Stones: Surgical Modalities for Management of Upper Urinary Tract Calculi

See 2016 AUA Stone Surgery Guideline Notes

See 2015 CUA Ureteral Calculi Guideline Notes

Extracorporeal Shock Wave Lithotripsy (SWL)

• Relatively weak, non-intrusive waves are generated externally and transmitted through the body. The shock waves build to sufficient strength only at the target, where they generate enough force to fragment a stone
• Primary types of shock wave generators (3):
  1. Electrohydraulic (spark gap)
     • Advantages:
       1. Effective in breaking stones
       2. Less pain than electromagnetic because the energy is introduced into the patient's body over a large skin area
       3. Largest focal zone
     • Disadvantages:
       1. Pressure fluctuations from shock to shock
       2. Relatively short electrode life
  2. Electromagnetic
     • Produces either plane or cylindrical shock waves
  3. Piezoelectric
     • Disadvantage:
       • Insufficient power which hampers its ability to effectively break renal stones
  4. Microexplosive generators have been produced but are not commonly used.
• Imaging modalities used by lithotripters (3):
  1. Fluoroscopy
  2. Ultrasound
     • Disadvantages:
       1. Requires a highly trained operator
       2. Poor visualization of ureteric stones
  3. Combination fluoroscopy and US
• Mechanisms for stone comminution (6)
  1. Shear stress
  2. Squeezing-splitting
  3. Acoustic cavitation
  4. Superfocusing
  5. Spall fracture
  6. Dynamic fracture

Contraindications (6)

1. Obstruction distal to stone★
2. Pregnancy
3. Uncorrected coagulopathy or bleeding diathesis
4. Untreated UTI
5. Arterial aneurysm near stone (renal or abdominal aortic aneurysms)
6. Inability to target stone (skeletal malformation)

Technique

• The unmodified Dornier HM3 is considered the gold standard treatment in SWL, other newer machines have not been as successful. These newer machines are downsized, more portable and decrease anesthetic requirements
• Percussion, diuresis, and inversion are safe, well tolerated, and modestly aid in stone passage after SWL

Pre-operative Antibiotic Prophylaxis

• In the absence of a UTI, SWL does not require antimicrobial prophylaxis as no invasive procedure is performed★

Ureteral stenting

• Routine stent placement is not recommended prior to SWL for ureteric calculi★
  • In SWL, stenting prior to treatment has not been shown to improve stone-free rates
    • 2019 AUA Update on Pediatric Urolithiasis: "When [SWL]used for renal stones >20 mm, a ureteral stent should be left in place to aid in stone passage and avoid steinstrasse."

Techniques to optimize outcome (3):

1. A rate of 60 shocks/min breaks stones more effectively and is more protective of kidney vasculature than 120 shocks/min.
   • Increasing the power setting on most electromagnetic lithotripters actually narrows the focal zone, which decreases stone breakage and may also increase the risk for renal injury and renal hematoma.
   • Disadvantage of slower rate is longer treatment times
2. “Ramping up” the energy can be protective of renal injury
3. General anesthesia to reduce stone motion during SWL
   • Patients undergoing SWL with general endotracheal anesthesia experience a significantly greater stone-free outcome than do patients undergoing SWL with alternative anesthetics

