AN OSTOMY is a surgically created opening in the abdominal wall through which bowel has been pulled to allow for the drainage of stool or urine.1 For the patient with an ostomy, a pouching system is required to contain the effluent and to protect the skin.2,3 (See Glossary of ostomy terms.) Selecting the right pouching system for a patient with an ostomy is important but not necessarily easy; making a good choice from the multitude of products available isn't always intuitive.4 The right system will ensure that the effluent from the stoma is contained, the patient's peristomal skin is well protected, and the pouching system can be changed on a predictable schedule.2 Failure to achieve these hallmarks of care can negatively impact peristomal skin and the patient's quality of life with a stoma.2,5
Pouching systems include a skin barrier (usually a hydrocolloid base) that protects the skin, and a pouch that contains the effluent. These pouching systems can be either one-piece (the skin barrier and pouch are inseparable), or two-piece (the skin barrier and pouch are separate but attach to each other through a coupling mechanism).2
Skin barriers essentially come in two shapes: flat or convex. This article reviews the advantages of convex skin barriers and their role in ostomy care.
Barrier selection considerations
The overarching goal of ostomy care is to achieve a secure and predictable seal of the selected pouching system.2,3 Having a secure seal allows the patient or nurse to change the pouch at planned intervals, not based on leakage. Changing the pouch at planned intervals helps protect the peristomal skin and contributes to the patient's confidence and quality of life.2,5
Unfortunately, the literature is replete with examples of high rates of peristomal skin complications ranging from 35% to 87%.6-9 Although multiple types of peristomal complications can occur for multiple reasons, incorrect barrier selection is one of the most important contributing factors.5
A common peristomal complication is irritant dermatitis, also known by the umbrella term of peristomal moisture-associated skin damage (PMASD).10 (See Looking at PMASD.) Irritant dermatitis results when effluent has contact with the skin, causing erosion of the epidermis and possibly dermis.11
In one seminal study, researchers found that 57% of patients with an ileostomy, 48% with a urostomy, and 35% with a colostomy had some degree of peristomal skin irritation.6 The researchers also determined that in 77% of cases, the skin disorder could be directly attributed to contact with the effluent.6
Irritated skin is typically moist, preventing adequate adhesion of the pouching system and leading to leakage.7 Redmond et al. identified some of the contributing factors to skin irritation, including inappropriate product use.5
Research has also identified the impact of pouch leakage and skin irritation on patient well-being.12 Richbourg and colleagues noted that 76% of patients with all types of stomas included in the small study experienced some degree of peristomal skin irritation, and 62% had experienced pouch leakage.12 Of those respondents, 54% reported that they no longer enjoyed their usual activities and 53% felt depressed or anxious.12 Confidence with the pouching system facilitates the patients' return to normal activities.5
Depending on stoma and patient characteristics, the early introduction of a convex barrier may contribute significantly to the prevention of leakage and protection of the peristomal skin.3,13 As the convexity corrects imperfections in the stomal protrusion and/or peristomal planes, it reduces the potential for leakage and subsequent skin damage.11 (See Picturing terminology.)
Understanding barrier shapes
Integrated convex skin barriers were developed in the 1980s in response to pouching challenges for patients.14 Flat skin barriers, which have been available since the 1950s, don't adhere well when the patient's peristomal skin contours aren't flat, leading to leakage and potential peristomal skin breakdown. Although clinicians creatively tackled these challenges by adding rings, belts, and additional adhesives to flat skin barriers to improve wear times, the introduction of integrated convex skin barriers was a substantial improvement in facilitating ease of care and better patient outcomes.13,15-18 That is, convexity was now built into the product in the manufacturing process.
Differentiating a convex barrier from a flat barrier is best appreciated when looking at the barrier from an angle. (See Understanding barrier configurations.) Flat barriers are literally flat, with no discernible protrusion on the adhesive side of the barrier. In contrast, a convex ostomy barrier has some degree of protrusion on the adhesive side; its curved or rounded shape gives the convex barrier its name. Convex products vary by manufacturer, each providing its own unique shape or depth of curve.
Flat barriers tend to work best in ideal situations: when the stoma is raised (protruding) above the level of the skin, the stomal os (opening of the stoma) is in the center, and the skin around the stoma is smooth and free from any irregularities such as wrinkles, creases, folds, or gullies.2,3 (See Comparing stomal characteristics and peristomal planes.) When the situation isn't ideal (that is, the stoma is flush or retracted, the stomal os isn't in the center or tips down, or surrounding skin has wrinkles, creases, and folds), then a convex barrier may be the better choice.2-4 Use of flat barriers in these imperfect situations may cause the barrier to “float” above the wrinkle, fold, or gully, or the inner edge of the barrier may rise above the level of the stomal os. Both circumstances contribute to the effluent undermining the barrier and result in leakage.
