Malassimilation syndromeK30; K90.9

Malassimilation (from Latin: malus - bad, and assimilare - align) is an acute, but mostly chronic, polyätiological digestive disorder, which is caused by the inability of the organism to break down and utilize certain building blocks and elements (e.g. minerals, vitamins, trace elements, proteins) from food. The consequences are chronic diarrhoea/steatorrhoea, weight loss and deficiency syndromes due to the loss of orally supplied vital nutrients via stool excretion.

The clinical symptoms of the deficiency state become apparent through pathological changes in various organs.

Etiology:

Basically the causes of the malassimilation syndrome can be divided into 2 main groups:

• Maldigestion
• Malabsorption

Maldigestion (K30) is defined as deficient enzyme and bile secretion with consecutive disturbance of the hydrolysis of carbohydrate, protein and fat into low-molecular cleavage products or with disturbance of the emulsification of fats. The causes of maldigestion are:

Disturbed digestion of nutrients

• Lack of digestive enzymes (exocrine pancreatic insufficiency: chronic pancreatitis, cystic fibrosis, pancreatic resection).
• Inactivation of digestive enzymes: Zollinger-Ellison syndrome

Disturbed fat emulsification

• Reduced bile acid synthesis (e.g. liver cirrhosis)
• Disturbed bile acid secretion (cholestasis e.g. occlusive cholestasis or intrahepatic cholestasis)
• Reduced conjugated bile acid (bacterial overgrowth in small bowel diverticulosis, Bildsack syndrome, motility disorders of the small bowel e.g. in systemic sclerosis)
• Increased loss of bile acid (syn.: bile acid loss syndrome) in the case of resection of the terminal ileum or Crohn's disease

Malabsorption (K90.9) is defined as a disorder in the absorption of cleavage products of food from the intestinal lumen into the blood and lymphatic system. The causes of malabsorption are:

• Diseases of the mucosa of the small intestine
  • disaccharide deficiency(lactose intolerance)
  • Amino acid transport disorder (Hartnup disease)
  • Mucosal atrophy (gluten-sensitive enteropathy = celiac disease, tropical sprue)
  • Inflammatory infiltrations of the small intestine (Whipple's disease, Crohn's disease with involvement of the small intestine, small intestine infections, parasitoses, eosinophilic gastroenteritis, condition after x-ray radiation)
  • Reduction of the resorption area (small bowel resections with development of a short bowel syndrome, short circuit connections e.g. gastroileostomy, blind sack syndrome)
  • Reduction of contact time (hormone-active tumours: Zollinger-Ellison syndrome, VIPom = Verner-Morrison syndrome, neuroendocrine tumours of the small intestine, hyperthyroidism, diabetic enteropathy, Addison's disease, generalised mastocytosis, amyloidosis)
• Disturbances of the food transport
  • Abetalipoproteinemia = disturbed formation of chylomicrons
  • Ischemia: disturbances of the enteral blood flow with angina intestinalis = ischemia
  • Obstruction of the lymphatic vessels: intestinal lymphangiectasia, enteral lymphomas enteral tuberculosis, lymph node metastases.

Protein deficiency: With a serum albumin concentration of < 2.5g/dl, hypoproteinemic edema develops in the extremities, possibly pleural effusions and ascites. Furthermore, cachexia may develop.

Carbohydrate deficiency: Fermented stools, distended abdomen, flatulence, low glucose levels after oral glucose tolerance test.

Fat-soluble vitamin deficiency: vitamin A, vitamin D, vitamin E, vitamin K.

• Vitamin A deficiency: Night blindness, decreased tear secretion (conjunctivitis sicca), dry skin, hyperkeratosis(phrynoderm).
• Vitamin D def iciency: leads to rickets in young children, bone pain and osteomalacia in adults.
• Vitamin K def iciency: possibly hematoma formation and increased bleeding tendency, due to decreased coagulation factors for the prothrombin complex ( factor II, factor VII, factor IX, factor X). A drop in the Quick value is characteristic.

Potassium deficiency: general weakness and arrhythmias.

Calcium deficiency: risk of tetany, paresthesias, secondary hyperparathyroidism and oxalate kidney stones, because decreased calcium is available for intraluminal binding and thus increased reabsorption of oxalate.

Iron deficiency: hypochromic, microcytic anemia, glossitis, and oral rhagades.

Vitamin B12/folic acid deficiency: With development of macrocytic, hyperchromic anemia and neurologic symptoms.

Possibly secondary endocrine disorders (e.g. amenorrhea).

Symptoms of the causative diseases leading to malassimilation, e.g. symptoms of chronic pancreatitis, symptoms of cholestasis, symptoms of Crohn's disease.

Typical clinical symptoms (food intolerances and operations, stool inspection with control of color, consistency, odor, etc.)

Routine laboratory: blood count, serum iron, ferritin, calcium, magnesium, albumin, INR (quick value),

Signs of maldigestion (detection of stool fat content: normal < 7g/day, detection of stool weight: normal < 300g/day, signs of steatorrhea: serum carotene and vitamin A levels are reduced.

Signs of malabsorption (D-xylose test: 25g of xylose are administered orally and the xylose concentration is determined in the 5h urine and in serum; in the case of a malabsorption syndrome such as celiac disease, the xylose concentration in the 5h urine is < 4g)

In exocrine pancreatic insufficiency: enzyme substitution.

In the case of underlying inflammatory or neoplastic diseases of the small intestine, appropriate therapy for the underlying disease.

For gluten-sensitive enteropathy: gluten-free diet.

In case of lactase deficiency: low-lactose diet.

Perenteral substitution of substances that are poorly absorbed. E.g. substitution of fat-soluble vitamins (A,D,E,K), vitamin B12, iron and others.

In maldigestion, fat and protein absorption are disturbed, and to a lesser extent carbohydrate absorption (effect of salivary lamylase).

Most nutrients are already absorbed in the proximal small intestine after enzymatic splitting. Exception: vitamin B12 and bile acids are only absorbed in the terminal ileum. Only water and electrolytes are absorbed in the colon.

1. Bang Jørgensen B et al (1991) Short report: lipid and vitamin B12 malassimilation in pancreatic insufficiency. Aliment Pharmacol Ther 5:207-210.
2. Brăgelmann R et al. (1996) Nutrient malassimilation following total gastrectomy. Scand J Gastroenterol Suppl 218:26-33.
3. Heckl S et al (2016) Evidence of impaired carbohydrate assimilation in euthyroid patients with Hashimoto's thyroiditis. Eur J Clin Nutr 70:222-228.
4. Kleine-Tebbe J et al. (2016) Food Allergy and Intolerance: Distinction, Definitions and Delimitation. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 59:705-722.