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
What is this?
What is Pseudomembranous colitis?
Pseudomembranous colitis, also called antibiotic-associated colitis or C. difficile colitis, is inflammation of the colon associated with an overgrowth of the bacterium Clostridium difficile (C. diff). This overgrowth of C. difficile is most often related to recent antibiotic use. (•Immunosuppression is also a predisposing factor)
How does Pseudomembranous colitis present histologically?
•Adherent layer of inflammatory cells and debris.
•The surface epithelium is denuded
•The superficial lamina propria contains a dense infiltrate of neutrophils.
•Superficially damaged crypts are distended by a mucopurulent exudate that forms an eruption reminiscent of a volcano.
These exudates coalesce to form pseudomembranes.
Lamina propria will not show hyalinization like ischemia
Tenderness and bleeding appear late in case of acute mesenteric ischemia
Pain usually appears during the first hour after eating and last for two to three hours.
Weight loss present in about 80 percent of patients as the result of food aversion.
Frequently patients with chronic mesenteric iscehmia have history of what?
underlying atherosclerotic vascular disease
What are the main risk factors for mesenteric venous thrombosis?
hypercoagulable states, portal hypertension, abdominal infections, blunt abdominal trauma, pancreatitis, splenectomy and malignancy in the portal region.
How does venous mesenteric ischemia affect the GI?
Venous thrombosis produces resistance in mesenteric venous blood flow, bowel wall edema, fluid efflux into the bowel lumen, increased blood viscosity and finally compromise of the arterial blood support.
What is 'upper' GI bleeding defined as?
above the ligament of Treitz
What is obscure bleeding?
bleeding without a clear source
Obscure overt bleeding: macroscopic obscure bleeding
Obscure occult: microscopic obscure bleeding. This is a chronic bleeding frequently presenting as iron deficiency anemia
What is Melena?
black, tarry, loose or sticky, malodorous stool caused by degraded blood in intestine and generally indicates an upper GI source, although it may originate in the right colon
What is hematochezia?
bright red blood from the rectum. It may be mixed with stools and usually indicates a lower GI lesions. When hematochezia is caused by an upper GI source, it indicates a massive hemorrhage
What is the most frequent source of GI bleeding?
acute upper GI bleed (Upper GI bleeding is five times more frequent than lower GI bleeding)
How are acute upper GI bleeds managed?
In general the management include the following
1:stabilization of hemodinamic status
2: determine the source
3:stop active bleeding
4: prevent recurrent bleeding
In case of GI bleeding the main aspects to investigate through the medical history include the following:
History of peptic disease,
recent use of NSAID,
alcohol or caustic ingestion,
cirrhosis, aortic graft surgery,
cancer, recent nose bleed
What things should be examined on physical exam for a GI bleed?
stigmata of cirrhosis,
What are some common causes of upper GI bleeding?
•Gastritis and duodenitis
In gastric ulcer we always have to consider malignancy as part of the differential. These patient require a surveillance endoscopy to document ulcer’s healing.
What is the cause in 16% of patients with upper GI bleeding?
Gastric erosions, defined as a Break in the mucosa that does not cross the muscularis mucosa Endoscopically less than 3-5mm and without significant depth
How do esophageal varices form?
•Venous blood from the GI tract passes through the liver, via the portal vein, before returning to the heart.
•Portal hypertension results in the development of collateral channels at sites where the portal and caval systems communicate.
•These collateral veins allow some drainage to occur, but at the same time they lead to development of congested subepithelial and submucosal venous plexi within the distal esophagus and proximal stomach =varices
What are the main causes of esophagel varices?
cirrhotic patients, hepatic schistosomiasis
What are Mallory Weiss tears?
lacerations in the region of the gastro-esophageal junction caused by retching with forceful gastric mucosa prolapse
Accounts for 5-10 UGI bleeds
History of vomiting
Usually resolves with conservative management
Bleeding from Mallory—Weiss tears stops spontaneously in 80 % to 90% of patients, and less than 5% of patients rebleed
Treatment include hemodynamic stabilization and endoscopic treatment. Angiography or surgery are rarely required.
8% of UGI bleeding
GERD is the most frequent
Infections (CMV, herpes)
What are some common GI vascular malformations?
•Gastric Antral Vascular Ectasia (GAVE)- Watermelon stomach
Vascular Ectasias: Chronic bleeding, frequently occult, presenting as iron deficiency anemia, frequently multiple, treatment: endoscopic
GAVE: Ectatic and saculated mucosal vessels, bleeding usually chronic and occult as vascular ectasias, idiopathic but more frequent in pts with portal hypertension (but not required) , Treatment: Endoscopic
Dieulafoi: Idiopathic, dilated submucosal vessel overlying the epithelium without ulcer, caliber of the artery is 1-3 mm, usually proximal stomach
bleeding can be profuse
Neoplasms represent ___% of UGI bleeds
Etiology of small-bowel bleeding
What is the best procedure available to study small intestine mucosa?
It is extremely helpful in the investigation in patient with occult bleeding
What is the most common cause of acute LGI bleed?
Diverticulosis and angiodysplasia
What is the most common cause of chronic LGI bleed?
Hemorrhoids and neoplasia
What is Diverticulosis?
Diverticulosis is the condition of having diverticula in the colon that are not inflamed. These are outpockets of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall. They typically cause no symptoms. Diverticular disease occurs when diverticula become inflamed, known as diverticulitis, or bleed
How common is diverticular bleeding?
3% of diverticulosis pts. with 70% of bleeding occuring from the right side
How does diverticular bleeding present?
Acute, painless, maroon to bright red hematochezia
Bleeding is often significant but will stop spontaneously in 70:80% of patients and 25-35% will have a recurrent episode of bleeding
What is the Most common cause of lower GI bleeding?
Diverticuli bleeding, from penetration of a colonic artery into the dome of a diverticula
3:5 % of patient with diverticulosis will bleed. 10-35 % will rebleed.
What is the tx of diverticular bleeding?
Include hemodynamic stabilization and endoscopic treatment. Angiography with embolization and surgery are the option in patients with persistent bleeding.
What is angiodysplasia?
angiodysplasia is a small vascular malformation of the gut. It is a common cause of otherwise unexplained gastrointestinal bleeding and anemia. Lesions are often multiple, and frequently involve the cecum or ascending colon, although they can occur at other places.
What are some causes of angiodysplasia?
•Chronic renal failure
•Prior radiation therapy
WHat is this?
Colon cancer should be always considered in the differential of lower GI bleeding.
The most common presentation is occult GI bleeding
Always consider colon malignancy in patients older than 50 presenting with iron deficiency anemia.