Alpha-blockers post-SWL

• May be prescribed post-SWL to improve stone-free rate★

Complications

• Intra/early post-operative
  1. Pain
     • Factors influencing degree of pain during SWL
       1. Type of generator
       2. Power level
       3. Shockwave energy density at the point of skin penetration
       4. Stone location (pain less with ureteral calculi when compared to renal calculi, more with rib-projected stone)
       5. Gender and age (female or young age more likely to require deeper anesthesia)
       6. History of anxiety, depression or prior SWL
       7. Use of topical analgesics, has been used to reduce anesthesia requirements during SWL
  2. Cardiac arrhythmias
     • Usually resolves with cessation of SWL.
  3. Injury to adjacent organ
     • Can occur in a variety of extrarenal tissues such as liver and skeletal muscle
  4. Acute renal injury
     • Shock waves rupture blood vessels and can damage surrounding renal tubules
       • 63-85% of all SWL patients treated with an unmodified Dornier HM3 lithotripter exhibit one or more forms of renal injury within 24 hours of treatment
     • Factors influencing the degree of renal trauma associated with SWL:
       • Aggravating factors (5):
         1. Number of shocks
         2. Period of shock wave administration
            • Shorter period increases damage
         3. Accelerating voltage
            • Higher voltage increases damage
         4. Type of shock wave generator: first vs. second/third generation devices
         5. Age
            • Children and the elderly both appear to be at a greater risk for structural and functional changes after exposure to shockwaves
       • Mitigating factors:
         1. Pre-treatment with 100-500 shocks at low energy level to reduce lesion size
         2. Treatment at a slow rate of shock wave delivery (≤60 shocks/min)
  5. Hematoma
     • Risk factors for post-SWL hematoma (7): TD COACH
       1. Thrombocytopenia
       2. Diabetes mellitus
       3. Coagulopathies
       4. Obesity
       5. Age
       6. Coronary heart disease
       7. Preexisting Hypertension (most likely to increase risk)
     • Most hematomas resolve within weeks and without long-term sequelae, though some hematomas may persist for many months to years
  6. Stent discomfort, if used
• Late post-operative (potential chronic renal changes associated with SWL treatment) (4):
  1. Accelerated rise in blood pressure
  2. Decrease in renal function
  3. Increase in the rate of stone recurrence
  4. Induction of brushite stone disease

Factors negatively affecting SWL success (5):

1. Skin-to-stone distance > 10cm (morbid obesity)
2. Stone attenuation (≥1000HU)
3. Stone composition
   1. Most resistant to SWL (in descending order) (4):
      • Cystine
      • Calcium phosphate (specifically “brushite”)
      • Calcium oxalate monohydrate
      • Matrix
4. Renal anatomic anomalies (horseshoe kidney, calyceal diverticulum)
5. Unfavorable lower pole anatomy (3)
   1. Narrow infundibulopelvic angle
   2. Narrow infundibulum
   3. Long lower pole calyx

• If initial SWL fails, offer endoscopic therapy as the next treatment option.
  • Those who have had partial fragmentation and clearance may be considered for repeat SWL while those with no fragmentation and/or clearance may be selected specifically for endoscopic intervention.

Intracorporeal Lithotripters

• Classification: flexible vs. rigid

Flexible (2): Electrohydraulic lithotripsy (EHL) Laser

Rigid (2): Ballistic Ultrasonic

Flexible

EHL

• Essentially an underwater spark plug
  • Creates a shockwave
    • The shockwave is not focused, unlike in SWL, so the stone must be placed where the shockwave is generated
• Disadvantages (2):
  1. Significant damage to the ureteral mucosa, resulting in ureteral perforation
     • Risk of perforation is greater with higher energies, such as in treatment of a hard stone, and for impacted stones
  2. Retrograde propulsion of calculi and fragments
• Application
  • Should not be activated directly on the basket wires or the guidewire
  • Fiber tip should be positioned 2-5mm distal to the end of the ureteroscope

Laser

• Types of lasers (including those NOT used in stone surgery)
  1. Holmium laser (Ho:YAG)
  2. Nd:YAG
  3. KTP:YAG laser
  4. Thulium
• Urologic applications (3):
  1. Stone fragmentation
  2. Prostate enucleation (Holmium Laser Enucleation of Prostate (HoLEP), Thulium Fiber Laser Enucleation of Prostate (ThuFLEP))
  3. Soft tissue applications (strictures, urothelial tumors)

Holmium laser (Ho:YAG)

