Preliminary Experience with a 3D Digital Fluorescence Microscope and Indocyanine Green Angiography in Subinguinal Varicocelectomy

Summary

This study explores the application of a three-dimensional (3D) digital microscopy platform combined with indocyanine green (ICG) angiography in subinguinal varicocelectomy, highlighting improvements in surgical precision, arterial preservation, and patient outcomes.

Abstract

This study reports the application and preliminary experience of a three-dimensional (3D) fluorescent digital external-viewing microscope platform using indocyanine green (ICG) fluorescence angiography in subinguinal varicocelectomy and explores its impact on surgical outcomes and postoperative recovery. Twenty-six microscope-assisted subinguinal varicocelectomy procedures were performed on 23 patients between September 1, 2024, and October 25, 2024, using this technology.

During each surgery, 3 mL of ICG dye was administered via peripheral intravenous injection for angiography. Under fluorescence mode, the arterial and venous structures were visualized; the arteries were marked and preserved, and the veins were ligated. All operations were completed successfully, with an average operative time of 52.65 ± 8.48 min per procedure. The mean time from ICG injection to arterial fluorescence was 45.88 ± 2.10 s, and the mean time to venous fluorescence was 81.61 ± 3.61 s. On average, 2.1 ± 0.84 arteries (range 1-4) were preserved per patient, and several capillary reticular arteries were observed in most patients' spermatic vessels.

The 3D fluorescent digital external microscope platform using ICG angiography demonstrates promising potential in subinguinal varicocelectomy. It may become a reliable adjunctive technique in microscope-assisted varicocelectomy, aiding surgeons in accurately identifying and locating arterial branches at all levels, thereby preventing arterial injury during surgery.

Introduction

Varicocele refers to the abnormal dilation, elongation, and tortuosity of the pampiniform venous plexus within the spermatic cord, which can cause discomfort and swelling in the ipsilateral scrotum and/or decreased semen quality. It is a common male reproductive system disorder with an incidence rate of 10%-15% and as high as 25.4% among men with abnormal semen quality^1,2. Varicocelectomy is an effective treatment for varicocele, and it mainly includes open surgery, laparoscopic surgery, and microsurgical procedures. The ideal surgical approach is to completely ligate the veins of the spermatic cord while effectively preserving the spermatic artery and lymphatic vessels^3,4. Microsurgical varicocelectomy is currently considered the most effective technique⁵. However, some arteries remain difficult to identify under the microscope, which may be due to their smaller diameter, surrounding tissue encapsulation, or weak pulse, making them challenging to detect under direct visualization⁶.

Indocyanine Green (ICG) is an emerging fluorescent tracer with unique fluorescence properties. When excited by light of a specific wavelength, it emits fluorescence, which can be used with high-precision fluorescence imaging technology to precisely identify target structures. ICG has applications in angiography, tumor localization, and lymph node mapping and tracking, and has been widely adopted in surgeries involving the breast, gastrointestinal tract, liver, gallbladder, and pancreas^{7, 8}. Several studies have reported the use of ICG in (robot-assisted) laparoscopic varicocelectomy and demonstrated its feasibility^9,10,11. However, there are few reports on the application of ICG in microsurgical varicocelectomy.

Based on the fluorescent imaging capabilities of ICG, which can effectively display the vascular system and better identify arteries, veins, and lymphatic vessels, our center has conducted microsurgical varicocelectomy under ICG fluorescence guidance. This study aims to provide a preliminary summary of our experiences with this approach.

Protocol

This study involves human subjects and has been approved by the Ethics Committee of the First Affiliated Hospital of Zhejiang Chinese Medical University (Approval Number: 2024-X-163). Written informed consent was obtained from all patients. Authorization was granted to use patients' surgical videos and data for presentation. This study strictly adheres to the Declaration of Helsinki and relevant ethical guidelines. All consumables and equipment used in the study are detailed in the Table of Materials.

1. Preparation for surgery

1. Patient screening
   1. Determine patient eligibility based on the following criteria.
      1. Apply these inclusion criteria: Patients diagnosed with oligoasthenospermia, or experiencing ipsilateral scrotal discomfort, or identified by physical examination.
         NOTE: All patients were diagnosed with varicocele by physical examination and ultrasonography.
      2. Apply these exclusion criteria: Patients with recurrent varicocele after previous surgery, a history of inguinal hernia repair, nutcracker syndrome, or scrotal swelling/pain due to testicular or prostate pathology or oligospermia caused by other known factors.
2. Preoperative testing
   1. Perform a preoperative iodine allergy test. Apply a small amount of iodine reagent to the patient's skin and observe for redness, itching, or other signs of an allergic reaction.
   2. Ensure all patients test negative for iodine allergy before proceeding to surgery preparation.
3. Surgical area preparation and anesthesia
   1. Clean the surgical area with soap to remove contaminants from the skin before the operation.
   2. Disinfect the surgical area using 5% Povidone-Iodine under sterile conditions until the skin is dry.
   3. Position the patient in a supine position and administer general anesthesia via intubation.

