Introduction 

What is pouchitis?

Individuals suffering from diseases such as ulcerative colitis may undergo surgery to remove their large bowel, also known as the colon.¹ The ileum is the final section of the small intestine and is used in these surgeries to form a store to hold faeces before it is excreted.² This is referred to as an ileal pouch. 

Pouchitis refers to the inflammation of the ileal pouch as a result of the body's immune response.³ Swelling and irritation occur due to a change in the natural gut bacteria interacting with the ileum.²

Symptoms of pouchitis

Inflammation of the ileal pouch causes the sensation of needing to go to the toilet more often and urgently.² It is common to also experience cramping and pain localised to the lower abdomen.³ Normal bowel habits can also change and include diarrhoea, incontinence, and blood in the stool¹. Other symptoms which can be experienced include:  fevers, chills, or weight loss.¹

Why is it important to get pouchitis diagnosed? 

Pouchitis can be treated with a course of antibiotics and therefore should be diagnosed to reduce the onset of symptoms.² Diagnosing and treating pouchitis can reduce the chance of further complications such as scarring, ulcers or failure of the ileal pouch.¹ There are also various types of pouchitis classified as idiopathic or secondary.⁴ The treatment options vary between these pouchitis types, and therefore, it is key to diagnose pouchitis accurately for effective medications to be prescribed.⁴

Preventive measures can be encouraged if pouchitis is diagnosed to lower the chance of it recurring. These can include taking prebiotics to increase the friendly bacteria in the gut⁵ or making changes to the diet, such as increasing fruit and fibre intake.³

Clinical evaluations 

What do clinical evaluations consist of? 

A doctor will first perform a clinical evaluation in a suspected case of pouchitis. This includes asking questions about your symptoms and taking a detailed medical history.² 

Blood and stool tests will also be conducted to support clinical evaluations to check for infectious bacteria that could be causing the inflammation.^1,6 This is particularly useful when determining the cause behind chronic pouchitis to prescribe an antibiotic selective to the bacteria.⁶

Risk factors 

During a clinical evaluation, the risk factors for pouchitis should be assessed to determine if the individual is likely to develop pouchitis. This includes having inflammatory bowel disease (IBD), taking nonsteroidal anti-inflammatory drugs (eg, ibuprofen).³ These are all features known to increase the chance of developing pouchitis. 

Endoscopy for diagnosing pouchitis

What is an endoscopy? 

An endoscopy is a type of internal examination that a doctor can perform. This includes using a small camera and a light on the end of a thin tube known as an endoscope.2 By inserting the tube through a natural opening, the doctors can look inside an individual and see the ileal pouch. Endoscopes can also retrieve a sample of the tissue, known as a biopsy,  from the ileal pouch to be taken for further testing.²

Key findings from endoscopies 

When an endoscopy is performed on someone with pouchitis, there are several signs that act as indicators for the disease. 

The ileal pouch can appear red when seen in an endoscopy.⁶ This is known as erythema and occurs due to increased blood flow to the site.⁷ Other abnormalities that can be seen through an endoscopy include the ileal pouch, which presents as patchy and rough in appearance.⁶ The tissue of the ileal pouch can also be fragile, such that it can bleed easily.⁶ Ulcers can also form on the tissue of the ileal pouch.⁶

Biopsies for diagnosing pouchitis

What is a biopsy? 

A biopsy involves studying cells or tissue taken from a patient to identify signs of disease.⁸ A sample of tissue from the ileal pouch can be taken by the endoscope during an endoscopy. Biopsies are studied with histological analysis, which involves using microscopes to examine samples.⁶

Key markers from biopsies

The biopsy can study similar markers for pouchitis as the endoscopy, such as ulcers and inflammation, but allows for greater description of the extent of these signs. Other signs that may be noticeable through the biopsy include areas of pus (crypt abscesses) or areas of immune cells (granulomas).^9,10 Changes in the normal expected tissue of the ileum could be identified, such as the presence of precancerous cells or the reduction of intestinal projections known as villi.⁹

Issues with diagnosing pouchitis

How to differentiate pouchitis from other diseases? 

The symptoms of pouchitis can be caused by a range of other diseases. Stomach cramping and abnormal bowel movements can be related to Crohn’s disease, irritable bowel syndrome, and cuffitis of the ileal pouch.^3,6 The latter describes a similar disease to pouchitis, but is the inflammation of the rectal cuff created in the surgery that forms the ileal pouch.¹⁰ A level of inflammation is expected after surgery to form the ileal pouch, and therefore, diagnostic techniques need to analyse the extent of symptoms.6 Furthermore, the key findings from endoscopies and biopsies are also non-selective for pouchitis.9 For example, the ulcers and damage to the ileal pouch could be caused by a lack of blood supply to the ileal pouch, known as ischemic damage.³

Due to the non-selective symptoms of pouchitis, diagnosis is confirmed by using multiple approaches such as symptoms, endoscopies and biopsies.⁴ Analysing the exact location and extent of inflammation using biopsies and endoscopies can differentiate pouchitis from cuffitis.⁶ Crohn’s disease of the ileal pouch is distinguished by clusters of white blood cells known as granulomas, identifiable through a biopsy.^6,10 Clinical evaluations can also be used since some substances found in faeces from stool tests are accurate indicators for Crohn’s disease.⁶

Irritable pouch syndrome is similar to irritable bowel syndrome, known as IBS.⁷ Irritable pouch syndrome produces similar symptoms to pouchitis and therefore would be difficult to distinguish the two from a clinical evaluation of symptoms and medical history alone.⁷ Biopsies and endoscopies are key here to differentiate irritable pouch syndrome from pouchitis, since these often show no histological signs of inflammation.⁶

Diagnosing pouchitis requires multiple approaches to find signs of the disease. By gathering enough evidence, other, very similar diseases can be ruled out to correctly diagnose pouchitis. 

Alternative approaches for diagnosing pouchitis 

Other techniques may be required to support the diagnosis of pouchitis. Other methods can include imaging scans of the ileal pouch, such as pelvic MRI and CT scans.¹ An x-ray of the ileal pouch can also be taken using a contrast solution, known as a pouchogram.¹ These can produce pictures of the ileal pouch to show structures like abscesses that could be indicators of pouchitis.⁶ While these are useful techniques, they are less commonly used in pouchitis diagnosis.⁶

Indexes for diagnosing pouchitis 

Numerical measuring scales have been developed to support the diagnosis of pouchitis. This includes the pouchitis disease activity index, termed PDAI for short.³ This is a three-part ranking system where symptoms, endoscopy and histology can be scored out of six points each.4 A total score of seven or more indicates the individual could be suffering from pouchitis.³ Since the findings from symptoms, endoscopies and histology are not specific to pouchitis and can be caused by other diseases, this metric is not commonly used in clinical practice.⁶

Conclusion

Pouchitis is the inflammation of the ileal pouch.¹ The main approaches to diagnose pouchitis include clinical evaluations, endoscopies and biopsies.² Clinical evaluations allow doctors to assess your symptoms and risk factors associated with the disease. An endoscopy will allow a doctor to visualise the ileal pouch and identify physical signs of pouchitis, including inflammation or redness.⁴ Endoscopies can retrieve a biopsy sample to be studied for indicators of pouchitis that appear as abnormalities in the ileal pouch tissue. The symptoms of pouchitis are similar to other diseases of the ileal pouch, such as cuffitis, Crohn’s disease of the ileal pouch and irritable pouch syndrome.^3,6 Therefore, multiple approaches are required to correctly diagnose pouchitis.