonly affected
  • Supplies the midgut (distal duodenum to proximal ⅔ of the transverse colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix)
• Inferior mesenteric artery: supplies the hindgut (distal ⅓ of transverse colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix to anal canal above pectinate line)

Pathophysiology

• The intestinal tract has a ↑ metabolic rate → requires ↑ blood flow
• Disruption in blood flow → ischemic changes within 15 minutes:
  • May cause a reactive vasospasm → ↓ collateral blood flow
  • Bowel hypoxia → bowel wall spasm → symptoms:
    • Vomiting
    • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea
  • May depend on:
    • Adequacy of perfusion
    • Any collateral circulation
    • Number of vessels affected
• Mucosal damage and sloughing occurs within 3 hours and can lead to:
  • Gastrointestinal bleeding Gastrointestinal bleeding Gastrointestinal bleeding (GIB) is a symptom of multiple diseases within the gastrointestinal (GI) tract. Gastrointestinal bleeding is designated as upper or lower based on the etiology's location to the ligament of Treitz. Depending on the location of the bleeding, the patient may present with hematemesis (vomiting blood), melena (black, tarry stool), or hematochezia (fresh blood in stools). Gastrointestinal Bleeding and visceral pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Release of vasoactive mediators, bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview, and toxic byproducts; resulting in:
    • Cardiac failure
    • Systemic inflammatory response syndrome (SIRS)
    • Multisystem organ failure
• Bowel wall becomes cyanotic and edematous → fluids released into peritoneal cavity
• Necrosis occurs within 6 hours → peritoneal signs

Chronic Mesenteric Ischemia

Epidemiology

• Rare
• 60% of cases are inpatients > 60-years-old.
• More common in women

Etiology

Chronic mesenteric ischemia is caused by a progressive stenosis of ≥ 2 arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries, resulting in episodes of blood flow supply and demand mismatch (usually after eating).

• The majority of cases are due to atherosclerotic disease narrowing the origin of the mesenteric vessels.
• Rare causes: 
  • Vasculitis
  • Fibromuscular dysplasia Fibromuscular dysplasia Fibromuscular dysplasia (FMD) is a nonatherosclerotic, noninflammatory, medium-sized angiopathy due to fibroplasia of the vessel wall. The condition leads to complications related to arterial stenosis, aneurysm, or dissection. Fibromuscular Dysplasia
  • Artery dissection
  • Retroperitoneal fibrosis
  • Median arcuate ligament syndrome: celiac artery compression by the arcuate ligament of the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm
  • Endovascular repair of the aorta

Clinical presentation

• Episodic abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain:
  • Referred to as “intestinal angina” 
  • Dull and crampy
  • Epigastric
  • Varies in intensity
  • Postprandial:
    • Occurs within 1 hour after eating
    • Resolves over the following 2 hours
• Food fear:
  • Due to postprandial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Leads to significant weight loss in 80% of patients
• Abdominal bruit: present in 50% of patients
• Less common signs and symptoms:
  • Nausea and vomiting
  • Early satiety
  • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea
  • Gastrointestinal bleeding Gastrointestinal bleeding Gastrointestinal bleeding (GIB) is a symptom of multiple diseases within the gastrointestinal (GI) tract. Gastrointestinal bleeding is designated as upper or lower based on the etiology's location to the ligament of Treitz. Depending on the location of the bleeding, the patient may present with hematemesis (vomiting blood), melena (black, tarry stool), or hematochezia (fresh blood in stools). Gastrointestinal Bleeding
• Beware of acute-on-chronic mesenteric ischemia:
  • May occur due to thrombus formation in a patient with chronically stenotic vessels.
  • Associated with a ↑ morbidity and mortality
  • Symptoms similar to acute mesenteric ischemia.

Diagnosis

Vascular imaging studies are used to make the diagnosis.

