Introduction
Irritable Bowel Syndrome (IBS) is a gastrointestinal tract disorder that affects the large intestine, which is also known as the colon.

Normally, food that is consumed is pushed through the digestive tract by muscle contractions of the intestines. In individuals with IBS, contractions either last too long or too short of a time. This creates problems in proper food movement through the digestive tract
Common symptoms associated with IBS include abdominal pain, bloating, diarrhea, and constipation. In most cases, these symptoms do not become extreme and can be controlled through a combination of medications and lifestyle changes
Irritable Bowel Syndrome is classified and diagnosed as four subtypes, depending on the individual’s stool consistency. The IBS classification is important, as it determines what medications and treatments the individual shall receive.

IBS with constipation: Hard stools at least 25% of the time, loose stools less than 25% of the time
IBS with diarrhea: Loose stools at least 25% of the time, hard stools less than 25% of the time
Mixed IBS: Hard stools at least 25% of the time, loose stools at least 25% of the time
Irritable Bowel Syndrome is believed to affect anywhere between 3-20% of the population
IBS has been found to affect females twice as often as it affects males
While the disorder can occur at any age, it usually begins during young adulthood. Studies have found that in most cases, it occurs in individuals under the age of 45 years.

Common risk factors of Irritable Bowel Syndrome include:

Young age: Most cases of IBS occur in individuals under the age of 45 years
Gender: Females are twice as likely to suffer from the condition, as males
Family history: Individuals having relatives with IBS, are more likely to suffer from the syndrome themselves
Stress: Many cases of IBS arise due to stress
Low-fiber diet: Fiber is important in your diet, as it promotes the movement of food material through the digestive tract, increases the weight of your stools, and also softens your stools
Currently, researchers do not know the exact cause of Irritable Bowel Syndrome. A variety of factors are believed to contribute towards it, including:

Abnormal serotonin levels: Serotonin is a chemical messenger important in brain function and digestive system function; when abnormal levels are present, the digestive system cannot function properly
Improper diet: Many individuals have been found to suffer from IBS when their intake of food and drink, like chocolate, alcohol, dairy products, and carbonated drinks increase
Stress: While the physiological link between stress and IBS has not been established, research has determined that stress aggravates the symptoms further
Hormone imbalances: Studies have found that in women, IBS is more likely to occur during one’s menstrual period. Furthermore, postmenopausal women have been found to suffer from the condition, though with fewer symptoms than menstruating women. This suggests that reproductive hormones impact one’s likelihood of developing IBS
Genetics: Individuals with a family history of the disorder have an increased likelihood of developing it themselves. It is unclear whether this increased risk is due to genetic or environmental factors
Although the causes of Irritable Bowel Syndrome are unclear and varied, the physiology of the disorder is the same in all cases. In a healthy individual, the GI tract muscles contract in a coordinated manner to move food through the digestive system. In individuals with IBS, however, muscle contraction either occurs too quickly or too slowly, resulting in abnormal movement of food.

Common signs and symptoms of Irritable Bowel Syndrome include:

Abdominal pain, cramps
Bloating, passing gas
Diarrhea
Constipation
Mucous in stools
Abnormal bowel movements
Loose, watery stools or hard, lumpy stools (or alternating bouts of both)
Loss of appetite

Diagnosis of IBS
While these signs may occur in many individuals after consuming a large meal, a diagnosis of IBS is made, if these signs and symptoms are present, at least three times a month over a three-month period.
There are no formal tests to diagnose Irritable Bowel Syndrome. In most cases, the disorder is diagnosed based on one’s signs and symptoms. Due to the lack of formal tests, the Rome criteria for diagnosing IBS have been developed. According to this criteria:

Abdominal pain is present over a 12-week period (it does not have to be constant, or present during consecutive weeks)
Stool frequency or stool consistency has changed
Mucous is present in the stool
Straining, or a feeling that you cannot completely empty your bowels, occurs
The doctor may, however, conduct tests to rule out other medical problems, such as:

