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  • Percutaneous Nephrolithotomy (PCNL): Kidney Stones

    About the authors: Jed-Sian Cheng, MD/MPH MD and Oleg Shapiro, MD

    Oleg Shapiro, MD

    Dr. Oleg Shapiro completed his medical education and residency at SUNY Upstate Medical University, Syracuse, NY where he stayed on as staff. His primary focus is the treatment of urologic cancers and stone disease.

    Link to Dr. Shapiro’s website page at Upstate Medical University

    Dr. Jed-Sian Cheng, urologybook.com

    Jed-Sian Cheng, MD/MPH was born in Taiwan and immigrated to America before age 3.  He grew up outside of Boston, MA and attended the Middlesex School.   His undergraduate education was at Cornell University and attended the University of Texas Health Science Center-Houston Medical School where he earned his MD and MPH.  He is currently a chief resident at State University of New York-Upstate and will be going to Harvard/Massachusetts General Hospital for a Society of Urologic Oncology fellowship.

    Introduction:

    Percutaneous access of the kidney was first described in 1955 (Goodwin et al.) in a case requiring relief of an obstructed kidney.  In 1976, the percutaneous access was used to remove kidney stones as described by Fernström and Johansson, and thus the birth of PCNL.

    Indications:

    PCNL is most commonly indicated for large stone burden.  This is defined by the following:

    • Staghorn calculi
    • Stone >2cm
    • Multiple stones >1cm
    • Proximal ureteral stone >1cm

    PCNL should also be considered for difficult to treat stones:

    • Lower pole stones >1cm
    • Calcium oxalate monohydrate and cystine stones
    • Stones refractory to other treatments
    • Stones in calyceal diverticulum
    • Stones with UPJ obstruction or poor drainage like horseshoe kidneys

    Contraindications:

    Absolute contraindications include active infection, coagulopathy, pregnancy, and unsafe access. Active infection may result in acute sepsis during or after the procedure.  Coagulopathy needs to be corrected prior to surgery as hemorrhage is a well known risk for the procedure.  A PCNL is not safe for pregnancy and temporizing measures such as stenting or nephrostomy tube should be considered until the post partum period.  If the access is suspicious for possibly injuring or perforating surrounding organs, then the PCNL should not proceed.

    The relative contraindications include pulmonary or cardiac disease, and morbid obesity.  Pulmonary and cardiac assessment is especially important if the patient is placed prone as there is extra stress on the cardiopulmonary system. Moreover, in the prone position, the ability to access the airway is hindered.  The patient would usually need to be repositioned supine in any emergency.  Morbid obesity is another relative contraindication as the access tract may be longer than the standard instruments available.  Some companies make extra long instruments for this patient population.

    Special Anatomy Considerations:

    Approaches and incision site is based on the best access to renal collecting system.  Access should be through the parenchyma of the kidney into a calyx.  One should not use an access that is through the renal pelvis.  Generally, the access is through a lower or middle pole calyx.

    Occasionally upper pole access is needed due to anatomy and stone location.  There is an increased risk of puncturing the diaphragm causing a pneumothorax or hydrothorax in these cases.  Post procedure fluoroscopy of the chest or a upright chest radiograph is recommended.  A chest tube may be needed if patient is symptomatic.

    Horseshoe kidneys have a few anatomic anatomic findings.  These kidneys are generally lower than normal kidneys as developmental ascent of the kidneys is inhibited by the fused lower poles trapped by inferior mesenteric artery.  These kidney are also malrotated with the renal pelvis pointing anteriorly.  This confirmation results in a lower and more medial incision for access of the kidneys.  Since the inferior mesenteric artery lies over the fused lower pole, be aware that too much force against the kidney with a rigid scope may result in injury to the artery.  Finally, the ureters insert high into the renal pelvis and sometimes there is a level of mild obstruction.

    During fetal development, the kidney ascends from the pelvis to the normal anatomic position.  A kidney can be found anywhere along the path of ascent.  An ectopic kidney does not exclude the patient from having a PCNL.  However, special consideration is needed for deciding patient positioning and site of access.  Different approaches have been described and an upper pole access in a pelvic kidney may be the only access obtainable.  These cases require special thought planning.

    A malrotated kidney will change the location of the access site.  In most cases, a safe access can be obtained.  However, in some cases, the pelvis is rotated lateral and posterior and the calyces may be difficult to access due to the spine (in a prone approach) or bowel (in a supine or flank approach).

    A transplant kidney is usually found in the peritoneal cavity in the pelvis.  There have been different approaches to access these kidneys.  They have included laparoscopic assisted PCNL approach to transperitoneal ultrasound guided access.  In these cases it is important to remember that the patient is immune suppressed and risk for infection is elevated.

    Patient Position and Special Instruments:

    PCNL is classically performed in the prone position but other positions have been described.    Other positions include supine, semi-supine, flank, and modified flank. In the classic prone position, the patient is placed on either two rolls (rolled up blankets or jelly rolls) or a bump placed at the abdomen.  The goal of these rolls are to cause a decrease the lumbar curvature and keep the buttocks away from the working space.

