European Journal of Cardiovascular Medicine

An effort has been made to reduce the complications during the surgical procedure known as percutaneous nephrolithotomy (PCNL) by using a smaller version called miniaturized PCNL (MPCNL) [1,2]. It is assumed that reducing the diameter of the PCNL tract will result in reduced damage to the renal parenchyma [3–5]. However, flexible ureterorenoscopy (fURS) has significantly advanced due to the progress in laser technology and the reduction in scope width, while still providing sufficiently big working channels to accommodate all necessary attachments.

Improved digital image quality and enhanced mechanical properties, such as increased deflection and endurance. The use of fURS has significantly broadened the range of conditions that can be treated with retrograde intrarenal surgery (RIRS) [6–8]. According to international guidelines, renal stones larger than 2cm in diameter should be treated with PCNL, while those with a diameter smaller than 1-2cm should be treated with RIRS. However, mini-PCNL is a viable and effective minimally invasive treatment option for even smaller stones. On the other hand, the limits of RIRS are constantly being expanded to include larger stones. Both methods have advantages and disadvantages, but they also differ in terms of costs. Miniaturized PCNL tools can be reused multiple times, while flexible ureteroscopes and devices are either disposable or still highly delicate. The latter option leads to significant operational and maintenance expenses in addition to the initial financial investment required to purchase the equipment. This is especially crucial in a growing nation such as India. Hence, international comparative studies conducted in the western world may not be entirely applicable to our specific circumstances, as economic constraints play a crucial role in determining outcomes.

Hence, our study aimed to compare the local clinical results of mini percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS) in the management of renal stones with a diameter of 1-2 cm.

The study included RIRS and mini-PCNL procedures performed by a single surgeon in a tertiary care hospital in central India for renal stones measuring 1- 2 cm. The study excluded individuals who received treatment other than ESWL for the same stone, as well as paediatric patients. Prior to surgery, all patients underwent preoperative assessments including serum biochemistry, renal function tests, urine routine microscopy and culture, radiography, Urinary System Ultrasonography (USG) and CT intravenous pyelogram (CT IVP). Patients who had evidence of bacterial growth in their urine cultures were not subjected to surgery until the culture tests showed no signs of infection. These patients were treated with antibiotics based on the results of their antibiogram. Spinal anaesthesia was selected for mini PCNL, whereas General anaesthesia was used for RIRS procedures.

Group-1– consist of 55 patients undergoing RIRS Procedure.

Group-2 –consist of 45 patients undergoing Mini-PCNL Procedure.

Mini-PCNL technique:

 Following the administration of anaesthesia, patients were positioned in the dorsal lithotomy posture. A 20 F rigid cystoscope was used to access the external urethra, and a hydrophilic guide wire was inserted into the appropriate ureter. Subsequently, a 6 French open-ended ureter catheter was placed and a 14 French Foley catheter was introduced. Next, the patient was repositioned in a prone position and a 50% diluted non-ionic contrast material was administered through the ureter catheter under fluoroscopy. This allowed all calices to be filled with the opaque substance. If feasible, entry was obtained via the posterior lower calyx below the 12th level. In cases where access through this calyx was not available, access through the middle and higher calices was achieved through intercostal pathways. Bull’s eye and triangulation technique is employed to puncture renal calyces under fluoroscopy. Following the insertion of an 18G needle, a guide wire was introduced into the intrarenal system and, if feasible, guided towards the upper calyx or ureter. Subsequently, alkane metal dilators were placed in the kidney using the guide wire.

Next, a 16.5/17.5 French (F) operative sheath was placed above the dilators. Then, a 12 F nephoscope was used to enter the lower calyx and visualise the surgical area and stone. The stones were shattered using a pneumatic lithotripter. If feasible, the process of breaking into sizable fragments was guaranteed, and these fragments were thereafter extracted using forceps through the access point.

