15.4.6 Acute & Chronic Diarrhoea In Children Flashcards
What is diarrhoea?
- a symptom (in acute gastroritis)
- Increased stool frequency
- Decreased stool consistency
- Increased stool volume or weight
- In children >10ml/kg/day = diarrhoea
- > 30ml/kg/day dehydration and nutritional consequences
Acute gastroenteritis
- Leading cause of infant death and morbidity worldwide, especially in LMIC countries (low and middle income countries)
- Most cases due to viral infection, bacterial pathogens and parasites too
- Spread is typically faecal-oral, including contamination of food or water
- Lack of breastfeeding, early weaning and use of incorrect weaning foods predispose to diarrhoea and malnutrition
Pathophysiology of diarrhoea in acute gastroenteritis
- Increased loss of water and electrolytes
- Decreased absorption of water, electrolytes ± nutrients
- Loss of intestinal barrier function
What are the functions of the intestine?
- Absorb water and electrolytes
- Digest and absorb nutrients
- Barrier between lumen and body
➡️for micro-organisms and large antigenic molecules
BUT
➡️must be Semi-permeable to allow for absorption and allow immune interaction
Water absorption: adult
In adults 8-10 litres of fluid containing copious amounts of sodium, potassium and chloride enter the proximal small intestine daily
Approximately two litres is consumed as part of the normal dietary intake and the remainder comes from secretions from the salivary glands, stomach, biliary and pancreatic ducts and small intestine.
The small intestine absorbs all but about 1.5litres of this fluid. The large intestine absorbs all but approximately 100-150ml of water and electrolytes of the remaining fluid.
What remains is excreted as faeces.
Regardless of what is consumed, the proximal small intestine is very permeable to water and allows both water and electrolytes to equilibrate with luminal gut contents to ensure that the food that is ingested becomes isotonic with plasma by the time it reaches the proximal jejunum. This allows for optimal absorption of fluid, electrolytes and nutrients in the jejunum.
Principals in children are the same but volumes are proportionally smaller
Water absorption in the intestine
Small intestine
- have both villi and crypts
- nutrients absorbed
Colon
- only crypts, but no villi
- absorb water and electrolytes but no nutrients
- Normally sodium is absorbed at the tips of villi and chloride is secreted in the small intestinal crypts.
- In normal physiological states this leads to net absorption of water and elctrolytes as shown on the left.
- In secretory diarrhoea as indicated on the right the net flow is reversed with excess loss of water and electrolytes
Infective causes of acute gastroenteritis
Viruses
- rotavirus
- norovirus
Bacteria
- Salmonella
- Shigella
Protozo
- Cryptosporidium
Non-infective causes of acute diarrhoea
- Antibiotics/drugs
- Osmotically active substances that are not digested and absorbed e.g. laxatives, phosphate or magnesium salts, lactose, other sugars, fatty acids, bile acids
- Cow’s milk protein allergy
Cholera
- vibrio choleria - Gram- bacillus
- lives in water
- spread by contamination of food an drinking water supplies
- Enters the gut after ingestion of contaminated food or water
- large amount of organisms should be ingested to produce symptoms
- if cholera can survive acidity of stomach they move to small intestine; where they adhere to epithelium
- produces a toxin that leads to excess chloride secretion, disturbing the normal balance between secretion and absorption (leads to net loss of large vol of fluid into the intestine)
- Treatment: antibiotic / oral dehydration therapy
Severe complications
- Dehydration
- Severe dehydration: Hypovoleamic shock ➡️ impaired organ perfusion ➡️ organ dysfunction or failure
- Electrolyte abnormalities (eg hypokalaemia, hypernatraemia)
… may lead to death - Also comorbid conditions may kill…
- Pneumonia, bacteraemia, malnutrition, HIV
Other complications
- Dehydration
- Shock
- Metabolic acidosis
- Hyponatraemia
- Hypernatraemia
- Hypokalaemia
- Hypocalcaemia
- Hypomagnesaemia
- Hypoglycaemia
- Seizures
- Acute kidney injury and renal failure
- Ischaemic brain injury
- Venous sinus thrombosis
- Systemic infection
- Persistent gastroenteritis
- Haemolytic uraemic syndrome
Signs of Dehydration
- loss of skin turgour
- thirst
- sunken eyes
- sunken fontanelle
- tachycardia
- oliguria
Shock: emergency treatment
- poor perfusion
- weak pulses
- cold peripheries
What is chronic diarrhoea?
- Most cases of acute gastroenteritis resolve within a few days
- When diarrhoea lasts longer than two weeks = chronic diarrhoea
- NB: any severe enteropathy (eg severe celiac disease, IBD or severe malnutrition) may lead to generalised malabsorption through a combination of multiple mechanisms
Mechansims of chronic diarrhoea
- Secretory (watery)
- Osmotic (watery)
- Inflammatory – typically stools with blood and mucus
- Steatorrhoea (fatty stool)
- Creatorrhoea (protein-losing enteropathy)
Pathophysiology of secretory diarrhoea
- Diarrhoea is caused by abnormal fluid and electrolyte transport – either decreased absorption or increased secretion (of water and electrolytes)
- Chronic intestinal infection eg Cryptosporidium parvum in an immunocompromised patient can cause chronic watery diarrhoea
- Inflammatory mediators (histamine, serotonin, prostaglandins) can also increase intestinal secretion – infection or inflammatory bowel disease
