CHRONIC DIARRHEA

Question 1

Definition

Answer 1

Persistent alteration of stool consistency from the norm with loose stools (consistency between types 5 and 7 on the Bristol stool chart) and increased stool frequency of greater than 4 weeks duration

Question 2

Causes (4)

Answer 2

• IBS, IBD, malabsorption syndromes (e.g. lactose intolerance and celiac disease), and chronic infections

Question 3

Acute Diarrhea

Answer 3

Diarrhea for less than 2 weeks, usually infectious or drug-induced

Question 4

Fatty Diarrhea (3)

Answer 4

• Caused by fat malabsorption
• E.g. celiac, pancreatic insufficiency, short bowel syndrome, Whipple’s disease
• Investigate with small bowel and pancreatic tests

Question 5

Inflammatory Diarrhea (4)

Answer 5

• Exudative/invasive (damage to intestinal mucosal cells —> mucus, blood, pus)
• May have defective absorption of fluid and electrolytes
• E.g. inflammatory bowel disease, ischemic colitis, radiation colitis, microscopic colitis, malignancy, chronic infections
• Investigate with colonoscopy

Question 6

Watery Diarrhea- Osmotic (5)

Answer 6

• E.g. celiac disease, chronic giardiasis, malabsorption (lactose, fructose, sorbitol, osmotic laxatives)
• The gut mucosa acts as a semi-permeable membrane
• Fluid enters the bowel if there are large quantities of non-absorbed hypertonic substances in the lumen:
  
  • ingestion of non-absorbable substances e.g. MgSO4
  • malabsorption: high concentration of solutes in lumen e.g. sorbitol
• Diarrhea stops when patient stops ingesting osmotic agent
• Stool osmotic gap > 150

Question 7

Watery Diarrhea- Secretory (4)

Answer 7

• E.g. drug induced, lymphoma, IBD, microscopic colitis, endocrine (gastrinoma, VIPoma)
• There is both active secretion of fluids and electrolytes as well as decreased absorption
• Common causes of secretory diarrhea:
  
  • hormones e.g. VIP
  • bile salts in colon following ileal resection
  • laxatives e.g. docusate sodium
• Stool osmotic gap < 50
  (osmotic gap: 290 - 2(Na+K))

Question 8

Approach (4)

Answer 8

• History and physical examination (guide towards the cause)
• Lab tests (CBC, ESR, CRP, PT, INR, Ca, Albumin, Iron studies, Folic acid, Vit B12)
• Stool studies (occult blood, WBCs, pH, Sudan stain for fat, cultures, laxative screen, electrolytes, osmolality)
• Specialized testing depending on suspected cause: colonoscopy/enteroscopy with biopsies, small bowel imaging, capsule endoscopy, celiac serology, pan creating imaging and function, hormone levels (Gastrin, VIP, 5’HIAA, etc)