الفهرس 
AnatomyOnly 14 pages are availabe for public view
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Abstract
Tumors of the kidney account for about 3% of all malignant tumors of the body. RCC is the most common primary renal malignant neoplasm in adults. It accounts for approximately 90% of renal tumors and 2% of all adult malignancies. One fourth to one third of patients present with metastatic disease. In recent years, tumors are being discovered at an earlier stage, possibly due to increased use of medical imaging in general. Other malignant renal tumors include TCC, lymphoma, metastases, sarcomas and Wilm’s tumor (the most common malignant renal tumor in children).
Conventional radiography is rarely used to diagnose a renal mass. Accidentally, we may suspect the presence of a renal tumor in abdominal radiographs done for other causes (loss of the psoas margin, displacement of retroperitoneal fat, presence of calcification and presence of an expansile ball shaped mass extending from the kidney raise the suspicion). Picture of renal tumors on IVU are non-specific and include mass effect on the collecting system, distortion of the renal contour, enlargement of a portion of the kidney and calcification.
The widespread use of abdominal US has aided in the early detection of renal tumors discovered incidentally on US for other causes. It can differentiate solid masses from simple cysts. It is non invasive, painless and does not involve irradiation. However, it is still limited in staging and giving final diagnosis of the nature of the tumor. CEUS has become increasingly important because it can clearly resolve small tumor vessels; it is safe for patients with impaired renal function because of the absence of urinary excretion of the contrast agent. Moreover, the technique is not contraindicated for patients with pacemakers or arthoprostheses, is less expensive than CT and MRI, and does not entail use of ionizing radiation. But still the presence of bowel gas limits the effectiveness of US. Endoscopic ultrasound allows examination and biopsy of masses within the kidney, thus facilitating the diagnosis of early RCC.
CT plays a central role in the evaluation of a patient with a suspected renal mass; it can be used to detect and stage RCC and to provide information for surgical planning of renal tumors. Helical CT has improved the diagnosis of renal masses by decreasing the potential limitations of partial volume averaging and respiratory misregistration. Currently, the CT technique recommended for detection and staging of renal cell carcinoma is a multiphase protocol, which includes unenhanced CT followed by corticomedullary and nephrographic phase imaging of the kidneys. MSCT allows faster data acquisition times when compared with single-detector CT, with no loss in image quality thus helping reduce the motion artifact. CTU has demonstrated excellent sensitivity in detecting upper tract uroepithelial neoplasms. But still CT has two major disadvantages, the use of intravenous contrast media and the irradiation to the patient.
MRI is a powerful and versatile tool for single modality evaluation of potential renal malignancies. A well-planned high field MRI examination can simultaneously detect and characterize renal tumors. MRI generates the highest intrinsic soft tissue contrast of any cross-sectional imaging modality. The main MRI feature indicating potential malignancy of a renal tumor is enhancement after intravenous gadolinium administration. MRU has evolved to become a serious clinical alternative to conventional IVU and CTU. Analysis of tumor vascularity by MRA and MRV helps in recognition of all malignancies, including renal cancer. When IVC involvement is suspected, either inferior venacavography or MR angiography is used. Diffusion weighted MRI is able to differentiate between normal and neoplastic renal parenchyma. MRI is limited by patient cooperation because MRI is more sensitive to motion artifact than CT.
Most imaging modalities yield purely anatomic and morphologic tumor details without addressing tumor metabolism. The advent of PET and PET/CT has provided tumor-related qualitative and quantitative metabolic information critical to patient diagnosis and management. Its sensitivity for detecting metastatic lesions is better than for determining the presence of cancer in the renal primary site.
Image-guided renal mass biopsy procedures can be performed using CT, US, MRI or less commonly, fluoroscopic guidance. The most common indications are tumors that do not have the typical radiologic features of RCC, Bosniak category III or IV cystic lesions, locally advanced or metastatic RCC and non-surgical tumors.
RFA is increasingly more being used for the treatment of renal lesions in patients who are poor surgical risks or who refuse surgery, also in patients with a solitary kidney and as an alternative to nephron-sparing surgery. The size of a renal tumor, its location within the kidney, and the proximity of adjacent structures should be considered when evaluating a tumor for possible ablation. The procedure can be performed laparoscopically under US guidance, open under US guidance or percutaneously under US, CT or MRI. Other ablation techniques include cryoablation, HIFU, microwave and laser ablation.
Transarterial embolization is an accepted therapeutic option for palliation of renal cancer with very high success rate and low complication rate.
In conclusion, CT is the gold standard for diagnosis of malignant renal tumors, a multiphase protocol must be used.