Traditional TURP for BPH still suffers from problems in terms of large intraoperative bleeding and transurethral resection syndrome (TURS), which is unique to TURP, while transurethral intravesical laser surgery is a targeted solution to these two major problems of TURP. Due to the good tissue coagulation effect of laser, it has excellent hemostasis during tissue cutting, which significantly reduces the risk of intraoperative bleeding. At the same time, due to the non-electrical conductivity of laser, electrolyte solution, i.e. saline, can be used as the intra-vesical flushing medium during surgery, which basically eliminates the risk of TURS. Therefore, although TURP is still considered the “gold standard” of BPH treatment, the rapid development of transurethral intravesical prostate laser surgery in the last 30 years is undoubtedly another milestone in the minimally invasive treatment of BPH after TURP.
Since the introduction of the world’s first ruby laser in 1960, the use of lasers in medicine has evolved rapidly.
The properties of lasers include.
① Narrow wavelength range and monochromatic nature.
(ii) High coherence and instantaneous enhancement of energy upon excitation.
(3) Small divergence angle and directionality.
The effects of laser light on tissue include: absorption, conduction, reflection, and scattering. The wavelength of the laser and the nature of the tissue determine the corresponding clinical effect.
In the history of transurethral intracavitary prostate laser surgery, the main types of lasers used for the treatment of BPH are: Nd:YAG laser (neodymium laser), Ho:YAG laser (holmium laser), KTP laser (green laser) and 2µm laser (thulium laser), the principle of action of the above four lasers is different and their excitation wavelengths are different. The laser has a unique tissue action, and the surgical results are different.
1, the principle and characteristics of various lasers used in prostate surgery
(1) Nd:YAG laser (neodymium laser)
Neodymium laser is a solid-state laser with wavelength of 1064nm, and its emitted light is invisible light. The above-mentioned characteristics of neodymium laser determine that its effect of surgical hemostasis in the treatment of BPH is exact, while the effect of tissue cutting and enucleation is not good.
In the early 1990s, the neodymium laser was used in BPH, the laser energy is transmitted through the fibers with 60-90 reflection angle at the tip, so the laser is lateralized, and when it is excited, the laser radiates energy to the lateral tissues in a non-contact form to cause coagulation necrosis in the deep tissues. This procedure is actually called neodymium laser ablation of the prostate. The use of a sapphire tip at the end of the fiber is a contact laser, while the use of a disc-shaped reflector is a non-contact laser. The main drawbacks of this procedure are: postoperative urethral obstruction due to necrotic tissue formation often requires a second operation to resolve; the majority of the tissue obtained after the procedure has undergone coagulative necrosis, thus reducing the pathological detection rate of incidental prostate cancer. Therefore, the neodymium laser has been replaced by other lasers with better performance in clinical practice.
(2) Ho:YAG laser (Holmium laser)
Ho:YAG laser (holmium laser) is a solid-state pulsed laser. Its principle is to excite holmium, a rare element attached to yttrium-aluminum garnet crystal, to produce a pulsed laser with a wavelength of 2100 nm, which is located in the near-infrared region of the spectrum, and the absorption coefficient of water at this wavelength is large, so holmium laser can be significantly absorbed by water. Since the tissue is mainly composed of water, the energy of holmium laser is absorbed by the surface, and the powerful energy released instantly and forms a high temperature, vaporizing the tissue to achieve tissue cutting and coagulation, and the energy is mainly absorbed by the superficial tissue, so the thermal damage depth is only 0.4 mm. therefore, holmium laser is especially suitable for precise tissue excision. At the same time, because the pulsed laser energy of holmium laser can form vaporized bubbles with small absorption coefficient, most of its energy acts on the distal bubble-water interface, which can form a vacuolation effect on the stone surface, and thus has a lithotripsy effect that other lasers do not have. Therefore, holmium laser is the only multi-purpose laser among the above four commonly used lasers that has the function of tissue removal and stone fragmentation.
