Diarrhea

Definitions:

Harriet Lane:

Acute Diarrhea is >3 loose or watery stools per day
Chronic Diarrhea is Diarrhea lasting >2-4wks

Wylie:

WHO defines diarrhea as passing >3 liquid stools daily
Acute < 4wks
Chronic > 4wks

Globally diarrhea is the 4th leading cause of mortality in children <5yo (mostly due to infection: rotavirus)

"Normal" stool on western diet: 10mL/kg/day (infant) or 200g/day (adult). Infants can pass stool multiple times daily or once every 2 wks and still be considered within normal for growth and development -Wylie

Classifications: (can often be mixed etiology)

Osmotic Diarrhea - Water is drawn into lumen by maldigested compounds (i.e. celiac, lactose intolerance, or pancreatic disease) Decreases with fasting (Stool Osmolar gap >125 mOsm/kg)

Secretory Diarrhea - Water accompanies secreted or unabsorbed electrolytes into the lumen (excessive secretion of Cl- by cholera toxin) stool volume increased and independent of diet (Stool Osmolar gap <50 mOsm/kg)

Stool Osmolar Gap = Stool Osm - [2 x (Stool Na mEq/L + Stool K mEq/L)]
Stool Osmolar Gap = 290 - 2(Stool Na + Stool K)

Inflammatory Diarrhea - Cytokines (such as interleukin 1 [IL-1] and tumor necrosis factor α [TNF-α]), chemokines (such as IL-8, which attracts eosinophils), and prostaglandins induce intestinal secretion by enterocytes and activate enteric nerves

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EVALUATION

History

Duration of diarrhea (acute vs. chronic vs. recurrent)
Onset of diarrhea (sudden or gradual)
Number of daily stools
Volume of stools (large-volume diarrhea arises from the small intestine, and small volume usually from the colon)
Consistency of most of the stools (in IBS, stools can vary from well-formed to liquid)
Presence of blood in stool (anal fissure, allergy, IBD)
Painful defecation or not (anal fissure, IBD)
Fecal urgency (IBD)
Presence of diarrhea in fasting state and while sleeping (secretory diarrheas like cholera, vipoma, and IBD)
Associated symptoms such as fever, vomiting, abdominal pain, skin rash, joint involvement (infectious, IBD)
Dietary intake, for example, fruit juice and milk intake (toddler’s diarrhea, lactose intolerance)
History of sick contacts (infectious)
History of recent antibiotic usage (antibiotics-associated diarrhea, Clostridium difficile )
History of recent travel/camping (traveler’s diarrhea, parasites like Giardia spp. )
History of previous surgery (short-bowel syndrome, ileum resection)
Family history of GI disease (cystic fibrosis, IBD)
History of recurrent bacterial infection or immunocompromised state (cystic fibrosis, HIV, on immunosuppressants, after bone marrow transplantation)
History of weight loss, aphthous ulcers, growth delay, uveitis, arthralgias, or arthritis (IBD)

Physical Exam

Assess for dehydration in acute patients
(Table from HL for dehydration assessment)
Normal (<5% dehydration) = General appearance: well, alert; normal eyes; drinks normally/not thirsty; Skin pinch (turgur) goes back quickly

Degree of dehydration
Signs of systemic illness (pharyngeal erythema, fever, otitis media)
Signs of significant dehydration (sunken anterior fontanel, tachycardia, dry mucous membranes, oliguria/anuria, tachypnea, orthostatic hypotension)
Current weight and premorbid weight (if available)
Assessment of growth chart
Presence of pallor, icterus, petechiae, skin rash
Abdominal tenderness, distended abdomen
Rectal examination: presence of perianal skin tags, fissure, fistula
Extraintestinal manifestations: Eye examination (uveitis), joints (arthritis), lungs (pleural effusion), heart (pericardial effusion), skin (erythema nodosum, pyoderma gangrenosum)
Signs of fat-soluble vitamin deficiency (rickets, night blindness, bruises, peripheral neuropathy)

Labs:
Stool:

pH ( if <6 with reducing substances present, osmotic diarrhea like carbohydrate malabsorption)
Reducing Substances
Osmotic Gap (<50 secretory and >125 Osmotic)
Fecal Leukocytes
Occult Blood
Calprotectin (Inflammation and infection or polyps)
Lactoferrin
Qualitative and Quantitiative 3-day fecal fat estimation (difficult but still gold standard for fat malabsorption)
Stool Ova and Parasites (O&P)
Fecal pancreatic Elastase (measures pancreatic exocrine function)
Alpha-1-Antitrypsin (A1AT) (Protein loss in stool)
Stool Culture

