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REVIEW ARTICLE
Year : 2023 | Volume
: 34
| Issue : 4 | Page : 164-169
Contemporary management of large and complex renal calculi: Have we found the perfect solution yet?
Yung-Hao Liu1, Ching-Heng Yen2, Yi-Sheng Tai3, Tai-Lung Cha1, Guang-Huan Sun1, Dah-Shyong Yu1, Sheng-Tang Wu1
1 Division of Urology, Department of Surgery, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
2 Division of Urology, Department of Surgery, Tri-Service General Hospital, Song-Shan Branch, Taipei, Taiwan
3 Department of Urology, Fu Jen Catholic University Hospital, Fu Jen Catholic University, New Taipei City, Taiwan
Correspondence Address:
Sheng-Tang Wu
Department of Surgery, Division of Urology, National Defense Medical Center, Tri-Service General Hospital, Neihu 114, Taipei
Taiwan
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/UROS.UROS_108_22
This review provides a thorough overview of contemporary treatment strategies for complex renal calculi, including large-volume stones, stones with increased hardness and greater number, or stones with abnormal anatomy. The development of tailored treatment plans for stone removal is essential for treatment success. A literature search was conducted on PubMed using the Keyword “complex renal calculi” along with “percutaneous nephrolithotomy (PCNL),” “retrograde intrarenal surgery (RIRS),” “endoscopic combined intrarenal surgery (ECIRS),” “stone free rate,” and “complications.” Based on the findings, the use of “minimally invasive PCNL,” “multiple-tract PCNL,” “staged RIRS,” and “ECIRS” is proposed in addition to the traditional PCNL suggested using the European Association of Urology guidelines. Renal calculi in patients with solitary kidneys or who underwent kidney transplants are considered to be complex, and treatment options that allow preservation of their remaining renal function should be considered.
Keywords: Complex renal calculi, endoscopic combined intrarenal surgery, minimally invasive percutaneous nephrolithotomy, multiple tract percutaneous nephrolithotomy, staged retrograde intrarenal surgery
The prevalence rate of renal calculi is approximately 1%–5% in Asia,[1] and they often require medical or surgical intervention, which can be tedious and time-consuming. This applies particularly to complex stones, and the complexity can be graded using the STONE score, with parameters consisting of size, topography, obstruction, number, and evaluation of Hounsfield units, or Guy's stone score to aid in predicting postoperative stone free rates (SFRs).[2],[3] The definition of the term “complex renal calculi” varies considerably; however, the European Association of Urology (EAU) guidelines refer to these as complete or partial staghorn stones.[4] In general, complex renal calculi include stones with large volume (size: >2 cm) and increased hardness (≥950 Hounsfield units); association with moderate-to-severe hydronephrosis; multiple stones in different parts of the pelvicalyceal system; and the association with anatomical abnormalities of the kidneys.[5],[6],[7]
Conservative treatment modalities, such as medical expulsion, can facilitate ureteral calculi passage but have minimal effect on renal calculi. In the cases of uric acid and struvite stones, alkalinizing urine through chemolysis, either percutaneously or orally, can be beneficial.[4] An improved treatment efficacy is achieved through surgical interventions such as shock wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS), and percutaneous nephrolithotomy (PCNL). The treatment modality of choice depends on the location and size of the calculi; as the concept of minimal invasiveness has gained dominance in treatment strategies, laparoscopic surgeries or open anatrophic nephrolithotomies have become less popular. Consequently, modifications in traditional PCNL and RIRS procedures have been advocated. The current study investigates possible treatment options for complex renal calculi and examines the associated stone-free and complication rates. In addition, treatment options for patients with a solitary kidney (either functionally or anatomically) exhibiting renal calculus-induced hydronephrosis that may jeopardize the kidney's remaining renal function have also been discussed.
This review aimed to analyze available evidence on complex renal calculi to assist fellow urologists in the development of treatment strategies.
Treatment StrategiesPercutaneous nephrolithotripsy
The preferred treatment for complex renal calculi is PCNL.[4] Since its introduction in 1976, it has replaced anatrophic nephrolithotomy as the standard surgical intervention for patients with renal calculi >2 cm.
