Main arterial supply of the GI
Cardiac output: 7000 ml
Celiac artery 800 ml
SMA: 800 ml
IMA: 480 ml
Describe the SMA
It is responsible of giving the vascular support to pancreatico-duodenal area, small intestine and right colon. It arises approximately 1 cm below the celiac artery and runs toward the cecum, terminating as the ileo-colic artery.
A vast network of collateral blood vessel gives substantial protection from ischemia or infarction in a setting of segmental vascular occlusion
How do catecholamines affect splanchic circulation?
they are released in response to oligemic shock and cause vasoncontriction
How do Angio II and ADH affect splanchic circulation?
How do gastrin, CCK, and secretin affect splanchic circulation?
T or F. Ischemic changes are more common in the small than in the large bowel
What are some major categories of intestinal ischemia?
Decreased arterial supply
Decreased venous return
Low flow states (heart failure, hemorrhage, shock)
Depending on the layers affected, infarcts are classified as:
What are the main ischemic diseases of the GI tract?
•Acute mesenteric ischemia
•Chronic mesenteric ischemia
•Venous mesenteric ischemia
What is the ultimate cause of ischemic colitis?
Lack of BLOOD FLOW to the mucosa
The main symptoms of ischemic colitis center around whether it is occlusive or non-occlusive. What are some main causes of non-occlusive ischemic colitis and how does it present?
May occur spontaneously or be caused by hypotension, cardiac failure, sepsis and are either subclinical or produce mild symptoms
The main symptoms of ischemic colitis center around whether it is occlusive or non-occlusive. What are some main causes of occlusive ischemic colitis and how does it present?
Thrombosis or embolization of the mesenteric arteries
Ligation of IMA during aortic reconstruction or colon resection
Diffuse disease of small vessels (diabetes mellitus, vasculitis)
Venous outflow obstruction (intra-abdominal inflammatory processes, hypercoagulability states)
Extrinsic and intrinsic obstruction (tumor, adhesions, volvulus, rectal prolapse)
The outcome of ischemic colitis depends on what?
severity, extent, rapidity of onset, status of collateral circulation, ability of bowel wall to resist bacterial infection
Ischemic colitis most commonly affects the what areas?
Wateshed areas of colon that have limited collateral circulation such as the splenic flexure and rectosigmoid area.
Rectum is generally not involved.
Ischemic colitis (also spelled ischaemic colitis) is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia.
Causes of the reduced blood flow can include changes in the systemic circulation (e.g. low blood pressure) or local factors such as constriction of blood vessels or a blood clot. In most cases, no specific cause can be identified
Ischemic colitis can span a wide spectrum of severity; most patients are treated supportively and recover fully, while a minority with very severe ischemia may develop sepsis and become critically, sometimes fatally, ill
How are pts. with mild ischemic colitis tx?
Patients with mild to moderate ischemic colitis are usually treated with IV fluids, analgesia, and bowel rest (that is, no food or water by mouth) until the symptoms resolve. Those with severe ischemia who develop complications such as sepsis, intestinal gangrene, or bowel perforation may require more aggressive interventions such as surgery and intensive care. Most patients make a full recovery; occasionally, after severe ischemia, patients may develop long-term complications such as a stricture or chronic colitis
Mesenteric ischemia is a medical condition in which injury of the small intestine occurs due to not enough bloodsupply. It can come on suddenly, known as acute mesenteric ischemia, or gradually, known as chronic mesenteric ischemia
Acute disease often presents with sudden severe pain. Symptoms may come on more slowly in those with acute on chronic disease
How does AMI present?
Early abdominal pain without ileus (a painful obstruction of the ileum or other part of the intestine)
Peritoneal signs only in advanced disease
Not always blood
Signs and symptoms of chronic disease include abdominal pain after eating, unintentional weight loss, vomiting, and being afraid of eating.
What are some causes of occlusive AMI?
Embolism generally coming from atherosclerotic plaques: Origin of SMA
What are some causes of non-occlusive AMI?
significant reduction in mesenteric flow secondary to cardiac failure or hypovolemic shock
T or F. AMI is a medical or surgical emergency
T. Delay in the diagnosis and treatment may result in bowel necrosis
How is AMI diagnosed?
X-ray, CT showing thickened bowel wall, ileus, and portal vein gas
Angiography (70-100% sensitive; 100% specific)
What are the risk factors for AMI?
Risk factors include atrial fibrillation, heart failure, chronic renal failure, being prone to forming blood clots, and previous myocardial infarction
Three progressive phases of mesenteric ischemia have been described:
A hyper active stage occurs first, in which the primary symptoms are severe abdominal pain and the passage of bloody stools. Many patients get better and do not progress beyond this phase.
A paralytic phase can follow if ischemia continues; in this phase, the abdominal pain becomes more widespread, the belly becomes more tender to the touch, and bowel motility decreases, resulting in abdominal bloating, no further bloody stools, and absent bowel sounds on exam.
Finally, a shock phase can develop as fluids start to leak through the damaged colon lining. This can result in shock and metabolic acidosis with dehydration, low blood pressure, rapid heart rate, and confusion. Patients who progress to this phase are often critically ill and require intensive care.
Thumb printing represent edema of lamina propria
What is this showing?
Ischemic intestines (code phrase= 'dusky bowel'- May be salvageable, but the phrase is often used for infarcted bowel that needs surgical removal)
How does ischemic colitis present histologically?
•Superficial mucosal necrosis
•Hyalinized lamina propria
•Withered or atrophic crypts
•Chronic ulcers and strictures
What is this showing?
Pseudomembrane in ischemic bowel