Paediatrics chapters
Acute diarrhoea and dehydration
How to define acute diarrhoea, which organisms cause it, how to grade dehydration at the bedside, and how to treat it with low-osmolarity ORS, zinc and the WHO Plans A, B and C.
- Acute diarrhoea is three or more loose or watery stools in 24 hours (or one watery stool), lasting under 14 days; rotavirus is the leading cause in young children and spread is faeco-oral.
- Dehydration is graded no, some or severe using general condition, sunken eyes, thirst/ability to drink and skin pinch; it decides Plan A, B or C.
- Treatment is low-osmolarity ORS (245 mOsm/L, Na 75 mmol/L), zinc for 10 to 14 days, continued feeding, and IV Ringer lactate 100 mL/kg for severe dehydration; antibiotics only for dysentery, cholera or proven infection.
On this page
Overview
Acute diarrhoea is one of the commonest reasons a child is brought to hospital in Pakistan and a leading cause of death under 5 years. Most deaths come from dehydration and electrolyte loss, not from the organism itself. The cornerstones of care are simple: assess dehydration, rehydrate with ORS or IV fluids, give zinc, keep feeding, and use antibiotics only for clear indications.
Definition
- Diarrhoea: passage of three or more loose or watery stools in 24 hours, softer than the child's usual stool, or even one watery stool (Akbar).
- Nelson gives a physiological definition: stool water loss of more than 10 mL/kg/day.
- Acute diarrhoea lasts less than 14 days. If an infective episode lasts more than 14 days it is persistent diarrhoea; chronic diarrhoea (usually non-infective) is covered in its own chapter.
- Dysentery means diarrhoea with visible blood, usually with mucus and fever.
Breastfed babies normally pass frequent soft stools. Frequency alone is not diarrhoea; a change in consistency is what matters.
Epidemiology (Akbar)
- About 3 to 4 episodes per child per year; the peak is in the first year of life.
- Accounts for 40 to 50% of hospital admissions in the summer and rainy season in our setting.
- Spread is mainly faeco-oral through contaminated food and water. Some organisms (Shigella, E. coli O157:H7, Giardia, enteric viruses) need only a small inoculum and spread from person to person.
Risk factors
- No breastfeeding
- Unsafe water, poor sanitation, contaminated food
- Malnutrition and measles
- Low maternal education
Causes and common pathogens
| Group | Organisms | Notes |
|---|---|---|
| Viruses | Rotavirus (about 40% in Akbar), norovirus, astrovirus, enteric adenovirus 40/41 | Watery stool, no blood; vomiting common; winter peak for rotavirus |
| Bacteria | E. coli (about 25%): enterotoxigenic, enteropathogenic, enteroinvasive, enterohaemorrhagic O157:H7; Salmonella; Shigella; Vibrio cholerae; Campylobacter; Yersinia; S. aureus (food poisoning) | ETEC is the main cause of traveller's diarrhoea; EHEC causes haemolytic uraemic syndrome |
| Parasites | Entamoeba histolytica, Giardia lamblia, Cryptosporidium | Giardia: greasy, foul stool, bloating; Cryptosporidium severe in AIDS |
| Non-infective | Otitis media, pneumonia, UTI ("parenteral" diarrhoea), overfeeding, food allergy, antibiotics | Treat the underlying cause |
Mechanisms worth knowing
| Mechanism | Example | Key point |
|---|---|---|
| Secretory (toxin) | Cholera toxin and ETEC heat-labile toxin raise cyclic AMP; ETEC heat-stable toxin raises cyclic GMP | Glucose-linked sodium absorption stays intact, which is why ORS works |
| Invasive | Shigella, enteroinvasive E. coli, Campylobacter, amoebiasis | Fever, cramps, tenesmus, small bloody mucoid stools with pus cells |
| Mucosal damage / osmotic | Rotavirus | Loss of brush-border disaccharidases gives temporary lactose intolerance |
Cholera toxin binds the GM1 ganglioside receptor and switches on adenylate cyclase. Stools are rice-water and very large in volume.
