2. Methodology
2.1 Data identification
For these 2026 Guidelines on Intravesical Instillation, new and relevant evidence has been identified, collated and appraised by means of a structured assessment of the literature. A broad and comprehensive scoping exercise covering all areas of the Guidelines was also carried out. Databases searched included Medline, EMBASE the Cochrane Libraries and CINAHL, restricted to the English language and covering a time frame between January 2015 and 1 June 2024. A total of 1,955 unique records were identified, retrieved and screened for relevance. The Working Group added relevant references that were received after the search period during the document review. A total of 66 new references were added to the 2026 Guidelines. Detailed search strategies are provided in Appendix 1.
Recommendations within the Guidelines are developed by the panel to prioritise clinically important care decisions. Recommendations in this text are assessed according to their level of evidence (LE) and Guidelines are given a grade of recommendation (GR) according to a classification system based on the Oxford Centre for Evidence-Based Medicine Levels of Evidence [1].
Table 1. Level of evidence*
| LE | Type of evidence |
|---|---|
| 1a | Evidence obtained from meta-analysis of randomised trials |
| 1b | Evidence obtained from at least one randomised trial |
| 2a | Evidence obtained from one well-designed controlled study without randomisation |
| 2b | Evidence obtained from at least one other type of well-designed, quasi-experimental study |
| 3 | Evidence obtained from well-designed, non-experimental studies, such as comparative studies, correlation studies and case reports |
| 4 | Evidence obtained from expert committee reports or opinions or clinical experience of respected authorities** |
Table 2. Grade of recommendation*
| Grade | Type of evidence – Nature of recommendation |
|---|---|
| A | Based on clinical studies of good quality and consistency addressing the specific recommendations and including at least one randomised trial |
| B | Based on well-conducted clinical studies, but without randomised clinical trials |
| C | Made despite the absence of good quality, directly applicable clinical studies |
* Modified from [1]
**Including qualitative studies
2.2 Review
This 2026 publication was peer reviewed prior to publication. A blinded review was carried out by specialised nurses and urologists in various countries. A final version was approved by the EAUN Board.