IBS or something more serious? When persistent digestive symptoms deserve further investigation

Gastrointestinal symptoms are common and are frequently labelled as irritable bowel syndrome (IBS), with little thought process and few effective treatment options. This doesn’t have to be the case. Firstly, I am not a fan of the term “IBS”. It is an overused, general umbrella term that encompasses many separate conditions, but it is the one most commonly used and widely recognised. For the purpose of this article, I will use the term “IBS”, but prefer to call these functional gut symptoms, or disorders of the gut-brain axis. Secondly, it does not take much to confirm why some people experience these symptoms and explain the causal factors behind them. Once this is known, it allows a more focused and tailored approach to the management of the underlying condition. 

IBS covers a wide range of symptoms affecting both the upper and lower gastrointestinal (GI) tract. They are seen in 30% of all the new patients presenting to their GP practices, and about 40% of those referred to specialists' gastroenterology clinics. IBS symptoms are due to a range of long-term conditions that affect the function of the upper and lower GI system, rather than being due to an underlying organic disease or structural issue. One should, however, always be vigilant with persistent or changing symptoms, as this can sometimes indicate a more serious underlying gastrointestinal condition that requires further investigation. As a consultant gastroenterologist, it is important to emphasise that while most people with IBS do not have a life-threatening illness, symptoms such as unexplained weight loss, rectal bleeding, persistent diarrhoea, anaemia or a strong family history of bowel disease should never be dismissed. A careful assessment, supported by appropriate investigations where necessary, helps distinguish IBS from other digestive disorders.  

What is IBS?

IBS is one of the most common gastrointestinal disorders in the UK. It is classified as a disorder of gut-brain interaction, meaning symptoms arise from altered communication between the digestive system and the nervous system rather than inflammation or damage to the bowel itself.

Research suggests that between ten and twenty per cent of adults experience symptoms consistent with IBS, although many people never seek medical advice.

Common features include:

• Abdominal pain that is often relieved by passing a bowel motion.
• Changes in bowel habits, including diarrhoea, constipation or alternating between both.
• Bloating and excessive wind.
• A feeling of incomplete bowel emptying.
• Symptoms that fluctuate over weeks or months.

Although IBS can significantly affect quality of life, it does not increase the risk of bowel cancer or inflammatory bowel disease.

Symptoms of IBS

The symptoms of IBS vary from person to person and often change over time. Some individuals experience mild episodes, while others find symptoms interfere with work, travel and social activities.

Typical symptoms include:

• Abdominal cramping or discomfort.
• Bloating that worsens during the day.
• Constipation, diarrhoea, or a combination of both.
• Excessive gas.
• Passage of mucus in the stool.
• Symptoms that improve after opening the bowels.

Symptoms are often triggered or worsened by:

• Stress or anxiety.
• Certain foods.
• Hormonal changes.
• Previous gastrointestinal infections.

Around one in twenty people in the UK consult a healthcare professional each year because of IBS-related symptoms, making it one of the most common reasons for referral to gastroenterology services.

When IBS symptoms may suggest another condition

Many gastrointestinal conditions share symptoms with IBS, particularly during their early stages. This overlap means persistent symptoms should not automatically be attributed to IBS without appropriate assessment.

Features that deserve further investigation include:

• Rectal bleeding.
• Unexplained weight loss.
• Persistent or worsening diarrhoea.
• Iron deficiency anaemia.
• Difficulty swallowing.
• Symptoms that regularly wake a person from sleep.
• A strong family history of bowel cancer, coeliac disease or inflammatory bowel disease.
• Symptoms beginning for the first time later in adulthood.

Conditions that may resemble IBS include:

• Inflammatory bowel disease, including Crohn's disease and ulcerative colitis.
• Coeliac disease.
• Bowel cancer.
• Microscopic colitis.
• Bile acid diarrhoea.
• Diverticular disease.
• Lactose intolerance and other food intolerances.

While these conditions are less common than IBS, identifying them promptly can significantly improve long-term outcomes.

How IBS differs from other gastrointestinal conditions

One of the greatest challenges in gastroenterology is distinguishing IBS from diseases that produce similar symptoms.

