Constipation

Symptoms

Typical symptoms of constipation include abdominal pain, cramping, bloating, nausea, loss of appetite and straining during bowel movements. In children, as well as infrequent or irregular bowel movements, a child with constipation may also have the following signs and symptoms such as lack of energy, being irritable, foul-smelling wind, soiling clothes and generally feeling unwell. Stools associated with constipation tend to be dry, hard and lumpy and indicated as type 1 or 2 on the Bristol stool chart (Figure 1). The pain and discomfort from chronic constipation and the associated complications can greatly impact a person’s quality of life.

Figure 1: The Bristol stool chart

Causes

Chronic constipation can be classified as functional (or idiopathic) or secondary constipation. Functional constipation occurs without an anatomical or physiological cause. A person with functional constipation may be healthy, yet has difficulty defecating leading to believe it maybe neurological, psychological or psychosomatic. It is diagnosed by the exclusion of a pharmacological or medical cause. Secondary constipation is generally caused by a drug or medical condition.

 

Medical conditions

Conditions known to cause constipation include disorders that alter the functionality of the GI tract, such as Crohn’s disease and ulcerative colitis. Conditions such as Parkinson’s disease and multiple sclerosis can also have direct effects on the nerves that control bowel function resulting in uncoordinated contraction of abdominal muscles and inhibiting the passage of stools. Secondary constipation can occur in patients with diabetes and hypothyroidism due to weight gain and reduced mobility associated with such conditions.

 

Medications

 

1. Antihypertensives (diuretics, clonidine, calcium channel blockers)

If clinically appropriate switch to less constipating medicines such as ACE inhibitors, beta-blockers or          angiotensin-II receptor antagonists. Diuretics can cause constipation due to less available fluid.                  Laxatives such as docusate can act as a surfactant and softener or osmotic laxatives can be used to            increase the amount of water in the large bowel.

2. Tricyclic antidepressants (e.g. amitriptyline)

Serotonin and noradrenaline re-uptake inhibitors are alternatives less associated with constipation.

3. Antimuscarinics (procyclidine, oxybutynin)

These agents decrease GI motility and therefore a stimulant laxative may be necessary.

4. Antiparkinsonian medicines (levodopa, dopamine agonists, amantadine)

5. Iron supplements

Intravenous iron could be used, or a laxative may be co-prescribed.

6. Aluminium-containing agents (sucralfate and antacids)

Proton pump inhibitors could be used instead.

7. Analgesics (Opioids and NSAIDs)

Opioids cause constipation by decreasing peristalsis and enhancing the resorption of fluids and                  electrolytes. A stimulant laxative e.g. senna is recommended at the lowest effective dose. Osmotic            laxatives are also effective for this type of constipation and are often better tolerated than stimulant          laxatives which can cause abdominal cramping.

 

Other causes of constipation

Pregnancy: Constipation is mostly experienced during the early stages of pregnancy as a result of hormonal changes. During pregnancy more progesterone which acts as a muscle relaxant is produced. As food moves through the gut, the gut wall muscles contract and relax in a rippling wave-like motion. The increased progesterone interferes with the contraction of the bowel muscles making it harder for waste products to move along.

In young children: About one in three parents report constipation at some time in their child’s life. Poor diet, fear about using the toilet and poor toilet training can all be responsible.

 

Diagnosis

Doctors define constipation in a number of ways:

• opening the bowels less than three times a week
• needing to strain to open bowels on more than a quarter of occasions
• passing a hard or pellet-like stool on more than a quarter of occasions

When assessing a patient for constipation, possible causes such as medication and comorbidities along with diet, level of exercise, recent changes in routines are taken into consideration. A physical or internal rectal examination may sometimes be performed to confirm that faecal masses are palpable abdominally or perianally. Patients with any red flag symptoms (unexplained weight loss, rectal bleeding, family history of colon cancer or inflammatory bowel disease or signs of obstruction) should be referred to a specialist for further investigation. The Rome III diagnostic criteria (Figure 2) can be used to classify functional gastrointestinal disorders and may be useful when functional constipation is suspected and contributing medicines or medical conditions have been excluded.  

