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Doppler ultrasound in transplant renal artery stenosis
1. Doppler in transplant renal artery stenosis
Samir Haffar M.D.
Assistant professor - Department of internal medicine
2. Christian Doppler (1803 – 1853)
Famous for what is called now “Doppler effect”
1841: Professor of mathematics & physics
Prague polytechnic
1842: Published his famous book
“ On the colored light of the binary stars
& some other stars of the heavens ”
1850: Head of institute of experimental physics
Vienna University
3. First reported case
of transplant renal artery stenosis
Case records of the Massachusetts General Hospital
Case 43 – 1966. N Engl J Med 1966;275:721–729.
4. Transplant renal artery stenosis
• Potentially curable cause of refractory HTN
• 75% of all post-transplant vascular complications
• Incidence varies upon definition & diagnostic techniques
12% Routine Doppler in asymptomatic recipients
2% Doppler to confirm clinical suspicion
• Timing Can present at any time
Usually 3 mo – 2 yr after transplantation
Bruno S et al. J Am Soc Nephrol 2004 ; 15 : 134 – 141.
5. Clinical presentation of TRAS
• Severe HTN Difficult to treat
• Vascular murmur Not specific
• Graft dysfunction Specially after ACEi
• Erythrocytosis Found by some authors
• Asymptomatic Doppler done as routine screening
ACEI: Angiotensin-Converting Enzyme Inhibitors
Buturovic -Ponikvar J. Nephrol Dial Transplant 2003 ; 18 : v74 – v77.
6. Causes of post-transplant HTN
65 - 90% of patients
• Calcineurin inhibitors Cyclosporine - Tacrolimus
• Corticosteroids Largely depends on dosage
• Transplant RAS 2 – 10 %
• Post-biopsy AVF Rare cause
• Chronic graft rejection
• Native kidneys & pre-transplant HTN
Ponticelli C. Medical complications of kidney transplantation.
Informa Healthcare, London, UK, 2007.
7. Locations for graft artery stenosis
Three 3 main locations
• At the site of anastomosis
Probably a consequence of surgical technique
• Distal from the site of anastomosis
Cause is still ill-defined
• At the distal arterial branches
Multiple stenoses – Expression of chronic rejection
8. Diagnostic procedures of TRAS
Procedures Performance
Plasma renin activity Less informative than unilateral RAS of native kidneys
Serum potassium Normal or in patients on Cyc, tacrolimus or RI
Renal scintigraphy Good sensitivity 75% – Poor specificity 67%
CDUS Good sensitivity (87-94%) – Good specificity (86-100%)
Spiral or MSCT Contrast medium – High cost – Limited accessibility
MRI Gadolinium – High cost – More limited accessibility
Arteriography Gold standard test – Invasive – Contrast medium
Bruno S et al. J Am Soc Nephrol 2004 ;15 : 134 – 141.
9. Sonography of renal allograft
Routine exams
• 1 – 2 days after transplantation
Important standard to be compared with later changes
• 1 – 2 weeks after transplantation
• 3 months after transplantation
10. CDUS in transplant RAS
Best screening tool
• Main advantages Non-invasive
High sensitivity & specificity
Performed at bedside (ICU)
Follow-up
• Main disadvantages Operator dependency
Time-consuming
Operator should consult the surgery report
Multiple arteries – Anastomotic problems
11. End-to-end arterial anastomosis
Artery
End-to-end anastomosis
to internal iliac artery
Vein
End-to-side anastomosis
to external iliac vein
Classical kidney transplantation surgery
Possibility of erectile dysfunction & TRAS
12. End-to-side arterial anastomosis
Artery
End-to-side anastomosis
to external iliac artery
Vein
End-to-side anastomosis
to external iliac vein
Possibilty of early obstruction, late stenosis
& steal phenomenon
14. CDUS – 1st approach
Extrarenal Doppler
• Scanning of RA from anastomosis to hilus
Pic Systolic Velocity around anastomosis
• Diagnosis severity of stenosis
• Diagnosis non-significant relative stenosis
• Possibility of localization
• High operator dependency
16. CDUS – 2nd approach
Intrarenal Doppler
• Interlobar arteries (upper, middle, & lower poles)
Resistance index & Acceleration Time
• Can be amplified by use of captopril
• Not so operator dependent
• Only diagnose high grade stenosis (> 80 %)
• No possibility to localize stenosis along TRA
17. Resistance index or Pourcelot index
RI: S – ED / S
Normal: 50 – 70%
Abnormal: > 80 %
19. RI & renal allograft survival
601 patients – Follow-up 3 years
Radermacher J et al. N Engl J Med 2003 ; 349 : 115 – 24.