Assessment
History
- Duration, number and consistency of stools; blood or mucus
- Vomiting, fever, urine passed in the last 6 hours
- Feeding (breastfeeding, dilution of formula, bottle hygiene)
- Drugs already given (antibiotics, antidiarrhoeals, ORS)
- Associated illness: cough, measles rash, urinary symptoms; contact history
Grading dehydration (WHO / IMNCI, as in Akbar)
| Sign | No dehydration | Some dehydration (2 or more signs) | Severe dehydration (2 or more signs) |
|---|---|---|---|
| General condition | Well, alert | Restless, irritable | Lethargic or unconscious |
| Eyes | Normal | Sunken | Sunken |
| Drinking | Normal | Drinks eagerly, thirsty | Not able to drink or drinks poorly |
| Skin pinch (abdomen) | Goes back quickly | Goes back slowly | Goes back very slowly (over 2 seconds) |
| Treatment | Plan A | Plan B | Plan C |
Weight-loss estimate
| Grade | Akbar (percentage of body weight) | Nelson (infant / adolescent) |
|---|---|---|
| Mild | Under 5% | 5% / 3% |
| Moderate | 5 to 10% | 10% / 6% |
| Severe | Over 10% | 15% / 9% |
Nelson adds that tachycardia, weak pulses, delayed capillary refill, oliguria and then hypotension mark worsening dehydration; low blood pressure means shock.
In hypernatraemic dehydration water moves out of cells into the blood, so the circulation is protected and the child looks less dry than they are. The degree of dehydration is easily underestimated.
Types by serum sodium (Akbar)
| Type | Serum sodium | Share of cases |
|---|---|---|
| Isotonic | 130 to 150 mmol/L | About 70% |
| Hypotonic | Below 130 mmol/L | About 20% |
| Hypertonic | Above 150 mmol/L | About 10% |
Investigations
Most children with watery diarrhoea need no tests. Investigate if severely dehydrated, bloody, prolonged or unusual.
| Test | Use |
|---|---|
| Serum electrolytes, urea, creatinine | Severe dehydration, IV fluids, suspected hypernatraemia or kidney injury; urea rises more than creatinine in simple volume loss |
| Stool microscopy | Pus cells and red cells (invasive organisms); cysts or trophozoites of Giardia and amoeba |
| Stool pH and reducing substances | Acidic stool with reducing substances suggests sugar (lactose) intolerance |
| Stool culture | Dysentery, high fever, suspected cholera, outbreaks |
| Rotavirus antigen (ELISA) | Confirms rotavirus, especially in winter |
| Blood culture | Suspected typhoid or bacteraemia (Salmonella, Shigella) |
| Urine examination, chest X-ray | Look for "parenteral" causes (UTI, pneumonia) |
Management
Low-osmolarity ORS
| Ingredient | g/L | Component | mmol/L |
|---|---|---|---|
| Sodium chloride | 2.6 | Sodium | 75 |
| Glucose (anhydrous) | 13.5 | Chloride | 65 |
| Potassium chloride | 1.5 | Glucose | 75 |
| Trisodium citrate dihydrate | 2.9 | Potassium | 20 |
| Total weight | 20.5 | Citrate | 10 |
| Total osmolarity | 245 mOsm/L |
- Glucose helps sodium (and so water) absorption through the intact sodium-glucose co-transporter.
- Potassium prevents hypokalaemia; citrate corrects acidosis.
- Mix in clean water, do not boil after mixing, and make a new solution each day. Give by cup and spoon, frequent sips, or nasogastric tube.
- Park notes that the reduced-osmolarity formula cut stool output by about 20%, vomiting by about 30% and the need for unplanned IV fluids by about a third compared with the old ORS.
"75-65-75-20-10 = 245": sodium, chloride, glucose, potassium, citrate, total.
Plan A: no dehydration (treat at home)
Three home rules: give extra fluid, continue feeding, know when to return.
