Anatomical four-plane retroperitoneal laparoscopic adrenalectomy for selected unilateral adrenal tumors smaller than 6 cm: technical description and in-hospital outcomes from a single-center retrospective case series

Technical Summary: Anatomical Four-Plane Retroperitoneal Laparoscopic Adrenalectomy

Problem Statement
Retroperitoneal laparoscopic adrenalectomy (RLA) offers direct access to the adrenal gland without mobilizing intraperitoneal organs. However, the procedure is often hindered by a confined working space, adherent perinephric fat, and the potential loss of anatomical orientation if the peritoneum is breached. These factors can obscure the adrenal margins and the renal upper pole, leading to repeated tissue manipulation and an unstable dissection sequence. While previous anatomical approaches (such as the three-plane technique) have improved reproducibility, challenges remain in clearly defining the interface between the adrenal base and the upper renal pole, particularly in patients with significant perinephric fat.

Methodology
This study presents a single-center, retrospective case series of 102 patients who underwent an anatomical four-plane RLA for unilateral adrenal tumors smaller than 6 cm at Kaifeng Central Hospital between January 2018 and December 2024.

The core of the methodology is a standardized, sequential dissection strategy utilizing the renal capsule and renal fascia as landmarks. After opening the lateroconal fascia, the surgeons developed four relatively avascular surgical interfaces:

1. First Plane (Renal Capsular Plane): A vertical incision through the anterior renal fascia and perinephric fat at the lateral border of the mid-kidney. Dissection proceeds medially and cranially along the interface between the renal capsule and perinephric fat to expose the anterior surface of the upper renal pole.
2. Second Plane (Anterior Adrenal Surface): The upper-pole perinephric fat is opened obliquely in a cranial direction to identify the peritoneum. Dissection then advances medially, cranially, and deeply through the interface between the perinephric fat and the anterior renal fascia to expose the anterior surface of the adrenal gland.
3. Third Plane (Posterior Adrenal Surface): Dissection occurs between the superolateral perinephric fat and the posterior renal fascia, exposing the diaphragm's lumbar fascial surface. The plane is developed medially, cranially, and caudally to expose the posterior surface of the adrenal gland.
4. Fourth Plane (Renal Surface of the Adrenal Gland): This plane is the study's specific addition. Near the diaphragm, the superolateral fat over the upper renal pole is incised inferomedially. Dissection follows the interface between the upper-pole renal parenchyma and the fat at the adrenal base, terminating at the anteromedial margin of the upper renal pole to expose the renal surface of the adrenal gland.

Once all four planes are established, gravity and retroperitoneal insufflation displace the kidney and elevate the perinephric fat, creating a clear working space for the isolation, clipping, and division of the adrenal pedicle.

Key Contributions

• Standardized Sequence: The paper describes a reproducible, four-step dissection sequence that uses the renal capsule as a primary reference to systematically expose the anterior, posterior, and renal surfaces of the adrenal gland.
• Fourth Plane Definition: It explicitly defines the "fourth plane" as an extension of the established three-plane concept, specifically targeting the often-obscured interface between the adrenal base and the upper renal pole.
• Technical Feasibility Data: The study provides a detailed technical description and a comprehensive dataset of in-hospital outcomes for this specific technique in a selected cohort.

Results

• Completion: All 102 procedures were completed laparoscopically (100%; 95% CI, 96.4–100) with no conversion to open surgery.
• Safety: There were no major visceral or vascular injuries (0%).
• Adverse Events: Six intraoperative adverse events occurred: two peritoneal breaches (managed with an auxiliary trocar) and four superficial renal capsule lacerations (managed with bipolar coagulation). Eight patients experienced mild postoperative subcutaneous emphysema (Clavien–Dindo grade I), which resolved spontaneously. No grade II or higher complications were recorded.
• Efficiency: The mean operative time was 48.3 ± 6.5 minutes, and mean estimated blood loss was 10.8 ± 5.4 mL.
• Recovery: The median time to oral intake was 12 hours, and the median postoperative hospital stay was 4 days.
• Follow-up: Among 97 patients with available follow-up (median 24 months), no recurrence was documented. Functional outcomes for primary aldosteronism and cortisol-producing adenomas were consistent with expected clinical recovery.

Significance and Claims
The authors assert that the anatomical four-plane technique is technically feasible and demonstrates a favorable in-hospital safety profile in the hands of an experienced surgical team. The approach successfully achieved complete laparoscopic exposure and adrenalectomy without open conversion in a cohort of patients with tumors up to 6 cm.

However, the paper maintains a modest stance regarding its broader implications. The authors explicitly state that:

• The findings do not establish superiority over conventional RLA or the three-plane technique, as the study lacked a control group.
• The results are uncontrolled and descriptive; they cannot prove that the four-plane sequence reduces operative time, blood loss, or complication rates compared to other methods.
• The "fourth plane" is a surgically defined interface based on intraoperative landmarks, not a histologically validated fascial space.
• Future prospective comparative studies are required to define optimal indications, the learning curve, and the reproducibility of the technique across different surgeons and institutions.