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Keywords:

  • nephrolithiasis;
  • flexible ureteroscopy;
  • renal and proximal ureteral calculi

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

Study Type – Therapy (case series)

Level of Evidence 4

What's known on the subject? and What does the study add?

Large upper tract urinary calculi, greater than 2 cm, have historically been treated with percutaneous nephrostolithotomy. In general, there has been a growing interest in employing retrograde, flexible ureteroscopy and laser lithotripsy in select patients who are either poor medical candidates for percutaneous lithotripsy or who may prefer a less invasive intervention. Properly selecting patients for this approach, designing specific treatments based on complex stone presentation and offering general information with regard to long-term outcomes and surgical risks have historically been based on results from small, multicentre series lacking uniformity of technique and long-term outcomes.

Our initial multicentre experience employing ureteroscopic techniques to treat large upper urinary tract calculi was presented in 1998. This current work represented the largest single-centre experience, accrued prospectively over 10 years, where there was uniformity of technique and treatment algorithms. This study frames an argument for retrograde ureteroscopic lithotripsy not only in those who are at high risk for percutaneous nephrostolithotomy but in all who present with large, non-infected stone burdens.

OBJECTIVE

  • • 
    To define the safety and efficacy of retrograde ureteroscopic lithotripsy in treating large, non-infectious intrarenal and proximal ureteral stone burdens.

PATIENTS AND METHODS

  • • 
    Between 2000 and 2011, 145 patients with 164 large (2 cm or greater in diameter on standard imaging) non-infectious upper intrarenal and proximal ureteral calculi were chosen for retrograde ureteroscopic lithotripsy.
  • • 
    Patients were treated with small diameter flexible fibre-optic ureteroscopes and holmium laser lithotripsy by a single surgeon.
  • • 
    Second-look ureteroscopy was performed in patients with the largest calculi in whom there was a high index of suspicion of significant residual fragments.
  • • 
    Stone clearance was defined as no fragments or a single fragment less than or equal to 4 mm in diameter on standard radiograph and sonography at 3-month follow-up.

RESULTS

  • • 
    Our study included 103 male patients and 42 female patients with an average age of 55 years (range 16–86 years) and a mean stone diameter of 29 mm (range 20–70 mm) including 36 partial staghorn stone burdens (mean diameter 37 mm). Overall, 266 ureteroscopies were performed on 164 stone burdens (1.6 procedures per stone burden), clearing 143 stone burdens (87%).
  • • 
    The highest clearance rates were observed for proximal ureteral (97%) and renal pelvic (94%) stones, while the lowest clearance rates were observed for lower pole (83%) and staghorn calculi (81%).
  • • 
    Three patients required subsequent percutaneous therapy due to infectious material encountered at the time of ureteroscopy or inaccessible stone burdens secondary to infundibular stenosis.
  • • 
    There were five minor postoperative complications, including four fevers and one patient with gross haematuria and clot retention, with no major intraoperative complications.

CONCLUSIONS

  • • 
    In select patients, large, complex, metabolic upper urinary tract calculi can be treated safely and efficiently with retrograde ureteroscopic techniques.
  • • 
    Staged, retrograde, flexible ureteroscopy is an alternative to percutaneous therapy with acceptable efficacy and low morbidity.

Abbreviation
PCNL

percutaneous nephrostolithotomy

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

Large upper tract urinary calculi are commonly associated with obstruction and infection and may lead to renal loss, sepsis and death if left untreated [1]. Large stone burdens (>2 cm) are typically treated by percutaneous nephrostolithotomy (PCNL), with percutaneous access to the collecting system and concurrent antegrade endoscopic fragmentation and evacuation of stone and debris. However, some patients are poor medical candidates for percutaneous lithotripsy, while others may prefer less invasive procedures.

Over the last two decades, retrograde ureteroscopy has been applied to large upper tract calculi, made possible by improvements in ureteroscope flexibility, miniaturization of the endoscope and accessory equipment, and refinements in technique. Herein, we define the safety and efficacy of our retrograde endoscopic technique for treating large (>2 cm), non-infectious renal and proximal ureteral stones.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

All patients treated between January 2000 and December 2011 with large upper urinary tract non-infectious calculi, a major diameter on standard imaging of 2 cm or greater and a proximal ureteral or renal location were eligible for the study. Patients with multiple renal or proximal ureteral stones were included only if the largest single stone diameter was 2 cm or greater (e.g. patients with an aggregate volume greater than 2 cm of multiple smaller stones were not included). Data were collected prospectively and entered into an existing, institutional review board approved stone database. Prior unsuccessful treatment with extracorporeal shock wave lithotripsy, endoscopic or percutaneous therapy did not preclude entry into the study. All patients were offered standard therapy with PCNL if medically fit to tolerate a percutaneous procedure. However, many patients were poor candidates for percutaneous procedures and were specifically referred for retrograde endoscopic therapy.

