Intraoperative Cone-beam CT for Percutaneous Nephrolithotomy
Phase: NA
Conditions: Nephrolithiasis
Sponsor: Loyola University

 
Protocol Version #: 2 
  Version Date: August 23, 2021 
 
Protocol Outline 
 
Protocol Title: Intraop Cone-beam CT for Percutaneous Nephrolithotomy 
Protocol Date: August 23, 2021 
Principal Investigator: Kristin Baldea, Thomas Turk 
Research Team: Parth Patel, Alexander Kandabarow 
 
I. 
Abstract 
Percutaneous nephrolithotomy (PCNL) is a first-line treatment for kidney 
stones >2cm. Frequently, patients require multiple procedures to address their 
stone burden. The decision to proceed with a second-look procedure is based 
on follow-up CT imaging, which is obtained postoperatively. In this study, we 
propose the use of a portable CT scan technology to obtain follow-up imaging 
while the patient is still under anesthesia for the initial procedure. The goal of 
this study is to determine whether this allows the surgeon to identify residual 
fragments and render the patient stone-free within a single anesthetic event. 
 
II. 
Background and Significance/Preliminary Studies 
Percutaneous nephrolithotomy (PCNL) is considered a first-line management 
option for kidney stones larger than two centimeters. Unfortunately, because 
of the large stone burden, up to 70% of these patients are left with residual 
stone fragments after their initial PCNL.1 Additionally, an estimated 20% to 
60% of such patients ultimately require further interventions due to residual 
stone fragments.2 The need for a subsequent procedure is determined by 
postoperative abdominal computed tomography (CT) imaging, which is 
routinely performed on the first postoperative day at this institution. The 
decision to proceed with a second procedure is based on findings from this 
postoperative CT scan. 
 
Cone-beam CT (CBCT) is a novel portable imaging technique that can allow 
cross-sectional imaging to be obtained intraoperatively, rather than post-
operatively.3 Incorporating this modality would allow the surgeon to 
determine whether the procedure should be continued, in the event of residual 
fragments, or if it can be safely concluded. This would obviate the need for 
dedicated postoperative CT scans and, more importantly, reduce the need for 
subsequent procedures and consequently decrease the patient’s length of stay. 
 
III. 
Study Aims 
The purpose of this study is to determine whether using CBCT to perform an 
abdomen-pelvis CT scan immediately following initial PCNL, before the 
patient emerges from general anesthesia, allows the surgeon to determine 
whether additional work is needed or whether the procedure can be concluded 
without requiring further imaging or future interventions. Therefore, the 
primary outcome will be the rate of subsequent surgical intervention (i.e. 
“second-look” interventions) in patients undergoing CBCT.  
 

 
Protocol Version #: 2 
  Version Date: August 23, 2021 
 
IV. 
Administrative Organization 
This study will be performed exclusively in the Main Operating Room area of 
Loyola University Medical Center. 
 
V. 
Study Design 
1. The study population will be patients undergoing initial PCNL, and they 
will be recruited to participate in this study prior to surgery.  
2. Outcomes from this study will be compared with existing data on rates of 
second-look intervention at this institution.  
3. Our retrospective chart review of PCNL patients from 2018 and 2019 
revealed a total of 178 PCNL patients, with a second-look intervention 
rate of 31.5%. We anticipate that use of CBCT will reduce our 
second-look intervention rate to 10%. However, despite being 
rendered radiographically stone-free with CBCT, we imagine patients 
may require second-look procedures for various reasons; we estimate 
the upper bound of this occurrence to be 15%. Assuming this, along 
with a power of 80% and a type I error rate of 5%, our study would 
be appropriately powered with 39 patients. We will aim to recruit 60 
patients to allow for redundancy and unanticipated exclusions such as 
for reasons listed in VI.1.i.2. 
VI. 
Study Procedures 
1. Subject selection procedures 
i. Sampling plan 
1. Inclusion criteria: 
a. Patients >18yo 
b. Undergoing initial PCNL 
c. Stone fragmentation 
(laser/ultrasonic/mechanical) was performed 
during the procedure 
2. Exclusion criteria: 
a. Patients who are deemed by the operating 
surgeon not to require any form of CT imaging, 
intra-operatively or post-operatively (for 
example, this can occur in the event of a single 
visible stone which is removed in its entirety 
under direct vision without requiring any 
fragmentation) 
b. Patients whose procedures are aborted for various 
reasons, including but not limited to bleeding, 
hemodynamic instability, equipment failure, and 
inadequacy of nephrostomy access  
c. Patients whose habitus does not allow for the use of 
the CBCT machine 
ii. Recruitment procedures 
1. Patients undergoing initial PCNL will be recruited and 
provided protocol/consent materials at a preoperative 

