One hundred ninety-five color Doppler flow (CDF) examinations were performed in 146 renal allografts to assess the capabilities of this technique in detecting intra- or extrarenal vascular complications. Conventional angiography was also performed in 44 transplants. In the group of transplants with angiographic correlation, CDF sonography enabled correct identification of 30 of 34 vascular complications. CDF showed 10 of 11 significant stenoses of the renal artery or of one of its main branches. There were two false-positive renal artery stenoses (one normal artery and one 40% stenosis). Nine of nine renal artery thromboses and the single pseudoaneurysm were also identified. Within the parenchyma, CDF sonography demonstrated five of five segmental infarcts, two of two postbiopsy arteriovenous fistulas, and three of six segmental or interlobar artery stenoses. Measurement of peak systolic velocity showed a significant difference (P less than .05) between a group (n = 8) with significant stenosis of the renal artery or one of its main branches (mean, 215.2 cm/sec +/- 32) and a group (n = 14) without stenosis (mean, 99.2 cm/sec +/- 19).

Dilatation of the collecting system is a classical phenomenon during pregnancy, due to hormonal and extrinsic compressive factors. Imaging has to differentiate a physiological dilatation and a pathological obstruction due to urolithiasis. Presently, sonography, using both, B-mode and color Doppler, has the potential to demonstrate the physiological compression of ureters at the level of the pelvic brim. A pathological obstruction is considered either when a stone is detected above the usual site of compression or when the ureter appears dilated beyond. Color Doppler helps in localizing the site of ureteral compression against the vessels and in differentiating ureters from veins. Magnetic resonance urography, with strongly T2-weighted sequences, also may show the site and type of obstruction without contrast agent administration. These two non-radiating techniques make it possible to avoid the use of X-rays in most cases for management of these patients. The type of treatment is based mostly on the level of pain and the presence or absence of stone.

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Twenty-two patients with hemodialysis grafts were prospectively evaluated with color Doppler flow imaging and digital subtraction angiography (DSA). Eighteen patients had normal functional parameters during hemodialysis, and four had increased venous pressure during hemodialysis. Color Doppler flow imaging allowed identification of nine macroaneurysms related to wall degeneration, two cases of spontaneous fistula formation between the graft and peripheral veins, and 20 stenoses. Use of color Doppler flow imaging led to overestimation of the degree of stenosis at the venous anastomosis when compared with use of angiography. Three cases of subclavian venous stenosis were identified only at angiography. Color Doppler flow imaging appears accurate in the detection of stenoses and seems sufficient for follow-up of normally functioning grafts. However, because of its low sensitivity for identification of proximal stenoses and the necessity of obtaining an angiogram to plan surgical or percutaneous correction, DSA remains the technique of choice.

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