Introduction
What is digestion and what is absorption?
Digestion means hydrolysis of nutrients. Absorption means uptake of nutrients from the gastrointestinal tract to the systemic circulation.
What is maldigestion and what is malabsorption?
Maldigestion denotes impaired nutrient hydrolysis. Malabsorption refers to defective mucosal absorption of nutrients. However, the two entities are so closely linked that in clinical practice malabsorption serves as a global term for all aspects of their impairment. Malabsorption may occur for many nutrients or for specific carbohydrates, fats, or micronutrients.
What steps are involved in digestion and absorption?
Three phases are involved:
Luminal phase - Dietary fats, proteins, and carbohydrates are hydrolyzed and solubilized, largely by pancreatic and biliary secretions.
Mucosal phase - Terminal hydrolysis of carbohydrate and peptides occurs and fats are processed and; then packaged for cellular export.
Removal phase - Absorbed nutrients enter the vascular or lymphatic circulation.
Thus defect in any of these phases leads to malabsorption.
What are the Causes of Malabsorption in Children?
Inadequate digestion
- Postgastrectomy
- Deficiency or inactivation of pancreatic lipase
- Exocrine pancreatic insufficiency
- Chronic pancreatitis
- Cystic fibrosis
- Pancreatic insufficiency - congenital or acquired
- Gastrinoma - acid inactivation of lipase
- Lactose intolerance
Reduced intraduodenal bile acid concentration/impaired micelle formation
Liver disease
- Parenchymal liver disease
- Cholestatic liver disease
Bacterial overgrowth syndrome
- Anatomic or functional stasis
- Interrupted enterohepatic circulation of bile salts
- Ileal resection
- Crohn's disease
Drugs (bind or precipitate bile salts) : calcium carbonate, neomycin, cholestyramine
Impaired mucosa absorption/mucosa loss or defect
Intestinal resection or bypass
- Inflammation, infiltration, or infection
- Celiac disease
- Crohn's disease
- Tropical sprue
- Amyloidosis
- Scleroderma
- Lymphoma
- Immuno proliferative small intestinal disease (IPSID)
- Eosinophilic enteritis
- Whipple's disease
- Folate and Vitamin B12 deficiency
- Infection: Giardiasis, Strongyloidiasis, Tuberculosis
- Graft vs. host disease
Genetic disorders
- Disaccharidase deficiency
- Agammaglobulinemia
- Abetalipoproteinemia
- Hartnup disease
- Cystinuria
Impaired nutrient delivery to and/or from intestine
Lymphatic obstruction
- Lymphoma
- Lymphangiectasia
Circulatory disorders
- Constrictive pericarditis
- Vasculitis
- Congestive heart failure
Endocrine and metabolic disorders
- Hyperthyroidism
- Adrenal insufficiency
- Diabetes mellitus
- Hypoparathyroidism
- Carcinoid syndrome
Most Frequent Causes of Malabsorption In Children In India
- Infections: Giardiasis, Strongyloidiasis, Tuberculosis
- Celiac sprue (Gluten sensitivity)
- Lactose intolerance
- Tropical sprue
- Chronic pancreatitis
- Lymphoma, Immunoproliferative small intestinal disease (IPSID)
Does an Acute Gastrointestinal Infection Lead to Malabsorption?
Yes. Acute viral or bacterial gastrointestinal infection can give rise to transient malabsorption, most probably due to damage to small intestinal villi and microvilli.
Where are Specific Food Items Absorbed Along the Gastrointestinal Tract?
| Food Item |
Site of maximal absorption |
Proteins
|
Jejunum and Ileum |
| Carbohydrates | Jejunum and Ileum |
| Lipids | Jejunum and Ileum |
Iron
| Duodenum and Jejunum |
Calcium
| Jejunum and Ileum |
Zinc
| Duodenum and Jejunum |
Magnesium
| Small intestine |
| Vitamin A | Small intestine |
Vitamin B12
| Ileum |
Folic acid
|
Jejunum |
| Vitamin C |
Jejunum and Ileum |
| Vitamin D |
Jejunum |
| Vitamin E |
Jejunum and Ileum |
| Vitamin K |
Jejunum and Ileum |
| Water |
Jejunum, Ileum, Colon |
When Does One Suspect That a Child has Malabsorption Syndrome?
