Term
| what are the typical causes of intestinal obstruction? |
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Definition
| hernias, adhesions, volvulus, intussusception, and L-sided tumors |
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Term
| what is the definition of a hernia? what may one result in? |
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Definition
| a serosa-lined pouch of peritoneum which may protrude externally due to a weakness in the peritoneal cavity wall. this can result in obstruction of venous outflow and enlargement of the hernia sac, making it difficult to reduce - which can then lead to entrapment which in turn can cause arterial and venous compromise which can cause infarction. |
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Term
| who are inguinal hernias more common in? |
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Definition
| men, b/c their anatomy allows for testes ascent |
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Term
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Definition
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Term
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Definition
| acute peritoneal inflammation can lead to the formation of fibrous bridges between bowel segments, the abdominal wall and operative sites. eventually portions of the bowel may become entrapped, leading to infarction. |
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Term
| what is volvulus? what can it cause? what can it lead to? |
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Definition
| a complete twisting of a loop of bowel around its mesenteric base of attachment, which can cause vascular/luminal obstruction (can be initiated by adhesions). it is most commonly seen in the sigmoid colon, followed by the cecum, small bowel and stomach. it can occur spontaneously in children. |
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Term
| what is intussusception? what can this result in? who does this happen in more commonly? how is it treated? |
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Definition
| intussusception occurs when a portion of the intestine moves via peristaltic movement and telescopes into the immediately distal portion of the bowel. this may result in vascular obstruction and subsequent infarction. in *children this may be due to an anatomic defect or *rotavirus (due to lymphoid aggregates). in older children/adults, this may be due to an intraluminal mass (such as colon CA). this can be treated by barium enema in children, but requires sx intervention in older children/adults. |
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Term
| what is ischemic bowel disease? |
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Definition
| disease due to acute obstruction of an artery (celiac and superior/inferior mesenteric) which may lead to infarction of several meters of intestine. |
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Term
| what are some common causes of acute obstruction which could lead to ischemic bowel disease? |
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Definition
| atherosclerosis, aortic aneurysms, hypercoagulable states, oral contraception, embolization of cardiac vegetations and aortic atheromas, shock, dehydration or vasoconstrictive drugs |
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Term
| how does the bowel respond to hypoxia? |
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Definition
| at onset of vascular compromise, only minimal damage may occur if hypoxia is transient - the *most damage occurs when the blood supply is restored and the bowel undergoes reperfusion injury. |
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Term
| what is reperfusion injury? |
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Definition
| release of inflammatory factors, free radical production, release of neutrophils, activation of intracellular signaling molecules and transcription factors. |
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Term
| what does the severity of damage due to ischemic bowel disease depend on? |
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Definition
| the time frame during which the occlusion develops and the number of and specific vessels affected |
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Term
| are there portions of the bowel which are more prone to hypoxic damage? |
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Definition
| intestinal portions at the end of the arterial segment - therefore localized ischemia can develop from generalized hypotension and hypoxia |
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Term
| how is the surface epithelium of the bowel more vulnerable to injury? |
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Definition
| the intestinal capillaries run along glands from crypt to surface (which is labile - constantly overturning) in a somewhat tortuous fashion |
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Term
| what are the three kinds of infarction possible in ischemic bowel disease? |
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Definition
| transmural, mural and mucosal infarction |
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Term
| what characterizes mucosal and mural infarction? where does can it occur? how does it appear? |
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Definition
| in mucosal and mural infarction, which can occur anywhere in the GI, the lesions are often patchy/segmental, the mucosa is hemorrhagic, ulcerated, dark red/purple, edema thickens the bowel wall and involves the mucosa (may involve the submucosa/muscularis propria). mucosal and mural infarctions are less severe. |
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Term
| what characterizes transmural infarction? where does can it occur? how does it appear? |
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Definition
| transmural infarction involves substantial portions of the bowel due to *acute arterial occlusion and appears as red edematous bowel w/possible perforation as the *coagulation necrosis progresses and involves the muscularis propria. there is a clear demarcation between normal and ischemic bowel and the *splenic flexure is the site of greatest risk due to the fact that it is supplied by vessels at an end of an arterial supply. transmural infarction is more severe. |
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Term
| what is a mesenteric venous thrombosis? |
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Definition
| a venous thrombosis which over time prevents drainage, leading to backing up of blood flow, which can eventually develop changes similar to those seen in arterial occulusion. |
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Term
| what is the morphologic presentation of mesenteric venous thrombosis? |
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Definition
| atrophy of the surface epithelium, acute inflammation w/neutrophils, and chronic ischemia which may result in a fibrotic lamina propria w/possible stricture formation |
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Term
| what does presentation of ischemic bowel disease depend on? |
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Definition
| how quickly the occlusion occurs |
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Term
| how do pts with ischemic bowel disease generally present? |
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Definition
| abdominal pain/distention, vomiting (can't pass bowel contents), bloody stool (shedding off infarcted mucosa), fever (acute inflammatory response), and life-threatening sepsis (esp with a bowel perforation). chronic ischemia may mimic inflammatory bowel disease |
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Term
| what are other causes of ischemic bowel disease? |
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Definition
| CMV (infects endothelial cells = ischemia), radiation exposure, and necrotizing enterocolitis (acute, usually transmural necrosis often seen in premature/low birth weight babies) |
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Term
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Definition
| abnormal blood vessel formation, typically in the mucosa/submucosa in the R bowel and cecum which can cause distention/contraction due to mechanical factors. bowel affected by it appears hyperemic w/dilated and tortuous vessels. generally pts present @ > 40 yrs with R abdominal pain (mimics appendicitis) and blood in stool. |
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Term
| what is meckel's diverticulum? |
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Definition
| persistence of the solitary *vitelline duct (remnant of an attachment to umbilicus) located along the antimesenteric border. it can lead to ulceration/bleeding w/perforation or irritation by things being lodged in it. there may be *ectopic pancreatic tissue within the affected portion of bowel and it is not a problem itself, but it can lead to complications. men are more commonly affected. |
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Term
| what is colonic diverticulosis? |
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Definition
| a blind pouch lined by mucosa which can communicate with the lumen - most often found in the sigmoid colon. they are not a problem unless they become inflamed = diverticulitis, irritated by seeds and which can lead to abscesses/LLQ pain, and fever. (more prevalent in western countries, maybe due to a more refined diet that requires an increase in peristalsis, which requires an increase in intra-luminal pressure) |
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Term
| how is colonic diverticulosis treated? |
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Definition
| if severe - a portion of the bowel may be removed. otherwise a high fiber diet and avoidance of food w/a lot of seeds, etc. |
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Term
| who does acute appendicitis usually affect? |
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Definition
| males in their 2nd-3rd decade |
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Term
| what will usually cause acute appendicitis? |
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Definition
| obstruction: fecalith, gallstones, tumor (esp carcinoid), and intestinal worms |
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Term
| what is acute appendicitis characterized by? |
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Definition
| neutrophilic infiltration, anorexia, and RLQ pain |
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Term
| what are the different kinds of appendix tumors? |
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Definition
| carcinoids (most common), mucocele (dilation of the appendix by mucinous secretion), mucinous cystadenoma, and mucinous cystadenocarcinoma. |
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