Irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a common, chronic disorder of how the bowel works. The symptoms are very real — abdominal pain, bloating, and changes in bowel habit — but the bowel itself looks structurally normal at examination and imaging. This is what doctors mean when they call IBS a functional disorder: the function is disturbed, but there is no visible structural problem.

IBS affects around 1 in 7 adults worldwide. It can begin at any age, often starts in early adulthood, and is more common in women. It is debilitating for many people — and unfortunately also frequently dismissed or trivialised, which makes the experience more isolating.

There are three common patterns: IBS-D (diarrhoea-predominant), IBS-C (constipation-predominant), and IBS-M (mixed — alternating between the two). Most people fall fairly clearly into one of these, though the pattern can shift over time.

IBS is a diagnosis of exclusion. That phrase matters. It means the diagnosis is made after the conditions that can mimic IBS have been properly looked for and ruled out — not before, and not as a shortcut.

A great many conditions cause symptoms that look very similar to IBS:

• Coeliac disease — sensitivity to gluten that damages the small bowel lining
• Inflammatory bowel disease (IBD) — Crohn's disease or ulcerative colitis (see IBD)
• Bowel cancer or pre-cancerous polyps — particularly important to exclude in anyone over 45, with red flag symptoms, or with a family history (see Bowel Cancer)
• Disaccharidase deficiencies — lactase, sucrase-isomaltase and related enzyme deficiencies in the small bowel; often missed and surprisingly common
• Microscopic colitis — inflammation of the bowel lining that cannot be seen at colonoscopy but is found on biopsies
• Bile acid malabsorption — excess bile acids in the colon causing chronic diarrhoea
• Pelvic floor dysfunction — see the Pelvic Floor Dysfunction page
• Endometriosis involving the bowel, in women with cyclical symptoms

Treating someone for IBS when one of these is the real cause means continued symptoms and a missed diagnosis. That is why a proper investigation matters, particularly when the diagnosis has not been formally made or when standard IBS management is not working.

IBS typically causes:

• Abdominal pain or cramping that is related to bowel motions — typically relieved or worsened by passing a motion
• A change in stool form or frequency — looser, harder, more frequent, or less frequent than usual; often alternating
• Bloating and a sensation of distension, often worse as the day goes on
• Excess wind
• Mucus in the stool (clear or whitish)
• A sense of incomplete emptying after going to the toilet

The symptoms typically come and go in cycles over weeks and months, and are often worse during periods of stress, after specific foods, or around menstruation in women. The pattern is usually long-standing — symptoms over many months or years — rather than a sudden recent change.

Certain symptoms should never simply be put down to IBS without investigation. If you have any of the following, please see your GP for a referral promptly:

• Rectal bleeding or dark, tar-like stools
• Unintentional weight loss
• New iron deficiency or unexplained anaemia
• New symptoms beginning over the age of 45 — IBS most often starts in younger adulthood, so symptoms starting later in life deserve careful investigation
• A family history of bowel cancer, polyps, or inflammatory bowel disease
• Symptoms that wake you at night — true IBS symptoms typically settle when you are asleep
• Persistent, worsening, or rapidly changing symptoms — particularly if the pattern is different from your previous longstanding symptoms
• A persistently abnormal blood test — raised inflammatory markers, low iron, abnormal liver tests

The presence of any of these does not mean something serious is found — most often the result is reassuring. But it does mean investigation should not be skipped.

The surgical role in IBS is to investigate thoroughly and to exclude the structural and treatable causes that mimic it. Which investigations are appropriate depends on your age, your symptoms, your family history, and what has already been done. A typical workup may include:

• Blood tests — full blood count, inflammatory markers (CRP), iron studies, thyroid function, and coeliac serology (the standard blood test for coeliac disease)
• Faecal calprotectin — a simple stool test that helps distinguish IBS from inflammatory bowel disease
• Colonoscopy — particularly when there are red flag symptoms, family history of bowel cancer, or new symptoms over the age of 45. Biopsies taken during the colonoscopy can also rule out microscopic colitis
• Gastroscopy with biopsies — useful where coeliac disease or a disaccharidase deficiency is suspected, particularly in patients whose symptoms have been labelled IBS without a clear explanation
• Other tests — such as breath testing for lactose intolerance or bacterial overgrowth, or imaging — may be arranged depending on the clinical picture

The aim is not to investigate exhaustively, but to investigate appropriately. What each test is for, why it is being done for you specifically, and what the result will and will not tell us is explained clearly.

Once any structural or treatable cause has been excluded — and IBS is confirmed as the diagnosis — ongoing management is best led by a gastroenterologist or your GP, not by a surgeon.

Modern IBS management is much better than its reputation. It usually combines several elements, tailored to you:

• Dietary changes — particularly the structured low-FODMAP diet (with a specialist dietitian), which helps a large proportion of patients identify trigger foods
• Antispasmodic medications (e.g. mebeverine, hyoscine) for cramping
• Targeted laxatives or anti-diarrhoeals depending on the subtype
• Neuromodulator medications (low-dose antidepressants used for their effect on the gut–brain axis, not for depression) — often very effective for pain and bowel-habit regulation
• Psychological therapies — particularly gut-directed hypnotherapy and cognitive behavioural therapy (CBT), both of which have strong evidence in IBS
• Lifestyle measures — regular sleep, stress management, exercise

The combination that works for you is something to find with your gastroenterologist or GP over time, with the reassurance of knowing that nothing important has been missed.

Mr Nguyen's role for patients with possible or confirmed IBS is focused and clear:

• Investigation — performing the colonoscopy, gastroscopy, and any related biopsies (including disaccharidase assays where appropriate) to exclude the structural and treatable causes that mimic IBS
• Communication of findings — sitting down with you to explain what was found, what it means, and what it does not mean
• Referral and coordination — referring you to a gastroenterologist for ongoing IBS management, or back to your GP when that is appropriate, and keeping everyone informed

Mr Nguyen does not manage IBS long-term himself, but he is committed to making sure the exclusion phase is done properly so that the management phase can be effective.

Consider asking your GP for a referral if any of the following apply to you:

• You have chronic bowel symptoms that have never been formally investigated
• You have any of the red flag symptoms listed above
• You have been managed as IBS but standard treatment has not been effective
• Your symptoms have changed in pattern, become worse, or are no longer responding to what previously helped
• You have a family history of bowel cancer, polyps, IBD, or coeliac disease — and your own bowel symptoms have not been investigated to take account of that

An investigation that comes back reassuring is useful: it removes the worry and clears the path to focused IBS management.

Your GP will send a referral and most patients are seen within one to two weeks. At the consultation a careful history is taken — symptom pattern, food triggers, family history, what has already been tried — and which investigations are appropriate for you is discussed. Where colonoscopy or gastroscopy is recommended, it is usually arranged within a few weeks at Warringal Private Hospital or Epworth Eastern.

A follow-up appointment is arranged once results are back. If the investigations are reassuring, you will be referred on to a gastroenterologist (or back to your GP) for ongoing IBS management, with continuity of care maintained. If something other than IBS is found, that is managed directly or referred to the right specialist.