Renal transplant rejection. Limited value of duplex Doppler sonography

Over a two-year period, 275 duplex Doppler ultrasound (US) examinations were performed on 75 renal allograft recipients. Retrospective visual analysis of the Doppler tracings was compared to concurrent clinical findings and to biopsy results. One hundred eight of the 176 Doppler examinations (61%) that showed acute rejection clinically or histologically were interpreted as rejection, while 80 of 99 examinations (81%) in clinically normal patients were interpreted as normal. Two hundred thirty-four examinations had resistive index (RI) calculations. Seventy-two of 141 examinations (51%) with RI less than 0.70 had clinical or biopsy evidence of rejection. Studies compared with only concurrent biopsies revealed that 35 of 39 US examinations interpreted as rejection were confirmed histologically, but only one of 32 examinations that appeared normal sonographically was histologically normal. The low sensitivity of Doppler US, whether by waveform analysis or RI calculation, makes it a poor screening test for acute rejection. The findings support the conclusion that Doppler sonography cannot replace biopsy in the evaluation of renal transplant dysfunction, particularly when the waveform analysis is normal and the RI less than 0.70.     

Pulsed duplex sonography in the detection of lower pole arteries in hydronephrosis

Pulsed duplex sonography was used for the diagnosis of lower pole arteries, which cross the uretero-pelvic junction and are possibly the reason of hydronephrosis. We could identify the crossing vessel in 8 patients by pulsed duplex sonography. The diagnosis is easy, though optimum patient preparation is required, and Duplexsonography may help to reduce the frequency of angiography in this special clinical situation.     

Renal carcinoma: duplex Doppler evaluation

Doppler ultrasound has a clearly defined role in the assessment of carotid and peripheral vascular disease. In these situations vessel pathology produces alterations in velocity and volume flow and in the flow-velocity spectrum. Flow in the renal arteries is affected not only by disease of the renal vessels but also by the peripheral resistance to flow within the kidney. Alterations in this peripheral resistance resulting from renal disease are reflected in the Doppler flow spectrum analysis. In 14 patients with renal carcinoma, three different blood flow patterns were observed, reflecting the differing vascularity of the renal tumours. These were compared with blood flow in normal kidneys and in kidneys containing renal cysts. Doppler ultrasound adds further information to the study of renal carcinomas, allowing the prediction of tumour vascularity, and may be useful as a preliminary investigation prior to angiography and embolisation.     

Renal allografts in acute rejection: evaluation using duplex sonography

Sixty-nine duplex sonographic studies were performed in 24 patients who had received renal allografts. After a prospective qualitative analysis of the Doppler waveforms, results were correlated with biopsy material and each patient's clinical course. Increased pulsatility of the Doppler waveform of intrarenal arterial flow constituted an abnormal study, indicating acute rejection. Overall sensitivity varied with the histologic form of rejection, with a 60% sensitivity for acute interstitial rejection with or without vascular rejection and an 82% sensitivity for acute vascular rejection. Overall specificity was 95% and 96%, respectively. Early rejection was also accurately detected in three patients less than 48 hours following kidney transplantation. Duplex sonography has a useful role in evaluating posttransplantation renal failure. Abnormal study results may obviate the need for biopsy and help in guiding clinical management.     

Renal vein Doppler sonography of obstructive uropathy

OBJECTIVE: Obstructive uropathy in the early stages can be difficult to diagnose using either standard sonography or the arterial resistive index. We tested the hypothesis that acute obstruction of the renal collecting system reduces the intraparenchymal renal compliance, which affects the intraparenchymal venous blood flow to a greater degree than the arterial flow. SUBJECTS AND METHODS: Twelve patients with clinical evidence of acute obstructive uropathy were referred for helical CT to confirm the diagnosis and to provide a gold standard by which we could evaluate the sonographic findings in the 12 test patients. Twelve patients without renal disease served as a control group. Doppler sonography of the interlobar arteries and veins of both kidneys then was performed, with the sonographer unaware of which kidney had an obstruction. Peak venous flow measurements and arterial resistive and venous impedance indexes were obtained. The impedance indexes of the obstructed and unobstructed kidney were compared for each patient. RESULTS: The mean arterial resistive indexes of the obstructed kidneys were larger than those of the unobstructed kidneys, 0.67 +/- 0.08 and 0.62 +/- 0.05, respectively (p = 0.05). The venous impedance indexes comparing obstructed and unobstructed sides were 0.38 +/- 0.25 and 0.80 +/- 0.25, respectively, a statistically significant result (p = 0.0002). On average, the peak venous flow signal in the obstructed kidney was 69% higher than that of the unobstructed kidney (p = 0.04) and 86% higher than that of the peak venous flow signal in the control group (p = 0.005). CONCLUSION: Renal obstruction alters the venous flow to a greater extent than the arterial flow, and a comparison between the venous flow in the obstructed and unobstructed kidneys may improve diagnostic accuracy.     

