الفهرس 
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Abstract
Solid renal masses contain little or no liquid components, and when examined with CT, usually (but not always) consist of predominantly enhancing tissue. Enhancement is an important feature; the presence of unequivocal enhancement by CT signifies that the lesion has a blood supply and is solid. Solid tumors may be benign or malignant. Benign entities encountered in clinical practice include angiomyolipoma and oncocytoma. Renal cell carcinoma (RCC) is the most frequently occurring solid lesion within the kidney and the most common primary renal malignant neoplasm in adults. It accounts for approximately 90% of renal tumors and 2% of all adult malignancies. The incidence of RCC has been rising steadily over the past 50 years and approximately 30,000 new cases are now diagnosed in the United State annually.
Due to the increased detection of tumors by imaging techniques, such as ultrasound (US) and computerized tomography (CT), the number of incidentally diagnosed RCCs has increased. These tumors are more often smaller and of lower stage.
The past 2 decades have witnessed significant changes in the manifestation, diagnosis, and management of renal cell carcinoma. With the widespread use of cross-sectional imaging, as many as one-half of such carcinomas are discovered incidentally and many are early-stage lesions. Paralleling this clinical stage migration is a growing trend for more limited surgical resection, such as adrenal-sparing radical nephrectomy, laparoscopic nephrectomy, or nephron-sparing partial nephrectomy.
The challenges of renal tumor imaging include not only reliable differentiation between benign and malignant lesions but also accurate delineation of the extent of the disease to ensure optimal treatment planning.
Computed tomography (CT) is used for diagnosing, accurate characterization of nearly all renal masses as solid or cystic. In addition to the presence of a solid mass, perhaps the most important characteristic of the mass is the demonstration of enhancement following administration of IV contrast. In addition to defining the tissue characteristic of the lesion (solid versus cystic, enhancing versus non-enhancing), CT accurately estimates the size of the lesion and allows for precise visualization of adjacent structures such as perinephric fat, lymph nodes, adjacent organs, and vascular structures (renal vein and IVC). These data not only facilitate accurate clinical staging of RCC but also provide a road map for surgical planning.
Several improvements in CT imaging over the last two decades have brought about the current diagnostic accuracy of CT. Recent advances have been made in many areas, but the most significant changes have occurred in multislice CT. Multislice or spiral CT permits rapid imaging of kidneys during a single breath hold, which effectively eliminates respiratory misregistration. Power injection of iodinated contrast agents enables consistent tissue enhancement. Three-phase CT scans are commonly performed for detection, characterization, and staging of renal lesions. Enhancement characteristics on these scans can help to distinguish between different tumor types. Although ultrasound and magnetic resonance imaging have many indications for imaging renal tumors; CT, with new uses and improved diagnostic capabilities, remains the gold standard in renal imaging.
In staging renal cell carcinoma, the goal of any imaging study is to identify patients who have a resectable tumor and can be cured by means of surgical intervention. The extent of disease must be accurately delineated to allow optimal surgical planning.
Since the first introduction of 4-slice multislice computed tomography (MSCT) more than 10 years ago, MSCT imaging has achieved widespread acceptance and became a standard of care in routine clinical practice by offering high-speed, non-invasive, thin-slice diagnostic scanning for a wide range of clinical applications in radiology and cardiology. In the past year, the industry has witnessed an explosive increase in the amount of data obtained by MSCT and in the number at acquired slices to 32 and 64. While some experts have argued that a 16-slice system is sufficient from a practical standpoint, a closer examination of 32- and 64-slice systems offers new and superior clinical benefits over and above 16-slice technology, especially in imaging of the coronary arteries and in multiphase and functional studies.
Perfusion imaging with multislice CT is potentially useful in the differential diagnosis of renal mass this is due to the fact that different pathological types of renal mass have different perfusion characteristics.
To differentiate the subtypes of renal cell carcinoma the, degree of enhancement is the most valuable parameter. In addition to the presence or absence of cystic degeneration, vascularity and enhancement patterns can serve supplemental role in differentiating renal cell carcinoma subtypes, and this could help in preoperative identification of the renal cell carcinoma subtype and influence the degree of preoperative evaluation and extent of surgery, resulting in less aggressive surgery in patients with a subtype that tends not to metastasize or recur, such as chromophobe subtype. Thus, postoperative morbidity and mortality would be decreased, particularly in elderly patients.
The computed tomography (CT) discrimination of renal lesions bases on the presence of contrast enhancement during the nephrographic phase of contrast enhancement. For this reason, the standard practice in genitourinary CT includes both a non-contrast CT acquisition to assess baseline attenuation of renal masses as well as a contrast enhanced CT acquisition to measure contrast enhancement within the mass. The presence of unequivocal enhancement (>20 Hounsfield units) illustrates lesion vascularity, thereby confirming the diagnosis of a renal neoplasm.
