Small bowel disorders Flashcards
What are the two main types of contractile activity in the small intestine?
- segmentation: cylindrical contraction and relaxation of inner circular muscle layer, important for mixing
- peristalsis: aka migrating myoelectric complex, waves of contractile activity that begin after food ingestion and pass sequentially down the intestine, important for propulsion
Differentiate the fed vs fasting pattern of motility in the small intestine
- fed: isolated contractions over short lengths, do not propagate
- fasting: after a meal, movement of increasing frequency and amplitude that propagates down the intestine
Differentiate luminal vs membrane digestion
- luminal: occurs in lumen as a result of secreted digestive enzymes (bile, pancreatic enzymes)
- membrane: contact digestion at the apical surface of enterocytes by lactase, sucrase, maltase
Give an example of absorption by passive diffusion
diffusion of monoglycerides and fatty acids across the lipid bilayer after delivery of these products to the apical surface of the intestinal cells via mixed micelles
Give an example of absorption by active diffusion
absorption of glucose, galactose, and free amino acids using a sodium-coupled cotransporter
Give an example of absorption by facilitated diffusion
absorption of fructose via specific carrier protein
Where is vitamin B12 absorbed?
terminal ileum
Where are bile salts absorbed?
terminal ileum
Where is folate absorbed?
jejunum
Describe the pathophysiology of ischemia of the small intestine
Mesenteric ischemia occurs when there is a reduction in blood flow to the intestine, which can result from embolic or thromboembolic event, vascular occlusion, vasospasm, or general hypoperfusion.
The classic presentation of _______ is severe acute abdominal pain out of proportion to exam
acute ischemia
In acute ischemia, labs for ____ and ____ are elevated
WBCs and lactate (lactic acidosis)
Chronic ischemia presents with ______ and_____
post prandial abdominal pain and sitophobia, weight loss
What does imaging for acute ischemia show
CT imaging that may reveal air within the intestinal wall, as well as portal venous gas.
The most common cause of _______ is underlying atherosclerotic disease in people with diabetes, hypertension, and hyperlipidemia
chronic ischemia
What is the treatment for ischemia of the small bowel?
restoration of blood flow by vascular surgery or interventional radiology
What is the pathophysiology of small intestine obstruction?
narrowing of the small intestinal lumen that leads to proximal dilation of the intestine and accumulation of GI secretions and swallowed air
________ can lead to vascular compromise and small bowel ischemia
complete obstruction
Describe the presentation of small bowel obstruction
crampy intermittent abdominal pain, nausea, vomiting, abdominal distention, hyperactive then hypoactive bowel sounds
loose stools in partial SBO
no stools or flatus in complete SBO
In small bowel obstruction, bowel sound are initially ______ then eventually ______
hyperactive then hypoactive
Describe imaging for small bowel obstruction
abdominal X ray showing dilated small bowel with multiple air-fluid levels
CT can aid in finding the transition point/ cause of SBO
List some major causes of small bowel obstruction
post-operative adhesions, tumors, Crohn disease, incarcerated hernias
What is the treatment for SBO?
NPO, IVF, nasogastric tubes with suction to decompress the intestine
medical treatment or stricturoplasty in Crohn’s
surgical lysis of adhesions or resection of tumors
What differentiates ileus from small bowel obstruction?
In ileus, instead of a narrowing of the small intestine lumen, the cause of obstructive symptoms is a lack of motility
What is the pathophysiology of ileus?
Absolute failure of intestinal contractions and subsequent lack of propulsion of gut motility
Describe the presentation of ileus
Presentation of an ileus includes abdominal pain, nausea, vomiting, abdominal distention, and absence of flatus/bowel movements
Exam shows a distended abdomen that is diffusely tender and tympanitic
Describe imaging seen in ileus
Abdominal x-ray shows dilated loops of small bowel with air-fluid levels and a paucity of gas in the colon
CT to rule out obstruction
List common causes of ileus
post operative state electrolyte abnormalities drugs- narcotics, CCBs, anticholinergics sepsis, pancreatitis, peritonitis scleroderma, CT disorder Parkinson's, institutionalized patients
How is ileus treated?
NPO, IVF, nasogastric tube with suction
ambulate if possible
stop unnecessary medications
replace electrolytes
may require enteral nutrition, short course of antibiotics, prokinetics (metoclopramide, erythromycin)
in colonic ileus, there is concern of perforation
What is the pathophysiology of diverticulosis?
Pockets of mucosa and submucosa that can be found in the setting of a motility disorder, can be complicated by malabsorption secondary to bacterial overgrowth
How does diverticulosis present?
Non specific symptoms of upper abdominal discomfort, bloating, early satiety
How is diverticulosis diagnosed?
Barium small bowel follow through with hydrogen breath test
What are causes of diverticulosis?
Scleroderma
Visceral neuropathies, visceral myopathies
How is diverticulosis treated?
intermittent antibiotics, surgical resection (rare)
What is the pathophysiology of short gut syndrome?
Malabsorption due to resection of >70% of small intestine
Resection of the ileum specifically leads to problems with reabsorption of:
B12 and bile acids
What is the presentation of short gut syndrome?
dehydration, malnutrition, diarrhea
How is short gut syndrome treated?
Enteral feeding via intestinal tube or TPN
octreotide or clonidine to decrease fluid secretions
loperamide, lomotil, codeine for diarrhea
cholestyramine for bile malabsorption
What are some complications of small bowel ischemia?
Bowel infarction
sepsis
bowel perforation
