What are the complications and preventive measures of using Ureteral Access Sheaths (UAS) in Retrograde Intrarenal Surgery (RIRS)?

Complications of Ureteral Access Sheath in RIRS

Ureteral access sheaths in RIRS reduce postoperative infectious complications but carry a risk of ureteral injury that increases with larger sheath sizes, particularly in non-prestented patients. 1, 2

Major Complications and Their Incidence

Ureteral Injury

• Low-grade ureteral injuries occur in 18.8-27.5% of cases, with higher rates associated with larger diameter sheaths (12F/14F vs 9.5F/11.5F) 2
• High-grade ureteral injuries occur in 5-11.9% of cases, with significantly higher rates when using 12F/14F sheaths in non-prestented patients (11.9% vs 5%, p=0.013) 2
• Ureteral stricture formation occurs in approximately 1.6% of cases overall, though this difference was not statistically significant between sheath sizes (2.5% for 12F/14F vs 0.6% for 9.5F/11.5F) 2
• Non-stented patients using UAS demonstrate PULS score of 1 (low-grade trauma), while prestented patients show PULS score of 0 (no injury) even with larger 12F/14F sheaths 3

Infectious Complications

• Postoperative fever is reduced by 51% with UAS use (RR 0.49; 95% CI 0.29-0.84) 1
• Postoperative infection is reduced by 50% with UAS use (RR 0.50; 95% CI 0.30-0.83) 1

Pressure-Related Complications

• UAS lowers intrarenal pressure (IRP) by approximately 18 mm Hg when suction is activated (from 42.30 mm Hg to 24.45 mm Hg) 4
• Paradoxical IRP elevation can occur with extended suctioning >5 seconds, especially at high vacuum settings (>200 mm Hg), due to outflow tract collapse 4

Prevention Strategies

Prestenting Protocol

• Prestenting for at least one week results in ureteral enlargement and protects against injury, allowing safe placement of larger diameter sheaths (12F/14F) with PULS score of 0 3, 5
• Prestenting is not routinely required but may improve treatment outcomes for renal stones 6

Sheath Size Selection

• Use 9.5F/11.5F sheaths in non-prestented patients to minimize high-grade ureteral injury risk (5% vs 11.9%) 2
• Reserve 12F/14F sheaths for prestented patients where ureteral protection is established 3, 2

Force of Insertion Monitoring

• Maximal force of insertion ranges from 0.91 to 5.9 Newton, with lower forces associated with smaller sheaths and prestenting 3
• Consider semirigid ureteroscopy with 7.8-F sheath prior to UAS placement in non-stented patients to facilitate passage 3

Vacuum-Assisted Technique Optimization

• Use lower suction settings (≤200 mm Hg) rather than maximum suction to achieve greater delta IRP reduction (25.44 mm Hg vs 10.26 mm Hg, p=0.04) 4
• Limit suction activation to short bursts of <5 seconds to prevent paradoxical IRP elevation from outflow tract collapse 4

Postoperative Management

• Routine post-URS stenting is unnecessary after uncomplicated procedures and may increase morbidity 6
• Stenting is advised in cases with trauma, residual fragments, bleeding, perforation, UTI, or pregnancy 6
• Alpha-blockers improve stent tolerability when postoperative stenting is required 6

Clinical Outcomes Without Significant Difference

• Stone-free rates are equivalent with or without UAS (RR 1.05; 95% CI 0.99-1.11) 1
• Operative time shows no significant difference (MD 3.56 minutes; 95% CI -4.15 to 11.27 minutes) 1
• Length of hospital stay is comparable between groups (MD 0.32 days; 95% CI -0.42 to 1.07 days) 1

Common Pitfalls to Avoid

• Avoid using large diameter sheaths (12F/14F) in non-prestented patients due to 2.4-fold increased risk of high-grade ureteral injury 2
• Do not use prolonged continuous suction with vacuum-assisted sheaths, as this causes outflow collapse and paradoxical pressure elevation 4
• Avoid routine stenting after uncomplicated UAS-assisted RIRS, as this increases morbidity without proven benefit 6
• Consider UAS use specifically in patients at higher risk for infectious complications to maximize the demonstrated benefit of reduced postoperative fever and infection 1