21/07/2026
For almost a decade, the doctrine of equivalents has been a powerful tool available to UK patentees. Following Actavis v Lilly, patent owners took comfort in the idea that competitors could no longer avoid infringing simply by making an immaterial change to a product.
However, the Court of Appeal’s decision in Salts Healthcare Ltd v Pelican Healthcare Ltd [2026] EWCA Civ 93 is an important reminder that this doctrine has limits.
The case concerned ostomy bags incorporating internal welded portions designed to improve the distribution of waste within the bag, reducing bulging and improving user comfort.
Salts alleged that Pelican’s ModaVi product infringed their patent GB2569212B both on a conventional interpretation of the claims and under the doctrine of equivalents. At first instance, the infringement claim failed, and Salts appealed.
The Court of Appeal upheld the finding of non-infringement and in doing so provided valuable guidance on both claim construction and the doctrine of equivalents.
Claim wording still matters
The issue central to infringement by equivalents concerned the claim requirement for a “weld portion” extending “away from the periphery” of the bag.
Figure 1 of the patent, reproduced below, illustrates weld portions 20, 22, 28 and 30.
The downwardly angled weld portions help prevent bulging when the bag contains waste.
In contrast, Pelican’s ModaVi product incorporated “lobe” portions (reference numeral 16), illustrated below, which were found to achieve substantially the same result in substantially the same way as the patented invention.
Salts argued that the skilled person would not understand the patentee to have intended strict compliance with the structural claim language.
The Court disagreed. It held that extending protection beyond the specific structural language chosen by the patentee would exceed the fair protection afforded to the patentee while undermining the reasonable degree of legal certainty owed to third parties. The structural limitations of the claims therefore remained decisive.
The decision serves as a reminder that careful thought should be given to whether claims define an invention by structural features alone or whether broader functional language could more effectively protect the inventive concept.
Think carefully before describing embodiments
The Court also attached significance to the fact that the relevant claim was limited to weld portions extending downwardly towards the bottom of the appliance, whereas that limitation did not appear in the other independent claims.
Importantly, the specification described alternative embodiments that the patentee ultimately chose not to claim. Those alternatives were therefore treated as having been deliberately left outside the scope of protection.
As Lord Justice Arnold observed, this was a strong example of the principle that: “what is disclosed in the specification, but not claimed, is disclaimed.“
For applicants, this highlights the importance of ensuring that the claims and specification are properly aligned. Describing commercially relevant alternatives without claiming them may provide competitors with a legitimate route to the alternatives, beyond the reach of the doctrine of equivalents.
Anticipate design-arounds
During drafting, applicants should also continually ask: “If a competitor achieves the same clinical benefit using a slightly different structure, do our claims still cover it?“
If the answer is no, broader or alternative claim formulations may be needed.
Med-Tech competitors rarely produce identical copies. Instead, they typically develop products that deliver substantially the same clinical benefit while making modest structural modifications. Patent applications should therefore consider next-generation products, foreseeable engineering modifications, and manufacturing changes which all achieve the same technical effect.
Alongside this, the drafting process is often conducted while products such as medical devices are still in development. The evolving and iterative nature of clinical trials may mean that what is viewed as the “best” embodiment at the time of drafting may not ultimately be the version that succeeds or reaches the market. Patent specifications should therefore be drafted with this in mind to accommodate developments through the clinical trials process.
This further reinforces the benefit of including broader, functional language together with advantageous or commercially relevant examples when drafting the patent specification. Not only will this allow the protection initially sought to encompass the evolution of a product, but also helps to address issues highlighted in this Decision – without disclosure in the specification of broader principles or examples, a court may treat specific claim features as essential.
As the judge stated in the Appealed decision, it would “have been straightforward for the patentee to formulate a claim by result …or to omit the word ‘downwardly’, but none of the asserted claims does that”.
Crucially, these considerations must be made during the drafting process and cannot wait until litigation. The dispute between Salts and Pelican demonstrates that successful patent enforcement often turns on decisions made many years earlier.
The decision provides an excellent opportunity for Med-Tech companies to review existing patent portfolios, and reflect on if the claims protect foreseeable competitor modifications, as well as whether the portfolio will remain commercially valuable as products evolve over the next five to ten years.
Final thoughts
While the doctrine of equivalents remains an important aspect of UK patent law, it is not a reliable safety net for claims that fail to capture commercially important variants. For Med-Tech innovators, the decision is a timely reminder that careful application drafting remains the best tool for protecting innovation and preserving a competitive advantage.
This content is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.
