Renal Transplant

The most common cause for deteriorating renal function in renal transplant patients is rejection. However, the possibility of transplant renal artery stenosis must also be considered, especially if there is associated new onset or severe hypertension. Early diagnosis of arterial stenosis is essential to salvage a failing renal allograft (Fig. 15a, b). Digital subtraction angiography is the gold standard for evaluation of these vascular complications, but the invasiveness and particularly the risk of potential nephrotoxicity to the already compromised kidney due to the iodinated contrast medium make DSA less suitable for renal transplant follow-up. MRA has been shown to be a reliable method of diagnosing transplant renal artery stenosis (Table 4).

The transplant renal artery examination is performed in a manner similar to native renal artery imaging but shifted lower into the pelvis to cover the transplant kidney and in-flow from the iliac arteries. Three-dimensional contrast MRA is performed in the coronal plane encompassing the lower abdominal aorta and extending down to below the femoral heads. The transplanted artery is usually anastomosedto the ipsilateral external iliac artery using an end-to-side anastomosis or to the

End End Anastomosis Renal Transplant
Fig. 15a, b. Stenosis of the iliac artery in a patient with ipsilateral transplant kidney

internal iliac artery using an end-to-end anastomosis. Generally, about 40 sections (interpolated to 80 sections with zero padding), each 2-3 mm or less, are sufficient to include the aorta, iliac arteries and the entire transplant kidney. The posterior coverage must be sufficient to include tortuous iliac arteries. Post contrast Tl-weighted images within 5-10 minutes of intravenous Gd injection should be acquired to assess renal excretory function and to demonstrate perfusion defects, masses, infarction, peri-transplant fluid collections, and hy-dronephrosis. T2-weighted imaging with fat saturation is also helpful. Vascular clips in the surgical bed may produce metallic artifact on MRA (Fig. 16). This potential pitfall can be avoided by recognizing its characteristic MR imaging appearance and correlating the imaging findings with CT or conventional radiography.

Nevertheless an origin of an accessory renal artery or a renal artery in congenital malformations (Fig. 17a, b) from the iliac arteries may as well be found, thus it is always important to include the iliac arteries in the field-of-view.

Artificial Artery
Fig. 16. Vascular clip artifact resulting in an image with an artificial occlusion of the right iliac artery. However due to the normal enhancement of the distal vessel it is obvious that the occlusion is artificial

Fig. 17a, b. Congenital pelvic kidney with a renal artery arising from the left common iliac artery (Gd-BOPTA, 0.1 mmol/kg). Whereas a first arterial acquisition (a) clearly displays the origin of the renal artery (arrow) the venous phase image (b) nicely displays two renal veins and their complex relationship to the iliac arteries and aortic bifurcation [Images courtesy of Dr. G. Schneider]

Pelvic Kidney

Fig. 17a, b. Congenital pelvic kidney with a renal artery arising from the left common iliac artery (Gd-BOPTA, 0.1 mmol/kg). Whereas a first arterial acquisition (a) clearly displays the origin of the renal artery (arrow) the venous phase image (b) nicely displays two renal veins and their complex relationship to the iliac arteries and aortic bifurcation [Images courtesy of Dr. G. Schneider]

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  • yasmin
    What is congenital pelvic kidney?
    8 years ago

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