Duplex Doppler evaluation of renal allograft dysfunction: Doppler signal quantitation and pathologic correlation

The value of quantitative duplex Doppler sonography in discriminating the different possible causes of renal transplant dysfunction was prospectively studied in 60 patients during 65 episodes of renal function impairment. Final diagnosis at histology was acute rejection (n: 30), acute tubular necrosis (n: 4), cyclosporin nephrotoxicity (n: 16) and chronic rejection (n: 15). Duplex sonography was done the day a percutaneous biopsy was taken and before any therapy was started. Arterial Doppler signals obtained from the segmental, interlobar and arcuate arteries were both morphologically and quantitatively analysed. For quantitative analysis we used the resistive index as proposed by Pourcelot on the one hand, and introduced a variant resistive index on the other hand. Morphological analysis yielded no discriminative value. Comparing both quantitative methods--the resistive index of Pourcelot and the variant resistive index--clearly higher specificities--71% using the variant resistive index, 28% using the resistive index of Pourcelot--for excluding acute rejection from the other possible causes of renal function impairment could be achieved. A nephrectomy was done on 7 patients with severe transplant dysfunction. Microangiographies performed on these nephrectomy specimens were correlated with previous Doppler studies and with histology.     

Duplex Doppler sonography in renal allografts: the significance of reversed flow in diastole

This study was undertaken to assess the significance of diastolic flow reversal seen on duplex Doppler sonograms of patients with renal transplant dysfunction. Earlier studies have evaluated the causes of increased vascular resistance in renal transplants. None, however, have investigated specifically the subset of patients in whom impedance in the renal microcirculation has increased to the degree that retrograde arterial flow is present. In our series, 533 consecutive scans in 270 patients were reviewed. The patients were referred for evaluation of renal transplant dysfunction during a 25-month period. Doppler samples were obtained from main, segmental, and, when possible, arcuate arteries. An episode of reversed diastolic flow was identified in nine patients. Correlation was made with clinical, laboratory, histologic (biopsy in six patients, nephrectomy in three patients), and imaging studies (DTPA scintigraphy in seven patients, angiography in one patient). On the basis of histologic and nephrectomy results, we determined that among the nine patients, four had acute tubular necrosis, three had acute rejection, and two had renal vein thrombosis. One of these patients had both severe rejection and renal vein thrombosis. One additional patient had neither biopsy nor nephrectomy and was not included in the diagnostic groups listed here. Our study suggests that reversed diastolic flow is not specific for either acute rejection or acute tubular necrosis. Reversal of diastolic flow, however, is a poor prognostic sign; nephrectomy was imminent in three of the nine patients. Furthermore, two (22%) patients had renal vein thrombosis, whereas renal vein thrombosis was not found in any of the 261 patients without reversed diastolic flow. Duplex Doppler examinations with reversed diastolic flow should suggest renal vein thrombosis.     

Comparison of Duplex sonography and color Doppler imaging in renal allograft evaluation: a prospective study

A prospective study compared the diagnostic capability of quantitative Duplex sonography (DS) and color Doppler imaging (CDI) in 49 consecutive patients with 50 renal allografts. Sixty five DS examinations and 65 CDI examinations were performed by two independent investigators on two different machines on the same day. The resistive index (RI) was calculated and the color flow of renal arteries was observed up to the arcuate arteries. There was good correlation of RI values obtained by DS and CDI at all vascular sites. Thirty one allografts were functioning stably and 19 were in a state of dysfunction, defined by histology (n = 17). Forty allografts presented with a RI < 0.9 and normal color flow. All five allografts with a pathologic RI 0.9 showed abnormal color flow (missing flow in arcuate and/or interlobar arteries). Five allografts had a RI < 0.9 but abnormal color flow, possibly due to atrial fibrillation, hypertension, heart failure or a combination of these. A normal color flow pattern excludes severe vascular compromise to the allograft. In addition, CDI revealed three biopsy-related vascular lesions; two of them had been missed by DS.     

Duplex sonography of normal renal allografts

Thirty-five patients with normal renal allografts as well as 10 healthy volunteers with normal native kidneys were examined by duplex sonography. Blood flow measurements were performed in the main renal artery as well as in segmental, interlobar and arcuate arteries. In both groups the normal range of variation in blood flow was defined by using the resistive index (RI). Doppler wave forms and RI of main renal arteries were both similar to those of their branches. In renal allografts as well as in native kidneys the blood flow pattern showed a rapid up-slope in systole followed by a gradual down-slope in early diastole, with a persistent flow throughout diastole. In addition, there was no significant difference in the RI between allografted and native kidneys. The interobserver variability was less than 10 per cent. The mean RI was 0.68 using all data points. Vascular rejection in 11 patients could be discriminated significantly (p less than 0.001). Duplex sonography is useful in evaluating renal blood flow. This simple and non-invasive technique seems to be useful in long-term follow-up of renal allograft recipients.     

