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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE Table of Contents   
Year : 2001  |  Volume : 12  |  Issue : 2  |  Page : 157-163
Value of Doppler Ultrasound Hemodynamics in the Assessment of Renal Artery Stenosis in Transplanted Kidneys: An Assessment of Patients after Percutaneous Transluminal Angioplasty


1 Nephrology and Hypertension Division, Department of Medicine, King Fahad National Guard Hospital, Riyadh, Saudi Arabia
2 Department of Medical Imaging, King Fahad National Guard Hospital, Riyadh, Saudi Arabia

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   Abstract 

Doppler ultrasound (USS) may allow a non-invasive early diagnosis of transplant renal artery stenosis (TRAS). Adequate Doppler sampling of the transplant renal artery is difficult, time consuming and highly operator dependent. As a result, there has been increased attention focused on the intrarenal vessels and downstream changes that occur secondary to TRAS. We evaluated Doppler USS parameters in nine patients with TRAS confirmed on angiography (significant stenosis defined as > 60% diameter narrowing). Doppler USS correctly identified all the nine stenoses. Mean peak systolic velocity (PSV) was 3.6 m/s + 1.09. Mean end-diastolic velocity (EDV) was 1.75 m/s + 0.25 with an acceleration time (AT) of 0.14 + 0.04 sec and resistivity index (RI) of 0.42 + 0.12. Early systolic peak (ESP) was lost in all cases. Percutaneous transluminal angioplasty (PTA) was successfully done in five patients with significant improvement in Doppler parameters. PSV decreased from 4.04 m/s + 1.35 to 0.76 m/s + 0.42 (p = 0.01). Similarly EDV improved from 1.71 m/s + 0.28 to 0.30 m/s + 0.17 (p = 0.001). AT improved from 0.13 + 0.01 to 0.05 + 0.01 sec (p = 0.001). RI normalized from 0.34 + 0.07 to 0.73 + 0.09 (p = 0.008). ESP was restored in all the patients. In conclusion: our results show that the Doppler USS analysis of segmental arteries is an excellent tool for the diagnosis of TRAS and follow-up of patients post PTA.

How to cite this article:
Huraib S, Tanimu D, Gorka W. Value of Doppler Ultrasound Hemodynamics in the Assessment of Renal Artery Stenosis in Transplanted Kidneys: An Assessment of Patients after Percutaneous Transluminal Angioplasty. Saudi J Kidney Dis Transpl 2001;12:157-63

How to cite this URL:
Huraib S, Tanimu D, Gorka W. Value of Doppler Ultrasound Hemodynamics in the Assessment of Renal Artery Stenosis in Transplanted Kidneys: An Assessment of Patients after Percutaneous Transluminal Angioplasty. Saudi J Kidney Dis Transpl [serial online] 2001 [cited 2019 Nov 15];12:157-63. Available from: http://www.sjkdt.org/text.asp?2001/12/2/157/33805

   Introduction Top


Hypertension is a common complication after renal transplantation, with a reported prevalence of 20-80%. [1],[2] Risk factors for hypertension following renal transplantation include transplant renal artery stenosis (TRAS), native kidneys, recurrent disease, rejection and the use of cyclosporin. [1],[2],[3]

The incidence of TRAS as a cause of hypertension ranges from 1.5% to 16%. [4],[5] TRAS may lead to a significant impairment of allograft function [4] and early diagnosis may allow correction with percutaneous transluminal angioplasty (PTA). [6]

Angiography remains the gold standard for evaluation of possible stenosis. However, concerns about the nephrotoxicity of intra­venous contrast agents and the invasiveness of the procedure make it a less than optimum screening procedure for stenosis. In addition, the relatively low prevalence of TRAS does not justify the use of angio­graphy in all patients with hypertension.

Doppler ultrasound clearly has proved to be an excellent non-invasive screening modality for the identification of possible TRAS. [7],[8],[9] Doppler ultrasound is useful in assessing the effectiveness of revasculari­zation procedures such as angioplasty. [10] After successful angioplasty, intrarenal waveform parameters return to normal immediately. Their failure to do so indicates a poor technical result and predicts a poor blood pressure response to treatment.

