GI: Small and large intestine Flashcards
How do you initially manage someone with chronic diarrhea, >50 yo and <50 yo?
Patients older than 50 years should undergo colonoscopy to screen for colorectal cancer. Patients younger than 50 years should also have colonoscopy if features of inflammatory bowel disease are present. Any patient undergoing colonoscopy to evaluate diarrhea should have inspection of the terminal ileum (to assess for Crohn disease) and random biopsies of the colonic mucosa (to assess for microscopic colitis). Sigmoidoscopy is not recommended in most patients because it does not evaluate the proximal colon or terminal ileum.
In evaluation of diarrhea, if colonoscopy is negative what test do you go for next?
A 48- to 72-hour stool collection with analysis of fat content measures the amount of diarrhea and steatorrhea.
What fat excretion is diagnostic of steatorrhea? What diagnoses could this be?
Normal fat excretion is less than 7 g/d (in patients consuming 100 g/d of fat); however, this may be increased nonspecifically by any diarrheal disorder to 12 to 14 g/d. Fat excretion above 14 g/d is diagnostic of steatorrhea. Patients with steatorrhea should undergo evaluation for small-bowel mucosal disorders (celiac disease, Whipple disease), small intestinal bacterial overgrowth (SIBO), and pancreatic insufficiency.
What if a fat test of diarrhea demonstrates that it has no steatorrhea? Then what?
In patients with true diarrhea but without steatorrhea, measurement of stool electrolytes can be helpful to categorize the diarrhea so that more targeted testing can later be performed. Measurement of fecal sodium and potassium allows calculation of the osmotic gap, as follows:
290 – (2 × [stool sodium + stool potassium])
> 100 mOsm/kg (100 mmol/kg): Osmotic diarrhea
<50 mOsm/kg (50 mmol/kg), the diarrhea is secretory rather than osmotic.
50 and 100 mOsm/kg (50 and 100 mmol/kg) is equivocal
What is the stool osmotic gap? How is it used?
It helps separate out secretory diarrhea from osmotic diarrhea.
What is the differential for malabsorption/steatorrhea?
1) Celiac Disease
2) Small Intestinal Bacterial Overgrowth
3) Short Bowel Syndrome
4) Carbohydrate malabsorption
What is celiac disease?
Celiac disease is a chronic inflammatory enteropathy caused by an immune-mediated reaction to gluten and gliadins, proteins that are present in wheat and other grains.
How do you diagnose celiac disease? What are the serological makers?
The diagnosis of celiac disease requires positive serologic markers and a compatible small-bowel biopsy.
IgA tissue transglutaminase (tTG) antibodies and endomysial antibodies (EMA) are sensitive and specific serologic markers; testing for these should be done while the patient is consuming gluten.
What are the histological findings of celiac disease?
The classic findings on small-bowel histology are intraepithelial lymphocytosis, crypt elongation, and villous blunting
What is a lab abnormality that gives a clue to SIBO?
A clue to the diagnosis of SIBO is the combination of vitamin B12 deficiency (due to bacterial consumption) and an elevated serum folate level (due to bacterial production).
What are common causes of SIBO?
Diabetes, gastric bypass surgery
What is short bowel syndrome?
Short-bowel syndrome (SBS) arises when a large portion of the small intestine is resected or diseased. Causes of SBS are massive resection or bowel dysfunction related to ischemia, radiation enteropathy, Crohn disease, or trauma.
How much healthy intestine that remains causes short bowel?
Short-bowel syndrome arises when a large portion of the small intestine is resected or diseased; it typically does not occur until less than 200 cm of healthy small intestine remains.
How does ulcerative colitis present?
UC typically presents with bloody diarrhea and abdominal discomfort, the severity of which is related to the extent and severity of inflammation. Because UC typically involves the rectum, tenesmus, urgency, rectal pain, and fecal incontinence are common. Fever and weight loss are uncommon and suggest severe disease.
What is the distribution of ulcerative colitis?
The distribution of UC is generally divided into proctitis (involving the rectum only), left-sided colitis (inflammation does not extend beyond the splenic flexure), and pancolitis (inflammation extends above the splenic flexure).
How does Crohn’s disease present?
Common symptoms of CD are abdominal pain, diarrhea, and weight loss; fever and overt gastrointestinal bleeding are less common than is typically seen in UC.
What does the mucosa look like in Crohn’s disease? What is it’s distribution?
Additionally, unlike UC, the transmural inflammation seen in CD may predispose to fistula formation. Given the variable distribution of inflammation in CD, the symptoms can vary considerably between patients. Thirty percent of patients have isolated small-bowel disease, 40% have ileocolonic inflammation, and 25% have isolated colonic disease. The other 5% of patients have isolated upper gastrointestinal or perianal manifestations. Symptoms correlate with disease location.
*Ulcerative colitis extends throughout, Crohn’s can be certain discreet locations
What lab abnormalities suggest severe UC or Crohn’s?
y. Leukocytosis, anemia, hypoalbuminemia, and vitamin deficiencies indicate more severe disease. The erythrocyte sedimentation rate and C-reactive protein levels are often elevated; if so, these levels can be monitored as signs of response to therapy and subsequent disease flare.
