You are an intern in a paediatrics rotation, 9 month old Samantha Longley presents with her mother. They have been referred by their GP. Samantha has been losing weight over the last 2 months and is more unsettled and seems to be in pain after meals. Her mother also informs you that Samantha's bowel motions are more frequent and more liquid than before.
She was born at term following an uneventful pregnancy and delivery.
At birth: weight 3.0 Kg; length 51 cm; head circumference 34.5 cm.
She had been growing normally along the 50th centile up until 6 months of age, when her weight gain slowed;
She currently weighs 7.0 Kg, length 70 cm, head circumference 44.5 cm.
Diarrhoea is the most common presentation and may be accompanied by loss of appetite, decreased physical activity, lethargy and growth failure. Children with coeliac disease may have decreased appetite, and are often cranky and irritable. In contrast, children with pancreatic insufficiency often develop a voracious appetite. In children with failure to thrive, such as Samantha, a detailed dietary history is required. Occasionally, parents manipulate the child's diet in an attempt to control the diarrhoea, which can lead to significant dietary insufficiency with attendant weight loss. Assessment of the age of introduction of various foods into the diet may give insight to the underlying diagnosis. Onset of symptoms 3-6 months after the introduction of wheat products suggests the possibility of coeliac disease. Onset shortly after introduction of cow's milk suggests cow's milk protein intolerance. History of overseas travel is important, as some unusual infections, such as amoebic dysentery, can cause chronic bloody diarrhoea.
The nature of the loose stool is important to ascertain, as it provides important clues to the pathophysiology and thus aetiology. Diarrhoea can be thought of in terms of fatty stools (steatorrhoea), watery diarrhoea (osmotic because of carbohydrate malabsorption or secretory) and bloody diarrhoea.
Assessment of general health is important, as many gastrointestinal disorders exhibit extraintestinal manifestations. Cystic fibrosis, Shwachman syndrome and immunodeficiency disorders are associated with infections, particularly sinopulmonary infections. Delayed pubertal development can accompany many chronic disorders but is particularly prevalent in Crohn disease
Family history may be of note. Cystic fibrosis, primary disaccharidase deficiencies and abetalipoproteinaemia are recessively inherited. Coeliac disease and inflammatory bowel disease are more frequently observed in first-degree relatives.
Physical examination includes assessment of growth, nutritional status and pubertal development. Plotting percentile charts is mandatory. A child who is growing normally is unlikely to be suffering from serious gastrointestinal disease. Plotting longitudinal measurements, if available, is very important as it may give clues to the onset of disease and could indicate the diagnosis. Other physical signs of malabsorption and specific nutritional deficiencies include: loss of muscle bulk and subcutaneous fat; peripheral oedema (hypoproteinaemia); bruising (vitamin K deficiency); glossitis and angular stomatitis (iron deficiency); finger clubbing (cystic fibrosis, Crohn disease, coeliac disease); skin rashes in coeliac disease (dermatitis herpetiformis) and inflammatory bowel disease (erythema nodosum, pyoderma gangrenosum); and specific skin disorders associated with zinc, vitamin A and essential fatty acid deficiencies. Rickets (vitamin D deficiency) is very uncommon in sunny climates, even in conditions with severe steatorrhoea. It is important to examine carefully as there are many extraintestinal manifestations of gastrointestinal disease and malnutrition.
Initial clinical assessment and stool examination will suggest the diagnosis in most children. Stool microscopy and measurement of stool-reducing substances can be performed in the clinician's office and are readily available 'bedside' tests.
In patients with steatorrhoea: full blood count and differential white cell count; serum triglycerides/cholesterol; sweat test; small bowel biopsy; X-ray of long bones.
In patients with carbohydrate maldigestion/malabsorption: breath hydrogen testing; small bowel biopsy/mucosal disaccharidase activities; inpatient dietary manipulation with close observation of stool output.
In patients with bloody diarrhoea: gastroscopy and colonoscopy; biopsy of small bowel and colon; sometimes radiology looking for inflammatory bowel disease.
Practical points: Diagnosis is not by exclusion; A thorough history, physical examination and stool examination will suggest the diagnosis in most disorders; simple well-directed investigations usually confirm the clinical diagnosis; there is no such thing as a 'malabsorption workup'
Fat: Requires bile salts (form micelles), pancreatic enzymes (lipase and colipase), and intact intestinal mucosa. Breakdown products form chylomicrons which exit into lymphatic system then systemic circulation.
Protein: Begins in stomach (pepsin and acid). Most hydrolysis occurs in jejunum by pancreatic proteases. Products are amino acids and oligopeptides, absorbed by specific membrane transporters.
Carbohydrate: Starch broken down by amylase; brush border enzymes (sucrase-isomaltase, glucoamylase) produce glucose. Glucose and galactose absorbed by SGLT (energy-dependent); fructose by GLUT-5 (facilitated diffusion).
| Nutrient | Clinical Features |
|---|---|
| Protein | Growth failure, Muscle wasting, Hypoproteinaemic oedema |
| Fat | Weight loss, Muscle wasting, Deficiency of vitamins A,D,E,K |
| Carbohydrate | Weight loss |
| Salt/water | Electrolyte disturbances, Growth failure, Dehydration |
| Vitamin A | Night blindness, Skin rash, Dry eyes (xerophthalmia) |
| Vitamin D | Rickets, Hypocalcaemia |
| Vitamin K | Bruising (coagulation defects) |
| Vitamin E | Anaemia, Peripheral neuropathy |
| Vitamin B12 | Megaloblastic anaemia, Irritability, Hypotonia, Peripheral neuropathy |
| Folate | Megaloblastic anaemia, Irritability |
| Iron | Microcytic anaemia, Delayed development |
| Calcium | Rickets, Irritability, Seizures |
| Zinc | Diarrhoea, Skin rash (mouth, perineum, fingers/toes), Poor growth |
Steatorrhoea: fatty stools, fat globules seen on microscopy, classically stools float in toilet bowl
Watery diarrhoea: very fluid and high volume, may be osmotic (carbohydrate malabsorption) or secretory
Bloody diarrhoea: Either visible blood or microscopic. May contain mucous if inflammatory cause.
Coeliac disease (gluten enteropathy): Intestinal injury induced by gluten (found in wheat, barley, rye, oats). Incidence may be as high as 1 in 70.
Presentation: 'Classical' (9-18 months): anorexia, weight loss, abdominal distension, wasting, chronic diarrhoea ± iron deficiency anaemia, hypoproteinaemic oedema, fat-soluble vitamin deficiency. Older child: growth failure, chronic diarrhoea, iron deficiency.
Diagnosis: Antibody screening (antigliadin, anti-endomysial, antitissue transglutaminase - sensitivity/specificity >95%). Small bowel biopsy is mandatory for diagnosis (performed while on unrestricted diet). No empirical trial of gluten-free diet. Definitive diagnosis important as treatment is lifelong gluten-free diet.
Cystic fibrosis: Commonest cause of pancreatic malabsorption in Caucasians (incidence 1 per 2000). Inborn error in epithelial chloride secretion (CFTR).
Organs affected: GI tract, liver, sinopulmonary tract, pancreas, sweat glands, vas deferens.
Pathophysiology: Viscous secretions in lung, gut, pancreas lead to: chronic suppurative lung disease, nasal polyps, pancreatic insufficiency, intussusception, meconium ileus, infertility, elevated sweat sodium/chloride.
Malabsorption causes malnutrition with specific nutrient deficits (hypoalbuminaemic oedema, vitamin A deficiency, essential fatty acid deficiency). Median life expectancy 30 years.