A preoperative urine culture was obtained for all patients. Patients with refractory infections or a high index of suspicion for struvite calculi were not offered ureteroscopic therapy. If pyonephrosis or infectious material was encountered at the time of initial diagnostic ureteroscopy, patients were drained and not treated in a retrograde fashion.

All stones were treated with a small diameter (8.2 F shaft) fibre-optic based, actively deflectable, flexible ureteropyeloscope. The upper tract access technique has been previously described, and commonly was based on direct endoscope placement, frequently without intramural ureteral dilatation [2]. Operative sheaths were not employed, and bladder drainage was maintained with a small calibre 14 F Foley catheter placed beside the flexible ureteroscope. All procedures were performed by a single surgeon (MG).

The holmium:YAG laser was employed exclusively as the endoscopic lithotrite. The 365-µm laser fibre was used for all but the most dependent lower pole calculi. Laser energy and frequency of pulsation were varied based on stone density and volume. Higher settings were employed initially to convert the stone centre to fine dust and small fragments. Once the residual mass became mobile, the settings were decreased to minimize kinetic forces and emphasize mechanical fragmentation. The end result of this intervention converted the stone burden into fine dust and small passable fragments (<3 mm). Representative fragments were extracted for crystallographic analysis with a stone-grasping accessory. Larger calibre (typically 8 F in diameter) ureteral stents were placed if technically feasible for 10–14 days to facilitate passive ureteral dilatation.

In patients with the largest stones, in whom there was a high index of suspicion of significant residual calculi after the initial procedure, second-look ureteroscopy was performed. Two protocols were employed. An interval of 1 to 2 weeks was used in those who wanted solely outpatient therapy. In other patients who wanted both procedures within a short period (typically patients not from our geographical area who wished expedited care), the interval between procedures varied from 36 to 72 h. In these select patients with the largest calculi, we employed retrograde intrarenal irrigation to clear created dust and debris between interval-staged ureteroscopic lithotripsy. Intrarenal irrigation inflow was performed through a 5 F Cobra catheter with the distal tip positioned in the lower pole, while outflow was maintained with either a 6 or 8 F single pigtail catheter placed cephalad (Fig. 1). Irrigant depended on stone composition, with alkalinizing agents employed most commonly (Table 1). Irrigation began at a rate of 50 mL/h and was raised to 100 mL/h based on patient tolerance. Broad spectrum parenteral antibiotics were used prophylactically during retrograde irrigation. Clinical parameters of fever, flank pain, nausea or emesis led to cessation of irrigation and reassessment.

image

Figure 1. Between staged ureteroscopic lithotripsy sessions, retrograde catheters are employed for topical therapy to clear stone dust. Inflow is performed through a 5 F Cobra catheter with its tip in a dependent lower pole location, where debris tends to collect. Outflow is obtained through a 6 or 8 F single pigtail catheter positioned in a superior calyx.

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Table 1. Irrigant choice for intrarenal irrigation
Stone typeIrrigant choiceNo. of patients, n = 45 (%)
  • *

    THAM-E is pH 10 tromethamine tris-hydroxymethyl aminomethane; Mucomyst is N-acetylcysteine.

CystineTHAM-E and Mucomyst*17 (38)
Uric acidTHAM-E23 (51)
Calcium-basedSaline and gentamicin5 (11)

Stone clearance was defined as no fragments or a single fragment less than or equal to 4 mm on standard radiograph and sonography at the 3-month follow-up.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

Our 145 patients (103 male patients and 42 female patients) presented with 164 large upper urinary tract stones. Mean patient age was 55 years (range 16 to 86). Indications for retrograde ureteroscopic lithotripsy are listed in Table 2.

Table 2. Surgical indications for retrograde ureteroscopic treatment of large upper urinary tract calculi
IndicationNo. of patients (%)*
  • *

    Percentage does not add to 100 due to rounding.