• One of the safest, most effective, and most versatile intracorporeal lithotripters
• Advantages (4):
  1. Safer and more efficient than EHL
     • Zone of thermal injury associated with laser ablation ranges from 0.5-1mm, whereas EHL may cause injury to the ureter even when the probe is activated several mm away from the ureteral wall
       • With use of energy levels typically applied for stone disease (<15W), the operator’s cornea would be damaged only if it were at a distance of ≤10cm from the fiber
  2. Reduced retropulsion of the stones or stone fragments compared with EHL or pneumatic lithotrites due to a weak shock wave
     • Settings that will lead to the least amount of retropulsion of a renal pelvis stone are (3):
       1. Decreased pulse energy
       2. Increased frequency
       3. Long pulse width
  3. Can fragment all stones regardless of composition
     • Holmium laser is capable of cutting through metal of a guidewire or basket.
  4. Can transmit its energy through a flexible fiber, which facilitates lithotripsy throughout the entire collecting system.
• Disadvantage of holmium laser (1):
  1. Initial high cost of the device and the cost of the laser fiber
• Operates at a wavelength of 2140 nm in the pulsed mode
  • The long pulse duration produces an elongated cavitation bubble that generates only a weak shock wave
  • Lithotripsy occurs primarily through a photothermal mechanism that causes stone vaporization
• Technique
  • Treatment should begin with low-pulse energy (e.g. 0.6J) and a pulse rate of 6 Hz
    • Pulse frequency should be increased (in preference over increasing energy) as needed to speed fragmentation
  • The laser fiber should extent at least 2 mm beyond the tip of the endoscope to avoid destroying the lens system or the working channel of the endoscope
  • To maximize lithotripsy efficiency, the laser fiber should be moved over the stone surface in a “painting” fashion, vaporizing the stone rather than fragmenting it
  • When a stone is positioned in a renal calyx, firing the laser at high frequency will agitate the stone material, bringing the stone or pieces of the stone into rapid close contact with the tip of the laser fiber – “popcorn technique”.

Nd:YAG

• Depth of penetration: 5-6mm (according to Campbell’s, but varies based on source)
• Wavelength: 1064 nm
• Causes deep coagulative necrosis and considerable thermal tissue injury
• Advantage:
  1. Good for hemostasis
  2. Limited depth of penetration

KTP:YAG laser

• Also called green light laser
• Depth of penetration: about 0.8 mm
• Wavelength: 532 nm
  • Derived from Nd:YAG laser
    • Passing the invisible Nd:YAG beam via a KTP crystal, doubles the frequency and halves the wavelength from 1064 nm to 532 nm.
• Energy is selectively absorbed by haemoglobin, but not by water
• Advantage:
  1. Good for hemostasis
  2. Limited depth of penetration
  3. Because energy of KTP laser is absorbed only by haemoglobin, it is possible to perform operations in non-contact use called photoselective vaporization of tissue.

Thulium

• Typical wavelength of 1940 nm§
• Advantage
  • In-vitro studies demonstrate superior stone ablation rates, compared to Holmium:YAG§
  • Ability to use low pulse energy ensures minimal stone retropulsion§
    • Retropulsion threshold estimated to be 2–4 times higher than that of Holmium:YAG laser.

Rigid

Ballistic

• Relies on energy generated by the movement of a projectile (jackhammer effect).
  • Once the projectile is in contact with another object, the ballistic energy is transferred to the object
• Advantage:
  • Significantly lower risk for ureteral perforation compared with EHL, ultrasonic lithotripsy and laser lithotripsy
• Disadvantage:
  • Relatively high rate of stone propulsion

Ultrasound

• Applies electrical energy to excite a piezoceramic plate in the ultrasound transducer. The plate resonates at a specific frequency and generates ultrasonic waves. Ultrasound energy is transformed into vibrations of the hollow steel probe, which then transmits the energy to the calculus
• Although some heat may develop at the end of the probe during lithotripsy, irrigation can reduce the temperature at the tip of the probe
• Advantage:
  1. Efficient combination of stone fragmentation and simultaneous fragment removal.
     • Fragments <2 mm are aspirated through the hollow lithotrite along with the irrigation fluid
• Disadvantage:
  • Limited use in the ureter due to the rigid nature of ultrasonic probes

Combined ultrasonic and pneumatic devices (e.g. LithoClast, Boston Scientific)

• Combines the superior fragmentation ability of the pneumatic component with the ability of the ultrasonic modality to simultaneously evacuate stone fragments

Historical

Dolbeau technique of perineal lithotomy. Dr. Dolbeau once removed a 53g calculus with this method.§