PCNL typically offers higher SFR than those of SWL (relative risk [RR]: 0.69, 95% confidence interval [CI]: 0.61–0.78; P < 0.001) and RIRS (RR: 1.14, 95% CI: 1.06–1.22; P < 0.001) regardless of the size of the renal calculi; however, higher complication rates and longer hospital stay are among its limitations.[8],[9] The most common complications of PCNL include nephrostomy tube leakage (15%), transient fever (10%–30%), bleeding (blood transfusion 2%), infection (sepsis <3%), pleural injury (0.3%–1%), and injury to the adjacent organs (0.2%–1%).[10]
In patients with calculi, especially larger than 2 cm, PCNL exhibits superior SFR than that of RIRS (RR: 1.23, 95% CI: 1.10–1.37; P < 0.001), although the latter technique can also achieve comparable rates (improving from 66.6% to 87.7%) when performed along with auxiliary procedures.[8],[9],[11],[12] The differences in complication rates between the two procedures become insignificant when dealing with larger calculi. Unlike RIRS, the major concern in patients treated using PCNL is an increased bleeding risk.[8],[12] While RIRS procedures are usually associated with a longer operating time, patients receiving PCNL must stay in the hospital for longer durations (extra 3 days) because of the invasive nature of the intervention.[11],[12]
Minimally invasive percutaneous nephrolithotripsy
Since the introduction of miniaturized technology, renal stone extraction via small-sized tracts has been performed by urologists; the method was later named “mini-PCNL.” Despite the requirement of a longer operating time, mini-PCNL has the benefits of decreased risk of leakage, risk of bleeding, need for blood transfusion, and risk of renal pelvis perforation.[13],[14] Moreover, mini-PCNL often results in comparable SFR to that of standard PCNL when used for treating large (>2 cm) renal stones (odds ratio [OR]: 1.06, 95% CI: 0.64–1.74; P = 0.43) or staghorn calculi (OR: 1.11, 95% CI: 0.87–1.42; P = 0.10).[13],[14],[15] Tubeless mini-PCNL can also be used to minimize postoperative pain associated with nephrostomy tubes.[16] However, an increased risk of complications and greater likelihood of fatigue within the surgical team can result from a longer operating time, necessitating the prolongation of anesthesia,[17] which can be concerning for urologists.
Access sheaths in standard PCNL are typically 24–30 Fr, while those used in mini-PCNLs are 14–20 Fr. Smaller sheath sizes such as ultra-mini PCNLs (11–13 Fr) and micro-PCNLs (4.8 Fr) are also available and were initially designed for pediatric patients before being indicated for renal calculi <2 cm in size. These smaller access sheaths are typically associated with lower complication rates compared with those of standard PCNLs, although the SFR is compromised to 85%–92% in ultra-mini PCNLs and 85%–90% in micro-PCNLs.[18],[19] Moreover, the difficulty in efficiently extracting stone fragments through the access sheath remains a major limitation. Therefore, a careful selection of the ideal access sheath size while considering the efficacy and safety of the procedure is essential.
Multiple-tract percutaneous nephrolithotripsy
PCNL remains the first-line therapy for staghorn calculi branching into multiple calices.[4] The selection of the proper calyx to access is crucial, as maximum clearance of stone fragments through a single tract may lead to excessive torque of the nephroscope, which can injure the renal parenchyma and lead to severe bleeding.[20] Performing PCNLs through multiple tracts minimizes this risk and allows complete stone clearance in a single stage.
