Milestones in Surgical Complication Reporting. Clavien-Dindo Classification 20 years & Comprehensive Complication Index (CCI®) 10 years

Objective: To provide improved guidance for the consistent application of the Clavien-Dindo classification (CDC) and Comprehensive Complication Index (CCI^®) in challenging clinical scenarios. Background: Standardized outcome reporting is key for the proper assessment of surgical procedures. A recent consensus conference recommended the CDC and the CCI^® for assessing postoperative morbidity. Several challenging scenarios for grading complications still require evidence-based guidance, and the use of the 2 metrics in randomized controlled trials (RCTs) remains unexplored. Methods: We assessed the use of the CDC and CCI^® as an outcome measure in a systematic literature search. In addition, we asked 163 international surgeons to critically evaluate and independently grade complications in 20 complex clinical scenarios. Finally, a Core Group of 5 experts used this information to develop consistent recommendations. Results: Until July 2023, 1327 RCTs selected the CDC and/or CCI^® to assess morbidity. Annual use was steadily increasing with now over 200 new RCTs per year. However, only a third (n = 335) of published RCTs provided the complete range of CDC grades, including all subgrades. Eighty-nine out of 163 surgeons (response rate: 55%) completed the questionnaire that served as a basis for the recommendations: repetitive interventions that are required to treat one complication, complications followed by further complications, complications occurring before referral, and expected and unrelated complications to the original procedure should all be counted separately and included in the CCI^®. Invasive blank diagnostic interventions should not be considered a complication. Conclusions: The increasing use of the CDC and CCI^® in RCTs highlights the importance of their standardized application. The current consensus on various difficult scenarios may offer novel guidance for the consistent use of the CDC and CCI^®, aiming to improve complication reporting and better quality control, ultimately benefiting all health care stakeholders and, first and foremost, all patients.