Malabsorption and small bowel disease Flashcards
What is the clinical definition of malabsorption?
Impaired nutrient absorption due to defects in the absorptive epithelium of the small intestine or improper digestion of nutrients.
What are the clinical features of malabsorption?
Diarrhea with fatty, large-volume, foul-smelling stools (steatorrhea), weight loss, and vitamin/mineral deficiencies (e.g., iron, calcium, fat-soluble vitamins).
What are the major etiologies of malabsorption?
Celiac disease, pancreatic insufficiency, lactose intolerance, Whipple disease, Tropical sprue, Small intestinal bacterial overgrowth (SIBO).
How is malabsorption diagnosed?
Fecal fat analysis (e.g., Sudan III stain), hydrogen breath test for carbohydrate malabsorption, and D-xylose absorption test.
What is celiac disease?
An autoimmune hypersensitivity to gluten, resulting in small bowel mucosal inflammation and villous atrophy.
What are the clinical features of celiac disease?
Malabsorption symptoms (diarrhea, weight loss, iron deficiency anemia) and dermatitis herpetiformis. Patients will be deplete in fat soluble vitamins, such as A, D, E, and K.
How would celiac disease present with a child?
anemia from iron loss and bowed legs (genu varum) from vitamin D loss.
Note under normal circumstances, Genu Varum self corrects by 2 to 3 years, so this might convolute presentation, diagnosis, and management.
How is celiac disease diagnosed?
Serology (tTG-IgA, deamidated gliadin peptide IgG) is used to screen and endoscopy with biopsy (villous atrophy, crypt hyperplasia, intraepithelial lymphocytosis) is used to confirm.
- tTG (Tissue Transglutaminase Antibody) is the preferred autoantibody to screen as it has high sensitivity and specificity (>90%). This autoantibody is against the enzyme tissue transglutaminase, which modifies gluten peptides in the small intestine. Primarily IgA (tTG-IgA), is used although IgG (tTG-IgG) is used in individuals with IgA deficiency. tTG can also be used to as a surrogate to assess the degree of intestinal damage and can be used to monitor adherence to a gluten-free diet.
- DGP (Deamidated Gliadin Peptide Antibody) is an autoantibody against deamidated gliadin peptides, which are gluten-derived peptides modified by tTG. IgA (DGP-IgA) would be preferred, but is unreliable in IgA deficiency, in which case IgG (DGP-IgG) is used. DGP is a second-line screening tool as the sensitivity and specificity are slightly lower than tTG-IgA but still reliable for screening, the major limitation is that DGP is prone to false positives compared to tTG-IgA.
- EMA (Anti-Endomysial Antibody) is an autoantibody against endomysium, the connective tissue layer surrounding muscle fibers. The primarily autoantibody is IgA (EMA-IgA). There is no IgG anti-endomysial antibody (EMA) test. EMA is highly specific for celiac disease (>99% specificity), making it useful for confirmatory testing, however, typically EMA is ordered as a secondary test if tTG or DGP results are equivocal. EMA requires indirect immunofluorescence microscopy, making it more expensive and labor-intensive and can be unreliable in IgA deficiency.
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Screening for Celiac Disease
tTG-IgA: The preferred screening test due to its high sensitivity and specificity.
Total IgA levels: Always measured alongside tTG-IgA to identify IgA deficiency.
If IgA deficiency is detected, switch to: tTG-IgG or DGP-IgG for screening.
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Confirmatory Diagnosis
While serologic tests are excellent for screening, celiac disease must be confirmed with endoscopy with small bowel biopsy (gold standard for diagnosis). Patients must consume gluten prior to testing (ideally 6–8 weeks) to avoid false-negative results. Findings include villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytosis. Biopsy is typically avoided in young children if both clinical symptoms and serologic tests (e.g., tTG-IgA and EMA-IgA) are unequivocally positive.
What hematological test has shown to be a credible risk factor for celiac disease?
HLA-DQ2/DQ8.
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This has a high negative predictive value.
What immunological deficiency should patients be screened for when attempting to diagnose for celiac disease?
Selective IgA deficiency. If this is low, check tTG IgG or DGP IgG.
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Selective IgA deficiency is associated with Giardia infection (giardiasis).
What is the treatment for celiac disease?
Gluten-free diet with vitamin and mineral supplementation (e.g., iron, calcium, folate).
Celiac increases the risk for … ?
T cell lymphoma, Type 1 DM, and Hashimoto’s thyroiditis.
What is the skin finding associated with celiac disease?
Dermatitis herpetiformis. This is an erythematous rash with vessilces. Patients can be given Dapsone, but this should be avoided with G6PD deficiency.
What causes pancreatic insufficiency?
Chronic pancreatitis, advanced hemochromatosis, cystic fibrosis, obstructive conditions, or small bowel resections reducing cholecystokinin (CCK) production.
What are the clinical features of pancreatic insufficiency?
Steatorrhea, weight loss, and malabsorption.
How is Whipple disease treated?
Penicillin or ceftriaxone initially, followed by TMP-SMX (Bactrim) for one year, Bactrim is given for longer if the infection has reached the CNS.
