What's known on the subject? and What does the study add?
Use of balloon dilatation leads to less blood transfusion rates than metallic dilators. Plasma vaporization leads to less blood loss than balloon dilatation in this study.
The study evaluates a novel technique for the creation of a nephrostomy tract for PCNL. Compared with other techniques, plasma vaporization is a safer procedure that causes lesser blood loss, requires a shorter hospital stay, causes less radiation exposure, and enables easier nephrostomy tract creation for PCNL.
To evaluate the efficacy and safety of plasma vaporization for tract creation in percutaneous nephrolithotomy (PCNL).
Patients and Methods
In this randomized prospective trial we enrolled 65 patients and assigned each to one of two groups: 33 patients were randomly scheduled to undergo plasma vaporization and 32 were scheduled to undergo balloon dilatation for tract creation.
A bipolar resectoscope mounted with a plasma vaporization button electrode or a traditional balloon dilator were used to create the nephrostomy tract.
The mean blood loss, mean length of hospital stay and mean operating time, stone-free rates and postoperative complications in the two groups were compared using the t-test or chi-squared test (Fisher's exact test).
The plasma vaporization group had a significantly lower mean (SD) decrease in haematocrit level (3.5 [2.8]% vs 6.6 [3.3]%; P = 0.02) and a shorter mean (SD) hospital stay (2.6 [1.2] days vs 5.3 [3.4] days; P = 0.0).
There were no significant differences in the operating time, stone-free rate or cases of postoperative fever between the two groups.
The plasma vaporization technique is safe, leads to less blood loss than the other techniques, and is a simple solution for creating the nephrostomy tract for PCNL.
The creation of a nephrostomy tract is one of the most important and also most expensive procedures in percutaneous nephrolithotomy (PCNL). Compared with metal dilatation, the use of balloon dilatation reduces blood transfusion rates; however, the use of balloon dilators often results in haemorrhage, perforations in the collecting ducts, radiation hazards, or even operation failure [1-3].
A vaporization technique that uses a spherical plasma vaporization button electrode (TURis-PVP system; Olympus, Tokyo, Japan) for the treatment of BPH was recently introduced; this technique resulted in superior efficacy and lower complication rates than previous techniques . In the present study, we aimed to evaluate the efficacy, safety and results of this new method for nephrostomy tract creation and to compare these findings with those obtained by standard balloon dilatation.
Materials and Methods
The study was approved by our institutional review board. Patients were enrolled between May 2010 and September 2011, and were randomly assigned to one of two groups: 33 patients were randomly scheduled to undergo plasma vaporization, and 32 were scheduled to undergo balloon dilatation for tract creation.
The patients were placed in the prone position, and an 18-gauge Chiba needle was inserted into the appropriate renal calyx using ultrasonography and occasional fluoroscopic guidance to make contact with the stone. After removal of the stylet, a floppy-tipped guidewire was passed through the needle and into the collecting system. The skin over the puncture site was then incised. In the control group, a balloon dilator (UltraxxTM; Cook Medical Inc., Bloomington, IN, USA) was inserted to dilate the nephrostomy tract using the standard procedure. In the experimental group, the wound was dilated using a haemostat and a 28-F Amplatz sheath was inserted into the s.c. area. A bipolar resectoscope (TURis-PVP system; Olympus) mounted with a plasma vaporization button electrode powered by the Olympus UES-40 generator (Olympus) was introduced into the Amplatz sheath. Continuous flow irrigation using saline was performed. The spherical part of the electrode displayed a plasma corona, and the electrode was gradually moved using a hovering technique, along the guidewire and in direct contact with the s.c. tissues, fascia, muscle and renal parenchyma, thereby enabling a virtually bloodless vaporization at 250–300 W (Fig. 1A). A large quantity of vapour bubbles was noted during the vaporization. The Amplatz sheath was advanced along with the resectoscope once the tract had been created by vaporization. When large vessels were encountered during vaporization of the renal parenchyma, coagulation could be achieved by reducing the power of the generator to 150 W (i.e. by switching vaporization mode to coagulation mode [Fig. 1B]). Vaporization was stopped when the electrode and Amplatz sheath reached the calyx or renal pelvis (Fig. 1C). The guidewire was removed through the Amplatz sheath. A 28-F Karl Storz nephroscope and Swiss Lithoclast® Master (EMS, Nyon, Switzerland) were used to disintegrate the renal stone. After stone fragmentation, a JJ stent was routinely placed using the antegrade or retrograde approach after completion of the procedure. Three to four pieces of absorbable haemostatic gelatin sponge (Spongostan; Ethicon, Somerville, NJ, USA) were inserted into the tract through the Amplatz sheath. The wound was sutured without introducing a nephrostomy tube. All procedures were performed by the same surgeon (C.P.H.). The success rate was defined as entrance of the 28F Amplatz sheath into the targeted collecting system, and the patient was recommended reasonable follow-up when the largest residual fragment was <7 mm in diameter. The JJ stent was removed 1 month after the operation. At the same time, plain abdominal film of kidney, ureter and bladder was used to measure the diameter of residual stone fragments.
