Have you heard about the new movie about constipation?

It’s not out yet.

There is no shortage of jokes about constipation, but it’s actually no laughing matter.

It is a common condition that affects people of all ages, with varying degrees of severity. Many people experience it briefly but for others it can be a chronic condition that causes significant pain and discomfort and affects their quality of life.

The US National Institute on Ageing, part of the Department of Health and Human Services, reports that “nearly everyone becomes constipated at one time or another”, and that “constipation is a symptom, not a disease”.

“Doctors do not always know what causes constipation,” it adds.

A further complication is revealed in a new study by researchers from King’s College London, in the UK, which finds that what many people see as constipation differs drastically from the definitions applied by doctors and contained in formal diagnosis guidelines.

Their report, published in the American Journal of Gastroenterology, identified six key sets of symptoms common to both the general public and doctors that could form the basis of a new medical definition for the condition.

Constipation remains troublesome in other ways, too.

“Currently prescription medication for constipation fails in nearly 60% of patients, and almost half report not being satisfied with their treatment,” says Eirini Dimidi, the study’s lead author.

Most people with chronic constipation do not visit a doctor, but in Britain it is diagnosed in more than a million general practitioner consultations and 63,000 hospital admissions every year.

Its detection, however, varies considerably.

Some patients self-diagnose, some doctors diagnose pragmatically, and others use formal criteria, such as the Rome IV diagnostic criteria, which specify combinations of symptoms experienced over defined periods of time.

“Previous studies have tried to estimate how many people suffer from constipation, but their results vary between 3% and 35%,” Dimidi says.

He adds that one reason for this wide range may be the lack of a consistent way to diagnose it.

“Accurately identifying a condition is at the root of good care,” he says.

The researchers collected data from 2557 members of the public, of which 934 had self-reported constipation, along with 411 GPs and 365 gastroenterology specialists.

They found that of those who self-reported constipation, 94% met the formal diagnostic criteria found in Rome IV, which must include at least two of these symptoms for 25% of defecations: straining; lumpy or hard stools; sensation of incomplete evacuation; sensation of anorectal obstruction or blockage; and manual manoeuvres. Having fewer than three bowel movements per week also counts.

Surprisingly, however, of the 1623 who did not self-report constipation, 29% met these criteria too. Nearly one-third of “healthy” patients were, therefore, clinically constipated but did not recognise it.

Using case studies, the rates of correct diagnosis of constipation ranged from 99% down to 39%, depending on the symptoms present.

Infrequent bowel movements, for example, were perceived as important by less than a third of the constipated general population, compared to 41% of GPs and as many as 65% of specialist doctors.

The study also highlighted six key symptom clusters that were commonly agreed upon across the study groups: abdominal discomfort, pain and bloating; rectal discomfort; infrequent bowel movements and hard stools; sensory dysfunction; flatulence and bloating; plus faecal incontinence.

Study contributor Kevin Whelan says the research has discovered that many of the symptoms considered important for a diagnosis of constipation by the general public are not part of any current diagnostic criteria or assessment tools, “with significant differences between patients and doctors”.

“This is important as patients who seek medical care for their constipation-related symptoms may not have their symptoms recognised as constipation by the doctor and, therefore, may not be managed as such. This could significantly impact patients’ access to care and treatment.”