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Renal transplant. Rising creatinine.

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

History:  Renal transplant. Rising creatinine.


Transplant kidney is shown below. Which choice is most appropriate?

Hydronephrosis.Stigmata of PTLD.Pathologically echogenic cortex.Medullary nephrocalcinosis.Within normal limits.Image
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Renal transplant. Rising creatinine.

Here now are some doppler images. Click to enlarge.

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Which choice most likely characterizes the diagnosis?

Acute rejection.Chronic rejection.Renal vein thrombosis.Renal transplant artery stenosis.Iliac arterial stenosis.
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Renal transplant. Rising creatinine.

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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).

Differential diagnosis:

  • 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)
Diagnosis:  Renal transplant arterial stenosis (mild)
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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.
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Renal transplant. Rising creatinine.


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