Definition: It is the general name of the clinical picture characterized by malabsorption or insufficient absorption in the digestive system.
Clinic
• Malabsorption classically progresses with diarrhea, weight loss and malnutrition.
• Other special symptoms/signs seen in malabsorption and associated conditions given in the table:
Malabsorption symptoms/signs and associated conditions
Symptom/sign ------------------Etiology
• Steatorrhea -------------------- Fat malabsorption
• Diarrhea ----------------------- Absorption disorder
• Gas, bloating------------------ Carbohydrate malabsorption
• Weight loss, muscle atrophy----------- Absorption disorder, calorie deficiency
• Edema ------------------------- Protein malabsorption
• Anemia---------------------- Iron, folate, Vitamin B12 malabsorption
• Bleeding diathesis ---------------------------- Vit K deficiency
• Osteomalacia, paresthesia, tetany --------- Vit D and calcium deficiency
• Night blindness ------------------------------ Vitamin A deficiency
• Dermatitis ---------------- Zinc and other trace element deficiency
• Stomatitis, glossitis ----------- Vitamin B, C, folate, B12 deficiency
Diagnosis
• The blood levels of any substance whose absorption is impaired may be found to be decreased and these can be used for diagnostic purposes. Hypocalcemia, hypoalbuminemia; Calcium, phosphorus, magnesium and zinc deficiency, prolongation of PTZ, microcytic anemia (iron deficiency), macrocytic anemia (folate and B12 deficiency) can be detected.
• Serum carotene measurement and qualitative fat determination in stool can be used as a screening test in the presence of malabsorption. These are sensitive, but not specific.
Measurement of serum carotene level: Carotene is absorbed from the epithelial cells of the small intestine. This test reflects the integrity of the small intestinal mucosa. Usually normal, small intestinal mucosa in pancreatic disorders! diseases are expected.
Qualitative fat determination: The most practical test for fat malabsorption, but
it is subjective. The stool sample is spread on a slide, stained with Sudan III, examined under a microscope, and oil droplets are evaluated.
Quantitative fat absorption test: Three days of stool are collected from patients under normal diet. The average amount of fecal fat should not be more than 7 gr/day. (> 7g/day = steatorrhea). It is the best test to show fat malabsorption.
- D-Xylose test
Normally, after 25 g of D-Xylose is taken orally, the D-Xylose level in the urine for 5 hours should be more than 5 g.
This test reflects the integrity of the small intestinal mucosa. It is expected to be normal in pancreatic disorders, and abnormal in small intestinal mucosal diseases.
- Bentiromide test
It is the easiest and most specific test for the diagnosis of pancreatic insufficiency.
Benthyromid is a combination of PABA (para amino benzoic acid) and synthetic peptide.
The bond is broken only by pancreatic chymotrypsin.
For the test, the patient is given oral bentiromide and then urine PABA levels are measured.
A low level of PABA in the urine suggests exocrine pancreatic insufficiency.
- Secretin test
It is the most sensitive but complicated test to evaluate pancreatic exocrine functions.
Secretin-stimulated pancreatic secretion is collected and analyzed by a duodenal tube.
- Schilling test
In the first step, the patient is given oral radiolabeled cyanocobalamin and 24-hour urine is collected. If this substance is low in the urine, the test is defective (Bl2 absorption is impaired). Other stages of testing are done to find the cause:
If the test improves with the administration of intrinsic factor, the diagnosis is pernicious anemia.
There is chronic pancreatitis if it gets better when pancreatic extract is given, and if it gets better with antibiotic treatment, there is excessive bacterial growth.
If the cause of B12 deficiency is ileal disease, the test will not improve in any way.
In vegetarians and achlorhydria, the test is normal in the first stage.
- H2 breathing test
Carbohydrate malabsorption (especially lactose intolerance) is evaluated.
It is based on the detection of lactose, which passes into the colon in the absence of lactase enzyme and ferments there, causing the formation of excess hydrogen.
Excess hydrogen gas in the breathing air indicates lactose intolerance.
- C14- Xylose respiration test: It is used for the diagnosis of excessive bacterial growth.
• Fecal alpha-1 antitrypsin clearance and chymotrypsin: They are used to evaluate protein loss.
• Imaging methods
Barium radiography of the small intestine: It shows anatomical disorders (fistula, stenosis, dilatation, blind loop, etc.).
CT or MR enterography: It better determines the morphology of the small intestine.
Capsule endoscopy and double-balloon enteroscopy: Provides direct visualization of lesions, biopsy can also be taken with enteroscopy.
• Small intestine biopsy
It is the most important method in the evaluation of a patient with steatorrhea or chronic diarrhea.
There are 4 conditions related to the extent of disease involvement in malabsorptions and the diagnostic ability of biopsy:
Diffuse involvement, specific histology (biopsy is always diagnostic)
- Abetalipoproteinemia, Agamaglobulinemia, Whipple's disease
Segmentary involvement, specific histology (biopsy is diagnostic only if taken from the involved intestinal segment)
- Crohn's disease, lymphoma, lymphangiectasia, eosinophilic gastroenteritis, amyloidosis, mastocytosis
Diffuse involvement, non-specific histology (biopsy is abnormal but does not make a specific diagnosis)
- Gluten sensitive enteropathy, tropical sprue, infectious enteritis, radiation enteritis, bacterial overgrowth
Cases where a biopsy is normal
- Functional bowel disease, liver disease, pancreatic insufficiency, disaccharidase deficiency, ulcerative colitis
