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High-resolution magnetic resonance (MR) imaging plays a pivotal role in the pretreatment assessment of primary rectal cancer. The success of this technique depends on obtaining good-quality high-resolution T2-weighted images of the primary tumor; the mesorectal fascia, peritoneal reflection, and other pelvic viscera; and superior rectal and pelvic sidewall lymph nodes. Although orthogonal axial high-resolution T2-weighted MR images are the cornerstone for the staging of primary rectal cancer, high-resolution sagittal and coronal images provide additional value, particularly in tumors that arise in a redundant tortuous rectum. Coronal high-resolution T2-weighted MR images also improve the assessment of nodal morphology, particularly for superior rectal and pelvic sidewall nodes, and of the relationship between advanced-stage tumors and adjacent pelvic structures. Rectal gel should be used in MR imaging examinations conducted for the staging of polypoid tumors, previously treated lesions, and small rectal tumors. However, it should not be used in examinations performed to stage large or low rectal tumors. Diffusion-weighted imaging is useful for identifying nodes and, occasionally, the primary tumor when the tumor is difficult to visualize with other sequences. Three-dimensional T2-weighted imaging provides multiplanar capability with a superior signal-to-noise ratio compared with two-dimensional T2-weighted imaging.

Computed tomography (CT) plays an important role in evaluation and management of primary renovascular disease. Nonenhanced CT is useful for demonstrating renal hemorrhage, renal parenchymal or vascular calcifications, and masses. Contrast material-enhanced CT is essential to identify global or regional nephrographic abnormalities resulting from the vascular process (eg, renal infarcts, ischemia secondary to renal artery stenosis, arteriovenous communications). In addition, renal manifestations of a systemic disease (eg, vasculitis, thromboembolic disease) can be seen at CT. In trauma, occlusion of the main renal artery can be accurately diagnosed with contrast-enhanced CT. In cases of spontaneous renal hemorrhage without an apparent cause (eg, vasculitis, coagulopathy), a careful CT study should be performed to exclude renal cell carcinoma. The presence of fat in a hemorrhagic renal mass larger than 4 cm in diameter is characteristic of angiomyolipoma complicated by hemorrhage. Acute renal vein thrombosis appears as a clot in a distended renal vein, whereas renal vein retraction with collateral vessels is highly indicative of chronic thrombosis. Helical CT, especially with multiplanar two-dimensional and three-dimensional reconstruction following an intravenous injection of iodinated contrast material, has greatly improved our ability to directly image the proximal renal arteries and detect vascular lesions.

No abstract

This study demonstrates that the chemical composition of urinary calculi can be accurately determined by CT scanning in an in vitro setting.