(3) KTP laser (green laser)
The KTP laser is a pulsed laser with a wavelength of 532 nm (in the green region of the visible spectrum) produced when a Nd:YAG (neodymium laser) passes through a potassium titanium oxide carbonate (KTP) crystal, hence the name green laser. Its energy is preferentially absorbed by oxyhemoglobin, followed by water absorption, so it facilitates vascular coagulation and tissue vaporization, but the depth of thermal damage is 1 – 2 mm, also known as photo-selective prostate vaporization (PVP).
(4) 2µm laser (thulium laser)
Thulium laser wavelength 1.91µm, close to the peak energy absorption of water, mainly for water absorption, coagulation layer 0.5 – 2mm, thus producing effective tissue vaporization, cutting and coagulation, with pulsed or continuous emission mode, up to 140W power.
2. Types of transurethral laser prostate surgery and their clinical characteristics
(1) Transurethral homium laser enucleation of Prostate (HoLEP)
In 1998, Gill first reported transurethral holmium laser enucleation of the prostate. Based on the development of anatomical understanding of prostate surgery, HoLEP differs completely from the previous concept of transurethral prostate surgery by using fiber optics to remove, dissect, and push the entire lobe of hyperplastic prostate tissue from the prostate surgical envelope into the bladder cavity, and then using a special Morcellator to shred and aspirate large pieces of prostate tissue within the bladder. During the procedure, a high-power (i.e., 100-watt) holmium laser is used to remove the gland, with an energy of 90 (J) = output power of 2.0 (W) × pulse frequency of 45 (/S); to improve the coagulation and hemostasis effect, the energy can be adjusted to 30 (J) = output power of 1.5 (W) × pulse frequency of 20 (/S). The procedure can be graphically summarized as follows: the holmium laser fiber head that is similar to the operator’s index finger in suprapubic transcatheter prostate removal, hence the name of this procedure as transurethral holmium laser prostate enucleation.
The basic steps of the HoLEP procedure include.
(i) enucleation of the middle lobe: an incision is made deep into the surgical pericardium of the prostate at the bladder neck between points 5 and 7 and the seminal frenulum, a lateral incision is made proximal to the seminal frenulum, the points 5 and 7 are incised out to join the confluence, and the middle lobe is reverse enucleated along the level of the surgical pericardium and pushed into the bladder.
(ii) Removal of the lateral lobe: Using the correct level (i.e., the prostatic surgical pericardium) separated during the middle lobe removal, the lateral lobe of the prostate is cut laterally at the 5 and 7 o’clock incision on the side of the seminiferous tubercle and rotated outward and upward to meet at the 12 o’clock bladder neck, cut off, and push the lateral lobe into the bladder, and at the same time, the wound is thoroughly hemostatic with laser.
(3) Cutting and shredding and removal of tissue: A 5-mm working channel of the nephroscope is used to cut and shred the prostate tissue in pieces in the bladder with a Morcellator.
The peak energy produced by the Ho:YAG laser leads to vaporization of the tissue and precise and effective removal of the prostate tissue, which has the advantages of less bleeding, complete removal, and no TURS, etc. It is suitable for patients with various sizes and volumes of prostate enlargement, especially for patients with high-risk factors (e.g., advanced age, huge prostate, combined with cardiopulmonary and other important organ dysfunction, coagulation dysfunction or on anticoagulation therapy, severe anemia, etc.). Patients who are not suitable for TURP surgery, such as those who have a large prostate gland, combined with cardiopulmonary and other important organ failure, coagulation disorders or are on anticoagulation therapy, and severe anemia). In 2004, Du Chuanjun reported a controlled study of 337 BPH patients undergoing HoLEP (185 cases) and TURP (152 cases), and the results showed that 3 cases (1.6%) were transfused in the HoLEP group and 18 cases (11.8%) in the TURP group; 55.3% of the TURP group had hyponatremia and 5.3% had severe hyponatremia, while no hyponatremia occurred in the HoLEP group; the above indexes were significantly different between groups. There is a significant difference between the groups, which proves that surgical safety of HoLEP is better than that of TURP, and it is not difficult for urologists with skilled TURP experience to master HoLEP, and studies have shown that the learning curve can be completed in 20 cases of HoLEP with a skilled HoLEP instructor.
