Coeliac disease and irritable bowel syndrome (IBS) share many digestive symptoms, which can make differential diagnosis difficult in clinical practice. In recent years, various studies have also suggested that the two conditions may be linked more frequently than expected.

People with coeliac disease are at a significantly higher risk of developing irritable bowel syndrome, even many years after diagnosis.

Irritable bowel syndrome is a functional digestive disorder characterised by recurrent abdominal pain associated with changes in bowel habits, such as diarrhoea, constipation or both.

It is a very common and heterogeneous condition, with no specific biomarkers, and its diagnosis is based primarily on clinical criteria.

Symptoms common to both IBS and coeliac disease

One of the main diagnostic problems is that many symptoms of IBS overlap with those of coeliac disease, including:

• Recurrent abdominal pain
• Abdominal bloating
• Diarrhoea or constipation
• Changes in bowel habits
• A persistent feeling of digestive discomfort

This overlap explains why, in some cases, coeliac disease may initially be mistaken for irritable bowel syndrome.

There is currently no single definitive explanation to account for this relationship between irritable bowel syndrome and coeliac disease. Several mechanisms are likely to be involved:

1. Persistent villous atrophy and digestive symptoms

Patients with persistent villous atrophy appear to receive fewer diagnoses of IBS than those with mucosal recovery. In these cases, digestive symptoms may be directly attributed to the activity of coeliac disease and not labelled as irritable bowel syndrome.

2. The possible role of diagnostic bias

Researchers have also taken into account what is known as ‘surveillance bias’. In previous studies, many diagnoses of IBS occurred shortly after a diagnosis of coeliac disease, suggesting that part of the increased risk might simply be due to greater medical follow-up.

However, according to the most recent research, the association persists even after long periods of follow-up, reinforcing the hypothesis of a genuine link between the two conditions.

Furthermore, an increased risk of an IBS diagnosis prior to the detection of coeliac disease has also been observed, probably because some symptoms may be mistakenly interpreted as a functional digestive disorder.

In short, current evidence confirms that people with coeliac disease are at greater risk of developing irritable bowel syndrome, and that conversely, symptoms of IBS are commonly present in patients with undiagnosed coeliac disease.

This clinical overlap between the two conditions necessitates a careful diagnostic approach and the consideration of coeliac disease in patients with symptoms consistent with IBS.

Understanding this relationship can help improve both the diagnosis and long-term management of patients with coeliac disease.