Intraoperative Fluorescent Molecular Imaging of Vascular Perfusion in Minimally-Invasive Repair of Ureteropelvic Junction Obstruction: an Evaluation of Pyelo-ureteral Anastomotic Viability Using Indocyanine Green Fluorescence in a Pig Model
Andres D. Silva, MD, Brian J. Minnillo, MD, Samantha Ganick, MD, Frank J. Penna, MD, Rian J. Dickstein, MD, Hiep T. Nguyen, MD
Children's Hospital Boston, Boston, MA, USA.
BACKGROUND: Dismembered pyeloplasty remains the gold standard for the treatment of ureteropelvic junction obstruction (UPJO), with a long-term success rate over 95%. Despite the high success rate, there are nevertheless cases of failures associated with the technique. While the etiology for postoperative anastomotic obstruction and pyeloplasty failure is unclear, one proposed cause is inadequate perfusion due to excessive ureteral and pelvic mobilization. Currently, there is no method of evaluating viability of the anastomosis during the time of initial surgery. We hypothesized that indocyanine green (ICG) fluorescence can predict intraoperative pyeloureteral anastomotic viability based on visualization of perfusion.
METHODS: Twenty swine underwent robot-assisted laparoscopic complete, unilateral ureteral ligation. Ten swine underwent robot-assisted pyeloplasty and ten underwent open dismembered pyeloplasty one week later, either with or without the assistance of molecular imaging. Two swine served as normal controls and did not undergo surgery. Molecular imaging with ICG was used intraoperatively to assess perfusion to the area of ureteral obstruction and to the anastomosis (Figure 1). Five mL of ICG (0.5 mg/kg) was administered intravenously immediately prior to imaging. Perfusion was visualized with the guidance of a photodynamic eye (Hamamatsu Photonics KK, Japan), which enabled televised live footage with optimized detection at a wavelength of 750 nm. Imaging served to guide the selection of the ureteral dissection limits and segment for anastomosis. One week following pyeloplasty the animals underwent renal ultrasound (US), intravenous pyelogram (IVP), molecular imaging of the repair, as well as urodynamics to assess patency. The animals were then euthanized and histopathologic samples were obtained.
RESULTS: The fluorescent intensity of the UPJO in all obstructed swine was diminished as compared to normal controls. Intensity of the anastomosis immediately post-repair was dependent on the technique used as well as the use of molecular imaging guidance prior to repair: robot-assisted laparoscopic pyeloplasty as well as use of an image-guided repair revealed a greater intensity of perfusion. Renal US, IVP, molecular imaging and urodynamics at one week post-pyeloplasty confirmed a patent and well-perfused repair in all swine.
CONCLUSIONS: Intraoperative fluorescent molecular imaging during pyeloplasty provides enhanced visualization of perfusion to the obstruction and anastomosis, which has the potential to predict and prevent postoperative obstruction and pyeloplasty failure.
Figure 1. A ligated ureter under tension by suture (left) revealing diminished blood flow to area (white arrow) and diminished perfusion to the pyelo-ureteral anastomosis (right, black arrow).