Role of Computed Tomography in Differentiation of Radio-Lucent Stones from Radio-Opaque Stones in The Renal System Depending on Attenuation Measurements (Hounsfield Unit)

Renal calculus remains to be a common problem in the hospital. It is the third most common urological problem after urinary tract infection and prostate disease Computed tomography (CT) has a superior sensitivity and specificity over all other modalities in Diagnosis of renal stones in determining the size and number of kidney stones, no matter how small it is, also it helps in the identification of Hounsfield unit (HU) and thus determines the composition of gravel. Aim: The aim of this study is to differentiate between radio-opaque from radio lucent stones depending on attenuation measurements of the Hounsfield unit (HU) and to find the cutoff value depending on the Hounsfield unit in computed tomography (CT). PATIENT


INTRODUCTION
Kidney stones (renal calculi) are solid masses made of crystals.Kidney stones originate in the kidneys but can be found at any point in the urinary tract.The urinary tract includes the kidneys, ureters, bladder, and urethra [1,2].
Renal calculus remains to be a common presentation in the hospital.It is the third most common urological problem after urinary tract infection, with a lifetime prevalence of Urolithiasis at 10-15%.The prevalence has risen over 20 years from the mid-1970s to the mid-1990s.The diagnosis of urolithiasis is largely dependent on analysing the clinical presentation and physical examination.Suspicion is confirmed with radiologic tests [3,4,5], particularly the non-contrast-enhanced computed tomography (CT) scan.The advent of non-enhanced CT has not only provided detection and confirmation of calculi but also accurate detection of its size and location.Non-contrast helical CT scan provides several advantages over the KUB radiograph such as detection of radiolucent calculi, sensitivity for small stones, identification of other causes of flank plan as well as avoidance of any preparation prior to the procedure.However, a KUB radiograph has remained part of the protocol for most clinicians even after a non-contrast helical CT scan is carried out because of its impact in clinical decision-making prior to treatment.Due to the higher radiation dose with CT, conventional or digital radiography is being used to monitor the passage of stones if radiographic follow-up is believed to be indicated [6,7,8] Nephrolithiasis occurs in all parts of the world.The lifetime prevalence of nephrolithiasis is approximately 12% for men and 7% for women in the United States, and it is rising.Having a family member with a history of stones doubles these rates.Approximately 30 million people are at risk in the United States.Roughly 2 million patients present on an outpatient basis with stone disease each year in the United States, which is a 40% increase from 1994 [9].The incidence of urinary tract stone disease in developed countries is similar to that in the United States; the annual incidence of urinary tract stones in the industrialized world is estimated to be 0.2%.Stone disease is rare in only a few areas.
Most urinary calculi develop in persons aged 20-49 years.Peak incidence occurs in people aged 35-45 years, but the disease can affect anyone at any age.An initial stone attack after the age of 50 years is relatively uncommon.Nephrolithiasis in children is rare.[10] Urolithiasis is more common in males (male-to-female ratio of 3:1).Stones due to infection are more common in women than in men.
Approximately 80-85% of stones pass spontaneously.Approximately 20% of patients require hospital admission because of unrelenting pain, proximal UTI, or inability to pass the stone [11.12]A study done in Iraq showed that Epidemiology and pathogenesis in urinary stones predominantly of mixed type: calcium oxalate was the commonest compound.Anatomical distribution of urinary stones shows that renal stones are more common than Urolithiasis and bladder stones.

DATA COLLECTION
Full clinical history was taken from all patients included in this study.All the patients were submitted to the plain X-ray of the abdomen (KUB) and non-enhanced CT of the abdomen.

Plain X-Ray of the abdomen (KUB-(kidney, ureters, bladder))
KUB was performed to all patients after preparation, which is: 1.Before one day from examination, the patient was asked to take an early dinner and 1-2 spoons of castor oil to avoid gasses shadow in the KUB X-ray.
2. The examination is performed in a supine position, and ask the patient to take a deep breath.The X-ray field extends from the pubic Asymptotic to the superior aspect of the kidney.The exposure factor was-(80-100 kv, 60MAs), and this exposure factor according to the patient built.
The following parameters were studied by KUB examination: 1. Size of stone.2. Appearance of stone (radio-lucent or radio-opaque).
•The study focused on the renal stone that measures l0 mm or more.