This was a descriptive cross-sectional study conducted on 30 patients with clinical suspicion of renal masses; to evaluate the diagnostic value of computed tomography in differentiating solid renal masses and see if it is possible to differentiate between the benign and malignant lesions and is it possible to differentiate between the different subtypes of renal cell carcinoma. All patients have renal masses in routine US examination. We used abdominal ultrasonography and multislice CT examination for all cases.
In our study, the mean age of all patients was (56.7 ± 10.3) years. Regarding gender of the patients, (50%) of patients were males; and (50%) were females.
Our study showed that the average number of lesions was (1.3 ± 0.5). Regarding type of CT lesion, (66.7%) of patients had solid masses, and (33.3%) had cystic lesions. Regarding Bosniak classification for renal cysts, (10%) of patients had class I, (13.3%) had class II-F, (23.3%) had class III, and (53.3%) had class IV. Regarding side of CT lesion, (33.3%) of patients had bilateral lesions, (26.7%) had Lt-sided kidney lesion, and (40%) had Rt-sided kidney lesion. Regarding size of kidneys, (76.7%) of patients had enlarged kidneys. Regarding back pressure of kidneys, only (13.3%) of patients had kidney back pressure.
The average attenuation value (before enhancement) was (27.2 ± 9.04) Hu, average attenuation value (CMP) was (64.4 ± 21.7) Hu, average attenuation value (EP) was (84.4 ± 28.25) Hu. Regarding pattern of enhancement, (10%) of patients had homogeneous enhancement, (66.7%) had heterogeneous enhancement, and (23.3%) had peripheral enhancement.
Histopathologically, the average number of lesions was (28.94 ± 2.74), (66.7%) of patients had malignant lesions, while (33.3%) had benign lesions. Regarding type of RCC, (80%) of patients had clear cell RCC, and (20%) had papillary RCC, while nobody had chromophobe RCC. The 30 suspected renal mass patients were classified according to histopathology results into 2 independent groups: benign group (10 patients) and malignant group (20 patients).
Comparison revealed highly significant decrease in number of lesions and highly significant incresae in solid mass lesions, Bosniak class III and IV, single kidney lesions and kidney enlargement in malignant group; compared to benign group (p < 0.01). Also, this comparison revealed significant increase in size of lesion (Lt and Rt) and incidence of neo-vascularity, venous invasion, cystic degeneration and lymphadenopathy in malignant group; compared to benign group (p < 0.05).
Comparative study between the 2 groups revealed highly significant increase in attenuation value (before enhancement, CMP and EP) and heterogeneous pattern of enhancement in malignant group; compared to benign group (p < 0.01).
The 20 malignant RCC patients were further classified according to type of RCC results into 2 independent groups: clear cell RCC group (16 patients) and papillary RCC group (4 patients). Comparative study between the 2 groups reveale; highly significant increase in age and female gender in papillary RCC group; compared to clear cell RCC group (p < 0.01). Also, this comparison revealed significant increase in size of Lt-sided lesions in clear cell RCC group; compared to papillary RCC group (p = 0.008) and significant increase in cystic degeneration in papillary RCC group; compared to clear cell RCC group (p = 0.0076).
Comparative study between the 2 groups revealed significant increase in attenuation value (CMP) in papillary RCC group; compared to clear cell RCC group; with highly significant statistical difference (p = 0.0015).
To predict patients with malignancy by using ROC-curve analysis, attenuation value (before enhancement), at a cutoff point (>19) predicted patients with malignancy from patients without, with perfect accuracy, sensitivity= 100% and specificity= 100% (p < 0.01). At a cutoff point (>50), CMP predicted patients with malignancy from patients without, with perfect accuracy, sensitivity= 100% and specificity= 100% (p < 0.01). At a cutoff point (>62), EP predicted patients with malignancy from patients without, with perfect accuracy, sensitivity= 100% and specificity= 100% (p < 0.01).
To predict patients with clear cell RCC by using ROC-curve analysis, attenuation value (before enhancement) showed non-significant predictive values in discrimination of patients with clear cell RCC from patients without (p > 0.05). At a cutoff point (≤86), CMP predicted patients with clear cell RCC from patients without, with perfect accuracy, sensitivity= 100% and specificity= 100% (p < 0.01). At a cutoff point (>100), EP predicted patients with clear cell RCC from patients without, with fair accuracy, sensitivity= 75% and specificity= 100% (p = 0.02).
To predict patients with papillary RCC by using ROC-curve analysis, attenuation value (before enhancement) showed non-significant predictive values in discrimination of patients with papillary RCC from patients without (p > 0.05). At a cutoff point (>86), CMP predicted patients with papillary RCC from patients without, with perfect accuracy, sensitivity= 100% and specificity= 100% (p < 0.01). At a cutoff point (>100), EP predicted patients with papillary RCC from patients without, with fair accuracy, sensitivity= 100% and specificity= 75% (p = 0.02).