Disorders of Malabsorption
All disorders of malabsorption are associated with diminished intestinal absorption of one or
more dietary nutrients. Malabsorption can result from a defect in the nutrient digestion in the
intestinal lumen or from defective mucosal absorption. Malabsorption disorders can be
categorized into generalized mucosal abnormalities usually resulting in malabsorption of multiple
nutrients or malabsorption of specific nutrients (carbohydrate, fat, protein, vitamins, minerals,
and trace elements). Almost all the malabsorption disorders are accompanied by chronic
diarrhea.Disorder that cause generalized defect in assimilation of nutrients tend to present with
similar sign and symptom such as : abdominal distention , pale , foul – smelling bulky stool ,
muscle wasting , poor weight gain or weight loss and growth retardation , stool may be greasy
appearing ( steatorrhea ) or may be normal .
The clinical features of malabsorption disorder affecting individual intestinal digestive enzyme
typically differ from those of generalized malabsorption syndromes . and some present without G
. I . T . symptoms .
Causes of generalized Malabsorption syndromes
1- intestinal causes :
A- anatomic defect : e . g . massive resection stagnant loop syndrome ,
congenital short gut
B- chronic infection : giardiasis , immune deficiency .
C- others : celiac disease , tropical sprue ,
idiopathic diffuse mucosal lesion
2- hepatobiliary causes : biliary atresia , other
cholestatic stasis.
3- exocrine of pancreas : chronic protein - calorie
malnutrition , cystic fibrosis , rare like schwachman – diamond syndrome chronic
pancreatitis
Evaluation of Children with Suspected Intestinal Malabsorption:
In a child presenting with chronic or recurrent diarrhea, the initial work-up should include
stool cultures and antibody tests for parasites, stool microscopy for ova and parasites such as
Giardia, and stool occult blood and leukocytes to exclude inflammatory disorders
A complete blood count including peripheral smear for microcytic anemia, lymphopenia
(lymphangiectasia), neutropenia (Shwachman syndrome), and acanthocytosis
(abetalipoproteinemia) is useful.
Investigations for Carbohydrate Malabsorption
1-using a Clinitest reagent that identifies reducing substances,
2- Breath hydrogen test, is used to identify the specific carbohydrate (lactose, sucrose,
fructose, or glucose) that is malabsorbed.
3- Small bowel mucosal biopsies can measure mucosal disaccharidase (lactase, sucrase,
maltase, palatinase) concentrations directly.
Investigations for Fat Malabsorption
The presence of fat globules in the stool suggests fat malabsorption, Quantitative
determination of fat malabsorption requires a 3-day stool collection for evaluation of fat
excretion.
Investigations for Protein Losing Enteropathy
Dietary and endogenous proteins secreted into the bowel are almost completely absorbed.
Excessive bowel protein loss usually manifests as hypoalbuminemia. However, the most
common cause of hypoalbuminemia in children is a renal disorder; therefore, urinary protein
excretion must be determined. Other potential causes of hypoalbuminemia include liver
disease (reduced production) and inadequate protein intake. Measurement of stool α1-
antitrypsin is a useful screening test for protein-losing enteropathy. This serum protein has a
molecular weight similar to albumin's; however, unlike albumin it is resistant to digestion in
the gastrointestinal (GI) tract.
Investigations for Exocrine Pancreatic Function
Fecal elastase-1 estimation is a sensitive test to assess exocrine pancreatic function in
chronic cystic fibrosis and pancreatitis. Serum trypsinogen concentration can also be used as
a screening test for exocrine pancreatic insufficiency.
Investigations for Intestinal Mucosal Disorders;
Establishing a specific diagnosis for malabsorption often requires histologic examination of
small bowel mucosal biopsies. These are obtained during endoscopy.
Imaging Procedures;
Plain radiographs and barium contrast studies might suggest a site and cause of intestinal
motility disorders.
Celiac disease ( Gluten-Sensitive Enteropathy)
Celiac disease is an immune-mediated disorder elicited by the ingestion of gluten in
genetically susceptible persons and characterized by chronic inflammation of the small
intestine. It is considered an autoimmune condition because of the presence of anti–TG2
antibodies and the association with other autoimmune diseases (thyroid, liver, diabetes,
adrenal), it mostly affect people of northern Europe , it has been also documented in Indian
Sudanese , Chinese , afro-caribben and middle east people , the most common age of
presentation is 6 m. – 2 y. of age , it is a permanent intolerance to gluten . there is a genetic
predisposition , celiac disease is associated with certain human leukocyte antigen ( H L A )
type ( B 8 ,DR 7 , DR 3 , DQW2 ) .
the a symptomatic form of the disease may be 5 – 7 times more common than the
symptomatic disease .