RI > 0.8 measured 3 months posttransplantation
has poor subsequent graft function & death
20. Accleration time
AT
• Length of time in seconds from
onset of systole to peak systole
• Normal value: < 0.07 second
23. Doppler of transplant RAS
Clerbaux G et al. Nephrol Dial Transplant 2003 ; 18 : 1401 – 1404.
Extra-renal Doppler
• PSV > 2 m/sec *
• Velocity gradient > 2
• Distal spectral broadening
* Generally accepted criteria
Values differs from 1.5–3m/sec
Intra-renal Doppler
• RI < 0.50
• AT > 0.07 sec
• AI < 3m/sec2
Only in severe stenosis
(> 80 % diameter reduction)
24. Severe transplant renal artery stenosis
End-to-end-anastomosis
Stenotic anastomosis
PSV: 6.54 m/s
Proximal IIA
PSV: 0.78 m/s
Velocity ratio: 8
25. Severe transplant renal artery stenosis
End-to-side-anastomosis
PSV: 3.74 m/s
Stenotic anastomosis
PSV: Proximal 1.29 m/s
Anastomosis 1.77 m/s
Distal 1.35 m/s
EIA
Velocity ratio: 2.3
26. PSV threshold for action
• 2.5 m/sec used by many centers
• One report use the value of 3 m/sec*
• Diagnosis of sub-clinical arterial stenosis may be
of no significance
• No evidence these lesions progress to clinical significance
* Patel U. Clinical Radiology 2003 ; 58 : 772 – 777.
27. Spectral broadening
Post-stenotic zone
• Proportional to severity of stenosis
• Cannot be precisely quantified: evaluated visually
• Fill-in of spectral window > 50% reduction
• Severely disturbed flow > 70% reduction
High amplitude
Low frequency Doppler signal
Flow reversal
Poor definition of spectral border
31. Doppler of transplant RAS
Extrarenal Doppler Intrarenal Doppler
PSV > 2.5 m/sec * RI < 0.50
Velocity gradient > 2 AT > 0.07 sec
Marked distal spectral broadening AI < 3m/sec2
* Generally accepted criterion for diagnosis
Cut-off value differs from series to series (1.5 – 3.0 m/sec)
Nephrol Dial Transplant 2003 ; 18 : 1401 – 1404.
32. Doppler parameters between EE & ES TRAS
Retrospective – 38 patients – severe TRAS
End-to-End
(n = 19)
End-to-Side
(n = 19)
P value
PSV at stenosis
PSV proximal to stenosis
PSV ratio
4.62 ± 0.64
0.66 ± 0.19
7.61 ± 2.52
3.65 ± 1.33
1.18 ± 0.41
3.25 ± 1.37
< 0.01
< 0.001
< 0.001
AT in intrarenal artery 0.11 ± 0.04 0.12 ± 0.05 > 0.05
Gaoa J et al. Clinical Imaging 2009 ; 33 :116 – 122.
Different criteria need to be established depending
on type of arterial anastomosis in severe TRAS
33. Special forms of TRAS
• Intimal dissection of TRA
• Kinking of TRA
• Pseudo-TRAS
34. Intimal dissection of TRA
Rarely documented in literature
• Timing Within a week after transplantation
• Causes Artery traction: harvesting, cannulation, clamp
• Symptom Sudden onset of oligoanuria
• CDUS Severe perfusion failure - Flap not visualized
• Dx Angiography
• DD Acute rejection: rare in first few days
ATN - Cyclosporine toxicity - RV thrombosis
• Prognosis If not diagnosed: RA thrombosis - Graft loss
Takahashi M et al. AJR 2003;180:759 – 763.