    Instruments:

    Guidewires: a superstiff or ultrastiff wire and another guidewire of surgeon’s preference

    C-arm/fluoroscopy

    Amplatz dilators or nephromax balloon dilator

    Irrigation and endoscopic tower

    Nephroscope

    Flexible cystoscope

    Flexible ureteroscope

    Stone graspers, stone basket, and stone laser

    Lithotripsy device: EHL, pneumatic, sonic, laser, or other

    JJ stent

    Nephrostomy tube

    Contrast

    Ureteral/Pollack catheter

    Kaye tamponade ballon catheter

    Surgical Steps:

    *Some urologists acquire their own access.  This is usually done by first placing a Pollack catheter in the ureter of interest prior to turning the patient prone.  Once the patient is prone, the Pollack catheter can be injected with air and/or contrast to help delineate the renal pelvis.  Many institutions rely on interventional radiology (IR) for nephroureteral access.  In the video provided, our access was gained by IR and they left two nephroureteral wires in place.

    Prior to placing the patient prone, a Foley catheter is placed.  The catheter allows decompression of the bladder during the surgery as irrigation from the kidney will drain antegrade.  The patient is then positioned prone on a bump.  The arms are placed outward and forward in a 90 degree angle.  Axillary rolls need to be placed to prevent a brachial plexus injury.  If a long surgery is anticipated, warm irrigation should be prepared and also body warmer is recommended.

    In the video presented, renal access was already obtained by IR.  We use a method of boxing out the surgical site using 10x10s prior to prepping the patient.  We believe that this reduces the exposure of the patient to cold irrigation and causing hypothermia.  The tubes and the site is then prepped and dried. A small cut is made in the middle of the adhesive PCNL drape and the prepped nephroureteral tubes are passed through the drape.

    Once the patient is draped and equipment has been checked and found to be in working order, The C-arm is brought in and a scout film is taken.  A superstiff wire and a safety wire is then passed down the nephroureteral tubes and into the bladder.  Once the wires are in place, the tubes are push pulled out.

    An Incision is then made with an  11 blade.  This incision is made between the wires and big enough to pass a pinky finger into the fat.  Care is taken not to leave any skin bridges by the wires as it will make passing instruments over the wire difficult.

    The tract is dilated over a superstiff wire.  This is done using a nephromax balloon over the superstiff wire.  Only a superstiff or ultrastiff wire provides the necessary rigidity  for dilatation.  Of note, the balloon should not be pre-tested as it is specially packaged for insertion into the tract.  The indicator for tip of balloon is then passed under fluoroscopy until the marking is in the pelvis.   The tract is then dilated to 12 atmospheres (ATM) of contrast in the balloon.  Fluoroscopy is used to confirm if the tract is evenly dilated and smooth.  The balloon is then partially deflated to 10 ATM and an access sheath is passed over the balloon into the kidney.  Live fluoroscopy is used to ensure that the sheath is passed properly.  Once the sheath is in the kidney, the balloon is then deflated and removed.  Alternatively the tract can be dilated with Amplatz sequential dilators, however literature suggests that more trauma and bleeding are associated with the Amplatz.

    At this time the nephroscope can be passed through the sheath to visualize the collecting system.  Irrigation is put on pressure to maintain good visibility.  Clots may be seen in the sheath and can be removed by rigid graspers.  The collecting system can then be visualized and the stones identified.  Small stones can be pulled out by rigid graspers and larger stones may require a lithotripsy device.  In our case we use a Lithoclast which uses both a sonic and pneumatic device.  Caution is necessary when using the pneumatic device as holes can be made in the collecting system kidney.  The suction at the tip of a sonic device can also remove mucosa.

    If a stent is already present, it is our preference to leave it during the stone breaking.  This will keep larger stone fragments from migrating down the ureter.  If during the procedure the stent is in the way of stone clearance we would then remove it.  Nephrostomy tubes are generally removed once good access to the collecting system is gained.

    The rigid nephroscope may not be able to access all the stones and stone fragments may migrate into a calyx.  Once all the stones that can be visualized by the nephroscope are cleared, a flexible cystoscope is introduced to view all the other calyces and remove stones with a stone basket. Fluroscopy can be used to identify calyces that contain stones and a nephrostogram can be considered in complex collecting systems.  A holmium laser and stone basket are sometimes needed for removing large calyceal stones.

    Large ureteral stones and stone fragments can be extracted in an antegrade fashion with a flexible ureteroscope.  Small stones <4mm will likely pass.  The ureteroscope may also be used to enter calyx with tight infundibulum.

    At the end of the procedure there are some considerations as to what stents or tubes should be left.  If there is a large amount of stone debris, ureteral injury, or the possible need for a future ureteroscopy, a stent may be left in place.  This is passed through the nephroscope in an antegrade fashion.  An old stent can be exchanged through the nephroscope as well.

