Clinical application of PCNL in oblique supine lithotomy position for upper urinary calculi

In 1976, when Fernstrom and Johansson successfully removed kidney stones through percutaneous renal channels for the fi rst time, PCNL gradually became the gold standard for the treatment of kidney stones ≥2cm in diameter [1]. The oblique supine lithotomy position was introduced by Ibarluzea In 2007 [2], compared with the traditional prone position, which confi rmed with higher stone removal rate [3-5]. The purpose of this study is to compare the treatment effect of prone position and oblique supine lithotomy position in the treatment of upper urinary tract stones with PCNL by retrospective study. Related studies are helpful to evaluate the advantages of oblique supine lithotomy position in the application of PCNL. Our hospital has performed PCNL for oblique lithotripsy for upper urinary calculi since 2016, and has achieved good results. It is reported as follows.


Introduction
In 1976, when Fernstrom and Johansson successfully removed kidney stones through percutaneous renal channels for the fi rst time, PCNL gradually became the gold standard for the treatment of kidney stones ≥2cm in diameter [1]. The oblique supine lithotomy position was introduced by Ibarluzea In 2007 [2], compared with the traditional prone position, which confi rmed with higher stone removal rate [3][4][5]. The purpose of this study is to compare the treatment effect of prone position and oblique supine lithotomy position in the treatment of upper urinary tract stones with PCNL by retrospective study. Related studies are helpful to evaluate the advantages of oblique supine lithotomy position in the application of PCNL. Our hospital has performed PCNL for oblique lithotripsy for upper urinary calculi since 2016, and has achieved good results. It is reported as follows.

Operative procedure
All patients underwent PCNL surgery, which was performed by the same surgical team led by the same surgeon, and also by the same urology specialist surgical nurses and anesthesiologists.

Prone position PCNL
After general anesthesia, the lithotomy position was taken, and a zebra safety guide wire was placed under the cystoscope. An F6 ureteral catheter was placed along the guide wire. Select the 11th intercostal space or the 12th lower costal space, between the posterior axillary line and the scapular line, and perfuse normal saline with a 50ml syringe retrogradely through an F6 ureteral catheter, resulting in "artifi cial hydronephrosis". Under the guidance of B-ultrasound, the 18G renal puncture needle punctured the renal calyceal dome precisely, and the clear liquid outfl ow indicated that the puncture was successful (a lot of blood liquid indicated that the puncture failed, and a second puncture was needed). The "J" guide wire was placed into the renal collection system through the needle sheath, and the fascial expander was gradually expanded to F20, and the working sheath was retained. Nephroscope was entered into the renal collecting system through the channel to look for stones. After smashing the stones with holmium laser, the stones were fl ushed out through the perfusion fl uid, and the larger stones were taken out in the stone basket. F4.8 double J tube and F16 nephrostomy tube were routinely indwelling Figure 1.

Oblique supine lithotomy position PCNL
The lower torso of the supine position is turned to the opposite side, the body is turned into a healthy side by the waist cushion, the back is close to the edge of the bed, the shoulders are fi xed with shoulder rests, and the cushions are placed behind the hips. Tilt back 45 ° to the operating table 3L washing liquid was placed on the abdomen to reduce the lateral displacement of the patient. The lumbar bridge was adjusted to make the waist show a folding knife position. The puncture area of the patient side was exposed. The patient side lower limb fl exed knee adduction was slightly abducted and fi xed on the foot rest. The healthy side lower limb fl exed knee was placed on the horizontal plate of the abduction. The chest and abdomen were in oblique supine lithotomy position, while the lower limbs and buttocks were in rotation 90° lithotomy position. Under the guidance of color ultrasound, puncture was performed in the posterior line of 12 subcostal axilla, the puncture Angle was 12°~25° from the ventral Angle perpendicular to the skin, the puncture target was located in the middle or lower calyces of the affected kidney, and the renal puncture channel was established in the same prone position. F4.8 double J tube and F16 nephrostomy tube were routinely indwelling.

Intraoperative pressure monitoring of the renal pelvis
By placing the pressure sensor (Pressure Sensor (Beijing Jishiba Medical Devices Co., Ltd. ICU Medical Model 42584-05)) in the renal pelvis along the puncture sheath through the extension tube, it is fi xed in the plane of the renal pelvis. After the calibration and adjustment, the invasive blood pressure measurement channel connected to the ECG monitor (Shanghai Hanfei Medical Devices Co., Ltd. Delgde State BSM3500) is connected. Data collection software was used to input the intraoperative data into the database in real time, and then SPSS was used for retrospective statistics to calculate the intraoperative mean renal pelvic pressure.
During the operation, two ureteroscopy combined with ureterolithiasis retrograde ureteroscopy: COOK F16 ureteroscopy dilatation sheath was placed along the guide wire, and Olympus ureteroscopy was placed for lithotripsy; anterograde ureteroscopy: ureteroscopy was used to look for residual stones in the upper ureter from the calyx through the renal puncture

General information
In terms of average age, the prone position group was 49.6  (Table 1 for details).