Chronic anticoagulation9 (6)
Morbid obesity8 (6)
Severe kyphoscoliosis, renal ectopia, solitary kidney7 (5)
Hypermetabolic syndrome37 (26)
Failed prior percutaneous therapy43 (31)
Complex comorbid conditions11 (8)
Elective30 (21)

Mean overall stone diameter was 29 mm (range 20–70), including 36 partial staghorn stones (mean diameter 37 mm) and 10 bilateral simultaneous stones. There were 131 renal stones (80%) and 32 proximal ureteral stones (20%). Ninety of 164 stone burdens were treated with a second-look endoscopy (55%). Two large staghorn calculi (6 and 7 cm in diameter) required a third-stage ureteroscopy to achieve satisfactory stone fragmentation.

The most common urinary stone composition treated was calcium oxalate, with the monohydrate variety being the major type (53%). In addition, 24% of the stone analysis showed a significant component (>50%) of uric acid, 18% of patients had pure cystine calculi and 5% of patients had calcium phosphate calculi.

Table 3 presents stone clearance rates by location and size. Overall, 256 ureteroscopies were performed (1.6 procedures per stone burden), clearing 143 stone burdens (87%). Highest clearance rates were observed for proximal ureteral stones (97%) and renal pelvic stones (94%), while the lowest clearance rates were observed for lower pole renal calculi (83%) and staghorn calculi (81%). Intrarenal irrigation was employed for 45 (27%) stone burdens, with similar stone clearance rates to those with smaller and more central calculi.

Table 3. Mean stone diameter and stone clearance rates by location
 No.Mean size (mm)Clearance rate (%)
Overall16429143 (87)
Location   
 Renal calculi13130114 (87)
  Partial staghorn363729 (81)
  Upper pole132711 (85)
  Middle pole153214 (93)
  Lower pole362730 (83)
  Renal pelvic322730 (94)
 Proximal ureteral calculi322731 (97)

Three patients required subsequent PCNL due to infectious material encountered at the time of ureteroscopy or inaccessible calculi due to infundibular stenosis. Overall, there were five minor postoperative complications, including four fevers and one patient with gross haematuria and clot retention requiring readmission. There were no major intraoperative complications.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

In 2005, the American Urological Association guidelines established percutaneous therapy as the primary treatment modality for large (>2 cm) and branching calculi, with an overall stone clearance rate of 78% [3]. Absolute indications for PCNL include infectious stone burdens, especially those associated with obstruction of the collecting system. The efficacy of PCNL must be balanced against the more invasive nature and higher risk profile of this procedure compared with ureteropyeloscopic treatment of upper urinary tract calculi. Significant complications associated with PCNL include the risk of blood loss requiring transfusion (range 1–10%), severe haemorrhage requiring angio-embolization and subsequent loss of renal parenchyma (1%), fever/pyelonephritis (3–30%), urinary extravasation (1–5%) and injury to adjacent organs (0–1%) [4,5]. These complications are rarely, if ever, encountered with ureteroscopic therapies [6].

Patient comorbidities, such as uncorrectable coagulopathies, morbid obesity, severe obstructive pulmonary disease or extremity contractures/severe kyphoscoliosis, may render percutaneous treatments challenging and unsafe compared with ureteroscopic treatments. In addition, patients with hypermetabolic syndromes like cystinuria frequently present with impaired renal function often as a result of multiple, prior percutaneous procedures and require subsequent therapies emphasizing parenchymal preservation [7]. Therefore, select patients with large upper tract stones would benefit from an alternative, retrograde treatment modality.

In 1998, we reported the first, multicentre, collaborative effort of treating large complex, upper urinary tract stone burdens ureteroscopically, defining the safety and efficacy of our technique. In that report, three institutions combined to treat 51 patients with 66 large upper urinary tract stone burdens, using staged ureteroscopy in 27% of patients and achieving a stone clearance rate of 93% [8]. Since that time, mechanical improvements in flexible ureteroscopes, such as smaller shaft diameter with increased rigidity, improved optics and miniaturization of accessory equipment, have facilitated a growing experience with the retrograde treatment of upper tract stones.

In the present study, we present the largest single-institution series of retrograde intrarenal endoscopic lithotripsy for complex, large, upper urinary tract stone burdens. Patients were treated by a single surgeon, ensuring a uniform treatment algorithm and operative technique, and follow-up data were obtained prospectively. The patients treated in our series were particularly complex, referred to our practice mostly because medical comorbidities prohibited safe percutaneous treatment or because they had failed percutaneous treatment elsewhere. Elective desire to avoid PCNL was an indication in only 21% of patients.