Doppler sonography in renal diseases

Using Doppler sonography, the circulation of the kidney can now be studied in the living person in various physiologic or pathologic situations. Our understanding of renal hemodynamics, gleaned from experimental animal models as well as human studies, is being enhanced by Doppler examination and the clinical uses are expanding. Some early concepts, sometimes hastily postulated, are being questioned. The highlights of ongoing debates and the results of animal studies that further our understanding of Doppler examinations in patients are the subject of this review.     

Duplex Doppler sonography of the hepatic vein in tricuspid regurgitation

Patients with tricuspid regurgitation may present initially with vague abdominal symptoms and elevated liver enzymes. In the absence of diagnostic sonographic findings, patients may be subjected to an unnecessary invasive liver biopsy for an accurate diagnosis. We recently described the association of the pulsatile portal venous waveform on duplex Doppler sonography with tricuspid regurgitation in 15 patients. In this study I describe the changes in the hepatic venous waveform in these patients and compare the findings with the final diagnosis as determined by Doppler echocardiography (n = 14) or ultrafast CT (n = 1). All patients had clinical findings consistent with liver dysfunction and were referred for sonography to rule out diseases of the liver, biliary tree, or hepatic or portal veins. All patients had persistently dilated hepatic veins and inferior venae cavae. Twenty-four volunteers, 11 of whom had simultaneous ECG tracings, served as a control group. The main findings on the hepatic duplex sonogram in the disease group were a decrease in the size of the antegrade systolic wave with a systolic/diastolic flow velocity ratio of less than 0.6 (n = 4) or reversal of the systolic wave (n = 10). In all volunteers, systolic flow was antegrade and the ratio was more than 0.6. Two diagnoses were false positive and one was false negative. In some patients with sonographic signs of congestive heart failure, duplex Doppler sonography of the hepatic vein may be helpful in the diagnosis of one of the causes of liver dysfunction, tricuspid regurgitation.     

Duplex pulsed Doppler sonography in the differential diagnosis of hepatocellular carcinoma and other common hepatic tumours.

180 previously untreated consecutive patients with liver tumours (308 lesions), including 104 hepatocellular carcinomas (148 lesions), 43 metastases (116 lesions) and 33 haemangiomas (44 lesions), were studied to determine the value of duplex sonography in the differentiation of hepatocellular carcinoma from other tumours. For lesions measuring less than or equal to 5 cm in diameter, hepatocellular carcinoma demonstrated the highest rate and haemangioma demonstrated the lowest rate of Doppler signals from within the lesions. To differentiate malignancy from haemangioma, the presence or absence of Doppler signals from these lesions were used as criteria. The specificity and positive predictive value were very high (100%, 100%), but the sensitivity, negative predictive value and accuracy were low (61.5%, 48.3%, 71.7%, respectively). With one exception, all lesions measuring less than 3 cm in diameter with detectable Doppler signals were hepatocellular carcinoma. Using these results it is possible to differentiate hepatocellular carcinoma from metastases and haemangioma with high sensitivity, specificity, positive and negative predictive value, and accuracy (80.8%, 96.4%, 95.5%, 84.4%, 88.9%, respectively, for metastases; 80.8%, 100%. 100%, 81.5%, 89.6%, respectively, for haemangioma). We conclude that Doppler signals from within a lesion in combination with its size can aid differentiation of hepatocellular carcinoma from two other kinds of common hepatic tumour.     

Soft-tissue lipomas: accuracy of sonography in diagnosis with pathologic correlation

PURPOSE: To retrospectively determine the accuracy of sonography in helping to distinguish soft-tissue lipomas from other soft-tissue masses by using histologic proof as the reference standard. MATERIALS AND METHODS: Institutional review board approval was obtained, and informed consent was waived. Thirty-nine patients who underwent sonographic evaluation of a soft-tissue mass followed by biopsy or resection were retrospectively evaluated. Two musculoskeletal radiologists (readers 1 and 2) reviewed the sonographic images, characterized the masses, and rated the level of confidence in the diagnosis of lipoma by using a five-point scale. A level of confidence was also rated for the prospective sonographic report, which was reviewed and designated as reader 3. Receiver operating characteristic (ROC) curves, including 95% confidence intervals, were generated, and the area under the ROC curve (A(z)) was calculated for each reader. Sensitivity, specificity, and accuracy for each reader were calculated by using a confidence rating of 4 or 5 as positive for lipoma. Weighted kappa analysis was also performed to assess for interobserver variability. RESULTS: Histologic examination yielded 25 lipomas and 14 nonlipomas. The echogenicity of lipomas ranged from hypoechoic to hyperechoic relative to muscle, although most were isoechoic or hyperechoic. A(z) values were 0.79 for reader 1, 0.56 for reader 2, and 0.77 for reader 3. There was no significant difference between the A(z) for each reader and for chance. Interobserver agreement was fair, with a kappa value of 0.35 among the three readers. Sensitivities were 52%, 40%, and 52%, and accuracies were 64%, 49%, and 64% for readers 1, 2, and 3, respectively. CONCLUSION: Sonography demonstrates low accuracy in the diagnosis of soft-tissue lipomas.     

