Assessing rectal sensitivity with elastic balloon vs rectal barostat
Research type
Research Study
Full title
A feasibility study to assess rectal sensitivity using elastic balloon inflation versus a rectal barostat: is there an agreement in London Classification diagnoses?
IRAS ID
331715
Contact name
Natalie Page
Contact email
Sponsor organisation
Newcastle upon Tyne Hospitals NHS Foundation Trust
ISRCTN Number
ISRCTN12953305
Duration of Study in the UK
2 years, 0 months, 1 days
Research summary
Research summary
The human body stores stool (poo) within the rectum, which is between the end of the large bowel and the anus, where stool exits the body. Some people develop issues with sensing that stool is there, or can sense it too much. This can cause symptoms that decrease quality of life, such as leaking stool, pain, and going to the toilet too much or too little. One example where this occurs is a condition called irritable bowel syndrome, which currently affects 3.2 million people in the UK.
The majority of hospitals in the UK assess sensations felt within the rectum by inflating a small elastic (stretchy) balloon, placed within the rectum, with air. The patient is asked at what time they feel different sensations, and from this information a diagnosis can be made (using the London Classification system), which can help their doctor to devise a treatment plan. A less common device, called a rectal barostat, can also be used to test sensations in the rectum. Instead of an elastic balloon, the rectal barostat inflates a plastic bag that is non-elastic, with air. Since the rectal barostat bag is non-elastic, it can also measure the capacity of the rectum, and tell us how stretchy its walls are.
In this study, patients who attend for the elastic balloon test as part of standard care, would also undergo assessment with the rectal barostat in the same hospital appointment. We are aiming to see whether patients tested with the elastic balloon receive the same diagnosis as when they are tested with the rectal barostat. This research is important as it may show that using the rectal barostat changes someone’s diagnosis, and suggests more centres should be using this device instead of the elastic balloon so we can accurately diagnose more patients.
Summary of results
Thank you to all the participants who agreed to participate in this study. The research team now have an improved understanding of how often the two tests (elastic balloon distension test and the rectal barostat test) agree with each other when assessing the sensitivity of the rectum to stool, and how well each test is tolerated.
Newcastle upon Tyne Hospitals NHS Trust sponsored this study, and the study began 22/04/2024 and ended 14/05/2025. Uptake for the study was positive, and a total of 32 participants with bowel symptoms took part in this study, 16 (11F:2M, average age of 64) participated at site 1 (Newcastle upon Tyne Hospitals NHS Foundation Trust) and 16 (14F:2M, average age of 65) participated at site 2 (County Durham and Darlington NHS Foundation Trust). All participants were between the ages of 18 and 90, were nonpregnant, had had previous investigations that ensured the tests were safe to undertake, and had symptoms relating to their bowels. Of patients who were eligible to partake in the study that were contacted, 76% chose to participate at site 1, and 80% at site 2.
All the participants were attending for tests to investigate their bowel symptoms as part of their usual care pathway. One of these tests is called elastic balloon distension, which involves positioning a small elastic balloon within the rectum (where stool is stored) with air. The patient is asked at what time they feel different sensations, and from this information a diagnosis can be made regarding how sensitive their rectum is to sensing stool. This diagnosis is made using a system called the London Classification. Participants additionally underwent a test which is not as commonly used in clinical practice, called the rectal barostat test. This test is also used to assess the sensitivity of the rectum to stool, and instead involves positioning and inflating with air a non-elastic plastic bag in the rectum, and this can also be used to measure the capacity of the rectum. Both tests were undertaken in a randomised order during the participant’s appointment. The results of each of these tests was then compared to see if the London Classification diagnosis was the same. Each participant also filled out a questionnaire asking them how they found each test, and whether they preferred one test over the other.
Complete study data was obtained for 30 participants. Two participants, one per site, withdrew from the study. There were a total of 8 adverse reactions were reported during the study. Of these adverse reactions, 7 were observations of rectal bleeding. In all participants this had resolved within 24 hours. 1 adverse event was an experience of abdominal pain during the rectal barostat test, which resolved once the test was aborted. Results obtained from the questionnaire that participants filled out following their appointment are summarised below:
• Four participants disagreed that the rectal barostat test was comfortable
• Three participants agreed that the rectal barostat test was painful
• Two participants disagreed that the elastic balloon distension test was comfortable
• One participant agreed that the elastic balloon distension test was painful
• 59% of participants did not prefer one test to the other, however 15% stated they preferred the rectal barostat test, and 26% stated they preferred the elastic balloon distension test
• 85% of participants would be willing to undergo the tests againThe average length of time taken to perform each test was 1 minute and 24 seconds for the elastic balloon distension test, and 15 minutes and 26 seconds for the rectal barostat test. The percentage of London Classification diagnoses that remained unchanged from having the elastic balloon distension test compared to the rectal barostat test, was 13% at site 1 and 56% at site 2. The sizable difference in the agreement of diagnosis is likely due to each site using elastic balloon distension equipment produced by two different manufacturers which use different sets of normal values, and indicates there may be a difference in the accuracy of the normal values. The rectal barostat test is repeated three times as part of its usual protocol, and the study showed that when the test is repeated the results are similar each time, demonstrating that it has what is called ‘good test-retest repeatability’.
The study helped to demonstrate that there is poor agreement between the elastic balloon distension test and the rectal barostat test. This suggests patients could be receiving different London Classification diagnoses on how sensitive their rectum is to stool, depending on what test they attend for. This may affect how their bowel symptoms are treated by their consultant, and highlights that the rectal barostat test should be more widely used in clinical practice, as this is considered to be the more accurate test out of the two. However, as the rectal barostat test took much longer to undertake compared to the elastic balloon distension test, this could be a potential barrier to implementing it into a clinical setting.
The study has also helped researchers identify that patients were willing to participate in the study, and very few found the tests uncomfortable or painful. This suggests a larger cohort study would be feasible to conduct in the future, and that introduction of a rectal barostat test in routine patient care would be well-received. The research team plans to use this study to deliver a definitive study in the future, which will provide further evidence of the utility of the rectal barostat test in routine practice.
If you would like to read more about this study, the project is currently registered with the ISRCTN registry (ISRCTN12953305). Information relating to the study is available to read at https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftrack.pstmrk.it%2F3ts%2Fwww.isrctn.com%252FISRCTN12953305%2FNBTI%2FoOTCAQ%2FAQ%2Fe32cedb9-c775-49f7-b530-f6c9f3e91544%2F1%2FPRyb2Dj8z_&data=05%7C02%7Cdulwich.rec%40hra.nhs.uk%7C743036fbac2147c1241608de59cac239%7C8e1f0acad87d4f20939e36243d574267%7C0%7C0%7C639046924537266547%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=InaZVvMrVf86V8i%2FpGsv75IrM8oAXqnV%2BlY1pnsfyl0%3D&reserved=0 , which includes contact information for the research team.
REC name
London - Dulwich Research Ethics Committee
REC reference
23/PR/1521
Date of REC Opinion
29 Jan 2024
REC opinion
Favourable Opinion