Fluoroscopy and nephoscopy were employed after the surgery to verify the absence of any kidney stones that could be extracted from within the kidney. All patients in both groups underwent procedure of double J stent placement after stone clearance. Subsequently, a 14 French ryles tube was inserted and retained as a nephrostomy tube in few selected patients with excess or persistent bleed. Patients experiencing significant bleeding through the tube clamped for a duration of 24 hour. After 24 hr tube unclamped and connected by urine bag to check for bleeding still present or not. If haemorrhage has stopped, nephrostomy removed in subsequent 12 hours. Patients were scheduled for two follow-up appointments: one week and one month after their initial visit. The check-up studies consisted of a hemogram, creatinine test, X ray KUB and kidney urinary bladder ultrasonography (USG KUB). Double J stent implanted underwent stent removal during the fourth week. Patients who still had stones in the kidney or ureter underwent extracorporeal shock wave lithotripsy (ESWL) and either retrograde ureteroscopy (R-URS) or flexible ureteroscopy (F-URS).

RIRS technique-

 General anaesthesia was delivered to the patients. Following the administration of anaesthesia, patients were repositioned into the dorsal lithotomy posture. Initially, the external opening of the urethra was accessed using a procedure called R-URS. Subsequently, a hydrophilic guidewire was inserted through the appropriate opening of the ureter, and then the R-URS was advanced into the ureter. Patients who were unable to have their ureter accessed underwent a DJ stent implanted for a period of 2 to 4 weeks. A hydrophilic guidewire was used to introduce a 9.5/10.5 f, 11/13 F, or 13/15 F access sheath (Cook medical) or, for certain patients, an F-URS (Karl Storz, Tuttlingen, Germany) was sent straight to the kidney over the guidewire.

Fluoroscopy was used for all procedures in which the guidewire advanced from the ureter to the kidney, the access sheath was inserted, DJ stent was implanted, or direct removal over the guidewire was performed. During the surgery, fluoroscopy was employed using a solution of diluted contrast material to locate the opening of calyx containing stone and determine the dimensions of the pelvicalyceal angle, infundibular length, and width. The stones were fractured using a holmium-YAG laser. The dusting mode was used to powder small stones, while the fragmentation mode was used to fragment large stones into small stones. Stone shards larger than 2 mm were extracted using a nitinol-tipped basket forceps. The dusting mode utilises a high frequency range of 8-12 fr and a low energy range of 5-8 Joules, whereas the fragmentation mode utilises a low frequency of 5 fr and a high energy range of 8-10 Joules. During the surgical procedure aimed at enhancing image clarity, the pressure was applied using the pump from a fluid set, even in the absence of an irrigation pump. Following the surgical procedure, a thorough examination of all calices and the renal pelvis was conducted using fURS to identify if any stones remained and to confirm the absence of residual fragments. Fluoroscopy was employed specifically for stones that are not transparent. Every patient underwent the insertion of a DJ stent. Patients who were able to tolerate the DJ stent had it extracted after a duration of 4 weeks. Patients were scheduled for follow-up appointments at intervals of one week and one month.

Statistical analyses

Data analysis was conducted using an online tool that was available at no cost.

The results are reported as either the mean or as a percentage (%). Continuous variables were compared using either the student t-test or the Mann-Whitney U test, depending on the circumstances. The categorical variables were analysed using either the chi-square test or Fisher's exact test. The statistical significance was established with a p-value of less than 0.05.

The demographic and stone characteristics of two groups, Group 1 and Group 2 were compared in this study. Group 1 had an average age of 47.08 years with a standard deviation of 14.71, while Group 2 had an average age of 48.42 years with a standard deviation of 13.46, showing no significant difference (p=). Gender distribution showed 34 males and 21 females in Group 1, compared to 31 males and 14 females in Group 2, with no significant difference observed (p=). Body Mass Index (BMI) was slightly lower in Group 1 (26.08 kg/m2 ± 4.52) compared to Group 2 (27.05 kg/m2 ± 3.30), but this difference was not statistically significant (p=0.085). The prevalence of comorbid disorders differed significantly between the two groups (p=0.007), with hypertension (ht) and diabetes mellitus (dm) being reported in both groups, and COPD and antiaggregant (presumably indicating antiplatelet medication) reported only in Group 1. Lateral site distribution of stones showed no significant difference between the groups (p=0.291), with similar proportions of stones located on the right, left, or bilaterally. However, Group 2 having larger stones (16.05 mm ± 3.30) compared to Group 1 (15.03+-6.31). Overall, the study highlights differences in comorbidities and stone size between the two groups, with potential implications for treatment strategies and outcomes.

