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Year : 2020  |  Volume : 31  |  Issue : 2  |  Page : 68-72

Tubeless mini-percutaneous nephrolithotomy for the treatment of renal and upper ureteral stones of ≥3 cm in diameter

1 Department of Urology, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi, Taiwan
2 Department of Urology, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi; Department of Health and Nutrition Biotechnology, Asian University, Taichung, Taiwan

Date of Submission23-Oct-2019
Date of Decision17-Dec-2019
Date of Acceptance31-Dec-2019
Date of Web Publication25-Apr-2020

Correspondence Address:
Yeong-Chin Jou
No. 539 Chung-Hsiao Road, Chiayi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/UROS.UROS_82_19

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Purpose: To assess the outcome and safety of tubeless mini-percutaneous nephrolithotomy (mini-PCNL) to treat patients with renal and upper ureteral stones ≥3 cm. Materials and Methods: Between March 2017 and September 2019, 82 patients who underwent tubeless mini-PCNL at our hospital were evaluated. The patients had renal and upper ureteral stones of a size ≥3 cm in maximal dimension. A 15-Fr operating nephroscope was used. The patients were placed in the prone position. The stones were fragmented using ballistic lithotripter. The outcome was determined immediately after operation through plain radiography of the kidneys, ureters, and bladder and sonography. Various patients and stones characteristics, including perioperative outcomes and complications were evaluated. SPSS version 16 (SPSS, Chicago, IL, USA) was used for data analysis. Results: The mean age of the patients was 57.9 ± 10.5 years, and their body mass index was 26.0 ± 3.8 kg/m[2]. The mean stone size was 50.3 ± 19 mm. The average operative time was 107.7 ± 41.8 min, and the stone-free rate (SFR) was 54%. The mean postoperative hospital stay was 3.5 ± 1.9 days. The mean hemoglobin decrease was 0.16 ± 0.88 g/dL. None of our patients had organ trauma or any other significant complication. Twenty-one patients had residual fragments and needed subsequent extracorporeal shock wave lithotripsy. The total SFR with an auxiliary procedure was 80%. Blood transfusions were needed in one patient. The average stone size was 46 ± 18 mm in the stone-free group and 55 ± 20 mm in patients without stone-free status, which was statistically significant (P = 0.027). Conclusion: Tubeless mini-PCNL was thus found to be safe and effective, even in patients with renal and upper ureteral stones ≥3 cm. Studies with a larger cohort may be required to finally validate this technique.

Keywords: Kidney stones, mini-percutaneous nephrolithotomy, ureterorenoscopy

How to cite this article:
Lee YC, Jou YC, Cheng MC, Shen CH, Lin CT. Tubeless mini-percutaneous nephrolithotomy for the treatment of renal and upper ureteral stones of ≥3 cm in diameter. Urol Sci 2020;31:68-72

How to cite this URL:
Lee YC, Jou YC, Cheng MC, Shen CH, Lin CT. Tubeless mini-percutaneous nephrolithotomy for the treatment of renal and upper ureteral stones of ≥3 cm in diameter. Urol Sci [serial online] 2020 [cited 2020 May 28];31:68-72. Available from: http://www.e-urol-sci.com/text.asp?2020/31/2/68/283255

