Renal transplant. Rising creatinine.

Our appreciation is extended to Dr.  Lauren Ladd, Indiana University Department of Radiology, for contributing this case.

Renal transplant. Rising creatinine.

Renal transplant. Rising creatinine.

Findings:

Normal renal transplant appearance without hydronephrosis or abnormal perinephric fluid collection.

Renal Doppler:  Normal resistive indices in the arcuate arteries, normal iliac artery flow.

Main renal artery velocities as follows:  at the anastomosis (2.3 m/s, RI 0.92), mid artery (0.9 m/s, RI 0.82), and at the hilum (0.7 m/s, RI 0.8).  Elevated renal artery flow velocity at the anastomosis is accompanied by decreased amplitude and upstroke velocity of the downstream renal artery (parvus tardus waveform).

• Medication related (cyclosporine or Tacrolimus- related preglomerular vasoconstriction)
• Native iliac artery stenosis
• Renal transplant artery stenosis
• Acute vascular rejection
• Chronic graft rejection
• Segmental infarction (with or without thrombosed polar renal artery)

Renal transplant. Rising creatinine.

Key points: 

• Transplant renal artery stenosis usually occurs between 3-24 months after transplant.
• Many possible causes, differentiated by location of stenosis and temporal presentation:
  • Pre-anastomotic: atherosclerotic disease (if early, likely within donor vessel; if late, possibly developed within graft).
  • Anastomotic (50%, greater occurrence if end-to-end anastomosis): trauma to vessel (during harvest / implantation), reaction to suture material, acute vascular rejection.
  • Post-anastomotic: rejection (more commonly chronic, can be acute), malpositioned kidney with twisted / kinked artery.
• Imaging:
  • Ultrasound with spectral Doppler = first line imaging
    • Color aliasing, spectral broadening, turbulent flow just distal to stenosis
    • Increased resistive index at the site of stenosis (>0.56)
    • Flow velocity gradient of stenotic to post- stenotic segments > 2:1
    • Parvus tardus waveform of downstream artery / intrarenal arteries
      • Parvus tardus: delayed time to peak (rounded instead of sharp upstroke) and decreased overall amplitude of the peak
  • MR angiography
    • Evaluates stenosis, can be performed without gadolinium contrast using time of flight technique
• Clinical presentation & treatment:
  • Presents with refractory hypertension (gradual or acutely progressive)
  • May also have graft dysfunction, or only graft dysfunction
  • Primary treatment is percutaneous transluminal angioplasty +/- stent placement
  • If early stenosis with suspicion for sutural cause or arterial damage, may perform surgical revision of anastomosis

References: 

1. Akbar SA, et al. Complications of Renal Transplantation. Radiographics. 2005; 25: 1335-1356.
2. Middleton, WD. Case Review Series: General and Vascular Ultrasound. St. Louis: Mosby, 2002.
3. Bruno S, Remuzzi G, and Ruggenenti P. Transplant Renal Artery Stenosis. Journal of the American Society of Nephrology. 2004; 15(1): 134-141.

Renal transplant. Rising creatinine.