COPD (chronic obstructive pulmonary disease), BMI (Body Mass Index), Sd; standard deviation, P<0,005, Significant.

Table 2 presents the surgical features comparison between Group 1 and Group 2. Group 1 had a longer average operation time (69.30 minutes ± 13.5) compared to Group 2 (53.54 minutes ± 11.99), with a statistically significant difference (p=0.036). Similarly, the fluoroscopy time was significantly longer in Group 2 (4.79 minutes ± 1.57) compared to Group 1 (1.03 minutes ± 0.45) (p<0.001). Haemoglobin levels decreased significantly post-operation in both groups, with a greater reduction observed in Group 2 (2.07 g/dL ± 1.14) compared to Group 1 (0.57 g/dL ± 0.39) (p<0.001). Stone-free rates (SFR) showed no significant difference between the two groups at the end of 1 week and 1 month follow up. However, Group 2 had a higher visual analogy scale (VAS) pain score (4.57 ± 1.12) compared to Group 1 (4.0 ± 1.52) (p=0.003). Hospital stay was significantly longer in Group 2 (48 ± 12 hours) compared to Group 1 (36 ± 12 hours) (p<0.001). Anesthesia type showed a significant difference between the groups (p<0.001), with more patients in Group 1 receiving general anesthesia (45) compared to Group 2 (36). Overall, these findings underscore the differences in surgical outcomes and interventions between the two groups, potentially influencing post-operative recovery and patient satisfaction.

VAS is for Visual Analog Scale, HB stands for Haemoglobin, SFR stands for Stone Free Rate. The value of P is less than 0.005, indicating statistical significance.

Table 3 summarizes the complications encountered in both Group 1 and Group 2. In Group 1, there were a total of 6 complications (10.8%), while in Group 2, there were 5 complications (10.4%), with no statistically significant difference between the groups (p value not provided). Complications in Group 1 included urosepsis (2 cases), fever (2 cases) and gross haematuria (1 case). In Group 2, complications included subcapsular hematoma (1 case), gross haematuria (1 case), stein Strasse (1 case), hydrothorax (1 case), leak of nephrostomy (1 case), and one case of reversible rise in renal function test. Overall, both groups had similar rates of complications, highlighting the importance of monitoring and managing post-operative complications in patients undergoing surgical interventions for urolithiasis.

RFT stands for renal function tests. The p-value of 0.005 indicates that the results are statistically significant.

The inferior calyx of the kidney poses a higher risk of stone formation and presents greater challenges for stone therapy due to anatomical disadvantages in comparison to other areas of the kidney. ESWL provides highly favourable stone-free rates (SFR) for lower calyx stones measuring up to 1 cm. However, for stones larger than 2 cm, there are several uncertainties involved. These include the potential formation of stone routes due to stone pieces, the possibility of incomplete fragmentation of stones, and the risk of fragments not being expelled from the calyx [9].

Currently, the most effective treatment options known for kidney stones larger than 2 cm are standard and/or miniature percutaneous nephrolithotomy (PCNL) methods. For all types of kidney stones, including the lower calyx, stone free rates ranging from 85% to 100% can be achieved. However, the procedure carries the risk of blood loss, injury to surrounding organs, and damage to the kidney's parenchyma. Mini-percutaneous nephrolithotomy (Mini-PCNL) has been implemented to mitigate the problems associated with conventional percutaneous nephrolithotomy (PCNL) [10].

