What is the glue clot technique in the context of Retrograde Intrarenal Surgery (RIRS)?

Glue Clot Technique in Retrograde Intrarenal Surgery (RIRS)

The glue clot technique is a method to retrieve small stone fragments (<3 mm) during RIRS by using autologous blood or biocompatible adhesive to embed residual fragments that are too small for basket extraction, allowing them to be removed en masse from difficult-to-access locations like the lower calices. 1, 2

Technical Description

The technique involves the following steps during RIRS:

• After laser fragmentation of renal stones to <3 mm fragments, the lower calyx is filled with 5-10 cc of venous autologous blood with the patient positioned in reverse Trendelenburg 1
• The blood is allowed to clot in situ, embedding the small stone fragments within the clot matrix 1
• A confirmatory pyelogram is performed to ensure proper clot formation, followed by placement of a double-J stent 1
• The clot with embedded fragments is then removed either spontaneously through the stent or during subsequent procedures 1

Alternative adhesive materials beyond autologous blood have been tested, including novel biocompatible adhesive systems that can be applied directly through the flexible ureteroscope to capture stone dust 3

Primary Indications

This technique is specifically indicated for:

• Lower calyceal stones >6 mm and <2 cm where complete direct fragment removal is not feasible 1
• Residual fragments after primary shock wave lithotripsy (SWL) or percutaneous nephrolithotomy (PNL) as a salvage procedure 1
• Patients with upper ureteral tortuosities or narrowing that limit multiple instrument passes for conventional stone removal 1
• Stone fragments ranging from 0.2-0.8 mm that are too small to grasp with standard retrieval baskets 3, 2

Clinical Outcomes

The technique demonstrates excellent efficacy:

• Stone-free rates of 94% at 3 months and 97% at 6 months in the initial case series of 35 patients 1
• Complete clearance achieved in all pediatric patients in a case series of 4 children, representing the first use in pediatric ureteroscopy 4
• 84% stone-free rate for fragments 0.2-0.8 mm using biocompatible adhesive systems in kidney models 3
• Success rate of 97% for the occlusion procedure at first attempt 1

Technical Advantages

The glue clot technique offers several benefits over conventional fragment removal:

• Minimizes ureteral trauma by reducing the number of instrument passages required for active fragment removal 1, 2
• Addresses anatomically challenging locations where direct basket extraction is difficult or impossible 1, 3
• Not dependent on surgeon experience level for successful fragment retrieval 3
• Allows treatment of patients with indwelling DJ stents, including those with significant encrustation 1

Safety Profile

The technique demonstrates favorable safety outcomes:

• No patients required readmission for clot colic in the initial series 1
• Only 8.6% required more than overnight hospital stay 1
• No specific complications related to the clot formation were reported 1

Common Pitfalls to Avoid

• Ensure adequate reverse Trendelenburg positioning during blood clot formation to prevent premature clot migration 1
• Confirm clot formation with pyelography before stent placement to verify successful fragment embedding 1
• Do not attempt this technique in patients with active infection or coagulopathy, as these are relative contraindications 1
• Recognize that fragments >3 mm may not be adequately embedded and may require conventional basket extraction 1

Relationship to RIRS Indications

This technique complements the primary indications for RIRS, which include renal stones <2 cm and upper ureteral stones where ESWL has failed 5. The glue clot method specifically addresses the challenge of achieving complete stone-free status when the "dust and go" approach leaves residual fragments, as complete stone removal remains the goal rather than leaving clinically insignificant residual fragments 5.