  Introduction Top

Urolithiasis is a common disease and is considered a relevant public health problem worldwide, with a prevalence rate of 8.8% in the USA and annual health-care costs of approximately USD 3.8 billion.[1] Although kidney stones initially often remain asymptomatic, treatment is commonly performed to prevent future complications associated with the disease (e.g., renal colic, urinary tract infections, and impairment of kidney function).[2] The surgical treatment of kidney stones is complex because multiple competitive treatment modalities are available and more than one modality may be appropriate in some cases. The selection of proper treatment, which is directed by patient- and stone-specific factors, remains the most significant predictor of successful outcomes. The treatment for kidney stones should achieve both high stone-free rates (SFRs) and low complication rates. Extracorporeal shock wave lithotripsy (ESWL) and flexible ureterorenoscopy (URS) are the common treatment options for kidney stones of <20 mm in diameter.[3] The American Urological Association Guidelines recommend percutaneous nephrolithotomy (PCNL) as the first-line treatment for patients with a large renal stone (>20 mm)[4] because it has a higher SFR than SWL or URS and is less invasive than open surgery or laparoscopic/robotic-assisted procedures.[5] Compared with SWL, SWL often requires multiple treatments and has the risk of ureteral obstruction (colic or steinstrasse), which requires adjunctive procedures.[6] For large or complex renal stones, treatment methods that can achieve complete stone-free status with minimal morbidity and least number of procedures are ideal. The traditional standard procedure is open nephrolithotomy, which evolved into PCNL or retrograde intrarenal surgery (RIRS).[7] RIRS is not recommended as the first-line treatment for stones of >20 mm in uncomplicated cases as it has a low SFR and staged procedures have become necessary.[8],[9] PCNL is the gold standard procedure for large kidney stones owing to its high SFR, and the procedure can be safely performed by well-trained urologists within short time.[10],[11] However, PCNL is still considered a challenging surgical technique and can be associated with severe complications, which may compromise its efficacy. To decrease morbidity associated with large instruments, such as blood loss, postoperative pain, and potential renal damage, the standard PCNL has been developed. To reduce the invasiveness of conventional PCNL, the application of a miniaturized instrument for PCNL was first developed by Jackman et al.[12] Since then, the method has become a treatment option for adults. The term “mini-PCNL” is commonly used for access sheaths below 20 Fr.[13],[14] Stent- and drainage tube-related pain is one of the most common urologic complaints among operative patients. Modern techniques have begun to reexplore the idea of PCNL without the standard nephrostomy drainage. Tubeless PCNL refers to internal drainage with the use of a ureteral stent without the placement of nephrostomy tube after the procedure. Several studies have demonstrated the safety and efficacy of this approach.[15] Previously, nephrostomy tubes were believed to provide hemostasis along the tract, prevent urinary extravasation, and maintain adequate drainage of the kidney.[16] However, based on the concept, that the tube is only used to maintain adequate drainage of the kidney, the idea of a tubeless method has been considered. Since Bellman et al. first reported PCNL without a nephrostomy tube after the procedure in 1997, tubeless PCNL has been extensively evaluated.[17] Shah et al. have compared the outcomes of tubeless PCNL with those of small-bore nephrostomy drainage after PCNL and reported that patients undergoing tubeless PCNL experienced significantly less postoperative pain and required less analgesia and were discharged 9 h and earlier than other patients.[18] Agrawal and Agrawal have shown that tubeless PCNL has favorable outcomes in patients with stones of <3 cm.[19] To decrease the morbidities associated with the use of larger instruments and nephrostomy tube, which include blood loss, postoperative pain, and potential renal damage, a combination of mini-PCNL and tubeless technique has been developed. The current retrospective analysis aimed to report the use of the tubeless mini-PCNL technique in patients with renal and upper ureteral stones of ≥3 cm in diameter, with a focus on stone clearance, complications, and retreatment rate.

  Subjects And Methods Top

All the patients treated for large renal and upper ureteral stones (with the largest diameter of >30 mm on plain radiography or computed tomography [CT] scan) with the tubeless mini-PCNL technique at our hospital from March 2017 to September 2019 were included in the study. In our study, we included both male and female patients aged >18 years with unperforated renal cavities prior to surgery. However, patients with a single kidney or a congenital malformation and those who underwent bilateral PCNL were excluded. All the patients underwent noncontrast-enhanced abdominal CT scan prior to surgery and had negative urine culture findings. Tubeless mini-PCNL was performed under general anesthesia, while the patients were in a prone position. The study protocol was approved by the institutional review board of Chia-Yi Christian Hospital (IRB No. IRB2020001). Informed consent was confirmed by the IRB.

During tubeless mini-PCNL, an occlusive balloon catheter was inserted through cystoscopy at the beginning of the procedure. The renal puncture was performed under ultrasound guidance, and the renal access tract was dilated with a coaxial metal dilator to facilitate the insertion of a 15-Fr miniature nephroscope (Richard Wolf, Knittlingen, Germany). The stone was disintegrated with a ballistic lithotripter, and a double J catheter was inserted after the stone was completely removed. Then, the renal access tract was packed with oxidized regenerated cellulose strips (SURGICEL®, Ethicon Inc., Somerville, NJ, USA) without placement of a nephrostomy tube. The access tract wound was closed with a suture, and a Foley catheter was inserted for overnight urine drainage. The patients underwent plain radiography of the kidneys, ureters, and bladder (KUB) and abdominal ultrasonography immediately after the surgery. Hemoglobin, serum creatinine, and C-reactive protein levels were monitored perioperatively and postoperatively.

