Low-level laser therapy (LLLT) has been employed to alleviate pain resulting from chronic non-infectious inflammation in muscles and joints. One of the challenges of LLLT is that a consistent understanding of mechanism of action remains elusive. The spinal dorsal horn, a key site where noxious signals are densely conveyed, offers a significant point of study for understanding the analgesic mechanism of LLLT. However, there’s a dearth of reports assessing LLLT’s effects on this region. In our study, the effect of laser irradiation on the sciatic nerve and the resultant firing of superficial neurons in the spinal dorsal horn—triggered by mechanical skin stimulation—was investigated using in vivo extracellular recording. To monitor the firing from individual neurons, electrodes were positioned in the superficial layer of the rat spinal dorsal horn. Mechanical stimulation, facilitated by von Frey filaments (vFF) ranging from 0.6 g to 26.0 g, was applied to the skin receptive field governed by the sciatic nerve, both pre and post laser exposure. The vFF-evoked neuronal firing in the superficial spinal dorsal horn was then recorded and analyzed. We examined two methods of laser application: direct irradiation onto the exposed sciatic nerve through a skin incision and percutaneous irradiation without making any incision. Our findings indicate that direct laser exposure to the sciatic nerve significantly inhibited the 26.0 g vFF-evoked firing frequency post-irradiation, with effects persisting for 3 hours. In an analysis 15 minutes post-irradiation, both 15.0 g and 26.0 g vFF-evoked firing frequencies were selectively inhibited. Sham irradiation showed no changes in firing frequency. A similar trend was observed with percutaneous laser irradiation. The firing frequency ratios between pre and 15 minutes post-irradiation remained consistent between the direct and percutaneous irradiation methods. When a photodiode sensor was implanted near the sciatic nerve, followed by percutaneous laser application, the power density reaching the nerve decreased to approximately 10% of the set irradiation parameters. Moreover, histopathological evaluations revealed no observable damage to the sciatic nerve due to direct laser exposure. Given that the 15.0 g and 26.0 g vFF are thought to correspond to noxious (painful) stimuli, our results suggest that laser irradiation selectively inhibits neuronal firing triggered by pain. This hints at the inhibition of neural activities in either or both Aδ and C fibers. Our findings suggest LLLT might not only be suitable for treating inflammation-induced pain (currently an insurable condition) but also for conditions where Aδ and C fibers play a pivotal role in the pathophysiological mechanism.

Three patients who presented with a chief complaint of Fordyce spots of the lips were treated with carbon dioxide laser (CO2RE^® Syneron Candela, Inc.). Irradiation was performed with consideration of the anatomical location of the lesion based on histological studies. One patient had a partial postoperative recurrence, but two patients have had no recurrence to date with no scar formation. Although Fordyce spots represent a normal collection of free sebaceous glands and have no pathological significance, individuals often desire treatment for cosmetic reasons. Fordyce spots can be treated in a minimally invasive manner with carbon dioxide laser in a short term since they are located in a relatively shallow area of the dermis and wounds in the mucosa, which is a preferentially affected site, heal very quickly.

Photodynamic diagnosis and treatment technologies have emerged recently. In December 2017, oral 5-aminolevulinic acid hydrochloride was approved for intraoperative navigation of tumors during transurethral resection of bladder tumor in Japan. Here, we have been working on the development of porphyrin metabolic pathway-based fluorescent urine cytology as a less invasive test compared with routine cystoscopy for post-treatment surveillance for urothelial carcinoma.

For upper urinary tract urothelial carcinoma (UTUC), the European Association of Urology and the National Comprehensive Cancer Network guidelines have recommended ureteroscopic surgery (URS) for cases with low-risk tumors (low-grade biopsy and cytology, <1.5–2 cm, unifocal, no invasion on imaging), and cases with bilateral tumors, a solitary kidney, or severe renal dysfunction. However, the 2-year recurrence rate after surgery is remarkably high, leading to the need for salvage radical nephroureterectomy. Furthermore, unlike robotic or laparoscopic surgery, the surgical procedure for URS has not been standardized due to the technical specificity of laser devices and ureteroscopes. Therefore, this procedure is performed only in limited facilities with extensive experience internationally. In this review, we introduce the current issues of URS for UTUC and the use of the photodynamic diagnosis-guided URS procedure, which we are implementing to overcome these challenges.

Current development of laser technology and flexible ureteroscope under urolithiasis treatment have dramatically been prompted to go toward less-invasive procedures. Of all, Holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy has already been gold standard. In addition, “Moses technology” with pulse modulation had invented and contributed to improve the clinical efficacy. Furthermore, novel laser named Thulium fiber laser whose wavelength is different from Ho:YAG laser has introduced and already applied in clinical field. These new technology are going to make a lot of roles for urolithiasis management.

For upper urothelial carcinoma (UTUC), minimally invasive treatment with laser ablation combined with ureteropyeloscope (URS) for small, solitary, low-grade, low-risk UTUC of less than 1 cm results in kidney-sparing treatment have recently been reported to be relatively good. An additional advantage of URS is the possibility of histopathological diagnosis prior to treatment. At our institution, we are working on laser resection with vaporization (LRV) as organ preservation not only for low-risk tumors. We investigated the association between biopsy pathology and recurrence in 37 patients (30 males and 7 females) who underwent LRV. Regarding lymphovascular invasion (LVI), 35 cases (94.6%) were negative. A multivariate analysis of the grade, invasion mode, LVI, coexisting carcinoma in situ (CIS) lesions, and biopsy pT stage that could be determined by biopsy pathology revealed that INF and LVI were independent predictors of recurrence. Although further investigation is necessary due to the limited number of cases, it was suggested that strict follow-up is required for cases found to be LVI-positive or infiltrative growth patterns by biopsy pathology.

5-aminolevulinic acid (ALA)-Photodynamic diagnosis (PDD) using ALAGLIO^® (ALA hydrochloride, SBI Pharmaceuticals Co., Ltd., Tokyo, Japan) had been approved for the management of non-muscle invasive bladder cancer (NMIBC) in Japan and has been available to the public health insurance system since 2017. ALA-PDD improved diagnostic accuracy and therapeutic effect. And ALA-induced hypotension may be observed as a side effect and need to respond.