Diarrhea Causes and Types

Causes of Diarrhea

Infectious causes:
- Bacterial infections (e.g., E. coli, Salmonella, Shigella)
- Viral infections (e.g., Rotavirus, Norovirus)
- Parasitic infections (e.g., Giardiasis, Cryptosporidiosis)
Non-infectious causes:
- Food poisoning
- Medications (e.g., antibiotics, chemotherapy)
- Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis)
- Irritable bowel syndrome (IBS)
- Lactose intolerance
- Fructose malabsorption
- Artificial sweeteners (e.g., sorbitol, xylitol)

Symptoms of Diarrhea

Common symptoms:
- Frequent, loose, or watery stools
- Urgency to have a bowel movement
- Abdominal cramps or pain
- Bloating or gas
- Nausea and vomiting
- Fever
- Blood in the stool (in some cases)
Dehydration symptoms:
- Dry mouth and throat
- Fatigue or lethargy
- Dizziness or lightheadedness
- Decreased urine output
- Dark yellow or amber-colored urine

Treatment of Diarrhea

Fluid replacement:
- Oral rehydration therapy (ORT) with electrolyte-rich fluids (e.g., Pedialyte, sports drinks)
- Intravenous fluids (in severe cases)
Medications:
- Anti-diarrheal medications (e.g., loperamide, bismuth subsalicylate)
- Antibiotics (if bacterial infection is suspected)
- Anti-inflammatory medications (e.g., mesalamine, sulfasalazine)
Rest and hydration:
- Resting the bowel by avoiding solid foods for a short period
- Drinking plenty of fluids to prevent dehydration

Nutritional Management of Diarrhea

Bland diet:
- Bananas
- Rice
- Applesauce
- Toast (BRAT diet)
- Plain crackers
- Plain cooked vegetables
Electrolyte-rich foods:
- Bananas (potassium-rich)
- Avocados (potassium-rich)
- Coconut water (electrolyte-rich)
- Sports drinks (electrolyte-rich)
Avoid:
- Dairy products (if lactose intolerant)
- High-fiber foods
- Spicy or fatty foods
- Caffeine and alcohol

Causes of Diarrhea

Infectious causes of diarrhea include bacterial infections such as E. coli, Salmonella, and Shigella, viral infections like Rotavirus and Norovirus, and parasitic infections like Giardiasis and Cryptosporidiosis.
Non-infectious causes include food poisoning, certain medications like antibiotics and chemotherapy, inflammatory bowel disease, irritable bowel syndrome, lactose intolerance, fructose malabsorption, and artificial sweeteners like sorbitol and xylitol.

Symptoms of Diarrhea

Common symptoms of diarrhea include frequent, loose, or watery stools, urgency to have a bowel movement, abdominal cramps or pain, bloating or gas, nausea and vomiting, fever, and blood in the stool in some cases.
Dehydration symptoms may include dry mouth and throat, fatigue or lethargy, dizziness or lightheadedness, decreased urine output, and dark yellow or amber-colored urine.

Treatment of Diarrhea

Fluid replacement is crucial and can be done through oral rehydration therapy with electrolyte-rich fluids like Pedialyte or sports drinks, or through intravenous fluids in severe cases.
Medications may include anti-diarrheal medications like loperamide, antibiotics if a bacterial infection is suspected, and anti-inflammatory medications like mesalamine or sulfasalazine.
Resting the bowel by avoiding solid foods for a short period and drinking plenty of fluids to prevent dehydration is also important.

Nutritional Management of Diarrhea

A bland diet can help manage diarrhea and includes foods like bananas, rice, applesauce, toast, plain crackers, and plain cooked vegetables.
Electrolyte-rich foods like bananas, avocados, coconut water, and sports drinks can help replace lost electrolytes.
Foods to avoid when experiencing diarrhea include dairy products for those who are lactose intolerant, high-fiber foods, spicy or fatty foods, caffeine, and alcohol.

