Gastroenteritis

Gastroenteritis

1. differential diagnoses

   • infection
     • systemic
       • septicaemia
       • meningitis
     • local
       • resp tract infection
       • otitis media
       • hepatitis A
       • UTI
   • surgical disorders
     • pyloric stenosis
     • intussusception
     • acute appendicitis
     • necrotising enterocolitis
     • Hirschsprung disease
   • metabolic disorder
     • diabetic ketoacidosis
   • renal disorder
     • haemolytic uraemic syn
   • other
     • coeliac disease
     • cow's milk protein intolerance
     • adrenal insufficiency

2. epidemiology

   • developing countries
     • major cause of child mortality
   • developing countries
     • major cause of child morbidity
     • UK
       • 10% of 5 yr olds annually

3. causes

   • viral
     • rotavirus
       • commonest cause in developed countries
       • accounts for 60% of cases in <2 yr olds
       • effective vaccine available
         • not part of national immunisation programme
     • cause outbreaks
       • adenovirus
       • norovirus
       • calicivirus
       • coronavirus
       • astrovirus
   • bacterial
     • less common in developed countries
       • Campylobacter jejuni
         • commonest bacterial infection in developed countries
         • assoc w/ severe abdo pain
       • Shigella, some Salmonella spp.
         • dysentry
         • blood and pus in stool
         • pain
         • tenesmus
         • Shigella may be acc by high fever
     • blood in stool
     • clinical features are poor guide to the pathogen
     • cholera and enterotoxic E. coli
       • profuse, rapidly dehydrating diarrhoea

4. clinical features

   • sudden change to loose or watery stools
     • often + vomiting
   • contact w/ a person w/ diarrhoea
   • recent travel abroad

5. complication

   • dehydration
     • increased risk of dehydration in
       • infants
         • esp < 6months old or born w/ low birth weight
         • at greater risk than older kids
           • infants have higher surface area:weight
             • -> greater insensible losses
           • infants have higher basal fluid requirements
             • 10-12% of body weight
           • infants have immature renal tubular absorption
           • infants can't get fluid for themselves when thirsty
       • children passed 6 or more diarrhoeal stools in prev 24 hours
       • children vomited 3 or more times in prev 24h
       • children unable to tolerate (or not been offered extra fluids)
       • children w/ malnutrition
     • Rx aims to prevent or correct this
     • -> shock
     • types
       • isonatraemic
         • loss of water and Na+ are proportional
           • so plasma Na+ within normal range
       • hyponatraemic
         • when kids w/ diarrhoea drink large amounts of water or other hypotonic sols
           • -> greater net loss of Na+ than water
             • -> fall in plasma Na+
               • -> water shifting from extracellular to intracellular comp
                 • -> increase in brain vol
                   • ->convulsions
                 • greater degree of shock per unit of water loss
                   • due to marked extracellular depletion
         • more common in poorly nourished infants in developing countries
       • hypernatraemic
         • infrequent
         • water loss exceeds relative Na+ loss
           • plasma [Na+] increases
             • usually results from high insensible water losses
               • high fever or hot dry env
             • can result from profuse low Na+ diarrhoea
             • extracellular fluid becomes hypertonic vs intracellular fluid
               • -> shift of water into extracellular space from intracellular
         • signs of fluid depletion less obvious
           • so hard to recognise this type of dehydration clinically
             • esp in obese infants
         • dangerous form of dehydration
           • water is drawn out of brain
             • cerebral shrinkage within a rigid skull ->
               • jittery movements
               • increased muscle tone
                 • with hyperreflexia
               • altered consciousness
               • seizures
               • multiple, small cerebral haemorrhages
               • transient hyperglycaemia
                 • self-correcting
                 • no need for insulin
     • total body deficit of Na+ & water

6. Mx

   • assessment of dehydration
     • degree of weight loss during diarrhoeal illness
       • most accurate measure of dehydration
     • use hx and examination
       • degree of dehydration
         • no clinically detectable dehydration
           • usually 5% loss of body weight
         • clinical dehydration (usually 5-10%)
         • shock
           • > 10% loss of body weight
           • clinical features
             • decreased levels of consciousness
             • sunken fontanelle
             • dry mucous mbs
             • eyes sunken and tearless
             • pale mottled skin
             • increased resp rate
             • prolonged capillary refill time (> 2 secs)
             • increased heart rate
             • weak peripheral pulses
             • hypotension
             • reduced skin turgor
             • sudden weight loss
             • cold extremities
             • reduced urine output