Grade I hydronephrosis: pulsed Doppler US evaluation

This study was undertaken to determine whether the presence of blood vessels could mimic the appearance of grade I hydronephrosis on sonograms and thus cause false-positive readings. One hundred consecutive patients with grade I hydronephrosis were examined. Sample volumes were obtained with pulsed Doppler ultrasonography (US) at the site of the greatest separation of the central renal sinus echoes to determine if the separation was fluid accumulating in the collecting system, as in obstruction, or if the separation was actually caused by vessels that mimic hydronephrosis. Vascular structures accounted for the separation of the sinus echoes in 43% of patients. In patients 12 years of age or younger, this frequency rose to 61%. The simple procedure of evaluating the renal sinus echo separation with pulsed Doppler US should decrease the frequency of false-positive diagnoses of hydronephrosis and thus diminish the need for further confirmatory testing.     

Hepatocellular carcinoma: evaluation with color Doppler US and MR imaging.

Fifteen patients with hepatocellular carcinoma underwent examination with color Doppler ultrasound (US), magnetic resonance (MR) imaging, dynamic computed tomography (CT), and angiography. Doppler signals ranging from 0.22 to 3.48 kHz could be obtained from within the tumor in 14 of 15 patients. The resistive index was 0.38-0.77. Color Doppler signals were visualized in nine of 15 lesions with a Doppler shift greater than 0.7 kHz. The Doppler signals and the resistive index of the tumor vessels became lower as the vessels progressed into the center of the lesion. The appearance of tumor vessels recognized on MR images obtained with gradient-recalled acquisition in the steady state (GRASS) in 11 of 15 lesions was compared with that on CT scans and angiograms. Tumors that were hyperintense on GRASS images obtained with a flip angle of 15 degrees transmitted Doppler signals of considerably higher amplitude compared with the isointense lesions. Both color Doppler US and MR imaging provided useful information for characterizing intratumoral blood flow.     

Ureterovesical jets in infants and children: duplex and color Doppler US studies

Ureteric jets were studied with conventional duplex Doppler (79 patients) and with color Doppler flow imaging (22 patients). Correlation with voiding cystourethrography (VCUG), performed ont he same day, was obtained in all patients. Thirty-six patients with normal VCUG results and normal renal and bladder ultrasound (US) studies served as the control group for 39 patients with vesicoureteric reflux (VUR) and 26 patients with urinary tract disorders other than reflux. The site of the ureteric orifice and duration, direction, and turbulence of the jets were recorded. Duration varied from 0.4 sec to 7.5 sec and depended largely on fluid intake. Duration varied in an individual patient by up to 2 sec from one jet to another. The direction of the normal jet was anteromedial and upward. Jets from refluxing ureters can appear normal. Severe renal parenchymal scarring reduced frequency and amplitude of the jets. Doppler analysis of the ureteric jet does not allow diagnosis or exclusion of VUR. Color Doppler was more sensitive in demonstrating ureteric jets than was gray-scale, real-time US and facilitated the study, but it was equally unable to help predict reflux.     

Renal transplant pyelocaliectasis: role of duplex Doppler US in evaluation

To distinguish the obstructed from the nonobstructed dilated collecting system of transplanted kidneys without interventional diagnostic measures, the authors prospectively evaluated duplex Doppler analysis (determination of resistive index [RI]) in 35 renal transplant patients with pyelocaliectasis. Proof of the presence or absence of obstruction was obtained at interventional procedures in 18 patients and at clinical follow-up in 17. Thirteen kidneys were obstructed (mean RI, .81 +/- .06), while 22 had nonobstructive dilatation (mean RI, .66 +/- .07). The RI difference was statistically significant (P less than or equal to .01). Of 21 kidneys with a normal RI, only two had obstruction. In both of these, the obstruction was associated with a significant peritransplant collection of fluid due to a ureteral leak. In the seven obstructed transplanted kidneys with follow-up, the mean RI was .82 +/- .06 before nephrostomy and .67 +/- .05 after nephrostomy. Obstruction was a common cause of an elevated RI (greater than or equal to .75). Other causes of transplant dysfunction can be associated with an elevated RI and nonobstructed dilatation. More important, a normal RI should strongly argue against obstruction unless a ureteral leak is also present.     

