Introduction

The large intestine, also referred to as the colon, is an organ located in the abdomen, responsible for absorbing water and nutrients and removing waste from the body.^{1 2} It is lined internally by a mucous membrane, which, in certain conditions, can become inflamed, known as colitis. Colitis typically leads to watery diarrhoea, blood in stool, an urgent feeling to pass a stool even when the colon is empty, abdominal pain, fever, and tiredness. There are various types of colitis, which vary depending on what is causing the condition.³ One of these types is collagenous colitis, which was initially discovered in 1976, where deposits of collagen are found in the colon’s mucous membrane and cause it to become inflamed and not function as it normally would.^4,5

Causes of collagenous colitis

Collagenous colitis is a result of the deposition of collagen in the colon’s mucous membrane. However, what exactly causes this is not clearly understood, though theories have been proposed. One theory is that the condition is caused by a genetic abnormality. Another theory has linked the condition to smoking tobacco and the use of certain medications:^{4, 5}

• Non-steroidal anti-inflammatory drugs
• Proton pump inhibitors
• Statins
• Selective serotonin reuptake inhibitors
• Pembrolizumab

Signs and symptoms of collagenous colitis

Collagenous colitis can cause several signs and symptoms:^3,5

• Watery diarrhoea that often lasts longer than a month and where there are typically about four to nine bowel movements per day
• Blood in stool
• An urgent feeling to pass a stool even when the colon is empty
• Abdominal pain
• Fever 
• Tiredness

Diagnosis of collagenous colitis

Diagnosing collagenous colitis can involve a range of strategies, including a medical history, blood tests, stool studies, and a colonoscopy with a biopsy. There are several conditions that may need to be ruled out when confirming a diagnosis of collagenous colitis, such as:^{5, 6, 7}

• Coeliac disease - Coeliac disease is an autoimmune disease that damages the small intestine and is aggravated by glucose. Coeliac disease can cause diarrhoea similar to that occurring in collagenous colitis
• Crohn’s disease - Crohn’s disease causes inflammation of part of the small intestine and the large intestine. Similar to collagenous colitis, the condition can cause diarrhoea and abdominal pain
• Irritable bowel syndrome (IBS) - IBS is categorised into a few subtypes, one of which is characterised by a predominance of diarrhoea. Abdominal pain is a common feature of the condition too, making the condition’s signs and symptoms similar to those of collagenous colitis

Medical history

During a medical history, you are given an opportunity to share your thoughts about what you are currently experiencing regarding your health and ask any related questions. A physician may ask you questions about past medical conditions you have been diagnosed with, past procedures you have undergone, any medications you take, your social life, and any medical conditions that run in your family, as well as signs and symptoms you are currently experiencing.⁸

Blood tests

You may have a blood test taken in the process of diagnosing this disease. Some factors that may indicate the presence of collagenous colitis include a lower quantity of red blood cells, the presence of autoantibodies, and low levels of protein in the blood. During a blood test, a small amount of blood will be taken using a needle that is typically inserted into the region of the skin that is inside the elbow, which may cause a sensation similar to scratching as it pierces the skin. There may be some bruising or swelling in the region where the needle is inserted, though this typically subsides within a few days.⁵

Stool studies

A stool study involves you being asked to pass a stool into a sterile plastic container, which is sent to a laboratory to be analysed. The reason why a stool sample can be helpful in diagnosing collagenous colitis is because stool contains substances, such as bacteria and parasites, found throughout the digestive system, which can indicate what problems are occurring here. However, stool studies can often show no abnormality in the stool in the case of collagenous colitis, and so other tests are typically required.⁵

Colonoscopy with a biopsy

A colonoscopy can allow the inside of the large intestine to be viewed. A flexible, long, and thin tube, containing a small camera, is passed through the anus into the large intestine. Prior to undergoing a colonoscopy, you will be given laxatives so your large intestine is empty for the procedure. As well as this, prior to the procedure, you will be offered medication to help you have a comfortable experience. In the case of collagenous colitis, the view of the colon may appear normal or show lesions, redness, and swelling. 

During the colonoscopy, a biopsy will also be performed, where a small sample of tissue from the colon will be taken. This tissue sample will then be examined with a microscope, allowing for abnormalities of the colon to be seen in much more detail as cells can be examined, allowing for it to be determined whether collagenous colitis is present or not. Medication to prevent pain will be given before performing the biopsy.

Treatment of collagenous colitis

Collagenous colitis cannot be cured, but treatment can allow for signs and symptoms of the condition to subside. Treatment may initially involve stopping smoking tobacco or taking medications that may be worsening signs and symptoms. Following this intervention, medications serve as the key mode of treatment for patients. Loperamide, an anti-diarrhoea medication, is often initially prescribed, and if signs and symptoms persist, a medication called budesonide may be added to this regimen, followed by a medication called cholestyramine if signs and symptoms still do not subside. However, approximately 10 to 20% of patients do not respond to these medications and may require surgery.^4,5

Loperamide

Loperamide is an anti-diarrhoea medication. It slows down the movement of food in the body, allowing the large intestine to have more time to absorb water from food, causing your stool to be firmer and be passed less frequently. Though loperamide can be an effective treatment, it can cause several side effects:

• Constipation
• Nausea
• Headaches
• Faintness 
• Stomach pain

Budesonide

Budesonide is used to reduce inflammation. It is in a class of medications called corticosteroids, which mimic hormones naturally made by the body. It can commonly cause certain side effects including:

• Stomach pain
• Muscle pain
• Headaches
• Skin reactions
• Oral thrush

It is important when taking budesonide not to eat grapefruits or drink grapefruit juice as this can increase the likelihood of side effects occurring.

Cholestyramine

Cholestyramine may be prescribed in four daily doses if diarrhoea does not resolve with other medications. It binds to bile, which can subsequently lead to diarrhoea to resolve.⁵

FAQs

Can stress worsen signs and symptoms of collagenous colitis?

Stress has been associated with inflammation of the colon, though whether it plays a role in collagenous colitis specifically is not known.⁹ 

Can collagenous colitis be cured?

Collagenous colitis cannot be cured, but treatment can allow for signs and symptoms to subside.⁴

How common is collagenous colitis?

Collagenous colitis is not common, and how frequently it occurs varies depending on the country, though for every 100,000 people, it is thought to occur in 5 to 90 people. Middle-aged people assigned female at birth are most commonly impacted, but any age and gender can be diagnosed with the condition.³

Summary 

Collagenous colitis results from collagen being deposited in the mucous membrane of the colon. What causes this deposition of collagen is not completely understood but is thought to be associated with genetic abnormalities, smoking tobacco, and certain medications. Several strategies may be employed to confirm a diagnosis of collagenous colitis, including a medical history, blood tests, stool studies, and a colonoscopy to perform a biopsy. Treatment for collagenous colitis initially involves stopping taking substances that may be aggravating the condition and then medication, such as loperamide, budesonide, and cholestyramine, if signs and symptoms persist. Surgery is typically reserved for patients who do not respond to medication.