Epidemiology and Aetiology

• Diarrhoea is the second leading cause of death in children under five globally, with the highest burden concentrated in LMICs.
• Billions of diarrhoeal episodes occur annually, causing substantial outpatient visits, hospitalisations and economic losses in low‑resource settings.
• Common infectious causes in LMICs include viruses (notably rotavirus), bacteria such as Shigella, enterotoxigenic and enteropathogenic Escherichia coli, and parasites such as Cryptosporidium.

Pathophysiology and Risk Factors

• Diarrhoea arises from increased intestinal secretion, reduced absorption or both, often triggered by enteric pathogens that damage enterocytes or alter ion transport.
• Major risk factors in LMICs include unsafe water, poor sanitation, inadequate hand hygiene, low maternal education and crowded living conditions.
• Malnutrition and micronutrient deficiencies, especially zinc deficiency, increase susceptibility, prolong episodes and heighten the risk of death.

Principles of Clinical Management

• The cornerstone of management is prompt rehydration, primarily using low‑osmolarity ORS to prevent or treat dehydration.
• WHO/UNICEF recommend ORS plus 10–14 days of zinc supplementation in all children with acute diarrhoea to shorten duration and reduce recurrence.
• Continued age‑appropriate feeding, including breastfeeding, is strongly advised to prevent nutritional deterioration and support intestinal recovery.

Assessment and Classification

Generally, the assessment of a child with diarrhoea is important before the commencement of the treatment. The child is examined, and a brief history is taken as part of the critical assessment. Determining the degree of dehydration, diagnosing any dysentery, assessing feeding habits and the child's nutritional state, diagnosing any coexisting illnesses, and finding out the child's history of measles vaccinations are the goals. The following steps should be taken.

• Clinical assessment focuses on the degree of dehydration (none, some, severe) using signs such as general condition, thirst, tears, skin turgor and urine output.
• WHO guidelines provide structured treatment plans (A, B and C) for outpatient, oral rehydration‑centre and inpatient management based on dehydration status.
• Identification of danger signs (lethargy, inability to drink, persistent vomiting, blood in stool, convulsions) guides urgent referral and intensive care; that is, this assessment will determine the treatment plan and other recommendations for the care of the child.

TABLE SHOWING HOW TO ASSESS CHILD WITH DIARRHOEA DISEASE FOR DEHYDRATION 

Determining the degree of dehydration and selecting the treatment plan as shown in the table above, the degree of severity is determined according to the three columns in the table above. Two or more signs in one column, including at least one key sign, mean the patients fall in that category and require the corresponding treatment plan.

Rehydration and Pharmacologic Therapy

• Low‑osmolarity ORS (75 mmol/L sodium, 75 mmol/L glucose, total osmolarity 245 mOsm/L) reduces stool output, vomiting and need for IV fluids compared with older ORS formulations.
• For children with some dehydration, ORS is given at 75 ml/kg over 4 hours, with reassessment and continued replacement for ongoing losses.
• Intravenous Ringer’s lactate or normal saline is reserved for severe dehydration, shock or inability to tolerate oral therapy.
• Zinc (10–20 mg daily for 10–14 days, according to age) decreases the duration and severity of diarrhoea and offers protective effects against subsequent episodes.
• Antibiotics are indicated only for specific conditions such as cholera with severe dehydration, dysentery (suspected Shigella), confirmed invasive bacterial infection or certain parasitic infections.
• Routine use of antidiarrhoeal drugs (e.g. loperamide) is discouraged in children due to risk of ileus and toxicity, and they offer little benefit compared with ORS and zinc.

Nutritional and Supportive Management

• Guidelines emphasise early resumption and continuation of normal or increased feeding, including breast‑feeding on demand, to prevent weight loss and promote mucosal healing.
• In LMIC settings, locally available, energy‑dense and micronutrient‑rich foods are recommended over specialised formulas, with lactose restriction considered only in suspected or proven intolerance.
• Vitamin A and zinc supplementation, along with catch‑up growth strategies after illness, help reduce long‑term adverse outcomes.

Public Health and Health‑System Interventions

• Expansion of ORS and zinc coverage is essential, yet many children in LMICs still do not receive these life‑saving therapies or receive inadequate fluids.
• Community‑based programmes promoting handwashing with soap, safe drinking water, sanitation, rotavirus vaccination and health education significantly reduce diarrhoeal incidence and severity.
• Training health workers and caregivers to recognise dehydration, avoid unnecessary antibiotics and use ORS/zinc correctly improves adherence to guidelines and reduces mortality.

Complications of Diarrhoeal Disease

• Dehydration and shock are the most immediate life‑threatening complications and account for many diarrhoea‑related deaths in young children in LMICs.
• Electrolyte abnormalities (hyponatraemia, hypernatraemia, hypokalaemia) and metabolic acidosis can cause seizures, arrhythmias and impaired consciousness.
• Severe or prolonged episodes may lead to acute kidney injury, particularly when compounded by sepsis and delayed fluid resuscitation.
• Recurrent or persistent diarrhoea contributes to malnutrition through reduced intake, malabsorption and intestinal inflammation, creating a vicious cycle of illness and growth failure.
• Chronic effects in childhood include stunting, cognitive impairment, reduced school performance and diminished adult productivity.
• Certain pathogens, such as enterohaemorrhagic E. coli, may cause haemolytic uraemic syndrome, while invasive infections can result in bacteraemia and multi‑organ failure.

Conclusion

Diarrhoeal disease in LMICs is largely preventable and treatable, yet remains a major contributor to child and adult morbidity and mortality. Scaling up use of low‑osmolarity ORS, zinc, continued feeding, targeted antibiotic therapy and robust public‑health interventions is critical to reduce complications, interrupt the malnutrition–diarrhoea cycle and move towards global child‑survival targets.