I have constipation despite a high-fibre diet. What's wrong with me?

A change in bowel habit, even if it occurs slowly over time, should prompt investigation, because it can be caused by abnormalities in the colon that narrow the passage of stool, as well as a decline of the function of the colon to transport stool.

Q: I am a 73-year-old man and have been suffering from constipation over the years.

I eat fruits and vegetables and I drink about 2 litres of water daily in addition to coffee and other beverages.

I have also been drinking 150ml of prune juice twice a day - once in the morning and once before retiring at night.

I tried taking a high-fibre product, but it does not seem to work.

I have to resort to taking medication when I do not move my bowels after three days.

Of late, my constipation has been getting worse and I have had to use suppositories (tablets inserted into the anus) to help me move my bowels.

I can feel that my stool is hard and it comes out in lumps each time.

Is there any advice or help you can give to improve my situation?

A: A change in bowel habit, even if it occurs slowly over time, should prompt investigation, because it can be caused by abnormalities in the colon that narrow the passage of stool, as well as a decline of the function of the colon to transport stool.

Some tests can be done to evaluate your colon for lesions that obstruct or narrow the passage.

They include colonoscopy, during which the doctor examines the large intestine using a flexible tube with a small camera inserted through the anus, and computed tomography (CT) colonography, which involves performing a CT scan of the colon.

In some cases, the doctor may carry out a contrast enema X-ray, which is an X-ray examination of the colon after barium - which acts as a dye to highlight abnormalities on the X-ray image - has been pumped in.

The function of the colon to transport stool can be assessed via a colonic transit study, which is an abdominal X-ray taken five days after the patient has ingested some small markers in tablet form.

These markers can then be seen on the X-ray image and can give important information about how long the stool took to travel through the colon.

This can indicate whether a delay is due to the colon working very slowly in general (colonic inertia) or due to a problem near the outlet when the person is trying to pass motion (functional outlet obstruction).

The doctor can then recommend the appropriate treatment for the problems diagnosed.

Dietary fibre plays an important part for colonic function, as it increases stool bulk and draws water into the colon, thereby softening the stool and making it easier to be passed out.

Too much fibre, however, can have the opposite effect and can lead to constipation, especially if insufficient fluid is consumed.

A high-fibre diet can also lead to significant intestinal gas production, bloating and flatulence.

The recommended daily fibre intake for an adult is 20 to 35g.

Here are some examples of the amount of fibre present in food: A small bowl of cooked white rice contains 1g of fibre and an apple contains 2g of fibre.

The recommended daily fluid intake for an adult is 1.5 to 2 litres.

Fluids that contain caffeine increase the amount of urine produced and passed out of the body and should therefore be consumed only in small quantities.

Fluids recommended to aid digestion are water, fruit juice and other beverages that do not contain caffeine.

Dr Bettina Lieske
Associate consultant at the division of colorectal surgery at the National University Hospital

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