The tactics of removing kidney and ureteropelvic junction stones are currently quite widely and particularly described in modern guidelines. Determination of one or another treatment way depends on the kidney stone features and localization, the patient`s constitutional peculiarities, and concomitant diseases ― remote kidney stone crushing, laparoscopic operations, retrograde or percutaneous lithotripsy. Endoscopic instruments have been significantly improved over the past 15 years. Therefore, it became possible to remove complex kidney stones of the kidney and the upper third of the ureter effectively. However, it is not possible to achieve a good result through a monomethod in all the cases. Special difficulties arise when it is impossible to visualize the stone retrogradely, to bring the lithotriptor probe due to mucosal edema, anatomical features, with “penetrated” stones, and concretion migration during crushing. The percutaneous method is often problematic to be used for kidney stones of elongated narrow necks of the calyx, postoperative scarring of the kidneys, and skeletal deformities. In this regard, it is necessary to look for new ways that may allow removing “problem” kidney stones through integrating accesses.

Fernstrom and Johansson were the first who performed percutaneous nephrolithotripsy in 1976 [1]. Therefore, serious drastic changes in approaches to the surgical treatment of kidney stones have taken place since the introduction of this method. Percutaneous nephrolithotripsy was performed in the prone position until 1987; Valdivia described the original technique performed in 585 patients in the supine position [2]. Carrying out the surgery in the prone and supine position is comparable for the reasons of safety. At the same time, the supine position has some advantages: direct access to the respiratory tract with endotracheal anesthesia and the possibility of simultaneous retrograde access. Also, there is no need to make the patient change the supine position (after installing a renal catheter) to the prone one. The options for accessing the upper calyx are optimal and safer if the patient remains in the prone position, and the implementation of multiple accesses is more profitable in this case [3][4][5][6].

In most cases, treatment of kidney and ureteropelvic junction stones is carried out by retrograde or percutaneous access and using rigid instruments. In many cases, access to some areas of the pelvicalyceal system is only possible with the help of flexible tools. It is especially necessary for coralloid forms of nephrolithiasis ― fragmentation, spur extractions, kidney stones, and fragments of the upper third of the ureter, also in patients with kidney abnormalities and complex bony frame deformities [7][8].

Therefore, pneumatic, electrohydraulic, ultrasonic, and laser energies are widely used to influence the fragmentation of kidney stones [9][10][11][12][13]. Pneumatic and ultrasonic lithotriptors are the safest for the surrounding tissues. When the stone is crushed, the fragments are evacuated simultaneously ― that is the advantage of the ultrasonic lithotripter. At the same time, when the pneumatic lithotripter is crushed by the probe, fragments are formed; they are to be removed later, which also takes extra time spent for the surgery. The advantage of electrohydraulic and laser lithotriptors is their use with a flexible tool and the possibility of harder kidney stone fragmentation. Anyway, the significant damaging effect of the electrohydraulic method did not allow it to be widely implemented in practice.

The electro-pulse type of kidney stone fragmentation by retrograde access is described quite fully in the works of Gudkov, but the use of this lithotripsy type by the percutaneous method (particularly in combination with retrograde lithotripsy) has not been previously covered in the scientific literature [14].

The results of percutaneous and retrograde crushing of stones in kidneys and the upper third of the ureter have been quite actively discussed in recent years. Bozkurt et al. described eighty-six patients who underwent percutaneous nephrolitholapaxy (forty-five patients) and retrograde stone crushing (forty-one patients) of the upper third of the ureter in a 2015 study. The result was complete removal of the kidney stone in the first group ― 97.6%, and 82.3% of all the cases in the second one. In the second group, the kidney stone could not be visualized in three patients retrogradely due to edema, and in several patients, the kidney stone migrated to the kidney. Therefore, the hospital stay in the percutaneous nephrolitholapaxy group was longer than in the retrograde access group. Studies have confirmed that percutaneous nephrolithotripsy is a safe and effective procedure, as well as retrograde surgery, which is indicated for patients with kidney stones in the upper third of the ureter [15][16][17][18].

An effective method for treating stones in the ureteropelvic junction and the upper third of the ureter is a simultaneous combination of percutaneous and retrograde approaches in the Valdivia position. In his work, Chen performed simultaneous percutaneous nephrolithotripsy and retrograde contact lithotripsy for thirty-one patients. At the same time, the effectiveness of kidney stone removal after three months was 100%, the average age of patients was 57 years, the kidney stone size was 20.1 mm (15.0 – 37.9 mm range), the surgery time was 81 minutes (30 – 150 minutes range), and the postoperative hospital stay was 3.2 days [19]. Similar work was carried out by Huang in thirteen patients with kidney stones of the upper third of the ureter (about 15 mm size), which confirms the effectiveness of a combination of these approaches [18]. The integration of accesses is a promising scientific area and a very topical issue that is being actively discussed at the moment. The study aimed to evaluate the effectiveness and safety of removing kidney and ureteropelvic junction stones by a simultaneous combination of approaches ― retrograde and percutaneous lithotripsy through using electric pulse energy.

