Define Persistent Diarrhoea. Describe its pathophysiology, causes, investigations and management.

Definition

• Persistent diarrhoea is an episode of diarrhoea, presumed to be of infectious origin, that starts acutely but lasts for 14 days or more.
• It must be distinguished from chronic diarrhoea (≥ 14 days but usually of a non-infectious, often congenital cause).
• Persistent diarrhoea carries a high risk of malnutrition and death.

Risk Factors

• Young age (< 6 months) and malnutrition (a bidirectional relationship).
• Recent acute diarrhoea; lack of breastfeeding; artificial/animal-milk feeding.
• Recent measles; immunodeficiency (including HIV); previous inappropriate antibiotic use.
• Micronutrient deficiency (zinc, vitamin A).

Pathophysiology

• Persistent mucosal injury → villous atrophy → reduced absorptive surface and loss of brush-border enzymes.
• Secondary lactose (disaccharidase) deficiency → osmotic diarrhoea on milk feeds.
• Cow's-milk / soy protein sensitivity and small-bowel bacterial overgrowth.
• A vicious cycle of infection → mucosal damage → malabsorption → malnutrition → impaired mucosal repair & immunity → continued diarrhoea.

Causes

• Persistent/sequential enteric infection (E. Coli, Shigella, Salmonella, Cryptosporidium, Giardia).
• Post-enteritis lactose intolerance and cow-milk protein intolerance.
• Underlying malnutrition and micronutrient deficiency.

Clinical Evaluation

• Assess hydration and nutritional status (weight, oedema, MUAC) — the two priorities.
• History — duration, stool character (watery vs bloody), feeds (milk relation), prior antibiotics, associated infections.
• Look for systemic infection (pneumonia, UTI, sepsis, TB) and signs of specific deficiencies.

Investigations

• Stool — microscopy (ova, cysts, pus cells, RBCs), reducing substances & pH (low pH + positive reducing substances = lactose intolerance), culture.
• Blood — CBC, electrolytes, blood glucose; screen for HIV and systemic infection.
• Assess for associated deficiencies (zinc, vitamin A).

Management — Principles

• Treat & prevent dehydration — ORS (some/severe dehydration by Plans B/C); most children have no dehydration.
• Nutritional management is the cornerstone:
• Continue breastfeeding.
• Reduce the lactose load — replace animal milk with yoghurt/curd or a low-lactose diet; give energy-dense, frequent, mixed cereal-based feeds.
• Provide adequate calories (~150 kcal/kg/day) for catch-up; a lactose-free/milk-free diet only if the above fails.
• Micronutrients — zinc for 14 days, plus vitamin A, folate, copper and multivitamins.
• Antibiotics only for identified pathogens / dysentery / associated systemic infection (not routine).
• Treat associated infections (pneumonia, UTI, sepsis).

Complications

• Progressive malnutrition and growth faltering; recurrent dehydration.
• Electrolyte disturbances; sepsis; and increased mortality.

Prevention

• Exclusive breastfeeding; appropriate complementary feeding; avoid unnecessary antibiotics in acute diarrhoea.
• Zinc supplementation, measles & rotavirus immunisation, vitamin A, and good hygiene/sanitation.

Clinical Features

• Prolonged (≥ 14 days) loose stools, often with a relation to milk feeds (suggesting lactose intolerance).
• Weight loss / growth faltering and features of malnutrition and micronutrient deficiency.
• Recurrent dehydration; perianal excoriation (from acidic, sugary stools); and features of any underlying infection.

Step-wise Dietary Management (the Cornerstone)

Follow-up & Monitoring

• Monitor weight gain, stool frequency and hydration daily during treatment.
• A successful diet produces reducing stool frequency and steady weight gain within a few days.
• Ensure completion of zinc (14 days) and vitamin A; catch-up nutrition after recovery.

When to Refer / Investigate Further

• Failure to respond to standard dietary management; severe malnutrition with complications.
• Suspected specific cause — coeliac disease, immunodeficiency/HIV, congenital diarrhoea, or IBD.

Micronutrient & Mineral Supplementation

• Give double the RDA of vitamins & minerals for 2 weeks — including folate, vitamin A, copper and magnesium.
• Zinc for 14 days is essential (it restores the gut mucosa and reduces relapse).
• Treat iron-deficiency anaemia during the recovery phase.

Criteria for Hospital Admission

• Severe dehydration or inability to feed; systemic infection (sepsis, pneumonia).
• Severe acute malnutrition; young infant (< 4 months); failure of home/OPD management.
• Any danger sign — lethargy, high fever, persistent vomiting, convulsions.