Transplant renal artery stenosis
Rule out hydronephrosis after double-J removal and follow-up peri-graft fluid collections
Selected ultrasound images
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Selected images (labeled in French) of a 1 month post-operative follow-up renal transplant Doppler study.
The transplant shows normal echogenicity with good corticomedullary differentiation. No hydronephrosis.
Slight enlargement compared to previous studies of two perinephric fluid collections.
The kidney graft shows homogeneous vascularity on power Doppler. Renal arterial resistive index are slightly elevated since last exam, varying between 0.62 and 0,76 (previously maximally 0,70; not shown). The intra-renal arterial curves also have a slightly delayed systolic upstroke.
The renal vein is permeable, with proper respiratory variability.
The renal transplant artery anastomosis shows aliasing on color Doppler, despite proper imaging parameters with scale set to maximum. Spectral Doppler shows spectral broadening (increased spectral ranges under the curve) and velocity acceleration up to 623 cm/s. The adjacent external iliac artery has a normal spectral curve and maximum velocity of 105 cm/s. There is therefore nearly a 6:1 ratio between the transplant artery and external iliac. These findings are diagnostic for transplant renal artery stenosis.
Transplant renal artery stenosis is a serious complication threatening the long-term viability of kidney grafts. In the immediate post-operative period, it is considered a normal finding because of peri-anastomotic edema. However, after one month post-operative, its persistence is clearly an abnormal finding. Causes include intimal scarring or hyperplasia, kinking and extrinsic compression.
This case highlights the importance of carefully assessing the arterial anastomosis on all transplant ultrasounds with proper Doppler settings. Color Doppler scale should be set to the highest range allowable on the machine and zones of aliasing should be sought. The spectral Doppler interrogation box should be placed centrally in the area of maximal aliasing on color Doppler.
Care should be taken to avoid false negative results. In highly turbulent flow in and after a tight stenosis, there can be more than one apparent spectral curve. If the scale of the spectral Doppler is not specifically set to its optimal high value, the peak velocity can wrap around the baseline and become masked as spectral noise.