The thulium fibre laser (TFL) is a newer surgical laser with several uses in urology. In my talk I grouped them into three: breaking stones in the kidney and ureter (lithotripsy), enucleation of the prostate (lifting the enlarged inner part of the gland away from its outer shell), and cutting tissue.
Most of the talk was about stones. The meeting in Al Ain included a debate on the question "Is shock wave lithotripsy here to stay?" I argued the "No" side, and this is the case I made.
Three ways to treat a kidney stone
ESWL (extracorporeal shock wave lithotripsy) uses a machine outside the body to send shock waves through the skin and tissues to break the stone. There is no incision.
RIRS (retrograde intrarenal surgery) passes a thin telescope up the urinary passage into the kidney, so the stone is broken under direct vision. With the thulium fibre laser the stone can be reduced to fine dust, which is called dusting. There is no incision here either.
PCNL (percutaneous nephrolithotomy, keyhole surgery through the back to remove kidney stones) needs a small incision. In my comparison, PCNL used the Trilogy, a high-power stone-breaking device.
How the three compare side by side
Radiation exposure is medium to high with ESWL, medium with PCNL, and zero to low with RIRS.
For hard stones, and for stones in the lower calyces (the lowest cup-shaped chambers of the kidney), ESWL has a low stone-free rate, meaning fewer patients end up completely clear of stone. RIRS and PCNL both have good stone-free rates for these stones.
Size matters too. ESWL suits softer and smaller stones. PCNL can deal with stones of almost any size. RIRS can treat very large stones, though they may need a second RIRS session.
ESWL costs least, PCNL sits in the middle, and RIRS costs more. All three can be done as day care, with PCNL sometimes needing a one-day stay. Morbidity (the harm and discomfort a treatment causes) is less with RIRS and medium with PCNL. For ESWL, the long-term outcome is an open question.
Where shock wave lithotripsy runs into trouble
Some stones are a poor match for shock waves. Radiolucent stones do not show on X-ray, so they are hard to target. Harder stones, such as calcium oxalate monohydrate and cystine stones, resist breaking. Ureteric stones and very large stones are also difficult.
The size of the fragments cannot be controlled. Fragments can line up in the ureter and block it, a problem called steinstrasse, German for "stone street".
Anatomy can get in the way. A horseshoe kidney, kyphoscoliosis (curvature of the spine), a kidney sitting low in the abdomen, or a narrowing at the kidney outlet (the PUJ) or in the ureter all make treatment harder. The patient's breathing can shift the focal point. A stone in line with a rib or other bone, obesity, and bowel gas all soak up the shock waves before they reach the stone.
I also questioned whether ESWL is as non-invasive and cheap as it looks. Some patients need a stent (a thin tube placed in the ureter) or an extra procedure. The machine needs maintenance, and treatment often takes several sessions. Radiation and pregnancy are concerns, and stone clearance and long-term morbidity remain open questions.
Some patients are poor candidates: those on blood thinners or with a bleeding tendency, those with raised serum creatinine from chronic kidney failure, and those who need immediate and complete stone clearance. Complications include infection and sepsis, blood in the urine, a fluid collection around the kidney, and injury to other organs.
There is also a practical point. If a patient needs a double J stent anyway, which means an endoscopy, then why not do RIRS in the same sitting?
My conclusion on the slide was that ESWL is suitable only for a soft stone of about 1 cm, in a favourable position, with no contraindication. Every negative factor has to be ruled out first.
Why RIRS with the thulium laser works for most stones
RIRS breaks the stone under direct vision. It has fewer contraindications and fewer complications, and the thulium fibre laser makes the procedure quicker. Disposable scopes remove the worries about infection and about repairing damaged instruments.
In my own experience, RIRS works for most stones, except very large and staghorn stones (large branching stones that fill the kidney's drainage system). I do not need to place a stent beforehand, use an access sheath, or use fluoroscopy (live X-ray imaging). The average procedure takes less than an hour, and stone-free rates are high.
What the thulium laser changed in my practice
Since that debate I have used the thulium fibre laser widely. It works by a different ablation mechanism from the holmium laser (Ho:YAG) that most of us trained on, and the clinical results are starting to show it.
Recent comparative trials report better ablation efficiency and much lower retropulsion with TFL than with Ho:YAG. Retropulsion is the way a stone gets pushed away by the laser as you fire at it. For calcium oxalate monohydrate stones, which are among the hardest, that difference is real, and you feel it during the operation: less stone migration, faster dusting and a cleaner field.
TFL operates at 1940 nm with a quasi-continuous wave emission. Its “short” pulse is actually longer than the long pulse of Ho:YAG. That sounds counterintuitive until you understand the thermal dynamics involved.
With Ho:YAG, fragmenting dense stones was slow, and larger fragments would shield the target. With TFL, harder and larger stones clear faster.
The learning curve is real, though. Power settings, pulse duration and fibre size do not translate directly from holmium protocols, so a surgeon moving to TFL has to learn the settings again.
Cost per procedure is still a centre-specific question. Each unit should work it out honestly for its own case mix before deciding.
My answer to the debate question
I answered no. Shock waves can damage tissue, and that acute injury can lead to long-term harm, as McAteer and Evan set out in a 2008 review. They also pointed out that lithotripsy is still the only non-invasive way to remove stones, which gives it real value.
So the decision has to follow the stone and the patient's situation. No procedure is 100% perfect. ESWL and PCNL are good techniques. RIRS is quick, has fewer complications and high stone-free rates, and has a shorter learning curve.