For many individuals the prospect of living life with a stoma is daunting: the alteration to one's body image can be challenging and the necessary adjustment to lifestyle can be difficult. It is, however, widely accepted that the support of a specialist stoma care nurse (SCN) is advantageous, and positively impacts on a patient's quality of life (Claessens et al, 2015; Association of Stoma Care Nurses UK (ASCN UK), 2019). Support is offered in many ways; for example, patients can be provided with psychosocial support, as well as physical and practical support—all fundamental aspects of care. The ASCN UK (2021)Stoma Care Nursing Standards and Audit Tool (Quality Statement 7) states that people living with a stoma should have access to long-term/lifelong specialist SCN support.
Such support is necessary throughout a patient's time of living with a stoma, but it is even more crucial when a patient has issues with their stoma management. Patients can experience leakage from their appliance for many reasons, a discussion of which is beyond the scope of this article. However, where patients are able to access the input and support of a specialist SCN, these problems should hopefully be short lived.
One possible solution to minimising leakage is the use of a convex appliance—such products first became available about 30 years ago (Breeze, 1994). In 2005, a large study by Cottam et al (2007) looked at the number of people with newly formed stomas: an audit was undertaken in the first few weeks after surgery which recorded data for 3970 newly formed stomas across 256 UK hospitals. More than one third (n=1329) of the stomas were recorded as having a problem. Among the stoma types that more commonly require a convex appliance are necrotic stomas, which may then retract. In the study by Cottam et al (2007), there were 116 patients and 538 patients with necrotic and retracted stomas respectively, thus about half of the patients in this study would potentially require a convex appliance.
When looking at the literature for articles on convexity to underpin the use of convexity in clinical practice there is limited data available. Articles were predominantly descriptive rather than research based, correctly highlighting the use of convexity in clinical practice. This led to the need for the development of an evidence-based guideline to support nurses in clinical practice.
What is a convex stoma appliance?
The correct choice of pouch is essential and should be based on the type of stoma (colostomy, ileostomy or urostomy) created. A stoma appliance, also known as a bag or pouch, is generally made up of a flange or baseplate and a collection pouch or bag. Some pouches are single use and are changed and discarded. For those which are reused, the pouch will also have a mechanism for emptying: if the appliance needs to drain urine or a watery effluent (such as for a person with a high-output ileostomy), this will be an outlet tap or bung; if it needs to drain thick liquid stool (for people with an ileostomy), the pouch will have a re-sealable opening. Patients can choose whether the flange and bag are combined (one-piece pouch) or separate (two-piece pouch).
The flange or baseplate can be flat or convex (see Figure 1). A convex baseplate is dome shaped and faces into the abdominal wall—it sits close to the stoma, pushing into the peristomal skin, to increase stomal protrusion; this helps to make the stoma appliance more secure, reduce leakage and minimise potential skin damage. The degree of convexity required to achieve the best fit for an individual patient will be ascertained once assessment of the stoma and peristomal skin has taken place, but the depth of convexity can vary from one company's product to another. Soft, light/shallow and deep convex products are available in various plateau sizes (ie the diameter of the raised part of the stoma flange). Soft products are made without hard plastic to keep the shape of the convexity, the convexity of light products are only a few millimetres in depth and deep products have a convexity depth of around 1cm.
Figure 1. Example of appliance with a convex baseplate
A literature review by Hoeflok et al (2013a) outlined how it is thought convexity might work. The suggestion is that a convex appliance may help resolve uneven skin contours by flattening creases or, alternatively, the convex shape may fill any skin defect by pushing into the abdominal wall, increasing stoma protrusion and/or keeping stomal output further away from the skin (Cronin, 2005). Although there is no definitive reason why convex products are effective, it is likely related to increased stoma protrusion. However, this type of product is the only option for many people living with a stoma.
Numbers of patients requiring convexity
A postal questionnaire survey by Redmond et al (2009) of about 2000 people living with an ileostomy in the UK had a response rate of 52% (n=1035). Of these, 25% (260/1035) used a convex appliance. This study also found that people who used convexity were more likely to use additional products than individuals who had a flat flange. For example, a flange extender was used by 31% of people who used a convex product compared with 23% who used a flat flange. The reason for this is unclear but it could be due to fear of further leakage if this has been the patient's previous experience. Flange extenders can secure the outer edges of the flange over the patient's abdominal contours, increasing security and reducing leaks. Although respondents in Redmond et al's (2009) survey who used a convex product were more likely to report appliance leaks and have peristomal erythema than those using flat appliances, it was rare for these patients to ask a specialist SCN for assistance.
