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Level 2 of 6Must-remember

Acute diarrhoea and dehydration

Assess, manage and stay safe — enough on its own

The card — assess, manage, caution

Assessment— look, ask, measure

  • Three questions drive everything: how depleted is the patient, can they drink, and does the stool contain blood? The first sets the rate of fluid, the second the route, the third whether antimicrobials are considered and antimotility drugs forbidden.
  • Take the history in this order: duration; stool character (watery, bloody, mucoid, rice-water); number of stools in 24 hours; associated symptoms; exposures (food, travel, antibiotics, hospitalisation, residential care, contacts, animals, immunosuppression); and the time and volume of the last urine passed — the single most useful item for judging the deficit.
  • Count the losses rather than estimating them: each stool represents roughly 200 mL of isotonic fluid, so six to ten stools daily for 48 hours leaves an adult 2–4 litres depleted before any assessment is made; fever adds 200 mL/day per degree Celsius; and in cholera losses reach 1 litre per hour and 10–20 litres per day, enough to empty the adult circulation in under three hours.
  • Decide non-inflammatory versus inflammatory in the first minutes. Non-inflammatory (watery, small-bowel) disease gives periumbilical cramp, nausea, vomiting and voluminous watery stool without blood, with absent or low-grade fever. Inflammatory (dysenteric, colonic) disease gives fever, lower abdominal cramp, urgency, tenesmus and frequent small-volume stools with blood and mucus, volume typically under 1 L/day.
  • Grade the dehydration by the WHO scheme, in which a single severe sign classifies the patient as severe — the categories are not additive scores: none or mild is under 5% of body weight, some or moderate is 5–9%, severe is 10% or more.
  • Look in a fixed order: conscious level, thirst, the eyes, moistness of tongue and mucosae, skin turgor over the abdomen or forearm, radial pulse rate and volume, capillary refill, blood pressure lying and sitting, urine output. Acute change in body weight is the most honest measure of deficit and the best proof that treatment is working.
  • Severe dehydration is: lethargic, drowsy or unconscious; drinks poorly or unable to drink; deeply sunken eyes; a very dry parched tongue; a skin pinch that retracts very slowly (more than 2 seconds — tenting); a weak, thready or absent radial pulse; hypotension; capillary refill over 3 seconds with cold peripheries; and minimal or no urine.
  • In children look for sunken eyes, absent tears on crying, a sunken anterior fontanelle, a dry tongue, a slowly retracting skin pinch, capillary refill over 3 seconds, lethargy or inconsolable irritability, and dry nappies for more than 6 hours. The behavioural sign is near-diagnostic: a child who drinks eagerly and thirstily has some dehydration; one who drinks poorly or cannot drink has severe dehydration.
  • Check a bedside glucose in any lethargic child — hypoglycaemia is common and a frequent cause of convulsion, and remember that children and fit young adults hold systolic pressure until depletion is profound then decompensate abruptly, so a normal blood pressure is not reassurance here.
