Diarrhoea and vomiting

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7.8 Diarrhoea and vomiting

Christopher Webber

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.

The pulse rate and pulse volume may identify a rapid thready pulse indicating poor perfusion. Capillary refill is often thought to be a poor indicator of circulatory status, as the peripheral perfusion (hands and feet) may be affected by environmental temperature. The comparison of central (anterior chest) and peripheral capillary refill, with other data like heart rate, pulse volume and consciousness state, allows an assessment of the adequacy of the circulation. The presence of shock indicates inadequate tissue perfusion. It is present when there is a rapid, thready pulse, delayed capillary refill, especially if central (>2 seconds), and abnormal neurological status including agitation, lethargy, or coma. The diagnosis of shock is not reliant on the presence of hypotension, particularly in children. Delay in identifying shock until the child is hypotensive risks severe compromise and potential progress to cardiac arrest.

Septicaemia, with or without meningitis, may cause fever, vomiting and diarrhoea. Some bacterial pathogens that cause gastroenteritis may also cause septicaemia, such as Salmonella and Shigella.

Respiratory examination of the infant with fever, cough and vomiting may identify tachypnoea and grunt that alert the clinician to the possibility of pneumonia. Grunting is an expiratory noise, usually intermittent, and generates PEEP (positive end expiratory pressure) by partially closing the glottis during expiration. Percussion note for dullness may be more valuable than auscultation for crackles or bronchial breathing. Be aware of the child with abdominal pain and grunt as they may have a lower lobe pneumonia.

Abdominal examination

The abdomen is examined for distension, tenderness and guarding. Take note of the child’s resting posture and how they move spontaneously or on request, both in the bed or walking. A gentle, unrushed examination provides more information.

Presence of guarding and rebound can be elicited with gentle flexion/relaxation of the fingers of the examining hand (at the metacarpophalangeal joint). Evaluate for organomegaly – liver, spleen and kidneys. Are there any masses? The pale, vomiting child may have intussusception. Examine for anal fissures and other perianal abnormality that may indicate inflammatory bowel disease.

Neurological examination

The child may have impaired consciousness either due to systemic illness, shock or a primary neurological problem. The unwell infant who is vomiting may have meningitis. Likewise, raised intracranial pressure (ICP) may cause vomiting. Cushing’s triad includes bradycardia, hypertension and abnormal respiration, but is generally associated with a marked elevation of the ICP. On neurological examination, check for any asymmetry of movement, tone and reflexes, as a cerebral abscess may cause fever and vomiting. Focal seizures generally indicate focal pathology and should be considered the same as a focal abnormality on examination.

Temperature

Always measure the temperature of the vomiting child. If the child’s circulation is compromised then consider continually monitoring the temperature with a rectal probe. The body’s temperature varies over time, and in the unwell patient it is crucial to continue to monitor for fever over a period of time. Remember that some modes of measurement underestimate the core temperature or are an inaccurate reflection of the core temperature (see above). The child with overwhelming sepsis may not mount a fever and, indeed, may be hypothermic.

Differential diagnoses

This list is extensive and varies depending upon the combination of symptoms, vomiting and/or fever and/or diarrhoea, as well as the examination findings:

• gastro-oesophageal reflux;

• viral illness;

gastritis/enteritis;

non-specific, generalised viral illnesses;

• gastroenteritis – viral, bacterial;

• otitis media/URTI/tonsillitis/pharyngitis/stomatitis;

• urinary tract infection (UTI);

• septicaemia;

• meningitis/encephalitis;

• appendicitis;

• metabolic/endocrine problems;

• intestinal obstruction including malrotation (± volvulus);

• cyclical vomiting;

• malabsorption including cows’ milk protein enteropathy;

• colitis (including Crohn’s disease, ulcerative colitis, pseudomembranous colitis).

The child with recurrent vomiting warrants particular attention, with consideration of diagnoses like malrotation, UTIs and cyclical vomiting. An abdominal X-ray may be helpful, but after surgical consultation an upper gastrointestinal contrast study may be required. A child thought to have cyclical vomiting should be referred to a paediatrician for follow up. Beware of children with a pre-existing condition (or ‘label’) such as cyclical vomiting as they may develop other acute conditions. These children require careful reconsideration at each presentation before concluding ‘another vomiting episode’.

Investigations

Remember, only order tests that aid the decision making and management of the patient. Reference ranges are frequently based on the standard deviation in a population, so a result outside the range may not necessarily indicate abnormality or pathology. This may inadvertently lead the clinician to order more unnecessary tests.