clinical manifestations
the mode of presentation is variable ; most patient present with diarrhea , children can have
failure to thrive or vomiting as the only presentation . anorexia is common . infants are often
clingy and irritable . pallor and abdominal distention are common . Occasionally there is
constipation, rectal prolapse, or intussusception. The most common extraintestinal
manifestation of celiac disease is iron-deficiency anemia, unresponsive to iron therapy.
an increased prevalence of celiac disease has been noted in children with selective I G A
deficiency ,diabetic mellitus , chronic rheumatoid arthritis , thyroiditis , hypothyroidism ,
Addison disease , pernicious anemia, alopecia and Down syndrome
Evaluation
Anemia and hypoproteinemia may be present . the incidence of iron deficiency anemia is
variable , megaloplastic anemia can occur .
Serological markers include antibodies to gliadin , reticulin endomysium and tissue
transglutaminase ( E T G ) .the sensitivity of I.G.G and I.G.A. antigliadin antibodies is
believed to be 100% and 89% respectively . while the specificity is 95.5% for I.G.A and 86%
for I.G.G. antigliadin antibodies .
antigliadin antibodies can also be present in other conditions such as cows milk intolerance ,
crohn disease , I.G.A .nephropathy , eosinophilic enteritis , tropical sprue and dermatitis
herpitiformis .
anti endomysial antibodies are also I.G.A antibodies , the sensitivity reported to be near
100% while the specificity is around 98% . the use of both antigliadin antibodies and anti
endomysial antibodies together in screening of Celiac disease patients confers posativ and
negative values of almost 100% .
an Elisa for both I.G.A and I.G.G. t.T.G. is an attractive screening test , is easier to
standardize and doesn’t require the use of human or animal tissue . it is also valuable in
screening a symptomatic patient who have type 1 diabetes , history of first degree relative
with diabetes type 1 and family member with Celiac disease
. the combination of both clinical symptoms and serological marker may suggest the
diagnosis of Celiac disease , but histological confirmation is mandatory because it remains
the gold standard .
in the past in the diagnosis of Celiac disease is confirmed by showing that the small bowel
biopsy is return to normal by within 1-2 y . after starting gluten – free diet and then to
rechallenge the patient with a gluten diet and repeat the biopsy to demonstrate the return of
the intestinal lesion .
now according to The European Society for Pediatric Gastroenterology, Hepatology and
Nutrition (ESPGHAN) current criteria, the 2 requirements mandatory for the diagnosis of
celiac disease are the finding of villous atrophy with hyperplasia of the crypts and abnormal
surface epithelium, while the patient is eating adequate amounts of gluten, and a full clinical
remission after withdrawal of gluten from the diet. The finding of circulating IgA celiac
disease–associated antibodies at the time of diagnosis and their disappearance on a gluten-
free diet adds weight to the diagnosis. A control biopsy to verify the consequences of the
gluten-free diet on the mucosal architecture is considered mandatory only in patients with an
equivocal clinical response to the diet. Gluten challenge is not considered mandatory except
in situations where there is doubt about the initial diagnosis, for example, when an initial
biopsy was not performed or when the biopsy specimen was inadequate or atypical of celiac
disease.
Histological finding
By light microscope the mucosal lesion that seen on small bowel biopsy is short , flat .villa ,
deepened crypt with increased number of lymphocytes in the epithelial layer . Rota virus
enteritis , Giardia lymblia , tropical sprue , kwashiorkor , cows milk protein or soy protein
intolerance can cows similar lesion of celiac disease but not the marked abnormalities of the
enterocytes .
Treatment
Required a lifelong , strict gluten – free diet . all wheat , rye and barley products should be
eliminated from the diet . some physicians ( dietitian ) allow oats in the diet . vitamins and
ion supplementation is advisable .
Treatment of celiac crisis ( severe diarrhea , weight loss , hypocalcaemia and
hypoproteinemia ) is supportive and include the use of corticosteroid .
Compliance with a strict gluten - free diet can be followed with serological markers . the
antibodies will decrease to normal on strict gluten - free diet , small amounts of gluten in the
diet will result in elevation of the antibodies .
Prognosis
The response to strict gluten - free diet is gratifying , improvement in mood and appetite
followed by lessening of diarrhea . in most cases changes occur within 1 weak of starting
therapy . teenagers often became non compliant , unfortunately this is an age when the
disease become symptomatically quiescent and a teenagers may believe that the disorder has
resolved .
The development of malignancy (malignancy of esophagus , stomach, pharynx and intestine )
Is increased in patient with celiac disease especially in those with poor compliance so strict
gluten - free diet is the best possible prophylaxis . no complications from long term gluten -
free diet treatment are recognized .