What is the difference b/t malabsorption and maldigestion?
- MALABSORPTION: impaired absorption of nutrients
- MAL-DIGESTION: impaired digestion of nutrients
- Clinically, this distinction does not matter -> simply refer to malabsorption
What are the 3 steps to normal nutrient absorption?
- Luminal and brush border processing
- Absorption into intestinal mucosa
- Transport into the circulation
What is the difference b/t global and partial malabsorption?
- GLOBAL: reduced mucosal involvement or reduced absorptive surface
1. Not having enough bowel, or defect throughout the bowel
- PARTIAL: interferes with the absorption of specific nutrients
1. B12: need intrinsic factor from stomach (gastrectomy) and terminal ileum (Crohn's)
2. Bile acids: terminal ileum
3. Fe2+, Mg2+, Ca2+, absorbed in duodenum (2+ ions): deficiencies in some bypass surgeries
What are the clinical features of global malabsorption?
- CLASSIC: diarrhea
1. Pale, voluminous, foul-smelling stools
2. Weight loss
- "Classic" symptoms are actually quite uncommon, and the more SUBTLE SYMPTOMS are:
3. Abdominal distention
4. Borborygmi: rumbling, gurgling noise made by movement of fluid or gas in the intestines
5. Iron deficiency or osteopenia
- NOTE: can mimic IBS
What are the 8 categorical causes of malabsorption?
- Gastric disease
- Pancreatic disease
- Liver/biliary disease
- Lymphatic disease
- Intestinal disease
- Neuroendocrine tumors
- Endocrine causes
- Systemic disease
What are some gastric causes of malabsorption?
- Atrophic gastritis
- Auto-immune gastritis: pernicious anemia
- Gastric resection
What are some pancreatic causes of malabsorption?
- Congenital enzyme deficiency
- Pancreatic insufficiency:
1. Chronic pancreatitis
2. Cystic fibrosis
What are some liver and biliary causes of malabsorption?
- Inborn errors of bile transport
- Biliary tumors
- Primary and secondary sclerosing cholangitis (can occur in Crohn's)
What are some lymphatic causes of malabsorption?
- Primary intestinal lymphangiectasia: pathologic dilation of lymph vessels
2. Solid tumors
3. Thoracic duct trauma or obstruction
What are some intestinal causes of malabsorption?
- Celiac sprue, tropical sprue, food allergies
- Graft vs. host disease
- Intestinal infections
- Radiation enteritis
- MANY others
What are some NE tumor causes of malabsorption?
- Carcinoid syndrome
- ZE syndrome: gastrinoma
What are some endocrine causes of malabsorption?
- Addison's disease
What are some systemic causes of malabsorption?
How do you begin to determine the cause of pt's malabsorption?
1. Alcohol use
2. Prior surgeries
3. Relation of symptoms to diet
4. Abdominal pain
5. History of ulcers
What labs should you look at in pt with malabsorption?
- Iron, B12, folate
- Ca, Vit. D
What is the most commonly used indicator of global malabsorption? Tests?
- FAT: most complex process of absorption of the macronutrients, so tends to be most sensitive to interference from disease process
1. Most calorically dense macronutrient, so its malabsorption is a critical factor in the weight loss often seen in malabsorptive disorders
1. Qualitative: Oil red "O"/Sudan stain
2. Quantitative: 72-hr stool fat collection (gold standard, but rarely done in practice)
How does the 72-hr stool fat assessment work?
- QUANTITATIVE: >6g/d of fat is pathologic bc in stool fat excretion in healthy ppl usually <6g/d
- Pts w/steatorrhea usually have >20g daily: modest INC in fecal fat does not diagnose steatorrhea
- GOLD STANDARD, but rarely done in practice (compliance issues; cumbersome and messy)
- NOTE: stool fat remains constant with high fat diets, even >125g of fat daily
What is the qualitative stool fat assessment?