All patients were counselled preoperatively about the possibility of staged ureteroscopic therapy. Technical limitations of ureteropyeloscopic treatment for large stone burdens are that endoscopic lithotripsy creates significant stone dust and debris, which coats the urothelium and may hide larger, unpassable stone fragments. Furthermore, endoscopic lithotripsy becomes challenging when the urothelium is coated with dust, limiting visualization and increasing the chance of bleeding and perforation. In these patients, interim intrarenal irrigation was helpful in clearing dust and debris, improving visualization during second-look ureteroscopy. We liberally employed staged ureteroscopy, performing it in over half of our patients (55%). In this regard, retrograde and percutaneous treatments of large renal and proximal ureteral stones are similar, in that multiple stages are frequently required to achieve higher stone clearance rates.

Several groups have reported their experience with ureteroscopic management of renal stones larger than 2 cm. In 2009, Riley et al.[9] performed staged, retrograde ureteroscopy on 22 patients with renal stones with an average diameter of 3 cm, excluding those with complete staghorn calculi. An overall stone-free rate of 91% was achieved, with two conversions to PCNL for large lower pole stone burdens. Two major postoperative complications occurred, one episode of sepsis and one subcapsular renal haematoma. Hyams et al.[10] performed a multi-institutional review of 120 patients treated with flexible ureteropyeloscopy for renal stones 2–3 cm in diameter, achieving an 83% stone clearance rate with single-stage ureteroscopy. There were eight minor postoperative complications (6.7%) and one major intraoperative complication (ureteral perforation). The most complex stone burdens, i.e. large branched calculi, were excluded from both these studies.

In contrast, having a large branched renal calculus (i.e. partial or complete staghorn stone burden) did not preclude entry into our study. In all, 22% of our patients presented with staghorn stones. Our overall stone clearance rate of 87% compares favourably with other series of retrograde endoscopic therapy (Table 4). When stratifying by stone location, we observed the highest clearance rates for proximal ureteral (97%) and renal pelvic (94%) stones. The lowest clearance rates were observed for lower pole renal calculi (83%) and staghorn calculi (81%).

Table 4. Review of studies on ureteroscopic management of upper urinary tract calculi >2 cm
StudyDateNumber of patientsMean stone diameter (mm)Stone free (%)Mean number of proceduresComplications,* number (%)
  • *

    As a percentage of total procedures performed.

Grasso et al.[8]19985124.9931.33 (3)
Riley et al.[9]20092230.0911.84 (10)
Hyams et al.[10]201012024831.28 (6)
El-Anany et al.[11]200130>207713 (10)
Mariani [12]20071633882.44 (10)
Ricchiuti et al.[13]20072330.9741.40 (0)
Breda et al.[14]20081522932.33 (9)
Wheat et al.[15]2009938332.30 (0)
Bader et al.[16]20102429.8921.75 (12)
Takazawa et al.[17]20112031901.43 (5)
Present study201214529871.65 (2)

These results approach the stone-free rates of many PCNL series but with a vastly improved safety profile. Contemporary PCNL series for large and branching calculi describe stone-free rates ranging from 60% to 91% with an overall complication ranging from 10% to 20% [18–20]. Despite vigorous ureteroscopic lithotripsy, often lasting 2 h, there were no intraoperative complications observed in our study. Specifically, infectious complications were few, with four postoperative fevers and no episodes of sepsis. Employing small diameter flexible ureteroscopes allowed for continuous intrarenal drainage around the instrument and facilitated complex endoscopic lithotripsy. These procedures represent the extreme of ureteroscopic intervention, where leaving an access sheath in place for up to 2 h may be associated with prolonged ureteral wall compression and subsequent ureteral stenosis. For this reason, we don't routinely use access sheaths in this setting.

A limitation of the present study is the non-randomized nature of its design. In addition, a single-surgeon, single-centre experience obviously has limitations with regard to reproducibility of our results. Nevertheless, the consecutive accrual of our patients and the uniformity of our treatment algorithm underscores the usefulness of our described technique.

In conclusion, retrograde ureteroscopic therapy is a safe and viable alternative to PCNL in patients with large, complex upper urinary tract stone burdens. Ureteroscopic lithotripsy is facilitated by improved endoscopes and lithotrites able to reduce calculi to fine dust and small fragments. Stone-free rates with staged ureteroscopyeloscopy for large renal and proximal ureteral stones approach rates achieved with PCNL, but with greatly reduced patient morbidity.

ETHICS APPROVAL

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

This study was approved by the ethics board of New York Medical College.

CONFLICT OF INTEREST

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES

There are no conflicts of interest to report. There are no sources of funding to disclose.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. ETHICS APPROVAL
  8. CONFLICT OF INTEREST
  9. REFERENCES