The Ostomy Files: The Convexity Controversy

  For the past 50 years, convex ostomy pouching systems have been commercially available,¹ yet controversy lingers over when and how they should be used. Texts and clinical guidelines discuss the role of convexity but neglect to provide bedside caregivers with explicit instructions on exact assessment criteria that lead to specific convex product selection (eg, depth of convexity) to solve their patient's management problem.^2-4

Nearly half a decade of empirical experience with convexity had passed before Rolstad and Boarini took a theory-based approach to it.⁵ Two years ago, a consensus panel of Canadian ET nurses developed a standardized tool for the assessment for and use of convexity in ostomy care.⁶ Regardless, the fact remains that specialized and nonspecialized nurses in all care settings are challenged to make decisions about selecting clinically appropriate convex pouching systems for their patients with little-to-no evidence-based instruction. The reason for this is that the needs for convexity are exceedingly variable and difficult to quantify for general use, especially in the absence of valid data.

What is the Purpose of Convexity?

  Basically, convexity should furnish peristomal skin protection by providing a sustained and predictable wear time⁵ when deep or uneven topography is evident in the peristomal area and/or when stoma shape and size are variable. Convexity is often used for flush or retracted stomas - the intention is to increase protrusion of the stoma so that it rises above the surrounding surface and enhances efficient emptying into the pouch. Convexity is also used to match peristomal skin topography in stomas deep in skin folds by "reaching down" to the stoma. Additionally, convexity can provide support to unstable tissue around the stoma.

Successful Convexity

  To achieve these goals, a convex system must provide enough pressure around a stoma to make a good seal, "deliver" convexity directly at the base of the stoma with enough force to make it protrude and/or seal to the skin, and be flexible enough to conform and seal to variable tissue profiles during postural changes. Besides achieving specific clinical goals, the pouching systems also must be comfortable for the patient, inspire confidence and a sense of security, and be simple to use.

When is Convexity Used?

  Convexity is used with caution by some clinicians during the immediate postoperative period in response to concern that additional pressure at this time might disrupt peristomal sutures and cause mucocutaneous separation or that the additional pressure convexity provides might be uncomfortable on a postoperative abdomen. Other clinicians use convexity postoperatively on a routine basis, especially for obese patients, patients with retracted stomas, or on urostomies. The author is unaware of current research that would support or negate these practices or assumptions.

  More often, convexity is used 6 to 8 weeks after surgery as the stomal mucosa shrinks, the stoma becomes less budded, and/or the patient regains weight lost before surgery. Convexity often solves management problems for patients who are not candidates for surgical stomal revision but who are experiencing chronic leakage, shortened wear times, or persistent peristomal skin problems. What appears evident, however, is that the use of and need for convexity in ostomy management is increasing in our own country and worldwide.

Shortcomings of Convex Products

  Patients and clinicians report that most convex products are too rigid to fit into deep skin folds or crevices around the stoma. Rigidity prevents the faceplate from providing a secure seal on uneven peristomal skin and is uncomfortable for the patient as it "rocks" on the abdomen. Rigidity also can increase the potential for developing pressure ulcers in some higher-risk patients.⁶

  Because no manufacturing standard for "deep" or "shallow" convexity exists, convex products differ in depth and must frequently be supplemented with skin barrier pastes, strips, or other types of skin barriers to obtain a correct depth for the individual patient or accommodate oval or irregularly shaped stomas. Precut convexity precludes customization for unusual shapes or depth requirements. Additionally, many convex products "deliver" their convexity several centimeters away from the base of the stoma, rather than directly at the base of the stoma, interfering with the faceplate's ability to provide a secure and leakproof seal.

  Because not all supplemental products are precut, they often must be customized by the patient to meet individual needs to build up an effective depth of convexity. The use of cut-to-fit convexity and supplemental products that must be customized with scissors (ie, strips, wedges, and washers) can be difficult for patients with dexterity or visual problems.   Data gathered during patient assessment⁷ and a working knowledge of convex ostomy pouching systems guides decision-making in determining the optimal choices for providing convexity for the individual patient. Convex products are excellent problem-solving alternatives when flat systems or other product options do not provide a mirror image of the peristomal topography or provide an acceptable option for the patient. Today, even though some patients will not require convexity, it will be required by the majority of patients because of their individual abdominal and stomal characteristics.⁵

The Ostomy Files is made possible through the support of ConvaTec, A Bristol-Myers Squibb Company, Princeton, NJ.

1. Turnbull RW, Turnbull GB. The history and current status of paramedical support for the ostomy patient. Seminars in Colon & Rectal Surgery. 1991;2(2):131-140.

2. Wound Ostomy and Continence Nurses Society. Guidelines for Management: Caring for a Patient with an Ostomy. 1998. Available at: www.wocn.org.

3. Erwin-Toth P, Doughty DB. Principles and procedures of stomal management. In: Hampton BG, Bryant RA (eds). Ostomies and Continent Diversions: Nursing Management. St. Louis, Mo.: Mosby Year Book.1992:29-103.

4. Broadwell DC, Appleby CH, Bates MA, Jackson BS. Principles and techniques of pouching. In: Broadwell DC, Jackson BS, Eds. Principles of Ostomy Care. St. Louis, Mo.: The CV Mosby Company. 1982:565-643.

5. Rolstad BS, Boarini J. Principles and techniques in the use of convexity. Ostomy/Wound Management. 1996;42(1):24-32.

6. Canadian Ostomy Assessment Guide: Convexity. Sponsored by an educational grant from ConvaTec, a Division of Bristol-Myers Squibb Canada. 2001.

7. Turnbull GB, The ostomy assessment inventory: a data-gathering process to enhance appropriate pouching system selection. Ostomy/Wound Management. 1998;44(2):28-37.