Malabsorption
د.خلدون العبايجي/المرحلة الرابعةDefective small intestinal digestion and absorption of nutrients which may be selective or multiple.
Categories of causes with examples
1. Luminal phase
Deficiency of pancreatic secretions and bile salts lead to steatorrhea as in:
- Chronic pancreatitis result in malabsorption due to defective secretions of lipase, colipase and trypsin, so fat and proteins are maldigested.
- Deficiency of bile salts leads to fat malabsorption e.g cholestatic liver diseases, bacterial overgrowth which result in bile salt deconjugations
- Ileal disease or resection impair bile absorption.
2. Mucosal phase
It is the most common cause of malabsorption.
Diffuse small intestinal disease e.g celiac disease, crohns disease, surgical resection of small intestine, lactase deficiency, irradiation, infection as in giardiasis, drugs: alcohol, colchicines, neomycin, iron salts.
3. Transport phase
Nutrients leave small intestinal mucosal cells through vascular and lymphatic circulation.
Mesenteric vascular diseases e.g vasculitis, atheroma
Primary lymphagiectasia, lymphatic obstruction by malignancy or irradiation.
Clinical manifestations
- Nonspecific: bloating, fatigue, diarrhea, weight loss, failure to thrive in children.- Protein malabsorption: wasting and edema.
- Carbohydrate malabsorption: abdominal distension, watery diarrhea as in lactase deficiency.
- Fat malabsorption: steatorrhea (bulky oily stool)
- vitamin A malabsorption: xerophthalmia and night blindness
- vitamin D malabsorption: hypocalcemia, rickets and osteomalacia.
- vitamin K malabsorption: bleeding tendency and ecchymoses.
- Iron malabsorption: hypochromic microcytic anemia.
- Folate and vitamin B12 malabsorption: macrocytic anemia and neuropathy.
- B1 malabsorption: neuropathy and heart failure.
- B2 malabsorption: glossitis and angular stomatitis.
- Nicotinic acid malabsorption: Diarrhea, dermatitis, confusion.
- Mg malabsorption: muscle cramps.
Signs associated with malabsorption
Either due signs associated with diseases causing malabsorption or signs resulting from malnutrition secondary to malabsorptuion.
- Abdominal mass: crohns disease, TB, lymphoma.
- Abdominal distension: due to gas and ascites.
- Skin: thin skin, pigmentation, ecchymoses, dermatitis herpetiformis in celiac disease.
- Alopecia: gluten sensitivity.
- Conjunctivitis: in crohns disease.
- Mouth ulcerations: in crohns disease, celiac disease, Behcets syndrome.
- Glossitis: iron, folate, B12 deficiency.
- Raynauds phenomenon: in scleroderma
- Clubbing: in Crohns and lymphoma.
- Koilonychia: in iron deficiency.
- Arthropathy: in Behcets and Whipples diseases.
- Peripheral neuropathy: in B12 deficiency.
- Seizures and cranial nerve palsy: Whipples disease and lymphoma.
Tests of malabsorption
- Blood tests: full blood count to detect type of anemia, ESR, iron status, folic acid,B12,serum albumin, calcium, phosphorus, magnesium, potassium, prothrombin time, blood glucose, cholesterol.
- Fecal fat analysis: sudan stain on stool smear: Estimation of fat quantity in the stool ( give patient 100 gm fat daily for 3 days and collect stool daily, normally fat in stool should not exceed 6 gm/day). 14C-triolein breath test is useful in detection of fat in chronic diarrheas and chronic pancreatitis.
- Radiographic studies: barium follow through show flocculation and segmentation of barium in the small intestine is non-specific. It is helpful also in lymphoma, Crohns disease, stricture, enteric fistula. Plain abdominal X-ray may detect calcification in chronic pancreatitis.
- D-xylose test: assess mucosal integrity. Patient ingests 25 gm of D-xylose, collect urine for next 5 hours. Healthy subjects secrete > 4.5 gm in 5 hours.
- Schilling test: assess B12 absorption as in addisonian pernicious anemia due to intrinsic factor antibodies and atrophic gastritis, bacterial overgrowth and ileal disease in crohns disease. Phase one: inject 1mg of B12 to saturate liver storage, then patient ingests radiolabelled B12, urine is collected for measurement of radioactivity. Phase two: if malabsorption is diagnosed the test is repeated after giving B12 with intrinsic factor. If malabsorption is corrected then pernicious anemia is diagnosed. Phase three: if malabsorption still present give antibiotics, If malabsorption is corrected then bacterial overgrowth is diagnosed, if it is not corrected then ileal disease is diagnosed.
- Pancreatic exocrine function: after pancreatic stimulation duodenal contents are aspirated and analysed for bicarbonate and enzymes. Measure trypsinogen in blood, chymotrypsin or elastase in stool. CT and ERCP for chronic pancreatitis.
- Breath tests: bacterial degradations of luminal compounds causes release of gases that are measured in breath. Disaccharidase test ( lactase deficiency) ingestion of lactose result in colonic fermentation due to malabsorption of lactose in the small intestine and increased hydrogen in breath. In bacterial overgrowth ingestion of glucose result in fermentation and increased hydrogen in breath. Measurement of radioactive C14 in breath: useful in fat and bile malabsorption. 14C-xylose useful in detection of bacterial overgrowth.
- Serology: Useful in celiac disease due to gluten sensitivity in grains ( autoimmune disease, result in diarrhea in children and stunted growth with anemia and bone disease and also affects adults and cause bloating, diarrhea, anemia, osteoporosis and even infertility). Tissue transglutaminase IgA antibodies and anti-endomyseal antibodies are specific for celiac disease, confirmed by duodenal biopsy showing villous atrophy.
- Jejunal fluid aspirate: and anaerobic culture is useful also in diagnosis of bacterial overgrowth ( occur in blind loops after surgery and intestinal strictures in TB and Crohns disease).
- Small intestinal biopsy: may suggest or give a specific diagnosis in celiac disease, Crohns disease, tropical sprue, Whipples disease, amyloidosis, lymphoma, intestinal lymphangiectasia, and giardiasis. ( Giardiasis can be diagnosed also by microscopic stool examination).
Treatment of malabsorption syndrome
- Treat the underlying cause.
- Correct malnutrition and vitamin deficiency.
Celiac disease
Strict life-long adherence to gluten free diet (avoid wheat, barley, and rye).
Correct iron, folate, vitamin D and calcium deficiency.
Bacterial overgrowth
Antibiotics: tetracycline, ciprofloxacin, metronidazole and cephalosporin for variable period of time e.g tetracycline 250 mg 4 times daily for 7 days with vitamin B12.
Tropical sprue
Occur in India and south east Asia, caused by certain types of bacteria and is treated by tetracycline 250 mg 4 times daily for 28 days with folic acid.
Whipples disease
Due to infection with tropheryma whipplei shown as PAS positive foamy macrophages in small intestinal mucosa. Treated by i.v ceftriaxone 2gm/day for two weeks followed by co-trimoxazole for one year.
Intestinal obstruction and strictures
Treatment is surgical.
Crohns disease
Ileal resection, give vitamin B12. Bile acid normally reabsorbed from terminal ileum, so in ileal resection bile acid is not absorbed and pass into colon causing diarrhea which is treated by colestyramine which binds bile acids, aluminium hydroxide can be used as an alternative.
Short bowel syndrome
Nutritional support, vitamins and mineral replacement ( vitamin B12 and folate, vitamin D and calcium, Mg and zinc). Lopermide to stop diarrhea. Octreotide reduces GIT secretions. Some patients need total parenteral nutrition TPN.