- Oil red "O"/Sudan stain: stain for fat globules from a spot stool sample can detect >90% of pts with steatorrhea
- Sudan stain: fat stains orange (can stain all kinds of colors, according to Dr. Gupta)
- See attached image
Besides fat, what other macronutrient test can be used to assess malabsorption?
- CARBOHYDRATES: can rely on fermentation of undigested carbs by intestinal bacteria, or direct measurement of absorption of specific nutrients
- Examples: lactose tolerance test and several breath tests that measure hydrogen or radioactive isotopes from sugars containing radionuclide carbon analogues
What "other" diagnostic tests (incl. radiologic) can be done for malabsorption (aside from fat, carbs)?
- Upper endoscopy with biopsy
- Colonoscopy with ileal intubation (or biopsy)
- ERCP (endoscopic retrograde cholangio-pancreatography): images of bile & pancreatic duct
- Radiologic studies:
1. CT scan
2. Small bowel follow-through: x-ray that follows passage of barium through stomach and into the small intestine
3. MRCP: magnetic resonance cholangio-pancreatography uses MRI to visualize biliary and pancreatic ducts in non-invasive manner
What might this be?
- CELIAC SPRUE: notice the "scalloping"
- Doesn't make the dx: need to take a biopsy
What is going on here?
- Terminal ileum in normal (left) vs. CROHN's (right)
What might this be?
- CHRONIC PANCREATITIS: this is an ERCP (images taken while patient is on a fluoroscopy table)
- Scope can be seen on B: filling pancreatic duct with dye
- Dilated, strictures, torturous: probably chronic pancreatitis
What do you see here?
- EUS of normal pancreas vs. CHRONIC PANCREATITIS: dilated pancreatic duct, and body of pancreas calcified, much more heterogeneous
- US from inside the digestive tract
- Can biopsy mass through this endoscope too
Name 4 common causes of malabsorption.
- Celiac sprue
- Lactose intolerance
- Bacterial overgrowth
- Chronic pancreatitis
What is celiac sprue? Diagnosis?
- Autoimmune disorder of small bowel due to intolerance of gluten
1. Leads to global malabsorption, but symptoms can be subtle
- DX: tissue transglutaminase IgA
1. Total IgA: if pan-deficient in IgA, will not have TTG IgA (and have 5x risk)
2. Small bowel biopsy -> confirms diagnosis, regardless of the results of these first 2 tests
3. Can be diagnosed with nothing more than iron deficiency anemia
- Good to have dietitian help in tx of these pts
- Susceptible to bone loss
- NOTE: these tests must be done while pt is taking gluten in their diet
What condition do you see here? Describe the characteristic histopathology and dx technique.
- TOP: normal intestinal mucosa
- BOTTOM: celiac disease
- Biopsy specimens from duodenum are generally diagnostic in celiac disease
- Histopathology is characterized by:
1. INC #'s of intraepithelial CD8+ T lymphos (intraepithelial lymphocytosis)
2. Crypt hyperplasia
3. VILLOUS ATROPHY
- Probably takes awhile for the severe appearance on front of card, so INC #’s of CD8+ T-lymphos in tops of villi is what pathologist looks for -> see attached image
What is going on here? HIsto? Associated GI condition?
- Dermatitis herpetiformis: red, itchy, punctate lesions
1. Clefts filled with neutrophils (see attached image of histo)
- Associated with CELIAC DISEASE
What do you see here?
- Enteropathy-associated T-cell lymphoma: sheet of lymphos that eat up crypts/glands
- Associated with CELIAC DISEASE
What is lactose intolerance? Symptoms and epi?
- Intolerance of lactose-containing foods: primarily dairy products
1. Caucasians have abnormal persistence of lactase: only during childhood in most races (tolerance wanes with age)
- SYMPTOMS: bloating, abdominal pain, diarrhea, flatulence after ingestion of dairy products
- EPI: only 7-20% of Caucasians
1. 80-95% of Native Americans
2. 60-75% of Africans
3. Up to 90% in parts of Asia