Blood:

CBC
ESR
CRP
Total and Direct Bilirubin
Albumin
Total Protein
ALT
AST
GGT
Serum bile acids
Thyroid stimulatin hormone & Free T4 (Thyroid Disease)
Total IgA / Anti-TTG IgA / Anti-endomysial IgA (Celiac)
Vitamin A, D, E, K levels (Fat Malabsorption)
Vitamin B12 and Folate Levels

Breath Testing: Lactose and Fructose Breath Testing

Sweat Chloride testing

Imaging

KUB
Small Bowel Follow through (SBFT)
MR enterography
CT enterography

Endoscopy
EGD
Colonoscopy
Video Capsule endoscopy

If "Diarrhea" turns out to be encopresis, consider Constipation diagnoses, ARM, or rectal suction Bx as indicated

DDx:

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Acute Diarrhea - Viruses are most common cause

Viral
• Rotavirus
• Calicivirus
• Norovirus
• Enterovirus
• Astrovirus

Bacterial
• Salmonella spp.
• Campylobacter jejuni
• Escherichia coli
• Shigella spp.
• Yersinia enterocolitica
• Clostridium difficile
• Vibrio cholerae
• Aeromonas spp.

Parasitic
• Entamoeba histolytica
• Giardia spp.
• Cryptosporidium spp. --immunocompromised patients such as patients with HIV.
• Isospora belli --immunocompromised patients such as patients with HIV
• Balantidium coli
• Strongyloides stercoralis

Noninfectious Causes
Drug-Induced
• Antibiotics induced (erythromycin, amoxicillin clavulanate, others)
• Laxatives (lactulose, senna, others)
• Opiate withdrawal
• Oral magnesium

Food Allergies

Extraintestinal Infections
• Sepsis
• Urinary tract infections
• Respiratory tract infections
• Otitis media

Surgical Conditions
• Acute appendicitis
• Intussusception

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Chronic Diarrhea

Malabsorptive Diarrheas

Carbohydrate Malabsorption

Primary and secondary lactose malabsorption
Sucrose malabsorption
Fructose malabsorption
Postenteritis syndrome

Fat Malabsorption

Cholestatic Conditions
Biliary atresia, progressive familial intrahepatic cholestasis, bile acid synthetic disorders, primary sclerosing cholangitis, cystic fibrosis

Conditions Causing Exocrine Pancreatic Insufficiency
Cystic fibrosis, Shwachman syndrome, chronic pancreatitis leading to exocrine pancreatic insufficiency, Johanson-Blizzard syndrome

Decreased Enterohepatic Circulation of Bile Acids
Ileal resection secondary to necrotizing enterocolitis, Crohn disease, congenital absence of ileal bile receptor

Chronic Diarrhea of Inflammatory Origin
Inflammatory bowel disease: Crohn disease, ulcerative colitis, indeterminate colitis
Celiac disease
Microscopic or collagenous colitis
Eosinophilic gastroenteritis

Congenital Diarrheas
Microvillus inclusion disease
Tufting enteropathy
Autoimmune enteropathy
Chloride channel diarrhea
Sodium channel diarrhea
Congenital glucose–galactose malabsorption
Congenital sucrose–isomaltase deficiency
Abetalipoproteinemia and hypobetalipoproteinemia
Congenital lactase deficiency

Intestinal Failure
Secondary to extensive intestinal resection (necrotizing enterocolitis volvulus, infarction, ischemia, Crohn disease)
Secondary to motility issues (chronic intestinal pseudo-obstruction [CIPO])
Secondary to congenital defects (tufting enteropathy, microvillus inclusion disease, autoimmune enteropathy)
Secondary to bacterial overgrowth in intestine

Infectious
Chronic parasitic infestation ( Giardia lamblia , Cryptosporidium ) spp.
Viral infections: HIV
Bacterial: Clostridium difficile , Salmonella , spp. Campylobacter , spp. postenteritis syndrome

Medication Induced
Chronic laxative abuse
Magnesium-containing antacids
Erythromycin group of antibiotics
Antibiotic-induced diarrhea

Neurohormonal Causes
Hyperthyroidism
Gastrinoma
Vipoma
Ganglioneuroma
Neuroblastoma
Carcinoid

Others
Irritable bowel syndrome
Fecal impaction with overflow incontinence