Doppler ultrasound facilities allow identification of vessel anatomy and characterization of blood supply of and within the lesion. Spectral-wave-form analysis has capabilities to distinguish between arterial and venous flow, and to measure velocity as well as resistive index.
Current laparoscopic ultrasonography probes can use B-mode and Doppler (color Doppler and/or power Doppler with spectral Doppler flow analysis) functions simultaneously.
In color Doppler mode, movement of objects toward the probe typically is presented in red, while movement away from the probe is in blue.
In color Doppler mode, it is useful to determine flow direction and velocity. The advantage of power Doppler function is that blood flow sensitivity is increased by a factor of three to five times in comparison with conventional color Doppler function. Power Doppler is much less angle dependent.
In power Doppler mode, the hue and brightness of the color signal represents the power in the Doppler signal, which is related to the number of red blood cells producing the Doppler shift. Power Doppler can visualize smaller vessels as well as slower flow vessels, achieving improved visualization of vascular borders and contours. The duplex imaging of both gray-scale and (color or power) Doppler allows one to distinguish between vascular and cystic structures.
Particularly, vascular involvement or extent of tumor thrombus within the vessels (especially renal hilum) can be delineated. Therefore, laparoscopic ultrasonography is capable of enhancing the accuracy of staging laparoscopy.
Real-time visualization of blood flow will also provide significant physiologic and pathophysiologic information including tumor vascularity, lymph node involvement along vessels, and tumor resectability.
Critical anatomic information provided by laparoscopic ultrasonography for technical success of laparoscopic adrenalectomy includes demonstration of fat plane between the adrenal gland and the aorta, inferior vena cava, kidney, renal pedicle, pancreas, liver, and diaphragm; ruling out local invasion into adjacent organs; locoregional lymph adenopathy; exclusion of adrenal vein thrombus; and dimension of adrenal gland, extracapsular extension, or lack thereof.
With the placement of the laparoscopic ultrasonography probe directly on the vena cava and renal vein, tumor-bearing and tumor-free areas in the proximal renal vein could be easily identified, despite the lack of tactile sensation.
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