A small study by McPhail et al (2014) looked at urostomists with a flat or retracted stoma. In this study, 45 out of 47 patients felt more secure using a convex product, further adding to the body of evidence for the advantages of using this type of appliance. A comparison of these UK findings with those from recent European research from Sweden and Denmark (Correa Marinez et al, 2021) shows similar patient numbers using a convex appliance. Correa Marinez et al (2021) found that 38 (19%) of 201 patients across the two countries used convexity within the first 12 months following surgery.
The above findings indicate that patients feel that convex products can help increase security and reduce appliance leakage, but also that additional products may be necessary to enhance the efficacy of convexity appliances. Conversely, use of a convex product may reduce the need for additional products, thus careful assessment is necessary to determine the reason for appliance leakage.
Gaining convexity knowledge
Most of the specialist knowledge gained by nurses about stoma products, including convex products, is the result of hands-on experience, which may include a degree of trial and error. According to a survey by Perrin (2016), other routes to gaining this knowledge were peer learning from senior colleagues, reading about convexity and receiving updates from company representatives.
The educational needs and preferences of individual specialist nurses will vary, so it is unlikely that one method will work for all specialist SCNs who need to increase their knowledge of topics such as convex appliances. It is essential that specialist SCNs have a thorough understanding of the potential consequences of using convexity in order to provide appropriate advice and cause no harm to their patients.
The need for convexity guidance
There is limited evidence on the reasons for the increased use of convexity. The available data indicate the need for a standardised approach to patient assessment when considering the use of convexity, which should include the criteria for patient selection and follow up, once convexity usage is established. These factors indicate that a clinical guideline is vital for supporting specialist SCNs in their practice, to guide their decision making. However, even when guidance is made available, many individual patient factors will influence decision choices on whether or not to use convexity, so it is not possible to standardise care across the board.
Patient assessment
A detailed and thorough individual stoma care assessment should be undertaken by a specialist SCN before a convex product is recommended or trialled by a patient (Boyd et al, 2004; Buckle, 2013; Hoeflok et al, 2013b; 2017). A consensus document by Hoeflok et al (2017) highlighted the professional opinions of leading specialist SCNs from many countries, concluding that it was necessary to remove the pouch to allow adequate assessment of the peristomal skin, along with any folds or creases in close proximity to the stoma. The Hoeflok et al (2017) consensus document also recommended that the patient is best assessed in a sitting position, because it was felt that this enables ‘optimal assessment of body contours and the position of the stoma within the abdomen’ (Hoeflok et al, 2017:59). It should be noted that some of the expert panellists contributing to the Hoeflok et al (2017) consensus document suggested that the patient should ideally be assessed in different positions, including lying down, standing, bending and sitting. Much of the assessment statements incorporated within this consensus document are aligned with the content of the new ASCN UK (2021) guideline on the use of convex products (available to members at https://ascnuk.com/).
In addition to the stoma-specific assessment, generic history taking is also necessary. This will provide a thorough and comprehensive assessment of a patient, and is part of a holistic approach for determining the rationale for using a convex appliance. Gathering information about the patient's perception of the problem and the frequency of pouch renewal, as well as additional product usage to resolve the problem, is essential. Medication and dietary assessment help build a picture of the problem, which might include a recent change in dietary intake. Furthermore, it is important to take into account the patient's technique and ability to undertake stoma care, including factors such as manual dexterity (Table 1). The ASCN UK guidance can then support nurses to determine whether a soft or a firm convex product would be most appropriate. According to the international consensus (Hoeflok et al, 2017), the specific type of convexity that would most benefit people requiring such a product is determined by the firmness of a patient's abdomen around the stoma.
Table 1. Assessing the patient's history
| Suggested action | Rationale | |
|---|---|---|
| Patient history | Determine history of the problem from patient/carer by asking questions relating to:
|
To determine the patient's perception of the problem(s) experiencedIdentify the symptoms associated with the issuesIdentify potential causes or predisposing factorsEstablish the patient's ability to manage independent stoma care |
For people with a firm abdomen around the stoma, soft convexity would be the option of choice, while for those with a soft peristomal abdomen a firm convexity would be the preferred option (Table 2). In a small French study by Rat et al (2018) 90% (36/40) of people with a colostomy or ileostomy described the use of soft convex appliances as comfortable or very comfortable. Furthermore, the use of soft convexity in this study resulted in fewer leaks, as reported by 70% of participants, and a greater feeling of security was reported by 75% of participants. This suggests that, when appropriately used, a soft convex appliance could be used to prevent problems.
