4. Constipation

 

  

Overview

Pathophysiology

  • Chronic constipation results from a combination of:
    • Slow colonic transit.
    • Pelvic floor dysfunction (e.g., dyssynergic defecation).
    • Altered gut microbiota.
    • Potential psychosocial factors contributing to the perception of symptoms.
  • Rome III for Functional Constipation:
    • Rarely has loose stools without laxatives.
    • Doesn’t meet criteria for IBS.
    • At least two of:
      • <3 bowel movements per week.
      • Manual maneuvers >25% of the time.
      • Hard/lumpy stools >25% of the time.
      • Incomplete evacuation >25% of the time.
      • Sensation of obstruction >25% of the time.
      • Straining to defecate >25% of the time.
  • Transit Types:
    • Normal Transit: Presents as incomplete evacuation.
    • Slow Transit: Characterized by lack of urge to defecate, infrequent bowel movements, poor response to fiber and laxative therapy. Often shows normal resting motility but absent postprandial peristalsis. Diagnosed via colonic transit study (e.g., 6/24 markers remaining at 24 hours).

Diagnostic Criteria

UK NICE Guidelines (CKS):

  • Initial Evaluation:
    • Exclude secondary causes with:
      • CRP, ESR, FBC, and calcium levels.
      • Thyroid function tests (hypothyroidism).
    • Assess for red flags:
      • Rectal bleeding, unexplained weight loss, anemia.
      • Symptoms onset after 50 years of age.
      • Family history of colorectal cancer.
  • Chronic Constipation: Defined as symptoms lasting >6 weeks.

European ESNM Guidelines:

  • Chronic constipation in adults characterized by:
    • Fewer than three spontaneous bowel movements per week.
    • Straining, hard stools, or incomplete evacuation >25% of the time.
    • Symptoms persisting for at least 3 months with onset at least 6 months prior.

Clinical Features

  • Symptoms:
    • Infrequent defecation (<3 per week).
    • Straining, hard or lumpy stools (Bristol Stool Scale types 1-2).
    • Sensation of incomplete evacuation.
    • Abdominal bloating, discomfort.
  • Red Flags (require further evaluation):
    • Rectal bleeding or mucus discharge.
    • New-onset symptoms in older adults.
    • Severe persistent pain or unresponsive symptoms.

Diagnostic Workup

First-Line Investigations:

  • History and Examination: Identify functional vs organic causes.
  • Baseline Tests:
    • CRP, ESR, FBC, TSH.
    • Colonoscopy in patients with alarm symptoms or >50 years.
  • Imaging and Tests for Refractory Cases:
    • Anorectal manometry for pelvic floor dysfunction.
    • Defecography (MRI or barium) for structural abnormalities.
    • Colonic transit studies (e.g., radiopaque markers).

Pelvic Dyssynergia Classification:

  1. Type 1: Adequate propulsion (>40 mmHg), paradoxic contraction of anal sphincter.
  2. Type 2: Inadequate propulsion, paradoxic contraction of anal sphincter.
  3. Type 3: Adequate propulsion, absent or partial (<20%) relaxation of sphincter.
  4. Type 4: Inadequate propulsion, absent or partial (<20%) relaxation of sphincter.

Management Strategies

General Approach:

  1. Patient Education:
    • Normalize bowel habits and avoid excessive straining.
    • Encourage use of a footstool during defecation to optimize anorectal angle.
  2. Lifestyle and Dietary Modifications:
    • Adequate hydration and regular physical activity.
    • Dietary fiber intake: Aim for 20-30g/day, from fruits, vegetables, or supplements (psyllium).
    • Avoid excessive caffeine and alcohol.

Pharmacological Management:

  1. First-Line Therapies:
    • Bulk-forming laxatives (e.g., psyllium, ispaghula husk).
    • Osmotic laxatives (e.g., polyethylene glycol (PEG), lactulose).
  2. Second-Line Therapies:
    • Stimulant laxatives (e.g., bisacodyl, senna).
    • Secretagogues:
      • Linaclotide (guanylyl cyclase-C receptor agonist).
      • Lubiprostone (prostaglandin E1 derivative activating chloride type-2 channels).
    • Prucalopride (5HT-4 agonist).
  3. Management of Specific Cases:
    • Opioid-Induced Constipation (OIC):
      • First-line: Senna (15 mg prophylaxis ON, 15 mg BD for treatment) with fruit, fiber, and fluids.
      • Second-line: Naloxegol or methylnaltrexone for persisting symptoms (4 out of the last 14 days despite laxatives).
    • Pelvic Floor Dysfunction:
      • Biofeedback therapy for dyssynergic defecation.

Refractory Cases:

  • Consider combination therapy and consultation with a gastroenterologist.
  • Investigate for underlying disorders (e.g., Hirschsprung's disease, rectocele).

Additional Management:

  • Hypothyroidism:
    • Suspect in cases with hypothermia, blunted tendon reflex, confusion, raised TSH, low free T4.
    • May reveal raised MCV, low sodium.
  • Pseudo-Obstruction:
    • Correct electrolytes (magnesium, potassium, phosphate).
    • Rule out obstructing rectal tumors.
    • Trial neostigmine before endoscopic decompression.
  • Distal Intestinal Obstruction Syndrome:
    • Characterized by acute or incomplete obstruction of the ileocecum by inspissated intestinal contents.
    • Symptoms: Cramping RLQ abdominal pain with acute or intermittent onset becoming progressively severe. On examination, a mass may be palpated in the RLQ.
    • Management: Hydration (oral/NG if tolerated), gastrografin (can be given as enema), NAC to loosen plugs (better evidence for gastrografin).

Emergencies:

  • Volvulus:
    • Flexible sigmoidoscopy for decompression.
    • Radiological sign: Coffee bean sign pointing away from obstruction site.

Table 1: Pharmacological Options for Constipation

Drug Type

Examples

Mechanism of Action

Bulk-forming

Psyllium, Methylcellulose

Increase stool mass, stimulate peristalsis

Osmotic

PEG, Lactulose

Draw water into the bowel

Stimulant

Bisacodyl, Senna

Stimulate intestinal motility

Secretagogues

Linaclotide, Lubiprostone

Increase intestinal fluid secretion

PAMORAs

Naloxegol, Methylnaltrexone

Block opioid receptors in gut

References

  1. NICE. Constipation: Diagnosis and Management. Clinical Knowledge Summaries. Link
  2. European Society of Neurogastroenterology and Motility. Guidelines on Chronic Constipation. PDF Link
  3. European Medicines Agency (EMA). Guideline on Evaluation of Medicinal Products for Chronic Constipation. Link
  4. Functional constipation study. PMC Link

Images:

 Colon transit time radiographs:

Volvulus:

    • Sigmoid volvulus with coffee bean sign: Example