Progressive weight loss
Failure to thrive
Chronic diarrhea
Steatorrhea
Edema feet
Weakness, Malaise, Fatigue
Abdominal distension
Borborygmi, Excessive flatus
Abdominal pain
Symptoms reflecting specific deficiencies, such as bleeding tendency, muscle cramps, tetany, bone pains and paresthesias
Symptoms related to cause of malabsorption
What Is Steatorrhea?
Steatorrhea is pale, soft, bulky, malodorous stools that stick to the side of the toilet bowl or float and are difficult to flush away. Steatorrhea indicates an excess amount of malabsorbed fat in stools.
What are the Signs in a Child with Malabsorption Syndrome?
| Gastrointestinal | |
| Mass | Tuberculosis,lymphoma, Crohn's disease |
| Distension | Ascites (hypoproteinemia,tuberculosis), pancreatic pseudocyst |
Steatorrheicstool
| Pancreatic insufficiency, small intestinal mucosa disease |
| | |
| Extra intestinal | |
| Skin | |
| Nonspecific | Pigmentation, thinning, inelasticity, reduced subcutaneous fat |
| Specific | Petechiae
(Vitamin K deficiency), edema (hypoproteinemia), erythema nodosum
(Crohn's disease), dermatitis herpetiformis (celiac sprue) |
| | |
| Hair | |
| Alopecia, thinning | Gluten sensitivity, generalized inanition |
| | |
| Eyes | |
| Conjunctivitis, episcleritis | Crohn's disease |
| Paleness | Severeanemia
|
| | |
| Mouth | |
| Aphthous ulcers | Gluten sensitivity, Crohn's disease |
| Glossitis | Deficiencies ofvitamin B12,iron,folic acidand niacin |
| Angular cheilosis | Deficiencies of vitamin B12, iron, folic acid and vitamin B complex |
| Dental hypoplasia | Gluten sensitivity |
| | |
| Hands | |
| Clubbing | Gluten sensitivity, Crohn's disease, tuberculosis, lymphoma |
| Koilonychia | Iron deficiency
|
| | |
| Musculoskeletal | |
| Mono/polyarthropathy | Gluten sensitivity, Crohn's disease, Whipple's disease |
| Back pain | Gluten sensitivity, Crohn's disease |
| Muscle weakness | Diffuse mucosal disease, lymphoma |
| | |
| Nervous system | |
| Peripheral neuropathy | Vitamin B 12 deficiency |
| Cerebral (seizures, dementia, cranial nerve palsies) | Whipple's disease, gluten sensitivity, diffuse lymphoma |
Why Does Milk And Milk Products Aggravate Diarrhea In Patients With Malabsorption Syndrome?
This occurs since small intestinal mucosal diseases cause secondary lactase deficiency. Lactase is necessary for the digestion of lactose, the disaccharide present in milk.
How to You Initially Investigate Patients with Malabsorption Syndrome?
| Blood tests |
Abnormal result |
Complete hemogram,
Mean corpuscular volume | Anemia Microcytic-Iron deficiency
Macrocytic-Vitamin B12, folic acid deficiency |
| Peripheral smear | Hypersegmentation of polymorphic nuclei-Vitamin B12, folic acid deficiency.
