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Constipation
Constipation

Constipation

Constipation is defined on the basis of excessive straining, incomplete evacuation of faeces, failed/lengthy attempts at defecting, hard stools with less frequency.

🏘 ⚠️ Epidemiology and risk factors

It is a global, common issue with almost 40% of men and 50% of women report of straining on more than 1 in 4 occasions.

It is more common in women (2.2:1).

Other risk factors that increase its prevalence are:

  • Reduced fibre intake
  • Sedentary lifestyle
  • Female
  • Age >65
  • IBS
  • Opioid use
  • Functional dyspepsia
  • Black ethnicity - 2x higher in black patients.
  • Low SES
  • Nursing home resident
  • GI motility disorders
  • Dehydration
  • Psychosocial problems - keep safeguarding in mind.

Pathophysiology

Just a quick recap on the anatomy and physiology of the bowel movements:

Our colon contracts in 2 way other than regular peristaltic movements:

  1. Segmented contractions - occurring most of the time. It is used to mix contents and retain material. The contractions move the chyme in both directions, as opposed to peristalsis which moves causally.
  2. Gastro-colic response - a physiological reflex controlling motility of the GI tract following a meal. It allows for space to be made in response to the new food that is incoming.

Let’s also look at our enteric nervous system (ENS) which is a subdivision of the PNS that is located between the linings of the GI tract and is made of 2 plexuses:

  1. Myenteric (Auerbach’s) plexus - located between the circular and longitudinal layer. It increases gut tone and controls the velocity + intensity of contractions.
  2. Submucosal (Meissner’s) plexus - located in the submucosal layer. It is responsible for secretions and absorption as well as controls local muscle movements.

The PSNS stimulates the enteric nervous system while the SNS inhibits it. There are also pacemaker cells of the GI tract known as interstitial cells of Cajal (ICC) which also mediate peristaltic contractions.

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There are 3 types of primary constipation to consider:

  1. Slow transit constipation (STC) - this is when we have myopathy (dysfunction) of the colonic smooth muscle or neuropathy, or both.
  2. Dyssynergia - an acquired behavioural disorder in which there is a paradoxical contraction or insufficient relaxation of the pelvic floor muscles when attempting to defecate.
  3. Irritable bowel syndrome-constipation (IBS-C) - we will go into this further when discussing IBS.

There are a huge number of causes of secondary constipation such as:

  • Metabolic disturbances
    • Hypercalcaemia
    • Hypothyroidism
    • Diabetes mellitus
  • Iatrogenic causes
    • Opiates
    • CCBs
    • Antipsychotics
  • Neurological disorders
    • Parkinsonism
    • Spinal cord lesions
  • Colonic problems
    • Stricture
    • Cancer
    • Anal fissure
    • Proctitis

😷 Presentation

  • Infrequent stools - <3 defecations per week according to the Rome IV criteria.
  • Sensation of incomplete evacuation
  • Excessive straining
  • Hard stools - may cause rectal bleeding as a result.
  • Rabbit dropping stools - indicates dehydration.
  • Abdominal pain
☝
Digital rectal exam findings:

The obvious finding of stool should be followed up by asking the patient if they were aware of its presence as often chronically constipated patients develop rectal hyposensitvity and may lose the sensation of needing to open their bowels this is an issue as it may lead to faecal impaction and thus worsening rectal hyposensitivity in the future.

The consistency of the stool should also be noted.

Other findings may include: a stricture, spasm, tenderness, mass, blood or a rectocele (rectum prolapsing into the posterior vagina). Anorectal lesions may also be noted.

Investigations

🥇
1st line investigations to order for chronic constipation:
  • FBC - looking for secondary causes of constipation. Iron-deficiency anaemia may be suggestive of a secondary cause.
  • TFTs - looking for hypothyroidism as a secondary cause. A decreased TSH would be suggestive of this.
  • Serum electrolytes, calcium, magnesium - hypercalcaemia, hypomagnesaemia, hypokalaemia may suggest a secondary cause but usually these values are not deranged.
  • Blood glucose - as DM may be a concern of secondary causes.
  • Abdominal X-ray - assessing for faecal impaction or rectal masses. It may be done with a barium enema to improve visualisation.
📷
Imaging:

Imaging is not always done but there are plenty of options available to consider:

  1. Defecography - we evaluate the anorectal angle at rest and also during straining, perineal descent, anal diameter and assessing for rectocele.
  2. MR defecography - can evaluate the pelvic floor anatomy. Can also be used to assess rectocele and enterocele.
  3. ⭐️ Colonscopy - may be indicated if there is rectal bleeding, IDA, weight loss obstructive symptoms, rectal prolapse, >50 years old who have not had CRC screening.
  4. Anorectal/colonic manometry - looking for neuropathy and dyssynergic causes.

🔢 Criteria

The Rome IV criteria is used IBS-constipation but also for functional constipation.

2 or more of the following should be present to diagnose functional constipation and opioid-induced constipation:

  1. Straining during at least 25% of defecations.
  2. Lumpy/hard stools in 25% of defecations.
  3. Sensation of incomplete evacuation at least 25% of defecations.
  1. Sensation of anorectal obstruction/blockage at least 25% of defecations.
  2. Manual manoeuvres to facilitate at least 25% of defecations.
  3. <3 defecations per week.

🧰 Management

⏳
<3 months of symptoms (acute):
  1. Treat underlying cause - treat secondary constipation through management of the cause.
  2. + Dietary and lifestyle advice:
    1. Increase dietary fibre - fruits, vegetables, high-fibre breads and cereals (wholegrain and wholemeal options).
    2. Increase daily fluid intake
    3. Increase calorie intake if calorie intake is low.
    4. Increase exercise - especially if patient is sedentary.
  3. Laxatives - bulk laxatives and/or stool softeners are preferred as first-line options. Stool softeners are better for patients with hard stool and who are straining. Bulk laxatives are better for patients who have occasional loose stools in between the episodes of constipation.
    1. Stool softeners - may cause a bitter taste in mouth, nausea, diarrhoea and cramping.
      1. Docusate sodium - 100mg OD/BD orally.
    2. Bulk laxatives - may produce excessive gas → flatulence and bloating.
      1. Ispaghula husk
      2. Methylcellulose
  4. Prunes - a natural alternative that has shown to be as effective as Isphagula husk.

🚨 Faecal impaction

We need to implement evacuation measures such as: enemas, suppositories, PEG solution, stimulant laxatives or disimpaction. This depends on the patient characteristics and a specialist management would be needed.

💊
Opioid-induced constipation:

In the myenteric plexus, there are u-opioid receptors which inhibit parasympathetic stimulation → decrease peristalsis. As a result a side-effect of opioids is constipation. Loperamide is a u-opioid agonist that has no analgesic activity and is specifically used to treat diarrhoea.

Conversely we can treat opioid-induced constipation with methylnaltrexone which is a peiripheral opioid receptor antagonist that does not cross the BBB

Adverse effects include: abdominal cramping, flatulence.

⌛
>3 months of symptoms (chronic):
  1. 🥇 Treatment of underlying cause
  2. 🥇 Dietary and lifestyle advice
  3. 🥇 Bulk laxatives, stool softeners and/or prunes
  4. 🥈 Osmotic laxatives
    1. Lactulose
    2. Macrogol
  5. 🥉 Stimulant laxatives
    1. Senna
    2. Bisacodyl

If refractory to these laxatives, we can test for dyssynergia:

If positive → biofeedback can be effective. This involves training to improve coordination of the abdominal and anorectal muscles to aid defecation.

If negative → referral to specialist centre which may then involve surgery but will require a more detailed assessment initially.