A new percutaneous nephrolithotomy position in horseshoe kidney: 45 degrees sided prone.

INTRODUCTION: In this study we aimed to determine the effects of the 45 degrees sided prone position to the surgeon's comfort, operation time, fluoroscopy time and complications at the operation of percutaneous nephrolithotomy (PCNL) for the treatment of kidney stone of horseshoe kidney (HK) or rotation anomaly kidney.
MATERIAL AND METHODS: Thirty eight patients (25 male, 13 female) with renal calculi and HK, underwent PCNL. After the amplatz sheath was inserted into the collecting system, the patients in group 1 (n:20) were taken to the 45 degrees side position to the side of the operation and patients in group 2 (n:18) were operated in classical prone position. Operative data of two groups were compared statistically.
RESULTS: Mean stone size of group 1 was 557.8 ±244.8 mm3 (188-1175) and group 2 was 590.7 ±172.8 mm3 (423-909) (p = 0.639). In group 1 mean operation time was 78.6 ±21.8 (45-120) minutes and in group 2 was 95.05 ±11.5 (69-120) minutes. The difference for operation time was statistically significant and shorter in the sided group (p = 0.02).
CONCLUSIONS: The working position of rigid nephroscope is 90 degrees to the body after the dorsomedial or dorsolateral access. In our study the position of patient is laterally sided 45 degree and the flexion on the surgeon's shoulder was minimised. This new position described for PCNL in HK allows comfortable working position for surgeon after upper pole posterior calyces access. Copyright by Polish Urological Association.

INTRODUCTION

One of the most common renal fusion anomalies is horseshoe kidney (HK) with an incidence of 0.25% [1]. The anatomical position of the pelvis and calyces and the high insertion of the ureter in comparison with a normal kidney cause more prevalence of complications in HK [2]. HK is thought to be associated with an increased incidence of stone disease. The prevalence of urolithiasis in HK has been reported to be 20–60% [3, 4].

Percutaneous nephrolithotomy (PCNL) is the most widely used method in HK patients who have failed other therapies and is the treatment of choice for stones larger than 20 mm [5, 6]. Many various safe and effective changes in patient positioning for PCNL have been proposed over the years, including a reverse lithotomy position [7], prone split-leg position [8], lateral decubitus position [9,10], supine position [11], and Galdakao-modified supine Valdivia (GMSV) position [12].

An ideal patient position would provide good anesthetic conditions and ergonomics with minimal intraoperative complications [13]. In HK, the needle access is generally made to the upper posterior calyces because of the rotation of the kidney. The working angle of the nephroscope to the patient is 90 degrees. This working angle complicates the handling of the instruments for the surgeon. We sided the patient’s position 45 degrees to the surgeon’s side and saw that the use of instruments was easier than in the prone position. In this study we aimed to determine the effects of the 45 degrees sided prone position to the surgeon’s comfort, operation time, fluoroscopy time and complications of the operation of PCNL for the treatment of kidney stones within HK or rotational anomaly kidney.

MATERIAL AND METHODS

Thirty-eight patients (25 male, 13 female) with renal calculi and HK were enrolled in this prospective study. Patients underwent a PCNL procedure which was performed by two surgeons between September 2014 and January 2020. All patients were evaluated with a detailed medical history and physical examination, complete blood count, serum biochemistry, urinalysis, urine culture, and coagulation tests. Each patient underwent a comprehensive preoperative and postoperative radiologic assessment, including plain abdominal radiography, non-contrast and contrast computed tomography (CT). Estimated stone size was calculated by using Ackermann’s formula (volume = 0.6 x π x r2) (r is the half of largest diameter of the stone) and recorded in the data.

An open-ended 5 F ureteral catheter (MarflowTM, Marflow AG, Switzerland) was placed in the ureter and was guided by cystoscopy with the patient in the lithotomy position under general anesthesia. After placement, the patient was moved to the prone position. The anatomy of the pelvicalyceal system was visualized with radio-opaque material that was instilled using the ureteral catheter under C-arm fluoroscopy. A 19.5-gauge percutaneous needle (Percutaneous Access Needle, Boston Scientific Corporation, MA, USA) was introduced into the posterior upper calyx system upright in the body. Fluoroscopy was used to place a guidewire (ZebraTM Nitinol Guidewire, Boston Scientific Corporation, MA, USA) in the collecting system for access. The tract was dilated up to 30 F with semi-rigid amplatz dilators (Boston Scientific Microvasive Amplatz TractmasterTM, Boston Scientific Corporation, MA, USA) and an Amplatz sheath was inserted into the collecting system (Figure 1).

Figure 1

Percutaneous nephrolithotomy in classical prone position.

