Causes
of constipation
To understand
constipation, it helps to know how the lower part of the
gut (colon, large bowel) works. As food moves through it,
the colon absorbs water while forming waste products. The
waste products are the ‘stool’ (faeces). Muscle
contractions in the colon push the stool towards the rectum,
which is the last section of the bowel before the anus
(back passage). By the time the stool reaches the rectum,
it is almost solid because most of the water has been absorbed.
The hard
and dry stools of constipation occur when the colon absorbs
too much water. This happens because its muscle contractions
are slow or sluggish, causing the stool to move through
it too slowly.
The following
questions will help you to work out the reason for your
constipation.
- Are
you really constipated? (See checklist in the previous
section.)
- Are
you taking enough fluids and fibre in your diet? In northern
climates, dehydration is not usually a problem, but in
hot climates, it can cause dry stools that are difficult
to pass.
- Do
you take enough exercise?
- Are
you taking any medicines that can cause constipation
(see below)?
- Are
you allowing enough lavatory time to defecate?
- Has
there been any change in your lifestyle? Has your job
or personal relationships become more demanding?
- Are
you depressed? Nerves link the brain to the gut. Reduced
activity of these nerves in depression affects the muscle
activity of the bowel and results in constipation in
some people.
- Do
you have a frequent desire to defecate, then strain to
pass a few small pellets and leave feeling there is still
more to come? This is typical of the irritable bowel
syndrome (see useful
contacts).
- After
straining for some time, does the back passage seem to
bulge as the stool comes halfway through? This feeling
often occurs with piles (haemorrhoids).
- Do
you have a painful condition, such as piles (haemorrhoids)
or anal fissure? If passing
faeces is painful, constipation is a likely result.
- If
you are a women, do you have to put a finger in your
vagina to help pass the stool from the back passage?
This probably means you have a rectocele, a weakness
in the supporting tissues between the vagina and rectum.
- If
you are a women, did the constipation start after childbirth
or after hysterectomy? Hysterectomy may sometimes damage
the delicate nerve fibres connected to the bowel.
- Have
you gained weight and tend to feel the cold, maybe with
dry or thinning hair? You might have an underactive thyroid,
which can also cause constipation.
- Do
you have any other symptoms?
- Are
you pregnant? About 1 in 3 pregnant women has constipation,
probably because of the hormone progesterone. The best
way to deal with it is to take extra fibre in your diet.
- Have
you recently stopped smoking? Almost 1 in 10 quitters
experience constipation (Addiction 2003;98:1563–7).
Check
your medicines
Some medicines can cause constipation. Common culprits are:
- pain-killers
or cough medicines containing codeine
- antacids
(for indigestion) containing aluminium or calcium.
- iron
tablets
- some
antidepressants (tricyclic and monoamine oxidase inhibitor
types) and tranquillizers
- some
drugs for Parkinson’s disease and for epilepsy
(Parkinson’s disease can itself cause constipation)
- some
diuretic drugs (for high blood pressure or heart failure)
Obviously,
you should not stop a medicine that has been prescribed
for you
just because it is making you constipated – it could be an important
medication for you, so discuss it with your family doctor.
