Irritable bowel syndrome

Prevalence in western societies is

10-15%.

IBS is relatively common amongst western societies. It's main symptoms are

A change in bowel habits and abdominal pain that's relieved upon defecation.

IBS is further classified into two subdivisions

Diarrhoea predominant (IBS-D) or constipation predominant (IBS-C).

Twin studies showed that

IBS was twice as likely in monozygotes.

Plasma serotonin levels were found to be lower in

IBS-C than IBS-D and controls.

Peak plasma levels were higher in

IBS-D than in IBS-C and controls.

Diagnosed using the

Rome 2 and Rome 3 criteria. It is a syndrome of exclusion.

The Rome criteria is measured by

abdominal pain/discomfort for a certain amount of days in a specific period of time and a change in frequency or texture of stools. Pain and bloating, mucus, relief with defecation are also indicators.

Studies also showed that IBS patients seemed to have problems with

anticipation, distraction and experience of pain. They had greater activation of anterior cingulate cortex.

Alarm indicators

are used to exclude IBS. These include being over 50, rectal bleeding, nocturnal symptoms, weight loss and recurrent vomiting.

Diet

can also be changed to aid symptoms of IBS. Fibre seems to worsen symptoms in most.

Each person will all have a different

cause of IBS (genetics, diet etc).

IBS has a high

economic impact. Patients pay nearly double the annual medical costs in the US than controls.

Probiotics are widely seen as

effective but the magnitude of benefit and the most effective species and strain is unknown.

Another study found that

fibre, antispasmodics and peppermint oil were more effective in trials than placebos.

It is known as a

functional GI disorder. Which means it is a recurring problem with no atomical or biochemical cause.

IBS seems to be increased in people who

had previously suffered from a salmonella infection. A change in immune function may contribute to development.

The pathophysiology shows that IBS is not

immune related unlike IBD. It may be psychological and not actually a real existing condition (40% placebo rate).

Peppermint oil

is a known antispasmodic and has effects on smooth muscle. It can reduce colonic contractability and pain due to it blocking calcium channel activity.

Ispaghula husk

is a type of fibre that was found to increase transit time in IBS-C (Contradictory).

There is currently no specific treatment for IBS, just

management of symptoms.

Prevention of

muscle spasms also helps. These medicines include anticholinergics and antispasmodics.

Mechanisms may involve changes in the

nervous system function, gastric motility and other factors.

IBS is classed as

non-organic as it can not be measured or observed (e.g. via colonoscopy unlike IBD, which is organic).

There is no clear pathology and it's mechanisms are

poorly understood.

Mechanisms of probiotics include

promotion of immunoregulation. Changes in visceral hypersensitivity, serotonin, epithelial receptor function and CNS activation. Reducing inflammation, promoting healthy gut flora and enhanced intestinal barrier function and mobility.

Antispasmodics

reduced colonic contraction and transit time, therefore pain and stool frequency (Hyoscine in particular).

Fibre, antispasmodics and peppermint oil are all

safe and available over the counter but are overlooked due to newer, more expensive drugs.

Biffidobacterium

seem to be more effective in studies than lactobacillus species. Lactobacillus did not seem to improve bloating or defecation whereas biffidobacterium did, as well as abdominal pain.

There may be dysregulation of

serotonin in different types of IBS.

Genetic factors play a part as

someone with a family member how has IBS will often describe themselves as having abdominal pain or bowel trouble. Genetics or environment/education?

Pharmacological aids

such as alosetron and tegaserod are used. These are serotonin receptor antagonists, but are not readily available due to them having adverse side effects.

IBS-D patients

tend to have a reduced colon diameter and accelerated small bowel. (Antispasmodics can help this).

Serotonin is heavily involved in brain function and in

the GI tract and gastric motility involvement.

Treatment is

the management of symptoms. Education of the syndrome and psychological treatment.

IBS cannot be seen in

the organs unlike IBD during a colonoscopy. The vast majority also have no inflammation. Those that do = mild IBD?

Probiotics have also been used

to target the gut microflora. They help to increase colonic transit time but more than 1 per day is needed. They target lactic acid bacteria and are composed of lactobicillus and biffidobacterium species.

IBS is also understood for it's

visceral hypersensitivity. The main symptom is pain. Studies show IBS patients feel pain in visceral organs before it's expected to occur (rectal distension tests).