Laparoscopic cholecystectomy is one of the most frequently performed laparoscopic procedures worldwide. Failure to recognize the biliary anatomy represents the most frequent causes of iatrogenic biliary tree lesions, which are feared complications during laparoscopic cholecystectomy, with an incidence ranging from 0.15 to 0.6%. Near-infrared fluorescence (NIRF) cholangiography using intravenous ICG injection has been successfully studied in clinical trials as an efficient means to visualize the biliary tree during cholecystectomy. However, one of the most significant drawbacks of fluorescence cholangiography following systemic ICG injection is related to the high affinity of ICG to hepatocytes which yields an intense background fluorescence signal, due to the accumulation of ICG in the liver. A solution is to optimize the timing of ICG administration by injecting the dye prior to surgery, which has shown to improve the visualization of the biliary anatomy and a decreased hepatic background fluorescence. Another method to visualize the biliary anatomy is the direct intra-gallbladder ICG injection which bypasses the drawback of hepatic background fluorescence.
The incidence of iatrogenic ureteral injuries is up to 8% in selected cohorts, with the majority of these injuries missed during the surgical procedure, which leads to worsened postoperative outcomes. The intraoperative identification of the course of the ureters is pivotal for the prevention of such injuries. Since ICG is exclusively cleared by the liver, it cannot be used for a non-invasive NIRF ureteral delineation due to the lack of its excretion into urine. Consequently, and in this respect, the use of ICG requires a direct intra-ureteral injection or a retrograde catheter insertion. Although effective, this method harbors potential complications related to the ureteral catheter insertion. Another clinically available dye is methylene blue, which is partially cleared by the kidney and was subsequently studied for NIRF ureteral imaging in preclinical and clinical studies, showing promising results. MB has a lower brightness and emits a fluorescence signal near the lower edge of the NIRF range. This requires the use of specifically developed equipment. Thus far, the equipment used in most studies was experimental and is not (yet) commercially available for laparoscopic use. To this end, several promising novel NIR dyes have been developed for near-infrared fluorescence imaging of the ureters showing successful ureteral delineation is experimental studies.
Urethral injury is a complication which may occur during perineal and transanal surgery. With the recent introduction of the TaTME technique most particularly, the incidence of urethral imaging has risen, mainly as a result of a failed visualization of the urethra in the transanal operative field. Several methods are explored to visualize the urethra such as “clotting” an indwelling catheter using a mixture of ICG and silicone or instilling a mixture of ICG and lubricant gel directly into the urethra. Another method is near-infrared fluorescent coating of the indwelling catheters with fluorescent polymer for the purpose of NIR imaging of the urethra which has shown successful results in cadaveric studies.
Endometriosis is defined as the presence of endometrial tissue outside of the uterine cavity. This is a disease affecting 10 to 15% of women in their reproductive age. Due to the polymorphic appearance of peritoneal endometriosis, it can be challenging to recognize these lesions intraoperatively, and as a result, these lesions may be missed during surgery when attempting to remove them. The postoperative recurrence of endometriosis is associated with incomplete resection during the initial surgery. Due to the hypo- or hypervascularization of these lesions, it is hypothesized that they may have an enhanced visualization under NIRF imaging. In the recent years, there has been an increased scientific interest in the use of NIRF imaging with ICG for this purpose, showing promising results in comparison to conventional white light imaging.