This document discusses surgical management for urinary lithiasis, focusing on extracorporeal shock wave lithotripsy (ESWL) and percutaneous nephrolithotomy (PCNL). It covers the physical principles, methods, and complications of ESWL, as well as techniques, patient preparation, anesthesia considerations, stone removal methods, and intraoperative and postoperative complications of PCNL. The goal of PCNL is complete or nearly complete stone clearance to simplify any needed secondary procedures. Patient positioning, bleeding, and organ injury are among the risks during PCNL, while fever and sepsis are common postoperative complications if not managed promptly.
3. METHODS AND PHYSICAL PRINCIPLES
• External source generates shock wave
directed towards patient’s body
• Propagation of linear waves, although large
amount of pressure is used – relatively weak
and only induce slight compression and
deformation of material
• Shock waves only apply sufficient strength at
the targeted part generating enough force
to fragment a stone
5. ELECTROHYDRAULIC (SPARK GAP)
• Spherically expanding shock wave is generated by
and underwater spark discharge
• High voltage is applied to two opposing electrodes
resulting in a spark that produces a vaporization
bubble
• Bubble expands and collapse rapidly producing a
high energy pressure wave
6. ELECTROMAGNETIC GENERATOR
• Produce a magnetic field in either a flat plane or
around a cylinder
• Flat plane waves are focused by an acoustic lens
• Cylindrical waves are reflected by a parabolic
reflector and transformed into a spherical wave
7. ELECTROMAGNETIC GENERATOR
• More controllable and reproducible than
electrohydraulic generators
• Will deliver more shocks before needing servicing
• Introduce energy over a larger skin area – less pain
• Due to high energy density – increased risk of
subcapsular hematoma
8. PIEZOELECTRIC GENERATOR
• Produces shockwaves with directly
converging shock fronts
• Capacitor is fired to several
hundred to thousand piezoceramic
elements
• More focusing accuracy and longer
service life
• Possibility of anesthetic-free
treatment because of low-energy
density at the skin entry point
9. IMAGING SYSTEMS
• Three basic designs used for
stone localization:
• Fluoroscopy Alone
• Ultrasonography Alone
• Combination of both
10. FLUOROSCOPY ALONE
• Previous models used 2 x-ray
converters arranged at oblique
angles, 90 degrees from each other
to localize stone effectively
• To reduce cost, an adjustable C-Arm
is now used
12. STONE FRAGMENTATION
• Initial short and steep compressive front 40
megapascals (MPa) followed by a longer, lower
amplitude negative (tensile) pressure of 10 MPa, with
the entire pulse lasting for a duration of 4
microseconds
• Ratio of 5:1 positive to negative peak pressure
• Comminution (fragmentation) results from
mechanical stressors created by 2 mechanisms
occurring simultaneously or separately:
• Directly by incident shockwave
• Indirectly by collapse of bubbles
13. STONE FRAGMENTATION
• Squeezing-splitting or circumferential compression – difference in
sound speed between stone and surrounding fluid
• Shear stress – generated by shear waves that develop as the shock
wave passes into the stone
• Superfocusing – amplification of stresses inside the stone because of
the geometry of that stone
14. STONE FRAGMENTATION
• Cavitation - formation and subsequent collapse of bubbles, oscillating
in size then collapse violently, giving rise to high temperature and
pressures
• Accumulation of damage – leads to eventual destruction of the stone
structure
15. BIOEFFECTS: ACUTE EXTRARENAL DAMAGE
• SWL induces acute injury in variety of extrarenal tissues
• Associated with trauma to organs such as liver and skeletal muscle
• Rare reports of colonic perforation, hepatic hematoma, splenic
rupture, pancreatitis and abdominal wall abscess
• Extrarenal vascular complications
16. ACUTE RENAL INJURY:
STRUCTURAL AND FUNCTIONAL
CHANGES
• Almost all post SWL patients for renal stones
demonstrate hematuria after ~200 shock waves
• Hematoma rates range from 1-20%
• Appearance of renal hematomas range from mild
contusion to a large hematoma associated with severe
bleeding necessitating BT or even angiographic
emobilization
17. ACUTE RENAL INJURY:
STRUCTURAL AND FUNCTIONAL CHANGES
• Probability of a subcapsular hematoma
increased 2.2 times for every 10-year increase in
the patient’s age
• Existing hypertension to be at increased risk for
the development of a perinephric hematoma
• Other risk factors: diabetes mellitus, coronary
artery disease, and obesity, all of which suggest
a link to a vascular disorder
19. MECHANISM FOR TISSUE INJURY
• The violent collapse of cavitation bubbles generated by the
shock waves is primarily responsible for the cellular
changes (Cavitation concept)
20. TECHNIQUES TO OPTIMIZE SHOCK WAVE
LITHOTRIPSY OUTCOME
• Acoustic output and focal volume of
shock
• Number of shocks delivered and rate
• Power or voltage used
• Wider focal width – increased stone
breakage
• Use of optimal coupling medium such as
oil or gel – efficient transfer of energy
21. ADJUNCTS TO IMPROVE SHOCK WAVE
LITHOTRIPSY OUTCOMES
• AUA – placement of ureteral stents at
