Optimising pre‐operative imaging–surgery intervals for stones

Abstract Introduction and objectives The NICE guidelines for acute ureteric colic recommend diagnostic imaging, definitive management and definitive care within 24 and 48 h of symptoms and 4 weeks of temporisation, respectively. However, the NHS reality is fraught with long waiting times to definitive treatment, further compounded by a progressively increasing stone burden, paucity of on‐site lithotripters and a decrease in non‐cancer elective theatre sessions during the COVID‐19 pandemic. By the time patients attended the elective surgeries, their reference images (RIs) were often significantly out of date. Scant direction exists on what interval between imaging and surgery invalidates the usefulness of the RIs in providing surgical guidance. This study aimed to evaluate the role of imaging–surgery intervals (ISIs) on upper tract stone negative surgery outcomes and derive a cut‐off ISI warranting updated images, with a view to improving efficiency and patient safety. Materials and methods Upper tract stone surgeries were retrospectively assessed. Each renal unit was considered independently in bilateral stones. Cases were grouped into renal/pelvic (referred to as ‘RENAL’) and URETERIC stones. Data retrieved included the ISI, intra‐operative disparity (IOD) between stone‐related features on RIs and the surgical findings. Receiver operating curves (ROCs) were used to determine ISI cut‐offs more predictive of IODs. Results Four hundred and twenty‐seven surgeries on 174 (40.7%) RENAL and 253 (59.3%) URETERIC stones were appraised. No stones were found intraoperatively in 52 (12.1%) patients. Longer ISIs were associated with IODs, especially with URETERIC stones (p = 0.011, CI95 0.63; 4.84). The derived ROC ISI cut‐offs beyond which IODs, including negative surgeries, were more likely were 9 weeks for URETERIC (AUC: 63%, CI95 0.56; 0.70) and 19 weeks (AUC: 58.6%, CI95 0.50; 0.68) for RENAL stones, respectively. Conclusion There is a need to update reference imaging done more than 9 or 19 weeks before surgery for URETERIC and RENAL stones, respectively.


| INTRODUCTION
Hospital Episodes Statistics has shown a rising trend in the prevalence of urinary tract stones and admissions related to urolithiasis in England. 1 A 12%-35% rise in consultations and a 47%-79% rise in surgeries for urolithiasis across different age groups above 15 years of age were reported. 1 The increasing burden of patients with symptomatic stones, rising lifetime prevalence of stone disease and shortage in many centres of on-site shock wave lithotripters have led to long waiting surgical lists for patients under the National Health Service (NHS). 2 In 2020, the impact of the COVID-19 pandemic transcended all aspects of healthcare, modifying practice and the routine or emergent approach to management of other diseases. Guidelines recommended delaying definitive care for non-obstructing stones and encouraged conservative options or temporisation. 3,4 An online survey by the European Section of Urolithiasis (EULIS) Collaborative group showed that 89.4% of practitioners across 20 European countries consequently changed their practice to decompress obstructed urinary systems and delay definitive treatment. 5 Thus, the already long NHS waiting lists for stone treatment became longer. 6 The British Association of Urology recommends definitive treatment should not exceed 4 weeks from the temporising intervention, the former having been within 48 h of diagnosis. 7 The NICE guidelines recommend offering surgery within 48 h of diagnosis or readmission. 2 Given the aforementioned constraints, these timelines were not being met. Further, the NHS maximum waiting times from referral to definitive treatment of 18 weeks were being exceeded. 2,8 At our centre, from March 2020 of the COVID-19 pandemic, surgical priority was given to cancer-related surgeries with limited elective slots for stones. Our practice changed to aim towards primary ureteroscopy for new stone diagnoses presenting as emergencies. For elective surgeries, on the other hand, we experienced incidents whereby patients had outdated reference images by the time a date for surgery was available, with discrepant findings at surgery, negative surgery (NS) or even presentation with contralateral pain, rather than pain on the side the patient was listed to have surgery on. The latter scenario resulted in change of the intended side to be operated on the day of surgery after urgent re-imaging.
Our protocol by 2020 did not include repeat imaging on the morning of surgery as is the standard of care in some other centres. 9 An important consideration is the possible challenge of obtaining the CT scans on the day of surgery. A request for repeat imaging at our centre is rather driven by clinical information received prior to surgery, which might indicate a need. Another consideration for sameday pre-operative imaging is the possible surgery cancellation(s) on the day, with no allowance for substitution of the patients, as the protocol during the pandemic involved a 2-week pre-operative isolation period and negative COVID swab from 3 days prior to surgery. Therefore, the precious elective slot would be wasted if a CT scan on the day of surgery showed there was no need for surgical intervention.
Overall, there was limited existent evidence on the most appropriate time for repeat imaging prior to surgery.
The desire to improve the efficiency of the entire process and still ensure patient safety led to this study. We aimed to define a time limit from the last imaging beyond which patients were more likely to have surgical findings inconsistent with the prior radiological findings, or even negative surgeries, and should therefore, have updated imaging for stones.