 
Protocol Version #: 2 
  Version Date: August 23, 2021 
 
outpatient clinic visit. Consent will be obtained by one 
of the research team members at the preoperative visit 
or in the preoperative area on the day of surgery. 
2. The patient will not be required to attend any additional 
clinical appointments beyond standard care. The patient 
will not be compensated for their participation in the study. 
2. Data collection procedures 
i. A retrospective chart review of first-look PCNL procedures 
from 2018-2019 will be performed to identify a matched-cohort 
(based on patient demographics and stone characteristics) that 
meets the inclusion and exclusion criteria. 
ii. Data will be prospectively collected for our study cohort. The 
determination of our primary outcome (need for repeat surgical 
intervention) will be made in our usual fashion: via shared 
decision-making between the patient and the surgical team on the 
day subsequent to the initial procedure. 
iii. Data collected for both cohorts will include but not be limited to: 
1. Demographic factors (age, sex, race/ethnicity) 
2. Medical factors (patient height and weight, presence of 
medical comorbidities, surgical history, pertinent 
laboratory values) 
3. Stone factors (location, size, composition, and other 
characteristics) 
4. Surgical factors (length of procedure, blood loss, operative 
time, length of hospital stay, radiation dose) 
5. Surgical complications, ranked by Clavien-Dindo class 
iv. All data will be entered into Loyola’s secure RedCAP application.  
 
VII. 
Safety Monitoring Plan 
1. There are no additional anticipated patient safety issues associated with 
performing intra-operative CBCT when compared to standard post-
operative CT imaging.  
2. In another study using the same Medtronic O-arm CBCT system that is 
available at Loyola, it has been demonstrated that the radiation dose 
experienced by the patient from CBCT is lower than that from standard 
CT imaging.4 
3. In regards to radiation safety for operating room staff, standard 
precautions will be taken which include but are not limited to: using lead 
aprons for sterile surgical staff, optimizing the placement of sterile and 
non-sterile surgical staff, using lead aprons for sterile surgical staff, and 
standing beyond a 2-meter distance from the iso-centre. Assuming one CT 
per surgical procedure, a liberal average of three procedures per week, and 
48 work-weeks per year, an unprotected staff member would be expected 
to receive below 1.6 mSv a year at a distance of 2-meters from the iso-
centre.4 This is far below the occupational exposure limit set at 50 mSv 
per year by OSHA (Occupational Safety and Health Administration).  

 
Protocol Version #: 2 
  Version Date: August 23, 2021 
 
 
VIII. Analysis Plan 
1. The historical cohort and study cohort will be compared on a variety of 
demographic and surgical factors to ensure homogeneity between the 
groups. Chi-squared and Student’s t-tests will be performed as 
appropriate. 
2. The proportion of patients requiring a second-look procedure would be 
calculated for both our cohort under study and our historical cohort. These 
proportions would be analyzed with a chi-squared test to determine 
statistical significance. 
3. We would also perform subgroup analyses on a variety of patient 
characteristics, including but not limited to BMI, stone size, stone 
composition, and stone location, to determine if certain patient populations 
are more likely to benefit from CBCT. 
4. Data will be analyzed by exporting tables from RedCAP onto Loyola’s 
secure research network drives. From there, data will be imported into 
SPSS and analyzed as appropriate by the research team. 
 
IX. 
Literature Cited 
1. Pearle MS, Watamull LM and Mullican MA: Sensitivity of noncontrast 
helical computerized tomography and plain film radiography compared to 
flexible nephroscopy for detecting residual fragments after percutaneous 
nephrostolithotomy. J Urol 1999; 162: 23. 
2. Nevo A, Holland R, Schreter E, Gilad R, Baniel J, Cohen A, Lifshitz DA. 
How Reliable Is the Intraoperative Assessment of Residual Fragments 
During Percutaneous Nephrolithotomy? A Prospective Study. J Endourol 
2018; 32(6): 471-5. 
3. Roy OP, Angle JF, Jenkins AD, et al. Cone beam computed tomography 
for percutaneous nephrolithotomy: initial evaluation of a new 
technology. J Endourol. 2012;26:814–818. 
4. Pitteloud N, Gamulin A, Barea C, Damet J, Racloz G, Sans-Merce M. 
Radiation exposure using the O-arm® surgical imaging system. European 
spine journal. 2017 Mar 1;26(3):651-7.