Table 2. Assessing the abdomen
| Suggested action | Rationale | |
|---|---|---|
| Abdominal assessment | Observe the abdominal area while patient lies down, sits, bends and stands Identify the position of the stoma in relation to the following:
|
To assess the contours/topography of the abdomen and if/how it alters during movementTo identify the presence and extent of any factors that may support appropriate product choiceTo facilitate the development of an individualised care plan |
For all nurses, documentation is of vital importance as stated within the Nursing and Midwifery Council (NMC) Code (2018). Consequently, the specialist SCN must make an accurate record of the assessment undertaken.
When to use convexity
As previously stated, convexity may be necessary for a number of reasons: it could be due to an issue with the stoma itself or due to issues with the peristomal skin. The most common reason for using convexity is when a patient experiences repeated leakage (Cronin, 2008). Appliance leakage may be the result of a poorly formed stoma, for example, an ileostomy or urostomy that is poorly spouted. Cronin (2008) suggested that convexity can be useful when the protrusion of a stoma needs to be increased, for example in the case of a retracted colostomy, a flush ileostomy or urostomy. However, in practice, even a well-spouted stoma may require a convex appliance if there is leakage (Evans and White, 2020). This could be because leakage is more common with liquid outputs (Hoeflok et al, 2017). In other cases, the opening of the stoma may be positioned near the skin surface (Burch, 2019). All of these stoma-related issues might indicate the need for a convex appliance, and this is reflected, with the rationale for their use, set out in the new ASCN UK guideline.
Other reasons for appliance leakage may be related to the peristomal area and poor stoma siting. Many people do not have a flat skin surface around their stoma, and they may have visible creases as a result of scars, for example (Cronin, 2005). In addition, creases may appear only on movement or the patient may have dips, moats or a more generally irregular skin surface. In other cases, the skin surface may appear to be suitable for a flat appliance, but the use of a seal or paste fails to produce secure adherence between the skin and the appliance. The patient may also find a single convex product easier to manage.
How to use convexity
In most situations, convex appliances should be positioned close to the stoma to ensure effective pressure is exerted. The effectiveness of the convex product is increased if the pressure from the convex product is exerted as close to the stoma as possible; it is therefore important to choose the correct plateau size for the stoma size. A stoma belt can be used to increase the pressure applied to the peristomal skin by a convex appliance—it will hold the appliance in place and ensure it is closer to the abdominal wall. This adds security as well as potentially increasing the pressure on the skin around the stoma (Cronin, 2008).
Once a thorough assessment of a patient has been undertaken and convexity deemed necessary, it is important to ensure the patient understands the rationale for its use and can use the new products correctly. The possible negative aspects of using convexity should also be flagged up: the patient should be advised that skin damage can occur and that it is vital to check for problems at each appliance change. It is therefore essential to ensure that patients check their skin at each appliance change and contact their specialist SCN if they note any changes, such as bruising, indentation, skin erosion and ulceration. Regular review and observation of the stoma and peristomal skin by the specialist SCN is also recommended (see ‘Patient follow-up’ for patients with convex appliances section below).
Contraindications
Although guidance on the use of convexity is generally broad, specific situations merit a more conservative approach. For example, if the person with a stoma has an ulcer on their peristomal skin, such as one due to Crohn's disease or pyoderma gangrenosum, caution must be exercised. In this situation, any excess pressure from the convexity may prevent or delay healing or even worsen the ulcer. Patients with a parastomal hernia whose skin is thin and stretched should be carefully assessed prior to the use of a convex appliance. There is a risk that because the skin is already stretched it will be weakened by the use of such an appliance, putting the patient at greater risk of skin breakdown. Individuals living with a stoma who have visible veins around the edge of the stoma (peristomal varices and signs of caput medusa indicating liver disease) will be at risk of severe bleeding, which may be increased if convexity is applied (Coleman, 2020).