The clinical records of the patients were retrospectively reviewed to evaluate the following parameters: stone size, stone location (multiple location stones were defined as stones in two or more locations of the upper urinary tract), operative time (defined as the time from puncture to closure of the access tract), complete SFR, requirement for auxiliary procedures, overall SFR with an auxiliary procedure, complications, mean length of hospital stay, hospital readmission, and emergency department visit.

The primary endpoint was stone-free status, which was defined as the absence of residual stones of >0.3 cm on KUB radiography and ultrasonography immediately after surgery. Complication was defined as any adverse events intraoperatively or ≤30 days after the procedure. The grade of complication was determined according to the Clavien grading system and its modification for percutaneous procedures.[20]

  Results Top

Between March 2017 and September 2019, 82 patients with renal and upper ureteral stones of ≥30 mm were treated with tubeless mini-PCNL at our institution.

The characteristics of the stones and patients are summarized in [Table 1]. The mean age of the patients was 57.9 ± 10.5 years, and 72% of the patients were males. The mean body mass index was 26.0 ± 3.8 kg/m[2], and the mean stone size was 50.3 ± 19 mm. Due to the large size of the stones, most of them were located in more than one location, 59.7% (n = 49). A single-tract procedure was performed in all the patients. The perioperative and postoperative parameters are presented in [Table 2]. The average operative time was 107.7 ± 41.8 min. Moreover, 44 (54%) of the 82 patients were completely stone free after the first procedure. Twenty-one (26%) patients had residual fragments and required subsequent ESWL. The overall SFR of auxiliary procedures was 80% (65/82). None of the patients who were stone-free required more than one auxiliary procedure. A mean hemoglobin decrease of 0.16 ± 0.88 g/dL was observed between admission and first postoperative day. Based on the classification of PCNL complications using the modified Clavien grading system, 17 patients had Grade 2 complications (urinary tract infection [n = 16] and blood transfusion [n = 1]). Grade 3 or 4 complications were not observed. The mean hospital stay was 3.5 ± 1.9 days. None of the patients required hospital readmission or emergency department visit.
Table 1: Baseline stone and patient characteristics (n= 82)

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Table 2: The patients' operative and postoperative characteristics

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The average age, BMI, operation time, hospital stay, decrease in hemoglobin, and complications rate of patients with and without stone-free status were not statistically significant [Table 3]. However, the average stone size was 46 ± 18 mm in the stone-free group and 55 ± 20 mm in patients without stone-free status, which was statistically significant in both groups (P = 0.027).
Table 3: Demographic and clinical characteristics of patients with and without stone free