- Extra fluid after each loose stool:
| Age | ORS after each loose stool |
|---|---|
| Under 2 years | 50 to 100 mL |
| 2 years and over | 100 to 200 mL |
- Breastfeed more often and for longer; give ORS, clean water or home fluids (soup, rice water, lassi/yoghurt drink).
- Give the mother 2 packets of ORS to use at home; small frequent sips; if the child vomits, wait 10 minutes then continue slowly.
- Zinc (see below) and continued feeding.
- Return immediately if the child cannot drink or breastfeed, gets sicker, develops fever, has blood in stool or drinks poorly; otherwise follow up after 5 days.
Plan B: some dehydration (ORS in the clinic over 4 hours)
| Age | Weight | ORS in first 4 hours |
|---|---|---|
| Up to 4 months | Under 6 kg | 200 to 400 mL |
| 4 to 12 months | 6 to under 10 kg | 400 to 700 mL |
| 12 months to 2 years | 10 to under 12 kg | 700 to 900 mL |
| 2 to 5 years | 12 to 19 kg | 900 to 1400 mL |
- Rough rule: ORS (mL) = weight (kg) × 75. Use age only if weight is not known. Give more if the child wants more.
- Non-breastfed infants under 6 months also get 100 to 200 mL clean water in this period.
- Reassess after 4 hours and choose Plan A, B or C again.
An 8 kg infant has some dehydration.
ORS in 4 hours = 8 × 75 = 600 mL
This fits the table range for 6 to under 10 kg (400 to 700 mL).
Plan C: severe dehydration (IV fluids now)
Give 100 mL/kg of Ringer lactate (normal saline if Ringer lactate is not available):
| Age | First 30 mL/kg in | Then 70 mL/kg in |
|---|---|---|
| Infants under 12 months | 1 hour | 5 hours |
| Children 12 months to 5 years | 30 minutes | 2½ hours |
- Repeat the first 30 mL/kg once if the radial pulse is still very weak or absent.
- Reassess every 1 to 2 hours; start ORS about 5 mL/kg/hour as soon as the child can drink (usually after 3 to 4 hours in infants, 1 to 2 hours in children).
- At the end of the course (about 6 hours for an infant, 3 hours for a child, as given in Park), classify again and choose the next plan.
- If IV access is impossible and the worker is trained: ORS by nasogastric tube 20 mL/kg/hour for 6 hours (total 120 mL/kg).
- Akbar adds that a shocked child may first get 20 mL/kg pushed over 10 to 15 minutes, repeated if pulses stay weak.
An 8 kg infant with severe dehydration.
First 30 mL/kg = 30 × 8 = 240 mL in 1 hour
Then 70 mL/kg = 70 × 8 = 560 mL over 5 hours
Total = 800 mL (100 mL/kg) in 6 hours
The time split is 1 hour + 5 hours for infants but 30 minutes + 2½ hours for children aged 1 to 5. Examiners swap these.
Fluid deficit (Nelson)
Deficit (litres) = percentage dehydration × body weight (kg). After the bolus, plan maintenance + deficit over 24 hours and replace ongoing losses; add potassium only once the child passes urine.
A 10 kg child is 10% dehydrated.
Deficit = 10% of 10 kg = 1 kg = 1000 mL
Zinc
- Shortens the duration and severity of the episode and lowers the chance of further diarrhoea in the next 2 to 3 months (Park).
- WHO/UNICEF dose (Park): 10 mg/day for infants under 6 months and 20 mg/day for older children, for 10 to 14 days. Akbar gives 20 mg/day for children over 6 months.
Feeding
- Do not starve the child. There is no benefit in resting the bowel.
- Continue breastfeeding; restart the usual diet after rehydration with fresh, energy-dense food 4 to 6 times a day; banana or fresh juice adds potassium.
