Iron is absorbed in the duodenum
B12 needs intrinsic factor from the stomach for absorption
bile salts are absorbed in the terminal ileum
Other symtpoms of global malabsorption
Borborygmi= hearing gut sounds
What are some gastric causes of malabsorption?
-autoimmune gastritis (pernicious anemia)
What are some pancreatic causes of malabsorption?
What are some endocrine causes of malabsorption?
If you suspect malabsorption, start with an H&P
What labs should you get for a suspected malabsorptive pt?
–CBC (are they anemic or macro/microcytic)
–Iron, B12, Folate
–Calcium / Vit D
•Malabsorption of ____ is most commonly used indicator of global malabsorption
Why is fat the best indicator for global malabsorption?
(1) among the macronutrients (fat, carbohydrates, and protein), the process by which fat is absorbed is the most complex and, therefore, it tends to be the most sensitive to interference from disease processes; and
(2) it is the most calorically dense macronutrient and, therefore, its malabsorption is a critical factor in the weight loss that often accompanies malabsorptive disorders.
How is fat malabsorption assessed?
Via a stool fat assessment. In healthy people, stool fat excretion is usually less than 6 gram daily (Stool fat remains constant with high fat diets, even greater than 125 grams fat daily). This can be increased in patients with are having diarrhea
Typically the diagnosis of steatorrhea requires 20+gm of fat/24hr
What are some qualitative ways to measure steatorrhea?
•72 hour stool collection is cumbersome and messy
•A Sudan stain for fat globules from a spot stool sample can detect > 90% of patients with steatorrhea (below)
How can you test for carbohydrate malabsorption?
–Can rely on fermentation of undigested carbohydrates by intestinal bacteria
–Or direct measurement of the absorption of specific nutrients after a test dose (Examples are the lactose tolerance test as well as several breath tests, which measure hydrogen or radioactive isotopes from sugars containing radionuclide carbon analogues.)
What is this?
Endoscopy of the duodenum showing Celiac sprue – notice “scalloping”
Diagnosis is made via biopsy
What is on the right (left= normal terminal ileum)?
Crohn's disease. These are not exudates (non-friable), but lesions with depth into the GI wall
Again, diagnosis requires biopsy
C: Chronic pancreatitis- notice how dilated and strictured it is
EUS (endoscopic ultrasound) of normal pancreas vs. chronic pancreatitis (right)
What is Celiac Sprue?
An Autoimmune disorder of small bowel leading to intolerance to gluten leading to global malabsorption
Symptoms can be subtle (diarrhea, bloating, etc. may or may not be present)
What is the gold standard for diagnosis of celiac sprue? Other helpful methods?
GS: Small bowel biopsy
Other methods: Tissue Transglutaminase IgA and Total IgA (need to test both because a person who is IgA deficient will be a false negative for transglutaminase IgA)
NOTE: If a pt. is adhering to a gluten free diet, all of these tests will normalize
NOTE: ARBs (anti-HTN drug) can cause both the intraepithelial lymphocytosis and villous blunting, so while biopsy is the GS for diagnosis, labs have to be considered
Sometimes, especially in kids, all you will see is intraepithelial lymphocytes and not any villous atrophy. In general, intraepithelal lymphocytes is more indicative of Celiac than villous atrophy
A percentage of pts. with Celiac Disease will also have what disease?
Dermatitis Herpetiformis (clefts packed full of neutrophils)
A MAJOR complication of Celiac disease is T-cell lymphoma
Note that lactose intolerance is usually a diagnosis that can be made *just via history*
How is lactose digested?
•Lactose is hydrolyzed by intestinal lactase to glucose + galactose. These 2 monosaccharides are then absorbed
Lactose not absorbed in the small bowel can be absorbed in the colon. In the colon, lactose converted to short-chain fatty acids + hydrogen gas. The fatty acids are absorbed by the colonic mucosa (The production of hydrogen by colonic bacteria serves as the basis for the lactose breath hydrogen test used to diagnose lactose maldigestion)
History alone can be just fine
How does a lactose tolerance test work?
–Oral administration of 50 grams and Blood glucose levels monitored at 0, 60, 120 minutes (BG should rise!)
–Positive test: Blood glucose increases less than 20 mg/dl + development of symptoms
How does a lactose hydrogen breath test (more common) work?
–Easier to perform and Has largely replaced lactose tolerance test
–Give 25 gram oral lactose
–Breath hydrogen is measured at baseline and at 30 minute intervals for 3 hours
–Hydrogen values over 20 ppm are diagnostic
How is lactose intolerance tx?
–Avoidance of dairy products
–Replacement of lactase
–Supplemental calcium and vitamin D