Constipation Causes, Diagnosis & Treatment Options Available

What is Constipation?

Infrequent bowel movements and/or difficulty in bowel movements, often accompanied by straining or a sense of incomplete evacuation.

Classification 

• Primary constipation
• Secondary constipation

Causes of Secondary Constipation

Drugs

• Calcium channel blockers
• Opioids
• NSAIDs
• Calcium

Endocrinopathies

• Hypothyroidism
• Hypercalcemia
• Diabetes mellitus

Neurological Disorders

• Stroke
• Parkinson's disease
• Amyotrophic lateral sclerosis (ALS)

Obstructive Causes

• Carcinoma of the colon
• Rectal cancers

Metabolic Causes

• Hypokalemia
• Hypomagnesemia

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Classification of Primary Constipation

Normal Colonic Transit Time

• Functional constipation
• Increased risk for females, stress, depression, decreased dietary consumption of fibers, and debility
• Increased need for straining

Slow Colonic Transit Time

• Defects in myenteric plexus
• Hirschsprung disease
• Bloating
• Abdominal distension

Anorectal Dysfunction or Dyssynergic Defecation

• Colonic transit is normal, but the rectal sphincter fails to contract correctly
• Rectal pain or fullness
• Need frequent manual evacuation

Martelli's Regimen For Colonic Transit Time

Abdominal X-ray

• 1 capsule containing 20 radioactive markers
• Normally, > 80% of markers are expelled at the end of 5 days
• < 80% expulsion indicative of slow colonic transit time
• It can help identify the affected part of the colon, i.e., the right colon, left colon, or recto-sigmoid region.

Balloon Expulsion Test

• The patient lies in the left lateral decubitus position or squats on a toilet seat.
• A balloon filled with 50 ml of water or air is inserted, and the patient is asked to expel.
• Expulsion in < 2 minutes—normal
• Expulsion in > 2 minutes is indicative of dyssynergia
• Functional abnormality
• Poor response to laxatives

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Approach to Constipation

• 90% of cases are primary constipation.
• A detailed investigation is required if red flag signs are present:
  • Age > 50 years
  • Bleeding per rectum or blood in the stool
  • New-onset constipation
  • Weight loss > 10% of body weight within 6 months

History

Physical Examination

Test Results

Examinations

• Thyroid-stimulating hormone (TSH) test
• Complete blood count
• Electrolytes
• X-ray abdomen

Further Approaches

• If a secondary cause is found: Treat accordingly
• Supplement with fiber and laxatives

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Treatment for Constipation

Approach to Primary Constipation

• PEG compounds-preferred
  • Unabsorbed
  • Not acted upon by bacterial enzymes
• Lactulose
  • Flatulence
  • Partially absorbed

Classification of Laxatives

Bulk-forming Laxatives

• Do not stimulate peristalsis or initiate any biochemical change in the intestinal milieu
• Add bulk to stool, stimulating colonic movement
• Dietary fiber
• Methylcellulose

Osmotic Laxatives

• 1st line agent
• Lactulose
• Polyethylene glycol (PEG)
• Magnesium salts
• Mechanism of action:
  • Osmotically active
  • Attract water from the colon to bulk the stool.

Stimulant Laxatives

• Stimulate colonic peristalsis
• Bisacodyl

Secretory Laxatives

• Increase active secretion of chloride ions into a bowel movement
• An electrical imbalance develops, initiating the pumping of positive ions (sodium) into the lumen.
• There are more sodium and chloride ions in the lumen compared to the colonic cells.
• The osmotic gradient stimulates the movement of water into the lumen.
• Lubiprostone
  • Chloride channel stimulator
• Linaclotide
  • Guanylyl cyclase stimulator

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Functional Constipation

1. Functional Constipation is a type of primary constipation

2. Diagnosis: Rome IV Criteria

Rome IV criteria can also be used for:

1. Functional dyspepsia

2. Irritable bowel syndrome

3. Functional chest pain related to esophageal origin

Differential Diagnosis

Constipation Predominant Irritable Bowel Syndrome (IBS-C)

Criteria for Functional Constipation Diagnosis

The onset of constipation symptoms at least six months before diagnosis.

Below criteria met for the past 3 months

1. Two or more of the following criteria must be present:

• Straining with > 25% defecations
• Lumpy or hard stools with more than 25% of defecation
  • Bristol stool form types 1 and 2
• The sensation of incomplete evacuation with more than 25 % of defecations
• The sensation of anorectal obstruction or blockage with more than 25% of defecations
• Manual maneuvers are required, with more than 25 % of defecations
  • E.g., digital evacuations, support for the pelvic floor
• Fewer than 3 spontaneous defecations per week

2. Loose stools are rare without the administration of laxatives

3. Insufficient criteria for irritable bowel syndrome

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Patient Complaint

• Pain is a rare feature of functional constipation. If there is frequent pain present, it should suggest irritable bowel syndrome.
• There are no red flag signs.
  • Age more than 50
  • Significant weight loss
  • Blood in stool
  • Anemia
  • Fecal occult blood positive

Constipation Management

• Lifestyle modification (includes a good amount of mobility)
• Increased dietary fibers
• Stool bulking agents
• Pharmacotherapy.
  • DOC: Osmotic Laxatives
  • PEG > Lactulose
• 2nd Line Agents
  • Stimulant Laxatives
  • Secretory Laxatives
• Most patients respond well to lifestyle modification

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Important MCQs

A 40-year-old female was evaluated for primary constipation. Colonic transit time was tested. The patient was given a capsule containing 20 radiopaque markers orally. An abdominal X-ray was obtained daily. After 5 days, an X-ray showed 3 radiopaque markers still in the colon. Which type of constipation is the patient suffering from? 

1. Slow transit
2. Normal transit
3. Anorectal dysfunction
4. Rapid transit

Answer: A. Slow transit

• Females have a higher risk of constipation compared to males.

Q2: Balloon expulsion test is used for the diagnosis of 

1. Slow transit constipation
2. Dyssynergic defecation
3. Normal transit defecation
4. Fissure-in-ano

Ans.: B. Dyssynergic defecation

Q3: Which of the following is considered a first-line agent for the treatment of chronic constipation? 

1. Osmotic laxatives
2. Stimulant laxatives
3. Secretory laxatives
4. Any of the above

Ans.: A. Osmotic laxatives

Q4: Mechanism of action of linaclotide: 

1. Chloride channel activator
2. Prokinetic
3. Guanylyl cyclase stimulator
4. 5-HT4 agonist

Ans.: C. Guanylyl cyclase stimulator

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