At present, during lobectomy, the main use of the mirror sheath is similar to the “index finger enucleation” pushing and peeling, and when the vascular distribution or level is not clear, the Holmium laser vaporization cutting can be used to minimize thermal damage, keep the interface flat and clear, and significantly improve the efficiency of enucleation.
The duration of indwelling catheterization after HoLEP is short, and the incidence of retrograde ejaculation after surgery is similar to that of other transurethral surgical approaches. The Qmax at 1 year postoperatively is better than TURP, and the reoperation rate at 5 years postoperatively is lower than TURP. recently, Gilling summarized the results of a long-term postoperative study with TURP controls showing that HoLEP has consistent long-term results with open surgery, with a stable perioperative safety in patients with large prostate volumes >80 g. Also, HoLEP is the only minimally invasive surgical approach suitable to cover prostate of all volume sizes Holmium laser is also the only minimally invasive surgical procedure that covers all sizes of prostate enlargement. Holmium laser is also the only procedure in transurethral surgery that has the ability to treat both stones and prostate at the same time. Therefore, HoLEP is the most likely procedure to replace TURP as the “gold standard” in minimally invasive prostate surgery treatment today and in the future.
(2) Transurethral homium laser resection of Prostate (HoLRP)
In 1995, Gill from New Zealand reported the first case of holmium laser resection of prostate (HoLRP), which achieved ideal coagulation and hemostasis, but due to the use of holmium laser vaporization and lateral fiber, the resection efficiency was significantly lower compared to conventional TURP, so the HoLRP technique did not receive wide attention and development, and was eventually replaced by transurethral holmium laser resection. Prostate enucleation (HoLEP) replaced it.
(3) Transurethral Laser Vaporization
In 1996, Mayo Clinic first used 38W KTP in combination with neodymium laser to perform green laser prostate vaporization (PVP), using a continuous laser beam emitted by a side-fiber to rapidly vaporize the prostate tissue, but when it reaches the peritoneum, the vaporization effect is weakened due to the small number of blood vessels and fibrous tissue in the peritoneum, forming a “channel The laser beam can be used to vaporize the prostate tissue rapidly, and when it reaches the pericardium, the vaporization effect is weakened due to the less vascularized fibrous tissue in the pericardium, forming a “channel” for surgical treatment. The advantage is that there is basically no technical difficulty for urologists who have some lumpectomy base. Short-term improvements in IPSS scores, urinary flow rates, and QOL indices are comparable to TURP. It can be an outpatient procedure, but the incidence of postoperative urinary retention requiring catheterization is higher than for TURP. long-term efficacy has yet to be further investigated. The main drawback is the inability to obtain pathological tissue after tissue vaporization.
(4) Transurethral thulium laser peeled prostatectomy
In China, the Xia operation class reported that a technique similar to HoLEP lobectomy is used, in which the three lobes are divided into multiple lobes and are removed separately. Due to the vaporization effect, the tissue formed is smaller and the tissue crusher can not be used. The literature reports the use of orange peeled prostate thulium laser vaporization resection, the recent surgical efficiency (resected prostate weight, postoperative IPSS score) is similar to TURP, while the postoperative hemoglobin and electrolyte levels are more stable than TURP, the long-term efficacy is to be supported by evidence-based.
(5) Transurethral laser coagulation
It was once a surgical method to treat neodymium laser BPH. The distance between the fiber tip and the prostate tissue is about 2 mm, and the energy density is sufficient to coagulate the tissue, but not to vaporize it. The coagulated tissue will eventually necrotize and fall off, thus reducing the obstruction. Advantages include its simplicity, risk of bleeding, and low water absorption rate. Using meta-analysis, the incidence of urinary retention and urinary tract irritation requiring catheterization after transurethral laser coagulation of the prostate was found to be 21% and 66%, respectively, significantly higher than the 5% and 15% rates for TURP. Therefore, it has been replaced by other laser procedures.