Diarrhoea and vomiting

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7.8 Diarrhoea and vomiting

Christopher Webber

Essentials

1 ‘ABC fluids in and out’ is a useful tool in taking a history.
2 Not all diarrhoea and vomiting is gastroenteritis.
3 Vomiting may be a non-specific symptom of a more serious medical problem.
4 The differential diagnoses are extensive.
5 Young infants with diarrhoea must be managed with caution.

Introduction

Common symptoms

Vomiting and diarrhoea are common symptoms that affect infants and children. These symptoms may occur separately or in combination. Clinicians must exercise caution when evaluating infants presenting with fever and vomiting who do not have diarrhoea, as the list of differential diagnoses is extensive, including some conditions with significant morbidity and mortality.

Frequency of presentation

By far the commonest condition causing vomiting and diarrhoea in children is gastroenteritis. A urinary-tract infection (UTI) must be considered in all infants with vomiting, with or without fever. The presence of diarrhoea makes a urine infection much less likely, and in this situation the diagnosis is more likely to be gastroenteritis.

Definitions

Vomiting is an active process involving muscular contraction expelling the stomach contents orally. In comparison, gastro-oesophageal reflux is the passive regurgitation of gastric contents, most commonly liquid. In the newborn and young infant gastro-oesophageal reflux is common and may be considered normal if it is not associated with consequences like pain or failure to thrive.

Diarrhoea refers to the frequency and consistency of stool being frequent, loose or liquid. The stool may also contain blood and mucous, both of which are abnormal.

Fever is present when the body’s temperature is elevated above normal. Actual definitions of fever vary, but a core temperature of about 36.5–37.2°C is normal. The site used to make the measurement also affects measured temperature. Generally aural (tympanic) temperatures are less accurate. Per-axilla temperatures are lower than rectal temperatures by about 0.5–1°C. Although rectal temperatures more closely reflect the body’s core temperature, per-axilla temperatures are more convenient to measure and socially acceptable to the patient. Needless to say, an infant with cardiovascular compromise and peripherally ‘shutdown’ should have a rectal temperature checked, as a per-axilla temperature may not accurately reflect core temperature and falsely reassure the physician.

Clinical evaluation

History

Presenting complaint and past history

Always listen to the parents or carers of the child. Generally, they know the infant or child best and physicians are unwise to ignore their concerns. Explore the symptoms further and in more detail, if necessary. Is there blood in the vomitus, or blood or mucus in the stool? Sometimes important associated symptoms are not volunteered by parents, and are only alluded to when directed by a focused history. Specific information regarding the nature and content of the vomiting and diarrhoea needs clarification. In the child with a possible infectious condition, it may be important to clarify whether there have been infectious contacts or recent overseas travel. Review of the past history should include any significant medical or surgical problems and whether the child is thriving.

ABC – fluids in and out

This schema provides a simple structure for obtaining the history, and may be used to advise parents about concerning symptoms that may develop subsequently. Alertness and activity (A) provides information about the neurological state of the child. Lethargy and poor interactivity are concerning symptoms in a young child. The behaviour of the baby whilst feeding is also important. Parents may note poor suck and sleepiness during feeding; and the breastfeeding mother may comment more precisely about the quality of the infant’s suck. Breathing (B), specifically rapid or laboured breathing, and poor circulation (C), as indicated by mottling and coolness of the peripheries, are also worrying signs.

The child’s fluid intake and urine output as a percentage of usual or normal provide very important markers of the unwell infant or child. The number and ‘wetness’ of the nappies is used as the indicator of urine output. Thus, using an evaluation of ‘fluids in and out’, one should be concerned when these are less than 50% of normal for the child.

Examination

General observation

In the absence of a life-threatening emergency it is always worthwhile to make a careful observation of the child, either whilst talking with the carer or to the child. This general observation phase is invaluable in the paediatric assessment, particularly in young children. During this observation look and listen for the following:

Airway noises (stridor, sturtor, grunt or wheeze).
Tachypnoea (measure the respiratory rate).
Colour (centrally and peripherally, look for cyanosis and mottling).
Alertness and activity (or inter-activity, particularly with child’s carer[s]).

Note that the ABCD approach (airway, breathing, circulation, disability) is utilised.

Assessment of the state of hydration is critical. It is well recognised that clinicians tend to overestimate the degree of dehydration, consequently excessive amounts of intravenous fluid may be administered. Accurate premorbid and current weight may aid this assessment. The following is a revised guide for the assessment of dehydration:

• < 3% – no clinical signs; reduced urine output;
• 3% – mild dehydration; mild tachycardia, dry mucous membranes;
• 5% – moderate dehydration; lethargy, tachycardia, reduced skin turgor, sunken eyes/fontanelle;
• 10% – severe dehydration; clinical signs of shock (tachycardia, thready pulses, reduced perfusion, particularly centrally).

Always check carefully for a rash, as petechiae and purpura may be inconspicuous or subtle. Examination of the ears, nose and throat, is frequently left until the end of the examination, to avoid potential distress impairing the remainder of the examination.

Cardiovascular and respiratory status

It is important to evaluate the cardiovascular and respiratory systems in the infant with vomiting for the following reasons:

• shock may be present due to either septicaemia or fluid loss from vomiting and/or diarrhoea;
• septicaemia may be the cause of the symptoms;
• pneumonia or other respiratory infections may cause vomiting;
• effortless tachypnoea may indicate a metabolic acidosis.
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