Not every child who is medically assessed requires investigations. The tests required depend on the possible differential diagnoses and the severity of illness (Table 7.8.1). Don’t forget simple bedside tests like urine analysis (UA) and blood glucose. This information can be invaluable in assessing the child with diarrhoea and vomiting. In this context, check the specific gravity and for ketones. Glycosuria may indicate diabetic ketoacidosis. If the UA is positive for nitrites or leucocytes, then an appropriately collected urine specimen should be cultured. The specimen to be cultured should be collected attempting to minimise contamination, even if re-collection is required.

Common tests:

• Urine analysis

• Urine culture

Microscopy, culture

Rotavirus antigen

Giardia (often tested by RIA, avoiding the need for multiple samples for ova and parasites)

• Biochemistry – electrolytes, urea/creatinine, blood glucose

• Full blood count

Less common tests:

• Liver function tests

• Blood gas (venous or arterial)

• Blood culture

• Insulin, growth hormone, cortisol (if hypoglycaemic)

• Urine metabolic screen

• CXR to exclude pneumonia

• AXR to exclude intestinal obstruction

AXR, abdominal X-ray; CXR, chest X-ray; RIA, radioimmunoassay.

Generally urine culture is unnecessary where acute gastroenteritis is likely (i.e. when there is diarrhoea) but is mandatory in the infant or baby with acute vomiting and fever. Urinary symptoms like dysuria and frequency can be expected in children from about 4 or 5 years of age, allowing a more selective approach to those who require urine culture. ‘Bag urines’ (collected in an adhesive, sterile plastic bag) have a high contamination rate and are best avoided when performing a urine culture, but are satisfactory for a simple UA. Although more difficult to collect, a ‘clean catch urine’ provides a sample less likely to be contaminated. This is collected with an open nappy, a poised parent, with an open sterile container, waiting patiently to ‘catch’ the spontaneously voided urine. Those babies and infants deemed to be at higher risk of a UTI or who are more seriously unwell may require more rapid testing by either a suprapubic aspirate (‘bladder tap’) or an in–out catheter urine collection. Any child who is toilet trained and requires a urine culture should have mid-stream urine collected.

The child who is previously well and thriving who presents with vomiting and hypoglycaemia, if ketotic, is likely to be hypoglycaemic from starvation. In the absence of ketonuria, metabolic and endocrine abnormalities need to be considered. It may be necessary to assay growth hormone, insulin and cortisol, as well as performing a urine metabolic screen. Collecting appropriate specimens when hypoglycaemic is important. Blood samples collected in a lithium heparin tube (plasma) and plain tube (serum) should allow blood glucose to be measured concurrently with hormone levels. Other samples may also be needed. Consultation with a paediatrician or paediatric endocrinologist may be prudent.

In a young, breastfed infant with blood in vomitus or stool it is important to distinguish swallowed maternal blood from infant’s blood. An Apt test distinguishes between the two due to presence of HbF. To perform the test, add the bloody stool/vomitus to a test tube with about 5 mL of tap water. This lyses the red blood cells. After allowing to settle, the “supernatant” should be pink to continue. If so, add 1 mL of 1% sodium hydroxide. Remaining pink indicates infant’s blood (HbF) whereas changing to a yellow-brown colour over 2 minutes indicates maternal (adult) blood.

The microscopy of the diarrhoeal stool may be important. The presence of stool white cells, without a viral or bacterial pathogen, in the young infant, may indicate cows’ milk protein intolerance.

Management

Intravenous fluids

• Rehydration.

The management will depend on the need for immediate resuscitation and subsequently, the provisional diagnosis. A fluid bolus is used to restore circulating volume and is therefore warranted when signs of shock are present. This must not be confused with strategies of ‘rapid rehydration’ in dehydrated children. Intravenous fluids containing dextrose must not be used as volume expanders. The choice of crystalloid fluid for a bolus is either normal saline (0.9%) or Hartmann’s solution. If these crystalloids are not available, and a bolus is required, then a colloid should be used (e.g. 4% NSA or Gelofusine).

