How does oral rehydration solution (ORS) work, and what are its advantages?

ORS works through the sodium-glucose co-transport mechanism in the small intestine: glucose drives sodium absorption, and water follows the osmotic gradient passively. This continues to work even in gastroenteritis, giving effective, low-cost, easily available rehydration with fewer complications than IV fluids (overall failure rate ~3.6%).

Clinical relevance. Understanding the sodium-glucose co-transport basis of ORS explains why oral rehydration is first-line and highly effective.

More Detail

Oral rehydration solution (ORS)

ORS is the cornerstone of diarrhoea management because it exploits an intact absorptive mechanism.

Mechanism

• The sodium-glucose co-transport mechanism in the small intestine: glucose-coupled sodium absorption remains intact in gastroenteritis.
• Water follows the solute (osmotic) gradient passively, rehydrating the child.

Advantages

• Faster rehydration with fewer complications than IV fluids (overall failure rate about 3.6%).
• Low cost, easily available, and can be given by carers.

Limitations

• Vomiting, refusal to drink, or glucose malabsorption; preparation/storage errors.
• Adding juice changes the composition - use standard/appropriate ORS.