Hepatic vein stenosis after living donor liver transplantation: evaluation with Doppler US

PURPOSE: To determine the spectral Doppler ultrasonographic (US) findings that would indicate hepatic vein stenosis after living donor liver transplantation (LDLT). MATERIALS AND METHODS: The authors retrospectively reviewed postoperative Doppler US images of the hepatic veins in 113 consecutive patients who underwent LDLT. Doppler US was performed 1-25 times (mean, 5.2 times) during 1-433 days after LDLT. Nineteen patients who were inadequate for analysis were excluded; thus, 94 patients (72 male patients and 22 female patients; mean age, 40 years) were included in the study. Patients with more than 10 mm Hg of pressure gradient between the hepatic vein and the inferior vena cava were considered to have substantial hepatic vein stenosis (stenosis group). Those without substantial stenosis (control group) included patients with no clinical or radiologic evidence of hepatic vein stenosis for at least 3 months after LDLT. The wave pattern and peak flow velocity of the hepatic veins were compared between the groups. RESULTS: Five patients (5%) had substantial hepatic vein stenosis: three had persistent monophasic wave patterns at all US examinations, and two had monophasic wave patterns at most US examinations and biphasic or triphasic wave patterns at 6- and 9-day follow-up examinations. In the control group, 52 (58%) of 89 patients had a persistent triphasic or biphasic wave pattern and 37 (42%) had a monophasic wave pattern at one or more US examinations; this included two patients with persistent monophasic wave patterns. A monophasic wave pattern was more frequent in the stenosis group than in the control group (P =.015). There was no significant difference between the velocities of the hepatic veins in the stenosis group (22.3 cm/sec +/- 9.6 [SD]) and those in the control group (37.5 cm/sec +/- 20.3) (P =.14). CONCLUSION: A persistent monophasic wave pattern on Doppler US images of the hepatic veins is suggestive of, but not specific for, substantial hepatic vein stenosis after LDLT. A persistent triphasic wave pattern on Doppler US images can exclude the possibility of substantial stenosis.     

Power Doppler US: evaluation of the morphology of stenoses with a flow phantom

PURPOSE: To determine the importance of technical settings at power Doppler ultrasonography (US) for the evaluation of stenoses. MATERIALS AND METHODS: A computer-controlled phantom was used to induce a reproducible flow across a calibrated 71% stenosis in an 8.4-mm-diameter tube. Two transducers, 2-4 and 5-10 MHz, working at depths of 3.0 and 11.5 cm, respectively, with different beam angles (40 degrees, 60 degrees, and 90 degrees ), were used to simulate evaluation of pulsatile flow across normal and stenotic vessels in various conditions. For each condition, gain, pulse repetition frequency, and wall filter were progressively turned from low to high values. Two observers measured in a blinded fashion the apparent lumen of the stenotic and normal vessels on longitudinal and transverse images with the use of power Doppler US. RESULTS: When the high-frequency transducer was used, gain significantly affected both stenotic and feeding vessel measurement, whereas pulse repetition frequency and filter only affected feeding vessel evaluation. When the low-frequency transducer was used, all factors, including flow velocity and beam angle, played a significant role (P <.001). In most conditions, overestimation of the lumen and underestimation of the lumen of the feeding vessel led to severe underestimation of the degree of stenosis. CONCLUSION: Power Doppler US cannot be used to measure stenoses accurately. Underestimation of the degree of the stenosis was significantly higher with the low-frequency probe than with the high-frequency probe.     

Renal allograft rejection: evaluation by Doppler US and MR imaging

A prospective study compared the efficacy of Doppler ultrasonography (US) and magnetic resonance (MR) imaging in evaluating 38 renal allografts, with specific attention to transplant rejection. Forty-three Doppler US and 42 MR examinations were performed and interpreted. Histologic correlation was obtained from 22 biopsy or nephrectomy specimens. Clinical correlation or a response to instituted therapy was used as confirmation in the remaining allografts. Accuracy in identifying cyclosporine toxicity or acute tubular necrosis could not be evaluated because there were few such cases, with concomitant rejection in most. The ability to predict and identify presence or absence of rejection was not affected by different serum creatinine values. Doppler US was significantly superior to MR imaging in identifying allograft rejection, demonstrating a higher sensitivity (95% vs. 70%), specificity (95% vs. 73%), and accuracy (95% vs. 71%). Because of its low cost and accessibility, Doppler US should become the primary modality for renal transplant screening.