Intra-operative cone-beam CT for detecting residual stones

Percutaneous nephrolithotomy (PCNL) is the standard surgical treatment method for large
kidney stones. Obtaining a stone-free status is the main goal of this surgical procedure.
However, residual stones remain in many cases where the urologist expected to have
reached a stone-free status. Partly because of this, re-intervention rates are high and stonefree
rates show room for improvement. Cone-beam computed tomography (CBCT) allows for
intra-operative cross-sectional and threedimensional imaging of the urinary tract. In this way,
any imaged residual fragments can be extracted in the same procedure, expectedly leading
to increased single step stone free rates.

The objective of this study is to determine the added value of cone-beam computed tomography in percutaneous
nephrolithotomy, by measuring differences in the stone-free rates for patients with cases in
which a cone-beam CT-scanner is used versus patients with cases in which no cone-beam
CT-scanner is used.

This study is a randomized-controlled trial. Patients will be randomized into two even groups
during their percutaneous nephrolithotomy. One group will receive an intra-operative conebeam
CT-scan, whilst the other group will undergo the standard procedure without an intraoperative
CT-scan. The randomization occurs at the end of the procedure, at the point where
the urologist would have otherwise terminated the procedure.

The study population consists of all patients above 18 years of age in the UMCG that
undergo percutaneous nephrolithotomy with the intention to become stone-free. Some
patients will drop-out if during the surgery it becomes clear that making a cone-beam CT
would have no consequences.

The main endpoint in this study is the stone-free status as assessed four weeks postoperatively
by low-dose non-contrast abdominal CT, as is standard follow-up procedure.
Secondary endpoints are the amount of PCNL procedures required per episode of 3 months
starting from the first PCNL procedure, the stone-free rates at the end of an episode of 3
months as assessed by low-dose abdominal CT and the amount of stone-related events
registered within a period of 12 months.

Using Cone-Beam CT in percutaneous nephrolithotomy for detecting residual stones
increases one-step stone-free rates and lowers the occurrence of stone-related events.

October 2019 - December 2019: Preparation period (MEC application, protocol and database creation)
January 2020: Start of study
Approx. 2024: Interim analysis (half of study population has completed 1-year follow-up)
Approx. 2026: End of inclusion period
Approx. 2027: Study completion
2027 onwards: Publication

The intervention is the use of an intra-operative cone-beam CT-scanner.