Can Miniperc replace standard PCNL? : Appraisal of analysis of consecutive 318 patients.
What is the contempory role of miniperc?: Appraisal of analysis of consecutive 318 patients.
Introduction: Percutaneous nephrolithotomy (PCNL) was introduced for treatment of renal stones in 1976 (1). Over the years PCNL has undergone many modifications and improvements. These were aimed at improving the clearance of the stone and towards achieving complete clearance and also at decreasing the complications associated with it. PCNL is the standard of care for renal stones with size > 20mm and a treatment option for stones <20mm (2). Although there is no exact consensus on what should be considered as Miniperc. Miniperc is term generally accepted for PCNL done with tract size less than or equal to 20 Fr(3).Miniperc has been shown to have equal stone free rates and reduced morbidity compared to standard PCNL. As the tract size decreases the blood loss and pain associated with PCNL decreases (4, 5, 6). Miniperc which was earlier used for small burden stones is now also used for higher stone burden. It is a study to evaluate whether miniperc can replace the large tract standard PCNL and what is its contempory role?
Patients and Methods:
It is a retrospective review of 318 patients who underwent Miniperc in urological tertiary hospital from June 2009 to December 2013. Institutional review board and ethics committee approved the study.
Miniperc was defined as PCNL with tract size less than or equal to 20Fr. In our study the largest dimension of stone or cumulative largest dimension of multiple stones is considered as size of stone.
Informed consent was obtained from patients for undergoing procedure. Exclusion criteria for procedure were bleeding tendencies, patients on anticoagulants and pregnancy.Four different surgeons expert in performing PCNL performed miniperc. Procedures were done under general anaesthesia. Patients were initially placed in lithotomy position. Cystoscopy was done with rigid cystoscope and ureteric catheter was placed in the ureter on affected side. Foley catheter was placed per urethrally. Patient was turned prone and the proposed calyx to be punctured was determined. Under ultrasound or fluoroscopy guidance the proposed calyx was punctured. The puncture confirmation was determined by efflux of water from the needle, by placing dye into pelvicalyceal system and turning the fluoroscope into thirty degree position. Once perfect puncture was confirmed then glidewire® (Terumo, Tokyo, Japan) was passed into the pelvicalyceal system. The Miniperc system used was either Wolf (Richard Wolf, Germany) 14 Fr with 20 Fr Amplaz sheath or Storz (Karl Storz, Tuttlingen, Germany) nephroscope 12 Fr with 15/18 Fr sheath or 16.5/19.5 Fr sheath. The tract was dilated over glidewire with 14 Fr Angiotech single step dilator (PBN medicals, Denmark). After that the dilator and sheath of respective Miniperc system was placed. The energy source for stone fragmentation was either laser or pneumatic. Stone fragments were either flushed out from kidney by irrigation through the ureteric catheter or stones were extracted by Nitinol basket or with triflange forceps. Placement of ureteric catheter or double J (DJ) stent with or without nephrostomy tube was decided by surgeons as per the merits of the case. Check X ray of kidney ureter and bladder and ultrasound kidney ureter and bladder was done on first postoperative day for evaluation of clearance of stone. Perurethral catheter with ureteric catheter with or without nephrostomy tube was removed on first postoperative day if procedure was uneventful. The check X ray kidney ureter and bladder and ultrasound kidney ureter and bladder was repeated at one month postoperatively for reconfirming the stone free status.
The data about the demography of the patients, stone size and average Hounsfield unit, stone site, puncture guidance, operative technique, tract size ,nephroscope used, energy source used, exit strategy, total operative time, analgesic requirement (in milligrams of tramadol ) , visual analogue pain score (VAS) at 6 hours and 48 hours, stone free status assessed before discharge and at one month follow up, hospital stay, haemoglobin drop, Clavien – Dindo complication score was analyzed. The outcome parameters of interest were operative time, analgesic requirement, VAS at 6 and 48 hours, haemoglobin drop and hospital stay. We looked at the parameters such as number of tracts, tract size, stone size, stone Hounsfield units, energy source, operative time, exit strategy that could affect the outcome parameters. Univariate analysis of these parameters was done with respect to evaluating the outcome parameters.
The demographic parameters in the study are as depicted in table 1.
Complete clearance was achieved in 314 out of 318 (i.e.98.74%) patients with miniperc.
Table 2 shows the findings of univariate analysis.
There is no significant increase in haemoglobin drop or hospital stay with increasing number of miniperc tracts.
