Irritable bowel syndrome (IBS) is characterised by a mixture of symptoms that are believed to be due to a disorder of intestinal motor function.

It is the commonest condition seen by gastroenterologists.
The normal gut moves food along the gut through muscular contractions, known as propulsion. There are also areas of hold-up, known as segmentation).

The combination of propulsion and segmentation is called peristalsis. You are completely unaware of it when it is working normally.

The control of peristalsis is complex. The best way to regard IBS is as a loss of coordination of these muscular contractions.

In addition, there is evidence that patients with irritable bowel syndrome have increased sensitivity to stimuli arising within the gut.

As well as the intestinal symptoms, psychological factors are often involved. This is not to say these symptoms are not real (they are), but IBS is often the outcome of a complex interaction between psychological and physical factors.

The symptoms of IBS vary and may occur at any age. They most commonly start in late teenage years or early adulthood.

The symptoms will depend on which parts of the gut are involved. There is often overlap between areas of the gut. Some people may experience problems in only one part of the gut, others in several. Symptoms can also vary over time.

Oesophagus
A sensation like a golf ball in the throat between meals which does not interfere with swallowing (globus).
Heartburn - burning pain often felt behind the breastbone.
Painful swallowing (odynophagia), but without hold-up of food.
Sticking of food (dysphagia) - this requires investigation.

Stomach
Non-ulcer dyspepsia (symptoms suggestive of a stomach or duodenal ulcer, but which has not been confirmed on investigation).
Feeling full after small meals. This may reach the stage of not
being able to finish a meal.
Abdominal bloating after meals.

Small bowel
Increased gurgling noises which may be loud enough to cause social embarrassment (borborygmi).
Abdominal bloating which may be so severe that women describe themselves as looking pregnant.
Generalised abdominal tenderness associated with bloating.
Abdominal bloating of both types usually subsides overnight and returns the following day.

Large bowel
Abdominal bloating of both types usually subsides overnight and returns the following day.
Right-sided abdominal pain, either low, or tucked up under theright ribs. Does not always get better on opening the bowels.
Pain tucked up under the left ribs (splenic flexure syndrome). When the pain is bad, it may enter the left armpit.
Variable and erratic bowel habits alternating from constipation to diarrhoea.
Increased gastro-colic reflex. This is an awakening of the childhood reflex where food in the stomach stimulates colonic activity, resulting in the need to open the bowels.
Severe, short stabbing pains in the rectum, called proctalgia fugax.

During an addisonian crisis, low blood pressure, low blood glucose, and high levels of potassium can be life threatening.

During an addisonian crisis, low blood pressure, low blood glucose, and high levels of potassium can be life threatening.