Figure 1. Port placement and robot docking for a left robotic retroperitoneal partial nephrectomy. A, The mid axillary line, commonly coinciding with the tip of the 12th rib, is the initial landmark to determine the location for access to the retroperitoneum and camera port site. B, The relative positions of the balloon port (green), additional 8-mm robotic ports (red), and the 12-mm assistant port (blue). C, Depiction of robot docking with the axis of the da Vinci Xi boom in line with the anterior robotic ports. D, View after the robot is docked with instruments in place.

Figure 2. Depiction of the view of the retroperitoneum. The psoas muscle is maintained as the “floor” or the “horizon” while a transverse incision in made through Gerota’s fascia to enter the perinephric space.

Over the past 30 years, technological advancements of minimally invasive surgery have played a crucial role in decreasing the trauma and morbidity of kidney surgery. In concordance with this movement, there came a collective shift in preference from open retroperitoneal (RP) surgery for radical nephrectomy to a minimally invasive transperitoneal (TP) approach for partial nephrectomy. Although minimally invasive RP kidney surgery was described as early as the 1990s¹ and subsequent studies have reported no discernible difference in oncologic outcomes between approaches,² adoption of this surgery has been limited in the United States potentially due to technical challenges. Since the 2000s, the enhanced articulation of instruments, 3-dimensional view, and improved ergonomics of the robotic surgical platform have made minimally invasive RP kidney surgery not only a viable alternative to the TP approach, but arguably the superior option for certain cases such as partial nephrectomy for posterior and lateral renal masses.

Why RP Kidney Surgery?

Because the kidney is an RP structure, the ability to avoid the intraperitoneal space is associated with several key benefits. The RP approach allows for direct access to the renal hilum with preferential access to the renal artery, thus eliminating the need to mobilize intra-abdominal structures (bowel, liver, pancreas, spleen), which minimizes postoperative ileus³ and the risk for inadvertent injury.⁴ For posterior and lateral renal masses, the RP approach provides rapid identification and exposure in contrast to the TP approach which typically involves aggressive mobilization and rotation of the kidney. Overall, minimally invasive RP kidney surgery can improve surgical efficiency while decreasing patient morbidity.

Barriers to Minimally Invasive RP Kidney Surgery

Despite advantages to the RP approach described above, there are also inherent challenges which have likely slowed widespread adoption. Unlike minimally invasive TP surgery which accesses a potential space of the intraperitoneal cavity, minimally invasive RP surgery requires the creation of space in the retroperitoneum; this initial step must be navigated meticulously to avoid injury to the peritoneum as well as bleeding from RP vessels. While avoiding intraperitoneal organs with RP surgery is ideal from a safety perspective, there is more difficulty with establishing orientation due to that lack of anatomical landmarks. Furthermore, compared to the intraperitoneal cavity, the retroperitoneum is much smaller, which can lead to clashing of instruments and rapid loss of visualization when suctioning. Naturally, these challenges of lack of anatomical landmarks and limited working space are magnified for obese patients, especially those with abundant perinephric fat.

Overcoming Barriers to RP Kidney Surgery

Patient positioning and accessing the retroperitoneum

Like open RP kidney surgery, the patient is positioned in a full lateral decubitus position and the operating room table is flexed approximately 30°—with or without elevating the kidney rest—to ensure maximal space between costal margin and the iliac crest. Along the midaxillary line, 1.5 cm transverse incision is made midway between the 12th rib and the iliac crest (Figure 1, A); this incision can be moved to just below the costal margin if the target renal mass is at the upper pole of the kidney. Dissection is carried down with electrocautery to the RP space, which is then developed with a balloon dissector. Importantly, a camera placed within the balloon during dilation is useful to identify the psoas muscle, which reliably confirms that the correct space is being established. The balloon port is then replaced by an 8-mm robotic trocar, secured with an Intuitive Hasson cone or a balloon port, serving as the robotic camera port.

Maximize RP space and port placement

The location of the additional ports is then selected and positioned along a curvilinear line parallel to the costal margin separated by approximately 6 cm utilizing 3 robotic instruments and the camera (Figure 1, B). Once the 8-mm robotic port is placed posteriorly, a laparoscopic Kittner is used to sweep the peritoneum off the overlying transversus abdominus muscle until the most anterior robotic port can be placed without injury to the adjacent peritoneum. Toward the pelvis, the peritoneum is similarly mobilized to allow for placement of a 12-mm assistant port ∼2 cm anterior to the anterior superior iliac spine along the same sagittal plane of the most anterior robotic port (Figure 1, B). The robot is then docked with the boom angled along the plane of the anterior robotic ports to minimize clashing of the robot arms on the outside of the body (Figure 1, C). The use of a third instrument (eg, Prograsp retractor) located most anteriorly is essential to maximizing exposure during the case (Figure 1, D).

Orientation and identification of RP anatomy

Because the balloon dissection develops the inferior retroperitoneum, the robotic instruments are all located inferior to the kidney. For orientation, the psoas muscle is maintained as the “floor” or “horizon” on the screen. The “veil” in front of the camera is Gerota’s fascia. After making a transverse incision through Gerota’s fascia near the psoas muscle (Figure 2), the Prograsp forceps is passed into the perinephric space to elevate the kidney. While maintaining upward traction of the kidney, blunt dissection and electrocautery are employed to clear all the perinephric adipose tissue along the psoas muscle toward the pulsations of the renal hilum. To facilitate identification and exposure of the renal hilar vessels, it is helpful to position the Prograsp forceps to the medial aspect of the kidney and then retract anteriorly to create tension on the renal hilar vessels. Attention is then turned to identification of the renal tumor. It is important to resect perinephric adipose tissue off the renal capsule around the renal mass but avoid extensive defatting as this tissue can serve as a “handle” to optimally position the kidney for renal mass resection and repair of the parenchymal defect, which is performed similar to a minimally invasive TP kidney surgery.

The Future of RP Kidney Surgery

Recent technological advancements present exciting prospects for minimally invasive RP kidney surgery. Namely, the single-port surgery may serve to further minimize concerns about minimally invasive RP kidney surgery and further promote the approach. Single-port surgeries require reduced dissection compared to a multiport operation, and may result in reduced surgical trauma, decreased postoperative pain, and shorter hospital stays.⁵ As medical technology continues to evolve to provide more favorable patient outcomes, the advantages offered by an RP approach to kidney surgery will be increasingly apparent.