Varicocele (VAC) is the most common cause of male infertility that can be surgically corrected, with a prevalence of approximately 15% in adult males and approximately 35% of patients with primary male infertility having VAC, while in patients with secondary infertility this percentage can be as high as 70% to 81% [1,2]. Surgery is the main method of treatment for VAC. The main traditional surgical approaches are retroperitoneal cluster ligation of the spermatic vessels (Palomo procedure) and transinguinal high level ligation of the internal spermatic veins. In recent years, with the increasing maturity of laparoscopic techniques, laparoscopic high ligation of the internal spermatic vein has become increasingly common. However, both traditional surgery and laparoscopic surgery cannot effectively separate and protect the testicular artery and spermatic lymphatic vessels, and even ligate the testicular artery and lymphatic vessels together; in addition, because of the large number of branches of the internal spermatic vein and the large variation, traditional surgery and laparoscopic surgery often ligate incompletely and miss the branches of the vein. This results in increased complications such as postoperative testicular atrophy, syringomyelia and VAC recurrence rate. The effectiveness of traditional surgery for VAC with male infertility has also been questioned. Some analyses have shown that conventional open surgery and radiological interventions do not ultimately improve the conception rate of spouses of patients with VAC with infertility [3]. In order to effectively protect the testicular arteries and spermatic lymphatics and reduce postoperative recurrence, Goldstein et al [4] first reported the application of microsurgical techniques for the treatment of VAC in 1992, and since then, the advantages of microsurgery for VAC with good results, low recurrence rate and few complications have been reported in the literature; microsurgery for VAC with infertility can significantly improve semen quality and increase the conception rate. In this paper, we review the progress in this area. The microscopic anatomical features of the spermatic cord in VAC patients The spermatic cord contains arteries, veins, lymphatic vessels, nerves and vas deferens that enter and exit the testes and epididymis, as well as the external spermatic vein that drains the levator muscle and the draining vein that drains the testicular sheath, both of which are also associated with the recurrence of varicocele The microscopic anatomical features of the spermatic cord in VAC patients vary greatly according to the level of the spermatic cord. 1.1 Microanatomy of the spermatic cord at the level of the subepidididymal ring Hopps et al [5] found that at the level of the subepidymal ring, the leading veins could be seen in 60% to 70% of VAC patients, with an average of 0.4 veins of 2 mm diameter; the average number of external spermatic veins was 5.4, of which the average number of veins of 5 mm diameter (large veins) was only 0.05 (visible in only 5% of patients); the average number of internal spermatic veins was 11.1, of which the average number of small veins was 7.9. The number of intra-seminal veins >2 mm in diameter increased with the increase of the VAC grade; 25% of the patients had a single testicular artery at the level of the external ring, 42% had 2, and only 33% had more than 3. 55% of the VAC patients had more than 1 external seminal artery, and 95% of the testicular arteries were surrounded by small veins ( The lymphatic vessels could be seen in the spermatic cord in 94% of VAC patients, with an average of 3.2 vessels. 1.2 Microanatomy of the spermatic cord at the level of the inguinal canal Beck et al [6] found that at the level of the inguinal canal, the average number of internal spermatic veins was 8.7, with an average of 4.7 small veins, 2.2 medium veins and 1.9 large veins; the number of large veins was significantly greater (1.9 vs 0.4) and the number of small veins was significantly less (4.7 vs 7.9) than at the level of the inferior external ring, with the small veins generally converging into the The small veins generally converged to the nearest larger vein; external spermatic veins >2 mm in diameter were seen in 74% of patients; the leading vein was seen in 79% of patients; the single testicular artery was seen in 69% of patients, significantly higher than at the subcircular level (69% vs 25%, P< 0.03); the testicular artery was located posterior to the larger internal spermatic vein in 50% of patients, and was surrounded by a network of small veins in 30% of patients, significantly lower than at the subcircular level (30 P3mm), then they also need to be ligated [7]. The vas deferens usually has two sets of veins accompanying it, and as long as one set is left intact, the reflux needs can be met. During the procedure, the testis may or may not be pulled out of the incision; microscopic magnification varies from 6 to 25 times. 