26 patients underwent combined percutaneous and retrograde contact electric impulse lithotripsy during the period from 2014 to 2019 (Table 1).

Table 1. Summary patients’ demographics describing the study group

Patients’ demographics Number (n = 26) Sex (male/female) n = 8 / 18 Average age, year 53 ± 16.9 (25 ‒ 76) Kidney stone size, length in mm 19.5 ± 13.1 (5 ‒ 51) Stone density, HU 1229 ± 245.36 (510 ‒ 1720)

Inclusion criteria. This method of treatment was chosen in cases where, due to anatomical features, it was not possible to remove the concretion percutaneously or retrogradely through a monomethod. This combination was used mainly in patients with kidney stones of the ureteropelvic junction, penetrated kidney stones of the upper third of the ureter, kidney stones of the upper calyx with narrow elongated necks and an acute angle of access. Such an angle does not allow the percutaneous fragmentation of kidney stones (Fig. 1). Such combinative method is also used in patients with previously performed open interventions of the urinary tract, in patients having a scar deformity that led to changes in normal anatomy, and in patients with severe bone frame deformity that complicates the retrograde access to the kidney stone.

The percutaneous access played the main role during the combined removal of kidney stones due to the possibility of disintegration and evacuation of fragments of a larger size than the retrograde one. The retrograde access was auxiliary, it was used for kidney stone fragmentation and bringing it down. It was also necessary for erecting kidney stone fragments to the Amplatz tube in the case of non-possibility to achieve the result by antegrade access (Table 3).

Table 3. Summary outcome of surgery treatment

Surgery duration, min 131 ± 55.8 (40 ‒ 280) Post-surgery hospital stay, days 6.3 ± 1.77 (3 ‒ 17) Post-surgery kidney stone-free status, n (%) 26 (100%) Complications: bleeding requiring transfusion or conversion, n (%) 0 (0%) post-surgery fever > 38.0, n (%) 1 (3.84%) kidney stone’s migration, n (%) 2 (7.7%) re-intervention demand, n (%) 2 (7.7%)

Intraoperative and postoperative results are presented in Table 3. The average duration of surgical interventions was 131 minutes (40 ‒ 280 minutes range). The concretions of twenty-four patients were completely removed during one intervention, in two patients with multiple kidney stones, the surgery was performed in two stages or more. The effectiveness of this method was 92.3%, with repeated interventions, the result was achieved in 100% of cases.

23 interventions were performed without any complications, and one patient developed acute pyelonephritis in the postoperative period, which was stopped with antibiotic therapy. The migration of fragments during crushing was observed in two patients during the surgery. No significant bleeding was observed during the surgery and post-surgery treatment, no blood transfusion was required, no damage to adjacent organs was noted.

This study demonstrated that the combination of accesses to kidney and ureteropelvic junction stones is justified for kidney stones of various sizes, their prolonged standing or penetrating. The effectiveness of this technique does not depend on the kidney stone size. The risks associated with antegrade access are justified as well. This type of surgery intervention is very effective for multiple kidney stones, regardless of the location in the kidney.

The simultaneous use of percutaneous and retrograde methods has the advantage of achieving excellent results during one surgical intervention.

This approach to the treatment of kidney and ureteropelvic junction kidney stones allows creating an open system to safely crush the stone, without fear of reflux when the pressure of the irrigation fluid in the cavity system increases. The ureteropelvic junction kidney stone can be moved back into the renal pelvis, and the kidney stone or fragments of the upper calyx, on the contrary, can be brought down and removed through the Amplatz tube during one procedure. Also, one can always examine the ureter for the presence of residual kidney stone fragments or blood clots at the end of the surgery while removing the ureteroscope.

The combination of antegrade and retrograde approaches with using electro-pulse energy for ureteropelvic junction kidney stones and complex kidney stones is an effective treatment method. The simultaneous combined access to the kidney stone in some cases is the only possible one, when remote lithotripsy is contraindicated. It should be also used when the risk of open surgery is quite high and endoscopic methods in the form of monodetection are antegradely or retrogradely not effective.