Mucocutaneous separation may occur in the immediate postoperative period and presents as a dehiscence of the abdominal wall from the stoma. Caution is needed as the degree of convexity applied may further increase the separation between the abdominal skin and the stoma. According to Boyd et al (2004), when convexity is used within the initial postoperative period, this may cause delay in the healing process at the mucocutaneous junction. Cronin (2008) described using convexity 5 days after a stoma was surgically formed and by the 8th day superficial separation between the stoma and the peristomal skin was observed; this healed 10 days later. It is possible that the use of convexity caused the separation, but in such cases it is important to consider that patients may have underlying risk factors, such as diabetes, being on steroid medication or having an underlying infection, all of which will have a detrimental effect on the healing process.
It is interesting to note that Perrin (2016) elicited the opinions of 24 stoma specialist nurses about when convexity should be used with newly formed stomas. The answers ranged from immediately to 2 weeks after surgery. Some of the nurses supported their decision by stating that alternative options may need to be tried and shown to be ineffective prior to using soft convexity on a newly formed stoma; others were, however, happy to use soft convexity in the immediate postoperative period if assessed to be clinically necessary. A degree of compromise may therefore be necessary to achieve security and improve patient confidence.
The Hoeflok et al (2017) consensus document states that convexity can be considered in the immediate postoperative period. In practice, specialist SCNs will need to exercise their judgement as to the benefits of using convexity to prevent leakage and peristomal skin complications, as well as to reduce the negative impact leakage can have on quality of life and improve patient confidence versus the potential risk of delayed healing. Additionally, consideration should be given to how best to assist patients to adapt to their stoma, an experience that may initially be negative due to a leaking appliance. Using other options to prevent leakage, such as filler paste or seals, might be more complicated for the patient and this is another consideration for the specialist SCN in determining whether convexity should be used in the postoperative period.
Patient follow-up
There is no clear guidance on how best to follow up people who need to use convex stoma products. One view is that additional follow-up is needed to ensure that the patient does not experience any adverse outcomes, such as peristomal skin damage, although there is no consensus on how to follow up patients who are using convex appliances, including how frequently it should take place.
The small audit by Perrin (2016) found that opinion was divided. Some nurses considered it important to review people who had just started using a convex appliance weekly, particularly in the case of patients with a newly formed stoma. Other nurses considered 6-month follow-up was adequate. Judgements regarding the interval of follow-up should be made after each review and assessment. Davenport (2014) suggested that, as a minimum, all patients should be reviewed once a year.
The need for guidance
The NMC (2018)Code states that, as nurses, we must make sure that any information or advice we provide is evidence based, including that relating to any healthcare products or services. In this context, it is vital that specialist SCNs undertake a comprehensive assessment of each patient and suggest the most appropriate stoma products for the clinical situation. However, there are few articles describing how an assessment should be implemented, documented and evaluated. An article by Boyd et al (2004) is one of those covering the issue, setting out a comprehensive protocol for thorough nursing assessment. This work is now over 15 years old and, despite its detailed summation, anecdotally it does not appear to have been widely accepted by specialist SCNs within the UK.
Hanley (2013) suggested that there was no consensus on protocols on the use of convexity and that there was a need for further research on the topic. This was supported by Perrin (2016), who suggested that further evidence should conceivably be facilitated by a leading professional body, such as ASCN UK. The new ASCN UK (2021) guideline on convexity, which has been peer reviewed and was devised by a small group of experts following extensive review of the available literature, serves to enhance the existing body of evidence on the topic. However, the guideline does not compensate for the lack of research-based evidence required to support its ongoing use. The ASCN UK acknowledges the need for further work and hopes to undertake more detailed work in future.
As things stand, the ASCN UK has a portfolio of guidelines written by experts within the stoma care specialty, all of which have been extensively peer reviewed before publication and that are re-reviewed every 3-4 years (https://ascnuk.com/). The inclusion of a convexity guideline offering recommendations for specialist SCNs in the use of convexity was proposed as a welcome addition to the ASCN UK guidelines portfolio.
Devising a convexity guideline has been challenging, as many individual factors can affect a nurse's decision. The convexity guideline was published in July 2021 and follows the same format as other previously published ASCN UK clinical guidelines.
The guideline sets out three sets of recommendations:
- Detailed assessment
- Clinical situations where convexity can commonly be indicated
- Best practice for choosing the correct convex product.
Detailed assessment
Detailed assessment provides the novice SCN with a process to follow. A step-by-step approach facilitates a comprehensive assessment and signposts key considerations that should be part of an assessment. The stoma-specific thought processes are highlighted like a decision tree, setting out specific actions and the rationale for these. Table 1 provides a brief guide to taking a patient's stoma management history, Table 2 sets out how to examine the abdominal skin around the stoma and Table 3 provides guidance on making a stoma-specific assessment. This information will be in addition to that obtained from undertaking a holistic patient assessment, and will provide details of, for example, comorbidities and any underlying conditions. It is also helpful to establish what is normal for the patient in terms of their management routine prior to implementing the use of a convex product.