Intraoperative and postoperative data
There was no signifi cant difference between the two groups  (Table 2 for details).

Renal pelvis pressure
The RPP transient ≥30mmHg occurred in two groups were 152 and 32 cases, and ≥40mmHg were 115 cases and 28 cases, respectively. In both groups, the RPP was ≥30mmHg during the operation, and the total time was> 5min. There were 135 and 22 cases, respectively. There were 109 cases and 17 cases with total time> 5min ( Table 3 for details).

Renal pelvis hypertension and Postoperative day1 PCT (procalcitonin) change
Considering intraoperative renal pelvis hypertension alone, there was no statistically signifi cant difference in postoperative day1 PCT changes between patients in the high pressure group (RPP>30mmHg or>40mmHg Group) and the low pressure group (RPP>30mmHg Group, P>0.05, RPP>40mmHg Group, P>0.05). ; When the total duration of intraoperative renal pelvis hypertension (≥30mmHg) ≥5min, the postoperative day1 PCT was signifi cantly higher than that of patients with sepsis. Moreover, in vitro study showed that the pressure of renal pelvis above 30mmhg (3.99kpa) for more than 50s would signifi cantly increase the postoperative fever rate [10]. In this study, the intraoperative renal pelvis hypertension the total time was less than 5min; Only when the intraoperative renal pelvis hypertension with total time is more than 5min, the difference of postoperative fever between the two groups is   Citation: Zhou  At the same time, the early control of intraoperative perfusion through the syringe has great randomness and uncertainty. Excessive perfusion fl ow will cause renal pelvis hypertension and bacterial refl ux such as the circulatory system [9,15], resulting in urinary sepsis and renal impairment [16]. Or the intraoperative perfusion pressure can be adjusted by adjusting the height of 3L bag of perfusion fl uid. Although the stability of intraoperative perfusion pressure is ensured to some extent, there is still a lack of specifi c quantitative indicators, and the effect fl uctuates greatly before and after.
In this study, the perfusion pump was used to precisely control the low-pressure perfusion water fl ow, to ensure the stability of the pressure of the renal pelvis during the operation, and to minimize the transient high pressure of the renal pelvis during the operation.Meanwhile, low intraoperative RPP should also be considered, that is, insuffi cient perfusion leads to unclear intraoperative visual fi eld and lack of compression effect leads to increased intraoperative blood loss. In this study, the RPP at the oblique avulsion position was lower than that in the traditional prone position.

Intraoperative percutaneous nephroscope combined with ureteroscope in special cases
Studies have shown that the single stone removal rate for staghorn stones treated with PCNL is only 56% [17].
Multistage PCNL is associated with an increased risk of related complications [18,19].    supine lithotomy position is at the level of low-pressure perfusion, and the incidence of complications above grade II is only (10/ 80, 12.5%), which refl ects the safety of oblique supine lithotomy position from the side. With the rise of ultra-micro percutaneous nephroscope (SMP) in recent years, the narrower endoscopic sheath will lead to the increase of the pressure of the renal pelvis during the operation. In combination with the characteristics of low pressure of the renal pelvis in this position, it can better refl ect the advantages of oblique supine lithotomy position.

Defi ciencies
The sample size in this study is small; Since the incisivepuncture channel under the oblique anaposyte is far away, it is necessary to grasp the vascular area of the kidney more accurately in the process of establishing the channel. Realtime three-dimensional color ultrasound during the operation is needed to improve the vascular identifi cation rate and thus reduce the probability of intraoperative bleeding. At the same time, the puncture channel is longer, and the scope of the lens swing is limited during operation. A small amplitude of the lens swing may cause the puncture point to deviate from the predetermined target. In addition, compared with the prone position of abdominal cushions and compression of abdominal organs, kidney mobility in the oblique supine lithotomy position is greater than that of the prone position, which makes it diffi cult to accurately locate the entire puncture, and it requires more accumulation of puncture experience, extending the learning curve. Real-time color Doppler ultrasound tracking is needed to clarify the differences in renal activity during different positions to guide the establishment of percutaneous channels during the operation.

Conclusion
Oblique supine lithotomy position can reduce the pressure of renal pelvis during operation and improve the rate of postoperative stone removal (SFR). For special cases, especially the complicated upper urinary calculi of renal calculi with ureteral calculi, it can realize the combination of double mirror (percutaneous nephroscope + ureteroscope) lithotripsy, signifi cantly reduce the operation time, thus, reduce the amount of blood loss during operation and reduce the incidence of postoperative complications.

Ethical standard
Ethical and regulatory approvals were sought and obtained from the Second Affi liated Hospital of Nantong University, China.