The aim of the present study was to evaluate the utility of extrarenal and intra­renal Doppler waveform parameters for identifying patients with TRAS of > 60% and to examine the role of Doppler ultrasound in the follow-up of patients after angioplasty.


   Materials and Methods Top


Nine patients with suspected TRAS were referred for Doppler ultrasound. Referral criteria included: hypertension in six patients, the presence of graft bruit on auscultation in three, and unexplained deterioration in renal function in three.

There were five males and four females with a mean age of 33.1 years + 11.8 (range 16-51 years). The mean time between renal transplantation and Doppler ultrasound was 16 months (range 4-26 months). Arterial anastomosis was end to side to the external iliac artery in all patients. Their mean serum creatinine was 157 + 54 µmol/L (range 78­-246 µmol/L). [Table - 1] shoes that the median number of anti-hypertensive medications was two (range 1-3). Doppler ultrasound was performed after an overnight fast using a 3.5 mHz transducer with a commercially available equipment (Acuson 128, Mountain View, CA, USA). Doppler ultrasound of the intrarenal vessels was conducted and arterial Doppler spectra were sampled from the upper, mid- and lower-pole (examples in [Figure - 1],[Figure - 2],[Figure - 3]). The following Doppler indices were recorded: acceleration time (AT), resistivity index (RI) and the presence of early systolic peak (ESP). The main transplant renal artery was then examined from the anastomosis to the hilum in the supine position with measurement of peak systolic velocity (PSV) and end-diastolic velocity (EDV).

The criteria for the diagnosis of TRAS included: AT > 0.15 sec, RI < 0.50, loss of ESP for intrarenal parameters and PSV > 1.8 m/s for extrarenal parameters.

All the nine patients were investigated by angiography using percutaneous femoral puncture performed under local anesthesia. The degree of stenosis was estimated by visual examination. TRAS > 60% was considered hemodynamically significant. However, only five patients had successful percutaneous transluminal angioplasty (PTA) at the time of angiography. In the remaining four patients, angioplasty was technically difficult: two patients developed thrombosis, one patient had dissection of artery and another patient had unsuccessful cannulation. Doppler ultrasound parameters were again repeated post angioplasty. Doppler analysis was compared to the angiographic findings.


   Results Top


Angiography confirmed the presence of a significant stenosis (> 60% diameter narrowing) in all the nine patients. All the patients had stenosis > 75% on angio­graphy. Doppler ultrasound correctly identified all the nine stenoses giving an overall sensitivity and specificity of 100%. All the patients had a mean PSV of 3.6 m/s + 1.09 (range 2.25 - 5.86 m/s). Mean EDV was 1.75 + 0.25 m/s with an AT of 0.14 + 0.04 sec and RI of 0.42 + 0.12, [Table - 2]. ESP was lost in all the cases.

PTA was successfully performed in five patients with a residual stenosis of < 50%. Doppler ultrasound was carried out in all the five patients post-angioplasty. In all patients there was a significant improve­ment in Doppler parameters, [Table - 3]. PSV decreased from 4.04 + 1.35 m/s to 0.76 + 0.42 m/s (p = 0.01). Similarly EDV improved from 1.71 + 0.28 m/s to 0.30 + 0.17 m/s (p = 0.001). AT improved from 0.13 + 0.01 sec to 0.05 + 0.01 sec (p = 0.001). RI normalized from 0.34 + 0.07 to 0.73 + 0.09 (p = 0.008). ESP was restored in all the patients. In the four patients with failed angioplasty, AT remained above 0.15 sec with RI below 0.5 and ESP remained absent.


