Flexible ureteroscopy (RIRS): laser treatment for kidney stones

1What is flexible ureteroscopy?

Ureteroscopy (URS) uses a very thin telescope with a camera that is passed through the urethra into the bladder and up the ureter, with no cut in the skin. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a ureteroscope is longer and thinner than a cystoscope. A flexible ureteroscope can bend to reach inside the kidney itself, which is why the procedure is also called retrograde intrarenal surgery (RIRS). The stone is usually broken up with a laser fibre, and the fragments are removed with a tiny basket or, if very small, left to pass in the urine.

⏰When is ureteroscopy chosen over shockwave lithotripsy or PCNL?

The choice depends on stone size, position and your health, as our guide to kidney stone size explains. According to the American Urological Association (AUA) guideline:

• Kidney stones with a total size of 20 mm or less (outside the lower pole) can be treated with shockwave lithotripsy or ureteroscopy.
• For stones larger than 20 mm, percutaneous nephrolithotomy (PCNL) should be offered first.
• Shockwave lithotripsy should not be offered first for lower-pole stones larger than 10 mm.
• Ureteroscopy is recommended first for most mid and lower ureteric stones, and for most people on blood thinners that cannot be stopped.

The European Association of Urology (EAU) guidelines add that flexible ureteroscopy can be used even for kidney stones over 2 cm when PCNL or shockwave treatment is not an option, with a higher chance of a further procedure and a stent.

For the full range of options, see kidney stone treatment.

🔬How is the stone diagnosed before treatment?

According to the NIDDK, diagnosis relies on a urine test, blood tests, an abdominal X-ray (although not all stones show up on it) and a CT scan, which shows the stone’s size and position and whether it is blocking urine flow. They help the doctor choose the approach.

4Preparing for the procedure

• Fasting: according to Gloucestershire Hospitals NHS Foundation Trust, no food or drink for 6 hours beforehand, with water allowed until 2 hours before. Always follow your own team’s instructions.
• Bring a list of all your medicines to the pre-operative consultation, and tell the doctor about any blood thinners or possible pregnancy; only the doctor decides what to stop or continue.

5How the procedure is done

1. Anaesthesia: according to the British Association of Urological Surgeons (BAUS), it is normally done under a general or spinal anaesthetic.
2. The bladder is examined first, then a fine guidewire is passed up the ureter to the kidney.
3. A rigid or flexible ureteroscope is passed alongside the wire until the stone is seen.
4. The stone is broken with a laser, and fragments are removed with fine forceps or a retrieval basket.
5. A ureteral stent may be placed at the end, depending on what was done.

🩺The stent after surgery and its symptoms

A stent is a thin, flexible tube running from the kidney to the bladder to help urine drain. The EAU guidelines advise against placing one in uncomplicated cases and recommend it for ureteric injury, leftover fragments, bleeding, infection or pregnancy. According to University Hospitals Plymouth NHS Trust, discomfort, urgency, frequent urination and blood in the urine are common with a stent; Gloucestershire Hospitals notes these settle once it is removed. It is removed either by pulling an attached string or with a flexible cystoscopy under local anaesthetic gel. A stent is temporary and must not be forgotten; your doctor sets the removal date.

7Recovery and possible complications

According to the NIDDK, most people go home the same day. Gloucestershire Hospitals states that driving is usually possible after 24 to 48 hours and that most people need no more than a couple of days off work. Mild burning or light blood in the urine for a few days is common.

Possible complications include urinary infection, bleeding, injury to the ureter or kidney, failure to remove the stone, narrowing (stricture) of the ureter and stones coming back. According to the EAU guidelines, the overall complication rate after URS is 4-25%, most of them minor; the risk of urosepsis after surgery is up to 5%, while ureteric avulsion and stricture are rare (under 1%). Gloucestershire Hospitals reports that about 3 in every 100 patients develop an infection afterwards.

⏰When to seek urgent care after the procedure

According to University Hospitals Plymouth NHS Trust, contact your doctor or go to the emergency department straight away if you have:

• A temperature above 38°C, or shivering.
• Severe back or abdominal pain.
• Inability to pass urine.
• Heavy bleeding when passing urine.
• Signs of infection such as strong burning, foul-smelling urine or feeling generally unwell.

❓Frequently asked questions

10Sources

1. EAU Guidelines on Urolithiasis 2025
2. Kidney Stones: Surgical Management Guideline (AUA/Endourological Society)
3. Treatment for Kidney Stones – NIDDK
4. Diagnosis of Kidney Stones – NIDDK
5. Ureteroscopy for stones – British Association of Urological Surgeons (BAUS)
6. Ureteroscopy – Gloucestershire Hospitals NHS Foundation Trust
7. Managing a ureteric stent after ureteroscopy – University Hospitals Plymouth NHS Trust