2.1 Selection of the incision MV is often performed by taking an inferior external ring incision, by finding the external ring opening on the lateral side of the pubic tuberosity near the scrotal root, inserting the external ring opening with the index finger, then marking the body surface, taking a 2-3 cm transverse incision 1 cm below the external ring opening, separating the superficial fascia superiorly and inferiorly and then freeing the spermatic cord and presenting it outside the incision. However, according to the results of Hopps et al [5], there are many fine branches of the internal spermatic vein and testicular artery branches under the external ring, and a high percentage of testicular arteries are encircled by fine accompanying veins, which increases the difficulty of the procedure. Therefore, taking an inguinal incision for MV is easier to perform and is suitable for beginners; patients with VAC in isolated testes and prepubertal VAC should also take an inguinal incision because the testicular artery is easily identified via the inguinal route. However, if the patient has undergone VAC surgery before, an infra-epigastric incision needs to be chosen. In addition, if the patient is obese, has a wide and flaccid external ring orifice with a high position, a long spermatic cord and a low testicular position, the procedure can be easily performed by taking the subcircular incision. orhan et al [8] showed that there was no significant difference between the two incisions in terms of improved semen quality, increased pregnancy rate and operative time (all p > 0.05). 2.2 Comparison of intraoperative testes raised out of the incision or not Goldstein et al [4] initially applied microsurgery for VAC with the method of raising the testes out of the incision in order to identify the leading vein. More recently, Ramasamy et al [9] compared two methods of MV with and without raising the testis via the inguinal route and showed that there was no significant difference between the two methods in terms of improving pregnancy rates and no recurrence of VAC after surgery; semen quality improved in patients with grade II and grade III VAC after MV without raising the testis, whereas MV with raising the testis improved semen quality only in patients with grade III VAC; and semen quality improved after surgery without raising the testis. The testosterone level of MV without testes increased from 11.19 nmol/mL to 16.32 nmol/mL before surgery, while the testosterone level of MV with testes did not differ significantly before and after surgery. It is suggested that MV without raising the testis is superior to the method of pulling the testis out of the incision. It may be related to the increased damage to the testis by raising the testis into the incision. 2.3 Intraoperative identification of testicular artery and intra-seminomatous lymphatics The search for protection of testicular artery and intra-seminomatous lymphatics is a key step in MV and is an advantage of MV over conventional and laparoscopic surgical approaches. To identify the testicular artery, 1% poppy base or lidocaine can be added intraoperatively to the surface of the spermatic cord in drops to dilate the artery and help identify it. Intraoperative identification of the arteries can be made easier with the help of a fine-needle Doppler probe. However, the pulsation of the artery is the main basis for arterial identification. For smaller arteries, identification is difficult if spasm occurs intraoperatively. In this case, the fine network of accompanying veins surrounding the artery must be carefully separated to detect the arterial pulsation. The testicular artery can also be identified by temporary blockage, where the tip of the micro-needle holder is used to pick up the suspected vessel and slowly lower it, and if it pulsates, it is an artery. If the testicular artery still cannot be identified, the spermatic cord can be dissected starting with the thickest diameter vein, and the testicular artery can usually be found posterior to the vein. In approximately 50% of cases, the testicular artery is located posterior to the larger vein [6]. It was found [10] that testicular volume is related to the diameter of the testicular artery. The larger the testicular volume, the thicker the testicular artery and the easier it is to identify, and conversely, the smaller the testicular volume, the thinner the artery and the increased chance of intraoperative misligation. Lymphatic vessels are difficult to identify microscopically because of their transparency, and Schwentner et al [11] helped to identify lymphatic vessels by subcutaneous injection of 1% isoxsuprine (a lipophilic live dye) into the scrotum 15 min before surgery. However, Makari et al [12] showed that intra-testicular injection of live dyes such as isosulfan blue in rats can lead to thickening of the basal membrane of the germinal tubules, interstitial fibrosis and edema in the testis, and even necrosis of the germinal tubules, and caution is recommended for dye injection. Adjusting the microscope magnification to high magnification (10×) can also help in the identification of lymphatic vessels. 