Carbohydrate malabsorption
(see "Diarrhea, Congenital" for workup of neonates and young
children with ongoing diarrhea)
Clinical manifestations
- Watery non-bloody Diarrhea
- Osmotic diarrhea (Stool osmotic gap >100)
- Abd distension
- Poor weight gain after intro of solids and weaning off breast
milk
- Diaper rash from acidic (pH<6) stool
- Suggestive of Carbohydrate malabsorption:
- Watery osmotic diarrhea (stool gap >100)
- Abdominal distention
- Diaper rash after the introduction of solids
- Normal growth in early infancy
Labs
Differentiate from other sources of malabsorption by stool pH
Stool osmotic gap:
290 - 2(Stool Na + Stool K)
- if <50 = secretory
- if >100 = osmotic
Stool in glucose, lactose, galactose, and fructose malabsorption may
also be positive for reducing substances and a low pH
Disaccharidase deficiencies
-sucrase-isomaltase
-maltase-glucoamylase
-trehalase
-lactase
Diagnosis and Treatment:
- Trial of carbohydrate free formula (Ross Carbohydrate Free
formula) with improvement in symptoms supports the diagnosis
- If carbohydrate malabsorption is suspected, challenge with
specific carbs to determine selectivity
- Disaccharidase
- Monosaccharide
- Dissaccharide activity can be measured in a endoscopic biopsy
sample from the duodenum
- Poor sampling and specimen handling may make these tests
less optimal
- Enzymes tested:
- Lactase
- Sucrase
- Maltase
- Palatinase
- Trehalase
- Inflammation and villous atrophy from other causes can produce
a secondary disaccharidase deficiency
If there is no improvement in diarrhea with dietary challenges,
consider enteric endocrinopathies (enteric anendocrinosis and
dysendocrinosis) vs congenital short gut
- EGD/Colo with Biopsies for histology and EM
- Evaluate for protein losing enteropathy (A1AT in stool and
labs showing low albumin, low IgG, and lymphopenia)