Ultrasound images Renal artery stenosis

This generally occurs at the site of the anastomosis close to the iliac artery but can also occur along the length of the artery or even affect the intrarenal branches. The patient may present with severe, difficult-to-control hypertension, graft dysfunction, or both. Alternatively the patient’s renal function may deteriorate following angiotensin-converting enzyme inhibitor therapy and this is also an indication of a possible underlying RAS. Careful Doppler examination is now the accepted first-line investigation in the diagnosis of RAS.
In most cases it is possible to trace the artery back to its anastomosis with the iliac artery, using colour Doppler. If the site of the stenosis is identified, spectral Doppler will demonstrate an increase in peak systolic velocity at the lesion, followed by poststenotic turbulence (Fig. ultrasound images below). This can be difficult to pinpoint with MRA, especially if bowel is overlying the vessel. A delayed systolic rise (the parvus tardus waveform) can be identified in the intrarenal spectral Doppler waveforms, as for the native kidney (see above). The diagnosis however is primarily made on the peak systolic velocity within the renal artery. A value of < 2.5 m/s is normal while > 2.5 m/s constitutes RAS. If the stenosis is severe, it may be difficult to identify colour flow in the kidney and the waveform may be reduced in velocity with a tiny, damped trace in the main vessel. A stenosis affecting an interlobar artery may result in focal, segmental changes in the kidney. In general, contrast angiography is only used to grade and treat stenoses after a positive ultrasound scan, or when a high index of clinical suspicion persists, despite a negative ultrasound.
Ultrasound images of demonstrating turbulence distal to the site of stenosis
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