Diarrhea: Acute and Chronic

Introduction

• Clinical medicine topic: Diarrhea
• Definitions:
  • At least 3 or more loose stools per day for less than 2 weeks = Acute Diarrhea
  • More than 3 loose stools per day for more than 2 weeks = Chronic Diarrhea
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Acute Diarrhea

Classifications

1. Acute Non-Inflammatory (Secretory) Diarrhea

   • Mainly affects the small bowel
   • Pathophysiology: Massive decrease in absorption leads to high volume watery stools
   • No mucosal damage
     • Pathogens release enterotoxins
     • Common pathogens: S. aureus, B. cereus, ETEC, Vibrio cholerae
     • Viral causes: Norovirus (cruise ships), Rotavirus (daycares)
     • Parasitic causes: Giardia (river water), Cryptosporidium (immunocompromised patients)
   • Diagnostic indicators: No fecal WBCs, no fecal calprotectin, no blood in stool

2. Acute Inflammatory Diarrhea

   • Mainly affects the colon
   • Pathophysiology: Direct mucosal damage
     • Pathogens release toxins and cause mucosal injury
     • Common pathogens: Salmonella, Shigella, Campylobacter, EHEC O157:H7, C. difficile
     • Parasitic cause: Entamoeba histolytica
   • Diagnostic indicators: Presence of fecal WBCs, fecal calprotectin, blood in stool
   • Results in dysentery: bloody, mucous-containing stools

Chronic Diarrhea

Classifications

1. Secretory Diarrhea

   • Affected by hormone levels and stimulant laxatives
   • Pathophysiology: Over-secretion of electrolytes and water into the bowel
     • Common causes: VIP (VIPoma), Gastrin (Gastrinoma), Serotonin (Carcinoid Syndrome), Stimulant laxatives (Senna, Docusate)
   • Diagnostic indicators: Watery diarrhea, low stool osmotic gap

2. Osmotic Diarrhea

   • Pathophysiology: Malabsorbed or maldigested substrates pull water into bowel
     • Common causes: Celiac disease, EPI (Exocrine Pancreatic Insufficiency), Tropical Sprue, Whipple's disease, Lactose intolerance, Osmotic laxatives
   • Diagnostic indicators: Watery or fatty diarrhea (steatorrhea), high stool osmotic gap

3. Inflammatory Diarrhea

   • Pathophysiology: Chronic inflammation damages mucosa
     • Common causes: Inflammatory Bowel Disease (IBD) such as Crohn's Disease and Ulcerative Colitis, Chronic infections (e.g., CMV)
   • Diagnostic indicators: Bloody, mucous-containing stools, presence of fecal WBCs and calprotectin

Complications of Acute Diarrhea

• Hypovolemia

  • Symptoms: Tachycardia, low BP, dry mucous membranes, decreased skin turgor, low urine output, acute kidney injury
  • Laboratory findings: Low electrolytes, metabolic acidosis (non-anion gap)

• Colitis

  • Symptoms: Abdominal pain, fever, high WBC count
  • Severe forms: Toxic megacolon, perforation, peritonitis, sepsis
  • Common pathogens: EHEC, Shigella, C. difficile

• Hemolytic Uremic Syndrome (HUS)

  • Caused by pathogens like EHEC and Shigella
  • Triad: Hemolytic anemia, thrombocytopenia, acute kidney injury

Diagnostic Approach for Diarrhea

Acute Diarrhea

• Obtain CBC and BMP:
  • Identify complications: HUS, hypovolemia, metabolic acidosis
• Stool analysis if high-risk:
  • Tests: Fecal WBCs, fecal calprotectin, stool cultures, O&P, norovirus/rotavirus testing

Chronic Diarrhea

• Determine if inflammatory:

  • Tests: Fecal WBCs, fecal calprotectin, fecal occult blood test
  • If positive, perform stool analysis and colonoscopy

• Determine if secretory or osmotic:

  • Test stool osmotic gap
  • Secretory: Low gap, test VIP, gastrin, serotonin levels
  • Osmotic: High gap, perform fecal fat test (for malabsorption), hydrogen breath test (for maldigestion)

Treatment of Diarrhea

• Acute Diarrhea:

  • Manage complications: Hypovolemia (fluids), severe colitis (antibiotics), HUS (supportive care, avoid antibiotics and loperamide)
  • Antidiarrheal agents: Avoid loperamide, consider bismuth subsalicylate

• Chronic Diarrhea:

  • Identify and treat underlying cause: Laxatives, hormone-related issues, malabsorption/maldigestion, inflammatory bowel disease