Drugs
| Drug | Use |
|---|---|
| Antibiotics | Only for dysentery (Shigella), suspected cholera with severe dehydration, proven Giardia or amoebiasis, typhoid, or sepsis |
| Antidiarrhoeals / antimotility drugs | Not recommended in children |
| Antiemetic (ondansetron) | Nelson: may help persistent vomiting and improve ORS tolerance |
| Steroids, kaolin, charcoal | No value (Park) |
Most acute watery diarrhoea is viral; giving antibiotics routinely does not help and is a common wrong option.
Hypernatraemic dehydration
- The most dangerous type: water leaves brain cells, which shrink; bridging vessels may tear, causing bleeding and thrombosis.
- The child is lethargic but irritable, with fever, increased tone, brisk reflexes and seizures; skin may feel doughy.
- Brain cells make idiogenic osmoles to protect themselves. If sodium is lowered too fast, water rushes into brain cells, causing cerebral oedema, seizures and death.
- Correct slowly: sodium should fall by no more than 12 mmol/L in 24 hours; the deficit is corrected over 2 to 4 days. Start with normal saline, then 5% dextrose in half-normal saline, with close sodium monitoring.
The choice of fluid matters less than frequent sodium checks and slowing down if sodium drops too quickly.
Complications
- Dehydration and hypovolaemic shock
- Metabolic acidosis (deep, sighing breathing)
- Hypokalaemia with abdominal distension and paralytic ileus
- Seizures (hypernatraemia, hypoglycaemia, cerebral venous thrombosis)
- Acute kidney injury
- Persistent diarrhoea from secondary disaccharidase deficiency; malnutrition
- Haemolytic uraemic syndrome (EHEC, Shigella)
Prevention
- Exclusive breastfeeding for the first 6 months, then good complementary feeding
- Safe water, sanitation, hand washing with soap, food hygiene
- Rotavirus vaccine and measles vaccine (measles can trigger severe diarrhoea)
- Vitamin A supplementation where deficiency is common
- Early case management with ORS and zinc (IMNCI)
Pakistan's EPI includes rotavirus vaccine; schedules can change, so check the current national EPI guidance.
Expect: the definition (three or more loose stools or one watery stool; persistent if over 14 days); rotavirus as the commonest cause; cholera toxin and cyclic AMP; the four signs used to grade no, some and severe dehydration; low-osmolarity ORS composition (sodium 75, total 245); Plan A fluids after each stool; Plan B 75 mL/kg over 4 hours; Plan C 100 mL/kg Ringer lactate with the infant and child time splits; zinc dose and duration; slow correction of hypernatraemia (no more than 12 mmol/L per day); and the fact that antidiarrhoeals and routine antibiotics are not used.
Quick revision
- Diarrhoea: 3 or more loose stools a day or one watery stool; acute under 14 days.
- Rotavirus is the main cause; spread faeco-oral.
- Grade with general condition, eyes, thirst, skin pinch: no, some, severe.
- ORS: Na 75, Cl 65, glucose 75, K 20, citrate 10, total 245 mOsm/L.
- Plan B: 75 mL/kg in 4 hours; Plan C: 100 mL/kg Ringer lactate (infant 1 h + 5 h; child 30 min + 2½ h).
- Zinc 10 mg (under 6 months) or 20 mg for 10 to 14 days.
- Keep feeding; no antidiarrhoeals; antibiotics only for dysentery, cholera, parasites, typhoid.
- Hypernatraemia: correct over 2 to 4 days, sodium fall no more than 12 mmol/L per 24 h.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics; Park's Preventive and Social Medicine).
FAQ
What is the sodium content of low-osmolarity ORS?
It contains 75 mmol/L of sodium, with a total osmolarity of 245 mOsm/L.
How much ORS is given in Plan B?
About 75 mL/kg over 4 hours, then the child is reassessed and the plan chosen again.
Why do we not use antidiarrhoeal drugs in children?
They do not reduce fluid loss, can cause serious side effects and may hide worsening illness; ORS, zinc and feeding are the effective treatments.
Why is zinc given for 10 to 14 days?
It shortens the current episode, reduces its severity and lowers the risk of further diarrhoea over the next few months.