A horseshoe kidney is a congenital anomaly in which the two kidneys fuse together at their lower poles, forming a U-shaped structure. It is the most common kidney fusion anomaly, occurring in approximately 1 in 400 people. While many people with horseshoe kidneys live normal lives without any problems, the unusual anatomy creates significant challenges when surgical treatment is needed for conditions like kidney cancer.
The most critical surgical challenge in horseshoe kidneys is the aberrant blood supply. Unlike a normally positioned kidney that receives blood through a single main artery, horseshoe kidneys frequently have multiple accessory arteries arising unpredictably from the aorta, iliac arteries, or other nearby vessels. Studies have shown that up to 89% of horseshoe kidney patients who develop renal masses also have aberrant blood vessels near the tumor.
If a surgeon does not correctly identify and control all arteries supplying the tumor before removing it, there is significant risk of uncontrolled bleeding. Incomplete arterial clamping can also mean the tumor does not become avascular during resection, increasing the difficulty of clean surgical removal. These challenges have historically led to horseshoe kidney cancer cases requiring more extensive surgery than would otherwise be needed.
This case report documents the first use of indocyanine green (ICG) fluorescence navigation during a robot-assisted partial nephrectomy in a horseshoe kidney, describing how this technology helped safely navigate the complex vascular anatomy and successfully remove a large tumor while preserving the rest of the kidney.
The patient was a man in his 60s who came to the hospital with severe abdominal pain caused by acute cholecystitis, an inflammation of the gallbladder. During imaging performed to evaluate his gallbladder, doctors discovered an entirely separate finding: a large mass within a horseshoe kidney that he had not previously known about.
CT imaging revealed a 75-millimeter solid enhancing mass in the left side of the horseshoe kidney. The imaging characteristics, including the pattern of blood flow through the mass on contrast-enhanced scans, were consistent with renal cell carcinoma. Importantly, there was no evidence of spread to lymph nodes or distant organs, making the tumor potentially curable with surgery.
The patient had several medical conditions including obesity, high blood pressure, and type 2 diabetes managed with diet and oral medications. He was also a former smoker. These conditions needed to be factored into surgical planning, as they influence anesthesia risk, healing, and the importance of preserving as much kidney function as possible.
The surgical complexity score for this tumor, assessed using the standardized RENAL nephrometry scoring system, was rated as the highest possible complexity category. This reflected the tumor's large size, its location crossing the central axis of the kidney, and its proximity to the collecting system. The team recognized from the outset that this case would require careful preoperative planning and advanced intraoperative technology.
Indocyanine green (ICG) is a fluorescent dye that, when injected intravenously, travels through the bloodstream and can be visualized using near-infrared light. The da Vinci robotic surgical system includes a feature called Firefly imaging that switches the camera between standard white light and near-infrared mode, causing ICG-perfused tissues to appear bright green while non-perfused (avascular) tissues appear dark.
In partial nephrectomy, the surgeon must clamp the arteries supplying the tumor before cutting it out, temporarily cutting off blood flow so the kidney becomes a bloodless field during resection. ICG fluorescence provides real-time visual confirmation that the intended arteries have been successfully clamped and that the tumor region is no longer receiving blood flow before the surgeon makes any cuts.
This real-time vascular confirmation is especially valuable in horseshoe kidneys because there may be additional accessory arteries that were not visible on preoperative imaging. If an unclamped accessory artery is still supplying the tumor, the ICG scan will show residual perfusion in the tumor area, prompting the surgeon to identify and clamp the additional vessel before proceeding.
In this case, an additional superior renal artery was found intraoperatively that had not been identified on the preoperative CT scan. The ICG fluorescence helped confirm that after clamping this additional vessel along with the main left renal artery, the tumor area was completely avascular, allowing for safe resection.
The robot-assisted partial nephrectomy was completed successfully. The tumor was dissected deep into the renal sinus fat and into the collecting system while carefully preserving the isthmus, the bridge of tissue connecting the two kidneys. The renorrhaphy (repair of the kidney after tumor removal) was performed using multiple suture layers to close the defect.
The total warm ischemia time, the period during which blood flow to the kidney is clamped and the organ is without circulation, was 53 minutes. This is longer than the ideal target of under 25 minutes but is not uncommon in complex cases and reflects the difficulty of resecting a large tumor in an anatomically complex kidney. The kidney was not cooled during this time, which would have been used to protect kidney function in planned prolonged ischemia cases.
Histopathology confirmed a chromophobe renal cell carcinoma measuring 75 millimeters, with no capsular, lymphovascular, or perineural invasion and clear surgical margins. Chromophobe RCC is generally considered to have a better prognosis than clear cell RCC, which was a positive finding for this patient's long-term outlook.
The patient recovered without complications. His postoperative creatinine level (a measure of kidney function) was only slightly higher than his preoperative baseline, indicating that the remaining kidney tissue was functioning well. He was discharged on day 4 after surgery and his first surveillance scan at 6 months showed no signs of cancer recurrence.
This report documents the largest tumor in the published literature to be safely removed with a robotic partial nephrectomy in a horseshoe kidney. Previous reports of similarly sized or larger tumors in horseshoe kidneys had required heminephrectomy, the removal of an entire half of the fused kidney. Preserving the horseshoe kidney structure while completely removing the tumor is a significant surgical achievement.
It is also the first reported case of ICG fluorescence navigation being used during robotic partial nephrectomy in a horseshoe kidney. The technology proved essential in this case by revealing an additional artery not visible on preoperative imaging and confirming complete vascular occlusion before resection began. Without ICG, the surgical team would have had no way to verify in real time whether all blood supply to the tumor was controlled.
Preoperative imaging with a dedicated arterial phase CT scan and multidisciplinary discussion in a urology unit meeting were credited as essential to the successful outcome. The surgical team had mapped potential scenarios, including the contingency plan for converting to heminephrectomy if needed, before entering the operating room. ICG fluorescence supported the decision to proceed with the less extensive partial nephrectomy.
The patient's personal account reflected a positive experience. He described the team as highly communicative and thorough in their explanations, which helped manage his initial anxiety about needing two procedures in close succession. His recovery was straightforward, and he described feeling surprisingly well following a surgery of this complexity.
The authors identify three core learning points from this case. First, patients must be thoroughly counseled about the risks and benefits of kidney-sparing surgery versus more extensive alternatives, ensuring that treatment decisions reflect both medical evidence and individual patient values and circumstances.
Second, ICG fluorescence is a valuable intraoperative tool for confirming vascular control before resecting deep or complex renal tumors. In cases with known or suspected aberrant blood vessel anatomy, such as horseshoe kidneys, this technology adds an important safety layer that reduces the risk of bleeding and conversion to more extensive surgery.
Third, appropriate preoperative imaging with arterial phase CT is essential for planning surgery in horseshoe kidneys and other anatomically complex cases. Multidisciplinary preoperative discussion, including contingency planning for unexpected intraoperative findings, is strongly recommended. No amount of intraoperative technology fully replaces thorough preparation before the procedure begins.