time of SWL is not recommended
• Use of MET is found to be beneficial
• Use of A-blockers for 2 weeks post SWL-
improvement in stone free rates
• Percussion diuresis and inversion (PDI)
22. FUTURE DIRECTION
• Visio-track (VT) locking system
• Hand held probe that allows the
lithotripter to “lock on” to the stones
during treatment
• Ultrasonic propulsion of renal calculi
• Focused ultrasound is used to expel small
stones and fragments from urinary system
24. PATIENT PREPARATION
• Complete history and physical exam
• Absolute contraindications
• Uncorrected coagulopathy
• Active, untreated UTI
• Percutaneous nephrostomy drain without manipulation of the calculus of associated
with obstruction of renal unit and sepsis
• Pre operative lab evaluation: CBC, electrolytes, Crea, renal function tests
25. PATIENT PREPARATION
• Urine culture: if with suspicion of infection
• Perioperative antibiotics can be appropriately tailored to culture specific organisms
• Preoperative imaging: Plain abdominal CT
26. ANTIBIOTICS
• Antibiotic prophylaxis reduces infectious complications
• Institutional antibiograms aid in selection of most appropriate perioperative
antimicrobial regimen
• Fragmentation of stones, despite sterile urine, may release preformed
bacterial endotoxins and viable bacteria – risk for sepsis
• Patients with indwelling stents
27. ANESTHESIA
• PCNL can be performed after the administration of general, epidural or local
anesthesia
• Local anesthesia such as lidocaine can be delivered into the access tract to
the renal capsule
• Regional anesthesia for percutaneous procedures
• High block Is necessary to eliminate all renal pain
• Distention of renal pelvis during PCNL – cause a vasovagal reaction not
prevented by regional block
28. ANESTHESIA
• Upper pole puncture - GA is preferred to control respiratory movement
essential to minimize pulmonary complication
• Anesthesiologist must be aware of possible pulmonary injuries (hydrothorax
and pneumothorax) – close monitoring of airway pressure, CO2 levels and
O2 saturation as well as frequent lung auscultation
• Risk of hypothermia – warming of fluids; use of patient warming devices
29. PATIENT POSITIONING: PRONE
• Most commonly used position
• Chest supported by either a single horizontal chest roll
across the nipple line or two vertical rolls positioned
along the mid-clavicular line
• Elevation of legs to prevent pressure injury of lower
extremities
• Arms positioned toward the head in a modified
swimmer's position
• Padding of all pressure points to prevent injury
30. PATIENT POSITIONING: PRONE
• Direct access to favorably located posterior renal calyces
• Upper, mid or lower pole can be accessed
• Offers ready access to proximal ureter and ins some
cases, entire collecting system
• Allows bilateral percutaneous procedure without
repositioning
• Increased pulmonary capacity
31. PATIENT POSITIONING:
SUPINE
• Patient is positioned with the ipsilateral side
toward the most lateral aspect of the table and
the flank elevated with a bolster or 3-liter bag of
saline underneath the lumbar fossa
• The ipsilateral arm is positioned across the chest,
and padding is applied to limit pressure to the
elbow and wrist.
32. PATIENT POSITIONING:
SUPINE
• Several modifications such as Galdakao-
modified supine position
• Easy access to airway
• Optimization of CP function
• Faster operative times (no repositioning)
• Radiation exposure to surgeons hands
minimized
• Surgeon can perform procedure in seated
position
33. CHOICE OF CALYX FOR ACCESS
• Dictated by patient positioning
• Prone – posterior calyces are most accessible
• Supine – anterior ones are preferred
34. UPPER POLE CALYX
• Puncture into the upper pole calyx provides the most versatile access
• This site often requires supracostal (above the 12th rib) access leading to an
increased risk for pleural morbidity
• However, if entry directly above the 12th rib (11th intercostal space) provides the
best access to the optimal calyx, then the benefit generally exceeds the risk
35. INTERPOLAR CALYX
• Interpolar calyceal access likely is the least versatile
• reserved only for procedures limited to the interpolar region
36. LOWER POLE CALYX
• Puncture into the lower pole calyx affords the surgeon ready access to the
majority of the kidney while essentially eliminating the possibility of
pulmonary morbidity with upper-pole access
• With the use of a flexible scope, access to most calyces can be achieved
37. IMAGE GUIDANCE FOR PUNCTURE
• Two well described methods of antegrade percutaneous access
• Eye of the needle technique (Bull’s eye)
• fluoroscopy unit directly above the patient (directed vertically) and select the desired calyx
• rotate the top of the fluoroscopic unit 30 degrees toward the operator, which brings the
fluoroscopic view approximately in line with the posterior calyces
• Triangulation technique
• inspect the kidney with the fluoroscopy unit directly above the patient to select the desired
calyx, and hold the needle in the approximate position of the desired angle of entry
• Triangulation relies on two distinct fluoroscopy unit positions to address both medial-lateral
orientation of the needle and depth.