Patients were divided into 2 groups. Twenty patients were operated in the sided prone position and 18 patients were operated in the prone position. The randomization of the patients was made by a surgical nurse. The nurse decided in which position the operation will be performed on the day of operation. In the sided prone group, the patient was taken to the 45 degrees sided position to the side of the operator (Figure 2). After the patient was placed in the prone position, the patient was tied to the operation table at the hips, legs and shoulders to avoid possible slips and falls. Then, the patients were placed in a side position. Stone fragmentation was performed using a pneumatic lithotripter (CalculithTM Lithotripter, PCK, Turkey) through a 28 F rigid nephroscope (Karl StorzTM Endoscopy-America Inc.) in both groups. Stone fragments were collected by using forceps and the operations were ended after placement of a 14 F re-entry nephrostomy catheter.

Figure 2

Percutaneous nephrolithotomy in sided prone position.

Residual stone situation, operation time, fluoroscopy time and complications were recorded in the data. Residual stone situation was evaluated with low dose computed tomography in the postoperative first month. The patients with no residual fragments were assessed as stone free [14]. Complications were graded according to the Clavien-Dindo classification system which includes 5 grades [15]. Grade 1 and 2 complications require no surgical and radiological interventions. Blood transfusion and total parenteral nutrition were classified as grade 2 complications and grade 3 complication requires surgical or radiological intervention.

Visual Analog Scale (VAS) is a method for measuring pain intensity dimensionally. VAS is a 10 centimeter (100 mm) line and the patient is asked to place a mark on the VAS line at the point which defines their pain degree. VAS score of the surgeon’s shoulder, arm and back pain was recorded at 15, 30, 60, 90 minutes after the entry of nephroscope to the kidney. Additionally, in operations longer than 90 minutes one more VAS score was recorded at the end of the operation.

Statistical analysis

Statistical evaluation was completed using the Statistical Package For Social Sciences program version 18 (SPSS Inc). Quantitative measurements are summarized as the mean and standard deviation (the median and the minimum-maximum where necessary). For the comparison of quantitative measurements between the operation groups, Student’s T Tests were used when appropriate; Mann-Whitney U tests were used if the assumptions for Student’s T Tests were violated. Results were assessed at a 95% confidence interval, and p <0.05 was accepted as statistically significant.

RESULTS

There were 38 patients (25 male, 13 female) included to the study. Group 1 patients were operated on in the sided prone position and group 2 patients were in the prone position. Mean age of group 1 was 39.5 10.2 years and group 2 was 39.8 ±9.9 years (p = 0.712). Mean stone size of group 1 was 557.8 ±244.8 mm3 (188–1175) and group 2 was 590.7 ±172.8 mm3 (423–909). There were no statistically significant differences between the groups for stone burden (p = 0.639). In group 1 mean operation time was 78.6 ±21.8 (45–120) minutes and in group 2 was 95.05 ±11.5 (69–120) minutes. The difference for operation time was statistically significant and shorter in the sided group (p = 0.02) (Table 1).

Table 1

Characteristics of patients and operative data

	Group 1	Group 2	P
Patient number (n)	20	18
Mean age (year)	39.5 ±10.2	39.8 ±9.9	0.712
Male / Female (n)	12 / 8	13 / 5	0.573
Mean stone size (mm3)	557.8 ±244.8 (188–1175)	590.7 ±172.8 (423–909)	0.639
Operating time (min)	78.6 ±21.8 (45–120) (76)	95.05 ±11.5 (69–120) (95)	0.002
Fluoroscopy time (min)	7.25 ±2.5 (7)	7 ±1.6 (7)	0.724
Stone free rate	75%	61.1%	0.216
Nephrostomy removal (day)	2.9 ±0.7 (2–4)	2.8 ±0.7 (2–4)	0.785
Transfusion rate	5%	16%	0.125

Four patients required blood transfusion (Clavien grade 2) and 1 of these patients was in group 1 and 3 of them were in group 2. None of the patients had fever and lung or bowel complications after surgery. There was no complication due to the positioning of the patients from prone to the sided prone position. In all patients, the urethral foley catheter was removed on the first postoperative day.

DISCUSSION

PCNL is classically performed in the prone position, with well-documented safety and efficacy. The supine position, conversely, has anesthetic advantages, but results in poorer ergonomics and increased surgical difficulty [15, 16]. While previous original articles provided no rationale for the prone approach it nevertheless became the standard for the procedure. In this study a 45 degree sided prone position has advantages for the easy approach and good ergonomics for the surgeon.

In patients with a HK, upper pole percutaneous access is often recommended, because upper pole access allows access to the upper pole calices, renal pelvis, lower pole calices, pelviureteral junction, and proximal ureter [17, 18]. After the dorsomedial or dorsolateral access, the working position of the rigid nephroscope is 90 degrees to the body. In the normal positioned kidneys after lower pole access, the surgeon’s forearm angle is flexion of the elbow without any shoulder angulation.

