Key words : Case series, Complex iliac anatomy, Renal transplantation, Renal vein kinking, Surgical innovation, Vascular complication

Introduction

Kidney transplantation is the optimal treatment for end-stage renal disease, yet its success remains techni-cally dependent on a flawless vascular anastomosis. The venous anastomosis poses a particular challenge in recipients with a deep iliac vein or a bulky psoas major muscle, as this anatomy can cause renal vein kinking and thrombosis, threatening graft survival. While traditional maneuvers like vein mobilization and extensions are beneficial, they often fail to fully resolve the mechanical compression from a prominent psoas, creating a need for more targeted solutions.

To address this specific problem, we developed the psoas muscle groove technique. This novel approach involves creating a shallow, hemostatic groove in the psoas major to provide a protected, tension-free channel for the renal vein. By recessing the vein into this groove, the technique aims to prevent kinking, facilitate anastomosis, and optimize venous outflow without resorting to alternative strategies like intraperitoneal placement or inverted graft implan-tation, which alter the standard surgical field.

This study presents the first prospective evalua-tion of this technique. We hypothesized that, in patients with preoperatively identified challenging venous anatomy, the psoas groove would enable a safe, efficient, and kink-free venous anastomosis. This case series aims to describe the technique’s application and report its clinical utility and safety outcomes.

Materials and Methods

Study design and patient selection
This prospective case series was conducted at the Renal Transplant Center, Armed Forces Hospital Southern Region, between September 2017 and June 2025, after Institutional Review Board approval and informed consent were obtained. The study included 20 consecutive adult living related kidney transplant recipients with preoperatively identified challenging venous anatomy.

Definition of challenging venous anatomy
Complex venous anatomy in patients was determined preoperatively by using computed tomography and Doppler ultrasonography, which evaluated iliac vein depth, caliber, patency, tortuosity, and stenosis. Psoas muscle bulk and overall patient habitus were assessed, as hypertrophied psoas muscles in younger or muscular patients often indicate deep-seated veins prone to compression or kinking. A history of pelvic surgery, vascular interventions, or prior thrombosis was also considered suggestive of potentially difficult anatomy. Imaging from mid-L3 through the iliac bifurcation included measurement of bilateral psoas cross-sectional area and thickness to calculate the psoas muscle index, as well as visual assessment for prominent posterolateral psoas overhang. Iliac vessel depth (skin-to-EIV and psoas-to-EIV) and the course of CIV/EIV relative to the psoas were documented to anticipate challenging exposure and anastomotic angles.

Surgical technique
All patients underwent standard extraperitoneal transplant via an extended Gibson incision with wide retroperitoneal mobilization. The venous anasto-mosis was performed first, positioning the renal vein laterally and retracting the artery medially to optimize sightlines. In narrow or deep corridors, a Satinsky side-bite or staggered double clamps were applied to the external iliac vein.
A psoas groove was created when intraoperative assessment confirmed a deep external iliac vein causing acute upward angulation of the graft vein, prominent psoas overhang compressing the venous course, or a short renal vein that could not form a gentle curve without kinking. A shallow, hemostatic groove (~1 × 0.5 cm) was fashioned in the anteromedial psoas major with use of limited electrocautery, while avoiding muscle splitting and remaining superficial to protect the lumbar plexus. The renal vein was aligned flat and untwisted into the external iliac vein with an entry angle of ≤30 to 40° and rested recessed within the groove without torsion or kinking.

Data collection and outcomes
Data were collected prospectively. The primary intraoperative outcome was venous anastomosis time. Secondary outcomes included cold ischemia time, total operative duration, intraoperative blood loss, and incidence of vascular complications. Postoperative outcomes assessed were graft function (immediate function, serum creatinine, estimated glomerular filtration rate), patient and graft survival at 1 year, and all complications within 30 days.

Statistical analyses
Continuous variables were expressed as mean ± SD. Categorical variables were presented as counts and percentages. As this was a case series, descriptive statistics were primarily used. All analyses were performed using SPSS version 28 (IBM Corp).

Results

Patient cohort and baseline characteristics
All 20 patients with challenging venous anatomy successfully underwent kidney transplant with the psoas groove technique (Figure 1). The cohort had a mean age of 48.3 ± 10.5 years and included 14 male recipients (70%). The mean body mass index was 26.8 ± 3.2 kg/m², and the mean psoas muscle area was 18.9 ± 4.1 cm². Living donor transplants accounted for 65% of cases, with 60% of grafts transplanted to the right iliac fossa (Table 1).

