Abstract
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The use of noncontrast CT scan for urinary stone diagnosis has a sensitivity of 97%, specificity of 96%, and accuracy of 97% for urinary stones. 2 Urologic guidelines for treatment of urinary stones consider the stone size using CT scan measurements as the main criteria for classify urinary calculi patients. It is because this factor is crucial for selecting the proper treatment for a specific patient, among other factors.
Several efforts have been made to determine preoperatively stone burden using proper image studies, but it seems there is no practical consensus. Patel and Nakada, 3 for example, reported in an interesting review article including 101 studies for ureteroscopy (URS) and shock wave lithotripsy (SWL) purpose, in which, they found an important heterogeneous use of different imaging modalities to determine stone burden. They reported that only 19 (19%) and 4 (4%) of the studies included in the review quantified two- and three-dimension of the stones, respectively, and up to one-third of all studies for both URS and SWL did not mention the imaging modality used to quantify the stone burden preoperatively.
Although, the American College of Radiologists recommends to the radiology community to report maximal axial and coronal measurements using CT scan for urinary stone diagnosis, 4 frequently, the axial maximal diameter (manually) is the only one reported by radiologist, specially considering that the coronal maximal diameter has been reported to be more significant for ureteral stones in terms of prognosis. 5 The missing of this information in the final radiologist reports generates uncertainty about the exact diagnosis of the stone burden. Another important issue is that the radiologist report is considered a legal statement in courts in several countries. Also, the incomplete information would cause rejections of money reimbursements or payments by insurance companies, social security, and health institutions because of inaccurate diagnosis and eventually legal ramifications or controversies in case of legal trial for specific patients or cases.
When urologists have not access to the complete CT scan files (axial, coronal, and sagittal planes images), the radiologist report becomes a case of “Faith Act” for urologists/endourologists. This situation does not help urologists to choose the proper surgical option and to discuss with patient and relatives with more detail about the urinary calculi, considering that in a recent survey, interviewed patients reported a positive practice to review radiographic images or diagrams with his/her attending urologist to get better understanding, which would be a useful additional modality for patient counseling. 6 For this purpose, when I have access to the CT scan digital files (i.e., CD or DVD), I have found of great utility some tools to view DICOM files at the office such as Osirix MD© for IOS© system (Pixmeo SARL, Geneva, Switzerland) and RadiAnt© for Microsoft© system (Medixant, Poznan, Poland).
It is known that there is a discrepancy between radiologists and urologists when measuring or reporting stone size or stone burdens. For example, Tzou et al. 7 measured stone burden recorded between urologists and radiologists, and examined how these differences could potentially impact stone management. They included in a trial of 10 months 219 patients who had CT images available and an accompanying official radiologic report. The concordance between urologic and radiologic assessment of aggregate stone size was higher for single stone (63%) than for multiple stones (32%). There was statistical significance when comparing the mean difference in aggregate stone size for single and multiple stones (p < 0.01). Surprisingly, >33% of stone-containing renal units had a radiologic report with unclear size estimation or with size discrepancy. 7 It has also been questionable whether urologists are capable or not for evaluating CT scan images for diagnosis, but there are positive results in this field. 8
Of course it is not the intention to supplant the valuable and expertise of the radiologist community following the directions of the article by Bell and collaborators. This software, in case to be validated and reproducible in the future, would be a potential helpful tool for radiologists to do more precise measurements and for urologists to avoid inter-observer biases. So in the case to have access to full CT scan images, urologists/endourologists would better plan surgical treatments for urinary calculi by themselves using this promising software. It is recommended to improve better communication between radiologist and urologist teams and communities working at the same or different institutions, and to create agreements for reporting in homologized form the most sensitive characteristics of the urinary calculi determined by intended or not intended stone CT scan that are crucial for planning urinary stone procedures or active surveillance.
On the other hand, improvements should be done to this preliminary study by Bell and associates; for example, it would be ideal to determine the reproducibility of the automated measurements first in the preclinicial scenario as in the laboratory, validating the computer software and evaluating standarized stone phantoms or stone models known in terms of size, shape, and density and comparing with manual measurements. Another level of evaluation would be to determine measurement accuracy using clinical cases of single urinary stone in in vivo and ex vivo trials, for example, patients who are candidates for open stone surgery (without lithotripsy) such as cistolithotomy, pyelolithotomy, nephrolithotomy, and ureterolithotomy to measure stone before surgery (inside the patient) and after the surgery outside of the patient, in automated and manual groups. The power range of the studied computer software should identify and characterize urinary calculi size ≤ 3mm, even stone density ≤ 200HU, and should be able to reconstruct the geometrical form or shape of the urinary stone(s) studied. Furthermore, to determine accuracy, inter-operator variability and reproducibility, the manual measurements should be repeated same number of times by different operators, and might be compared with the automated measurement in the same terms, times and variables used in the manual group. Finally, Bell et al, reported not significant difference when comparing density and calculi volume between manual and automated measurements, except in the stone length determinations in favor to the automated group. It suggests that until now the automated group, is not superior to all variables evaluated and determined by manual measurements, at least by this methodology.
That is why the article by Bell and coworkers gives us a fresh air sensation to be more precise in calculi urinary stone measurements. Further research and improvements are needed in this field. Hopefully, software developers, clinicians, and biomedical engineers soon would give us more precise tools to classify each patient in terms of stone burden, and this information would help us to develop more efficient nomograms to determine better stone-free rates among other desirable variables to offer to our patients suffering from urinary calculi or even to select and to follow patients candidates for active surveillance.