11. Pediatric Diarrhea

Question 1

Chronic diarrhea after infancy in developing countries is often the result of what? (2)

Answer 1

• malnutrition and serial infections
• whereas in developed countries, it is mostly due to noninfectious processes.

Question 2

Pathophysiologic mechanisms of diarrhea include what? (4)

Answer 2

• Osmotic: ingested, nonabsorbed solutes reach colon, creating an osmotic gradient that allows water diffusion into the lumen (e.g., lactase deficiency).
• Secretory: excessive secretion of electrolytes (especially Cl−, through CFTR) into lumen after noxious stimulus, with water subsequently following (e.g., bacterial toxin)
• Altered motility: increased motility results in reduced transit time for water absorption (e.g., ileocecal valve resection)
• Inflammation: multifactorial—damage/atrophy of villi, epithelial cell dysfunction (e.g., altered fluid/electrolyte transport), and increased motility and secretions (e.g., infection, IBD)

Question 3

Name INFECTIOUS Acute causes of diarrhea (3)

Answer 3

• Viral: rotavirus, calicivirus (Norovirus, Sapovirus), enteric adenovirus, astrovirus
• Bacterial: E. coli, Salmonella, Campylobacter, Shigella, Yersinia, Clostridium, Listeria
• Parasitic: Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Cyclospora

Question 4

Name NON-INFECTIOUS Acute causes of diarrhea (4)

Answer 4

• Medication-related: antibiotic-associated diarrhea, drug side effect
• Allergy
• Toxin ingestion (foodborne/other): bacterial, pesticide, heavy metal
• Acute abdo presenting as diarrhea: intussusception, appendicitis, toxic megacolon, evolving bowel obstruction

Question 5

Name: Chronic causes of diarrhea (13)

Answer 5

• Enteric infection
• Postinfectious (villous atrophy)
• Immune-mediated
  
  • Celiac disease
  • IBD
  • Food protein-induced enter- opathy (e.g., cow’s milk protein intolerance)
  • Eosinophilic gastroenteritis
• Immune defects (1o or 2o)
• Functional
  
  • Toddler’s diarrhea
  • Irritable bowel syndrome
• Fecal impaction (overflow incontinence)
  
  • Functional constipation
  • Secondary constipation (e.g., HD, anorectal malformation, dysmotility)
• Neuroendocrine
  
  • Hyperthyroidism
  • Neoplasm (gastrinoma, VIPoma, systemic mastocytosis, neuroblastoma)
• Short bowel syndrome
• Small intestinal bacterial overgrowth
• Carbohydrate malabsorption
  
  • Constitutional lactase deficiency (decreased intestinal lactase levels over time, genetically regulated)
  • Secondary disaccharidase deficiency (after mucosal injury)
  • Congenital (e.g., lactase or sucrase- isomaltase deficiency, glucose-galactose malabsorption)
  • Dietary (excess fructose/sorbitol)
• Fat maldigestion/malabsorption
  
  • Pancreatic exocrine insufficiency, e.g., cystic fibrosis
  • Intrahepatic/extrahepatic cholestasis
  • Bile acid metabolism/synthesis defects,ileal resection/disease
• Protein-losing gastroenteropathy
  
  • Mucosal erosion/ulceration
  • Intestinal lymphangiectasia (1°/2°)
• Transporter/metabolic defects
  
  • Congenital secretory diarrhea
  • Galactosemia, tyrosinemia

Question 6

Name: Diarrhea redflags (9)

Answer 6

• Severe continuous or nocturnal diarrhea
• Systemic symptoms: fever, rash, arthritis
• Blood or mucous in the stool
• Very acidic stools
• Weight loss/failure to thrive
• Petechiae or purpura
• Signs of dehydration
• Change in mental status
• Severe abdo pain or distension

Question 7

Describe investigations: Acute diarrhea (6)

Answer 7

• Investigations should be based on DDx, none needed in most previously well children with uncomplicated, watery diarrhea (most cases viral, self-limiting).
• Stool Culture and Sensitivity, Ova and Parasites if bloody diarrhea, outbreaks with suspected HUS, immunosuppressed, recent travel to or exposure to endemic area
• Stool for C. difficile if recent antibiotic use (past 12 wk) and bloody diarrhea ± systemic toxicity, fever or abdo pain or diarrhea in immunocompromised patient and recent antibiotic/chemotherapy
• Consider: urine Routine and Microscopy, Culture and Sensitivity if febrile and no other source of infection is identified, CXR if associated respiratory symptoms
• Blood work and blood cultures if ill-appearing or significant dehydration requiring IV rehydration
• Imaging studies (abdo U/S, computed tomography, and air contrast enema) if findings suggestive of intussusception, appendicitis, or an acute abdo