  • In older patients decompensation occurs at smaller deficits, with less fever and loss of the thirst response; skin turgor is unreliable because elasticity is already reduced, and mucosal dryness is confounded by mouth-breathing and anticholinergics. Diarrhoea in an older patient is frequently a symptom of disease elsewhere — urinary or chest infection, drug toxicity, faecal impaction.
  • Recognise the features that indicate serious illness: fever above 38.5 °C; bloody stool; six or more unformed stools in 24 hours; profuse watery diarrhoea with dehydration; severe abdominal pain, particularly over 50; white cell count 15 × 10⁹/L or more; no improvement by 48 hours; recent antibiotic exposure, hospitalisation of 3 days or more or residential care; age ≥ 70 or frailty; immunocompromise; sepsis; a known outbreak.
  • Act immediately on these danger signs: absent or thready radial pulse, hypotension, cold mottled peripheries (hypovolaemic shock); reduced conscious level (a circulatory sign until proved otherwise, and a bar to oral rehydration); Kussmaul respiration (severe acidosis); anuria or oliguria persisting despite adequate volume replacement; falling haemoglobin and platelets with bloody diarrhoea (haemolytic uraemic syndrome); distension, silent abdomen, fever and tachycardia (toxic megacolon) or peritonism (perforation); potassium below 2.5 or above 6.0 mmol/L or any new arrhythmia; hypoglycaemia or convulsion in a small child.Not available at your setup — Serum electrolytes.
  • Use the incubation period, the most efficient discriminator available at the bedside: 1–8 hours with vomiting dominant suggests *Staphylococcus aureus* or *Bacillus cereus* (emetic, classically reheated rice); 6–16 hours with diarrhoea dominant suggests *Clostridium perfringens* or *B. cereus* diarrhoeal toxin; 12–48 hours suggests norovirus (24–48 h), ETEC, STEC or *Salmonella* (12–72 h); 24–72 hours suggests *Vibrio cholerae* and most invasive bacteria; 2–4 days *Campylobacter jejuni* and 3–7 days *Yersinia*; 1–2 weeks or more suggests *Giardia*, *Cryptosporidium*, *Cyclospora* or amoebiasis.
  • Know the duration bands: acute is less than 2 weeks (14 days) — over 90% infectious and usually self-limiting; persistent is 2–4 weeks; chronic is beyond 4 weeks and is not infectious at all. Diarrhoea persisting beyond 14 days is not attributable to a bacterial enteric pathogen except for *Clostridioides difficile*.
  • Separate the three impostors of diarrhoea: pseudodiarrhoea (frequent small volumes of formed stool with urgency), faecal incontinence, and overflow diarrhoea around impacted faeces, missed in the frail unless the rectum is examined — true diarrhoea is stool weight above 200 g per day in an adult on a typical Western diet.
  • Consider the non-infectious causes deliberately: drugs (magnesium salts, laxatives, metformin, SSRIs, GLP-1 agonists, colchicine, NSAIDs, chemotherapy), a first presentation of inflammatory bowel disease, ischaemic colitis, thyrotoxicosis, faecal impaction with overflow — and acute food allergy, which can present with diarrhoea and circulatory collapse that must not be mistaken for hypovolaemia.