Source: Wikipedia for further details

Ureteroscopic Lithotriopsy

Ureteric Stones

Technique

• Equipment
  • Semi-rigid vs. flexible ureteroscope
    • Clinicians performing URS for proximal ureteral stones should have a flexible ureteroscope available★
      • Semi-rigid URS above the level of the iliac vessels can cause additional torque on the ureteroscope, placing the ureteroscope itself at risk for damage.
        • If male, the anatomy may not allow a rigid ureteroscope to be easily passed above the iliac vessels, but a flexible ureteroscope usually can be advanced over a guidewire.
        • If female, the entire ureter can be more easily accessed with a rigid ureteroscope
• Mechanism of lithotripsy
  • Should not utilize EHL as the first-line modality for intra-ureteral lithotripsy★
    • The holmium laser can be activated 0.5 mm from the urothelial surface without risk of injury.
    • Due to a larger working area, EHL can safely be used in the kidney during PCNL, but the risk of perforation using this technology is still higher than other modalities. Therefore, care should be taken to avoid activation of the probe near the urothelial surface.
• Pre-operative Antibiotic Prophylaxis
  • AUA Best Practice recommendations for Ureteroscopy, all indications:★
    • Prophylaxis indicated: All cases
      • Antimicrobials of choice:
        • Fluoroquinolone OR
        • 1st/2nd gen. Cephalosporin +/- Aminoglycoside OR
        • 3rd gen. Cephalosporin
          • Alternative antimocribial(s), if required: Aztreonam
• Normal saline must be used as irrigation★
• If ureteral orifice is too narrow to accommodate the ureteroscope, dilation may be accomplished with
  1. Serial dilators
  2. Balloons
  3. Ureteroscope itself
• Complete fragmentation to a size less than that of the safety wire diameter (0.035 inch) should allow passage of all fragments without sequelae
• Ureteral stenting
  • Pre-intervention
    • Routine stent placement is not recommended prior to URS for ureteric calculi★
  • Post-intervention
    • Following URS, stent placement is strongly recommended in (5):★
      1. Ureteric injury during URS
      2. Evidence of ureteral stricture or other anatomical impediments to stone fragment clearance, such as ureteral wall edema
      3. Large stone burden (>1.5 cm)
      4. Anatomically or functionally solitary kidney or renal functional impairment
      5. Those in whom another ipsilateral URS is planned
      • Ureteral stenting may be omitted in patients without any of the features above★
        • Stent placement after uncomplicated URS has also been shown in randomized trials to be unnecessary
      • In general, 3-7 days of stenting is recommended following routine, uncomplicated ureteroscopic stone intervention★
        • The duration of ureteral stenting post-operatively should be minimized in order to reduce stent-related morbidity.
    • α-blockers and anticholinergics therapy may be offered to reduce stent discomfort★
      • Patients should be counseled about the possibility of post-operative stent discomfort
      • Other medications that can be used to alleviate stent discomfort include bladder analgesics for dysuria, non-steroidal anti-inflammatory agents, and narcotic analgesics.
    • Antibiotics at time of stent removal
      • AUA Best Practice recommendations for Cystourethroscopy with minor manipulation, break in mucosal barriers, biopsy, fulguration, etc:★
        • Prophylaxis indicated: uncertain, consider host-related risk factors
          • Antimicrobials of choice:
            • TMP-SMX OR
            • Amoxicillin/clavulin
              • Alternative antimocribial(s), if required: 1st/2nd generation Cephalosporin OR Aminoglycoside +/- Ampicillin OR Aztreonam¥ +/- Ampicillin
          • Duration of therapy: single dose
• Ureteral Access Sheath
  • Advantages (4):
    1. Decreases OR time
    2. Simplifies re-entry of the ureter
    3. Eliminates need for periodic emptying of the patient’s bladder
    4. Higher stone-free rate

Adverse Events

• Intra-operative
  • Risks of general anesthesia
  • Bleeding
  • Infection
  • Ureteral perforation
  • Ureteral avulsion
  • Incomplete removal/need for second procedure
• Early post-operative
  • Infection
  • Possible need for stent and stent pain
• Late post-operative
  • Ureteral stricture