In dehydrated, but not cardiovascular compromised children, it is safer to commence initial intravenous rehydration with fluids that contain at least 75 mmol L^–1 sodium, i.e. 0.45–0.9% NaCl solution. Commonly available fluids include 0.45% NaCl + 5% glucose, 0.9% NaCl (normal saline) and Hartmann’s solution. Normal saline (0.9% NaCl) with 5% glucose is also currently available. Hypoglycaemia is not infrequent, both at presentation or subsequently, thus dextrose-containing fluids are appropriate in all children, particularly in the young infant or those who have had insufficient caloric intake and are ketotic. Intravenous fluids are commonly manufactured as ‘isotonic’ with plasma, by varying the glucose concentration to balance the sodium chloride (e.g. 0.45% NaCl + 5% glucose). The addition of dextrose to many commercially available solutions (such as normal saline) makes them ‘hypertonic’ compared to plasma. However, due to rapid equilibration of the dextrose with extravascular space this is not clinically significant. In this context, 0.9% NaCl + 2.5% glucose is an appropriate intravenous fluid to use (may be made by adding 50 mL of 50% glucose to 450 mL of 0.9% NaCl).

Be aware of the potential of SIADH in unwell children. The rate of fluid administration may need to be altered depending upon the initial biochemistry, the diagnosis and the clinical progress of the child. Monitoring fluid balance is essential in the unwell infant or child.

Nasogastric rehydration is commonly used in dehydrated infants with gastroenteritis. See Chapter 7.12.

Antibiotics

Any specific management like administration of antibiotics depends on the provisional diagnosis, and the severity of illness. Most acute diarrhoeal illnesses are viral and self-limiting and therefore do not require antibiotics. Clearly it is preferable that appropriate cultures be taken prior to administration of antibiotics, although in the severely unwell, febrile patient broad-spectrum antibiotics should not be delayed whilst awaiting collection of all cultures. It would be preferable, but not essential, that a blood culture be undertaken prior to such administration.

Consultation

Consultation with more experienced staff, either emergency physicians or paediatricians should be encouraged, especially for complex or severely ill infants or children. Assistance may be required for clinical evaluation and technical procedures in critically ill children.

Transfer

Local experienced senior clinical consultation and review should occur prior to transfer. The child who requires transfer to a facility that provides a higher level of care needs an experienced evaluation regarding the level of escort, urgency and mode of transport required to safely achieve the transfer.

Conclusions

Differential diagnostic possibilities

For each patient the differential diagnoses vary depending on the constellation of symptoms (fever, vomiting, diarrhoea or others). Keep an open mind and always re-evaluate clinical data. Don’t be distracted by a child’s previous diagnoses or labels.

General approach

‘ABC fluids in and out’ is a useful tool in taking a history. Caution must be exercised in the infant who has fever and vomiting, as differential diagnoses include serious illnesses, like meningitis. The younger the infant, the more challenging the evaluation and the less reliable the clinical examination. If in doubt, seek consultation from a colleague. The telephone is a useful and powerful tool for clinicians and the value of consultation should not be underestimated.

Further reading

Craig J.V., Lancaster G.A., Taylor S., et al. Infrared ear thermometry compared with rectal thermometry in children: a systematic review. Lancet. 2002;360(9333):603-609. [Review; 48 refs]

Craver R.D., Abermanis J.G. Dipstick only urinalysis screen for the pediatric emergency room. Paediatr Nephrol. 1998;11(3):331-333. [1998 erratum appears in Paediatr Nephrol 12(5): 426]

Gorelick M.H., Shaw K.N. Screening tests for urinary tract infection in children: a meta-analysis. Pediatrics. 1999;104(5):54.

Gorelick M.H., Shaw K.N., Baker M.D. Effect of ambient temperature on capillary refill in healthy children. Paediatrics. 1993;92(5):699-702.

Hewson P.H., Gollan R.A. A simple hospital triaging system for infants with acute illness. J Paediatr Child Health. 1995;31(1):29-32.

Neville K.A., Verge C.F., O’Meara M.W., Walker J.L. High antidiuretic hormone levels and hyponatremia in children with gastroenteritis. Pediatrics. 2005;116(6):1401-1407.

Neville K.A., Verge C.F., Rosenberg A.R., et al. Isotonic is better than hypotonic saline for intravenous rehydration of children with gastroenteritis: a prospective randomised study. Arch Dis Child. 2006;91(3):226-232.

Shaw K.N., McGowan K.L., Gorelick M.H., Schwartz J.S. Screening for urinary tract infection in infants in the ED: which test is best? Paediatrics. 1998;101(6):E1.

Related

Textbook of Paediatric Emergency Medicine