38. STONE REMOVAL
• Use of physiologic solution for irrigation during PCNL to minimize dilutional
hyponatremia in event of large volume extravasation
• Use of an amplatz working sheath prevents elevated intrapelvic pressures
• Rigid nephroscopy is performed and small stones may be grasped or extracted with
stone baskets
• Larger stones require fragmentation before extraction
39. STONE REMOVAL
• Rigid nephroscopy is the preferred method for
stone removal
• Flexible nephroscopy may be used during PCNL to
survey the entire renal collecting system for
residual stone fragments
• Entire collecting system including the proximal
ureter should be examined systematically
40. STONE REMOVAL
• LASER or electrohydraulic lithotripsy are used
to fragment larger stones
• Fragments may be flushed or manipulated
into the renal pelvis – easier retrieval
• The goal of PCNL is complete or nearly
complete clearance of stone material at the
time of the primary procedure, which greatly
simplifies secondary procedures
41. SPECIAL SITUATIONS
• Calyceal diverticula
• Direct puncture is quite difficult because of
small size of cavity
• After successful puncture, insertion of
guidewire to renal pelvis is often difficult
• If calculi is visible on fluoroscopy, it is
preferable to puncture directly to the stone
• Direct puncture to the diverticulum allows
use of rigid instruments providing better
visualization compared to indirect
approach
42. HORSESHOE KIDNEY
• The lower and centrally oriented position of the kidney, the orientation of the
collecting system, and the abnormal blood supply should be taken into account
• The upper pole calyces are more posterior and lateral and are often
subcostal, providing a convenient and relatively safe route for PCNL acces
• Flexible nephroscopy also may be required to gain access to the lower medial
calyces, where stones are often found
43. STAGHORN CALCULI AND COMPLEX
STONES
• Goal: Stone free
• If single access tract is to be sued – upper pole
access is preferred
• Allows treatment of upper pole, renal pelvis and
lower pole using rigid nephroscope
45. COMPLICATIONS: INTRAOPERATIVE
• Patient positioning
• Decreased venous return due to compression of vena cava in prone position
• Ischemic optic neuropathy
• Injuries to cervical spine or peripheral nerves
• Duration of surgery is linked to increased risk of nerve injuries
46. COMPLICATIONS: INTRAOPERATIVE
• Intraoperative bleeding
• May arise from renal parenchyma or arterial or venous vessels
• Technical aspects to reduce risk: papillary puncture of targeted calyx, less angulation
of amplatz sheath and nephroscope and fluoroscopic monitoring of serial dilatation
• In cases of significant bleeding and low visibility: recommended to stop the
procedure
• Arterial bleeding - renal angiography and embolization of bleeding vessel
47. COMPLICATIONS: INTRAOPERATIVE
• Organ injury (lung, pleura, spleen, liver, colon)
• Pleural injury during puncture above 12th rib - hydrothorax,
pneumothorax, hemothorax, lung injury or nephropleural fistula
• Early diagnosis is crucial
• Colonic perforation – presence of fecaluria from NT tube and diarrhea
• Retraction of nephrostomy tube into the bowel (colostomy)
• Drainage of kidney with ureteral stent
• Peritonitis – immediate surgery
48. COMPLICATIONS: INTRAOPERATIVE
• Absorption of irrigation fluid
• Absorbed from renal parenchymal vessels or from fluid extravasation
• Postoperative electrolyte imbalance is rare
• Volume of absorbed fluid is directly related to duration of surgery
49. COMPLICATIONS: POST OPERATIVE
• Fever and Sepsis
• Common complication of PCNL
• Despite use of prophylactic antibiotics, 10-40% if patient still develops
post operative fever
• Preoperative microbiological evaluation and assessment of patient risk
factors are crucial to prevent post op fever and sepsis
• Timely diagnosis and management of postoperative infectious
complications are crucial for optimizing outcomes and avoiding
progression to sepsis
