What causes changes in stool color or consistency and how is it treated?

Changes in Stool Color and Consistency: Causes and Treatment

Changes in stool color and consistency are most commonly caused by irritable bowel syndrome (IBS), which should be treated with a targeted symptom-based approach including dietary modifications, appropriate medications for specific symptoms, and lifestyle changes. 1

Common Causes of Stool Changes

Irritable Bowel Syndrome (IBS)

• IBS is characterized by chronic, recurring abdominal pain or discomfort associated with disturbed bowel habit in the absence of structural abnormalities 1
• Diagnostic criteria include recurrent abdominal pain/discomfort at least 3 days per month in the past 3 months with two or more of:
  • Improvement with defecation
  • Onset associated with change in stool frequency
  • Onset associated with change in stool form/appearance 1
• IBS can be categorized into subtypes based on predominant stool pattern:
  • IBS-D (diarrhea predominant)
  • IBS-C (constipation predominant)
  • Mixed type (alternating between diarrhea and constipation) 1

Food Intolerances

• Common intolerances reported in the UK include wheat, dairy products, coffee, potatoes, corn, and onions 1
• Lactose intolerance is found in 10% of IBS patients but rarely cures IBS completely 1

Infections

• Bacterial, viral, or parasitic infections can cause changes in stool consistency 2
• Viral infections can lead to pale, fatty stools (steatorrhea) 3
• Rotavirus in particular has been associated with fatty stools that are very pale in color 3

Inflammatory Conditions

• Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis 4
• Microscopic colitis can cause chronic watery diarrhea 2
• Pseudomembranous colitis, often associated with C. difficile infection, presents with characteristic yellow-white plaques on the colonic mucosa 5

Other Causes

• Factitious diarrhea (laxative abuse) is a common cause of reported chronic diarrheal symptoms, especially in tertiary referral centers 1
• Faecal retention can paradoxically cause both constipation and diarrhea symptoms 6
• Medications, particularly antibiotics like ciprofloxacin, can alter gut flora and cause changes in stool consistency 7

Diagnostic Approach

Initial Assessment

• Evaluate based on duration of symptoms (chronic diarrhea defined as loose stools lasting >4 weeks) 2
• Consider patient demographics (IBS peaks in third and fourth decades with female predominance) 1
• Look for "red flag" symptoms requiring immediate investigation:
  • Weight loss
  • Rectal bleeding
  • Nocturnal symptoms
  • Anemia 1

Laboratory Testing

• Complete blood count, C-reactive protein, and basic metabolic panel to evaluate for inflammatory conditions 2
• Anti-tissue transglutaminase IgA and total IgA to screen for celiac disease 2
• Stool studies to categorize diarrhea as watery, fatty, or inflammatory 2
• Thyroid function, antiendomysial antibodies, and stool microscopy if indicated 1

Further Investigation

• Sigmoidoscopy if colonic symptoms are present, with biopsy of any abnormalities 1
• Colonic imaging (barium enema or colonoscopy) for patients >45 years at symptom onset or with family history of colon cancer 1
• Lactose tolerance testing if patient consumes substantial amounts of milk (>280 ml/day) 1

Treatment Approach

Dietary Modifications

• Identify and eliminate food intolerances through elimination diets 1
• Consider fiber modifications based on predominant symptoms:
  • Increase fiber for constipation
  • Reduce fiber for diarrhea 1

Pharmacological Treatment

• For constipation:

  • Osmotic laxatives (polyethylene glycol)
  • Stimulant laxatives (bisacodyl)
  • Secretagogues (linaclotide) 1, 8

• For diarrhea:

  • Antidiarrheals (loperamide, codeine phosphate)
  • 5-HT3 antagonists (ondansetron) 1

• For abdominal pain:

  • Antispasmodics (dicycloverine, hyoscine butylbromide)
  • Low-dose tricyclic antidepressants (amitriptyline)
  • Selective serotonin reuptake inhibitors 1

• For bacterial overgrowth:

  • Antibiotics (ciprofloxacin, metronidazole)
  • Non-absorbable antibiotics (rifaximin) 1

Lifestyle Modifications

• Regular physical activity to promote intestinal motility 6
• Adequate fluid intake 1
• Stress management techniques 1

Special Considerations

Post-Surgical Changes

• After bowel surgery, monitor for return of bowel sounds and normal function 8
• Early oral feeding should be initiated within 24 hours of bowel sounds returning 8
• Monitor for passage of flatus and stool as signs of resolving ileus 8

Warning Signs Requiring Immediate Attention

• Failure to tolerate enteral feeding after initial success 8
• Increasing abdominal distension or new onset of abdominal pain 8
• Development of bloody diarrhea, especially after antibiotic use (possible C. difficile infection) 7

Prognosis

• Prognosis depends on length of history (longer history less likely to improve) 1
• Chronic ongoing life stress is a key negative prognostic factor 1