TT occurs frequently in infancy and adolescence, and is found in 3.8/100,000 males under the age of 18 [7]. More than 30% of cases have no choice but to undergo orchidectomy. After 18 h of onset, the chance of testicular preservation is less than 50%, and after 24 h or more, the rate of testicular atrophy is close to 70% [8].

In the treatment of TT, it is important to diagnose it as soon as possible and to perform emergent surgery. At surgery, a test incision is made in the scrotum and the color tone of the testis is observed. If no problem is observed with the color tone, the testis is detorsioned and orchidopexy is performed. Even if the torsion is released, the color of the testicle may be poor, and it is often difficult to decide whether to remove or preserve it. There is also a technique that if the testicular tunica albuginea or parenchyma is incised and bleeding occurs within 10 min, it is suggestive of testicular preservation. When preserved using this technique, testicular atrophy rates have been reported to still be 17–22% [9, 10]. The criteria for determining whether a testis can be preserved or not are not clearly defined.

In this case, we evaluated testicular perfusion by means of IICG. For several years, ICG has demonstrated its application and effectiveness in tissue perfusion evaluation in a wide range of surgical procedures. In colorectal surgery, intestinal blood flow is evaluated by IICG, and it is useful for reducing the risk of anastomotic leakages [3].

In pediatric surgery, ICG is often used for example, in the identification of metastatic lesions of hepatoblastoma [4], for ICG cholangiography of biliary atresia [5], and for ICG lymphography of lymphatic malformation [6]. ICG has also been used safely and effectively in infants and newborns.

Although there is one case report of using IICG in a 26-year-old man with testicular torsion [11], there have been no reports in pediatric cases. The patient was operated after 6 and a half hours from onset of symptoms, and performed an IICG which consists of intravenous injection of 7.5 mg ICG, and visualization of the fluorescence under NIR light. ICG signals appeared in 45 s, showing homogenous vascularization of the whole testis, then the testis was salvaged. They reported to start a prospective study for ICG use in the setting of acute TT surgery in adult.

In our pediatric case, the ICG signals appeared 45 s after the intravenous of ICG injection, and we decided to preserve the testis. There are no criteria of the ICG appearance time for evaluating the blood flow of TT. Kumagai et al. used ICG fluorescence imaging to assess perfusion of reconstructed gastric tubes during esophageal cancer surgery [12]. After the intravenous injection of ICG, they measured the time from contrast entry into the right gastroepiploic artery base to contrast entry into the left gastroepiploic artery terminal branch and the gastric tube tip. They reported that there was a strong possibility of necrosis in the gastric tube in patients that contrast time over 90 s. In cases of non-occlusive mesenteric ischemia (NOMI), they evaluated whether ICG signals appeared or not [13, 14]. Tonooka et al. verified significance of intestinal blood flow evaluation by ICG during intracorporeal anastomosis in laparoscopic colectomy. They judged that the blood flow was good, an ICG signals appeared within 30 min [15]. Considering these reports, it seems that the testis can be preserved if ICG signals appeared at least 90 s.

The dosage of ICG in children has not been determined. Fernández-Bautista intravenously administered 0.2 mg/kg of ICG to assess the blood flow of pediatric organs [16]. There are few reports using ICG for blood flow evaluation in children, therefore more examinations are necessary to create accurate criteria for use of ICG in children.

The standard operative approach for TT is scrotal approach. In our case, an inguinal incision method was selected to evaluate blood flow from the spermatic cord to the testis. The inguinal incision method requires two incisions, the inguinal region and the bottom of the scrotum. However, in the inguinal incision method, not only the testis, but also the blood flow of the spermatic cord can be observed, which may help to determine whether or not the testis is preserved.

IICG may be a useful tool in the treatment of TT when macroscopic evaluation of the affected testis remains questionable after detorsion. In pediatric TT, whether the testis can be preserved is a very important issue for future tolerability, and it is expected that IICG evaluation will improve the testicular preservation rate.