Intraoperative outcomes
The psoas groove technique demonstrated excellent technical efficiency (Figure 2). The mean venous anastomosis time was 12 ± 4 minutes, with a corres-ponding cold ischemia time of 25 ± 6 minutes. The total operative duration averaged 210 ± 45 minutes, and mean intraoperative blood loss was 320 ± 110 mL. No instances of venous or arterial thrombosis occurred during the procedures.

Postoperative outcomes and complications
Postoperative outcomes were highly favorable. Immediate graft function was achieved in 19 patients (95%). No cases of delayed graft function occurred, although slow graft function was observed in 1 patient (5%). At 1-year follow-up, graft survival was 96.4% and patient survival was 96.4%. Renal function remained excellent, with a mean estimated glome-rular filtration rate of 89 ± 15 mL/min/1.73 m².Complication rates were low and manageable. One patient (5%) required reoperation for posto-perative bleeding, and 1 patient (5%) developed a lymphocele requiring drainage. No urinary leaks, surgical site infections, or neurological complications related to the psoas groove creation were observed.

Discussion

This prospective series validates the psoas groove technique as an effective solution for a well-recognized surgical challenge. The bulky psoas major fundamentally alters surgical dynamics by displa-cing iliac vessels posteriorly, compromising clamp application, restricting instrument maneuverability, and critically increasing renal vein kinking risk.¹ While preoperative imaging metrics like psoas muscle index provide anatomical context, our experience confirms that visual assessment of psoas overhang and iliac depth offers more practical intraoperative guidance. The absence of correlation between psoas measure-ments and outcomes² underscores that technical adaptation, rather than anatomical measurement alone, determines success.

The complete absence of venous thrombosis in our series, despite selection of patients specifically for high-risk anatomy, demonstrated the technique’s protective effect against this devastating complication. Renal vein thrombosis remains a significant concern, affecting 2% to 12% of transplants and typically manifesting within the first postoperative months.^3,4 By creation of a protected channel that eliminates mechanical com-pression and kinking, the psoas groove addresses a fundamental thrombotic mecha-nism that anticoagu-lation alone cannot prevent.⁵

Our data demonstrated compelling technical efficiency, with mean venous anastomosis time of 12 ± 4 minutes and mean cold ischemia time of 25 ± 6 minutes. These metrics are particularly relevant in deceased donor transplant, where prolonged ischemia directly affects delayed graft function and long-term survival.^6-8 The technique’s value lies in its targeted approach, whereas alternative strategies like minimally invasive approaches^9,10 or coupling devices¹¹ offer general benefits. An artery-first sequencing^1,12,13 reduces graft manipulation, and the psoas groove specifically resolves the mechanical conflict between the renal vein and prominent psoas muscle.

Intraperitoneal placement provides another solution for difficult cases, although intraperitoneal placement violates the peritoneal cavity and risks intra-abdominal complications. Similarly, the inverted kidney technique described by Simforoosh and colleagues¹⁴ offers an elegant solution for short right renal veins. The psoas groove technique complements rather than replaces these approaches. The technique maintains the standard extraperitoneal field while directly addressing psoas-related compression. In fact, for cases with combined challenges, groove creation could potentially be combined with inverted place-ment for optimal venous alignment.

Technical execution requires meticulous attention to safety. Groove creation must remain anteromedial and superficial to avoid the lumbar plexus,¹⁵ with hemostasis achieved through precise point coagu-lation. The groove should be just deep enough to recess the vein without tethering, typically measu-ring approximately 1 × 0.5 cm. Our standardized approach with limited electrocautery and with reassessment of venous alignment after reperfusion ensured consistent results without neurological complications or significant bleeding.

Strengths and limitations
The prospective design and standardized technique by a single surgeon strengthened the internal validity, and the well-defined anatomical criteria ensured appropriate case selection. However, the single-center experience and modest sample size limited generalizability, and the study was not powered to detect rare complications. One-year follow-up, although it can demonstrate excellent initial outcomes, cannot assess long-term graft function or potential late complications.

Future directions
Multicenter validation would strengthen evidence for broader adoption. Comparative studies versus other techniques for management of difficult anatomy would better define relative indications. As minimally invasive transplantation evolves,^9,10 investigation of the feasibility of groove creation in robotic or laparoscopic approaches could represent another promising direction.

Conclusions

The psoas groove technique represents a targeted solution to a specific mechanical problem in renal transplant. By providing a protected venous channel, this technique facilitates tension-free anastomosis, reduces ischemia times, and prevents kinking without adding morbidity. Its simplicity, reproducibility, and compatibility with standard techniques make it a valuable addition to the transplant surgeon’s arma-mentarium for management of challenging iliac anatomy.

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