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Constipation and Obstructed Defaecation


Constipation is a symptom that can mean a number of different things. It is used by some to indicate infrequent passage of stools but can also mean difficulty passing stools, the passage of hard stools, a feeling of blockage or a feeling of incomplete evacuation. The latter of these symptoms are often referred to as obstructive defaecation.

There is a large variation in the frequency of bowel motions. Anywhere from three times per day to three times per week is within the normal range. It is a common misconception that one must defecate daily.


Primary causes include:

  • Slow transit constipation – a disorder of colonic peristalsis
  • Obstructive defaecation – anatomical disorders such as a rectocoele or rectal intussusception/prolapse and functional disorders such as anismus.
  • Irritable bowel syndrome (IBS) – constipation associated with abdominal pain or bloating.

Secondary causes include:

  • Lifestyle factors – low fibre, poor diet, sedentary lifestyle, old age.
  • Endocrine conditions – diabetes, hypothyroidism, hypercalcaemia.
  • Neurological conditions – dementia, Parkinsons, MS, spinal injuries.
  • Pregnancy.
  • Medications –painkillers (opiates – codeine, panadeine, endone), antidepressants, iron.
  • Mechanical blockage – colonic tumours, diverticular disease.


The underlying cause is usually apparent following history and examination. Secondary causes can be ruled out by blood tests – blood sugar, thyroid function tests, calcium and others.

If there has been a recent change in bowel habits with constipation (especially in patients > 40 years old), a colonoscopy should be performed to rule out sinister causes such as bowel cancer.

In cases that are not responsive to lifestyle changes and laxatives, more specialised tests can be performed. A nuclear medicine colonic transit study can be used to diagnose slow transit constipation. Anorectal physiology studies and a defaecating proctogram can be used to investigate causes of obstructive defaecation.


Constipation often resolves with simple measures. The majority of Australians do not get enough dietary fibre. The recommended amount of fibre per day is 25-30g. Common foods that are high in fibre include cereals, grains, fruit and vegetables. It is also important to drink 1.5 – 2 L of water every day and to remain active with regular exercise. Fibre supplements can be very helpful in those lacking fibre in their diet. Examples include generic psyllium husk, bran flakes, Metamucil and benefiber. All these have similar benefits.


There are a huge number of laxatives on the market. The majority are completely safe even when used over a long period. Many people are afraid of laxative dependence. Usually, it is the bowel which is ‘slow’ intrinsically rather than the fault of the laxative. There is considerable variation in the efficacy of laxatives between individuals ie a laxative may be greatly effective in one person but have no or little effect in another. The common classes of laxatives include:

  • Osmotic laxatives – movicol, lactulose, osmolax, clearlax.
  • Stool softeners – coloxyl.
  • Stimulants – senna, bisacodyl (ducolax).


There are some medications used to treat constipation including the enterokinetic prucalopride(Resotrans).


Surgery is reserved for severe cases of obstructed defaecation when an anatomical defect is found and conservative measures have failed.

In highly selective cases of severe slow transit constipation a total colectomy and ileorectal anastomosis can be performed. This has a reasonably high success rate in the short and medium terms but less certain outcomes in the longer term.

  • Prince of Wales Private Hospital
  • The Royal Hospital For Women Foundation
  • Colorectal Surgical Society of Australia and New Zealand
Randwick Rooms

Prince of Wales Private
Suite 17, Level 7
Barker Street
Randwick NSW 2031

Phone: (02) 9099 4400
Fax: (02) 9650 4924

Double Bay

Level 1
451 New South Head Rd
Double Bay NSW 2028
(Opposite Woollahra Library Double Bay)

Phone: (02) 9096 3133
Fax: (02) 9096 3199

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