Synopsis
Separate benign high-frequency stool from persistent intestinal disease, quantify effects on growth and nutrition and use targeted stool, blood and specialist testing to identify treatable malabsorption.
- Persistent diarrhoea usually means at least 14 days; symptoms beyond 4 weeks are often termed chronic, but severity and growth effect matter more than the label.
- First-line assessment plots weight, height and BMI, characterises stool volume, blood, oil, nocturnal symptoms and triggers, and reviews diet, travel, medicines and development.
- A thriving preschool child with daytime loose stools, excess juice and no red flags may have toddler's diarrhoea; reduce juice, restore dietary fat and avoid unnecessary exclusions.
- Send stool culture or molecular testing for infection when blood, travel, exposure, immune compromise or persistent postinfectious illness supports it; add ova or parasite tests to the epidemiology.
- Test coeliac serology with total IgA and tTG-IgA while the child continues gluten; use IgG-based tests if IgA deficient.
- FBC, CRP or ESR, albumin, renal and liver profiles, ferritin and selected vitamins assess inflammation and nutritional consequence when growth or systemic features are abnormal.
- Faecal calprotectin supports intestinal inflammation but varies with age and infection; it does not diagnose IBD or replace specialist endoscopy.
- Pale greasy stool, faltering growth and respiratory features prompt sweat testing and faecal elastase for cystic fibrosis or pancreatic insufficiency.
- Management is cause-specific and dietitian supported; do not prescribe antimotility drugs or broad exclusion diets before diagnosis.
Key red flags
Weight loss, crossing down centiles, reduced height velocity, oedema or pubertal delay suggests nutritionally significant disease.
Visible blood, nocturnal stool, persistent fever, severe pain, perianal fistula or oral ulcers raises concern for inflammatory bowel disease or infection.
Pale bulky oily stool, recurrent chest infection, clubbing or salt-loss episodes suggests pancreatic insufficiency or cystic fibrosis.
Persistent diarrhoea in an infant, especially after neonatal onset, can cause rapid electrolyte and nutritional compromise and needs early specialist review.
Immunodeficiency, recent antibiotics, foreign travel, untreated water or affected contacts changes the infectious differential and testing.
Abdominal distension with bilious vomiting, guarding or absent stool and flatus requires urgent obstruction assessment.
Investigation priorities
Determine nutritional consequence and identify functional juice, fat or feeding patterns before invasive testing.
Management branches
Loose stool persists beyond the expected acute course.
- Assess hydration, weight trend, blood, nocturnal symptoms, fever, pain and immune status.
- Admit or obtain urgent paediatric review for instability, severe malnutrition, major bleeding or surgical features.
- Preserve gluten and ordinary nutrition while planning targeted testing.
The child is stable but infection, inflammation or malabsorption remains possible.
- Send pathogen studies from travel, blood, exposure and duration clues.
- Request coeliac serology, inflammatory or nutritional tests and calprotectin only where they answer a defined question.
- Use sweat chloride, elastase or specialist imaging for steatorrhoea and pancreatic or biliary clues.
- Refer for endoscopy and biopsy when growth, blood, inflammation or persistent unexplained symptoms warrant it.