A blood test may be performed to check for an abnormal blood count
Stool cultures may be checked for infection
A colonoscopy may be conducted, if the symptoms arise after the age of 50 years
The physician may also suggest removing dairy products from your diet for a few weeks, to see if you are lactose intolerant. If symptoms improve, then it is likely that IBS may not be the problem
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

Complications of IBS
The possible complications from Irritable Bowel Syndrome could include:

While IBS does not cause any permanent damage to the digestive tract, it can impact one’s quality of life
Due to the signs and symptoms of the disorder, it is often difficult to engage in social activities or leave home for extended periods of time
It has also been found that the bowel disorder impacts one’s ability to attend work. Studies have found that individuals with IBS are three times more likely to take sick days, as those without IBS
IBS can also impact one’s ability to have a healthy sexual life. Symptoms of the disorder often make it difficult to get in the mood, or take part in sex

Treatments for irritable bowel syndrome (IBS)

Many people are reassured that their condition is IBS, and not something more serious such as colitis. Simply understanding about IBS may help you to be less anxious about the condition, which may ease the severity of symptoms. Symptoms often settle for long periods without any treatment. In some cases, symptoms are mild and do not require treatment.

If symptoms are more troublesome or frequent, one or more of the following treatment options may be advised:
Treatment option 1: lifestyle changes

Exercise. Regular exercise is known to help to ease symptoms.
Managing stress levels. Stress and other emotional factors may trigger symptoms in some people. So, anything that can reduce your level of stress or emotional upset may help.
Keeping a symptom diary. It may help to keep a food and lifestyle diary for 2-4 weeks to monitor symptoms and activities. Note everything that you eat and drink, times that you were stressed, and when you took any formal exercise. This may identify triggers, such as a food, alcohol, or emotional stresses, and may show if exercise helps to ease or to prevent symptoms. If you are advised to try a particular treatment, it may be sensible to keep a symptom diary before and after the start of the treatment. For example, before changing the amount of fibre that you eat, or taking a probiotic (explained later), or starting medication. You may wish to jot down in the diary the type and severity of symptoms that you have each day for a week or so. Keep the diary going after you start treatment. You can then assess whether a treatment has improved your symptoms or not.

Treatment option 2: dietary changes

A healthy diet is important for all of us. However, some people with irritable bowel syndrome (IBS) find certain foods of a normal healthy diet can trigger symptoms or make symptoms worse.
Current guidelines about IBS include the following points about diet, which may help to minimise symptoms:

Have regular meals and take time to eat at a leisurely pace.
Avoid missing meals or leaving long gaps between eating.
Drink at least eight cups of fluid per day, especially water or other non-caffeinated drinks. This helps to keep the stools (faeces) soft and easy to pass along the gut.
Restrict tea and coffee to three cups per day (as caffeine may be a factor in some people).
Restrict the amount of fizzy drinks that you have to a minimum.
Don’t drink too much alcohol. (Some people report an improvement in symptoms when they cut down from drinking a lot of alcohol.)
Consider limiting intake of high-fibre food (but see the section above where an increase may help in some cases).
Limit fresh fruit to three portions (of 80 g each) per day.
If you have diarrhoea, avoid sorbitol, an artificial sweetener found in sugar-free sweets (including chewing gum) and in drinks, and in some diabetic and slimming products.
If you have a lot of wind and bloating, consider increasing your intake of oats (for example, oat-based breakfast cereal or porridge) and linseeds (up to one tablespoon per day). You can buy linseeds from health food shops.
Fibre

Fibre (roughage – and other bulking agents) is the part of the food which is not absorbed into the body. It remains in your gut, and is a main part of stools. There is a lot of fibre in fruit, vegetables, cereals, wholemeal bread, etc. In some people, perhaps particularly those with constipation, a high-fibre diet definitely helps. In others, often those with diarrhoea, a high-fibre diet makes symptoms worse. If you keep a symptom diary, you can work out which is true for you. Then you can adjust your fibre intake accordingly.
What seems to be the case is that the type of fibre is probably important. There are two main types of fibre – soluble fibre (which dissolves in water) and insoluble fibre. It is soluble fibre rather than insoluble fibre that seems to help ease symptoms in some cases. So, if you increase fibre, have more soluble fibre and try to minimise the insoluble fibre.