35. Intimal dissection of TRA
Takahashi M et al. AJR 2003;180:759 – 763.
Severe TRA stricture
Occlusion of IIA
Atherosclerosis of CIA
Angioplasty
1st stent placement
Remaining intimal flap
2nd stent placement
No residual stenosis
36. Kinking of transplant renal artery
Artery longer than vein
• Simulates hemodynamic & functional changes of TRAS
• Occasionally occurs when right kidney transplanted
RRA longer than RRV
Kinking of artery when anastomosis completed
Subsequent surgical revision if not recognized at surgery
Gray DW. Transplant Rev1994 ; 8 : 15 – 21.
37. Kinking of renal artery
False-positive result of CDUS
Patel U et al. Clin Radiol 2003 ; 58 : 772 – 777.
Kink at anastomosis between
TRA & IIAPSV 286 cm/s
38. Pseudo-TRAS
Should always be taken into consideration
• Iliac artery disease proximal to the anastomosis
Elderly patients or diabetic patients
• Low flow to transplanted kidney
• Signs & symptoms resembling those of TRAS
• Claudication or other signs of limbs hypoperfusion
• Treated by angioplasty or surgical revascularization
Aslam S et al. Transplantation 2001 ; 71 : 814 – 817.
39. Conclusion
CDUS & TRAS
• CDUS is best screening tool for diagnosis of TRAS
• Need more precision in PSV for diagnosis of TRAS
• Need different criteria for diagnosis in EE or ES
• CDUS cannot diagnose intimal dissection
• CDUS cannot diagnose kinking
• Angiography remains the gold standard (MSCT?)
Some patients may even have paradoxically normal or low BP, rapid deterioration of renal function, or even acute renal failure because of overzealous diuretic therapy or addition of either an angiotensin-converting enzyme inhibitor (ACEi) or an angiotensin II receptor blocker (ATA II) to the antihypertensive treatment.Reference:Curtis JJ, Luke RG, Whelchel JD, Diethelm AG, Jones P, Dustan HP: Inhibition of angiotensin-converting enzyme in renal-transplantrecipients with hypertension. N Engl J Med 308: 377–381,1983.Bruit: The presence of a bruit is not specific because it may be caused by physiologic vascular turbulence in the iliac or femoral arteries possibly sustained by increased blood perfusion close to the anastomosis. Bruits from proximal iliac vessel stenoses or biopsy-induced parenchymalarteriovenous fistulas can also confound the clinical picture. However, significant stenosis can occur in the absence of an audible bruit.
Potential mechanisms responsible for renal vasoconstriction caused by cyclosporineIncreased production of endothelin-1Activation of renin–angiotensin systemReduced production of nitric oxideIncreased production of TGFβ1Prostaglandin imbalanceIncreased sympathetic activity
Angiography: Need for relatively large amounts of radio-contrast medium that may precipitate acute renal failure particularly in patients with renal dysfunction. Thromboembolismis an even more severe complication that can cause irreversible graft function loss, and is reported in up to 9% of cases. Groin hematomas, pseudoaneurysms, and traumatic arteriovenous fistulas are other possible complications that, all together, occur in less than 10% of cases. Because of the substantial risks and the relatively high costs, renal angiography cannot be considered a screening procedure, but it iselectively indicated when a stenosis is suspected on the basis of non-invasive tests. An additional, practical feature of the procedureis that, as soon as the diagnosis is established, the stenosis can be immediately corrected by transluminal angioplastyfollowed by the deployment of a stent. The effectiveness of the intervention can then be immediately verified by asecond angiographic evaluation.
Classical kidney transplantation surgery was described using end-to-end anastomosis to the internal iliac artery & end-to-side anastomosis to the external iliac vein. This technique is performed in many transplant centers until today.However, some authors described the possibility of the occurrence of ED and renal artery stenosis with this type of anastomosis.