Computed Tomography (CT)
The examination was performed in a CT unit with Som atom definition AS 64 slice Siemens medical system Germany.A non-enhanced scan was performed to all I. II.7 Discussion CT is one of the best methods to detect kidney stones.All stones can be detected on CT except very rare stones composed of certain drug residuals (e.g., acyclovir In recent years, the use of helical non-contrast computed tomography (CT) in patients with urinary system stones has increased.Hounsfield units (HU), a parameter generated from standard CT, are related to the density of the stone or structure of interest.HU can also be used to assess the CT density of urinary system stones.It has become an important diagnostic tool, not only for predicting the type of stone but also for determining the appropriate mode of treatment [13,14].

III. ARE
In our study, we try to determine the best cut-off value of the Hounsfield unit in order to differentiate between Radio-Opaque and Radio-Lucent stones to help the urologist to determine the type of treatment, either surgical or medical.[15] In our study, we have 100 stores in 100 patients (65 male,35 female)dealt with sizes more than or equal to 10mm.We find 71 radio-opaque with a mean value of HU 914.Study of Sfoungaristos (2014) [18]focused on size gravel 9.7mm with sample size 375 (206 radioopaque, 169 radio-lucent, the best HU cut off value was 772.
Differences in results may be due to differences in the size of the gravel in the studies or because of the different environment or, the differing nature of the diet, or other factors which led to the different components of gravel [19,20].
We discussed the effect of gender on the appearance of gravel; in this aspect, the study agreed with a number of studies by Liapis and David, such as that showed that most of Radio-opaque stones are found in males while most of Radio-lucent stones are found in females.

Conclusion
1. Based on the constructed ROC curve, a threshold value of 573 in CT was established as a cut-off value in determining whether a calculus is a Radio-Opaque or Radio-Lucent.
2. Most of the Radio-Opaque stones were found in males, while of most of the Radio-Lucent stones were found in females.
/© 2024 The Authors.Published by Academic Journal INC.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/) 3 STUDY DESIGN AND PERIOD The study was a cross-sectional analytic study extended from September 2014 to June 2015 STUDY SAMPLE The study was conducted in the department of diagnostic radiology in Al-Emammain Al-Kadhymain Medical City, Baghdad, Iraq.One hundred patients (65 males and 35 females) All the patients included in this study are sent from the urology department, and they have renal stones equal to or more than l0mm in diameter as shown by the U/S examination.Exclusion criteria 1. Patient age (less than l8 and more than 80 years).2. Stone size (more than or equal to 10 mm). 3. pregnancy 4. Patient with Barium contrast study within three days before the examination.
Figure1-receiver operating characteristic curve to determine Hounsfield unit (HU) 573 as the best HU cut-off value for identifying radio-opaque stones from radio-lucent stones on computed tomography 87 and Std.Deviation 207.69, 29 with mean value of HU 461.21 and Std.Deviation 207.96, 29 Tauro Deviation 139.85.by using the Receiver Operating Characteristic curve (ROC), we determined the best HU cut-off value is 573 with sensitivity 97.2% and specificity 93.1% Previous studies done by researchers, such as the study of Chau (2012) [16,17], focused on size gravel 8.4mm with sample size 184 (121 radio-opaque with a mean value of HU 816.51 and Std.Deviation is 274,63 radio lucent with a mean value of HU 358.25 and Std.Deviation 156, whereas the best HU cut-off value was 498.5 with a sensitivity of 89.3% and specificity of 87.3% -Study of Chau (2014) focused on size gravel 7mm with sample size 203 (126 male,77 female.The best HU cut-off value was 610, with a sensitivity of 82.9% and a specificity of 93.9%.

Table ( 3
) Observed values And Expected values of Radio-Opaque and Radiolucent according to their gender. ISSN: