Small bowel disorders

Question 1

What are the two main types of contractile activity in the small intestine?

Answer 1

• 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

Question 2

Differentiate the fed vs fasting pattern of motility in the small intestine

Answer 2

• fed: isolated contractions over short lengths, do not propagate
• fasting: after a meal, movement of increasing frequency and amplitude that propagates down the intestine

Question 3

Differentiate luminal vs membrane digestion

Answer 3

• 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

Question 4

Give an example of absorption by passive diffusion

Answer 4

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

Question 5

Give an example of absorption by active diffusion

Answer 5

absorption of glucose, galactose, and free amino acids using a sodium-coupled cotransporter

Question 6

Give an example of absorption by facilitated diffusion

Answer 6

absorption of fructose via specific carrier protein

Question 7

Where is vitamin B12 absorbed?

Answer 7

terminal ileum

Question 8

Where are bile salts absorbed?

Answer 8

terminal ileum

Question 9

Where is folate absorbed?

Answer 9

jejunum

Question 10

Describe the pathophysiology of ischemia of the small intestine

Answer 10

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.

Question 11

The classic presentation of _______ is severe acute abdominal pain out of proportion to exam

Answer 11

acute ischemia

Question 12

In acute ischemia, labs for ____ and ____ are elevated

Answer 12

WBCs and lactate (lactic acidosis)

Question 13

Chronic ischemia presents with ______ and_____

Answer 13

post prandial abdominal pain and sitophobia, weight loss

Question 14

What does imaging for acute ischemia show

Answer 14

CT imaging that may reveal air within the intestinal wall, as well as portal venous gas.

Question 15

The most common cause of _______ is underlying atherosclerotic disease in people with diabetes, hypertension, and hyperlipidemia

Answer 15

chronic ischemia

Question 16

What is the treatment for ischemia of the small bowel?

Answer 16

restoration of blood flow by vascular surgery or interventional radiology

Question 17

What is the pathophysiology of small intestine obstruction?

Answer 17

narrowing of the small intestinal lumen that leads to proximal dilation of the intestine and accumulation of GI secretions and swallowed air

Question 18

________ can lead to vascular compromise and small bowel ischemia

Answer 18

complete obstruction

Question 19

Describe the presentation of small bowel obstruction

Answer 19

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

Question 20

In small bowel obstruction, bowel sound are initially ______ then eventually ______

Answer 20

hyperactive then hypoactive

Question 21

Describe imaging for small bowel obstruction

Answer 21

abdominal X ray showing dilated small bowel with multiple air-fluid levels
CT can aid in finding the transition point/ cause of SBO

Question 22

List some major causes of small bowel obstruction

Answer 22

post-operative adhesions, tumors, Crohn disease, incarcerated hernias

Question 23

What is the treatment for SBO?

Answer 23

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

Question 24

What differentiates ileus from small bowel obstruction?

Answer 24

In ileus, instead of a narrowing of the small intestine lumen, the cause of obstructive symptoms is a lack of motility

Question 25

What is the pathophysiology of ileus?

Answer 25

Absolute failure of intestinal contractions and subsequent lack of propulsion of gut motility

Question 26

Describe the presentation of ileus

Answer 26

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

Question 27

Describe imaging seen in ileus

Answer 27

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

Question 28

List common causes of ileus

Answer 28

post operative state
electrolyte abnormalities 
drugs- narcotics, CCBs, anticholinergics
sepsis, pancreatitis, peritonitis
scleroderma, CT disorder
Parkinson's, institutionalized patients

Question 29

How is ileus treated?

Answer 29

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

Question 30

What is the pathophysiology of diverticulosis?

Answer 30

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

Question 31

How does diverticulosis present?

Answer 31

Non specific symptoms of upper abdominal discomfort, bloating, early satiety

Question 32

How is diverticulosis diagnosed?

Answer 32

Barium small bowel follow through with hydrogen breath test

Question 33

What are causes of diverticulosis?

Answer 33

Scleroderma

Visceral neuropathies, visceral myopathies

Question 34

How is diverticulosis treated?

Answer 34

intermittent antibiotics, surgical resection (rare)

Question 35

What is the pathophysiology of short gut syndrome?

Answer 35

Malabsorption due to resection of >70% of small intestine

Question 36

Resection of the ileum specifically leads to problems with reabsorption of:

Answer 36

B12 and bile acids

Question 37

What is the presentation of short gut syndrome?

Answer 37

dehydration, malnutrition, diarrhea

Question 38

How is short gut syndrome treated?

Answer 38

Enteral feeding via intestinal tube or TPN
octreotide or clonidine to decrease fluid secretions
loperamide, lomotil, codeine for diarrhea
cholestyramine for bile malabsorption

Question 39

What are some complications of small bowel ischemia?

Answer 39

Bowel infarction
sepsis
bowel perforation