Advances in Retrograde Intrarenal Surgery for the Treatment of Kidney Stones

Dr Lee Han Jie, Associate Consultant, Department of Urology, Singapore General Hospital

Retrograde intrarenal surgery (RIRS) has become a first-line minimally invasive treatment for many kidney stones. Learn which patients are suitable for RIRS, the benefits of the procedure and how recent advances have expanded its role in managing more complex stone disease.

WHAT IS RETROGRADE INTRARENAL SURGERY (RIRS)?

RIRS is a minimally invasive surgical procedure used for the treatment of stones or other conditions (including tumours) within the kidney.

It involves passing a flexible ureteroscope (Figure 1) through the urethra, bladder and up the ureter into the kidney, without the need for an incision on the body. Within the kidney, laser fibres or stone retrieval baskets can be introduced through the ureteroscope for fragmentation and retrieval of stones respectively.

When is RIRS recommended?

General recommendations for patients to undergo RIRS include:

• Medium-sized kidney stones
  • Stones around 1-2 cm in size
  • Especially when there are multiple stones in several areas within the kidney
  • With recent advances, RIRS might also be possible for stones >2 cm in size, but on a case-by-case basis after consultation with the urologist
• Patients for whom a less invasive procedure is preferred
  This includes patients with other medical conditions, such as those requiring the use of antiplatelets/anticoagulants, or patients with difficult anatomy.
• Due to safety and high success rates, RIRS is a common first-line option for many stones, but is also performed for patients who fail other options for stone management such as extracorporeal shockwave lithotripsy (ESWL), or if other options are unlikely to succeed (e.g., very hard stones or stones in certain locations of the kidney including the lower poles).

Key benefits

Benefits for patients undergoing RIRS include:

• No external incision
  The entire procedure is performed using a scope, eliminating wound pain and complications like wound infections/scarring.
• High success (stone-free) rates
  RIRS can completely clear stones in up to 95% of patients1 after a single procedure, for stones ≤2 cm.
• Faster recovery
  Patients undergoing RIRS are usually discharged the same day and can resume normal activities quickly within days.
• Low complication rates
  RIRS has lower complication rates than other more invasive stone treatment procedures such as percutaneous nephrolithotomy (PCNL).

PROCEDURE

How is RIRS performed?

The procedure is usually performed under general anaesthesia (GA). A thin and flexible ureteroscope is inserted through the urethra, bladder and ureter to reach the kidney. The high-definition camera within the scope allows visualisation of the stone, which is then either fragmented or turned into fine dust using a laser (usually Holmium:YAG laser). The fragments are then suctioned out of the kidney or removed using a stone retrieval basket.

What can patients expect after RIRS?

After RIRS, a ureteral stent is usually left in place between the kidney and bladder. This is a thin, soft tube approximately 20-30 cm long that serves to:

• Ensure proper urine drainage from the kidney while
  the ureter heals from any minor swelling from the
  surgery
• Prevent obstruction of the ureter from residual stone
  fragments or blood clots

The stent is usually left in place for 1-2 weeks and removed in a short outpatient procedure – either via flexible cystoscopy under local anaesthesia, or by pulling a string attached to the stent.

Patients with stents may experience some symptoms, including:

1. Flank discomfort, especially when passing urine, as the bladder pulls gently on the stent
2. Urgency to pass urine, as the stent might cause mild irritation of the bladder
3. Blood in the urine, which tends to be mild and improves over time

These symptoms are common, expected, tend to be mild and can usually be managed with oral medications.

Complications

RIRS is generally a safe procedure with low complication rates. Complications can include the following:

• Haematuria
• Urinary tract infections: Urosepsis can occur in some cases, especially if the procedure is prolonged, and might require hospitalisation
  for antibiotic administration.
• Failure to access the kidney through the scope (approximately 5-10%):
  • This occurs because the ureter can sometimes be too narrow for the scope to be passed through into the kidney.
  •  In this situation, stone removal cannot be completed, but the urologist will place a stent (Figure 2) into the kidney. The stent is left for 1-2 weeks to allow the ureter to widen, before another RIRS procedure at a subsequent date where the scope can be safely passed into the kidney.
• Injury to the ureter, which might lead to scar formation (1%); most severe complication is complete tearing/avulsion of the ureter (<1%).
• Residual stones: For some larger stones or stones in difficult locations within the kidney, complete clearance might sometimes not be possible within a single procedure, and a staged RIRS might need to be done a few weeks later to ensure complete clearance of all stones.

RIRS IN SINGAPORE GENERAL HOSPITAL

Singapore General Hospital (SGH) is a major tertiary referral centre, with over 50,000 outpatient attendances annually and around 1,500-1,800 surgeries performed a year in the Department of Urology. The Department of Urology offers holistic evaluation of patients with suspected urolithiasis, as well as the entire array of stone treatments including Extracorporeal Shockwave Lithotripsy (ESWL), RIRS and Percutaneous Nephrolithotomy (PCNL). SGH performs a high volume of stone surgeries, likely the highest within the Singaporean context, with around 400 cases of RIRS and 100 cases of PCNL and Endoscopic Combined Intrarenal Surgery (ECIRS) a year.

Complex stones are also managed, including complete staghorn stones and stones in patients with an abnormal anatomy including transplant kidneys or in patients with previous urinary reconstruction (e.g., ileal conduit).

NEW ADVANCES IN RIRS

There have been several recent advances that have revolutionised the role of RIRS and significantly increased its effectiveness.

Flexible and Navigable Suction Access Sheath (FANS)

In recent years, RIRS has been performed with the aid of an access sheath, which is first placed into the kidney and allows the scope to be passed in and out of the kidney. 

The Flexible and Navigable Suction Ureteric Access Sheath (FANS) represents one of the most significant recent advances in RIRS technology. FANS includes a sheath that is placed into the kidney with two key additional features:

• A flexible tip that can be directed into different parts of the kidney, to improve access to stones in challenging locations.
• Continuous suction applied to the end of the sheath that allows stone fragments and dust to be actively suctioned out of the kidney after fragmentation.

These features have several key advantages:

1. Allows superior stone clearance, close to 90-95%, and shorter operative times
2. Smaller risk of postoperative complications, as the continuous suction reduces pressures within the kidney that are associated with complications such as infection
3. Has expanded the ability of RIRS to treat larger stones 2-3 cm that were traditionally too large to be cleared with the minimally-invasive RIRS

SGH has since incorporated FANS into all RIRS procedures resulting in high efficiency of stone clearance and lower risk of complications.

REFERENCES
1. Uy M, Moryousef J, Wang L et al. Flexible and navigable suction ureteral access sheaths for the treatment of urolithiasis: systematic review and meta-analysis. Eur Urol Focus. (2025). 10.1016/j.euf.2025.08.008

Dr Lee Han Jie is a urologist at Singapore General Hospital. He completed the SingHealth residency programme in 2025 as one of the top three chief residents and was named valedictorian of his graduating batch of SingHealth specialists. He is a passionate clinician with a keen interest in endourology, including the management of stone diseases, prostate enlargement and lower urinary tract symptoms.

With a keen interest in research and medical innovation to further improve clinical care, he has produced multiple academic publications and was awarded the prestigious National Medical Research Council (NMRC) Clinician-Innovator Award for medical device development.

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