The tract size of 20 Fr Amplaz ( with Wolf 14 Fr nephroscope) or less than that( i.e. Storz 15/18 or 6.5/19.5 with 12 Fr nephroscope) did not significantly affect analgesic requirement, VAS at 6 hours or 48 hours, hospital stay or haemoglobin drop.
Use of laser or lithoclast did not significantly affect total operative time or hospital stay in Miniperc.
As the size of the stone increased, the analgesic requirement and VAS at 6 hours post operatively significantly increased. However size of stone had no impact on VAS at 48 hours, haemoglobin drop or hospital stay.
The Hounsfield units of stone did not affect operative time, haemoglobin drop postoperative VAS scores or analgesic requirement or hospital stay.
As the total operative time increased the haemoglobin drop increased. However it did not affect analgesic requirement, VAS score at 6 hours or 48 hours, hospital stay.
Patients with nephrostomy had more analgesic requirement than tubeless procedures. In the tubeless procedures the analgesic requirement in ureteric catheter drainage group was less than the DJ stent drainage group.
The visual analogue pain score at 6 hours is not influenced by exit strategy.
The VAS at 48 hours is minimum in patients with tubeless procedure with ureteric catheter drainage. It is intermediate in patients with nephrostomy drainage and it is maximum in patients with DJ stent drainage group.
43 out of 112 patients who had DJ stent as exit strategy had significant DJ stent related symptoms.
The exit strategy did not significantly affect haemoglobin drop or hospital stay.
The presence of comorbidities did not affect haemoglobin drop or hospital stay.
Miniperc is associated with similar clearance rate as the standard PCNL but is associated with decreased haemoglobin drop,hospital stay,analgesic requirement and complication rates (3,4,5, 6).However these studies have compared miniperc with standard PCNL for <2cm size renal stones.In our study we have treated 32 patients with more than 2cm size stones.
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The stone free status following PCNL in solitary functioning kidney and bilaterally functioning kidney is 65.4% and 76.1% respectively as per the Clinical Research Ofï¬ce of the Endourological Society (CROES) data(17).The overall stone free status after PCNL was 75.7% as per the CROES data( 18) It was 82.5% overall in high volume in PCNL centre(19). In our study, complete clearance was achieved in 314 out of 318 (i.e.98.74%) patients with miniperc. Rest of the patients required 2nd stage conventional PCNL for complete clearance. This suggest that the stone free status of miniperc is atleast comparable to standard PCNL. This study mainly focuses on whether miniperc can replace conventional large tract PCNL, without affecting the primary goal of stone free status.
CROES data suggest Clavien Dindo complication grades with PCNL were No complication (79.5%), I (11.1%), II (5.3%), IIIa (2.3%), IIIb (1.3%), IVa (0.3%), IVb (0.2%) and V(0.03%) patients.In our miniperc series had no complications in 95.28% patients.Clavien Dindo level 1 complications occurred in 4.4% patients and level 2 complications in 0.31% patients.This suggest that miniperc has lesser complication risk than standard PCNL.
Large renal calculi and staghorn stones often require multiple tract approach for complete clearance of stone with rigid nephroscope or may require use of flexible nephroscope. In standard PCNL multiple tract or single tract with flexible nephroscopy for these complex renal stones did not have significantly different haemoglobin drop or hospital stay (8, 9). In our study we used multiple tract approach in 13 cases of miniperc. There was no significant difference in haemoglobin drop or hospital stay in patients who required single tract miniperc or multiple tract miniperc.
Coming to the issue of stone size, we treated 58 patient with size less than 1 cm,228 patients with size 1-2 cm and 32 patients with size more than 2cm with miniperc. There was no significant increase in haemoglobin drop, VAS at 48 hours and hospital stay between miniperc for these increasing sizes of stones.
These findings suggest that larger size of stones can be safely treated by miniperc and multiple miniperc tract approach may also be safe as and when necessary.Multi- miniperc approach has been used and found suitable for management of staghorn stones which require multiple tracts in children (10) as well as adults (11).
The miniaturisation of PCNL tract is associated with lesser complications and bleeding complication (4, 5, 6).In our study of miniperc the tract size of 15/18, 16.5/19.5,20 Fr did not affect the haemoglobin drop, analgesic requirement, VAS score at 6 hours, 48 hours, hospital stay. So the different miniperc systems by different manufacturers analysed in this study may not transform into clinically different outcomes.In other words different miniperc systems by different manufacturers analysed in this study are equally good.
