What is constipation?

Constipation is one of the most common digestive complaints worldwide, with everyone getting constipation at some time in their lives. Though not usually serious, it can nonetheless be uncomfortable and frustrating. In the USA alone, constipation affects two per cent of the adult population, accounting for up to 2.5 million doctor visits annually and medication costs worth millions of dollars.

A local study published in the Singapore Medical Journal in 2000 said there was a prevalence of about 7.3 per cent in those aged 16 years and above.

Constipation is a symptom and not a disease in itself. Constipation occurs when bowel movements become difficult or less frequent. The normal length of time between bowel movements ranges widely from person to person, but generally when movements stop for more than three days, the stools or faeces become harder and more difficult to pass. Patients may experience abdominal bloating, cramping pain or even vomiting.

Although definitions vary, one is considered constipated if there are two or fewer bowel movements in a week, or if one has two or more of the following symptoms for at least three months:

1. Straining during a bowel movement more than 25 per cent of the time
2. Hard stools more than 25 per cent of the time
3. Incomplete evacuation more than 25 per cent of the time

Causes of constipation

There are numerous causes of constipation and it is not always possible to identify a definite cause in each patient. The majority of patients can be managed conservatively and the doctor’s vital role is to identify more serious causes that might require surgical treatment. Causes may include:

• Dietary disturbances (inadequate water intake, too little or too much dietary fibre, disruption of regular diet or routine)
• Inadequate activity/exercise or immobility
• Excessive/unusual stress
• Medical conditions: hormonal (hypothyroidism), neurological (stroke, Parkinson disease), depression, eating disorders
• Medications (antacids containing calcium or aluminium, strong pain medicines like narcotics, anti-depressants, iron pills)
• Pregnancy
• Colorectal cancer

How is the cause of constipation investigated?

Most people do not need extensive testing. Only a small number of patients with constipation have a more serious underlying problem. Symptoms that could point to more serious causes that warrant early attention include:

• Constipation that is a new problem for you.
• Your constipation has lasted more than two weeks.
• You have blood in your stools.
• You are losing weight even though you are not dieting.
• Your bowel movements are associated with severe pain.
• You are more than 50 years of age with a family history of colorectal cancer.

Tests your doctor may perform to diagnose the cause of your constipation include:

• Blood tests if a hormonal imbalance is suspected
• Diagnostic tests for cancer such as scopes (colonoscopy) or imaging (CT-colonography or barium enema) to exclude colorectal cancer.

The vast majority of patients with constipation do not have any obvious underlying illness (secondary constipation) to explain their symptoms, and they suffer from one of two types of functional constipation (primary constipation):

1. Colonic inertia: A condition in which the colon contracts poorly and retains the stools.
2. Obstructed defecation: A condition in which a person excessively strains to expel the stools from the rectum. This may be due to a lack of coordinated anal muscle contractions or structural problems like rectal prolapse or a combination of both.

Nonetheless, these problems can be difficult to manage and can significantly affect one’s quality of life. Occasionally, functional constipation may be part of a more complex pelvic floor disorder. As such, even after excluding more life-threatening causes like cancer, persistent constipation should not be neglected and patients can still benefit from specialist help.

Specialised tests can be performed to better differentiate these two sub-groups.

Treatment for constipation

Treatment has to be individualised and depends on the cause and severity of the constipation. For secondary causes, treatment is directed at the underlying disease (e.g. thyroid hormones for hypothyroidism, surgery for colorectal cancer).

For the primary causes mentioned above, more than one type of treatment may be required to achieve the best outcomes, as defecation (passing stools) relies on a complex chain of events.

Fortunately, the majority of patients will benefit from conservative measures such as dietary modification, tailored medical therapy and pelvic floor rehabilitation. However, when the above measures fail, surgery may offer some relief of symptoms and an improvement in the quality of life.

Treatment options for constipation include the following:

• Pelvic floor rehabilitation exercises (anorectal biofeedback): To retrain the anal muscles to contract effectively in the presence of discoordinated movements.​
• Transanal irrigation: This is a simple procedure that aims to clear the bowel of stools at regular intervals. It is essentially a self-administered water enema that can be taught to patients or their caregivers.
• Neuromodulation (Sacral nerve stimulation/SNS): This minimally-invasive technique involves inserting a fine electrode next to the nerves supplying the anal sphincter muscles and rectum. This can help to modulate colonic contractions in some patients with colonic inertia. (Figures 1 and 2.)
• Surgical repair of any associated rectal prolapse: This surgery (rectopexy) involves supporting the rectum with a mesh and this can be performed using laparoscopy or with robotic assistance. (Figure 3.)
• Surgical removal of the colon (rarely used nowadays, in severe cases of colonic inertia)

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Figure 1. Sacral neuromodulation device

Figure 2. X-ray of a patient with an implanted device

Ref. R14