Differentials
Rotavirus or other viral gastroenteritis
SIGNS / SYMPTOMS
Common in children between the ages of 6 months and 2 years.
Results in severe dehydration and even death.
The incubation period for rotavirus disease is approximately 2 days. The disease is characterised by vomiting and watery diarrhoea for 3-8 days, and fever and abdominal pain occur frequently.[70]
Affected children are frequently simultaneously infected with both respiratory and gastrointestinal viruses, making interpretation of these findings more difficult. May co-occur with giardiasis.
INVESTIGATIONS
Enzyme-linked immunosorbent assay and latex agglutination test on stool samples will be positive for rotavirus.
Polymerase chain reaction (PCR)-based diagnostic will detect rotavirus-specific nucleic acids and other viruses depending upon the platform
Functional diarrhoea
SIGNS / SYMPTOMS
Defined as loose (mush) or watery stools without pain occurring in at least 75% of stools for a period of at least 3 months with symptom onset at least 6 months before diagnosis.
Does not result in weight loss. May co-occur with giardiasis.
INVESTIGATIONS
This is a diagnosis of exclusion and has no definitive investigation.
Coeliac disease
SIGNS / SYMPTOMS
Autoimmune process resulting from an inappropriate immune response to the dietary protein gluten.
Wide range of symptoms, including gas, recurring abdominal bloating and pain, chronic diarrhoea or constipation; pale, foul-smelling or fatty stool, weight loss/weight gain, fatigue, unexplained anaemia, behavioural changes, irritability common in children; tingling numbness in the legs (from nerve damage); bone or joint pain, muscle cramps; delayed growth in children or failure to thrive in infants; aphthous ulcers, dermatitis herpetiformis, osteoporosis (especially at a young age), iron deficiency.[71]
May co-occur with giardiasis.
INVESTIGATIONS
Test for serum IgA tissue transglutaminase (tTG) antibodies. A positive IgA tTG result should prompt small bowel biopsy with at least 4 tissue samples to confirm the diagnosis.
Adherence to a gluten-free diet may eliminate symptoms within a few months.[71]
Ulcerative colitis
SIGNS / SYMPTOMS
Onset between ages 15 and 40 years.
Almost always involves the rectum and may extend in a proximal and continuous fashion to involve other portions of the colon. Symptoms vary from intermittent rectal bleeding associated with the passage of mucus to frequent loose, bloody stools.
May co-occur with giardiasis.
INVESTIGATIONS
Colonoscopy and biopsy: vascular markings are lost due to engorgement of the mucosa, giving it an erythematous appearance. In addition, petechiae, exudates, touch friability, and frank haemorrhage may be present. Colonic involvement is continuous. Patients with more severe colitis may have macroulcerations, profuse bleeding, and copious exudates.
Giardia is not expected to cause high levels of inflammatory biomarkers in faecal samples.
Crohn's disease
SIGNS / SYMPTOMS
Onset between ages 15 and 40 years.
May involve the entire gastrointestinal tract from mouth to perianal area. Fatigue, prolonged diarrhoea with abdominal pain, weight loss, and fever, with or without gross bleeding, are the hallmarks of Crohn's disease.
Although haemoccult-positive stools are common in Crohn's disease, gross bleeding is much less frequent. May co-occur with giardiasis.
INVESTIGATIONS
Colonoscopy and biopsy: focal ulcerations adjacent to areas of normal-appearing mucosa along with polypoid mucosal changes that give a cobblestone appearance. Skip areas of involvement are typical with segments of normal-appearing bowel interrupted by large areas of obvious disease; this pattern is different from the continuous involvement in ulcerative colitis. Pseudopolyps are also often present.
Giardia is not expected to cause high levels of inflammatory biomarkers in faecal samples.
Microscopic colitis
SIGNS / SYMPTOMS
Usually middle-aged patients presenting with chronic watery diarrhoea without bleeding.
May co-occur with giardiasis.
INVESTIGATIONS
Colonoscopy and biopsy: diagnosis is made on histology. Classically characterised by colonic mucosal subepithelial collagen deposition with intra-epithelial lymphocytic infiltration.
Infectious diarrhoea
SIGNS / SYMPTOMS
Specific risk factors such as travel, HIV infection, use of antibiotics, and consumption of potentially contaminated drinking water.
May co-occur with giardiasis.
INVESTIGATIONS
Clostridium difficile toxin, polymerase chain reaction (PCR)-based diagnostic will detect pathogen-specific nucleic acids, modified acid-fast stains, stool culture, and stool for ova/parasites.
Irritable bowel syndrome (IBS)
SIGNS / SYMPTOMS
IBS is a gastrointestinal syndrome characterised by chronic abdominal pain and altered bowel habits in the absence of any organic cause. Younger patients and women are more likely to be diagnosed with IBS.
Does not result in weight loss.
May co-occur with giardiasis.
INVESTIGATIONS
Symptom-based criteria. Diagnosis of exclusion.
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