Management— do this, in order

  • Severe dehydration or shock is treated intravenously, immediately: 100 mL/kg of balanced crystalloid over 3 hours, given as 30 mL/kg over the first 30 minutes then 70 mL/kg over the next 2½ hours; in infants under 12 months the same 100 mL/kg goes in more slowly — 30 mL/kg over 1 hour, then 70 mL/kg over 5 hours.Doctor / Nurse
  • Ringer's lactate (Hartmann's) is the fluid of choice, because lactate is metabolised to bicarbonate and helps correct the acidosis, whereas 0.9% sodium chloride adds a chloride load.
  • Reassess the radial pulse at 15 and 30 minutes, and if it remains weak or absent at 30 minutes, repeat the 30 mL/kg bolus. In a frankly shocked child give 20 mL/kg as a rapid bolus, reassess, and repeat once.Doctor / Nurse
  • Begin oral rehydration solution alongside the infusion as soon as the patient can drink safely — running both is correct, because the gut absorbs glucose-coupled sodium even while secreting.
  • Some (moderate) dehydration: ORS 75 mL/kg orally over 4 hours in small volumes given often, plus continuing losses, reassessed at 4 hours. Cannulation is not required because the patient looks unwell — if they can drink, ORS is as effective and safer. If vomiting defeats oral intake, ORS by nasogastric tube at 20 mL/kg/hour is preferable to intravenous fluid in a patient who is not shocked.
  • No or mild dehydration: give ORS for ongoing losses only — about 200 mL after every diarrhoeal stool in an adult (children 50–100 mL under 2 years, 100–200 mL from 2 to 10 years) — and continue normal food, with oral fluids overall at 50–100 mL/kg over 24 hours.
  • Prescribe ongoing losses explicitly, not as "encourage fluids": the order should read maintenance fluid plus 200 mL ORS (or an equal volume of Ringer's lactate) for every subsequent diarrhoeal stool and vomit.
  • Use the reduced-osmolarity WHO/UNICEF formula, 245 mOsm/L: sodium 75 mmol/L, chloride 65 mmol/L, anhydrous glucose 75 mmol/L, potassium 20 mmol/L, citrate 10 mmol/L, which outperforms the older 311 mOsm/L formula on stool output, vomiting and the need for unscheduled intravenous fluid.
  • Where sachets are unavailable, an acceptable improvised solution is ½ teaspoon (3.5 g) of salt, 1 teaspoon (2.5 g) of sodium bicarbonate, 8 teaspoons (40 g) of sugar and 8 oz of orange juice, made up to 1 litre with clean water. Water, tea and fizzy drinks alone are inadequate — they lack the sodium and glucose for cotransport.
  • Assume hypokalaemia and replace it actively: a severely depleted adult may need at least 4 litres of isotonic fluid and 80 mmol of potassium in the first 24 hours. Do not add potassium to the resuscitation bolus; add it once urine flows. Peripheral administration should not exceed 40 mmol/L in the bag or 10 mmol/hour; faster replacement needs a central line and cardiac monitoring.Doctor / NurseNot available at your setup — Serum electrolytes.
  • Most of the acidosis corrects with volume alone, and sodium bicarbonate is not routinely indicated — consider it only in persisting acidaemia (pH below 7.1) despite adequate filling, and treat the perfusion rather than the number. Correct hypernatraemia at no more than about 10 mmol/L per 24 hours.Not available at your setup — Arterial blood gas.
  • Do not starve the gut. Soft, low-fibre, low-fat, temporarily low-lactose foods — soups, rice, bananas, toast — are better tolerated; avoid caffeine and alcohol. In infants, breastfeeding must continue uninterrupted, since breast milk reduces stool losses and the need for oral rehydration; do not dilute formula, and "bowel rest" has no place.
  • Give zinc to every child under 5: 10 mg orally daily for 10–14 days under 6 months; 20 mg daily for 10–14 days from 6 months to 5 years — it shortens childhood diarrhoea, reduces recurrence and reduces mortality in resource-limited settings.
  • Most patients should receive no antibiotic: empirical treatment of community-acquired watery diarrhoea is not indicated and may prolong carriage — such cases need ORS and, in children, zinc, and nothing else. Consider antibiotics for bloody or mucoid stool; severe, prolonged (more than 5 days) or worsening illness; sepsis; extremes of age; immunocompromise; significant dehydration; or complications — and take a stool sample before the first dose.Doctor
  • When an antibiotic is indicated: dysentery or shigellosis — ciprofloxacin 500 mg orally twice daily for 3–5 days, or azithromycin 500 mg orally daily for 3 days, or ceftriaxone 2 g IV daily if septic (children ciprofloxacin 15 mg/kg orally twice daily to a maximum 500 mg/dose; azithromycin 10–20 mg/kg orally daily to a maximum 500 mg for 3 days; ceftriaxone 50–80 mg/kg IV daily to a maximum 2 g).Doctor
  • Cholera with moderate or severe dehydration — doxycycline 300 mg orally as a single dose, or azithromycin 1 g, or ciprofloxacin 1 g orally as a single dose, or tetracycline 250 mg orally four times daily (children azithromycin 20 mg/kg orally single dose); in cholera, fluids come first, always.Doctor
  • *Clostridioides difficile*, initial episode — fidaxomicin 200 mg orally twice daily or vancomycin 125 mg orally four times daily, both for 10 days; metronidazole 400 mg orally three times daily only if neither is available (children vancomycin 10 mg/kg orally four times daily, maximum 125 mg/dose); stop the precipitating antibiotic where safe.Doctor
  • Amoebic dysentery — metronidazole 800 mg orally three times daily for 5–10 days, then a luminal agent (paromomycin 25–35 mg/kg/day in 3 doses for 7 days, or diloxanide furoate 500 mg three times daily for 10 days); children metronidazole 35–50 mg/kg/day orally in 3 doses, then a luminal agent. The luminal agent is not optional — metronidazole alone does not clear cysts.Doctor