   Discussion Top


Hypertension is the hallmark of a significant TRAS. However, up to 80% of patients with renal transplants may exhibit hypertension. [7] Diagnosis of TRAS should, therefore, only be suspected in patients with hypertension and graft dysfunction in the absence of rejection, refractory hypertension or newly developed and progressive hypertension. [11]

Although the gold standard of diagnosing renal artery stenosis is renal arteriography, a variety of less invasive tests have been evaluated for screening purposes, which include Duplex Doppler ultrasonography, captopril renogram, intravascular ultra­sonography, magnetic resonance angio­graphy and spiral CT with angiogaphy. [12],[13]

The mean time between transplantation and diagnosis of TRAS has been reported to be 23 months. [14] Most of our cases of TRAS were detected earlier, which may be a result of regular Doppler ultrasound screening.

Doppler ultrasound is a non-invasive imaging technique and is considered to be the first line screening test. Studies show a sensitivity of 60-100% and a specificity of 70-100%. [15],[16],[17] Differences in these reports may reflect variations in the frequency of accessory renal arteries, [18] type of transducer used, or criteria used in diagnosing TRAS. [19]

The values of peak systolic velocity used to defined TRAS ranged from 1.5 m/s to 2.5 m/s. [8],[9],[20] Adequate Doppler assessment of the transplant renal artery is difficult and time consuming. In several studies, 10-42% of the extrarenal arteries are not adequately visualized. [18],[21] Moreover, this technique is highly operator dependent. As a result, attention has focused on the intrarenal vessels and the downstream Doppler changes that occur secondary to TRAS.

The intrarenal Doppler waveform analysis is technically successful in the vast majority of patients because the translumbar approach avoids all the bowel gas, while providing excellent angles of insonation. In addition, it can be performed in one fourth of the examination time. Using the criteria of > 60% stenosis on angiogram for a hemodynamically significant stenosis, we have found correlation with Doppler ultrasound parameters. In our study, the mean PSV was 3.6 m/s with a range between 2.25 m/s and 5.86 m/s. Several Investigators [15],[17],[22] have demonstrated that using PSV values of 1.8-2.0 m/s as a criteria for the presence of a significant renal artery stenosis, sensitivities of 88-98% and specificities of 62-98% have been achieved. Our mean value for the EDV was 1.75 m/s and Olin and colleagues [15] demonstrated that 81% of renal artery had severe stenosis (> 80%) when measured EDV exceeded 1.5 m/s. Saarinen et al [10] have shown that a low RI (< 0.6) is highly suggestive of TRAS. Our mean value for the RI was 0.42 m/s. Using a threshold AT of 0.1 sec or . subjective assessment of dampening of the waveforms resulted in an accuracy of 95% in detecting a significant TRAS. [23] All our patients demonstrated loss of ESP with a mean AT of 0.14 m/s.

After successful angioplasty in five of our patients, Doppler analysis showed complete restoration of all Doppler parameters in four patients. Thus, Doppler assessment of the segmental artery may serve as a hemo­dynamic indicator of the results of PTA.

We conclude that our results show that Doppler ultrasound analysis of the segmental artery may be a useful tool for the diagnosis of TRAS and follow-up of patients post revascularization procedures.