The recent advancements in flexible endoscopic technology have made it easier to access the most challenging calyx of the lower calyx using Retrograde Intrarenal Surgery (RIRS). This is owing to the 270-degree bending capabilities and improved picture quality, particularly for upper urinary tract stones. Current guidelines suggest that flexible ureterorenoscopy (URS) is a viable therapeutic option for upper urinary system stones that are smaller than 2 cm and do not respond to extracorporeal shock wave lithotripsy (ESWL) [9]. For this specific category of stones, the stone-free rates are higher when using this method compared to ESWL. Many writers in the literature seem to prefer using RIRS for some patients with large stones, either to mitigate the potential complications associated with PCNL procedures or due to the high danger that PCNL poses to the patient. For patients who are at high risk for mini-PCNL surgery, such as those with haemorrhagic diathesis, morbid obesity, and musculoskeletal system deformities, it is more reasonable to consider RIRS instead of mini-PCNL for anterior calyx stones that are difficult to access with mini-PCNL, stones that require multiple access, and stones located in a solitary kidney or in the upper level of the ureter. Additionally, it is important to consider body habitus, renal anatomy, cost, and patient preference when deciding which treatment strategy to apply for patients [11,12].

Currently, there has been a surge in urologists' interest for native tract surgery. To provide guidance to our urologist colleagues, we conducted a comparative analysis of surgical outcomes between mini-PCNL and the current trend of RIRS for renal stones measuring 1-2 cm. We found limited references in the existing literature on this topic. In contrast to mini-PCNL, the effectiveness of the flexible URS for treating lower calyx stones depends on certain anatomical parameters of the kidney, such as IPA, IW, IL, and PCH [13]. Retrograde intrarenal surgery (RIRS) has been shown to achieve stone-free rates ranging from 60% to 93% for lower calyx stones in patients who meet these favourable criteria [14,15]. Mini-PCNL has been shown to achieve stone-free rates ranging from 90% to 97% for lower calyx stones [15]. The experience of the surgeon is crucial in enhancing the success of both surgeries. When analysing multiple studies comparing routine percutaneous nephrolithotomy (PCNL) with retrograde intrarenal surgery (RIRS) for lower calyx stones measuring 2 cm, [11,12,15-19] it was determined that PCNL outperformed RIRS in terms of hospital stay, morbidity, haemoglobin decrease, and use of fluoroscopy. RIRS was identified as a viable substitute for invasive PCNL in this specific population of patients with stones. It is important to remember that achieving satisfactory results with RIRS for lower calyx stones may require multiple sessions and the use of other modalities for assistance [14,20].

In a retrospective study conducted by Li et al., mini-PCNL (16 F surgical sheath, 10 F nephoscope) was compared with RIRS for the treatment of lower calyx stones measuring 1.5-2.5 cm. The study found that RIRS had advantages over mini-PCNL in terms of shorter hospital stay and cheaper cost [21]. The results indicated that the average duration of surgery and the overall rates of successful stone removal were comparable for both techniques. They highlighted that RIRS could serve as a viable alternate therapy option to mini-PCNL for lower pole stones.

The meta-analysis conducted by Gao et al. found that mini-percutaneous nephrolithotomy (mini-PCNL) had a higher success rate than retrograde intrarenal surgery (RIRS) for treating lower calyx stones, as measured by stone-free rate (SFR) [22]. However, RIRS was associated with shorter hospital stays and smaller decrease in haemoglobin levels. The study revealed that the SFR rates for short tract operations such as ultramini- and micro-PCNL were comparable to those of RIRS.

 In prospective randomized research, Fayad, et al. conducted a comparison between tube-free mini-PCNL and RIRS for lower calyx stones that were smaller than 2 cm [23]. The researchers discovered that mini-PCNL had a drawback in terms of the length of hospital stay, but it was more beneficial than RIRS in terms of surgical duration. Regarding stone-free rate (SFR), mini-percutaneous nephrolithotomy (mini-PCNL) achieved a higher success rate compared to retrograde intrarenal surgery (RIRS), with percentages of 92.72% and 84.31% for mini-PCNL and RIRS, respectively. The study revealed a greater incidence of elevated body temperature following RIRS.