2. Surgical procedure

1. Exposure of the spermatic cord
   1. Make a 2.0-3.0 cm oblique incision approximately 1 cm lateral to the pubic tubercle.
   2. Perform layer-by-layer dissection through the skin, subcutaneous tissue, Camper's fascia, and Scarpa's fascia.
   3. Use tissue forceps to expose the spermatic cord, pull it out through the incision, and secure it with a rubber tube to prevent damage to surrounding tissues.
2. Microscopic dissection
   1. Under a microscope (Figure 1), dissect the external spermatic fascia and cremaster muscle to expose the internal spermatic structures.
      NOTE: Unlike conventional binocular microscopes requiring eye-to-hand coordination through oculars, the 3D digital external-viewing microscope allows the surgeon to operate while viewing a high-definition 3D screen, enhancing ergonomics and allowing the surgical team to share the same visual field.
   2. Identify and isolate the vas deferens and its accompanying vessels, securing them gently with a rubber band to avoid damage (Figure 2).
3. Fluorescence-guided dissection
   CAUTION: Indocyanine green is photosensitive; ensure it has been stored in a dark environment.
   1. Verify that the patient has no iodine allergy (check the iodine allergy test results) before injection. Inject 3 mL of ICG intravenously.
   2. Activate the fluorescence mode to observe the visualization of the internal spermatic artery and vein.
   3. Carefully dissect the internal spermatic artery using microsurgical instruments, avoiding injury to the surrounding lymphatic vessels (Figure 3).
      NOTE: If a pause in the procedure is necessary, it is recommended to do so after completing step 2.3 to ensure smooth blood and lymphatic flow during subsequent tissue repositioning.
4. Venous ligation
   1. Identify the internal spermatic vein under the microscope and perform double ligation using 4-0 silk sutures.
   2. Transect the vein with micro scissors, ensuring no bleeding at the cut ends.
   3. After venous ligation, inject another 3 mL of ICG intravenously to confirm that no venous structures are missed.
5. Tissue repositioning and wound closure
   1. Suture the external spermatic fascia and cremaster muscle with absorbable sutures.
   2. Perform layered subcutaneous closure of the incision, ensuring precise alignment without tension.

3. Postoperative observation

1. Inspect the surgical wound for signs of infection, exudation, or hematoma.
2. Monitor for postoperative complications such as scrotal edema, recurrence, or other discomforts.

4. Data collection and analysis

1. Data recording
   1. Record operative time, fluorescence visualization times, the number of preserved arteries, details of venous ligation, and the incidence of postoperative complications using standardized forms.
2. Statistical analysis
   1. Analyze the data
      1. Express continuous variables as mean ± SD (standard deviation).
      2. Use t-tests or nonparametric tests for intergroup comparisons.

Results

The patients' average age was 28.92 ± 9.24 years (range: 12-59 years), with 20 patients presenting with left-sided varicocele and 3 patients with bilateral varicocele. The mean spermatic vein diameter, measured via ultrasound, was 3.13 ± 0.80 mm. All surgeries were successfully completed, with the average surgical time being 52.65 ± 8.48 minutes (range: 40-67 min). After peripheral intravenous injection of ICG, the time from injection to arterial fluorescence visualization was 45.88 ± 2.10 s (range: 42-51 s), while the t...

Discussion

Although ICG is generally safe, rare allergic reactions and limitations in patients with renal impairment must be considered. All patients in this study were tested for iodine allergy prior to administration, and no adverse reactions were observed. After intravenous injection of ICG, most arteries and veins can be observed using a fluorescence surgical microscope. The different times of arterial and venous fluorescence allow for effective differentiation between arteries and veins, improving vascular visualization. When ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Digital Surgical Microscope	Aesculap Aeos	PV010-CN	The digital surgical microscope consists of a camera, robotic arm, trolley, and control screen, 3D monitor stand, 26’ full HD 3D monitor, keyboard, mirror head cover, options
Indocyanine Green for Injection	DANDONG YICHUANG PHARMACEUTICAL CO.,ITD	H20055881	Used for choroidal angiography to determine the location of choroidal disorders.
SPSS version 23.0			Data analysis