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Why is my stoma getting bigger? Causes of stomas changing in size

All stomas vary in size and shape. Some protrude outwards and others can be flat or flush to your tummy. No two stomas are ever the same. A colostomy may often appear slightly larger as the surgery has been performed on the large bowel (colon), whereas an ileostomy (small bowel) or a urostomy are smaller in size. 

Another reason a stoma can vary in size is due to the type of surgery and stoma you have. For example, a loop stoma, which is often temporary, can be slightly larger and be more an oval shape compared to a permanent stoma.

Following surgery, it is perfectly normal for the stoma to reduce in size over the first 6-8 weeks. You will be closely monitored by your stoma nurse who will assist with adjusting your bag size accordingly and will also teach you how to measure your stoma yourself.

If you have had your stoma for a while now, you will likely be aware of the normal size of your stoma. However, changes can occur. We’ve outlined the main reasons for this below… 

Weight gain

If your stoma has increased in size, it may be worth considering whether you have gained weight recently? If so, this is the most likely reason your stoma has become larger. This is nothing to worry about, but make sure you measure your stoma size or ask your nurse to ensure the aperture (hole) in your stoma bag fits correctly around your stoma. Remember to check the flange is not resting on new skin folds/creases as well. On the other hand, if you have lost weight, your stoma may become smaller in size. 

If you are unable to measure your stoma yourself, contact your stoma nurse who will be able to help you and ensure that your stoma bag fits you correctly.

Swollen stoma

At times the stoma itself can appear swollen. It may be worth checking you are not constipated or have a blockage. On the other-hand it can shrink and become tight, if this happens, try to increase the amount of fluids you are drinking to ensure you have regular bowel movement.


A prolapsed stoma can be alarming as it can happen fairly quickly. Some prolapses can extend past 6 inches, which can make fitting an appliance very tricky. It can also become debilitating and reduce a person’s quality of life. The prolapse may be random and at times shrink back to original size, only to become larger again later. This quick fluctuation in size can make it difficult for the Stoma Nurse to measure accurately, so they will teach you how to measure your stoma yourself and how to make adjustments in your pouch system to accommodate the changes in size.

Depending on the severity of the prolapse, a referral can be made to the Surgeon for review, but is often not deemed as urgent unless your stoma changes colour or causes pain.


Parastomal hernias are caused when part of the bowel pushes through the muscle of the stomach (abdomen). Unfortunately, it can affect a large percentage of ostomates. Hernias can cause a bulge under the skin and as a result, they can then change the shape and size of the stoma making them appear larger and sometimes flatter.

Remember to contact your Stoma Care Nurse, so that they can give you tips to help prevent the stoma and hernia from getting worse. They will also be able to give you advice on a support garment for you to wear, which will help keep the hernia in place during the day time and will also help keeping your appliance/pouch in place.

If your hernia causes you pain, causes your stoma to change colour or stop working, you should contact your GP.

You can find out more about stoma hernias here.


As your abdomen grows during pregnancy, your stoma will also likely change shape and size. These changes are more obvious during the second and third trimester. It’s a good idea to contact your Stoma Care Nurse so they can monitor these changes and help with the fitting of your pouch throughout your pregnancy. Don’t forget…after the baby is born, your stoma may reduce in size once again.

Find out more about pregnancy with a stoma here

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