3.Comparison between MV and non-microsurgical VAC surgery Non-microsurgical VAC surgery cannot effectively protect testicular arteries and lymphatic vessels, and the high proportion of venous ligation makes postoperative testicular atrophy, testicular syringomyelia and other complications and VAC recurrence increase. Al-Kandari et al [13] compared the results of MV with several non-microsurgical VAC repair procedures and showed that no testicular syringomyelia occurred after MV, whereas the incidence of testicular syringomyelia after open inguinal surgery and laparoscopic surgery was 13% and 20%, respectively. Among 40 patients, only 1 (0.25%) recurred after MV, while 7 (17.5%) and 9 (22.5%) recurred after open inguinal surgery and laparoscopic surgery, respectively; 76% of patients had improved semen quality after MV, and the pregnancy rate was 40%, while 65% and 67% had improved semen quality after open inguinal surgery and laparoscopic surgery, respectively. The pregnancy rates were 28% and 30% for open inguinal surgery and laparoscopic surgery, respectively, both of which were lower than those for MV, which is considered to be the ideal procedure for the treatment of VAC at present. Compared with non-microsurgical procedures, the advantages of MV are mainly reflected in the following aspects. (1) Effective protection of the lymphatic vessels The lymphatic vessels draining the head and body of the testis and epididymis are accompanied by the spermatic vessels, while the lymphatic vessels draining the caudal part of the epididymis and vas deferens are accompanied by the vas deferens vessels, and there is no collateral drainage on the way back to the inguinal lymph nodes. Injury to the lymphatics can cause testicular syringomyelia, but also testicular enlargement (due to interstitial edema), damage to the germinal tubules, and reduced endocrine function of the testis [14]. Therefore, preservation of the lymphatic vessels is of great importance. However, the incidence of postoperative testicular syringomyelia is 6% to 39% in non-microsurgical procedures due to failure to protect the lymphatic vessels, whereas the incidence of testicular syringomyelia is almost zero in MV due to effective protection of the lymphatic vessels [15]. (ii) Effective protection of testicular artery Previously, it was believed that ligation of testicular artery would not lead to testicular atrophy because testicular blood supply could be compensated by lateral circulation such as levator artery and vas deferens artery. Therefore, traditional VAC repair surgery and laparoscopic surgery often ligated the testicular artery together with the spermatic vein to reduce postoperative VAC recurrence. However, reports have shown that the incidence of testicular atrophy after injury to the testicular artery can be as high as 14% [16]. Although testicular artery injury sometimes does not result in testicular atrophy, it can impair the spermatogenic process, and protection of the testicular artery plays an important role in maintaining normal spermatogenic function [17]. In view of this, the American Urological Association (AUA) recommends that VAC surgery requires maximum preservation of the testicular artery with the aid of a microscope or magnification [18]. It is even more important to protect the testicular artery in patients with isolated testes and pediatric or adolescent VAC. chan et al [19] reported 2102 patients with VAC treated with MV, 19 cases (0.9%) of testicular artery misligation occurred, and only one of these patients developed testicular atrophy. ③ The recurrence rate of VAC after surgery was greatly reduced The recurrence rate of VAC after MV surgery was only 0%-2%, while the non-microsurgical procedure was as high as 9%-16% [15]. 4. Effectiveness of MV for male infertility To evaluate the surgical effect of MV on VAC with male infertility, Marmar et al [20] observed the semen quality and pregnancy rate of spouses before and after surgery in 466 patients with VAC infertility, and the results showed that sperm density, viability, and percent normal sperm increased by 10.8×106/mL, 13.9%, and 3.8%, respectively, after surgery compared with those before surgery