I have had my ileostomy for years and have been using a regular pre-cut flat flange. Lately I have been having more problems with leakage and someone suggested that I needed a convex flange. What is a convex flange?



Convexity is a different style of flange or pouching system, one designed to correct some problems related to ostomy care, such as leakage. There are many options when considering the use of convexity and it is important to ensure that your selection of convexity matches an assessment of your stoma, and the peristomal skin and contours. The following will describe convexity and the range of products, some considerations when selecting convexity, and possible concerns related to its use.

Flanges, or skin barriers, for ostomy care generally come in two styles: flat or convex. Flat literally means that when you look at the barrier from the side, it is flat in appearance: there are no bulges or protuberances seen on the sticky side of the barrier. Convexity, on the other hand, does have some degree of protrusion on the back (or sticky) side of the barrier. Ideally, stomas stick out above the level of the skin, have the opening right in the middle, above skin level, and the peristomal skin contours (the natural bumps and curves of your skin when you are lying flat, sitting, etc) are flat, regardless of your position. In these cases, flat flanges will generally suit your pouching needs. When your stoma and/or skin contours are less than ideal, then you may need to correct the problem with the use of convexity. The protrusion at the back of the flange places pressure on the skin around your stoma causing some changes to the characteristics of your stoma and/or surrounding skin. Convexity can give you a more secure seal and a better wear-time.

Convexity can serve a number of purposes: the pressure on the surrounding skin can provide sufficient tension to prevent the undermining of stool and a premature leak of the appliance. This works well when the stoma does not sufficiently protrude, is flush with the skin, retracted, or when the mouth (opening of the stoma) is tipped over and drains directly onto the skin. Convexity can also provide sufficient tension to flatten some peristomal skin creases/folds, creating a flatter pouching surface. Convexity may help to fill in gullies or craters that may surround the stoma: the contours of the appliance follow the contours of the gully, finishing with tension at the base of the stoma, hoping to prevent leaks. Lastly, convexity can make a stoma that tips down, tip up allowing the stool to drain more directly into the pouch, rather than dribble close to the inner flange edge, causing a leak.

As mentioned, there is a wide variety of convex options to help with your pouching. Convex products range from the simple addition of a barrier ring to the back of a flange, to integrated convexity (the convexity is already built into the flange), to an insert that can be added onto a flange. There is also variability in the degree or amount of protrusion that the convexity can provide, from light to deep. These variations in depth essentially allow for some level of customization for each individual, based on the assessment of the stoma and the peristomal contours.

Low-level convexity will correct minor problems such as small skin folds, or a stoma that tips over slightly. Low-level products include items such as Eakin™ Rings, Adapt™ convex barrier rings or convex inserts from ConvaTec™.

Medium-level convexity will correct the more significant issues such as poorly protruding stomas or skin creases. Medium convexity is usually integrated into the flange. Hollister’s New Image™ convex appliances or Coloplast’s Assura™ light convex are examples of medium convexity.

Deep-level convexity has the maximum degree of protrusion and is meant to correct more difficult problems such as retracted or protruding stomas with surrounding gullies, or fat folds that droop over the stoma. ConvaTec’s Convex-It™ and Coloplast’s Assura™ regular convexity are deep convex products. While most people can use the deep integrated convex flanges to manage their problems, on occasion, barrier rings may be added to these appliances to make the convexity as deep as possible. Belts may also be used to help secure the appliance against the skin and to accentuate the convexity.

While convexity can help to solve issues related to stomal construction and peristomal skin contours, its use can result in some other challenges. Convex flanges/appliances are more costly than their flat counterparts are. However, if you achieve a better seal with a convex appliance and your wear-time is longer than with a flat flange, it may end up being a cheaper alternative over time. Barrier rings can also be costly and sometimes it is cheaper to switch to a system with integrated convexity than to add a barrier ring to a flat system. Some creative mixing and matching of products can be done to achieve the best seal, but certain products have been designed to work only with a very specific flange. ConvaTec’s convex inserts are only to be used with their Natura Sur-Fit™ and AutoLok™ flat flanges. Your enterostomal therapy nurse may help you to determine the best solution.

Convexity can cause damage to the skin around the stoma. Too much convexity may result in pressure ulcers to the skin, making your pouching more challenging, causing pain, and requiring regular care by an ET or nurse. While pressure ulcers are rare, it is important that the correct level of convexity be chosen for you. Some people with inflammatory bowel disease are also prone to developing a skin disorder called pyoderma gangrenosum (PG). PG is a painful condition that starts out looking like purplish pustules then progresses to become an open ulcer. PG tends to happen in areas of trauma and, in the case of convexity, the tension generated by just using a product may be sufficient trauma to begin breaking down the skin. PG can be treated with medications, along with alterations in the pouching system. Your ET can help you to manage skin complications related to your pouching.

Convexity can also cause lacerations (cuts) to the stoma itself if you are using an incorrect size/flange opening. The opening of the flange should be 1/8 inch (3-4 mm) larger than the base of the stoma. If you size your flange exactly the same size as your stoma or a bit smaller, the rigidity provided by the convexity can rub against the stoma, causing a cut. You may or may not be aware of the cut: it typically does not cause pain, but you may notice unusual bleeding from your stoma. Your ET can help you to determine the best size of flange for you.

Convex products are commonly used by individuals with stomas and are often recommended by ETs to compensate for problems related to the stomal construction and/or peristomal skin contours. Because of the multitude of products, it is important that your stoma and the surroundings dips, creases and folds be properly assessed before determining the right product for you. Assessment of your stoma and skin contours should be while you are sitting, not when you are lying on your back. The sitting position gives the ET much more information about your stoma and the surrounding skin, and is critical for evaluating your product needs. You may also be asked to twist side-to-side, to lift your legs up, or to lean forward, all positions adding more information to make the best selection for you.

Convexity may be an option to help you with your pouching problems. Given the broad range of products, a thorough assessment by your ET will help to ensure the most appropriate product selection for you. Additionally you may want to consult our article on ostomy belts for more information.