2. Introduction
• A laser is a device that emits light through
the process of optical amplification by the
stimulated emission of electromagnetic
radiation.
• The word laser is derived from an acronym
for “light amplification by stimulated
emission of electromagnetic radiation.”
3. • Laser light has specific properties. It is
monochromatic and of a single wavelength.
• The light is coherent with a uniform spatial
relationship between all portions of the
electromagnetic wave.
4. • Although various wavelengths of lasers are
employed to treat soft-tissue conditions such
as stricture disease, benign prostatic
hyperplasia (BPH), urothelial cell cancer, and
genital skin lesions,
• the holmium:yttrium-aluminum-garnet
(Ho:YAG) laser has become the accepted gold
standard for the treatment of urinary calculi at
this time
5. Holmium:YAG
• The Ho:YAG laser is a 2140-nm pulsed laser
that is used for soft-tissue and lithotripsy
applications in urology.
• The 2140-nm wavelength is strongly
absorbed in water, traveling only about 0.5
mm in the fluid medium, making it ideal for
the urologic environment.
6. • In the prostate, the absorption depth is about
0.4 mm resulting in a high-energy density
that leads to the rapid vaporization of tissue.
Heat is also generated during this process
and allows for coagulation of small blood
vessels up to a depth of approximately 2 mm.
7. • Preceding technologies, such as the Nd:YAG
lasers, used photoacoustic or
photomechanical processes, where light
energy created shockwaves that fragmented
stones.
• In contrast, photothermal stone breakage
during holmium laser use was hypothesized
based on early observations of “glowing hot
stones.”
8. • Photothermal processes involve direct light
energy absorption (“photo”) by stone
surfaces causing rapid temperature
(“thermal”) increases, before significant heat
diffusion can occur.
9. • Ho:YAG lasers produce fine fragments in large
part owing to photothermal energy
absorption by urolithiasis; this results in the
breakdown and disintegration of the heated
area, causing craters and fragmentation
10. So,
• Laser lithotripsy has brought versatility to intracorporeal
lithotripsy by allowing safe fragmentation in virtually all
areas of the genitourinary tract.
• Ho:YAG laser fragmentation is predominantly due to
photothermal decomposition and possibly photoacoustic
propulsion of fragments.
• Laser output can be adjusted based on rate (Hz), energy (J),
pulse duration (μsec), and fiber size (μm).
• Maximal deflection is achieved with 200-μm fibers during
flexible ureteroscopy; however, maximal efficiency is seen
with 360-μm fibers.
11. • Proper laser fiber handling can help reduce
scope damage and prolong the life of reusable
fibers.
• Techniques used during stone fragmentation
include painting and “popcorning,” which create
fine stone dust (precluding removal), or crude
fragmentation for basket extraction.
• Laser lithotripsy can produce the smallest
fragments and is efficacious in all stone
compositions.
12. In Ureteroscopy
• By reducing the diameter of ureteroscopes,
slender intracorporeal lithotripters must pass
easily through a working channel smaller than 4
Fr, while allowing room for irrigation.
• These instruments also must be durable
enough to be advanced and retracted
repeatedly through a scope without breaking,
even when deflected 270 degrees.
13. • Ho:YAG laser lithotripsy fulfills these
requirements because hydroxy silica fibers
are thin, flexible, and durable and possess
transmission efficiencies allowing for
effective photothermal stone fragmentation.
14. • Flexible ureteroscopy typically uses 200-μm
laser fibers, which have a minimal impact on
scope deflection.
• For semirigid ureteroscopy, 365-μm fibers are
more suitable, although they can be used with
flexible nephroscopy if minimal deflection is
required.
• These are considered workhorse fibers because
they have been shown to display maximal
efficiency and durability while being typically
cheaper (than 200-μm fibers)
15. • Ureteroscopic laser fragmentation can be
performed by several Techniques:
• Dust-sized fragments are produced by painting
the fiber across the surface of a stone. Avoiding
the creation of large fragments that are difficult
to pass makes basket extraction unnecessary.
• By using lower energy levels of 0.2 J and higher
pulse rates (i.e., 40 Hz), small debris and
minimal retropulsion are encountered, while
trading off a reduction in total fragmentation.
16. • Controlling for total energy, increasing pulse
energy levels were found to result in larger
fragments, with faster fragmentation times.
Alternatively, as laser fragmentation
becomes more time-consuming as fragments
become smaller, one can create large pieces
and remove them using an endoscopic
basket.