Ureteral Perforation

• When recognized, the procedure should be terminated and a stent placed.
  • Management
    • In general, a stent should be left in place for approximately 4 weeks after injury.
    • In cases of a severe injury, with significant extravasation of fluid, a percutaneous nephrostomy drain also may be necessary.
    • Urinoma can result and may need to be drained.
    • Antibiotics should be given because of the risk of infected urine and abscess formation.
    • Follow-up
      • Subsequent imaging after ureteral stent removal is mandatory to evaluate for proper healing and adequate drainage
• Complete extrusion of a calculus (lost stone)
  • Can occur in the setting of a ureteral perforation
  • Management
    • When an extruded stone is recognized, the procedure should be terminated and a stent placed.
      • In most cases, if the fragment is completely outside the collecting system it can be left in place.
      • Attempts to retrieve the stone may exacerbate the injury and increase the risk for significant irrigant extravasation.
    • Follow-up
      • One of the most serious sequelae is the later development of a ureteral stricture (see below)
    • Patients who have calculus extrusion should undergo postoperative imaging, which will confirm the stone location

Ureteral Avulsion

• Management
  • Immediate placement of a percutaneous nephrostomy drain and a delayed repair

Ureteral Stricture

• Risk factors (3):
  1. Ureteral perforation
  2. Impacted stones
  3. Submucosal stones
     • Submucosal stones are of concern because they can increase the risk for ureteral stricture formation. If submucosal stones are encountered, laser excision followed by ureteral stent placement is recommended
  • Can occur even after an uncomplicated ureteroscopy.
• Diagnosis and Evaluation
  • Although most patients with a stricture will be symptomatic, between 0.4-4% will be entirely asymptomatic
  • Imaging after ureteroscopic instrumentation is recommended by the AUA in all patients to exclude such cases of silent obstruction§

Intrarenal stones

• If feasible, a lower pole stone should be displaced to the renal pelvis or an upper pole calyx with the use of a basket.
  • Advantages:
    1. Facilitates straight passage of the scope, with minimal deflection of the tip, which will simplify laser lithotripsy.
    2. Residual fragments may be more likely to evacuate spontaneously

Percutaneous Nephrolithotomy (PCNL)

Contraindications

• Absolute (1):
  • Untreated UTI
• Relative (2):★
  1. Use of anti-coagulation or anti-platelet therapy that cannot be discontinued
  2. Anatomic derangements (e.g. contractures, flexion deformities) that may preclude positioning for PCNL
• In patients not considered candidates for PCNL, clinicians may offer staged URS

• Patient factors
  • Obesity
    • General anesthesia may be a special concern for obese patients in the prone position because of restricted respiratory capacity that may require higher ventilation pressures intraoperatively.
    • No increase in overall morbidity
  • Anti-coagulation
    • Aspirin and other anti-platelet medications should be discontinued 7 days before the date of surgery.
    • In patients with a higher risk for thrombotic complications, such as those with mechanical heart valves with atrial fibrillation, bridging therapy with low-molecular weight heparin may be necessary. In such instances, heparin should be discontinued 24 hours before the procedure and resumed 24 hours postoperatively, if feasible

