MALABSORPTION

MALABSORPTION

Disorders of digestion, and diminished absorption of dietary nutrients are referred as malabsorption syndromes.

ETIOLOGY:

Disorders of intraluminal digestion

A. Pancreatic enzyme deficiency:

 l. Chronic pancreatitis

2. Cystic fibrosis

3. Pancreatic carcinoma

B. Disturbances of gastric function:

 l. Gastroenterostomy

2. Partial gastrectomy

C. Deficiency of bile acids:

l. Crohn’s disease

2. Resection of terminal ileum

3. Stagnant loop syndrome or blind loop syndrome.

Disorders of transport in the intestinal mucosal cell

A. With histologically abnormal mucosa (infiltration, inflammation or infection of mucosa):

l. Coeliac disease

2. Tropical sprue

3. Lymphoma

4. Whipple’s disease

5. Giardiasis

6. Radiation enteritis

B. With histologically normal mucosa (genetic diseases):

l. Lactase deficiency

2. Pernicious anaemia

C. Disorders of transport from mucosal cell:

l. Abdominal lymphoma

2. Tuberculosis

3. Telangiectasia of mesenteric lymphatics

4.  Abetalipoproteinaemia

D. Impaired nutrient uptake:

l. Lymphatic obstruction

2. CHF, pericarditis

E. Miscellaneous:

l. Diabetes mellitus

2. Hyperthyroidism

3. Hypoparathyroidism

CLINICAL FEATURES:

The onset of malabsorption syndrome is insidious and progression is gradual.

General features

Diarrhoea, abdominal pain, distension, loss of weight,

anaemia and vague ill health.

Specific features

Specific features due to defective absorption of different constituents are as follows:

  i. Carbohydrates: Abdominal distension, belching, bloated feeling in abdomen.

 ii. Protein: Progressive emaciation, pitting pedal oedema.

 iii. Fat: Loss of weight, diarrhoea, and loose, pale, bulky offensive stool which floats on water, i.e. steatorrhoea.

 iv. Vitamins:

 a. Vitamin A: Follicular keratosis, night blindness, xerophthalmia, keratomalacia.

 b. Vitamin D: Muscular irritability, tetany, features of osteomalacia.

  c. Vitamin K: Haemorrhagic tendencies.

 d. Vitamin Bl and B2: Angular stomatitis, cheilosis,

glossitis, neuropathy.

  e. Folic acid: Macrocytic anaemia, glossitis.

  v. Minerals and electrolytes:

 a. Sodium: Muscle cramps, weakness, hypotension.

 b. Potassium: Weakness, areflexia, intestinal distension, cardiac arrhythmias.

 c. Calcium: Muscular irritability, tetany, features of rickets, features of osteomalacia.

 d. Magnesium: Weakness, tingling sensation, tetany.

 e. Zinc: Anorexia, weakness, tingling, impaired taste.

 f. Iron: Hypochromic microcytic anaemia, glossitis, koilonychia.

 g. Water: Dehydration, low blood volume.

INVESTIGATION:

Routine laboratory studies

Tests are performed to detect any nutrient deficiency. These tests reveal malabsorption of particular nutrient but do not establish the cause.

Specific Tests

i. Faecal fat estimation:

l. This is a reliable test to confirm steatorrhoea and fat malabsorption.

2. Sudan III stain may show an increase in the stool fat.

3. Quantitative estimation of fat in the stool is more reliable and sensitive.

4. A 72-hour stool collection while the patient is on a defined diet is used for fat estimation. Excretion of more than 10 g fat per day suggests fat malabsorption.

ii. Schilling test:

l. This is useful in the diagnosis of cobalamin (B12) malabsorption and its causes like pernicious anaemia, chronic pancreatitis, achlorhydria and bacterial overgrowth.

2. Schilling test: Radio-labelled cobalamin (1mg 58Co) is given orally and its excretion in urine is measured. One mg cobalamin is administered intramuscularly to saturate hepatic binding sites so that all radiolabelled cobalamin is excreted in the urine. The test is abnormal, if less than 10 % of the radio-labelled cobalamin is excreted in the urine in 24 hours. If the test is abnormal, it is repeated by giving radio-labelled cobalamin in combination with intrinsic factor or pancreatic enzymes. It may also be repeated after a 5-day course of antibiotics. This will help in differentiating the various defects responsible for malabsorption of cobalamin.

iii. D-xylose test:

It is performed to detect carbohydrate malabsorption. 25 g D-xylose is given orally and its excretion is measured in urine. Excretion of less than 4.5 g in 5 h is indicative of malabsorption.

iv. Upper GI endoscopy and biopsy of small intestinal mucosa:

It is essential for the diagnosis of conditions like tropical sprue, celiac sprue, Whipple’s disease, and Crohn’s disease.

v. Barium meal contrast radiography:

Radiological assessment of the small intestine with barium contrast is helpful in evaluation of structural abnormalities in Crohn’s disease, diverticulam and strictures.

vi. Pancreatic exocrine functions:

They are assessed in patients with steatorrhoea.

vii. Serological studies:

Autoantibodies are detected in some conditions such as celiac sprue and pernicious anaemia.

viii. Breath tests:

l. Cholyl-14C-glycine for bacterial overgrowth

2. Lactose H2 for bacterial overgrowth

ix. Small intestinal biopsy (duodenal or jejunal):

TREATMENT:

l. Deficient nutrients are replaced.

2. Gluten-free diet in coeliac disease.

3. Pancreatic supplements in pancreatic insufficiency.

4. Low fat diet and cholestyramine for bile acid deficiency.

5. Replacement therapy for anaemia, bone disease and coagulation defects.

6. Oral folic acid, oral iron and intramuscular B12

7. Vitamin D and calcium supplements.

8. Vitamin B complex

9. Treat dehydration and electrolyte deficiency by intravenous infusion.