Flat and Convex Ostomy Barriers Explained

The part of your pouching system that touches your skin has an important job: keeping output away from the skin around your stoma. Its shape matters. Flat and convex barriers are designed for different fitting needs, and neither is the best choice for everyone.

What is a flat barrier?

A flat barrier has a generally level adhesive surface. It may suit a stoma that protrudes adequately and an abdominal surface that allows a reliable seal. Your nurse will look at how the barrier sits around your stoma and how your abdomen changes as you move.

What is a convex barrier?

A convex barrier curves towards the body around the stoma. It can help direct output into the pouch in certain situations, such as a stoma that is flush with the skin or some types of creases and folds.

Convex products vary in depth, firmness, and flexibility. These differences affect fit and pressure on the surrounding skin. Ask your NSWOC to assess which option is appropriate, especially after surgery or if you have pain, damaged skin, or a changing abdominal contour.

Assess fit in more than one position

A surface that looks smooth while you are lying down may form a crease when you sit. Your nurse may assess you sitting, standing, and lying down to understand where output could get under the barrier.

Changing weight, a new bulge, or changes in your stoma can affect an established fit. Keep notes about when leaks happen and where you see output on the underside of the removed barrier. That information can help guide a reassessment.

Barrier shape and opening size are separate choices

Flat and convex describe the barrier's profile. Cut-to-fit, pre-cut, and mouldable describe how the opening is prepared. A pre-cut opening may be convenient once your stoma size is stable; a changing or oval stoma may need a different approach.

If your current system leaks repeatedly: Arrange a fit review rather than guessing at a deeper convex product or adding more pressure with a belt. The aim is a comfortable seal that protects your skin.

Sources & further reading

• Hollister Canada — Choosing an Ostomy Skin Barrier
• WOCN Society — Peristomal Skin Assessment Guide for Consumers

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