Jiao, et al. found that mini-PCNL was more efficacious than RIRS for treating lower calyx stones measuring 1-2 cm [24]. However, the patients who underwent mini-PCNL had a lengthier hospital stay and a higher occurrence of hematoma. Both approaches yielded identical results in measuring postoperative pain and surgery time. In a prospective and randomized controlled trial conducted by Lee et al., it was determined that both RIRS and mini-PCNL procedures were equally effective in terms of stone-free rate (SFR), surgical duration, amount of haemoglobin decrease, and length of hospital stay for kidney stones larger than 1 cm. [25] Nevertheless, the RIRS group experienced more severe postoperative VAS scores and had higher analgesic needs. Wilheim, et al. conducted a comparative study between ultramini-PCNL and RIRS for the treatment of kidney stones ranging in size from 10-35 mm [26]. Both the UM-PCNL and RIRS procedures showed comparable success rates (92% vs. 96%) for medium and large kidney stones. However, RIRS had the advantage of shorter hospital stays. Gross et al. documented the efficacy of RIRS (retrograde intrarenal surgery) for lower pole stones when conducted by skilled professionals [27]. They found that this procedure had low rates of complications and was more advantageous than invasive percutaneous procedures in terms of morbidity. De, et al. conducted a meta-analysis study and found that RIRS was superior to minimally invasive PCNL in terms of stone-free rate (SFR) for stones smaller than 2 cm [28].

According to their statement, RIRS was found to have the advantage of shorter hospital stays compared to PCNL procedures. However, it was observed that RIRS had higher complication rates and greater reduction in haemoglobin levels. Jiang, et al. conducted a meta-analysis comparing RIRS with mini-PCNL, analysing 13 papers. They found that the stone-free rate for kidney stones was statistically higher with mini-PCNL [29]. Pelit, et al. conducted a retrospective study to assess the effectiveness of RIRS and mini-PCNL in treating kidney stone patients with an average stone size of 2 cm [30]. The surgical length, fluoroscopy duration, and hospital stay were longer for mini-PCNL compared to other procedures. However, when auxiliary methods were used, the final stone-free rates (SFR) were 90.6% and 91.1% for RIRS and mini-PCNL, respectively. In both approaches, no significant complications, as classified by the Clavien Dindo system, were encountered.

Ramon and his colleagues conducted a comparison between miniperc and RIRS. Miniperc showed drawbacks in terms of decreased haemoglobin levels [31], increased need for pain-relieving medication, and longer hospital stays. On the other hand, RIRS had drawbacks of requiring many sessions for treating big volume stones, longer surgical procedures, and greater costs for hospital stays. After a single session of mini-percutaneous nephrolithotomy (mini-PCNL), the success rate of 82.3% at the end of the first month climbed to 93.75% after three months with the addition of auxiliary treatments such as extracorporeal shock wave lithotripsy (ESWL) and ureteroscopy (URS). Considering these principles, for patients who have favourable anatomical conditions and stones of 1-2 cm, we believe that mini PCNL could serve as a viable alternative to invasive RIRS procedures. Our study revealed a complication rate of 10.8% in patients undergoing RIRS, and a complication rate of 10.4% in patients undergoing mini-PCNL. Most problems associated with mini-PCNL in the literature are classified as grade 1, with the majority falling below grade 3. Reported frequencies of these issues range from 11.9% to 37.9%. In line with previous research, our mini-PCNL group did not experience any grade 4 or 5 problems, as reported in the literature [10, 29].

For retrograde intrarenal surgery (RIRS), the majority of complications have a severity level below Clavien 3, with reported rates ranging from Out of all the patients in our series. Out of the complications associated with RIRS, 50% were classified as grade 1 complications, specifically urosepsis. Preoperative factors such as the size of the stone, the presence of postoperative residue, and comorbidities such as diabetes mellitus and cardiovascular disease, contribute to higher rates of postoperative complications in both RIRS and mini-percutaneous nephrolithotomy (PCNL) procedures. In mini-PCNL, the pressure during the entire surgery remains below 20 mmHg, whereas in RIRS procedures, it can exceed 40 mmHg. Increased intrarenal pressure during surgery can lead to a higher incidence of urosepsis following RIRS. Following mini-percutaneous nephrolithotomy (mini-PCNL), there was a reduction in haemoglobin levels and a higher need for blood transfusion compared to retrograde intrarenal surgery (RIRS). Mini-PCNL results in a more significant decrease in haemoglobin levels compared to RIRS (9). According to reports, the rates of blood transfusion and embolization required with mini-PCNL range from 0.85% to 3% [20, 29]. Among our patients, 2.1% need blood transfusion.

