European Journal of Cardiovascular Medicine

Imaging is a vital cog in the wheel of diagnosis and management of patients suspected with renal and ureteric calculi, and it is imperative to choose the appropriate investigation that is accurate and safe for the patient. The choice of appropriate investigation depends on various factors such as the nature of presentation, body habitus of the patient, cost of the investigation, and the effect of the investigation on the patient. Many modalities are available for investigating stone in patients such as ultrasonography (US), X-ray, computed tomography (CT) scan, and magnetic resonance imaging (MRI). CT, US, and X-ray are used widely. ^[1] US has lesser sensitivity when compared with CT for diagnosing renal stones. US has also been considered inferior to CT in the assessment of the size of the stones. US tends to overestimate the size of stones, particularly the smaller ones. This has huge implications in management decisions with respect to smaller calculi. Overestimation of stone size leads to surgery for stones which would have been managed conservatively had the accurate size of the stone known previously. It is imperative that the surgeon knows the accurate stone size preoperatively for decision making and also patient counselling. ^[2]

At present, CT is the gold standard for a patient suspected to have stone disease. However, CT scan is associated with the hazards of radiation and high cost. US is cheap and also devoid of any radiation hazard to the patient. But, at the same time, its usage is limited by decreased sensitivity and specificity, inaccuracy in measuring stone size, and observer dependency. In this article, we review the techniques to improve the accuracy of US in measuring stone size. ^[3]

US is an ideal first-line imaging modality for nephrolithiasis due to its advantages such as low cost, absence of radiation, and easy availability. But the reason for its limited use is due to its decreased sensitivity and reduced accuracy in measuring the stone size, the areas in which CT scores over US. The addition of newer modes in US and the change in settings have increased the accuracy of US but not to the extent that it can replace CT. ^[4] European Association of Urology also recommends US as the first-line investigation for patients who present with suspected nephrolithiasis. So, for these reasons, US can be considered as first line in selected situations but it is far from being called as an ideal investigation for nephrolithiasis.

This Study Intended to classification of renal stone using U/S scan from different soft images of U/S machine during abdomen U/S. The data of this Study was collected from different clinical centres and by data sheets, U/S soft image and CT KUB reports, the data has been collected from April 2019 to October 2019. Patient samples: A total of 90 patients were examined in different clinical centres as shows the number of all patients, Data were collected using a data collection sheet for all patients in order to maintain consistency of the information. The following parameters were recorded (Pt code, age, Gender, Stone density, stone size derived from (width* length) cm and Stone site) were recorded. Imaging technique: - A kidney ultrasound may be performed on an outpatient basis or as part of your stay in a hospital. Although each facility may have different protocols in place, generally an ultrasound procedure follows this process: You will be asked to remove any clothing, jewellery, or other objects that may interfere with the scan. If asked to remove clothing, you will be given a gown to wear. You will lie on an examination table on your abdomen. Ultrasound gel is placed on the area of the body that will undergo the ultrasound examination. Using a transducer, a device that sends out the ultrasound waves, the ultrasound wave will be sent through that patient's body. The sound will be reflected off structures inside the body, and the ultrasound machine will analyse the information from the sound waves. The ultrasound machine will create images of these structures on a monitor. These images will be stored digitally. If the bladder is examined, you will be asked to empty your bladder after scans of the full bladder have been completed. Additional scans will be made of the empty bladder. There are no confirmed adverse biological effects on patients or instrument operators caused by exposures to ultrasound at the intensity levels used in diagnostic ultrasound. While the kidney ultrasound procedure itself causes no pain, having to lie still for the length of the procedure may cause slight discomfort, and the clear gel will feel cool and wet. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort. In CTKUB You may be asked to change into a patient gown. If so, a gown will be provided for you. A locker will be provided to secure personal belongings. Please remove all piercings and leave all jewellery and valuables at home. are most frequently done with and without a contrast media. The contrast media improves the radiologist's ability to view the images of the inside of the body. Some patients should not have an iodine-based contrast media. If you have problems with your kidney function, please inform the access centre representative when you schedule the appointment. You may be able to have the scan performed without contrast media or have an alternative imaging exam. The most common type of CT scan with contrast is the double contrast study that will require you to drink a contrast media before your exam begins in addition to the IV contrast. The more contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract. Statistical Texture Analysis First-order texture analysis measures use the image histogram, or pixel occurrence probability, to calculate texture. The main advantage of this approach is its simplicity through the use of standard descriptors (e.g. mean and variance) to characterise the data. However, the power of the approach for discriminating between unique textures is limited in certain applications because the method does not consider the spatial relationship, and correlation, between pixels. For any surface, or image, grey-levels are in the range where Ng is the total number of distinct grey-level, If (Ni) is the number of pixels with intensity i and M is the total number of pixels in an image, it follows that the histogram, or pixel occurrence probability, is given by, In general seven features commonly used to describe the properties of the image histogram, and therefore image texture, are computed. These are: mean; variance; coarseness; skewness; kurtosis; energy; and entropy

