Evaluation of fragmentation with single or multiple pulse setting of Lithoclast for renal calculi during percutaneous nephrolithotripsy and its impact on clearance

Frequency and risk factors for antegrade ureteral stone migration after percutaneous nephrolithotomy

Introduction

Percutaneous nephrolithotomy (PCNL) is the minimally invasive procedure of choice for the treatment of large and/or complex nephrolithiasis. Migration of residual fragments (RFs) into the ureter after PCNL is presumed to be uncommon. However, should associated stone-related events (SREs) occur, ancillary procedures may be required. The objective of this study was to describe the frequency and to analyze predictors of antegrade migration of RFs after PCNL.

Material and methods

A case-control study of patients who underwent PCNL for nephrolithiasis and had a postoperative computed tomography available within 48 hours was performed. Descriptive statistics and logistic regression analysis were carried out.

Results

The final sample included 169 interventions. Mean age was 49 ±13 years, median maximum stone size was 26 (7 to 87) mm and mean stone density was 835 (70 to 2022) Hounsfield Units (HUs). 7.1% of the patients experienced migration of RFs into the ureter after PCNL, of whom 41.6% suffered SREs. Lithotripsy was performed using ultrasonic (67.5%), laser (23.7%), and pneumatic (14.8%) technologies. Univariate analysis found female gender (OR 4.1, p = 0.02) height ≥1.68 m (OR 5.52, p = 0.009), middle (OR 6.71, p = 0.01) and upper (OR 3.59, p = 0.04) caliceal location, staghorn calculi (OR 4.72, p = 0.02), stone area (OR 1.001, p = 0.03), lasertripsy (OR 3.61, p = 0.03) and operative time (OR 1.007, p = 0.02) statistically significant for migration of SFs into the ureter after PCNL. Of these, only height ≥1.68 m (OR 7.17, p = 0.01) and staghorn nephrolithiasis (OR 13.27, p = 0.02) remained independent predictors in the multivariate analysis with an area under the curve of 0.69.

Conclusions

71.% of patients undergoing PCNL had a SF migrating to the ureter. Of these 41% suffered a SRE that required ancilliary interventions. Staghorn nephrolithiasis and ≥1.68 mts of height were found to predict this event.

Prospective randomized controlled trial comparing laser lithotripsy with pneumatic lithotripsy in miniperc for renal calculi

BACKGROUND AND PURPOSE

The energy source used for stone fragmentation is important in miniperc. In this study, we compared the stone fragmentation characteristics and outcomes of laser lithotripsy and pneumatic lithotripsy in miniperc for renal calculi.

PATIENTS AND METHODS

After Institutional Review Board approval, 60 patients undergoing miniperc for renal calculi of 15 to 30 mm were equally randomized to laser and pneumatic lithotripsy groups. Miniperc was performed using 16.5F Karl Storz miniperc sheath and a 12F nephroscope. Laser lithotripsy was performed using a 550-μm laser fiber and 30 W laser with variable settings according to the need. Pneumatic lithotripsy was performed using the EMS Swiss lithoclast. Patient demographics, stone characteristics, intraoperative parameters, and postoperative outcomes were analyzed.

RESULTS

The baseline patient demographics and stone characteristics were similar in both groups. The total operative time (P = 0.433) and fragmentation time (P=0.101) were similar between the groups. The surgeon assessed that the Likert score (1 to 5) for fragmentation was similar in both groups (2.1 ± 0.8 vs 1.9 ± 0.9, P=0.313). Stone migration was lower with the laser (1.3 ± 0.5 vs 1.7 ± 0.8, P=0.043), and fragment removal was easier with the laser (1.1 ± 0.3 vs 1.7 ± 1.1, P=0.011). The need for fragment retrieval using a basket was significantly more in the pneumatic lithotripsy group (10% vs 37%, P=0.002). The hemoglobin drop, complication rates, auxiliary procedures, postoperative pain, and stone clearance rates were similar between the groups (P>0.2).

CONCLUSION

Both laser lithotripsy and pneumatic lithotripsy are equally safe and efficient stone fragmentation modalities in miniperc. Laser lithotripsy is associated with lower stone migration and easier retrieval of the smaller fragments it produces.

