Why you might you need a convex stoma bag

22 April, 2026

By Jillian Matthew

Tidings contributor, Jillian Matthew, explains what convex bags are and how they can help certain ostomates.

Finding the perfect bag

There are lots of different reasons why finding the perfect stoma bag can be challenging. When you first have a stoma, it can be quite surprising to discover the range of options and different types of stoma bags that are out there, and that it definitely isn’t a case of one size fits all. There can be a lot of trial and error when trying different bags to find the one that suits you. Getting the right fit can depend on your body shape and your stoma shape, position and size – all of which can change over time.

The impact of not having a stoma bag that fits properly can include pancaking, leaking, and skin irritation. This in turn can limit your activities and make you wary of going out if you are worried about being able to find suitable toilets to change your bag. Finding a bag that’s comfortable and fits your body shape is so important and can make a huge difference to how you are able to live your life.

Convex stoma bags

Baseplates (also called wafers or skin barriers) are the part of the stoma bag that sticks to your skin around the stoma and connects to the bag. When you are in hospital for your stoma surgery, you usually wake up with a standard flat stoma bag attached. This is what I was given and used when I went home. However, my stoma is completely flush to my skin. I was getting a lot of pancaking and leaks under the baseplate because my stoma wasn’t protruding into the bag. It was only when I started to investigate this further that I found out about convex stoma bags and how these could help me.

Rather than being flat and flush against the skin, like a standard baseplate, convex baseplates are shaped into a dome that faces into the body. They are often flexible and mould to the shape of your body. Convexity provides pressure around the stoma, which allows the stoma to protrude further inside the bag. A variety of convex bags are available, including both soft and firm baseplates at different depths and which apply different amounts of pressure.

Reasons for needing convex stoma bags can include having a:

• flush stoma
• retracted stoma
• stoma in a flexible skin fold
• peristomal ulceration.[RU1.1]

If you recognise any of these issues and you think you might need a convex stoma bag, speak to your stoma nurse to get advice about it.

Convex baseplates for urostomies

For a urostomy, you need the stoma to stick out for urine to pour out into the bag and not seep under the baseplate and you may need stronger convexity, however firmer convexity can put more pressure on the abdominal area. There may be other options for you rather than a convex bag, depending on your own situation. As we all know, everyone’s stoma is unique!