Technique

• Pre-operative Antibiotic Prophylaxis
  • AUA Best Practice recommendations for Percutaneous renal surgery, e.g., PCNL:★
    • Prophylaxis indicated: All cases
      • Antimicrobials of choice:
        • 1st/2nd gen. Cephalosporin OR
        • Aminoglycoside and Clindamycin
        • Aminoglycoside and Metronidazole OR
        • Aztreonam and Metronidazole OR
        • OR Aztreonam and Clindamycin
          • Alternative antimocribial(s), if required: Ampicillin/Sulbactam
      • Duration of therapy: ≤24 hours
• Percutaneous Access
  • Preferred point of entry into the collecting system is posteriorly, along the axis of the calyx, through the papilla
    • UP access:
      • Advantages (4):
        1. Facilitates single access for staghorns
           • An UP access allows for treatment of the UP, renal pelvis, and many LP stones using the rigid nephroscope
        2. UP is line with axis of kidney, minimal tourque with rigid instruments
        3. Efficient treatment of high stone volumes
        4. Ability for simultaneous endopyelotomy
      • Disadvantage:
        1. Potential for pleural, liver, splenic injuries
    • LP access
      • Best suited for LP non-staghorn or LP partial staghorn stones
      • Advantages:
        1. Low risk of pleural, liver, splenic injuries
      • Disadvantages:
        1. Longer tract, greater skin to stone distance
        2. Worse access to UPJ
        3. Slightly higher risk of colonic injuries
    • Indications for supracostal puncture
      1. Predominant distribution of stone material is in the upper calyces
      2. Associated UPJ stricture requiring endopyelotomy
      3. Multiple lower pole infundibula and calyces containing stone material or an associated ureteral stone
      4. Staghorn calculi with substantial upper pole stone burden
      5. Horseshoe kidneys
    • Special situations
      • Horseshoe kidney
        • The optimal point of entry is through a posterior calyx, which is typically more medial than normal because of the altered renal axis and rotation associated with the midline fusion.
          • UP calyces
            • More posterior and lateral than the LP calyces, and therefore more away from hilar vessels
            • Often subcostal
            • Preferred route for PCNL access
          • LP calyces
            • Anterior
            • Inaccessible percutaneously in most cases
      • Struvite stones
        • UP is preferred if a single access tract is to be used in treating complex branching stones.
      • Concomitant endopyelotomy
        • A posterior UP calyx puncture, typically through a supracostal approach, aligns the axis of puncture with the UPJ. This allows endopyelotomy with a rigid nephroscope, while exerting minimal torque on the instrument
      • Staghorn
        • Best approached through polar access (not middle pole), UP preferred.
      • Pre-existing nephrostomy tube
        • Patients may have a pre-existing nephrostomy tube (from urgent percutaneous drainage during presentation of obstructing septic stone).
        • A nephrostomy tube site that is into an infundibulum or the renal pelvis should not be dilated due to the risk of hemorrhage, and in these cases a new access site should be used.
  • The hydrophilic glide wire is the preferred initial wire for entering the collecting system, because it is the most flexible and maneuverable wire available.
  • Overadvancement of the dilator/sheath is the most common serious error in access for PCNL and may result in significant trauma to the renal collecting system and/or excessive hemorrhage.
• Normal saline must be used as irrigation★
  • The use of physiologic irrigating solutions is mandatory because PCNL can lead to some absorption of irrigation fluid.
• Flexible nephroscopy should be used during every PCNL★
  • Goal is to survey the entire intrarenal collecting system for residual stone fragments
    • In an RCT, stone-free rate was higher in patients that underwent concomitant flexible endoscopy with rigid nephroscopy during PCNL, compared to without concomitant flexible nephroscopy, 92.5% vs 70%.
• Placement of nephrostomy tube following PCNL
  • “Tubeless” PCNL is a term used to describe the scenario when no nephrostomy tube is inserted at the end of the procedure.
    • Renal drainage can be established with an indwelling or externalized stent, or the patient can be left without a stent.
  • Benefits of inserting nephrostomy tube following PCNL (4):
    1. Promote hemostasis
    2. Allow for re-entry into the collecting system should a secondary procedure be necessary
    3. Aid in healing of the nephrostomy tract
    4. Prevent extravasation of urine
  • Harms of inserting nephrostomy tube following PCNL, compared to "tubeless" (4):
    • Increased postoperative pain with greater narcotic requirements
    • Increased length of hospitalization
  • Indications
    • In patients undergoing uncomplicated PCNL who are presumed stone-free, placement of a nephrostomy tube is optional
      • In the appropriately selected patient, "tubeless" PCNL can result in similar stone-free and complication rates as standard PCNL.
    • The tubeless approach should not be undertaken if there is active hemorrhage or it is likely that another PCNL will be needed to remove residual stones
• Postoperatively, pain is managed with opioid analgesia and anti-inflammatory medication when not contraindicated.
  • A prospective RCT no difference in complications but also no improvement in pain when ketorolac was administered continuously compared to placebo after PCNL

Complications

1. Hemorrhage
2. Sepsis
3. Perforation of the renal pelvis and ureter
4. Venous gas embolism
5. Pneumothorax or pleural effusion
6. Hydrothorax
7. Colon injury
8. Adjacent organ injury (e.g. spleen)
9. Failed access
10. Stent discomfort, if used