    If tubeless PCNL is desired, there are a few options.  If the surgery was pristine and minimal bleeding seen, then no tubes need to be left behind.  If there was some minimal bleeding or trauma, then a JJ stent with a string attached may be left.  The string will come out of the incision and the stent can be pulled out the next morning or in the office by pulling on strings.  Alternatively, a Pollack catheter can be passed and the end be secured to the skin.

    Traditionally a nephrostomy tube is left behind under fluroscopy.  There are a few different options as to what tube is left.  A large bore (26fr) nephroureteral tube, foley catheter, or large malecot may be left through the tract and into the collecting system.  This is generally left if there is significant bleeding or there is a consideration to perform a second look PCNL.  These large tubes should be downsized before complete removal of any tubes.  Alternatively, smaller bore (14fr) nephroureteral tube, foley catheter, or small malecot can be left.  This is generally used for cases with some bleeding but unlikely to need a second look.  The smaller tubes may be removed post operatively and the tract will close.  If using a foley for a nephrostomy tube, care is taken not to overly distend the collecting system by inflating too much into the balloon.  Once the tube is in place, the access sheath may be removed.

    The incision is closed with 2-0 vicryl with a mattress stitch.  A pressure dressing is then placed and the patient is turned supine.  The nephrostomy is left uncapped.  If moderate bleeding is noted, then the nephrostomy tube may be capped and the patient needs to be observed.   If brisk arterial bleeding is noted or the patient becomes unstable, the nephrostomy tube may be changed to a Kaye tamponade balloon catheter.  Supportive measures should be made and IR should be contacted for emergent embolization.

    In recovery, we routinely check a set of labs for electrolytes and blood count.  A chest radiograph should be considered for any upper pole access or if there is a suspicion for pneumothorax or hydrothorax.

    Complications:

    Most common complications of the procedure include hemorrhage, sepsis, ureteral and pelvic injury, penumothorax/hydrothorax, fistula, and injury to organs/access through organs (Liver, spleen, or bowel).  Patients with comorbidities may also develop myocardial infarction, stroke, or deep venous thrombosis.  Below are the results from two large studies recently published (table 1).  One article by the Clinical Research Office of the Endourological Society (CROES)1 which is an international study involving 96 centers and 5803 patients.  The other study is by Soucy et al. reporting on 509 staghorn calculi performed over a 15 year period at one center in Ontario, Canada2.

    CROES (ref 1) Soucy et al. Historical range
    Transfusion 5.7% 0.8% 1-17.5%
    Renal pelvis perforation 3.4% Not reported 4-11.5%
    Hydrothorax 1.8% 1.4% 2.3-3.1%
    Fever >38.5 10.5% Not reported 0.9-4.7%
    Total complications 20.5% Not reported 29-83%

    Table 1. List of complications reported by two recent large studies and reported historical range.

    Outcomes:

    It is agreed that the most important outcome is stone free rate, which is generally quoted as 80-90%.  However, currently there is no standardized method of reporting stone free rates.   As seen below in Table 2, the two recent studies report stone free rates at different intervals.  Many of the residual stones are small and may pass spontaneously.  Therefore a secondary outcome is the need for secondary procedure.  This is usually shockwave, ureteroscopy, or repeat PCNL.  Soucy et al. specifically looked at staghorn calculi and the residual small stones pass and by 3 months.  Therefore the stone free rate is higher at 3 months.

    Some heterogeneity is noted in the two studies as multiple tract accesses, and second look PCNL are included in the data set.  Also in the CROES study, there is variable modes of renal access such as IR vs. surgeon obtained.  Moreover the CROES study does not separate the different stone burdens.  Similar issues arise in the PCNL literature.  There is a belief that PCNL success is independent of stone size.

    CROES Soucy et al.
    Stone free at D/C Not reported 77.8%
    30 day stone free 75.7% Not reported
    90 day stone free Not reported 90.5%
    Without secondary procedure 84.5% 91.0%

    Table 2. Results from two large studies as to their outcomes and how they defined success.

    Final Thoughts and Surgical Pearls:

    • Although PCNL may be done without a safety wire down ureter, it is not recommended.  Safety wire will prove valuable if a renal pelvic injury occurs or when bleeding makes visibility difficult.
    • Consider reimaging patient with large stone burden before removing nephrostomy or stent to ensure no residual stones are present.
    • Post operative chest x-ray is recommended if the upper pole is accessed.  One can also check with the C-arm prior to concluding the case.
    • When possible, use warm irrigation and try to keep patient dry.  Patients can become hypothermic during a PCNL

    References:

    1. de la Rosette J, Assimos D, Desai M, Gutierrez J, Lingeman J, Scarpa R, Tefekli A; CROES PCNL Study Group. The Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study: indications, complications, and outcomes in 5803 patients. J Endourol. 2011 Jan;25(1):11-7.

    2. Soucy F, Ko R, Duvdevani M, Nott L, Denstedt JD, Razvi H. Percutaneous nephrolithotomy for staghorn calculi: a single center’s experience over 15 years. J Endourol. 2009 Oct;23(10):1669-73.

     

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