17. Comparing with ESWL
• With improving endoscopic technology,
ureteroscopy and intracorporeal lithotripsy
have replaced ESWL for treatment of many
ureteric stones.
• A review of 82 patients undergoing either
ESWL or ureteroscopy for impacted proximal
stones showed no difference in 3-month stone-
free rates (80% vs. 68%) or complications,
although patients undergoing ESWL required
more secondary procedures (Khalil, 2013).
18. • Similar results were achieved in a prospective
randomized trial comparing 180 patients
undergoing ESWL or semirigid ureteroscopy
and laser lithotripsy for stones less than 2
cm. No significant differences were found
between the two modalities in terms of 3-
month stone-free rates, although re-
treatment rates were higher for ESWL (6.1%
vs. 1.1%, P < .001)
19. • a multicenter randomized trial of distal and
midureteric stones (n = 156) treated with ESWL or
ureteroscopy and laser lithotripsy showed an
advantage for ureteroscopy. The 3-month stone-
free rate was 91% for ureteroscopy (vs. 51% for
ESWL), and re-treatment rates were significantly
lower (9% vs. 45% in ESWL) (Hendrikx et al, 1999).
• Several authors found cost savings associated with
ureteroscopy and laser use compared with ESWL
because of higher success rates and lower re-
treatment rates
20. Comparing other intracorporeal
lithotripsy modalities,
• A retrospective review of 394 patients with proximal
ureteral stones treated with laser or pneumatic
lithotripsy via semirigid ureteroscopy was performed
showing 86% were treated successfully with
pneumatic lithotripsy; 14% required secondary ESWL
for residual fragments (identified on radiograph).
Laser lithotripsy produced a 97% stonefree rate, and
only 2% required secondary procedures. Ureteral
perforations were uncommon and not significantly
different between groups (Bapat et al, 2007).
21. • In larger distal and mid-ureteric stones (mean
diameter 13 mm), a prospective randomized
trial showed a delayed stone-free rate of 95%
with laser lithotripsy versus 85% with
pneumatic lithotripsy on noncontrast
computed tomography. Laser use was
associated with less stone migration, although
complication rates were for both arms
(Kassem et al, 2012).
22. In Percutaneous Nephrolithotomy
• Although laser lithotripsy is not the favored modality
for use in large renal stone burdens treated
percutaneously, it plays an important role in flexible
instrumentation.
• Anterograde nephroscopy using flexible scopes can
access calyces that rigid nephroscopes cannot reach,
reducing the need for multiple accesses.
• For patients with large impacted ureteric stones,
reimplanted ureters, and reconstructed bladders,
anterograde flexible ureteroscopy and laser lithotripsy
can allow straightforward access to the stone.
23. • Coarse fragmentation and basket extraction
simplify the procedure because the ureteric
portion proximal to the obstruction is often
dilated, allowing for active retrieval of larger
stones.
24. • Laser fragmentation is central to percutaneous
nephrolithotomy performed with reduced-
diameter sheaths (i.e., minipercutaneous, ultra-
minipercutaneous, micro percutaneous).
• Developed initially for pediatrics, the procedure is
now used in adults with sheath diameters ranging
from 24 Fr (8 mm) to 16 gauge (1.3 mm). When
using extremely narrow sheaths, techniques
require special miniaturized imaging technologies
and laser lithotripsy.
• Because stone extraction is impossible with
extremely narrow sheaths, 200-μm laser fibers
are used to dust stones, and debris is cleared by
pressurized irrigation or passive urine flow.
25. In Bladder Stones
• An advantage of laser cystolithotripsy is its use
in flexible cystoscopy, allowing for treatment
in reconstructed bladders and challenging
genitourinary anatomy that precludes use of
rigid instruments.
• Flexible laser lithotripsy has been used under
local anesthetic in healthy men with stones
greater than 3 cm, with minimal pain and
improvements in lower urinary tract
symptoms, without significant complications
26. • In pediatric urolithiasis, instrument diameter
plays a key role in management options.
Bladder stones have been successfully treated
using 8-Fr ureteroscopes with 550-μm laser
fibers for stones less than 4 cm .
• No laser-related complications were
encountered perioperatively, and no children
showed recurrences or urethral stricture
formation in longterm follow-up (mean 48
months).
27. • In children with complicated genitourinary
reconstructions, augmentations, and
continence procedures, percutaneous laser
cystolithotripsy through a previous suprapubic
catheter site allowed for maximal stone
fragmentation, while minimizing the risk to
intraperitoneal structures and/or vascular
supply to bowel segments used for
augmentation