Hemorrhage

• The most significant complication of PCNL
  • Transfusion rates <1-10%.
• Risk factors for hemorrhage
  1. Patient characteristics (thrombocytopenia, coagulopathy, etc)
  2. Multiple access sites
  3. Increasing tract size
  4. Tract dilation with methods other than balloon dilation
  5. Renal pelvic perforation
  6. Supracostal access
  7. Prolonged operative time
  8. Greater stone burden
• Sequential steps to manage hemorrhage (5):♣
  1. Place a nephrostomy tube
     • Usually sufficient to control the bleeding since the source of hemorrhage is venous in most cases.
  2. Clamp the nephrostomy tube; may facilitate the tamponade of any bleeding points
  3. Place a Kaye nephrostomy tamponade balloon catheter.
     • The Kaye nephrostomy tube incorporates a low-pressure 12-mm balloon that may be left inflated for prolonged periods to tamponade bleeding from the nephrostomy tract.
     • See Figure
  4. Angiography to identify a possible arteriovenous fistula or false aneurysm.
  5. Partial nephrectomy may be required in the rare event that bleeding cannot be controlled with angiography
• Delayed bleeding after percutaneous nephrolithotomy is most commonly due to an arteriovenous fistula or pseudoaneurysm.
  • The bleeding may occur intermittently either with or without a nephrostomy tube in place and can often be readily controlled with the replacement of the tube; however, definitive management of an arterial bleed is still required. Selective renal arteriogram with transcatheter embolization is the treatment of choice.
    • Bleeding from an arteriovenous fistula or pseudoaneurysm requiring emergency embolization is seen in less than 0.5% of patients.

Sepsis

• Best predictor of post-PCNL urosepsis is stone culture or renal pelvic urine culture results.
• Despite sterile urine, the fragmentation of stones may release preformed bacterial endotoxins and viable bacteria that place the patient at risk for septic complications
  • The presence of unsuspected bacteria within stones may be one of the underlying causes for infectious complications after PCNL
  • ≈1/3 of patients with an indwelling ureteral stent will, despite sterile urine on a preoperative analysis, be colonized with bacteria.
    • Enterococcus and Staphylococcus epidermidis are the most frequent offending organisms colonizing ureteral stents§

Perforation of the renal pelvis and ureter

• Minor perforations
  • Common during PCNL
  • Premature termination of the procedure usually is not necessary when a low-pressure system (e.g., Amplatz sheath) is being used
• Significant perforation
  • Termination of the procedure and nephrostomy drainage are recommended.
• Intraperitoneal extravasation
  • Less common but potentially more serious complication than retroperitoneal extravasation.
  • Results in narrowing of the pulse pressure♣
    • Pulse pressure = systolic - diastolic blood pressure
    • Intraperitoneal extravasation increases abdominal pressure leading to decreased venous return, and thus, narrowing the pulse pressure.
    • Narrowed pulse pressures (rise in diastolic pressure) precede difficulty with ventilation, hypercarbia, and a rise in central venous pressure.
    • Distension is not appreciated in the prone position until later in the course.

Venous gas embolism

• Rare but potentially fatal complication
• The gas (in this case, air) enters the venous system and passes through the right heart into the pulmonary circulation, blocking the output of the right heart
• Diagnosis and Evaluation
  • Characterized by
    • Auscultation of a mill-wheel cardiac murmur♣
    • Hypoxemia
    • Hypercapnia
    • Depressed cardiac output
    • Hypotension
    • Dysrhythmias
• Management
  • Swift response is required and includes positioning the patient head down with the right side up.♣

Pneumothorax or pleural effusion

• Risk with supracostal puncture
  • A supracostal puncture should be performed only during full expiration.
  • The chest should be examined at the end of PCNL procedure in which a supracostal puncture is used

