The dehydrated child with gastroenteritis: a case-based approach

The case: a toddler with a tummy bug

A two-year-old has had watery diarrhoea for two days and has vomited a few times. She is off her food, a bit grizzly, and her nappies are less wet than usual. Her parents wonder whether to ride it out at home or seek help. This is an everyday picture. Most gastroenteritis in children is caused by a virus, spreads easily, and settles by itself. The clinician's main job is not to name the exact bug but to work out one thing: is this child becoming dehydrated? A child who is drinking, weeing normally, alert and playing between bouts is usually safe at home. A child who is drinking little, weeing less, and becoming floppy or drowsy needs to be seen.

How to spot dehydration in a child

Dehydration means the body has lost more fluid than it has taken in. In a young child the signs to look for include a dry mouth and tongue, fewer wet nappies or less wee than usual, no tears when crying, sunken eyes, being unusually sleepy or irritable, and faster breathing. In babies, a sunken soft spot on the top of the head can be a sign. A useful everyday guide is how much a child is weeing: regular wet nappies are reassuring, while long stretches with a dry nappy are a warning. Because small children have less reserve than adults, they can tip from mildly to seriously dehydrated quite quickly, so a child who is going downhill should be reassessed sooner rather than later.

The red flags that mean urgent care

Certain features mean a child should be seen urgently rather than watched at home. Seek urgent help if a child becomes drowsy or difficult to wake, floppy or unresponsive, has no wet nappies or has not passed urine for many hours, has sunken eyes, cold or mottled hands and feet, or is breathing fast. Blood in the diarrhoea, green vomit, a swollen or very painful tummy, or vomiting that will not stop and prevents any fluid staying down are also warning signs. A high temperature in a very young baby, a stiff neck, a rash that does not fade under pressure, or a child who simply looks seriously unwell all need urgent assessment. When in doubt, it is always right to get a child checked.

How doctors assess and rehydrate a child

A clinician assessing the child looks at how alert and responsive she is, checks her pulse, breathing, how moist her mouth is, whether her eyes look sunken, and how quickly colour returns to the skin after a gentle press. Weight, wet nappies and the overall impression all help judge how dehydrated she is. For most children with mild dehydration, the treatment is to replace fluid by mouth, often using oral rehydration salts — special sachets that balance water, salts and sugar — given in small, frequent sips. This slow, steady approach is usually enough. A child who cannot keep fluids down, who is more seriously dehydrated, or who is very unwell may need fluids through a tube into the stomach or a drip in hospital, along with monitoring.

Recovery, home care and preventing spread

For most children the plan is simple: keep offering fluids in small, frequent amounts, carry on breastfeeding or formula for babies, and reintroduce normal food once they feel like eating. Full-strength fizzy drinks and fruit juices are best avoided because they can worsen diarrhoea. Diarrhoea can last up to a week and vomiting a day or two; a gradual return to normal is expected. These bugs spread very easily, so thorough handwashing with soap, not sharing towels, and keeping a child off nursery or school until 48 hours after the last episode of diarrhoea or vomiting all help protect others. The key message from this case is to watch for dehydration and its red flags, and to seek help early if a child is going downhill.