Malabsorption gastro-intestinale

What is gastrointestinal malabsorption?

Gastrointestinal malabsorption is a failure to fully absorb nutrients from the gastrointestinal tract. The digestion and absorption of nutrients within the gastrointestinal tract requires a complex interaction between motor, secretory, digestive and absorptive processes that are vulnerable to various potential disturbances which may lead to global or specific malabsorption syndromes.¹

The outcome is malnutrition. Malnutrition may also be caused by inadequate diet with or without malabsorption. See also the separate Malnutrition article.

Malabsorption, from whatever cause, may be accompanied by:

• Changements de poids et de croissance :
  

  • Inadequate absorption of calories will lead to unintentional weight loss in adults or faltering growth in children.

• Symptômes gastro-intestinaux :
  

  • Chronic diarrhoea is common. Chronic diarrhoea may be defined as the abnormal passage of three or more loose or liquid stools per day for more than four weeks and/or a daily stool weight greater than 200 g/day.

  • Steatorrhoea is often present. There is excessive fat in the stools and they become pale, bulky and offensive in smell. Stools float and are difficult to flush away. They often leave a greasy rim around the pan.

• Antécédents familiaux :
  

  • Some diseases associated with malabsorption are found more frequently in families - eg, la maladie cœliaque, maladie de Crohn, la fibrose kystique et disaccharidase deficiencies (lactase). It is therefore important to explore the family history carefully.

• Des signes de carences peuvent être apparents. Il peut y avoir :
  

  • Non-anaemic iron deficiency.

  • Anémie ferriprive.

  • Carence en folates ou carence en vitamine B12.

  • Bleeding, resulting from low vitamin K.

  • Œdème, which occurs in protein/calorie malnutrition.

There may also be clinical features associated with the particular cause of malabsorption. The most common causes in the UK are maladie cœliaque, maladie de Crohn et chronic pancreatitis.

However the malabsorption of simple carbohydrates is the most common type of non-immune-mediated food intolerance, affecting 20-30% of the European population⁴ .

Mucosal causes

• Maladie cœliaque usually presents in childhood but can present later.

• Intolérance au lactose.

• Allergie aux protéines de lait de vache.

• Soya milk intolerance.

• Fructose intolerance and malabsorption: simultaneous consumption of glucose reduces fructose malabsorption⁶ .

• Infection :
  

  • Giardiase.

  • Maladie de Whipple.

  • Intestinal tuberculosis.

  • Sprue tropicale.

  • Diarrhée du voyageur.

  • Diphyllobothriasis (tapeworm can cause vitamin B12 malabsorption).

  • Ancylostomiasis (hookworm).

  • Strongyloïdose (nematode).

• In patients with an inflammatory bowel disorder and malabsorption, an immune deficiency, y compris HIV enteropathy, should be considered.^{7 8}

• Intestinal lymphangiectasia and other causes of lymphatic obstruction include lymphoma, la tuberculose and cardiac disease.

Intraluminal causes

• Pancreatic insufficiency:⁹
  

  • Mucoviscidose

  • Pancréatite chronique

  • Carcinoma of pancreas

  • Syndrome de Zollinger-Ellison

• Bile acid malabsorption: defective secretions of bile salts, due to cholestatic jaundice or disease of the terminal ileum.

• Small intestinal bacterial overgrowth (SIBO).¹⁰

Structural causes

• Urgence intestinale :
  

  • Post-gastrectomy

  • Post-vagotomy

  • Gastrojejunostomy

• Le blind loop syndrome involves disturbance of normal gut flora with malabsorption.

• Fistulae.

• Diverticulae and strictures.

• Maladie de Crohn.

• Amylodose.

• Short bowel syndrome.

• Eosinophilic gastroenteropathy.

• Mesenteric arterial insufficiency.

• Radiation enteritis.

Causes outside the gut

• Hyperthyroïdie.

• Hypothyroïdie.

• Maladie d'Addison.

• Diabète sucré.

• Hyperparathyroïdie.

• Hypoparathyroïdie.

• Carcinoid syndrome.

• Widespread skin disease (rapid cell turnover may also affect gut mucosa).

• Collagen diseases.

• Eating disorders.

• Factitious diarrhoea due to purgative abuse.

Analyses de sang

• Hémogramme complet.

• Plasma viscosity, ESR, CRP.

• Vitamin B12 level.

• Red cell folate.

• Iron status (usually ferritin but can be iron and iron-binding capacity).

• Clotting screen for vitamin K deficiency.

• Serum albumin.

• Calcium (corrected for albumin level).

• Magnesium, zinc, phosphorous.

• Vitamine D.

• Anti-endomysial, anti-reticulin and alpha-gliadin antibodies (coeliac screen).

• Bilan hépatique.

Stool

• Faecal microbiological assessments may be indicated.

• Sudan stain for fat globules.

• Tests for secretory function - eg, elastase or chymotrypsin in stool.

Imaging and endoscopy

• Abdominal ultrasound (gallbladder, liver, pancreas, intestinal wall, adenopathy).

• Barium follow-through may show structural abnormalities.

• Jejunal biopsy (and aspirate for possibility of SIBO).

• Ileocolonoscopy including biopsies of colon and ileum.

• CT; MRI of pancreatic duct-systems or endoscopic retrograde cholangiopancreatography (ERCP).

Breath hydrogen tests

Take samples of end-expired air; give glucose; take more samples at half-hourly intervals. If there is bacterial overgrowth there is an increase in exhaled hydrogen one hour after ingestion.

Nutritional support may be required for malabsorption.

Management otherwise depends upon the cause. For example:

• Coeliac disease requires a strict gluten-free diet.

• Pancreatic insufficiency requires the oral administration of enzymes with food.

• Blockage of the flow of bile requires surgery.

• Crohn's disease usually responds to steroids.

• Blind loop syndromes may require further surgery.

• Where bile salts are not reabsorbed, it may be necessary to give resins to bind them.¹²

• S'il y a une carence en folate et peut-être aussi en vitamine B12, il est impératif d'administrer une injection de vitamine B12 avant de commencer la supplémentation en folate. Sinon, il y a un risque de provoquer une dégénérescence subaiguë combinée de la moelle épinière.
  

Complications are related to the underlying disease.

• Lassitude is common. Children will have stunted growth.

• Untreated coeliac disease may result in small bowel adenocarcinoma or lymphoma.

• Infertility is common, especially in coeliac disease.

• Anaemia may occur.

• Rickets, osteomalacia ou ostéoporose may occur.