Colon injury

• Risk factors for colon injury
  1. Very little retroperitoneal fat (thin females, elderly)
  2. Previous jejunoileal bypass resulting in an enlarged colon
  3. Anterior calyceal puncture
  4. Previous extensive renal operation
  5. Horseshoe kidney
  6. Kyphoscoliosis
• Diagnosis and Evaluation
  • Typically, the injury is retroperitoneal; thus signs and symptoms of peritonitis are infrequent
  • Often diagnosed on a postoperative nephrostogram
• Management
  • If perforation
    • Extraperitoneal: placement of a ureteral catheter or double-J stent to decompress the collecting system and by withdrawing the nephrostomy tube from an intrarenal position to an intracolonic position, thus serving as a colostomy tube.
      • The colostomy tube is left in place for a minimum of 7 days and is removed after a nephrostogram or a retrograde pyelogram showing no communication between the colon and the kidney.
    • Intraperitoneal (with pertioneal signs (guarding, rebound)): surgical exploration and intestinal diversion.

Other potential complications

• Adjacent organ injury (e.g. spleen)
• Failed access

Fluoroscopy

• Radiation safety
  • Effective radiation dose is measured in sieverts (Sv) or gray (Gy)
    • 1 Gy = 1 Sv
    • Typical background radiation: 3 mSv/yr
• Fluoroscopy
  • Sources of radiation (3):
    1. Primary x-ray beam
    2. X-ray tube housing leakage
    3. Scatter from the patient and image receptor
  • Methods to reduce radiation exposure (3):
    1. Minimizing time
    2. Increase your distance
       • If you double your distance from a radiation source, you will reduce your dose by a factor of four (inverse square law)
    3. Use shielding

Open, laparoscopic, or robotic stone surgery

• Although a single open surgical procedure may seem to be the optimal procedure in the short term, the inevitable scar tissue that develops will compromise any future stone removal procedures.
• Indications (2):
  1. Salvage technique for failed PCNL, SWL, and ureteroscopy
  2. Associated anatomic abnormality requiring operative intervention, such as UPJ obstruction and infundibular stenosis

Nephrectomy

• Remains an option for patients with non-functioning kidneys or stone disease with a normal contralateral kidney.
  • Partial nephrectomy is also an option for a stone in a localized area of irrevocably poor function.

Questions

1. What are the 4 techniques available for intracorporeal lithotripsy? Which method is associated with the highest risk of perforation?
2. What is the zone of thermal injury associated with laser ablation?
3. What are the 3 types of shock wave generators?
4. What are the 6 mechanisms of stone comminution?
5. What are 7 risk factors for the development of a post-SWL hematoma
6. What are 4 potential chronic renal changes that may be associated with SWL treatment?
7. What are 6 contraindications for SWL?
8. How would you control PCNL bleeding? What if that didn’t work, what would be your next step? Next step? Last step?

Answers

1. What are the 4 techniques available for intracorporeal lithotripsy? Which method is associated with the highest risk of perforation?
   • Flexible: laser, EHL (highest risk of perforation)
   • Rigid: ballistic, ultrasound
2. What is the zone of thermal injury associated with laser ablation?
   • 0.5-1mm
3. What are the 3 types of shock wave generators?
   1. Electrohydrolic
   2. Electromagnetic
   3. Piezoelectric
4. What are the 6 mechanisms of stone comminution?
   1. Spall fracture
   2. Squeezing-splitting
   3. Shear stress
   4. Superfocusing
   5. Acoustic cavitation
   6. Dynamic fracture
5. What are 7 risk factors for the development of a post-SWL hematoma
   • TD COACH
   1. Thrombocytopenia
   2. Diabetes
   3. Coronary artery disease
   4. Obesity
   5. Age
   6. Coagulopathy
   7. Hypertention
6. What are 4 potential chronic renal changes that may be associated with SWL treatment?
   1. Accelerated rise in systolic blood pressure
   2. Decrease in renal function
   3. Increased rate of stone formation
   4. Induction of brushite stone disease
7. What are 6 contraindications for SWL?
   1. Pregnancy
   2. Uncorrected coagulopathy
   3. UTI
   4. Arterial aneurysm near target area
   5. Inability to target stone
   6. Obstruction distal to target stone
8. How would you control PCNL bleeding? What if that didn’t work, what would be your next step? Next step? Last step?
   1. Place nephrostomy tube
   2. Clap nephrostomy tube
   3. Place Kaye nephrostomy tube
   4. Angioembolization
   5. Partial nephrectomy

References

• Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 54