A total of 150 patients were included in the study. In table 1, the patients were predominantly in the late adulthood and elderly age groups, with 50 patients (42%), 25 patients (31%) and 35 patients (27%) aged between 25-39, 40-59 and 60-79 years old respectively. The mean age was 52 years old. Gender wise distribution, there were maximum no. of patients were 87 males and 63 females. In table 2, from the 150 data collected patients, 45 renal calculi were detected on both USG and CTU. There were 11 false positive cases. The sensitivity and specificity of renal calculi finding on ultrasound were 52% and 86% respectively. The positive predictive value (PPV) was 84% and negative predictive value (NPV) was 57%. The accurateness of ultrasound in detecting renal calculi was 68%. Of the 45 renal calculi detected on USG, 33 calculi were measured. The remaining 7 calculi not measured were too small and defined as tiny or too large and labelled as staghorn calculi. In table 3, the majority of calculi noticed by USG measured 5.1-10 mm. The least, extreme and normal size noted was 3.5 mm, 22 mm and 6.8 mm ± 3.8 mm respectively. 45 renal calculus detected and 38 renal calculi were not detected on USG but positive on CTU and 41 findings were true negative. Of the 38 calculi not detected on USG but detected on CTU, 9 were described as tiny and the other 29 were measured on CTU. The mainstream of calculi not found by USG measured ≤ 5 mm. The least, extreme and normal size of calculi that were not identified on USG was 3 mm, 11 mm and 3.7 mm ± 2.1 mm respectively. In table 4, ultrasound detected only 4 of the 26 ureteric calculi that were detected on CTU giving a low sensitivity of 12%. However, it presented a more specificity of 97%. The accuracy of ultrasound in finding ureteric calculi was 81%. The PPV and NPV were 63% and 81% respectively. On the other hand, detection of urinary bladder calculi for the detection of urinary bladder calculi, ultrasound achieved 20% sensitivity and 100% specificity. The PPV was 100% with NPV of 98%. The accuracy was 98%.

This study showed that USG had limited value for the detection of renal calculi. The sensitivity and specificity of 53% and 85% respectively were lesser contrast to two earlier studies that had stated 81% and 100%, and 76% and 100% for sensitivity and specificity respectively. ^[5] However, our sensitivity exceeded that of another study, which reported a sensitivity of 24%, but a slightly higher specificity of 90%. The lengthier time interval between ultrasound and CTU (45% within 1 month, the rest 1 month or more) in this study could have donated to this difference, in compare to 1 month or less in earlier studies. ^[6,7] The poor sensitivity and the excessive false negative rates (41%) of USG exhibited in this study are related to multiple factors. Calculi may be missed at USG due to lack of acoustic shadowing of the calculus. The other factors would be the body habitus, 6 the selection of the transducer power, and focal length. ^[8,9] The excellent contrast resolution of CTU allows discrimination of slight differences in attenuation, allowing better visualisation of stones. Furthermore, CTU has the capacity to obtain a volume of data that comprises the whole urinary system and not just renal only. USG could miss calculi within some parts of the urinary tract, particularly the ureters. In this study, the false positive rate (FP) was 15% for USG and may have been due to renal vascular calcification. ^[10] With regard to the size of renal calculi that were detected, this study presented that the mean size of calculi noticed on USG was 7.6 mm ± 4.1 mm, similar to study that stated a mean size of 7.1 mm ± 1.2 mm. 7 Of the 53 renal calculi not detected on USG, 85% measured ≤ 5 mm. A previous study showed that the mean size of calculus detected on CTU was 4.2 mm ± 0.4 mm. Seventy-three percent of calculi not visualized on USG were 3 mm or less in size. The USG in which a 12-mm calculus had been missed but was detected later on CTU was performed by a junior trainee, and the time interval between USG and CTU was between 1 – 3 months. ^{[11, 12]} The existence of posterior acoustic shadowing depends on size of the calculus. Consequently, lesser the calculus, the more probable it might be missed. However, the reason for a large calculus not being identified on USG is not clear. One way to improve on USG skill is to repeat the USG whenever a false negative or false positive result is noted on CTU. ^[13] With regard to the detection of ureteric calculi, a prospective study in 1998 achieved a sensitivity of 19% and a specificity of 97%. Another study in 2007 showed a slightly higher sensitivity of 23% and specificity of 100%. In this study, almost similar results were achieved, with low sensitivity of 12% and high specificity of 97%. The low sensitivity is attributable to occurrence of bowel gas, which normally obscures the ureters, and more body habitus with dense subcutaneous fat that decreases visibility. ^[14] The specificity of calculi detection on USG is greater in the ureter than in the kidneys. This is because the identification of ureteric calculus is significantly helped by the occurrence of hydro ureter. In other words, USG deficits sensitivity for finding of ureteric calculi. However, it is impartially precise when calculi are seen. This study showed the accuracy of USG in detecting renal, ureteric and urinary bladder calculi was 67%, 80% and 98% respectively. ^[15] USG is not equivalent to CTU in detecting urinary tract calculi. Though, this does not mean that all patient suspected of having a urinary tract calculus should undergo a CTU. Based on the findings of this study, the following imaging algorithm is recommended. A limitation of this study is the extended time interval between ultrasound and CTU. Approximately 55% of the patients obligated their ultrasound and CTU done at more than 1 month apart. Accuracy of ultrasound could be affected as calculi could have moved or changed in size during this period of time. New ultrasound technique such as the use of Doppler ultrasound to detect “twinkling artefact” could potentially improve urolithiasis detection on sonography, and should certainly be looked into in future studies.^[16,17]

The sensitivity and specificity of USG in detecting renal calculi was 52% and 86% respectively and the mean size of renal calculi not visualized on USG was 3.5 mm ± 2.7 mm. Our study showed that the accuracy of USG in detecting renal, ureteric and urinary bladder calculi was 68%, 80% and 99% respectively

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