Renal artery stenosis: duplex Doppler evaluation

The renal arteries of 40 patients without renal or renovascular disease were examined with duplex real-time Doppler sonography. Special views were employed to obtain adequate images and Doppler recordings from the renal arteries. Time limits were placed on the duration of the examination, the better to reflect common clinical practice. Velocity spectral analysis of the Doppler shift frequency was achieved in 82.5% of the arteries examined and a characteristic "Doppler signature" for the renal artery identified. This was compared with the Doppler signal from the renal arteries of eight patients with renal artery stenosis. Significant differences in spectral pattern were demonstrated in renal artery stenosis. These differences are illustrated and their potential for screening for renovascular disease in systemic hypertension is discussed.     

Pulsed Doppler duplex sonography and CT of portal vein thrombosis

Five patients with partial or complete portal vein thrombosis were examined by both computed tomography (CT) and pulsed Doppler duplex scanning. Duplex scanning correctly identified portal vein thrombosis in all five. Duplex sonography may be the preferred technique to detect and follow portal vein thrombosis because of lower cost, lack of need for intravenous contrast material, and easier availability for multiple follow-up examinations.     

Distinction between obstructive and nonobstructive pyelocaliectasis with duplex Doppler sonography

Because animal studies have shown that renal obstruction increases renal vascular resistance, we theorized that obstruction would change the Doppler waveform. We studied the value of the resistive index (RI) calculated from the duplex Doppler waveform to distinguish between obstructive and nonobstructive pyelocaliectasis in 229 kidneys in 133 patients. The RI is the peak systolic frequency shift minus the minimum diastolic frequency shift, then divided by the peak systolic frequency shift. Duplex Doppler sonography was performed prospectively in 70 kidneys with pyelocaliectasis before the presence or absence of obstruction was established. In 54 of 70 kidneys, the presence or absence of obstruction was proved by interventional methods (percutaneous nephrostomy, antegrade or retrograde pyelography, loopography), and in the rest it was proved by body CT, excretory urography, or surgery. Thirty-eight kidneys were found to be obstructed, and 32 had nonobstructive dilatation. In addition, 159 kidneys without pyelocaliectasis were studied to identify possible limitations of Doppler sonography in the diagnosis of obstruction. Clinical history and laboratory data were used to determine that 109 of these kidneys were in normal subjects and 50 were in patients with nondilated renal disease. There was a significant difference between the mean RI of the obstructed (0.77 +/- 0.05) and the nonobstructed dilated (0.63 +/- 0.06) kidneys (p less than .01). Analysis of the receiver-operating-characteristic curve showed an RI of 0.70 to be a good discriminatory level for obstruction, resulting in a sensitivity of 92%, a specificity of 88%, and an accuracy of 90%. All 109 normal kidneys had an RI less than 0.70. Over half (27/50) of the kidneys in patients with nondilated renal disease had an elevated RI (greater than or equal to 0.70). Ninety-six patients had Doppler examinations on both kidneys, and in only six patients did the RI values of each kidney differ by more than 0.10; all six were proved to have unilateral obstruction. Use of duplex Doppler sonography should improve the specificity, and thus the accuracy, of sonography in the noninvasive diagnosis of obstruction and should be used when a dilated collecting system is identified.     

Renal allografts: prospective analysis of Doppler sonography

Fifty-six consecutively transplanted renal allografts were prospectively evaluated with serial Doppler sonographic examinations. Thirty-eight episodes of transplant rejection in 32 patients (63% proved pathologically) and 24 episodes of acute tubular necrosis (ATN) in 24 patients were encountered. The Doppler spectral waveform was characterized by means of the pulsatility index (PI), systolic/diastolic ratio (SDR), diastolic/systolic ratio (SDR), diastolic/systolic ratio (DSR), and resistive index (RI). Accuracy was optimized with use of top normal values as follows: PI = 1.8, SDR = 4.0, DSR = 0.25, RI = 0.75. There were no significant differences in the indices for those patients undergoing rejection versus those with ATN. The sensitivity for predicting transplant rejection was adversely affected by the history of either ATN or a previous rejection episode in the same allograft. Comparison with concurrent radionuclide examinations revealed similar sensitivities for rejection with scintigraphy and sonography. Differentiation of ATN from rejection was more reliable with scintigraphy than with sonography.     