Figure 2: Rome III diagnostic criteria

Treatment and Prevention

Lifestyle advice can help to prevent and alleviate constipation. In many cases, constipation may be as a result of poor diet and lack of exercise. Patients should be encouraged to increase fibre in their diet and fluid intake before trying laxatives.

• Fibre increases the bulk and plasticity of stools which encourages movement through the colon. It is advised to consume at least 18 to 30g of fibre (fruit, veg, pasta, rice) each day. Also adding some bulking agents such as wheat bran to your diet will contribute to softer stools and allow to pass through the bowel easier.
• Increase fluid intake. It is recommended for adults to drink at least 2 litres of water each day. Child 1 to 3 years 900mls per day, 4 to 8 years 1200mls per day and 9 to 13 years 1800mls per day for boys and 1600mls per day for girls.
• Daily walk/run. There is little evidence that exercise can increase gut motility however one study found that women who report physical activity of once a week or more were significantly less likely to report constipation. Individuals who lead sedentary lives are more likely to get constipated.
• Toilet routines. As a rule, it is best to try going to the toilet first thing in the morning or about 30 mins after a meal. This is because the movement (propulsion) of stools in the lower bowel is greatest in the mornings and after meals. ‘Bowel training’ with kids can be useful. Ask your child to sit on the toilet four times a day after meals for five minutes, even if nothing happens. Maintaining a good toilet position using a footstool will also aid the passage of stools (Figure 3).

   

Figure 3: Toilet position

Pharmacological treatment may be required if lifestyle changes do not fully alleviate symptoms of constipation. The NICE guidelines advices that prescribing of laxatives for adults are limited to the short-term treatment of constipation when dietary and lifestyle measures proved unsuccessful or if there is an immediate clinical need.

Laxatives

• Bulk-forming laxatives (e.g. ispaghula husk, methylcellulose, sterculia) They increase faecal mass through water binding which stimulates peristalsis. This class of laxative usually takes two to three days to be effective. Plenty of fluids must be consumed with this type of laxative and not advised to take before bedtime.
• Osmotic laxatives (e.g. macrogols, lactulose) If stools remain hard after taking a bulk forming laxative, osmotic laxatives maybe advised instead. They work by drawing fluid into the large bowel from elsewhere in the body or retaining the fluid consumed with the medicine. It is advised to drink plenty of fluids when taking this laxative to prevent dehydration. As like bulk forming laxatives, they take two to three days to become effective.
• Stimulant laxatives (e.g. senna, bisacodyl) They are used generally on a short-term basis. They improve intestinal motility via muscle contractions and reduce water loss from the faeces keeping the stool soft. They usually start to work within 6 to 12 hours. A potential unpleasant side effect of stimulant laxatives is abdominal cramping due to the increased muscle contractions in the gut wall.
• Faecal softeners (e.g. docusate) They act by lowering the surface tension of the stool allowing water to penetrate the dry faeces and increase faecal mass size stimulating peristalsis.

 

Faecal compaction occurs when hard dry stools collect in the rectum causing an obstruction. Faecal compaction may initially be treated with a high dose of osmotic laxative macrogol followed by a stimulant laxative days later. If this combination is not successful, a suppository (e.g. bisacodyl or glycerol) or mini enema (e.g. docusate or sodium citrate) may be administered.

 

Complications of chronic constipation

1. Haemorrhoids: Excessive straining to pass stools can lead to developing haemorrhoids.
2. Severe faecal impaction can lead to several other complications such as swelling of the rectum, loss of sensation in and around the anus, faecal incontinence and anal bleeding.
3. Rectal prolapse is a protrusion of the lower intestine through the anus due to repeated staining during bowel movement.
4. Anal fissures: The forced passage of hard stools causes small tears through the lining of the anal canal.
5. Psychological effects: Faecal incontinence in children can affect children psychologically making them feel embarrassed and upset. It is important that parents and their support network are compassionate and understanding when dealing with this condition in children.

 

“The NICE guidelines advises that prescribing of laxatives for adults are limited to the short- term treatment of constipation when dietary and lifestyle measures proved unsuccessful or if there is an immediate clinical need.”

 

References available upon request.