Laparoscopic pyelolithotomy versus percutaneous nephrolithotomy for a solitary renal pelvis stone larger than 3 cm: a prospective cohort study

To prospectively compare the outcome of laparoscopic pyelolithotomy (LP) versus percutaneous nephrolithotomy (PCNL) in patients with a solitary renal pelvis stone larger than 30 mm. We analyzed demographic and perioperative parameters and intermediate outcome in 30 adults who underwent transperitoneal LP for solitary renal pelvis stone larger than 30 mm (Group I) and compared the results with 30 patients who underwent PCNL (Group II). The two groups were matched for age, sex and stone size (Group I 35.3 ± 7.33 mm, Group II 36.6 ± 7.0 mm; P = 0.47). Mean operative time was significantly longer in LP group (120.5 ± 39.94 min versus 98.1 ± 23.28 min; P = 0.01, 95 % CI 5.43-39.23). Stone-free rate after LP was significantly higher than after PCNL (100 % versus 76.7 %; P = 0.01). On the discharge day, no residual stone was found in LP group, and significant residual stone (mean size 9.8 mm, range 7-15 mm) was found in seven patients (23.3 %) in PCNL group. After the ancillary procedures, the stone-free rates were 100 % in LP and 96.6 % in PCNL group at the end of follow-up. The average overall treatment cost was significantly lower in LP (683.9 USD versus 815.9 USD; P < 0.001). Mean postoperative decreases in hemoglobin was similar in both groups. Given adequate laparoscopic experience, for patients with a solitary renal pelvis stone larger than 3 cm, LP can be considered as an appropriate second choice to PCNL. It can be a potentially cost-effective treatment option in terms of one-session stone-free rate and postoperative complications. However, the potential benefits of LP need to be weighed against the more invasive nature of this procedure.

Residual fragments after percutaneous nephrolithotomy

Clinically insignificant residual fragments (CIRFs) are described as asymptomatic, noninfectious and nonobstructive stone fragments (≤4 mm) remaining in the urinary system after the last session of any intervention (ESWL, URS or PCNL) for urinary stones. Their insignificance is questionable since CIRFs could eventually become significant, as their presence may result in recurrent stone growth and they may cause pain and infection due to urinary obstruction. They may become the source of persistent infections and a significant portion of the patients will have a stone-related event, requiring auxilliary interventions. CT seems to be the ultimate choice of assessment. Although there is no concensus about the timing, recent data suggests that it may be performed one month after the procedure. However, imaging can be done in the immediate postoperative period, if there are no tubes blurring the assessment. There is some evidence indicating that selective medical therapy may have an impact on decreasing stone formation rates. Retrograde intrarenal surgery, with its minimally invasive nature, seems to be the best way to deal with residual fragments.

The comparison of laparoscopic pyelolithotomy and percutaneous nephrolithotomy in the treatment of solitary large renal pelvic stones

The aim of the study is to investigate whether laparoscopic pyelolithotomy (LPL) could find a place in the management of large renal pelvic stones which are generally considered as excellent indications for percutaneous nephrolithotomy (PNL). Between 2006 and 2009, 26 consecutive patients with large (>4 cm(2)) renal pelvic stones were treated by LPL and their charts were compared to 26 match-paired patients treated with PNL during the same period. The patients were matched for age, BMI, stone size and location as well as presence of congenital anomalies. Perioperative and postoperative findings were compared. The mean age, mean stone size, rate of congenital anomalies, history open renal surgery and shock wave lithotripsy were similar in both groups (p > 0.05). The mean operation time was 138.40 ± 51.19 (range 70-240) min in LPL group as compared to 57.92 ± 21.12 (range 40-110) min in PNL group (p < 0.0001). There was one (3.8%) open conversion in the LPL group due to dense perirenal adhesions making the dissection difficult. The ureteropelvic junction (UPJ) obstruction concomitant to pelvic stones was successfully repaired laparoscopically in two cases. The mean drop in postoperative hemoglobin level was 0.9 ± 0.6 (range 0-2) g/dl in LPL group and 1.7 ± 1.1 (range 0-4) g/dl in PNL group (p = 0.024). Hospitalization was significantly shorter in PNL than LPL group (p = 0.0001). Stone-free rates were similar. Laparoscopic pyelolithotomy is associated with a longer operation time, is more invasive, and requires more skills when compared to PNL. However, LPL is associated with less blood loss. Laparoscopic pyelolithotomy is indicated for congenitally anomalous kidneys and especially in patients with concomitant UPJ.

Clinically insignificant residual fragments after percutaneous nephrolithotomy: medium-term follow-up

BACKGROUND AND PURPOSE

Clinically insignificant residual fragments (CIRFs), defined as asymptomatic, noninfectious, ≤4  mm fragments, are sometimes observed after percutaneous nephrolithotomy (PCNL). Because the natural history of these fragments is unclear, we investigated the medium-term outcome of these fragments.

PATIENTS AND METHODS

During a 3-year period, 430 patients underwent PCNL. Overall stone-free rate was 74.5%, and CIRFs were encountered in 22% of cases 3 months after surgery. A total of 38 patients who had CIRFs immediately after PCNL with at least 24 months of follow-up were included in the study. All patients were subjected to periodic follow-up with detailed history, clinical examination, and radiographic follow-up. Serum biochemistry together with urine metabolic evaluation was also performed.

