Renal resistive indexes: variability in Doppler US measurement in a healthy population

PURPOSE

To determine the variability in resistive index (RI) in normal kidneys, possible causes of variability, and consequences of reporting a single value.

MATERIALS AND METHODS

Doppler ultrasound RI measurements were obtained in the upper, middle, and lower regions of 118 kidneys in 58 healthy subjects (aged 24-70 years; 35 women, 23 men) who subsequently underwent angiography. The effects of sampling a particular parenchymal region, vascular territory, or kidney were assessed.

RESULTS

Kidney region, vascular territory, and right versus left kidney had no consistently significant effect (P < or = .05) on RI. Age had a statistically significant effect. RI readings were highly correlated with each other both within a subject and within a kidney. The probability that a single RI value would exceed 0.70 in a healthy 45-year-old subject was 6%; this decreased to 3% when three readings were averaged.

CONCLUSION

The variability of RI measurements in a kidney suggests that a number of RI readings should be averaged before a single representative value is reported.

Doppler evaluation of renal artery stenosis: interobserver agreement in the interpretation of waveform morphology

OBJECTIVE

Analysis of Doppler waveform morphology for features of the tardus-parvus phenomenon has been promoted as a useful and accurate means for detecting renal artery stenosis. The purpose of this study was to examine and quantify the interobserver agreement of such an analysis and to determine if interobserver differences limit the value of this approach for predicting renal artery stenosis.

SUBJECTS AND METHODS

Four observers independently categorized renal artery waveforms of 47 patients (94 kidneys) clinically selected for renovascular hypertension. Waveforms were classified into five categories based on the presence and severity of tardus-parvus changes in the systolic upstroke and early systolic peak. This categorization was then compared with angiographic findings, and the results were analyzed with receiver-operating-characteristic curves. Kappa statistics and agreement tables were computed to evaluate interobserver agreement.

RESULTS

Interobserver agreement in the waveform analysis for the four interpreters was statistically significant (p < 0.001). The receiver-operating-characteristic areas produced by the observers indicated, however, that such waveform classification was not strongly predictive of renal artery stenosis.

CONCLUSION

We conclude that substantial agreement in the interpretation of waveform morphology can be obtained between independent observers, and that such differences that do exist do not preclude the use of the pattern-recognition approach to waveform analysis. Even so, the specific application of this strategy to the waveform contours of early systole was not successful in predicting the presence or severity of renal artery stenosis.

Renal artery stenosis: analysis of Doppler waveform parameters and tardus-parvus pattern

PURPOSE

The utility of Doppler parameters and waveform contour analysis for diagnosis of renal artery stenosis was studied in a hypertensive population screened for renovascular hypertension.

MATERIALS AND METHODS

The Doppler results were compared with those obtained with angiography in a prospective double-blind study involving 118 kidneys in 46 patients with hypertension and 11 potential renal donors with normal blood pressure. Doppler parameters measured in the distal renal artery included systolic acceleration, acceleration time, peak systolic velocity, deceleration in late systole, pulsatility and resistivity indexes, and waveform features in early systole.

RESULTS

Angiograms demonstrated 28 stenotic renal arteries. There was no significant difference between stenotic (> 50% diameter narrowing) and nonstenotic renal arteries for any parameters studied. When stenosis was further categorized as moderate (50%-79%) or severe (80%-95%), significant (P < .05) differences for acceleration time and systolic acceleration were found between nonstenotic and severely stenotic arteries.

CONCLUSION

Doppler characterization of the tardus-parvus phenomenon in the distal renal artery is not an adequate screening method for detection of renal artery stenosis.

Macrovascular pulmonary arteriovenous malformations demonstrated by radionuclide method

Pulmonary arteriovenous malformations (AVMs) are abnormal vascular communications that allow unoxygenated blood to pass from the venous to the arterial circulation. Usually congenital in origin and twice as likely in women, hemoptysis, dyspnea, and chest pain are the common presenting complaints in AVM. A case of pulmonary AVMs that were demonstrated on a radionuclide angiogram is presented. Pulmonary AVMs were suspected after finding radioactivity in both kidneys on a perfusion lung scan.

Morphine-augmented cholescintigraphy with a false-negative result and an apparent ectopic gallbladder

Morphine-augmented cholescintigraphy has been shown to be a highly sensitive and specific means of evaluating acute cholecystitis. False-negative results do occur infrequently, however, and such a case is reported. In addition, this case initially demonstrated an apparent ectopic gallbladder, and thus anomalies in location of the gallbladder will be discussed.

Indium-111 imaging of an inflammatory abdominal aortic aneurysm

Indium-111-labeled leukocyte scanning has been shown to be a highly sensitive and specific imaging modality in the detection of abscess formation. Leukocyte infiltration occurs in a variety of inflammatory states as well as some noninflammatory states, leading to false-positive results. We report a case of an inflammatory abdominal aortic aneurysm imaged by 111In. It is not clear whether the activity noted is due to the inflammatory nature of the aneurysm or to hemorrhage present within the wall of the aneurysm.