However, evidence on the associated SFR remains controversial. While most studies suggest similar results between single- and multiple-tract PCNLs, Wang et al. reported contradictory results of better SFRs in the single-tract PCNL group (OR: 0.37, 95% CI: 0.19–0.74; P = 0.005).[21],[22] However, such findings may be biased as surgery for smaller stone burdens typically does not necessitate the involvement of multiple tracts. The number of access points required is directly related to the stone size,[23] with most renal calculi being treated using 2–3 tracts. Compared with the “sandwich therapy,” multiple-tract PCNLs performed in one stage are typically associated with lower costs and decreased time required for auxiliary SWL, RIRS, or repeated PCNL, which is beneficial for both patients and surgeons.[24]
However, there are concerns regarding increased blood loss and impaired renal function because of the extra perforations. Indeed, single-tract PCNLs result in a lower decline in hemoglobin (<0.46 g/dL) and fewer blood transfusions.[21],[22] Some proposed that this might be a consequence of lower hemoglobin levels before surgery or conducting transfusions after several days of surgery.[23] Parenchymal damage is inevitable during PCNL, although no significant changes have been reported in pre- and postoperative creatinine levels (cumulative mean difference: −0.02, 95% CI: −0.06 to 0.02; P = 0.32) after single- and multiple-tract PCNLs.[21],[25] Moreover, no significant differences in the risk of postoperative fever (OR: 0.86, 95% CI: 0.27–2.78; P = 0.8) or urinary tract infections (OR: 0.85, 95% CI: 0.13–5.45; P = 0.87) have been reported when the two approaches are compared.[21] The risk of pulmonary complications is increased secondary to the creation of a larger number of tracts (OR: 0.28, 95% CI: 0.09–0.83; P = 0.02), particularly when performing supracostal upper-pole access.[21] Like most surgeries, effective postoperative pain control is considered extremely important. Predictors of post-PCNL pain include the following: size and number of renal calculi, presence of residual calculi, and operating time;[26] the number of access points in multiple-tract PCNL is also significantly associated with postoperative pain intensity.[23] Most patients have reported mild-to-moderate pain, with scores ranging from 1 to 6 out of 10 on a Visual Analog Scale.[23] Multiple-tract mini-PCNLs can minimize pain intensity as there are no significant differences in the analgesic drug dosage administered between single and multiple mini-PCNLs.[27]
Therefore, multiple-tract PCNL is an efficient method for treating patients with large stone burdens or staghorn stones as they are associated with acceptable complication rates.
Staged retrograde intrarenal surgery
RIRS is typically used for treating renal and proximal ureteral calculi and has several advantages, including flexible working angles, minimally invasive procedures, and superior SFR compared with that of SWL. As per the EAU guidelines, SWL or RIRS should be used when treating stones <2 cm in size and with lower complexity.[4] Larger renal calculi treated using RIRS may result in inferior SFR compared with that of PCNL.[8] Xiao et al. proposed a scoring system (RIRS) to help formulate better surgical plans,[28] which predicts SFR after RIRS. This system consists of four parameters: stone density, inferior pole stone, renal infundibular length, and stone burden.[28] Furthermore, Woranisarakul et al. evaluated patients with large renal calculi (>2 cm) and found that stones >3.5 cm in size (OR: 5.86, 95% CI: 1.77–19.57; P = 0.004) and located in the lower pole (OR: 1.97, 95% CI: 1.039–3.742; P = 0.038) were predictors of post-RIRS residual fragments.[29] Tonyalı et al. also reported that RIRS performed using ureteral access sheaths resulted in a 1.4-fold increase in SFR.[30] Although patients with stones >2 cm exhibit low initial SFR, several studies have reported SFR comparable to that of PCNL after the second session of RIRS,[11],[31],[32] i.e., “staged RIRS.”
The overall complication rates of RIRS remain lower than those of PCNL, and postoperative fever and flank pain are the most common complications of RIRS when used for treating large renal calculi.[11],[32],[33] The risk of infection from larger stones is higher as they contain a higher endotoxin load and require a longer operating time.[34] The RIRS procedure has also been reported to be associated with a significantly lower decline in hemoglobin (<0.83 g/dL).[33] Lin et al. reported that approximately 45.4% of patients with large stones underwent staged RIRS because of the comorbidities such as chronic obstructive pulmonary disease, cardiovascular disease, and stroke.[32] Therefore, patients with complex renal calculi that are unsuitable for PCNL because of the presence of comorbidities or other contraindications such as unresolved bleeding tendencies or pregnancy can be treated with staged RIRS because of its comparable efficacy and superior safety.