Dietary sources of soluble fibre include oats, ispaghula (psyllium), nuts and seeds, some fruit and vegetables and pectins. A fibre supplement called ispaghula powder is also available from pharmacies and health food shops. This seems to be the most beneficial type of supplement.
Insoluble fibre is chiefly found in corn (maize) bran, wheat bran and some fruit and vegetables. In particular, avoid bran as a fibre supplement.

Probiotics

Probiotics are nutritional supplements that contain good germs (bacteria). That is, bacteria that normally live in the gut and seem to be beneficial. Taking probiotics may increase the good bacteria in the gut which may help to ward off bad bacteria that may have some effect on causing IBS symptoms.

Treatment option 3: Medication
Antispasmodic medicines for tummy (abdominal) pain
These are medicines that relax the muscles in the wall of the gut. Your doctor may advise one if you have spasm-type pains. There are several types of antispasmodics. They work in slightly different ways. Therefore, if one does not work well, it is worth trying a different one. If one is found to help then you can take it as required when pain symptoms flare up. Many people take an antispasmodic medicine for a week or so at a time to control pain when bouts of pain flare up. Some people take a dose before meals if pains tend to develop after eating.Note: pains may ease with medication but may not go away completely.

Treating constipation
Constipation is sometimes a main symptom of irritable bowel syndrome (IBS). If so, it may help if you increase your fibre as discussed earlier (that is, with soluble fibre such as ispaghula). Sometimes laxatives are advised for short periods if increasing fibre is not enough to ease a troublesome bout of constipation. It is best to avoid lactulose if you suffer with IBS.

Treating diarrhoea
An antidiarrhoeal medicine may be useful if diarrhoea is a main symptom. Loperamide is the most commonly used antidiarrhoeal medicine for IBS. You can buy this at pharmacies as an over-the-counter medicine. You can also get it on prescription which may be more cost-effective if you need to take it regularly.
The dose of loperamide needed to control diarrhoea varies considerably. Many people use loperamide as required but some take it regularly. Many people learn to take a dose of loperamide in advance when they feel diarrhoea is likely to be a problem. For example, before going out to places where they know it may be difficult to find a toilet.

Treating bloating
Peppermint oil may help with bloating and wind. It is available over-the-counter or on prescription. For some people peppermint oil also helps with tummy pains and spasms.

Antidepressant medicines
A tricyclic antidepressant is sometimes used to treat IBS. In particular, it tends to work best if pain and diarrhoea are the main symptoms. An example is amitriptyline. (Tricyclic antidepressants have other actions separate to their action on depression. They are used in a variety of painful conditions, including IBS.) Other types of antidepressants, called selective serotonin reuptake inhibitors (SSRIs) are also occasionally used for IBS. For example, a tablet called fluoxetine. They may work by affecting the way you feel pain.
Unlike antispasmodics, you need to take an antidepressant regularly rather than as required. Therefore, an antidepressant is usually only advised if you have persistent symptoms, or frequent bad flare-ups that have not been helped by other treatments.

Treatment option 4: Other types of treatment
Psychological treatments (talking treatments)
Situations such as family problems, work stress, examinations, recurring thoughts of previous abuse, etc, may trigger symptoms of irritable bowel syndrome (IBS) in some people. People with anxious personalities may find symptoms difficult to control.
The relationship between the mind, brain, nervous impulses, and overactivity of internal organs such as the gut is complex. Psychological treatments are mainly considered in people with moderate-to-severe IBS:

When other treatments have failed; or
When it seems that stress or psychological factors are contributing to causing symptoms.
The National Institute of Health and Care Excellence (NICE) recommends that cognitive behavioural therapy (CBT), hypnotherapy or psychological therapy should be considered when your symptoms have not improved with medication after one year.

What is the outlook (prognosis)?
In most people with irritable bowel syndrome (IBS), the condition tends to persist long-term. However, the severity of symptoms tends to wax and wane. You may have long spells without any symptoms, or with only mild symptoms. Treatment can often help to ease symptoms when they flare up. In some cases, symptoms clear for good at some stage. This is more likely if your IBS started after an infection (gastroenteritis).