Caution— what harms

  • Never rehydrate a drowsy or persistently vomiting patient orally — aspiration of vomitus is a rapid cause of death in profuse gastroenteritis, and a reduced conscious level is a bar to oral rehydration.
  • Never give an antibiotic for suspected STEC or haemolytic uraemic syndrome — antibiotics may increase Shiga toxin release and precipitate HUS.Doctor
  • Loperamide is contraindicated in bloody diarrhoea, fever above 38.5 °C, systemic toxicity, suspected shigellosis or *C. difficile*, and suspected toxic megacolon; in *Campylobacter* infection antimotility agents prolong symptoms and have been associated with toxic megacolon and with death. Where it is appropriate — an immunocompetent adult with watery, non-bloody diarrhoea — the dose is 4 mg orally initially, then 2 mg after each loose stool, maximum 16 mg in 24 hours, stopped immediately if diarrhoea worsens.
  • Antimotility drugs should not be given to children at all — no comfort benefit justifies the risk of ileus, megacolon and concealed fluid loss. Bismuth subsalicylate 524 mg orally four times daily is a safer adult alternative, though it blackens stool and tongue.
  • A normal blood pressure is not reassurance in a child or fit young adult, who compensates until decompensating abruptly; and individual dehydration signs perform only moderately when tested formally — no scale outperforms measured weight loss and serial reassessment.
  • Do not accept "the creatinine is high because he is dry" beyond one round of fluid: a creatinine that does not fall after adequate volume is not just dehydration — consider tubular injury or HUS.Not available at your setup — Renal function (creatinine/urea).
  • Established haemolytic uraemic syndrome reverses the fluid strategy: once haemoglobin and platelets are falling, fragmented cells are present and creatinine is rising, management becomes water restriction, discontinuation of oral rehydration solution, and avoidance of potassium-rich fluids and feeds, with transfusion and renal replacement therapy.DoctorNot available at your setup — Dialysis / renal replacement. if dialysis is unavailable, refer urgently for renal replacement therapy
  • Severe acute malnutrition changes the regimen entirely: a severely wasted or oedematous child must not receive the standard 100 mL/kg rapid rehydration — myocardial mass and function are reduced and rapid loading causes fatal heart failure. Give 10 mL/kg slowly, reassessing after each aliquot, use a low-sodium ReSoMal-type solution where available, and treat hypoglycaemia and hypothermia concurrently.Doctor / Nurse
  • Do not add potassium to the resuscitation bolus, and never exceed 40 mmol/L in the bag or 10 mmol/hour peripherally; a "normal" potassium in an acidotic patient hides a large deficit, and hypokalaemia worsens as the acidosis is corrected.Doctor / NurseNot available at your setup — Serum electrolytes.
  • Do not correct hypernatraemia faster than about 10 mmol/L per 24 hours — over-rapid correction risks cerebral oedema.Not available at your setup — Serum electrolytes.
  • Do not test formed stool for *C. difficile*, and do not repeat the test as a test of cure: toxin-positive means disease, but GDH- or PCR-positive with a negative toxin may represent colonisation — *C. difficile* is found in 5–10% of antibiotic-treated patients without diarrhoea.
  • Do not treat non-typhoidal salmonellosis routinely — antibiotics prolong carriage without shortening illness; reserve them for infants under 3 months, the immunocompromised, and bacteraemia. Assume fluoroquinolone resistance in travel-acquired infection: around 27% of *Campylobacter* isolates are ciprofloxacin-resistant, so azithromycin is the empirical agent of choice.Doctor
  • Do not diagnose inflammatory bowel disease on a biopsy taken during acute enteritis — it mimics IBD, and infective colitis, particularly *Campylobacter*, must be excluded first; and faecal calprotectin is raised in infective colitis as well as inflammatory bowel disease, so it cannot distinguish the two acutely.
  • Do not neglect infection control: use contact (enteric) precautions with hand hygiene by soap and water, since alcohol gel does not kill *C. difficile* spores; food handlers, healthcare and childcare workers should not return to work until 48 hours after the last loose stool; and cholera and case clusters are notifiable. Avoid fluoroquinolones and doxycycline in pregnancy — use azithromycin 500 mg orally once daily for 3 days or ceftriaxone 2 g IV once daily.Doctor

Refer / escalate

Escalate urgently for persistent shock after 30 mL/kg of crystalloid in an adult or 40 mL/kg in a child, stool output exceeding the infusion rate, anuria or a rising creatinine after adequate filling, falling haemoglobin and platelets with bloody diarrhoea (haemolytic uraemic syndrome), toxic megacolon or perforation, potassium below 2.5 or above 6.0 mmol/L or a new arrhythmia, hypoglycaemia or convulsion in a small child, or severe acute malnutrition requiring the modified 10 mL/kg regimen.

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