Methylene blue fluorescence of the ureter during colorectal surgery

Iatrogenic ureteric injury is a serious complication of colorectal surgery. Incidence is estimated to be between 0.3 and 1.5%. Of all ureteric injuries, 9% occur during colorectal procedures. Ureteric stents are utilised as a method to reduce the risk of injury; however, these are not without risk and do not guarantee prevention of injury. Fluorescence is a safe and effective alternative for intraoperative ureteric localisation. This proof of principle study aims to assess the use of methylene blue to fluoresce the ureter during colorectal surgery.

Patients undergoing elective colorectal surgery were included in this open label, non-randomised study. Methylene blue was administered intravenously at varying doses (0.25-1 mg/kg) over 5 min, 10-15 min prior to entering 'ureteric territory.' Fluorescence was assessed using the PINPOINT Deep Red laparoscopic system at fixed time points by the surgeon and an independent observer.

42 patients received methylene blue; 2 patients were excluded from analysis. Of the 69 ureters assessed, 64 were seen under fluorescence. Of these, 14 were not visible under white light. 50 ureters were observed with both fluorescence and white light with 14 of these being seen earlier with fluorescence. In ten cases, fluorescence revealed the ureter to be in a different location than suspected.

Fluorescence is a promising method to allow visualisation of the ureter, where it is not identified easily under standard operative conditions, thereby improving safety and reducing operative time and difficulty.