The clinical usefulness of power Doppler imaging for diagnosing various renal diseases was evaluated.
Subjects were 10 volunteers with normal kidneys, 2 patients suspected of having tumors with renal lobulation, 7 with transplanted kidneys (4 in whom the renal function could be evaluated serially starting immediately after transplantation and 3 in whom chronic rejection was suspected), 2 with renovascular hypertension, 1 with renal infarction, 4 with renal cell carcinoma, and 1 with metastatic renal tumor. Both velocity-
and power-mode color Doppler imaging were used to compare all subjects. The instrument, a GE LOGIQ
500, was equipped with 3.5 MHz and 5 MHz convex probes. Observation in velocity mode was followed by observation in power mode. A scale of ±7 to 10 cm/sec was used in velocity-mode imaging, and, to avoid artifacts, maximum color gain was used. Capability of color Doppler imaging to delineate renal cortical vessels
in normal kidneys was assessed, and the images obtained were compared with those obtained from patients
with renal disorders in order to evaluate the potential usefulness of this modality as a diagnostic tool. Results are as follows. In normal kidneys, power mode delineated a larger number of renal cortical vessels and
delineated them as far down as the subcapsular structure. This mode even delineated perforating branches
that could not be visualized in velocity mode. In the 2 patients suspected of having tumors with renal lobulation, power mode delineated normally running interlobar and interlobular arteries, making differentiation
from tumor tissue easier. In transplanted kidneys, velocity mode produced no demonstrable difference between delineation of renal cortical vessels in the event-free, good course and those in the acute tubular necrosis (ATN) stage. In power mode, however, renal cortical vessels were distinctly delineated in color, even in
the subcapsular area, during the good course. In the ATN stage, they were only poorly delineated, however.
The capability of color Doppler imaging to delineate renal cortical vessels was poor in cases of chronic rejection, where these vessels had the appearance of withered branches. Although diagnosis was possible with either mode, the power mode was superior in its ability to delineate renal vessels. In renovascular hypertension, both modes were equally effective in diagnosing one of the cases of renal arterial stenosis; power-mode imaging proved superior in the other. In the former case, a jet stream that was visualized at the site of
stenosis made diagnosis by velocity mode easy.
In the latter case, however, in which there was local stenosis
at the origin of the renal artery, an apparent abnormality that went undetected in velocity mode was identified in power mode. Power mode also proved superior in capability to visualize an avascular area in renal infarction. In the 4 cases of renal cell carcinoma, power mode was superior to velocity mode in capability to
delineate tumor vessels. Although velocity mode produced a rich color image of the lesion, the vessels delineated in this mode lacked continuity, while power mode delineated a tortuous and meandering pattern of tumor vessels. Both modes demonstrated metastatic renal tumor as an avascular lesion. These results suggest
that power-mode will improve the diagnostic capability of color Doppler imaging for an array of renal diseases. We predict that it will gain general acceptance as a diagnostic modality for these disorders.