Table 3. Assessing the stoma
| Suggested action | Rationale | |
|---|---|---|
| Stoma assessment |
|
To determine patient/carer's stoma care techniqueTo establish causative factors for the signs and symptoms identifiedTo identify any effect of the effluent on the skin barrier and the position of any leakage pattern |
Clinical indications for convexity
This convexity guideline documents many situations that may necessitate the use of a convex appliance, although the list is not exhaustive. It captures some important aspects of care, including the need to educate the patient/carer regarding care of their stoma and peristomal skin, as well as the need to reassess the need for convexity at an interval appropriate to each patient's individual requirements.
One scenario that illustrates a clinical indication for convexity is that of a patient (with any type of stoma), whose stoma opening (also termed the os or apex) is situated at or below the skin surface. Such a scenario may require, after careful assessment, the use of convexity even in the immediate postoperative situation.
Best practice for choosing the correct product
A plethora of convex products are available for individuals living with a stoma, and for those experiencing issues with stoma management such appliances undoubtedly greatly improve quality of life. It is not within the remit of the guideline to recommend specific products or manufacturers. The guideline suggests that after a detailed assessment has been completed, and the specialist SCN has concluded that a convex product is necessary, the general advice is to use the least depth/plateau of convexity in order to achieve the best outcome for the patient (Hoeflok et al, 2017).
This section suggests that it is important to ensure correct choice of a plateau size in accordance with the size and shape of the stoma, in combination with the information obtained from the assessment, to achieve the desired outcome. As previously stated, there is a paucity of research on convexity, so it is not possible to provide robust research-based evidence for the assessment and decision-making processes necessary to help decide whether or not a convex appliance is appropriate for a patient. However, the input of expert opinion into the content of this guideline contributes to a greater understanding of the topic and support for specialist SCNs in clinical practice. It can be seen that, despite the consensus on situations that indicated the need for a convex product (Hoeflok et al, 2017), that it is not possible to standardise care. The provision of a guideline will help to standardise current practice to some degree and enable specialist SCNs to support patients' use of convex appliances with a greater degree of confidence.
Education
Education to degree and master's levels allows nurses to undertake research dissertations, and the use of convexity would be an ideal subject to consider as it would enhance the body of knowledge surrounding the subject. Further education has enabled nurses to be involved in research, which has led to an increase in knowledge on stoma care-related topics.
Conclusion
While caring for an individual with a problematic stoma, it may be necessary to use a convex stoma appliance. In our specialty, stoma care nursing, there is a perception that the use of convexity is often beneficial for the patient: the use of such appliances results in fewer leaks and improved quality of life. However, as highlighted within this overview of the guideline, a thorough and detailed assessment should always be undertaken prior to initiating the use of convex appliances.
From the paucity of research and literature, it is clear that current practice is not strongly supported by either primary research or clinical guidelines. It is for this reason that the ASCN UK has published its convexity guideline this year to provide SCNs with guidance on assessing patients for, and helping them to use, convex appliances. The availability of this guideline, alongside the ASCN UK's portfolio of guidelines, will support the expert status of specialist SCNs and give them the confidence to undertake a comprehensive assessment and provide them with a rationale for the use of convex appliances.
Although the lack of available evidence makes it impossible to standardise care, the new guideline works towards increasing support for nurses in the assessment, choice of, and rationale for choosing, a product in caring for patients requiring a convex appliance for their stoma. Although there are a number of reasons why a convex appliance is useful, the most common reason is to prevent leakage of the content of an appliance on to the patient's peristomal skin or clothes.
KEY POINTS
- A common issue encountered by people with a stoma is an appliance leak
- Common causes for appliance leaks includes uneven skin, skin creases and poor adhesion between peristomal skin and the stoma appliance
- Specialist stoma care nurses are best placed to assess and resolve issues and complications related to the care of a stoma
- Guidelines help inexperienced nurses to assess and plan care
CPD reflective questions
- Is there relevant nursing guidance within your clinical workplace?
- Consider what guides your care-giving and assessment skill and how these could be improved
- What are the benefits to patient care that can be provided by guidelines?