Unlike IBS, many gastrointestinal diseases cause measurable inflammation, structural abnormalities or changes visible during testing.

Important differences include:

• Inflammatory bowel disease often causes persistent diarrhoea, rectal bleeding, raised inflammatory markers and weight loss.
• Coeliac disease results from an immune reaction to gluten and may cause nutritional deficiencies and anaemia.
• Bowel cancer may present with altered bowel habits, unexplained bleeding, abdominal pain or iron deficiency anaemia.
• Microscopic colitis commonly causes chronic watery diarrhoea despite a normal-looking bowel during endoscopy.
• Bile acid diarrhoea frequently causes urgent, frequent loose stools, particularly after meals.

These distinctions highlight why symptoms alone are not always enough to make a diagnosis.

How IBS and other gastrointestinal conditions are diagnosed

There is no single test that confirms IBS. Instead, diagnosis is based on a person's symptoms together with targeted investigations that exclude other important conditions when appropriate.

Assessment commonly includes:

• A detailed medical history.
• Physical examination.
• Blood tests to check for anaemia, inflammation and coeliac disease.
• Stool tests, including faecal calprotectin, where inflammatory bowel disease is suspected.
• Assessment of dietary and lifestyle factors.

Further investigations may include:

• Colonoscopy.
• Flexible sigmoidoscopy.
• Upper gastrointestinal endoscopy.
• Cross-sectional imaging such as CT or MRI scanning.
• Breath testing for selected conditions.

National guidance supports making a positive diagnosis of IBS using recognised symptom criteria while ensuring that symptoms suggesting more serious disease are appropriately investigated.

When further investigation is important

Most people with IBS do not require extensive testing. However, persistent symptoms, changing bowel habits or the development of new warning signs should prompt reassessment.

Further investigation is particularly important when:

• Symptoms continue despite appropriate treatment.
• There is unexplained weight loss.
• Blood tests reveal anaemia.
• Rectal bleeding occurs.
• There is persistent diarrhoea lasting several weeks.
• Symptoms first develop after the age of fifty.
• There is a significant family history of gastrointestinal disease.

In the UK, approximately forty-three thousand people are diagnosed with bowel cancer each year. Although cancer remains far less common than IBS, early diagnosis substantially improves treatment outcomes, making appropriate investigation essential when warning signs are present.

The importance of an accurate diagnosis

Living with persistent digestive symptoms can be frustrating and concerning. While IBS remains the most likely explanation for many people, assuming that every episode of abdominal discomfort or altered bowel habit is IBS may delay the diagnosis of other treatable conditions.

An accurate diagnosis provides several important benefits:

• Appropriate treatment based on the underlying cause.
• Reassurance when a serious disease has been excluded.
• Earlier identification of inflammatory or malignant conditions.
• Improved long-term symptom control.
• Better quality of life through personalised management.

From a gastroenterologist's perspective, the aim is not simply to label symptoms as IBS but to identify those individuals whose symptoms require further investigation. Careful clinical assessment, supported by evidence-based investigations where appropriate, ensures that significant disease is detected promptly while avoiding unnecessary testing for those with typical IBS.

References

• National Institute for Health and Care Excellence. Irritable bowel syndrome in adults: diagnosis and management (CG61).
• National Institute for Health and Care Excellence. Suspected cancer: recognition and referral (NG12).
• British Society of Gastroenterology. Guidelines for the management of irritable bowel syndrome.
• British Society of Gastroenterology. Guidelines for investigation of chronic diarrhoea in adults.
• Crohn's & Colitis UK. Inflammatory bowel disease information and statistics.
• Coeliac UK. Coeliac disease facts and prevalence.
• Cancer Research UK. Bowel cancer statistics for the UK.
• Office for National Statistics. Cancer registration statistics, England.
• Black CJ, Ford AC. Global burden of irritable bowel syndrome: trends, predictions and risk factors. Nature Reviews Gastroenterology & Hepatology. 2020.
• Lacy BE, Pimentel M, Brenner DM, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. American Journal of Gastroenterology. 2021.