Endoscopic Combined Intrarenal Surgery
Dr. Gaspar Ibarluzea and his Assistant Dr. Aurelio Jorge first suggested the concept of combining PCNL and rigid ureteroscopes.[35] Consequently, combined antegrade and retrograde approaches have mainly been performed in modified prone positions.[36] Dr. Cesare Macro Scoffone introduced endoscopic combined intrarenal surgery (ECIRS) and proposed the Galdakao-modified supine Valdivia position in 2008, which became increasingly popular worldwide ever since.[37]
Through the reduction in the number of access tracts required, ECIRS improves the one-step resolution of renal calculi. The combination of the two techniques has both therapeutic and diagnostic functions. RIRS typically involves kidney puncture and stone fragment delivery to the Amplatz sheath and permits inspection and irrigation during lithotripsy.[35] ECIRS, a combination of RIRS and PCNL, offers better SFR (OR: 5.14, 95% CI: 2.54–10.4; P < 0.001), offers lower overall or severe complication rates (OR: 0.43, 95% CI: 0.21–0.85; P = 0.02), and requires fewer blood transfusions (OR: 0.33; 95% CI: 0.12–0.91; P = 0.98) compared with those of PCNL alone.[38],[39] Mini-ECIRS can also reduce the risk of postoperative fever and shorten hospital stay compared with those of mini-PCNL.[38] Furthermore, ECIRS and multiple-tract PCNLs offer comparable SFR; the former has the added advantages of reduction in overall complication rates and shorter operating time and hospital stay.[40]
However, this procedure has some limitations. First, the simultaneous use of two endovision systems can be challenging for surgeons, assistants, and nurses in limited-resource settings. Second, despite being a combination of PCNL and RIRS, ECIRS procedures cannot be charged at rates equivalent to a combination of the two procedures individually.[41] Considering Taiwan's National Health Insurance setting, the superior efficacy and safety of ECIRS render it a suitable option for treating complex renal calculi in patients who can afford the procedure.
Treatment for Complicated AnatomySolitary kidney
Patients with solitary kidneys, congenitally or surgically, may exhibit associated physiological changes, such as compensatory renal hypertrophy. In patients undergoing radical nephrectomy, global kidney function decreases by approximately 32.2% while the contralateral kidney function increases by approximately 21.1%.[42] In children with congenital or early acquired single-functioning kidneys, the glomerular filtration rate increases by 100%, preserving the kidney function to levels similar to that of patients with two kidneys.[43] Thus, preserving the remaining kidney function when treating renal calculi is important, and achieving maximum stone clearance with minimal morbidity remains the main treatment goal.
The choice of treatment modality in solitary kidney patients depends on the stone size, with those >2.5 cm being treated using PCNL, those between 1.0 and 2.5 cm being treated with ureteroscopy (URS), and those between 1.0 and 1.5 cm being treated with SWL.[44] PCNL offers better initial SFR compared with that of RIRS when used to treat renal calculi >2 cm; however, it is limited by the prolonged operating time and hospital stay.[44],[45] Higher rates of complications, particularly bleeding events related to the number of urinary tracts created, must also be considered.[44],[46] Although Cui et al. suggested that renal function deterioration may be observed because of urinary tract infections and increased procedure time,[47] other studies have suggested that post-PCNL renal function can be well-preserved in the long term.[45],[46],[48]
After the inclusion of auxiliary procedures, RIRS offers SFR comparable to that of PCNL.[45],[49] However, RIRS can be more time-consuming as it requires a second treatment session, particularly in patients with large stone burdens.[49] It is also associated with a higher risk of steinstrasse[50] and a significantly lower risk of bleeding.[44],[49],[50],[51]
Multi-session RIRS is associated with complete stone-free status, minimal renal injury or other complications, and decreased operating time. During the selection of the appropriate surgical approach, other factors such as the anatomy, remaining renal function, presence of comorbidities, and patient preference should be considered.
