Background The aim of this systematic review was to identify all methods to quantify intraoperative fluorescence angiography (FA) of the gastrointestinal anastomosis, and to find potential thresholds to predict patient outcomes, including anastomotic leakage and necrosis. Methods This systematic review adhered to the PRISMA guidelines. A PubMed and Embase literature search was performed. Articles were included when FA with indocyanine green was performed to assess gastrointestinal perfusion in human or animals, and the fluorescence signal was analysed using quantitative parameters. A parameter was defined as quantitative when a diagnostic numeral threshold for patient outcomes could potentially be produced. Results Some 1317 articles were identified, of which 23 were included. Fourteen studies were done in patients and nine in animals. Eight studies applied FA during upper and 15 during lower gastrointestinal surgery. The quantitative parameters were divided into four categories: time to fluorescence (20 studies); contrast-to-background ratio (3); pixel intensity (2); and numeric classification score (2). The first category was subdivided into manually assessed time (7 studies) and software-derived fluorescence–time curves (13). Cut-off values were derived for manually assessed time (speed in gastric conduit wall) and derivatives of the fluorescence–time curves (Fmax, T1/2, TR and slope) to predict patient outcomes. Conclusion Time to fluorescence seems the most promising category for quantitation of FA. Future research might focus on fluorescence–time curves, as many different parameters can be derived and the fluorescence intensity can be bypassed. However, consensus on study set-up, calibration of fluorescence imaging systems, and validation of software programs is mandatory to allow future data comparison.

Aim In this systematic review we aimed to identify all quantitative fluorescent parameters of intraoperative fluorescence angiography (IFA) during gastrointestinal surgery to pave way for a threshold that could predict anastomotic leakage (AL). Background &Methods In the last decade quantification of IFA using indocyanine green is attempted to objectively evaluate anastomotic perfusion during gastrointestinal surgery. In this systematic review, we adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A literature search of PubMed and Embase was performed. Articles were included when IFA was performed to assess gastrointestinal perfusion in both animal and human and analysed the fluorescence signal using quantitative fluorescent parameters. A fluorescent parameter was defined as ‘quantitative’ when a diagnostic numeral threshold for AL could potentially be produced. Results Some 1317 articles were identified, of which 23 were included in this review. Eight applied IFA during upper and fifteen during lower gastrointestinal surgery. The quantitative fluorescent parameters were divided into four categories: (1) time to fluorescence (n=19), (2) contrast-to-background ratio (n=3), (3) pixel intensity (n=3), and (4) numeral classification score (n=2). The first category was subdivided into (a) time to fluorescent enhancement (n=7) and (b) fluorescent-time curves (n=12). Thirteen studies correlated the fluorescent parameters to the occurrence of AL. Cut-off values for AL were derived for time to fluorescent enhancement (speed in gastric conduit wall) and derivatives of the fluorescent-time curves (Fmax, T1/2, TR, and slope). Conclusion Of the four categories, time to fluorescent enhancement seems the most promising quantitative parameter for clinical usage, as development of a cut-off value is possible on a large scale in the near future and no software is required. Future research might want to focus on fluorescent-time curves, as many different parameters can be derived and the fluorescence intensity can be bypassed. However, consensus on study set-up, and calibration of the different fluorescent imaging systems and software programs is mandatory to allow future data aggregation.