Coming to issue of hardness of stones and energy sources used, the Hounsfield units of the stone are predictors of the hardness of stone. The outcome of SWL is dependent on the Hounsfield units of the stone (13). Lesser the Hounsfield units softer the stone and more it is amenable to the treatment by SWL. The Holmium laser and pneumatic lithotripters are capable of fragmenting the calculi of all densities efficiently(14). In our study the Hounsfield units of stone did not affect operative time, haemoglobin drop, postoperative VAS scores or analgesic requirement or hospital stay of miniperc. Use of laser or lithoclast in our study did not significantly affect total operative time or hospital stay in Miniperc.
In standard PCNL, as the operative time increased the haemoglobin drop increased (12).In miniperc also as the operative time increased the haemoglobin drop significantly increased (10).In our study also prolonged operative time was associated with increased haemoglobin drop.The prolonged operative time is required for larger and complex staghorn stones. So it is advisable to stage the procedure if prolonged operative time is necessary.Larger and staghorn stones also need multitract PCNL. As multiminiperc is safe option and does not lead to increase haemoglobin drop.So timed staged multiminiperc is the approach ideal for treatment of larger stones. This finding is consistent with findings in earlier publication advising timed staged multiminiperc for complex stones in children(10).
”To place nephrostomy or not “, is always been the discussed and never settled issue. The absolute indications for keeping the nephrostomy tube after PCNL or Miniperc is perforation, bleeding, incomplete clearance which would require secondary procedure, prolonged operative time, severe infection (7,15,16).Exit strategy as tubeless procedure is more likely after miniperc( 6) compared to standard PCNL. Generally a impacted stone or perforation, bleeding ,prolonged operative time are indications of putting DJ stent with nephrostomy and not ureteric catheter only.
In our study only 92 ( 28.93%)patients had nephrostomy tube placed as exit strategy. Patients with nephrostomy had more analgesic requirement than tubeless procedures. In the tubeless procedures the analgesic requirement in ureteric catheter drainage group was less than the DJ stent drainage group. Overall the placement of nephrostomy was cause of pain and placement of DJ caused more analgesic requirement compared only ureteric catheter. The ideal exit scenario would be one where there is no Intraoperative need of placing nephrostomy and the PCNL is exited with tubeless and ureteric catheter only drainage. As miniperc leads to more chances for tubeless procedures as compared to standard PCNL it leads to less analgesic requirement compared to standard PCNL.
The VAS at 6 hours was not significantly different for different exit strategies.
The ureteric catheters and nephrostomy was removed on morning after procedure hence at 48 hours after the procedure the nephrostomy and ureteric catheters were already removed. Whereas the DJ stent was removed 2 weeks after the procedure.DJ stenting causes more VAS at 48 hours as it causes DJ related symptoms.
However the exit strategy did not significantly affect haemoglobin drop related to surgery or hospital stay.
The miniperc is associated with lesser hospital stay compared to standard PCNL(5,6).The hospital stay in standard PCNL was 4.8 to 6.9 days.The size of the stone does not affect the hospital stay in miniperc. In our study the hospital stay in miniperc was only 2.8±1 day.
The presence of comorbidities did not affect haemoglobin drop or hospital stay so the presence of comorbidities was not a confounding factor in these outcomes.
We acknowledge the limitations of these results that it is based on retrospective data,there may be surgeon bias in selection of energy sources,miniperc system or exit strategy.The stone free status was accessed with ultrasound kidney ureter and bladder and X ray kidney ureter and bladder instead of non enhanced CT kidney ureter and bladder.However based on these results further prospective randomised miniperc trials against standard PCNL for larger stones can further substantiate our results.
Our results of this study suggest that miniperc quickens the recovery after PCNL with less haemoglobin drop,more probability of tubeless procedures and less analgesic requirement and lesser hospital stay. Even larger stones >2 cm size can be safely treated with miniperc with outcomes similar to outcomes of standard PCNL in published literature.So Miniperc is safe alternative to standard PCNL for any size of stone.These results need to be further validated by prospective randomised trial of miniperc against standard PCNL for larger renal stones. Hounsefield units of stone don’t affect the miniperc outcome.Both laser and pneumatic lithoclast are equally effective energy souces in miniperc.Different miniperc systems by different manufacturers evaluated in this study are equally effective.Miniperc has ushered in a paradigm shift as regards the exit stragery after PCNL. Majority of cases can be tacked with tubeless approach which lead to less analgesic requirements. In carefully selected patients the best exit strategy would be tubeless procedure with ureteric catheter drainage.
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