Diagnosis of neonatal hemochromatosis with MR imaging and duplex Doppler sonography

Neonatal hemochromatosis is a rare congenital disorder which affects both fetuses and newborns. It is characterized by hepatocellular failure, often appearing on the first day of life in the form of coagulopathy, hypoalbuminemia, hypoglycemia, and jaundice. Most of the affected infants die early in life, and definitive diagnosis has often been made only by post-mortem evaluation. With the help of MRI, plus increasing awareness of the disorder, diagnosis is now often made early, even in utero. Duplex Doppler sonography does not provide information on siderosis but shows abnormalities in the liver or blood-flow patterns associated with liver disease. Received: 24 September 1998; Revised: 23 November 1998; Accepted: 27 January 1999     

Role of duplex Doppler and power Doppler sonography in transplanted kidneys with acute renal parenchymal dysfunction

The limited work published on the comparison of power Doppler sonography (PDS) and duplex Doppler sonography (DDS) in the assessment of acute renal allograft dysfunction has shown contradictory results. We compared the role of DDS and PDS in renal transplant recipients developing acute renal parenchymal dysfunction and correlated these findings with kidney biopsy, which was taken as the gold standard. Thirty post-renal transplant patients with acute graft dysfunction underwent Doppler sonography, DDS and PDS using an HDI 5000 ATL machine. Patients who developed graft dysfunction as a result of vascular, obstructive or other non-parenchymal causes were excluded. All patients underwent an allograft biopsy within 72 h of the sonography. Based on the biopsy findings, 24 patients were categorized as having acute rejection, and six patients as having no rejection. The overall sensitivity, specificity and accuracy of DDS for evaluation of graft dysfunction were 54.17, 33.33, and 50.00%, respectively, and that for PDS were superior with 87.50, 33.30, and 76.67%, respectively. The low specificity can be partially attributed to the small number of cases without rejection in our study population. We conclude that PDS is superior to DDS in screening patients with acute parenchymal renal dysfunction post-transplant. However, a normal PDS examination does not exclude the presence of acute rejection. Power Doppler sonography is a useful screening test for diagnosing acute rejection but a renal allograft biopsy remains the gold standard for diagnosis of this condition.     

Colour Doppler and duplex sonography and angiography of the carotid artery bifurcations

We undertook a prospective double-blind study of 128 carotid artery bifurcations using colour Doppler and duplex sonography and angiography. Sixty-four patients with cerebrovascular events were admitted for angiography. All underwent sonography within 24 h of angiography. Standard duplex sonography and colour Doppler imaging without spectral analysis were performed, on the same device, by two sonographers, using defined morphological and haemodynamic criteria. Digital radiological data on vessel diameter were interpreted independently by two radiologists.The two sonographic methods gave similar grading of stenosis, compared to angiography, with an accuracy ranging from 96% in severe to 83% in minor stenoses. Colour Doppler studies gave better area measurements than standard duplex sonography, except for major stenoses. Discrepancies between ultrasonography and angiography were due mainly, to minor stenoses and large plaques of calcification on the vessel walls, which masked very segmental 70% stenoses in 2 cases. Angiography is limited by its own resolution, does not show uncalcified vessel walls and does not give cross-sectional data. It would therefore be inappropriate for showing small plaques, the full extent of ectasia or for defining the carotid bulb accurately.The advantages of colour methods were in investigating sinuous or deep vessels and hypoechoic plaques. Analysis of the residual lumen of a stenosis and its extent could be determined more rapidly. Haemodynamic quantification of stenoses by standard duplex sonography may be difficult because of limited sample volume and error in estimation of angle, whereas colour Doppler allows semiquantitative estimation of haemodynamics. Standard duplex sonography permits good analysis of vessel wall over a limited distance and quantification of velocity; colour Doppler affords overall demonstration of turbulence, acceleration and backward flow.     

Renal transplant pyelocaliectasis: role of duplex Doppler US in evaluation

To distinguish the obstructed from the nonobstructed dilated collecting system of transplanted kidneys without interventional diagnostic measures, the authors prospectively evaluated duplex Doppler analysis (determination of resistive index [RI]) in 35 renal transplant patients with pyelocaliectasis. Proof of the presence or absence of obstruction was obtained at interventional procedures in 18 patients and at clinical follow-up in 17. Thirteen kidneys were obstructed (mean RI, .81 +/- .06), while 22 had nonobstructive dilatation (mean RI, .66 +/- .07). The RI difference was statistically significant (P less than or equal to .01). Of 21 kidneys with a normal RI, only two had obstruction. In both of these, the obstruction was associated with a significant peritransplant collection of fluid due to a ureteral leak. In the seven obstructed transplanted kidneys with follow-up, the mean RI was .82 +/- .06 before nephrostomy and .67 +/- .05 after nephrostomy. Obstruction was a common cause of an elevated RI (greater than or equal to .75). Other causes of transplant dysfunction can be associated with an elevated RI and nonobstructed dilatation. More important, a normal RI should strongly argue against obstruction unless a ureteral leak is also present.     