Howell Jolly bodies-Gluten sensitivity, Crohn's disease
Acanthocytes-Abetalipoproteinemia |
| ESR, C-reactive protein | Tuberculosis, Crohn's disease, lymphoma, IPSID, vasculitis
|
| Prothrombin time | Vitamin K malabsorption
|
| Serum albumin | Protein loss through gut or amino acid malabsorption |
| Serum calcium | Vitamin D and calcium malabsorption |
| Serum phosphate | Vitamin D malabsorption |
| Serum alkaline phosphatase | Vitamin D malabsorption |
| Serum cholesterol | Lipid malabsorption |
Serum potassium
| Increase loss due to excessive diarrhea
|
| Serum iron, serum ferritin | Iron deficiency |
| Serum folate, red cell folate | Folic acid deficiency |
| Serum zinc | Zinc deficiency |
| Serum magnesium | Magnesium deficiency |
| Serum vitamin B12 | Vitamin B12 deficiency |
| Stool-Routine/Microscopy | Steatorrhoea, Giardia lamblia, Neutrophils in inflammatory disease |
| X Ray Abdomen * | Calcification (Chronic pancreatitis) |
| HIV (ELISA) * | Human immunodeficiency virus |
| Thyroid function tests * | Hyperthyroidism |
| Immunoglobulin A * | Low immunoglobulin levels |
| Specific antibodies * | Antigliadin (IgA)/Antiendomysial (IgA)-Gluten sensitivity |
| Sweat chloride * | Cystic fibrosis |
* Only if clinically suspected
What are the Specific Tests to Evaluate Malabsorption Syndrome?
| Test | Utility |
| Schilling test | To evaluate cause of vitamin B12 deficiency |
| Fecal fat estimation | Chronic pancreatitis, Small intestinal mucosa disease |
| Xylose tolerance test | Small intestinal mucosa disease |
| Small intestinal barium study | Small intestinal mucosa disease |
Endoscopy with small intestinal biopsy
| Small intestinal mucosa disease |
| US abdomen, CT scan abdomen | Chronic pancreatitis, Tuberculosis |
| ERCP | Chronic pancreatitis |
| Tests to evaluate pancreatic exocrine function (Tube and tubeless tests) | Chronic pancreatitis |
| Breath tests | Bacterial overgrowth syndrome, Lactase deficiency |
What are the Basic Principles of Management of Patients with Malabsorption?
Management depends on cause of malabsorption and severity of malabsorption. However, broad guidelines to be followed are:
Nutritional support:
- Anemia: Hematinic supplements (Iron, Vitamin B12, Folic Acid)
- Specific deficiencies of vitamins, minerals and trace elements - Oral supplementation (Fat soluble vitamins, calcium, magnesium, zinc, etc.)
- Temporary lactose restriction for patients with secondary lactase deficiency
- High-protein, low-fat diet
- Medium-chain triglycerides preferred as fat substitutes
- Avoid food items, which aggravate symptoms Symptomatic treatment:
- Diarrhea: Loperamide or Diphenoxylate
- Cholestyramine (in patients with limited ileal disease)
Treatment of underlying disease:
Specific therapy for underlying disease is of utmost importance.
- Celiac sprue: Avoid wheat, barley, rye and oats in diet.
- Bacterial overgrowth syndrome: Antibiotics.
- Giardiasis: Metronidazole, Tinidazole, Albendazole
- Strongyloidiasis: Thiabendazole, Albendazole, Mebendazole, Ivermectin
- Tuberculosis: Anti tuberculosis therapy
- Crohn's disease: Aminosalicylates, Corticosteroids
- Tropical sprue: Antibiotics, Folic acid
- Chronic pancreatitis: Pancreatic enzymes
What is the Prognosis of a Patient Having Malabsorption?
Once the diagnosis of malabsorption has been made, prognosis primarily depends on the cause of malabsorption. However, once the cause is found, the prognosis is reasonably good in most cases, if medical and diet therapy is rigorously followed. Infectious causes if treated adequately have excellent.
How Long is Therapy Necessary?
It is important to remember that most causes of malabsorption, except infections require continuous supervision by a doctor and necessitate prolonged therapy.