 
   References Top

1.Curtis JJ. Hypertension and kidney trans-plantation. Am J Kidney Dis 1986;7:181-96.  Back to cited text no. 1  [PUBMED]  
2.Huysmans FT, Hoitsma AJ, Koene RA. Factors determining the prevalence of hypertension after renal transplantation. Nephrol Dial Transplant 1987;2:34-8.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Waltzer WC, Turner S, Frohnert P, Rapaport FT. Etiology and pathogenesis of hypertension following renal transplantation. Nephron 1986;42:102-9.  Back to cited text no. 3  [PUBMED]  
4.Roberts JP, Ascher NL, Fryd DS, et al. Transplant renal artery stenosis. Trans­plantation 1989;48:580-3.  Back to cited text no. 4    
5.Schacht RA, Martin DG, Karalakulasingam R, Wheeler CS, Lansing AM. Renal artery stenosis after renal transplantation. Am J Surg 1976;131:653-7.  Back to cited text no. 5  [PUBMED]  
6.Greenstein SM, Verstandig A, Mclean GK, et al. Percutaneous transluminal angioplasty. The procedure of choice in the hyper-tensive renal allograft recipient with renal artery stenosis. Transplantation 1987;43: 29-32.  Back to cited text no. 6    
7.Dodd GD 3d, Tublin ME, Shah A, Zajko AB. Imaging of vascular complications associated with renal transplants. Am J Roentgenol 1991;157:449-59.  Back to cited text no. 7    
8.Grenier N, Douws C, Morel D, et al. Detection of vascular complications in renal allografts with color Doppler flow imaging. Radiology 1991;178:217-23.  Back to cited text no. 8  [PUBMED]  
9.Snider JF, Hunter DW, Moradian GP, et al. Transplant renal artery stenosis: evaluation with duplex sonography. Radiology 1989; 172:1027-30.  Back to cited text no. 9  [PUBMED]  
10.Saarinen O, Salmela K, Edgren J. Doppler ultrasound in the diagnosis of renal transplant artery stenosis-value of resistive index. Acta Radiol 1994;35:586-­9.  Back to cited text no. 10  [PUBMED]  
11.Hohnke C, Abendroth D, Schleibner S, Land W. Vascular complications in 1,200 kidney transplantation. Transplant Proc 1987;19:3691-2.  Back to cited text no. 11    
12.Canzanello VJ, Textor SC. Non­invasive diagnosis of renovascular disease. Mayo Clin Proc 1994;69:1172-81.  Back to cited text no. 12  [PUBMED]  
13.Derkx FH, Schalekamp MA. Renal artery stenosis and hypertension. Lancet 1994; 344:237-9.  Back to cited text no. 13  [PUBMED]  
14.Gedroyc WM, Reidy JF, Saxton HM. Arteriography of renal transplantation. Clin Radiol 1987;38:239-43.  Back to cited text no. 14  [PUBMED]  
15.Olin JW, Piedmonte MR, Young JR, DeAnna S, Grubb M, Childs MB. The utility of duplex ultrasound scanning of the renal arteries for diagnosing significant renal artery stenosis. Ann Intern Med 1995;122:833-8.  Back to cited text no. 15  [PUBMED]  [FULLTEXT]
16.Miralles M, Santiso A, Gimenez A, et al. Renal duplex scanning: correlation with angiography and isotopic renography. Eur J Vasc Surg 1993;7:188-94.  Back to cited text no. 16  [PUBMED]  
17.Strandness DE. Duplex imaging for the detection of renal artery stenosis. Am J Kidney Dis 1994;24:674-8.  Back to cited text no. 17    
18.Berland LL, Koslin DB, Routh WD, Keller FS. Renal artery stenosis: pros­pective evaluation of diagnosis with color duplex US compared with angiography. Radiology 1990;174:421-23.  Back to cited text no. 18  [PUBMED]  
19.Krumme B, Rump LC. Color Doppler sonography to screen for renal artery stenosis - technical points to consider. Nephrol Dial Transplant 1996;2385-9.  Back to cited text no. 19    
20.Baxter GM, Ireland H, Moss JG, et al. Color Doppler ultrasound in renal transplant artery stenosis: which Doppler index? Clin Radiol 1995;50:618-22.  Back to cited text no. 20  [PUBMED]  
21.Hoffmann U, Edwards JM, Carter S, et al. Role of duplex scanning for the detection of atherosclerotic renal artery disease. Kidney Int 1991;39:1232-9.  Back to cited text no. 21  [PUBMED]  
22.Hansen KJ, Tribble RW, Reavis SW, et al. Renal duplex sonography: evaluation of clinical utility. J Vasc Surg 1990;12:227­-36.  Back to cited text no. 22    
23.Gottlieb RH, Lieberman JL, Pabico RC, Waldman DL. Diagnosis of renal artery stenosis in transplanted kidneys: value of Doppler waveform analysis of the intra-renal arteries. Am J Roentgenol 1995;165: 1441-6.  Back to cited text no. 23    

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Correspondence Address:
Sameer Huraib
Division of Nephrology and Hypertension, Department of Medicine, King Fahad National Guard Hospital, P.O. Box 22490, Riyadh 11426
Saudi Arabia
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PMID: 18209367

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