| MATERIALS AND METHODS
A retrospective review of surgeries (ureteroscopies, standard and mini-percutaneous nephrolithotomies) done for urinary tract stones between December 2017 and November 2019 was conducted. Each urinary system was considered independently in patients with bilateral stone burden requiring surgical intervention. The cases were analysed as a cohort and dichotomised into those in the kidney or renal pelvis, hereby referred to as RENAL stones, and those between the proximal ureter and vesico-ureteric junction (VUJ), hereby termed URETERIC stones.
Data on stone size, location, radiological and surgical findings were retrieved. The primary outcomes were the time in weeks between the reference imaging used to plan the surgery and the surgery date, termed the imaging-surgery interval (ISI), and discrepancy rate between pre-operative imaging and intraoperative surgical findings, intra-operative disparity (IOD). Secondary outcomes included predictors of IODs and determination of the role, if any, of ISIs in IODs.
Patients with incomplete data, anatomic variations, concomitant nonstone-related surgeries or extracorporeal shock wave lithotripsy during the ISI were excluded from the analysis.
Measures of association were used to determine relevant factors predicting IODs. Receiver operating curves (ROCs) were used to derive ISI cut-offs predictive of IODs.
The patients were aged 17-96, with mean age of 56 years, SD 15.7.
Two hundred and sixty-six (62.3%) were males, whereas 161 (37.7%) were female. Thirty-seven were prescribed Tamsulosin, whereas 89 had pre-operative stents inserted. Thirty-two (7.5%) reference images were X-rays, whereas the rest were non-contrast helical CT scans. Tables 1 and 2 summarise the stone and imaging characteristics.  For either group, the ISIs of those with IODs or NS, exceeded the derived ISI cut-offs, whereas those without IODs fell within the ISI cut-off limits (Figure 1).

| DISCUSSION
The elective pathway in the NHS includes an 18-week target for a Finished Consultant Episode and clearly states that no patient should be waiting up to a year for definitive care. 10 The ISI ranges in this study show that these targets were not met. The pre-pandemic backlogs were significant, and the demand for more slots exceeded capacity in the NHS. 1 With the COVID-19 pandemic, the backlog of cases in the community and on waiting lists awaiting definitive treatment under the NHS increased significantly, with over 380 000 having waited for over a year by April 2021. 6,11 Renal stones and non-acute presentations were labelled non-urgent and deferred during the peak of the pandemic in accordance with the recommendations of the rapid reaction group. 3 A consensus on when to update the reference image used to make the diagnosis and plan for surgery is lacking at the moment.
Long delays have been noted to increase the incidence of NS. 12 It is generally agreed that negative surgeries for stones should be avoided. 12 The CROES study 13

| LIMITATIONS
Our study was small in comparison with multicentre studies or systematic reviews and would need larger numbers and further validation to verify its findings.
It also did not define how close to the date of surgery the task of updating images should be done. We, however, recommend updating the images 1-2 weeks before the surgery to permit replacement of the patient if the surgery is no longer required by the index patient.

| CONCLUSION
Increased intra-operative disparities and negative surgeries occur with ISIs greater than 9 and 19 weeks for URETERIC and RENAL stones, respectively. Updating the reference images that have exceeded these cut-offs could potentially reduce the risk of disparate findings at surgery, or even the risk of a stoneless surgery.
This would potentially reduce the risk to patient safety posed by an unnecessary surgery and anaesthetic exposure, as well as complications from the procedure itself. It would also allow better utilisation of theatre lists, improving efficiency, that is essential to reducing the backlog. It is also easy enough to effect.

| FUTURE RESEARCH
An in-hospital guidance to update the pre-operative reference images using these ISI cut-offs as a benchmark is being implemented at our centre. Further research to evaluate the incidence of NS and IODs thereafter would be necessary to validate the efficacy and accuracy of these ISI cut-offs.

AUTHOR CONTRIBUTIONS
The study concept, protocol design, data analysis and manuscript preparation were by Ijeoma Chibuzo; Ijeoma Chibuzo and Aleksandar Vucicevic collated the data; Abisola Oliyide, Adebanji Adeyoju and Zara Gall edited the manuscript; Adebanji Adeyoju and Zara Gall supervised the study.