Mini-PCNL causes a greater decrease in haemoglobin levels compared to RIRS [29]. It has been reported that blood transfusion and embolization are required in 0.85-3% of cases during Mini-PCNL [13,23]. We needed blood transfusion in 2.1% of our patients. In their meta-analysis, Jiang et al. found that the complication rate for RIRS was lower than that of mini-PCNL. They observed equal rates of Clavien grade 1 and 3 complications between the two procedures, but RIRS had fewer grade 2 issues compared to mini-PCNL. The incidence of bleeding was shown to be greater with mini-percutaneous nephrolithotomy (mini-PCNL) [29]. In a meta-analysis conducted by Jones, it was discovered that there was a complication rate of 15.2% following mini-PCNL. Based on the Clavien classification, they documented that 44% of the cases had Grade 1 problems, 28% had Grade 2 complications, and another 28% had Grade 3 complications. None of the patients exhibited Clavien grade 4 or 5 problems [10]. Fluoroscopy is utilized throughout all stages of percutaneous nephrolithotomy (PCNL) to guide the insertion of the nephoscope into the kidney and provide visual imaging of the stone. However, it poses a potential health hazard for the clinician, patient, and surgical staff involved in the procedure. Both our investigation and previous literature have found that mini-PCN l is less favourable compared to RIRS in this aspect [29].

Currently, there are authors who are able to achieve the same level of surgical success without using fluoroscopy. RIRS stands for Retrograde Intrarenal Surgery. Using ultrasonography as the first step in accessing the kidney with mPCNL can marginally decrease the amount of exposure to fluoroscopy. Our study focused on the evaluation of Visual Analog Scale (VAS) scores within the initial 12 hours after surgery. Our findings indicate that Retrograde Intrarenal Surgery (RIRS) demonstrated a statistically significant benefit over Mini Percutaneous Nephrolithotomy (mPCNL), aligning with the majority of previous research. Pain is a condition that prolongs the length of hospital stay and necessitates the administration of additional narcotic analgesics and anti-inflammatories. The use of a nephrostomy tube, urethral with ureteral catheter, and invasive entrance into the muscle group in the flank area and kidney capsule-parenchyma results in a greater sensation of pain during mPCNL compared to native ureter surgery (RIRS). Alongside the pain score, the RIRS group showed a statistically significant lag in analgesic usage compared to mPCNL patients, both in terms of the range of medicines used and the frequency of usage. Although RIRS may seem beneficial in terms of perioperative pain, it is important to take into account the lower urinary tract issues associated with DJ stent after being discharged. The majority of patients express dissatisfaction with lower urinary tract system issues, and a portion of them opt to have the stent removed within the early stages. The period of hospitalization for mPCNL was notably prolonged in our study conducted by Bryniarski et al. A meta-analysis conducted by Kang found that RIRS (retrograde intrarenal surgery) was associated with a shorter hospital stay compared to other treatments. The mean difference in hospital stay was 2.21 days, with a 95% confidence interval of 0.49 to 3.93 days (P=0.12) [19]. Due to the fact that RIRS is performed through the natural path, each step of the surgery is carried out with visual guidance and has a low risk of complications. As a result, it is projected that the period of hospital stay for RIRS will be longer than that for PCNL. The primary constraint of our study is the comparatively small sample sizes in both groups. One major limitation of RIRS is the exorbitant expense associated with flexible URS, equipment, and laser lithotripsy, particularly in developing nations.

We believe that RIRS is comparable to mini-PCNL for upper and middle calyceal stones measuring 1-2cm in terms of hospital stay, stone-free rate, and need for repeated sessions. While mini PCNL is superior to RIRS for lower calyceal stones measuring 1-2cm as stone free rate is higher in mini PCNL and duration of surgery along with cost of surgery is also less for all renal stones. RIRS is a viable alternative method due to its advantages in terms of complications, duration of hospital stays, reduced pain complaints, lower painkiller requirements, and decreased blood loss.

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