Helical CT of the urinary organs.

Despite of the diagnostic potential of conventional CT (CCT), limitations being inherent in this technology reduce its diagnostic confidence and limit clinical CT applications as 3D imaging. Helical CT (HCT) has far overcome the limitations of CCT and has become the standard CT technology. After a short overview on the technique of HCT and its advantages over CCT, the impact of HCT on the detection of disorders of the urinary organs is discussed. Due to the high quality of 3D reconstructions, vessels are visualized free of artefacts resulting in a dramatic improvement and acceptance of CT angiography, which has become a clinically important examination in the evaluation of obstructive renal artery disease. Fast HCT provides a precise assessment of the three phases of the nephrogram and it is a prerequisite for an improved depiction of abnormal vascular perfusion and impaired tubule transit of contrast material. Helical CT enables an improved characterization of cystic mass lesions reducing the diagnosis of indeterminate masses and thus facilitating a better therapeutic management. The diagnosis of renal cell carcinomas (RCC) has improved due to an increased sensitivity in detecting small RCCs, and an increased specificity in the diagnosis of neoplastic lesions. Improved staging of RCCs is the result of accurate assessment of venous tumour extension. When planning nephron-sparing surgery 3D display of the renal tumour helps to determine the resectability of the mass depicting its relation to major renal vessels and the renal collecting system. In the evaluation of renal trauma HCT provides shorter scanning time and thus fewer artefacts in the examination of traumatized patients who cannot cooperate adequately. Three-dimensional postprocessing modalities allow the assessment of the renal vascular pedicel by CT angiography and improve the demonstration of complex lacerations of the renal parenchyma. In the evaluation of the upper urinary tract unenhanced HCT has become the imaging method of choice in the diagnosis and differential diagnosis of acute flank pain since it is highly sensitive and specific in detecting calculus disease. Unenhanced HCT may furthermore demonstrate causes of flank pain unrelated to urolithiasis. Gapless volume scanning and improved resolution in the z-axis during the excretory phase enables improved visualization of the renal collecting systems and ureters, resulting in a better demonstration of intraluminal and extraluminal pathology.