Look on any site about Neuroendocrine Tumours (NETs) and you’ll find the term IBS (irritable bowel syndrome) frequently mentioned. That’s because it’s a common misdiagnosis for many before being formally diagnosed with NETs.

But what exactly is IBS, why is it such a common misdiagnosis for many NET patients and how can these misdiagnoses be prevented or reduced in future?  I just spent a few hours doing an online training course on IBS and I want to pass on some stuff I found to be very useful. I have never been diagnosed with IBS but having researched the issue through some training, I can understand why it might be in the thoughts of a general practitioner for many scenarios.  Much of my research was focussed on the British Society of Gastroenterology (BSG) who sponsored the online course I completed which also used material from their magazine Gut, a leading international journal in gastroenterology.

What is IBS?

Irritable bowel syndrome (IBS) is a common, long-term condition of the digestive system. It can cause bouts of stomach cramps, bloating and excessive wind, diarrhea and/or constipation, feeling of incomplete emptying, mucus in stool; and many other symptoms (see NHS IBS site).

The symptoms vary between individuals and affect some people more severely than others. They tend to come and go in periods lasting a few days to a few months at a time, often during times of stress or after eating certain foods.  IBS is a heterogeneous condition with a range of treatments.  There are in fact different classifications of IBS and the diagram below supports the list with some context:

• • IBS-D – diarrhea based
  • IBS-C – constipation based
  • IBS-M – mix of both diarrhea and constipation

You can see why someone presenting with diarrhea or IBS-D type symptoms might be automatically assumed to have IBS despite the fact that these symptoms could also apply to many other conditions including several cancers.  However, what I also found is that in the UK, there is now updated guidance from NICE (National Institute for Health and Care Excellence) to aid GPs and other physicians on how to properly diagnose IBS.  In fact, the online course I undertook is one of many now being offered to medical staff as part of the new guidance. That sounds like a good thing in practice (although I did notice some differences between the BSG recommendations and what is published by NICE…….. £ )

How is IBS diagnosed?

That is considerably complex as the symptoms are fairly general.  However, I was encouraged to find that doctors should assess any ‘red flag’ indicators that would need a referral to secondary care before any firm decision on IBS was made. These include (but not limited to), unintentional and unexplained weight loss, rectal bleeding, family history of bowel or ovarian cancer, a change in bowel habit to looser and/or more frequent stools persisting for more than 6 weeks in a person aged over 60 years, anaemia, abdominal masses, rectal masses, inflammatory markers for inflammatory bowel disease.  That’s very interesting because in 2010, after mentioning some unintentional weight loss, my GP said ‘anaemia’ to me and referred me to secondary care.  Perhaps I was lucky but perhaps, my GP’s team was just professional and thorough?  That said, if you’re with me so far, you can see why IBS might be an easy diagnosis to make for someone presenting with either diarrhea/constipation issues with no other obvious symptoms or abnormal test results (particularly IBS-D).

Why might NETs be frequently misdiagnosed as IBS?

Using the NICE guidelines, I noted there are a range of tests to preclude other diagnoses including full blood count (FBC), erythrocyte sedimentation rate (ESR) or plasma viscosity, c‑reactive protein (CRP), antibody testing for Coeliac disease. Whilst abnormal results of these tests might show up something to investigate further (i.e. FBC – haemoglobin worked for me), none of them include looking ‘inside’ the patient and I guess there is a resource/finance issue involved here.

In fact, the guidelines also list a number of tests that are NOT necessary to confirm a diagnosis of IBS. These include ultrasound, rigid/flexible sigmoidoscopy, colonoscopy, barium enema, thyroid function test, faecal ova and parasite test, faecal occult blood, hydrogen breath test.  You can see the issues ………..

The guidelines go on to say that a diagnosis of IBS should be considered only if the person has abdominal pain or discomfort that is either relieved by defecation or associated with altered bowel frequency or stool form. This should be accompanied by at least two of the following four symptoms:

• altered stool passage (straining, urgency, incomplete evacuation)
• abdominal bloating (more common in women than men), distension, tension or hardness
• symptoms made worse by eating
• passage of mucus.
  
  Other features such as lethargy, nausea, backache and bladder symptoms are common in people with IBS, and may also be used to support the diagnosis

I also noted that the causes of IBS are inextricably linked with psychological issues and the guidance also includes therapies including cognitive behavioural therapies (CBT) relaxation therapies, and hypnosis.

