Genitourinary Radiology > Kidneys > Parenchymal > Small Kidney > Renal Artery Stenosis

Renal Artery Stenosis

Renal artery stenosis is the most common cause of a unilateral small, smooth kidney (other causes include chronic renal vein thrombosis, post-obstructive atrophy, renal hypoplasia, previous renal trauma or renal radiation therapy).

IV contrast study shows a small smooth kidney with delayed nephrogram, delayed pyelogram, and late development of hyperdense pyelogram. Calyces and ureter are normal. A delayed pyelogram is a result of slow blood flow through the affected kidney. Decreased pressure within the nephron and increased amount of time within the tubules allows more water to be reabsorbed, causing concentration of contrast material and a hyperdense pyelogram. Enlarged collateral ureteric arteries may cause notching of the ureter and renal pelvis.

Screening for renal artery stenosis can be performed with nuclear medicine study (with ACE inhibitor) or with renal ultrasound and with renal Doppler. In patients with uncontrolled hypertension despite multiple blood pressure medications, ultrasound may identify patients with RAS who should go onto renal angiography and angioplasty for cure of their hypertension. With renal artery Doppler, a marked increase in flow at the level of stenosis is detected or downstream from the stenosis, a parvus tardus waveform can be detected.

Renal artery Doppler ultrasound (1) screening for renal artery stenosis shows very high velocity flow at the level of the left renal artery origin from the aorta.  This indicated a significant stenosis.  (2) Subsequent arteriogram in same patient shows tight stenosis at the left renal artery ostium.  Following angioplasty, the stenosis was gone and the patient's hypertension resolved.

Screening color Doppler ultrasound with spectral analysis in patient with uncontrolled hypertension despite multiple blood pressure meds shows classic parvus tardus (slow peak and dimished amplitude to systolic peak) of renal artery waveform distal to a renal artery stenosis. See arrows.

Angiographic study with injection of aorta at the level of the renal arteries in same patient as above shows tight stenosis just distal to take off of left renal artery (arrow).

Following angioplasty and stenting, flow to the left kidney is improved and the vessel lumen is normal caliber. The patient's hypertension resolved.

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