Question 8

Describe investigations: Chronic diarrhea (11)

Answer 8

• In absence of red flags, may require minimal investigation (functional diarrhea is not necessarily Dx of exclusion).
• Favor noninvasive testing
• Initial blood work may include inflammatory parameters (ESR, CRP, PLT, WBC, and differential), Hgb and iron studies, electrolytes, calcium, total protein and albumin, INR, transaminases, lipase, celiac screen, and TSH.
• Stool assessment for inflammation: fecal WBC ± calprotectin, infectious
• workup as above
• Stool pH and electrolytes if watery stools, help distinguish between osmotic and secretory diarrhea:
• Suspected carbohydrate maldigestion/malabsorption
  
  • Stool for reducing substances
  • Lactose hydrogen breath test
• Steatorrhea/suspected fat malabsorption
  
  • Tests of malabsorption: stool microscopy for fat globules, quantitative 72-h fecal fat collection
  • Screen for cholestasis: bilirubin (total/direct), GGT, ALP, vitamin A, D, and E levels, INR, triglycerides, cholesterol
  • Screen for pancreatic insufficiency: fecal elastase, sweat chloride
• Suspected protein-losing enteropathy
  
  • Stool a 1-antitrypsin
  • Calcium, INR, albumin
• Immunoglobulins: suspected immunodeficiency or eosinophilic gastroenteritis (IgE elevated in ~50% of cases)
• Specialized tests if indicated: abdo U/S, upper GI series with small bowel follow through, endoscopy

Question 9

How to differentiate osmostic and secretory diarrhea according to Stool pH and electrolytes? (2)

Answer 9

• Osmotic: pH 125mM, Na+ < 60 mM
• Secretory: pH > 5, osmotic gap < 50 mM, Na+ > 90 mM

Question 10

Describe: Stool Osmotic Gap (4)

Answer 10

• Estimates relative contributions of electrolytes and nonelectrolytes to retention of water in the intestinal lumen
• Normal stool osmolarity is 290 mmol/L (isotonic to plasma)
• Stool Na+ and K+ in stool multiplied by 2 in the equation to account for obligate anions
• Stool osmotic gap (mmol/L) = 290 (or measured stool osmolarity) − 2 (stool [Na+] + stool [K+])

Question 11

Describe management: Acute Diarrhea (11)

Answer 11

• Initial assessment of dehydration and fluid rehydration
• Treat electrolyte imbalances; screen for systemic infections
• Continued enteral feeding with age-appropriate diet thereafter, with ORS continued to replace ongoing losses from emesis or stools
• Early refeeding has clinical and nutritional benefits.
• Zinc supplementation can reduce duration and severity of diarrhea.
• Probiotics can reduce duration of acute viral diarrhea (five pediatric meta-analyses).
• Avoid fatty foods or foods high in simple sugars
• Avoid carbonated drinks, sweetened fruit juices, and plain water
• Antibiotics should only be used in children with bloody diarrhea when a specific pathogen has been isolated. Antibiotics may increase the risk of hemolytic uremic syndrome in patients infected with E. coli 0157:H7.
• Antimotility agents contraindicated if bloody stools, also likely no role in management of acute, watery diarrhea in otherwise well children
• Further management depends on the underlying cause.

Question 12

Describement management: Dehydration

• Mild to moderate
• Severe
• Limitations to oral rehydration therapy

Answer 12

• Mild to moderate dehydration:
  
  • rehydration with oral rehydration solution (ORS) (oral rehydration solution) over the first 4 h
• Severe dehydration:
  
  • IV resuscitation with normal saline or Ringer lactate for the first hour, with reassessment and repeated fluid boluses PRN. ORS can be started once stabilized.
• Limitations to oral rehydration therapy: shock, ileus, intussusception, carbohydrate intolerance, severe emesis, or high stool output (> 10 mL/kg/h)

Question 13

Describe management: Chronic Diarrhea (5)

Answer 13

• Management depends on the underlying cause, severity of dehydration, and/or malnutrition
• General dietary principles
  
  • Oral or enteral refeeding essential to stimulate mucosal recovery and avoid protracted diarrhea
    
    • Elemental or semi-elemental formulas and modular diets may be needed to allow for early refeeding
    • Poly/disaccharides—may increase diarrhea
  • Avoid restricted diets and parenteral nutrition, if possible
  • Long-chain triglycerides should be tried (osmotically inert, calorie dense, and absorbed variably in a variety of diseases).
• Antibiotics should only be used in children with bloody diarrhea when a specific pathogen has been isolated. Antibiotics may increase the risk of hemolytic uremic syndrome in patients infected with E. coli 0157:H7.
• Antimotility agents contraindicated if bloody stools, also likely no role in management of acute, watery diarrhea in otherwise well children
• Further management depends on the underlying cause.