Chronic Diarrhea

Definition: Increase in stool frequency (3 or more stools/day) and/or presence of loose or liquid stools; traditionally defined as an increase in daily stool weight (> 200 g/day)
Normal stool fluids processing:
- 8-9 L/d enter GI system
- 1-2 L/d ingested
- 7 L/d created
- Small bowel reabsorbs 6-7 L/d
- Large bowel absorbs 1-2 L/d
- 100-200 g/d stool created
Review of Nutrient/Vitamin Absorption:
- Duodenum/Jejunum: Carbohydrates, Amino acids, Iron, Calcium, Magnesium
- Ileum: Vitamin B12, Bile salts, Fat-soluble vitamins (A, D, E, K)
- Colon: Short-chain fatty acids, Biotin**, Magnesium
Chronic diarrhea: 5% prevalence; most frequent etiologies include functional disorders (IBS), inflammatory bowel disease (IBD), malabsorptive syndromes, and chronic infection

Small Bowel Function

Motility
Digestion
Absorption
Immune defense

Pathophysiology of Chronic Diarrhea

Types:
- Osmotic diarrhea
- Secretory diarrhea
- Inflammatory diarrhea
- Motility disturbances
Osmotic diarrhea:
- Causes: Ingestion of poorly absorbed osmotically active substances (non-electrolytes), carbohydrate malabsorption, and disaccharidase deficiency
- Examples: Mannitol, Sorbitol, Lactulose, Magnesium, Sulfate, Phosphate
Secretory diarrhea:
- Causes: Exogenous secretagogues (cholera toxin), endogenous secretagogues (neuroendocrine tumor), absence of ion transporter (congenital chloridorrhea)
Inflammatory diarrhea:
- Causes: Structural damage to intestinal mucosa, inflammatory mediators (histamine, serotonin, adenosine, cytokines, prostaglandins, leukotrienes), and IBD (Crohn's disease, UC)
- Examples: Invasive bacterial, parasitic, and viral infections, radiation colitis, ischemic colitis
Motility disturbances:
- Causes: Abnormal intestinal motility, hyperthyroidism, dumping syndrome, and diabetic autonomic neuropathy
- Examples: Postvagotomy diarrhea, postsympathectomy diarrhea

Clinical Classification and Diagnosis

Chronic diarrhea:
- Is it organic or functional?
- Clinical classification: Fatty, Watery, Inflammatory
- Work-up diagnosis: Blood analysis, imaging, endoscopic examination (based on clinical classification)
History:
- Effect of fasting on diarrhea
- Antibiotic use and risk of Clostridium difficile infection
- Substantial change in diet and new medication
- Travel history and exposure to contaminated food or water
- Stool characteristics, weight loss, and family history of IBD

Common Medications and Toxins Associated with Diarrhea

Acid-reducing agents (H2 blockers, PPIs)
Magnesium-containing antacids
Anti-arrhythmics (eg, digitalis, quinidine)
Antibiotics
Anti-neoplastic agents
Antiretrovirals
Beta blockers
Colchicine
Levothyroxine
SSRIs
Furosemide
Metformin
NSAIDs
Prostaglandin analogs (misoprostol)
Theophylline
Amphetamines
Caffeine
Alcohol
Narcotic/opioid withdrawal

Initial Evaluation and Physical Examination

Determining severity of diarrhea
Orthostatic changes
Fever
Bowel sounds (or lack thereof)
Abdominal distention, tenderness, masses, evidence of prior surgeries
Hepatomegaly
Digital rectal examination
Skin, joints, thyroid, peripheral neuropathy, murmur, edema

Differential Diagnosis and Laboratory Tests

Fatty diarrhea: Maldigestion, malabsorption, and osmotic diarrhea
Watery diarrhea: Very broad differential – bacterial toxins, ileal bile acid malabsorption, malignancy, medications, endocrinopathies, idiopathic
Inflammatory diarrhea: IBD (Crohn's, UC), microscopic colitis, ischemic colitis, diverticulitis, radiation colitis, infectious etiologies
Routine laboratory tests: Complete blood count, serum chemistry screening, inflammatory markers, thyroid hormones
Spot stool analysis: Occult blood, white blood cells, Sudan stain for fat
Endoscopic examination and mucosal biopsy: Sigmoidoscopy/colonoscopy with ileoscopy, upper tract endoscopy, small bowel capsule endoscopy

Hydrogen Breath Test and Other Diagnostic Tests

Diagnostic tool for small intestinal bacterial overgrowth and carbohydrate malabsorption
Tests for food GI allergy, mucosal absorption test, breath tests for physiological testing

Treatment

Correct dehydration and electrolyte deficits
Generally, empiric course of antibiotics is not useful for chronic diarrhea
Treat the cause
Dietary restrictions, pancreatic enzyme supplementation, opiates, bile acid binding resins, clonidine, and octreotide may be used in specific clinical settings