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  Discussion Top

Percutaneous access to the renal collecting system results in a high SFR; therefore, it is considered the treatment of choice for renal stones measuring >20 mm in diameter.[21] In general, PCNL is considered a demanding procedure, but it is safe and effective when performed by experienced urologists.[22] Conventional PCNL is usually performed through the renal access with a diameter of 24–34 Fr. Reducing the diameter of the renal access sheath leads to the use of the mini-PCNL technique.[23] Meanwhile, mini-PCNL can reduce blood loss and transfusion rate compared with conventional PCNL.[24] To further reduce the morbidity of the procedure, mini-PCNL has been established, which is characterized by a small-bore renal access (18 Fr), one-step dilatation technique, continuous low-pressure irrigation that facilitates rapid stone retrieval without the use of stone forceps or baskets, and direct closure of the renal access without the placement of a nephrostomy tube. The safety, feasibility, and efficacy of the procedure in the treatment of small renal and lower calyceal calculi have been reported in earlier studies.[21] Although the use of mini-PCNL leads to complete stone clearance in 92.9% of patients with renal stones of <20 mm,[21] its efficacy in patients with a larger stone has been questioned. Moreover, whether the smaller access and putatively reduced irrigation flow lead to poorer visibility, difficulties in handling endoscopic graspers, and subsequently reduced stone clearance has been argued.[25] The nephrostomy tube may be a cause of postoperative pain. To reduce this tube-related complication, modifications, including the use of tubeless PCNL, have been presented. One of the advantages of tubeless PCNL is reduced postoperative discomfort and pain associated with the tube and decreased requirement of analgesics.[26] The current retrospective analysis aimed to determine the safety and efficiency of tubeless mini-PCNL in treating renal and upper ureteral stones with a diameter of ≥30 mm. The primary SFR of all tubeless mini-PCNL procedures in the current patient population was 54%. A total of 21 patients underwent a single session of ESWL for residual stones and became stone-free, thereby improving our complete stone clearance rate after auxiliary procedures to 80%. A sample size of each subgroup that is too small reduces the power of the analysis, which renders the analysis subgroup SFR meaningless. Considering that the mean stone size in our analysis was larger than that in previous studies, we assumed that stone clearance is not affected by the small diameter of the access tract. Stone retrieval using the vacuum cleaner effect of continuous low-pressure irrigation without the need for endoscopic manipulation with stone graspers might contribute to an effective stone clearance and accelerate the procedure.[27] The mean operative duration in our study was 107.7 min. Data about whether miniaturization of the access sheath lead to a longer operative time in patients with large stones are contrasting. A comparative trial of 180 patients who underwent either conventional or mini-PCNL has found that mini-PCNL has significantly long operative time for simple (89.4 vs. 77.0 min), staghorn (134.3 vs. 118.9 min), and multiple (113.9 vs. 101.2 min) stones.[28] In contrast, in a prospective comparative study between conventional and mini-PCNL in 50 consecutive patients, Knoll et al. have reported no significant difference in terms of operative time between patients who underwent surgery in which an 18-Fr access sheath, rather than a 26-Fr access sheath, was used (mini-PCNL: 48 min vs. PCNL: 57 min).[24] Several factors might lead to decreased operative time in mini-PCNL, which include the one-step dilatation of the access tract and the vacuum cleaner effect that facilitates stone retrieval without the need of stone graspers. The so-called vacuum cleaner effect is a hydrodynamic effect attributed to the difference between the inner diameter of the access sheath and the outer diameter of the nephroscope. During continuous irrigation, a laminar low-pressure flow occurs through the access sheath. Turbulences occurring at the tip of the nephroscope facilitate suctioning of stone fragments from the renal collecting system.

Because this study was retrospective in nature, Grade 1 complications could not be assessed. Of the 82 patients who underwent tubeless mini-PCNL procedures, 17 had ≥ Grade 2 complications that required treatment. Meanwhile, 16 (19.5%) patients presented with urinary tract infection requiring additional antibiotics and one (1.2%) with significant blood loss requiring blood transfusions. However, none of the patients had severe complications (Grades III, IV, and V). The complication rate in this study is similar to that in previous studies; generally, the occurrence of higher grade complications (> Grade II) is rare.[22] One major concern related to PCNL is significant blood loss requiring blood transfusions. In the present investigation, the mean decrease in hemoglobin level was 0.16 g/dL; one patient needed a blood transfusion (transfusion rate: 1.2%), and all cases were managed conservatively by intravenous fluids and anti-bleeding measures. The low transfusion rate in mini-PCNL might be attributed to minimal parenchymal trauma and reduced risk of injury in larger segmental renal vessels with the use of a small-bore dilator during the establishment of the access tract. The reduced transfusion rate has also been reported in previous studies. The stone size has also been identified as a delimitating factor for the success of PCNL treatment. In the subgroup analyses, incomplete stone extraction occurred more commonly in patients with larger renal stone size (44 ± 18 mm vs. 55 ± 20 mm; P = 0.027).

The present study investigated the feasibility of tubeless mini-PCNL for treating renal and upper ureteral stones of ≥3 cm in diameter. Results showed that the SFR of the minimally invasive approach was similar to that of other procedures with an acceptable operative time and low morbidity. The present study had limitations. That is, it did not include a comparative control population. However, based on the relatively large number of patients with a large stone, a comparison of contemporary publications can help assess the advantages and disadvantages of the minimally invasive approach.

  Conclusion Top

Tubeless mini-PCNL is effective in patients with large renal stone. The SFR of this method was compared with that of large-bore conventional PCNL. The procedure does not tend to have a long operative duration and high-grade complications. Moreover, we believe that tubeless mini-PCNL is a unique and good technique that can be safely used. However, studies with a larger cohort must be conducted to further validate the efficacy of this method.

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  References Top

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  [Table 1], [Table 2], [Table 3]


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