For a patient of known weight, one can calculate the iodine dose needed to provide a desired level of hepatic enhancement. Use of a contrast material with a concentration of 240 mg L/mL is not recommended for dynamic incremental hepatic CT, except in small patients (eg, those weighing less than 73 kg).

No abstract

In hyperechoic renal masses, the presence of shadowing, a hypoechoic rim, and intratumoral cysts are important findings that may help distinguish AML from RCC.

Color Doppler ultrasound was used to image the ureteral jets in 17 healthy subjects and 26 patients with ureteral calculi proved with intravenous urography. In patients with ureteral calculi, three patterns of ureteral jets were seen: no detectable urine flow from the symptomatic side (12 patients), low-level continuous flow from the symptomatic side (four patients), and periodic ureteral jets on the symptomatic side that were not significantly different from ureteral jets of healthy subjects (10 patients). Of the 12 patients with high-grade obstruction on urograms, 11 had ureteral jets significantly different from those of healthy subjects (either no detectable ureteral jets or continuous low-level jets on the symptomatic side). Only three of the 11 patients with low-grade obstruction or nonobstructing stones had ureteral jets that were different from those of healthy subjects. It is concluded that analysis of ureteral jets with color Doppler can enable detection and qualitative determination of the degree of ureteral obstruction in many patients with unilateral ureteral calculi.

Recent reports have indicated that hyperechoic renal cell carcinomas (RCCAs) are more frequent among small cancers and that small cancers are being detected more frequently. To determine whether these trends have resulted in a change in the frequency of detection of hyperechoic RCCA and, in particular, in the frequency of RCCA mimicking angiomyolipomas (AMLs), the sonographic features of 90 pathologically proved RCCAs in 82 patients were retrospectively reviewed and correlated with tumor size. Tumor echogenicity was compared with that of normal renal parenchyma and classified as hypoechoic, isoechoic, slightly hyperechoic, or markedly hyperechoic. Thirty-one tumors were 3 cm in diameter or less, and 59 were larger than 3 cm. Ten (32%) of the tumors 3 cm in diameter or less were markedly hyperechoic and mimicked AMLs, whereas only one (2%) of the tumors larger than 3 cm had this appearance (P < .001). Eleven of the 90 tumors (12%) were markedly hyperechoic. Twenty-four (77%) of the small tumors were either slightly or markedly hyperechoic, compared with 19 (32%) of the larger tumors (P < .001). Because of the increased detection of small RCCAs in recent years, the number of hyperechoic cancers and the number of cancers mimicking AMLs have increased.

To determine the effect of contrast medium injection rate and biphasic versus uniphasic bolus on hepatic parenchymal enhancement at computed tomography (CT), 105 patients were randomized into four protocols. Hepatic and aortic enhancement curves were measured for each protocol. The optimal scanning interval (the duration between onset of a desired hepatic enhancement threshold and decline of enhancement below the threshold or onset of the equilibrium phase) and contrast enhancement index (CEI) (area under the hepatic enhancement curve above a desired threshold during the nonequilibrium phase) were the primary determinants of merit. Measurements were performed at hepatic enhancement thresholds between 10 and 60 HU. At most thresholds of hepatic enhancement, optimal scanning intervals were significantly longer and CEIs were significantly higher for the biphasic protocols than for the uniphasic protocols (P < .03). A biphasic injection with a high initial flow rate produces high peak contrast enhancement but delayed onset of equilibrium and thus provides a longer optimal scanning interval.

Current patterns of imaging utilization lead to frequent serendipitous discovery of renal lesions. Today, the majority of solid renal masses that are ultimately proved to be renal cell carcinomas were incidental findings on imaging studies performed for non-urinary tract symptoms. While earlier discovery has led to treatment of smaller and earlier-stage malignancies, the percentage of benign lesions discovered has also increased. A strategy for characterization of solid masses in adults based on the lesion's growth pattern, the "ball" versus the "bean," is presented. Common and uncommon renal masses, in concert with clinical and other imaging clues, are reviewed within the context of a renal ball or bean.

Extracorporeal shock wave lithotripsy (ESWL not equal to) is the optimal therapy for renal calculi less than 2 cm. in diameter and for proximal ureteral calculi. Controversy continues over the initial approach to distal ureteral calculi (that is below the bony pelvis): in situ ESWL versus ureteroscopy. Since February 1990, 76 distal ureteral calculi were treated at our institution using either in situ ESWL (Dornier HM3 ESWL with a Stryker frame modification in 27 patients or Siemen's Lithostar electromagnetic ESWL in 22) or ureteroscopy (27 patients). Patient age and stone size were similar among the groups. All ESWL treatments were performed with the patient under intravenous sedation and on an outpatient basis. Stone-free rates were 96% for the HM3 device, 84% for the Lithostar and 100% for ureteroscopy. Retreatment was required in 3 Lithostar cases (14%) and 1 HM3 case (4%). When compared to ESWL ureteroscopy for distal ureteral stones was more time-consuming, entailed routine placement of a ureteral stent, often required general anesthesia, more often led to hospitalization and doubled the convalescence period. From a cost standpoint, ESWL on an HM3 unit was a few hundred dollars more expensive than ureteroscopy. In summary, we believe that in situ ESWL provides optimal first line therapy for distal ureteral calculi, while ureteroscopy is better reserved as a salvage procedure should ESWL fail.