Introduction
Altered bowel habit is more than just a disruption in routine—it can signal anything from functional gut disorders to serious colorectal disease. This comprehensive guide explains every cause, symptom, and investigation for constipation, tailored for both students and clinicians.
What Is a Normal Bowel Habit?
- Variability across individuals
- Role of diet, age, and lifestyle
- Stool frequency and consistency (Bristol Stool Chart)
- When is it considered abnormal?
Defining Constipation
- Constipation: infrequent/difficult evacuation
- Absolute constipation: no stool or gas passage
- Tenesmus: incomplete or painful evacuation
- Functional constipation vs mechanical
- Acute vs chronic constipation
Red Flags in Altered Bowel Habit
| Symptom | Likely Concern |
|---|---|
| Age >55 with new symptoms | Rule out colorectal cancer |
| Blood in stool | Neoplasm, IBD |
| Weight loss + anaemia | Cancer |
| Nocturnal symptoms | Organic, not IBS |
| Family history | Hereditary CRC/polyps |
Major Causes of Altered Bowel Habit
1. Colorectal Causes (H3)
- Colorectal cancer: chronic progression, occult blood, mass
- Colonic Crohn’s disease: segmental inflammation
- Ulcerative colitis: tenesmus, mucus, rectal bleeding
- Diverticular disease: LIF pain, alternating bowel habit
- Rectal polyp: intermittent bleeding, mucus, minor obstruction
2. Anorectal and Neurological Causes
- Rectal fissure: spasm of anal sphincter, pain
- Hirschsprung’s disease: absence of enteric ganglia
- Proctitis: inflammation, urge to defecate, mucus
3. Systemic and Endocrine Causes
- Hypothyroidism: decreased motility
- Diabetes mellitus: autonomic neuropathy
- Pregnancy: progesterone-induced smooth muscle relaxation
- Drugs: opioids, anticholinergics, iron supplements
4. Functional Bowel Disorders
Irritable Bowel Syndrome (IBS-C subtype)
- Abdominal bloating, relief with defecation
- Altering diarrhoea/constipation
- Rome IV diagnostic criteria
- Strong psychological component
- Diagnosis of exclusion
5. Rare or Congenital Causes
- Hirschsprung’s in adults: short segment, misdiagnosed
- Megacolon, megarectum: chronic constipation complication
Key Symptoms and Clinical Signs
| Feature | Clinical Implication |
|---|---|
| Pencil-thin stools | Rectal obstruction |
| Hard masses on DRE | Rectal carcinoma |
| Blood with mucus | Colitis, polyps |
| Absolute constipation + pain | Obstruction/emergency |
Important Diagnostic Features
- Colorectal cancer: weight loss, anaemia, bleeding
- Diverticulitis: alternating pattern, LIF pain
- Hirschsprung’s: no rectal gas on X-ray, megarectum
- Drug-induced: detailed medication history
- IBS: young age, no red flags, functional symptoms
Investigations in Constipation & Bowel Habit Change
| Investigation | What it Detects |
|---|---|
| DRE | Rectal mass, fissure, impaction |
| FBC | Anaemia in CRC, infection |
| Stool culture | Infections, parasites |
| Sigmoidoscopy | Safe, quick diagnosis of L-sided pathology |
| Colonoscopy | Full colon visualisation, biopsy |
| Rectal biopsy | Hirschsprung’s disease |
| Barium enema | Strictures, obstruction (if colonoscopy contraindicated) |
When to Refer or Escalate
- New onset >55
- Evidence of obstruction
- Failure of conservative treatment
- Iron deficiency anaemia
- Significant weight loss
- Unexplained PR bleeding
Management Strategy
General Measures
- Increase dietary fiber and fluids
- Regular toilet habits
- Limit constipating medications
Medical Management
- Bulk-forming: Psyllium
- Osmotic: Lactulose, PEG
- Stimulant: Senna, Bisacodyl
- Enemas: only for severe impaction
Specialist Treatment
- Surgical: for cancer, stricture, rectal prolapse
- Biofeedback for pelvic floor dysfunction
- Psychiatric referral in severe IBS
FAQs
What’s the difference between IBS and colorectal cancer symptoms?
IBS does not cause weight loss, anaemia, or nocturnal symptoms.
How do I know if constipation is an emergency?
If there's abdominal distension, vomiting, and no passage of gas/stool — it's absolute constipation and may indicate obstruction.
Can stress cause altered bowel habits?
Yes—IBS is closely linked to stress and anxiety.
Do iron supplements worsen constipation?
Yes, especially in older adults and women.
Conclusion
Constipation and altered bowel habits are often dismissed as routine discomforts, but they can be the early signs of life-threatening colorectal diseases. Proper evaluation and timely intervention save lives—and quality of life.
