Teaching Case

The authors present a case of a 62-year-old man submitted to kidney transplantation due to IgA nephropathy, who developed increasing PCr serum levels, arterial hypertension and proteinuria three months after transplant. Maintenance immunosuppression is performed with tacrolimus, mycophenolatemofetil and corticosteroids.

Doppler ultrasound demonstrated normal graft size and parenchyma corticomedullary differentiation (Fig. 1) with transplant renal artery implanted on the right external iliac artery. Spectral and colour Doppler (Fig. 2, 3) showed interlobar renal arteries tardus and parvus waveform and an increase velocity peak (>200cm/sec) at the anastomosis indicative of transplant renal artery stenosis (TRAS).
Under local anaesthesia a percutaneous retrograde ipsilateral femoral access to the graft was performed using a 5F 11cm-long sheath. A preliminary nonselective angiography (Fig. 4) confirmed the diagnosis and ruled out iliac obstructive disease.
With the confirmation of a 90% stenosis, catheterisation of the transplant artery was obtained using a 0.014” guidewire (Advantage, Terumo, Tokyo, Japan). Then a 5 mm x 20 mm balloon-expandable stent (Formula, Cook Medical, Bloomington, IN, USA) was deployed (Fig. 5). Control angiography (Fig. 6) revealed technical success.
Follow-up was performed with clinical surveillance and Doppler ultrasonography which demonstrated normal transplant blood flow haemodynamics (Fig. 7, 8).

A. Background
TRAS is a well-recognised vascular complication and a major cause of graft loss and premature death. [1]
Approximately half of stenoses occur at the anastomosis due to perfusion cannula injury, faulty surgical technique or reaction to suture material, with end-to-end anastomoses having a higher risk of stenosis. Stenosis can occur proximal to the anastomosis, often due to atherosclerotic disease, or distal, secondary to rejection, or turbulent flow.

B. Clinical Perspective

Clinical indicators of TRAS are graft dysfunction and/or new or refractory hypertension or azotaemia in the absence of rejection, urinary obstruction or infection.
TRAS usually occurs between 3 months and 2 years after renal transplantation, with the highest frequency in the first 6 months. [2] Patients with TRAS usually present with refractory hypertension, fluid retention and/or graft dysfunction. An audible bruit over the graft may be present. [3]
Reported significant risk factors for TRAS are delayed graft function and cytomegalovirus infection. [4, 5]

C. Imaging Perspective

Doppler ultrasonography is the modality of choice in the evaluation of the renal graft. In TRAS it shows a focal area of colour aliasing with peak systolic velocities >200 cm/sec, a velocity gradient between the stenotic/prestenotic segment >2:1, and post stenotic spectral broadening. A tardus-parvus waveform may be appreciated in the arcuate and interlobar arteries of the renal parenchyma. [6] Although Doppler is commonly used as a screening tool for TRAS, angiography provides the definitive diagnosis. [1]

D. Outcome

The presence of clinical symptoms is the main indication of treatment. An isolated Doppler ultrasonography examination showing proximal stenosis of the allograft artery does not always imply clinical consequence. Conservative treatment with antihypertensive medications can be used. [1]
The vast majority of TRAS are treated using an endovascular approach, either by balloon angioplasty or by primary or secondary stenting (technical success rates: 89% - 100%). The procedure is safe and restenosis is the main inherent complication (balloon angioplasty 10-56% vs primary stenting 5.5%-20%). [7]
Revision open surgery is considered as a rescue therapy and is reserved for cases of unsuccessful angioplasty due to high reported rate of significant complications. [8]

E. Take Home Message

Several of the major complications after renal transplantation can be detected with US Doppler imaging. TRAS is a recognised severe complication resulting in transplant insufficiency. Doppler ultrasonography demonstrates flow haemodynamics changes and definitive diagnosis is obtained by angiography. Percutaneous angioplasty and stenting are the first-line therapy to correct haemodynamically significant stenosis in TRAS, a safe and effective procedure.