The different types of IBS

Did you know there are actually different types of IBS? You may have heard your doctor refer to your IBS as;

• IBS-C
• IBS-D
• IBS-M
• IBS-A
• IBS-U.

What do these letters mean? What are the different types of IBS and are they important?

What are the IBS subtypes?

IBS can be classified into 3 main subtypes based on the bowel habits and type of poo that you experience most often. [1]

1. IBS - C = IBS with mostly constipation.
2. IBS - D = IBS with mostly diarrhoea.
3. IBS - M = IBS with mixed bowel habits ranging from constipation to diarrhoea. (This subtype can also be referred to as IBS-A = Alternating).

* IBS - U = IBS unclassified by no obvious pattern or predominance of bowel habits.

How are the subtypes decided?

These subtypes are decided by referencing the Bristol Stool Chart. According to the Rome IV criteria for these subtypes more than 25% of the patients symptomatic, abnormal stools (not all total stools) must identify with the relevant stool types. This means that to be classified as IBS - C during periods of flare-ups and symptoms more than 25% of stools should be identified in the range of 1-2 (hard/lumpy) and less than 25% identified in the range of 6-7 (loose/watery) on the Bristol Stool Chart.

• IBS - C = >25% type 1-2 and <25% type 6-7
• IBS - D = >25% type 6-7 and <25% type 1-2
• IBS - M = >25% type 1-2 and equally >25% type 6-7
• IBS - U = The relevant % of symptomatic stools cannot be determined.

Do I need to know my IBS subtype?

Although knowing your IBS subtype is not essential it can be useful. Being classified into a subtype allows your health professionals to focus your treatment plan on the most predominant, (often most bothersome) symptoms of your subtype. This makes it possible to achieve the biggest symptom relief in the shortest time. In addition, some treatments and medications are better suited to one subtype of IBS over another. Knowing where to start can potentially save you from wasting time and money on less effective methods.

Whilst it's possible to be diagnosed with IBS where no subtype is given, changes have been made to the Rome IV criteria to try to minimise this. As a result, the number of patients deemed 'unclassified' has been reduced.

These changes reflect the fact that most people experience bowel motions that vary between 1-7 type on the Bristol Stool Chart. They also take into account that patients in remission can go for long periods where they consider their stool type to fit within the normal 3-5 type range. The changes are to classify patients based on the proportion of symptomatic bowel movements rather than all bowel movements. This gives a more reliable view of the predominant subtype.

Do you suspect you may have IBS? Could you do with some support as you navigate your tests, doctors appointments and diagnosis? We break it all down into easy to manage steps in these posts.

Which IBS type are you? Share if you dare in the comments below.