Define acute diarrhoea in children. List its causes. How would you assess for dehydration in such a child?

Definition of Acute Diarrhoea in Children

Acute diarrhoea in children is generally defined as the passage of three or more loose or liquid stools per day, or more frequent passage than is normal for the individual child, lasting for less than 14 days. This definition emphasizes the change in stool consistency and frequency from the child's usual pattern rather than just the number of stools. Episodes lasting longer than 14 days are classified as persistent diarrhoea.

Causes of Acute Diarrhoea in Children

Acute diarrhoea in children is predominantly caused by infections (gastroenteritis), though non-infectious causes can also occur. The transmission often occurs through contaminated food or water, or person-to-person via poor hygiene.

1. Infectious Causes (Gastroenteritis)

• Viral Infections: These are the most common cause of acute watery diarrhoea.
  • Rotavirus: Historically the leading cause of severe, dehydrating gastroenteritis in children worldwide, though its incidence has reduced significantly in many regions due to vaccination programs.
  • Norovirus: Common cause, often associated with outbreaks.
  • Adenovirus and Astrovirus: Other frequently identified viral pathogens.
• Bacterial Infections: Can cause watery or bloody diarrhoea (dysentery).
  • Escherichia coli (E. coli): Various strains like Enterotoxigenic E. coli (ETEC), Enteropathogenic E. coli (EPEC), Enteroinvasive E. coli (EIEC), and Enterohemorrhagic E. coli (EHEC). ETEC is a frequent cause of acute secretory diarrhoea.
  • Salmonella spp.: Often linked to food poisoning, can cause bloody diarrhoea.
  • Shigella spp.: A common cause of acute bloody diarrhoea (dysentery).
  • Campylobacter jejuni: Another common bacterial cause of bloody diarrhoea.
  • Vibrio cholerae: Causes severe watery diarrhoea, particularly in endemic areas or during epidemics.
• Parasitic Infections: Less common than viral or bacterial but can lead to persistent or acute diarrhoea.
  • Giardia lamblia (Giardiasis): Can cause acute or chronic diarrhoea.
  • Cryptosporidium parvum (Cryptosporidiosis): Particularly problematic in immunocompromised children.
  • Entamoeba histolytica (Amoebiasis): Can cause dysentery.

2. Non-Infectious Causes

These are less common for acute onset but can include:

• Food Intolerances or Allergies: Such as cow's milk allergy or lactose intolerance (can sometimes be secondary to infectious diarrhoea).
• Inflammation of the Bowel (Colitis): Rarer disorders.
• Antibiotic-associated diarrhoea: Many antibiotics can cause mild diarrhoea as a side effect.

Assessment for Dehydration in a Child with Acute Diarrhoea

Assessing dehydration is paramount as it is the most life-threatening complication of acute diarrhoea. The assessment relies on a combination of clinical signs and symptoms, often categorized by severity. The World Health Organization (WHO) provides a widely adopted classification system.

1. Clinical Observation (WHO Classification)

The assessment involves observing the child's general condition, eyes, mouth, thirst, and performing a skin pinch test.

Sign	No Dehydration	Some Dehydration	Severe Dehydration
General Condition	Alert, well	Restless, irritable	Lethargic or unconscious
Eyes	Normal	Sunken	Very sunken
Tears	Present	Absent	Absent
Mouth and Tongue	Moist	Dry	Very dry
Thirst	Drinks normally, not thirsty	Drinks eagerly, thirsty	Drinks poorly or not able to drink
Skin Pinch (Abdomen)	Goes back quickly	Goes back slowly (less than 2 seconds)	Goes back very slowly (≥2 seconds, 'skin tenting')
Capillary Refill Time	Normal (<2 seconds)	Slightly prolonged	Markedly prolonged (≥3 seconds)

Classification based on WHO signs:

• No Dehydration: Not enough signs to classify as some or severe dehydration.
• Some Dehydration: Two or more of the signs for "Some Dehydration" are present (e.g., restless/irritable, sunken eyes, drinks eagerly/thirsty, skin pinch goes back slowly).
• Severe Dehydration: Two or more of the signs for "Severe Dehydration" are present (e.g., lethargic/unconscious, very sunken eyes, drinks poorly or not able to drink, skin pinch goes back very slowly). This is a medical emergency requiring immediate intervention.

2. Other Important Assessment Parameters

• Urine Output: Decreased frequency or volume of urination, or dark-colored urine, indicates dehydration. No urine for 8-12 hours is a significant sign of severe dehydration.
• Weight Change: An acute weight loss is the most accurate indicator of fluid deficit, though premorbid weight is often unknown. A loss of 3-5% body weight indicates mild dehydration, 6-9% moderate, and ≥10% severe.
• Fontanelle (in infants): A sunken anterior fontanelle is a sign of dehydration.
• Pulse and Blood Pressure: Rapid, weak pulse and low blood pressure (especially in severe dehydration) are critical signs.
• Respiration: Deep, rapid breathing (Kussmaul breathing) can indicate metabolic acidosis, often associated with severe dehydration.

Early and accurate assessment is crucial to initiate appropriate rehydration therapy, which is the cornerstone of managing acute diarrhoea and preventing adverse outcomes.