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
