The protocol will vary a bit based on the patients age and the clinical history of the patient as well as clinical presentation. For example was this a mass incidentally seen on an abdominal non-contrast CT or the workup of a AAA or a patient with hematuria. Each of the presentations will change your suspicion but the CT protocol must take all information into account. The protocol is optimized for lesion detection and classification as well as for trying to minimize radiation dose for the patient. Typically a non contrast scan of the kidneys is followed by an arterial phase at 35 sec (from diaphragm to symphysis), a venous phase at 70 seconds (diaphragm to iliac crest) and a delayed phase(4-5 minutes post injection) from diaphragm to symphysis. This protocol can be decreased on the arterial phase in patients 30 or younger (do not scan below iliac crest). Scans are reconstructed with thin sections (ideally .75mm ) and thick sections (3mm) and reconstructed at .5mm intervals for the thin sections and 3mm for the thick sections. Contrast volumes used are typically 100-120 cc of ioxehol or iodixanol.

1. Non contrast CTs are critical to see whether the CT attenuation is under 20HU, over 70HU and between 20-70 HU. The 20-70HU is the danger zone.
2. Multiphase acquisition optimizes lesion detection as well as determining etiology
3. A solid or solid/cystic renal mass that enhances up to 90HU is likely a papillary renal cell carcinoma
4. A solid or solid/cystic renal mass that enhances above 100HU (usually over 130HU) is likely a clear cell renal cell carcinoma
5. AMLs (angiomyolipoma) usually contain macroscopic fat but may contain microscopic fat and be more difficult to diagnosis. Lipid poor AMLs can be confused with papillary RCCs as they are not very vascular
6. Image display using multiplanar imaging is critical in lesion detection
7. 3D mapping with MIP, VRT and CR is valuable for pre-op planning including determination of partial nephrectomy candidates.
8. Delayed phase imaging is critical in detecting transitional cell carcinomas (TCC) of the kidney
9. Venous phase and delayed phase imaging are especially valuable for looking at venous invasion (renal vein and IVC) and collateral pathways
10. Renal masses under 1cm in size in older patients are routinely followed in most cases
11. Renal masses can be misclassified especially in cases of high density renal cysts which tumors can be called papillary RCC. The value of non-contrast CT can not be over emphasized.