A ureteral access sheath (UAS) is a specialized medical device used in urological procedures to create a clear, protected pathway into the ureter and kidney. It functions as a conduit, allowing surgical instruments to pass smoothly and repeatedly into the upper urinary tract. This device helps reduce trauma to the delicate ureteral lining and maintains consistent dilation throughout the procedure, enhancing procedural efficiency and patient safety.
Understanding the Ureteral Access Sheath
A ureteral access sheath is a hollow, flexible tube. These sheaths are manufactured from materials like PTFE (polytetrafluoroethylene) with stainless steel lining mesh or Pebax, often featuring a hydrophilic coating. This coating becomes slippery when wet, facilitating smoother insertion and minimizing friction against the ureteral wall.
The sheath comes with a tapered dilator, an inner component that expands the ureter for the sheath’s outer diameter. Once the sheath-dilator assembly is in place, the dilator is removed, leaving the hollow sheath as a stable working channel. Ureteral access sheaths are available in various sizes, ranging from 9.5/11.5 French to 12/14 French in outer diameter, and lengths from 20 cm to 55 cm, to suit various patient needs. Some sheaths also include radiopaque markers for precise positioning under fluoroscopic imaging.
When a Ureteral Access Sheath is Used
Ureteral access sheaths are used in urological procedures requiring repeated access to the upper urinary tract, particularly for diagnosing and treating kidney and ureteral stones. They are frequently used during ureteroscopy and retrograde intrarenal surgery (RIRS), where a flexible scope navigates through the ureter to the kidney. The sheath provides a stable channel for the repeated insertion and withdrawal of instruments like ureteroscopes, laser fibers for stone fragmentation, and stone retrieval baskets.
A UAS offers several advantages. It reduces trauma to the ureteral wall from multiple instrument passes, protecting both the ureter and the ureteroscope. The sheath also improves irrigation fluid flow, maintaining clear visibility, especially with stone fragments or bleeding. By facilitating continuous irrigation and suction, the UAS helps manage intrarenal pressure, which can build up and lead to complications. It also aids in efficient stone fragment removal by allowing them to aggregate at its distal end, preventing scattering.
The Procedure and Recovery
The insertion of a ureteral access sheath occurs under general anesthesia, ensuring patient comfort and immobility. The surgeon first guides a guidewire into the ureter and up to the kidney. The lubricated sheath is then advanced over this guidewire into the ureter, often with fluoroscopic imaging for accurate placement. Gentle advancement is crucial to prevent injury to the ureteral wall. Once correctly positioned, the inner dilator and guidewire are removed, leaving the hollow sheath in place as a working channel.
Following the procedure, patients may experience temporary discomfort such as bladder spasms, increased urinary frequency, urgency, and a burning sensation during urination. It is also common to observe minor blood in the urine, which subsides within the first week. In some cases, a temporary ureteral stent may be placed to help the ureter heal and ensure proper urine drainage, usually removed as an outpatient procedure within a few weeks.
Patients are encouraged to rest and avoid strenuous activities immediately after the procedure. Most individuals can gradually resume normal daily activities within 1 to 2 weeks, but heavy lifting and vigorous physical exertion should be avoided for 3 to 4 weeks, or until cleared by their surgeon. Short baths or showers are permitted 24 to 48 hours after surgery, but swimming in pools or lakes is advised against for at least two weeks to minimize infection risk.
Possible Risks and What to Expect
While ureteral access sheaths are considered safe and improve procedural efficiency, their use carries some potential risks. A primary concern is ureteral injury during insertion or manipulation. These injuries can range from superficial mucosal abrasions (Grade 1) to deeper wall involvement (Grade 2), full-thickness perforations with visible peri-ureteral fat (Grade 3), or, in rare severe cases, complete avulsion of the ureter (Grade 4). Low-grade injuries are more common, and the risk of developing a long-term stricture from these injuries appears low.
Other potential complications include infection. Patients should monitor for symptoms like fever, chills, or persistent pain. Despite the sheath helping reduce intrarenal pressure, a slight infection risk remains, and preoperative antibiotics are often administered. Ureteral stricture, a narrowing of the ureter, is another potential long-term complication, though UAS use does not significantly increase this risk.
Patients should report any persistent flank pain, severe bleeding, or signs of infection to their healthcare provider immediately. Pre-stenting (using a ureteral stent prior to the procedure) has been associated with a lower risk of ureteral injury, particularly for higher-grade injuries.