Kidney Transplant
Renal calculi have an overall incidence rate of approximately 1% in kidney transplant recipients. The mean duration to diagnosis after transplantation is 28 ± 22 months,[52] with calculi detected within 6 months after transplantation being considered native to the donor kidney.[53] Calcium-based stones are the most commonly observed, followed by struvite stones which are associated with a higher risk of infection and may require intervention.[52] The distal ureter (49.01%), lower calyx (17.6%), and renal pelvis (7.8%) are the most commonly affected sites.[54] These patients rarely present with renal colic due to renal denervation, and more than 40% of cases are diagnosed incidentally.[54] Other clinical symptoms include hematuria (23.5%), acute renal failure (23.5%), and urinary tract infections (5.9%).[54]
Minimally invasive interventions such as extracorporeal SWL (ESWL) (43.1%), active surveillance (25.4%), retrograde URS (17.6%), antegrade URS (3.9%), and PCNL (3.9%) are typically favored to retain maximum renal function.[54] Active surveillance is suitable in patients with calculi <0.4 cm,[4] whereas those with calculi <1.5 cm are treated using ESWL. However, the adjacency of the graft to the iliac bone may interfere with the shock waves, necessitating additional RIRS when residual stone fragments are present.[55] PCNL is recommended for patients with calculi >2 cm, although the risk of bowel injury when creating a puncture to access the graft is higher.[56],[57] Mini-PCNL can further minimize parenchymal injury and bleeding complications. URS, especially RIRS, also represents a suitable option, although the neoureteral orifice can be difficult to identify and may require the assistance of semi-rigid ureteroscopes or other devices.[57] Santillán et al. performed mini-ECIRS to treat patients with en bloc kidney transplantations[58] and suggested that the procedure allowed for complete removal of the stone in one stage while also requiring a lower number of percutaneous tracts, resulting in a decreased bleeding risk and lower intrarenal pressure.
Patients receiving kidney transplants not only have a solitary kidney but also exhibit altered anatomy of the graft and ureter. Thus, the pursuit of maintaining the maximum renal function while minimizing surgical harm to the graft is crucial. The characteristics of the calculi should be carefully considered, and the patient's physical status, including transplant function, coagulation status, and anatomical obstacles due to graft position, should be evaluated when developing individual surgical plans.
Conclusion and DiscussionUrologists are compelled to ask themselves whether the perfect solution for large and complex renal calculi has been developed when faced with such cases. Although following guidelines and performing PCNL is acceptable, reconsideration may be necessary in some situations.
One of the most concerning complications of PCNL is increased risk of bleeding, and this can be improved using mini-PCNL, which can minimize the access tract size used; however, this may compromise stone clearance. To improve SFR efficacy, multiple-tract PCNL may be considered, as it avoids torquing of the nephroscope, thus reducing blood loss. However, higher rates of pulmonary complications and risk of renal parenchymal injury should be considered. In addition to these techniques, which allow percutaneous removal of the renal calculi, less invasive and more flexible interventions, such as RIRS, may be considered for renal calculi <2 cm. However, inferior SFR and the increased infection rate as operative time increases are the biggest concerns when treating larger calculi using this method. Staged RIRS can offer comparable SFR to that of PCNL while minimizing complication rates. ECIRS, which combines both techniques, can yield even better SFR and lower risk of complications. However, the need for two endovision systems, increased manpower, and higher associated costs are among its limitations. The related data are summarized in [Table 1].
Complex renal calculi include large stones or those with anatomical or functional variations. This review also elucidates on patients with solitary kidneys and kidney transplant recipients, who have a single kidney with anatomical alterations, as these may be considered challenging cases when developing treatment strategies for renal calculi. These patients should be carefully examined through preoperative imaging, and a thorough assessment should be conducted to evaluate comorbidities. Although the preservation of residual renal function is the main goal, selection of the best treatment option based on stone size and location while balancing the efficacy of clearance and reducing complication risks is also crucial. In patients with solitary kidneys, minimizing urinary tract infection and operating time is also beneficial.
Tailored treatment plans should be developed and employed for each patient. Therefore, although there is no single treatment approach that is perfect for large and complex renal calculi, careful consideration of all possible options will lead to treatment success.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
Financial support and sponsorship
Nil.
Conflicts of interest
Prof. Tai-Lung Cha, Prof. Guang-Huan Sun and Prof. Dah-Shyong Yu, the editorial board members at Urological Science, had no roles in the peer review process of or decision to publish this article. The other authors declared no conflicts of interest in writing this paper.
References
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