• CT angiography: 
  • Preferred diagnostic modality
  • Should demonstrate high-grade stenosis of ≥ 2 major mesenteric arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
• Duplex ultrasound of mesenteric vessels: can be used as a screening study

Management

• Conservative treatment:
  • Preferred for:
    • Incidental diagnosis
    • No overt clinical manifestations
  • Focuses on limiting the progression of atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis:
    • Smoking cessation
    • Glycemic control
    • Antiplatelet therapy
• Nutritional support:
  • Necessary in patients with significant weight loss
  • Parenteral nutrition may be considered for severe cases.
• Revascularization:
  • Indications:
    • Symptoms and documented stenosis on imaging
    • Peritonitis
    • Gastrointestinal hemorrhage
  • Goal: Prevent future bowel infarction.
  • Options:
    • Endovascular approach with stenting and/or angioplasty
    • Open surgical approach for endarterectomy or bypass

Differential Diagnosis

• Small bowel obstruction Small Bowel Obstruction Small bowel obstruction (SBO) is an interruption of the flow of the intraluminal contents through the small intestine, and is classified as mechanical (due to physical blockage) or functional (due to disruption of normal motility). The most common cause of SBO in the Western countries is post-surgical adhesions. Small bowel obstruction typically presents with nausea, vomiting, abdominal pain, distention, constipation, and/or obstipation. Small Bowel Obstruction: an interruption of intraluminal contents through the small bowel due to a mechanical or functional problem. Patients present with abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, distention, nausea, vomiting, and obstipation. Diagnosis is confirmed with abdominal imaging. Conservative management is usually the 1st step; nil per os (NPO), IV fluids, and NG tube decompression. Some patients fail conservative management and require surgery to relieve the obstruction.
• Spontaneous bacterial peritonitis (SBP): an acute bacterial infection of the peritoneal fluid (a well-known complication in patients with cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis). Individuals present with abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, distension, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and chills. Physical exam demonstrates a significantly tender abdomen. If SBP is suspected, patients require paracentesis with ascitic fluid analysis and culture. The treatment of choice is antibiotics.
• Acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis: inflammation of the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract resulting from sustained gallstone impaction of the cystic duct. Patients present with colicky, upper abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, nausea, and vomiting. Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract and gallstones are seen on ultrasound or CT. Management includes IV fluids, antibiotics, and cholecystectomy Cholecystectomy Cholecystectomy is a surgical procedure performed with the goal of resecting and extracting the gallbladder. It is one of the most common abdominal surgeries performed in the Western world. Cholecystectomy is performed for symptomatic cholelithiasis, cholecystitis, gallbladder polyps > 0.5 cm, porcelain gallbladder, choledocholithiasis and gallstone pancreatitis, and rarely, for gallbladder cancer. Cholecystectomy: Approaches and Technique.
• Peptic ulcer disease Peptic ulcer disease Peptic ulcer disease (PUD) refers to the full-thickness ulcerations of duodenal or gastric mucosa. The ulcerations form when exposure to acid and digestive enzymes overcomes mucosal defense mechanisms. The most common etiologies include Helicobacter pylori (H. pylori) infection and prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs). Peptic Ulcer Disease: ulcerations located in the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach and/or duodenum. Peptic ulcer disease Peptic ulcer disease Peptic ulcer disease (PUD) refers to the full-thickness ulcerations of duodenal or gastric mucosa. The ulcerations form when exposure to acid and digestive enzymes overcomes mucosal defense mechanisms. The most common etiologies include Helicobacter pylori (H. pylori) infection and prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs). Peptic Ulcer Disease may be caused by Helicobacter Helicobacter Helicobacter pylori is a gram-negative bacterium that causes gastric infection. It is the most well known and clinically significant species of Helicobacter. Transmission is believed to occur by ingestion of contaminated food or water; therefore, a higher prevalence of infection is seen in areas with poor sanitation. Helicobacter pylori (H. pylori) infection, medications (e.g., nonsteroidal antiinflammatory drugs Nonsteroidal Antiinflammatory Drugs Nonsteroidal antiinflammatory drugs (NSAIDs) are a class of medications consisting of aspirin, reversible NSAIDs, and selective NSAIDs. NSAIDs are used as antiplatelet, analgesic, antipyretic, and antiinflammatory agents. Nonsteroidal Antiinflammatory Drugs), lifestyle factors, or hypersecretory conditions. Patients may have dyspepsia, postprandial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, early satiety, nausea, or evidence of bleeding. The diagnostic test of choice is an upper endoscopy. Management includes lifestyle changes, H. pylori treatment, and proton pump inhibitors.
• Diverticulitis: inflammation or infection of a colonic diverticulum; potentially complicated by perforation, abscess, or fistula formation. Patients present with diffuse or left lower quadrant abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, nausea, vomiting, and fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever. Diagnosis is made with a CT scan. Management includes antibiotics and, in cases of perforation, surgical bowel resection.