Renal interlobar artery parameters with duplex Doppler sonography and correlations with age, plasma renin, and aldosterone levels in healthy children

OBJECTIVE: The objectives of this study were to compare and make correlations between age and Doppler parameters of the interlobar arteries, including synchronously obtained plasma renin and aldosterone levels and to obtain new normative data regarding acceleration time in healthy children from neonates to 16 years. SUBJECTS AND METHODS: One hundred sixty-nine healthy children (72 girls and 97 boys) were classified into four groups: group 1 (< 1 year; n = 34), group 2 (range, 1-6 years; n = 48), group 3 (range, 6-12 years; n = 50), and group 4 (range, 12-16 years; n = 37). Blood samples from the renin and aldosterone were collected in the morning after bed rest and fasting. The resistive index (RI), pulsatility index (PI), and the acceleration time of the renal interlobar arteries with duplex Doppler sonography, including both kidney longitudinal lengths with grayscale sonography, were evaluated. One-way analysis of variance with the least significant difference post-hoc test and Pearson's correlation test were used to compare the differences between groups and to make correlations, respectively. An independent-sample t test was used to evaluate the differences between all parameters based on sex and to compare the left and right kidney longitudinal lengths in each group. RESULTS: The RI, PI, and acceleration time were statistically significant in between-group comparisons. Only in group 4 was acceleration time not statistically significant compared with groups 2 and 3. Plasma renin levels were significantly higher in group 1 compared with groups 2 (p < 0.03) and 4 (p < 0.0001); in group 2 compared with group 4 (p < 0.05); and in group 3 compared with group 4 (p < 0.01). The plasma aldosterone levels were significantly higher only in group 1 compared with groups 2 (p < 0.001), 3 (p < 0.008), and 4 (p < 0.0001). The RI correlated linearly with the PI, plasma renin levels, and aldosterone levels and correlated inversely with acceleration time. Age had a negative correlation with the RI, PI, plasma renin levels, and aldosterone levels and correlated positively with acceleration time. There were no statistically significant differences between all parameters based on sex and no significant difference found between the right and left kidney longitudinal lengths in each group. CONCLUSION: The RI in children up to 54 months old is higher than in adults. Therefore, the adult mean renal RI criterion of 0.70 should be applicable to children 54 months old and older. We showed that the age dependency of the RI was directly related to that of plasma renin and aldosterone levels in healthy children in whom Doppler parameters and blood analysis were evaluated synchronously.     

Combined use of duplex sonography and CW Doppler in diseases of the carotid arteries

740 patients with findings of cerebrovascular insufficiency were investigated by duplex sonography and frequency-analysing cw doppler. In 620 pathological arteries not stenosing lesions of the carotid bifurcation were found most frequently (93%). In 35% moderate-severe stenoses of the a. carotis interna were diagnosed. The advantage of duplex sonography and cw doppler in combination is the addition of both methods, so that a very reliable diagnosis of the extracranial carotis is possible.     

Thrombosis of upper extremity thoracic inlet veins: diagnosis with duplex Doppler sonography

Duplex Doppler sonography of the axillary, subclavian, internal jugular, and brachiocephalic veins was performed in 20 normal volunteers and in a series of 22 consecutive patients with suspected venous thrombosis. When normal, these vessels had hypoechoic or anechoic lumina, sharply echogenic walls, and characteristic Doppler flow patterns that varied with changes in intrathoracic pressure. Most thrombosed vessels had poorly defined walls and echogenic lumina. All had absent flow on Doppler analysis. Duplex Doppler sonography was positive in all 10 patients subsequently shown to have venous thrombosis by venography or CT. One false-positive result occurred in a technically limited study. Sonography has the advantages of portability, ease of performance, and high patient acceptance. Duplex Doppler has advantages over either continuous-wave Doppler or imaging sonography alone. Our experience suggests that duplex Doppler sonography should be the initial diagnostic study in evaluating suspected thrombosis of the upper extremity thoracic inlet veins.