So, if you’re one of the unlucky ones who has presented with “IBS like” symptoms and have normal test results as per above, you may not get the opportunity to get to further testing to find the true diagnosis. It’s possible that you saw a physician who has not followed guidelines for diagnosing IBS, if indeed such guidelines were available to him/her.  The inclusion of psychological issues also connects with many anecdotal stories of NET patients being told they needed psychological help before eventually being diagnosed with NETs.

I can see many similarities in the descriptions of IBS symptoms and the sort of things you can read on NET forums – curiously including the effects of NET surgery and other treatment after diagnosis.

Slight digression but if this subject is of interest, you may like to comment.  I once said to my Oncologist that I felt as if I had IBS since my surgery and somatostatin analogue treatment. In fact, I told him that I thought my bowel was more than irritated, it was bloody angry! During my research, I couldn’t help noticing that some of the suggestions and recommendations for IBS are similar to those offered to a post-surgical NET patient.  You may therefore like my blog series on Nutrition which was co-authored by a NET specialist dietician who is also IBS aware.

Preventing or Reducing a Misdiagnosis of IBS (all illnesses)

The course looked at this angle as it was clearly keen to emphasise this to medical people going through the module.  The NICE guidelines read like a process that must be strictly followed but at the end of the day, they are just ‘guidance’ and should not stop doctors from thinking outside the box.

A recent study suggested that as many as 1 in 6 patients (~16%) with symptoms of IBS had another disease.  Approximately 7% had Crohn’s disease, 3% coeliac disease, and 2% microscopic colitis when they were formally tested. Patients with IBS-diarrhoea predominant more often had abnormalities than those with IBS-constipation predominant (interesting for NETs).  The paper stresses the importance of tailored investigation of patients presenting for the first time.

One in six patients with symptoms compatible with IBS without alarm features in this selected group exhibited organic GI disease following an investigation. Assessment of alarm features in a comprehensive history is vital to reduce diagnostic uncertainty that can surround IBS. You can, if you wish, read the abstract of the paper on the link below.

The issue here is that people not meeting the criteria for further checks may be precluded for scans and other tests due to lack of clinical evidence and their diagnosis of IBS will stand.  As this was a study, clearly some of them might have gone on to present with sufficient clinical evidence to warrant more checks and subsequent diagnosis of something else at a more advanced stage.  Clearly, this sounds familiar with NETs.  However, looking at the figures above, I suspect the figures of NETs IBS misdiagnoses are pretty small in comparison to those who are correctly diagnosed with IBS.  To put that into context (in the UK), according to the NHS, IBS is thought to affect up to one in five people (10,000,000 in UK alone) at some point in their life, and it usually first develops when a person is between 20 and 30 years of age and around twice as many women are affected as men.  Compare that with a UK NETs prevalence of around 50,000 (guesstimate), you can see that a misdiagnosis of IBS for NETs, is not that common.  However, one misdiagnosis is one too many. 

Summary

Having done this course and read the accompanying references (some only abstracts), I can see the scope for people with many different illnesses being misdiagnosed with IBS. However, the use of alarm symptoms and ref flag indicators should be helping to reduce this. I’m guessing that many people in first-line care may not be fully aware of the IBS guidelines to be able to take heed.  I’m also guessing that in the UK (at least), a 10-minute appointment with a busy GP is just not going to solve some of these symptom clashes and many visits might be required to move forward.

It’s really difficult to advise anyone going through a diagnosis of IBS as to how to approach a physician who says they have IBS and they think this is wrong.  In the case of NETs, other cardinal symptoms may be of use in convincing physicians (e.g. flushing).  Armed with this knowledge, I would say to anyone who suspects NETs but is faced with an IBS diagnosis, take a copy of the BSG and NICE guidelines to your doctor and tick off all the differential ‘ref flag’ and ‘alarms’ issues ensuring that each has been tested before accepting the IBS diagnosis.

References used to support compilation of this blog:

NHS Site – IBS

The IBS online course (it may expire depending on when you read this post)

Prevalence of organic disease at colonoscopy in patients with symptoms compatible with irritable bowel syndrome: a cross-sectional survey (abstract only, not full article)

BSG Guidelines on the irritable bowel syndrome: mechanisms and practical management (full article)

NICE Guidance – irritable bowel syndrome  in adults