Direct-in-Scope Suction: Advantages and Limitations

Technology for treating kidney stones continues to advance, particularly with the emergence of suction into the armamentarium.

In part 2 of our 5-part series of suction technology for treating kidney stones, Karen L. Stern, MD, and Naeem Bhojani, MD, FRCSC, discuss direct in-scope suction (DISS). DISS scopes integrate suction directly into the working channel. They generally feature 1 channel that serves for both inflow and suction. To activate suction, the inflow must be temporarily shut off. DISS scopes have smaller channels compared with CVAC 2.0 and the flexible and navigable ureteric access sheath (FANS). Due to these smaller channels, DISS is primarily effective for evacuating dust, but not larger stone fragments. This limitation is significant, as not all stones can be easily broken down into dust.

Stern and Bhojani compare DISS with FANS. They highlight FANS as a device that significantly improves visualization and allows for the removal of larger stone fragments, not just dust. A major pro of FANS is its versatility; if it can't be advanced to the collecting system, it can still be used as a standard sheath. FANS is less expensive than some scopes. Furthermore, FANS helps maintain low intrarenal pressure due to high throughput (irrigation inflow and suction), reducing the risk of post-operative infection and sepsis. This constant fluid movement also helps keep the operative temperature down. Using FANS allows surgeons to worry less about the duty cycle (time on/time off) of the laser.

However, Stern and Bhojani note, FANS can increase surgeon workload and add significant operative time. It also contributes to the rising trend of surgeons focusing on removing every stone particle rather than leaving small dust that would pass naturally.

Combining a DISS scope with a FANS sheath allows the surgeon to activate the suction on the DISS scope, which holds the fragment, and then withdraw the scope and stone together through the FANS sheath. The main drawback to this highly effective method is the increased cost of using both devices.