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
How does lactose digestion work?
- Lactose hydrolyzed by intestinal lactase to glu + galactose, and these 2 monosaccharides are then absorbed by intestinal mucosa
1. Lactose not absorbed in the small bowel can be absorbed in the colon
- In colon, lactose converted to short-chain fatty acids (SCFA's) + hydrogen gas -> the fatty acids are absorbed by the colonic mucosa
1. Production of hydrogen by colonic bacteria basis of the lactose breath hydrogen test used to diagnose lactose maldigestion
How is lactose intolerance diagnosed?
- History: this alone can be just fine to dx
- Lactose tolerance test
- Lactose hydrogen breath test
How does the lactose tolerance test work?
- Oral admin of 50g lactose, and blood glu levels monitored at 0, 60, and 120 minutes
- Positive test = blood glu INC <20mg/dL + devo of symptoms
- NOTE: this test is "not done"
How does the lactose hydrogen breath test work?
- Easy to perform, so it has largerly replaced the lactose tolerance test
- Give 25g oral lactose -> breath hydrogen measured at baseline and 30-min intervals for 3 hrs
1. Hydrogen values >20 ppm are diagnostic
- NOTE: you can even order these tests over the internet and have them mailed to your home (see attached image)
What is the tx for lactose intolerance?
- Avoidance of dairy products
- Replacement of lactase
- Supplemental Ca and Vit. D
What is small bowel bacterial overgrowth (SBBO)? Associations?
- Condition in which non-native and/or native bacteria are present in INC #'s
1. Results in excessive fermentation, inflam, or malabsorption
2. Small bowel is relatively sterile: ileocecal valve, motility, pylorus keep bacterial growth here to a minimum
- Associated with:
1. Anatomic abnormalities: surgical loops (blind loops of bowel), strictures
2. Abnormal small bowel motility: DM, scleroderma, radiation enteritis
3. Abnormal communication in small bowel: fistulas, don’t have ileocecal valve, pylorus
4. Others: chronic pancreatitis, cirrhosis, ESRD, TPN use in children
How is SBBO diagnosed?
- Suspected by history
- Can give empiric trial of antibiotics: improvement can last months
- Carbohydrate breath tests: can use lactulose, glucose, D-xylose (2 peaks = (+) result)
1. (+) results will see early peak from hydrogen production in small bowel, then later peak from hydrogen production in colon -> normal result is peak only after 2-3 hours in colon
How is SBBO treated?
- Trial of antibiotics: can treat with 7-10 day course with lasting results
1. Rifaxamin is a non-absorbed, expensive AB: few side effects, and low risk of resistance
- Treat underlying disorder:
1. Motility agents
2. Surgical correction
What is chronic pancreatitis? Symptoms?
- Condition of progressive inflammatory changes leading to structural damage
- Contrasts with acute pancreatitis: recurrent bouts of acute can progress to chronic
- SYMPTOMS: abdominal pain
1. Pancreatic insufficiency: does not occur until 90% of pancreatic function is lost -> fat malabsorption, diabetes
How is chronic pancreatitis diagnosed?
- HISTORY: chronic alcohol abuse
- FECAL ELASTASE: most sensitive and specific, esp. in early phases of pancreatic insufficiency
1. <200mcg/g suggestive of pancreatic insufficiency
2. Independent of pancreatic enzyme replacement tx, and require only single random stool sample
- IMAGING studies: CT, MRI, MRCP, EUS
How is chronic pancreatitis treated?
- Cessation of alcohol intake: hardest part
- Pain management
- Enzyme replacement: pill forms
- Surgical procedures: to relieve blocked pancreatic duct (not very common)
What is Whipple disease? Dx? Histo? Tx?
- Rare, multivisceral chronic disease presenting with malabsorption, lymphadenopathy, and arthritis
1. Middle-aged pts with weight loss, diarrhea, pain, and arthropathy -> when you see this, think Whipple
2. Test of choice is biopsy of small bowel
- HISTO: foamy macros and large #'s of argyrophilic rods in lymph nodes
1. G(+) actinomycete (Tropheryma whippelii)
- TX: prolonged course of AB’s (1-2 years of tx)
What is going on here? Pathogenesis? Stain?
- Dense accumulation of distended, foamy macros in small intestinal lamina propria -> Whipple's
- Clinical symptoms bc organism-laden macros accumulate in small intestinal lamina propria and mesenteric lymph nodes, causing lymphatic obstruction
1. Malabsorptive diarrhea due to impaired lymphatic transport
- PAS positive and diastase resistant (see attached image)
What is this?
What is going on here?
- Intestinal TB: foamy macros and PAS-positive organism -> similar appearance to Whipple's
1. Acid-fast stain can be helpful bc mycobacteria stain (+), but T. whippelii do not
- NOTE: mycobacterium avium complex (MAC) consists of two species -> M. avium and M. intracellulare
Which of the following is only absorbed in the terminal ileum?
C. Bile salts
B. B12 and C. Bile salts
Which of the following is the best test to screen for celiac sprue?
A. Lactose hydrogen breath test
B. SBFT: a fluoroscopic technique designed to obtain high resolution images of the small bowel
C. Tissue Transglutaminase IgA
C. Tissue Transglutaminase IgA (if +, then small bowel biopsy)
Which of the following does NOT predispose to SBBO?
B. Pulmonary HTN
D. Prior bowel surgeries
B. Pulmonary HTN
- NOTE: diarrhea may be fairly common in diabetes due to meds (Metformin), overgrowth, etc.
What is tropical sprue (at a very basic level)?
- Like Celiac disease, but presents with patient who spent more than a few months in the tropics
- May develop several years later