Parametric data were compared using the t-test, and categorical data were compared using the chi-squared test (Fisher's exact test). SPSS version 17 (IBM Corp., Somers, NY, USA) was used to perform the calculations.
The patients included in this prospective, randomized study had similar baseline characteristics with regard to age, gender, body mass index, American Society of Anesthesiologists (ASA) score, stone type, and stone diameter (Table 1).
Table 1. Demographic data and stone characteristics
No. of patients
Mean (sd) age
Mean (sd) body mass index
Mean (sd) ASA score
Stone type, n (%)
Neither of the above
Mean (sd) stone size, largest diameter; mm
By applying the plasma vaporization technique, we achieved a success rate of 100% for entry into the targeted collecting system. In the 33 patients who received plasma vaporization, the mean (SD) haemoglobin levels before and 24 h after the PCNL procedure were 13.5 (1.5) g/dL and 12.2 (1.5) g/dL, respectively, and the corresponding haematocrit values were 40.3 (3.7)% and 36.1 (4.2)%, respectively. By contrast, in the 32 patients who underwent balloon dilatation performed by the same surgeon, the mean (SD) haemoglobin levels before and after PCNL were 14.1 (1.7) g/dL and 11.8 (1.5) g/dL, respectively, and the corresponding haematocrit values were 42.2 (1.2)% and 35.3 (4.1)%. The plasma vaporization group was found to have a significantly lower drop in haematocrit levels (3.5 [2.8]% vs 6.6 [3.3]%; P = 0.02) and a shorter hospital stay (2.6 [1.2] days vs 5.3 [3.4] days; P = 0.0) (Table 2). There were no significant differences between the groups in the operating time and the rate of residual fragments <7 mm. In the 33 patients who received plasma vaporization, the mean (SD) estimated GFR (eGFR) levels before and 24 h after the PCNL procedure were 86.4 (45.1) and 78.2 (41.7) mL/min/1.73 m2, respectively. In the 32 patients who underwent balloon dilatation, the eGFR levels before and 24 h after the PCNL procedure were 74.3 (28.2) and 77.8 (29.6) mL/min/1.73 m2, respectively. There was no significant difference in change in eGFR after the operation between the two groups.
Table 2. Surgical outcomes
Mean (sd) 24-h postoperative haemoglobin drop, g/dL
Mean (sd) 24 h postoperative haematocrit drop, %
Mean (sd) hospital stay, days
Mean (sd) operating time, min
Residual fragments <7 mm, %
Postoperative fever, n (%)
Mean (sd) 24-h postoperative eGFR change, mL/min/1.73 m2
None of the patients in either group needed blood transfusions or had major complications.