The dorsomedial or dorsolateral access to the kidney makes the position of nephroscope right angled to the patient’s body. Because of the rotation of the kidney in the HK the surgeon’s position is flexion of shoulder to maintain the vertical position of nephroscope. In the HK with high stone burden, the operation time will increase and the surgeon’s arm and shoulder can get tired because of the vertical working position. This difficulty is only in handling the nephroscope. Additionally after the insertion of forceps or lithotriptor, the arm will rise up and the wrist will turn down to control the forceps. It is difficult to maintain the arm and wrist in this position. This fatigue can increase the complication rate. In our study the position of the patient is laterally sided at 45 degrees and the flexion on the surgeon’s shoulder was minimised. Surgeons’ arm, shoulder or back pain was questioned after surgery. VAS score of the surgeons at 15, 30 and 45 minutes into the operations were not different between the groups. But there were a statistically significant difference between the groups for surgeons’ VAS score at 60, 90 and later minutes. Surgeons’ VAS scores were lower in the sided prone group (Table 2). Working in the laterally sided position mimics the lower pole access in a normal kidney and maintains the surgeon’s comfort.

Table 2

Surgeons’ mean VAS score

VAS score	Group 1	Group 2	P
15 min	0.15	0.55	0.764
30 min	0.5	2.05	0.634
45 min	1.15	2.94	0.258
60 min	1.62	3.5	<0.005
90 min	1.85	4.3	<0.005
End of operation	2	5.08	<0.005

VAS – Visual Analog Scale

In the literature, ultimately stone-free rates following PCNL in the HK were reported to be within the range of 72–91% [19, 20, 21]. In our data stone-free rate was 81.2% and consistent with the literature. There was no significant difference between the groups for stone-free rates.

Although there are publications in the literature reporting selective embolization due to postoperative bleeding because of the fact that the vessels of the horseshoe kidneys enter the anteromedial hilus and the calyces are oriented towards the posterior, the risk of vessel injury is no higher than in normal kidneys [17, 22]. In the literature transfusion rates were reported as 0–13.3% [23, 24]. In our study a decrease in hemoglobin was seen in 7 patients but only 4 patient required a transfusion. In patients with HK anomalies, adjacent organ injury in PCNL is a risk. El-Nahas et al. have reported colon perforation rates in PCNL with HK as 5.9% [24]. Shokeir et al. reported only one colon perforation in their 34 PCNL patients with horseshoe kidney and the patient had retrorenal colon [21]. Some investigators recommend a preoperative CT evaluation in horseshoe kidney patients [25]. None of the patients we operated with the technique described had any adjacent organ injury but it is not an advantage of this position as we dilate the kidney in the prone position and after the dilation we transfer the patient to the side position.

The operating time with our technique was also evaluated in our study. A recent systematic review by Falahatkar et al. [26] found that the mean operating time of prone and supine PCNL was 99 min and 81 min, respectively. This is comparable with the mean operating time in our own study, which was 78.6 min in group 1 and 95 min in group 2. We found a significant difference between the study groups for operating time. We explained this difference with the easier use of instruments and not getting tired early in group 1.

Proietti et al. stated that the renal sheath angle parallel to the ground is one of the advantages of the supine position. The advantage of this angle to the prone position has been reported as a decrease in intrarenal pressure and spillage of fragments [27]. Since the angle of the sheath, which is 90 degrees to the ground in horseshoe kidney, will be parallel to the ground in the position we have defined, it may contribute to the reduction in intra-renal pressure. Another disadvantage of the upright sheath is the risk of ‘bumping into the nephroscope’ or ‘displacing the nephroscope’ which may occur more frequently in the classical prone position. In the sided prone position this risk decreases.

In a multicentre study of Vicentini et al., it has been stated that horseshoe PCNL can be safely applied in the supine position, as well as the prone position [28]. There are advantages in supine PCNL such as not having to reposition the patient, easy access to the intubation tube, covering the patient only once, and a short operative time. Since the sheath is in the downward position in the supine PCNL, intrarenal fluid pressure and pyelovenous return of the contaminated fluid may be less. However, the nephroscope control and the use of forceps can be ergonomically difficult in the sheath standing downward. In our position the working comfort of the surgeon is superior.

CONCLUIONS

This study shows that our PCNL position is feasible, efficacious, and safe. This new position described for PCNL in HK allows for a comfortable working position for the surgeon after upper pole posterior calyces access. According to our series, the described technique for PCNL in HK should be an option. Nevertheless these results must be confirmed by further studies.