RESULTS

The median follow-up was 28.4±5.3 months (range 24-38  mos). Ten (26.3%) patients had a symptomatic episode that necessitated medical therapy during follow-up while others remained asymptomatic. Radiologic assessment showed an increase in the size of the fragments in 8 (21.1%) patients, while the size of the fragments was stable or decreased in 27 (71.1%) cases. Three (7.9%) patients had spontaneous stone passage. Metabolic evaluation revealed abnormalities in 10 (26.3%) patients. Stone analysis revealed magnesium ammonium phosphate in three of eight patients who had an increase in residual fragment size. Also, only two of these eight patients had a metabolic abnormality (one hypocitraturia and one hypercalciuria).

CONCLUSION

Medium-term follow-up of CIRFs after PCNL revealed that progression within 2 years is relatively common. Increase in fragment size is common in patients with struvite stones, and presence of risk factors on 24-hour urine metabolic analysis does not seem to predict growth of observed fragments.

Diagnosis and management of postpercutaneous nephrolithotomy residual stone fragments

Residual stone fragments can occur in up to 8% of patients who are treated with percutaneous nephrolithotomy (PCNL). When left untreated, approximately half of these patients will experience a stone-related event, for which more than half will need a secondary surgical intervention. Predictors of adverse events are a residual fragment larger than 2 mm that is located in the pelvis or ureter. Preventive measures for the creation of residual fragments include a carefully selected access giving exposure to the bulk of the stone, the creation of multiple tracts, the use of single pulse pneumatic lithotripsy, the prevention of stone migration with ureteral balloons or stone cones, and careful flushing of the stones from the collecting system. Plain radiography of the kidneys, ureters, and bladder, linear tomography, and ultrasonography have all been used to judge the result of PCNL and to detect the presence of residual fragments. Thin-slice, unenhanced helical CT, however, is more sensitive and should be performed at 1 month after surgery. While medical therapy and shockwave lithotripsy possess a minor role, second-look flexible nephroscopy and/or flexible ureterorenoscopy seem to be the treatments of choice for residual stone fragments after PCNL.

Evidence-based choice of pneumatic lithotripsy probe diameter using an improvised in vitro biomodel

PURPOSE

Over the past few years of experience at our center, we had perceived a difference in stone fragmentation capability between two probe diameters available for transurethral pneumatic lithotripsy. We designed and utilized a novel in vitro biomodel to test this hypothesis.

MATERIALS AND METHODS

Twenty 15-cm-long pieces of avian gut were refashioned and fixed at the two ends in a standardized manner to imitate the natural human ureter and its convolutions as closely as possible. Five-millimeter phantom stones placed at the proximal 5-cm point of each ureter were fragmented by pneumatic lithotripsy through a semirigid ureteroscope in four study groups: Group I, using a 1.6-mm probe at 12 Hz; group II, using the 1.6-mm probe at 6 Hz; group III using a 0.8-mm probe at 12 Hz; and group IV using the 0.8-mm probe at 6 Hz.

RESULTS

Fragmentation required 272 +/- 57 pulses on the 1.6-mm probe, versus 853 +/- 85 using the 0.8-mm probe (P < 0.005). The 1.6-mm probe was similarly effective at 6 and 12 Hz (P = 0.08), while for the 0.8-mm probe 6-Hz pulse frequency entailed far fewer pulses to achieve the objective (P < 0.005). The 1.6-mm probe had uniformly higher efficacy compared to 0.8 mm at both 6 and 12 Hz (P < 0.005).

CONCLUSION

The 1.6-mm pneumatic lithotripsy probe has consistently higher efficacy compared to 0.8 mm throughout both frequency ranges. Our biomodel is introduced as a suitable low-cost and readily available in vitro medium for comparing intracorporeal lithotripsy modalities.

Management of stones in patients with anomalously sited kidneys

PURPOSE OF REVIEW

Congenital abnormities in urology are very common. Horseshoe, malrotated and ectopic kidneys, as well as duplex systems, are the most frequent in this respect. The combination of both abnormalities and stones is of clinical importance. The question is asked if standard procedures for stones apply also to stones in abnormal kidneys.

RECENT FINDINGS

In general, open surgery, extracorporeal shock-wave lithotripsy, percutaneous procedures, endoscopic procedures and laparoscopy are possible procedures in both normal and abnormal kidneys. The importance of ureteric pelvic junction obstruction has to be taken into account and a metabolic work-up remains important.

SUMMARY

The trend for treatment of stones in abnormal kidneys goes towards endoscopical and laparoscopical procedures, whereas a combination of both seems to be appropriate in many cases.