The key procedure for a successful PCNL is the creation of a nephrostomy tract. The traditional method of dilatation of the percutaneous access tract involves the use of a metal or balloon dilator. Blood loss is common during PCNL, can occur during or after the operation and frequently occurs as a result of parenchymal lacerations incurred during tract dilatation . Blood transfusion after PCNL has been reported in 5–25% of patients, with some cases even requiring angiographic intervention [5-8]. In one study, severe bleeding with symptoms and signs of shock and hypotension occurred in 3% of the patients . Tomaszewski et al.  reported a lower incidence of blood transfusion (1.3%) among patients undergoing PCNL using balloon dilatation rather than metal dilatation. In their series, the mean (SD) decrease in haematocrit levels was 6.1 (4.3)%. Their results are similar to those of the present study for the patients undergoing PCNL using balloon dilatation; however, although none of the patients in the present study required blood transfusion, the mean (SD) decrease in haematocrit levels was only 3.5 (2.8)% in the patients who underwent PCNL using plasma vaporization. Less bleeding during or after the operation reduces the risk of developing a retroperitoneal haematoma, thereby resulting in less gross haematuria and flank discomfort, which may be reflected in the shorter length of hospital stay. Under the health insurance system in Taiwan, patients are more reluctant to be discharged if they still suffer from haematuria and flank pain. The shorter hospital stay may result from the fact that good haemostasis can be obtained in the vaporization group.
Despite using a conventional monopolar resectocope mounted with a Collin's knife to dilate the nephrostomy tract, we encountered irregularities and tissue debris in the nephrostomy tract. Moreover, the risk of water intoxication and fluid absorption attributable to the use of water as an irrigation fluid restricted the use of this technique. The transurethral resection in saline system (TURis-PVP; Olympus) is characterized by the ability of the UES-40 bipolar electrosurgical generator to produce a plasma corona on the surface of the spherical electrode. This technique incorporates both the active and return electrodes. It permits tissue vaporization in a conductive saline medium and enables concomitant haemostasis. Furthermore, this type of vaporization does not alter the visual characteristics of the tissues, enabling the operator to differentiate the fascia, muscle, adipose tissue, renal parenchyma and calyx. In addition, the vaporization area contains a smooth tract without irregularities or tissue debris. The ‘mushroom'-like electrode, displaying a plasma corona on its surface, enables a virtually bloodless vaporization with practically concomitant coagulation, thus providing a very clear visual field. Although there was no significant difference in the rate of residual fragments <7 mm between the two groups, the suction tube connected to the Swiss Lithoclast Master® often had to be clamped to clear the visual field of the bleeding from the parenchyma in the balloon dilatation group; however, such bleeding seldom occurred in the plasma vaporization group. This advantage over balloon dilatation may be the reason for the trend for a shorter operating time in the plasma vaporization group.
Access to the pyelocaliceal system is routinely performed under fluoroscopic guidance. The dilator is difficult to enter into the pyelocaliceal system occasionally if the calyx or pelvis is fully occupied with stones. Access for PCNL guided by ultrasonography has been reported as an alternative to using fluoroscopic guidance, but the dilatation of the working channel using a dilator still needs to be performed under radiographic control . Although the radiation dose in a standard PCNL procedure is often within the safe limit, and the clinical value of this radiation dose is minimal, it is always best to ensure the lowest radiation exposure . Plasma vaporization eliminates the need for fluoroscopic guidance during the creation of a nephrostomy tract; in most cases of plasma vaporization in the present study, we only used fluoroscopy to check for the presence of residual stones and the position of the JJ stent.
Plasma vaporization is economical because the TURis-PVP system can also be used in the treatment of BPH, and the plasma button electrode is reusable. This system is more cost-effective than the disposable Ultraxx nephrostomy tract dilation sets that cost ∼US $ 250.00 in Taiwan. Moreover, the shorter hospital stay that results from the use of plasma vaporization electrode can compensate for its cost.
There was no change in eGFR after the operation in either of the two groups. Diathermy to the renal parenchyma, leading to more renal parenchymal and function loss with plasma vaporization than with balloon dilatation, seems unlikely.
A limitation of the present study was its small sample size. Nevertheless, it was a prospective randomized trial, and all the procedures were performed by a single surgeon using similar operating techniques and management strategies. The findings support the hypothesis that plasma vaporization for creation of a nephrostomy tract results in less bleeding, a shorter hospital stay and a rate of stone fragments <7 mm similar to those obtained using other techniques.
In conclusion, compared with other techniques, plasma vaporization is a safer procedure that causes less blood loss, results in a shorter hospital stay, requires less radiation exposure, and enables easier nephrostomy-tract creation for PCNL.