Renal clearance of fluorescent agents can compromise image-guided surgery along the urinary tract

To study the effect of renally cleared fluorescent agents on image-guided surgery along the urinary tract by using the renally cleared, non-tumour-specific, fluorescent dye fluorescein.

Sixteen patients who underwent robot-assisted radical prostatectomy (RARP) with lymph node dissection received an intradermal injection of fluorescein. The slow-release of the fluorescein from the skin into the lymph- and bloodstream were used as a pharmacokinetic model for slow release from receptor-targeted agents. The presence of fluorescein in the urine and the surgical dissection planes around the prostate (representative of cancer margins) during RARP were evaluated. Suction, gauze and irrigation were used to try and reduce fluorescent background signals according to standard operating protocol.

Fluorescein was detected in the urine in the bedside catheter bag after a median of 1.3 h after agent administration and in the surgical field after opening the bladder neck as part of RARP (median of 2.4 h after injection). Suction and application of gauze helped to reduce contamination, but suction combined with irrigation with lukewarm NaCl 0.9% was shown to be most effective. Fluorescein accumulation was seen in the tissue surrounding the bladder neck in 80% of patients.

Renally excreted fluorescent agents risk contamination of the surgical field and possible dissection margins along the urinary tract, a feature that, without proper counter measures, could compromise the accuracy of intra-operative imaging by creating false-positive findings. A clear example of this was the observed bladder neck staining with fluorescein.