The stoma and peristomal planes should be assessed with the patient in the sitting position. Although ideal assessments would include a variety of positions such as supine, standing, and bending at the waist, the sitting position is the minimum required to identify any irregularities such as folds in surrounding skin.2,3 Assessing the patient in only the supine position would fail to show these important parameters and misdirect barrier selection.
Convex skin barriers are now available from almost all ostomy product manufacturers in both one-piece and two-piece pouching systems, and in some cases, as an accessory such as a barrier ring. Although the design of these barriers varies, they all generally serve a similar function: displacing skin folds or adding tension to the peristomal skin to ensure a good fit.
How does a convex barrier work?
Convex barriers help to correct the less-than-perfect stoma and/or peristomal planes, preventing stool or urine from seeping underneath the barrier. Applying tension to the skin around the stoma can also help to make minor alterations to the stoma; for example, helping the stoma to protrude slightly more or helping the stomal os to tip in a different direction so it can drain more directly into the pouch.19 Convexity can also flatten wrinkles and creases, hold folds open, fill a defective skin surface, or match the shape of the surrounding gully.19 Using an ostomy belt will accentuate the properties of the convex barrier, increasing the pressure provided by the barrier directly against the skin.2
How convex barriers differ
Many types of convex barriers are available. Each ostomy product manufacturer has its own unique configuration and style of convexity, allowing nurses to find the best match for their patient.
Many descriptors can be used to differentiate convex barriers from one another; the most commonly used are those that help to describe the depth of convex protrusion. Although all convex barriers protrude, each manufacturer's barrier will protrude in varying degrees. Some offer a “light” or low-level protrusion; others have medium or deep levels of protrusion. Unfortunately, no standardized measurements define low, medium, or deep, nor does a uniform means exist to match these depths of convexity to specific patient assessments or findings.19 Nevertheless, broad categorizations may be made. For example, someone with minor or small wrinkles and creases in the peristomal skin may benefit from a low level of convexity, while those with significant folds may have more success with medium or deep levels of convexity.2 Ideally, a wound ostomy and continence nurse (WOCN) could help provide a full assessment and determination of convexity needs. The following organizations can help provide access to a WOCN or an enterostomal therapy nurse (ETN):
- In the United States, a WOCN may be found by accessing the website www.wocn.org/?page=nurse_referral.
- In Canada, an ETN may be found by accessing the website https://members.caet.ca/etfinder.
How to decide if convexity is needed
A focused stoma and peristomal assessment is recommended for all patients to determine the correct pouching system.2,20 Sitting is the optimal position for patient assessment because it best illustrates the “worst case scenario” and reveals any stomal and peristomal changes that indicate the need for a convex skin barrier.2
When assessing the patient, it's also important to determine the stoma type: Is it an end stoma or a loop stoma? An end stoma has a single os. Loop stomas have two openings side-by-side, and both openings need to be assessed. To determine the patient's need for convexity, see Key assessment indicators.
Convex skin barriers aren't without risks or negative consequences. Most convex skin barriers are constructed using integrated plastic, convex-shaped inserts with the physical attributes of rigidity and pressure. These characteristics may contribute to the development of a stomal or peristomal complication. Unfortunately, the literature is sparse and primarily relies on anecdotal evidence to support the claims of a complication. Being aware of potential complications is prudent so that product adjustments can be made.
One consequence of using a convex product may be the impact on patient comfort. Flat skin barriers are usually more supple and flexible compared with convex skin barriers. This can become more evident for patients who transition from a flat skin barrier to a convex one. Patients may report feelings of pressure or stiffness as a result of the convex barrier use.21 This can sometimes lead to poorer adherence to therapy when using convexity and should be addressed as part of patient assessment and education. Some patients resist suggested changes in their new regimen, even if it improves their skin and wear time; some return to their former pouching system.
Peristomal pressure injuries are a risk due to the rigidity of the convex barrier and the pressure it exerts. The recorded frequency of these events is relatively low (0.03%).22
Convexity either causing or worsening existing mucocutaneous separation in the immediate postoperative period has been described, but again evidence supporting the validity of this concern is lacking.18,23 A recent international consensus panel on convex ostomy products indicated that postoperative use of convexity can be considered.20 Stomal lacerations may occur from incorrect fitting of the barrier opening and the rigidity of the convex insert.19
Limited evidence suggests that convexity may contribute to development of peristomal pyoderma gangrenosum.23 Other skin conditions such as caput medusa and peristomal Crohn disease may be exacerbated by the use of convexity, although little evidence on these potential adverse events is available. If these conditions are already present and convexity is required to manage the patient, use convexity with caution and routinely assess the patient for such adverse events such as peristomal bleeding or ulcerations.
For several decades, convexity products have been used safely and successfully to improve wear times, prevent leakage, and improve patients' quality of life. Choosing the right type of ostomy product depends on a focused assessment of the stoma and the peristomal planes. Gaining experience with the differing types of convexity is an ongoing process, particularly as new types of convex skin barriers are introduced to better manage patients.
Looking at PMASD
PMASD is identified by erythema or the superficial loss of skin, typically in the area immediately around the stoma.10