Differential diagnosis of lymphadenopathy: power Doppler vs color Doppler sonography

Our objective was to compare color and power Doppler sonography of superficial lymph nodes. One hundred ninety-three lymph nodes in 161 patients were assessed by color and power Doppler sonography using standardized settings. We tested which modality displayed more intranodal vessels and checked if these differences would have altered the diagnosis. Additional vessels were seen by color Doppler sonography in 18 nodes and by power Doppler sonography in 58 nodes. Amongst those nodes were 15 nodes which showed no vascularization in color Doppler sonography and 23 nodes with only few intranodal flow signals; however, the better sensitivity of power Doppler sonography had no impact on the diagnosis in 42 of 58 nodes. Diagnostic confidence was increased in 7 nodes which showed normal vessels only in power Doppler sonography, although missing flow signals were defined as a benign finding. Pathological vessels were displayed only by power Doppler sonography in 9 nodes, but 6 of these 9 results proved to be false positive. Power Doppler sonography displays more intranodal flow signals than color Doppler sonography, but the diagnostic impact is low because of an increased risk of false-positive results.     

Arteriovenous fistulas in renal transplants: Color Doppler ultrasound observations

One hundred twenty-six new renal transplants were scanned regularly with color Doppler ultrasound (CDU). In 22 (17.5%) of the grafts there was evidence of postbiopsy arteriovenous (AV) fistula during the first 6 months postoperatively. In 14 cases the fistula closed spontaneously. In the remaining eight, the fistula was still present up to 24 months later (four cases) or until the graft failed (four cases). Additionally, 163 established grafts were scanned for evidence of vascular abnormality. AV fistulas were observed in 15 grafts (8%). Circulatory complications of fistulas observed include vascular steal and a possible association with graft vein and artery stenosis.     

Cholecystokinin sonography: lack of utility in diagnosis of acute acalculous cholecystitis

It has been postulated that cholecystokinin sonography may be useful in the diagnosis of acute acalculous cholecystitis in the hospitalized patient. To evaluate this hypothesis, sincalide, a cholecystokinin derivative, was administered to 15 fasting trauma patients who had undergone laparotomy. No biliary or gallbladder disease was found in any patient. Sincalide was slowly administered intravenously, and the gallbladder was examined with ultrasound every 5 minutes for 60 minutes. The average decreases in length, height, and width of the gallbladder were 15%, 23%, and 21%, respectively. In only four of the 15 patients was there a decrease by more than 50% in any of these dimensions. The average decrease in gallbladder volume was 33% (range, 0%-97%), with no change in gallbladder volume in four patients. There is considerable variability in gallbladder response to administration of sincalide in the fasting hospitalized patient. Lack of contraction of the gallbladder after injection of cholecystokinin should not be considered a major criterion in the diagnosis of acute acalculous cholecystitis.     

Duplex Doppler ultrasound in determination of renal artery stenosis

Twenty-six cases of renal artery stenosis were evaluated with Doppler ultrasound using the pulsatile flow index (PFI). To establish normal values, the PFI in 60 renal arteries in 30 healthy volunteers was obtained. Normal values by PFI ranged between 0.48 and 0.71 (mean +/- SD: 0.6 +/- 0.06). In renal artery stenosis the PFI range was 0.72-0.79. The normal upper limit was 0.71. The PFI failed in three patients; however, an ultrasound examination showed secondary renal disease (two patients with stenosis on both sides with a shrunken kidney on one side, and one patient with hypernephroma on the opposite side). The PFI was normal (14 of 14 patients) in patients without angiographic evidence of stenosis or after successful dilatation.     

Amplitude coded-colour Doppler sonography in paediatric renal disease

The aim of our study was to assess the ability of amplitude coded-colour Doppler sonography (ACDS) to depict altered perfusion in paediatric renal disease in a prospective study. Colour Doppler sonography (CDS) and ACDS examinations were performed in 180 renal units (90 patients; age range newborn to 16 years) with unilateral or bilateral renal disease (e. g. reflux nephropathy, renal scars, end-stage renal disease, ureteropelvic junction obstruction, urinary tract infection, renal failure, haemolytic uraemic syndrome, nephrotic syndrome, systemic lupus erythematosus (LE), renal biopsy, congenital dysplasia, tumour/infiltration). The ACDS results were compared with scintigraphy or CT as well as to clinical findings. Amplitude colour-coded Doppler sonography accurately demonstrated normal vasculature in 49 of 51 healthy kidneys ( = 96 %); 3 healthy kidneys could not be evaluated due to motion/artefacts. In 39 of 43 kidneys with focally altered perfusion ACDS could be performed and correctly depicted focally impaired vasculature/perfusion in 35 kidneys ( = 89.7 %). Seventy-three of 83 kidneys with diffusely impaired perfusion could be evaluated by ACDS and altered pattern was correctly depicted in 58 kidneys ( = 79.4 %), with an overall percentage of agreement of 87.1 %. Amplitude CDS appears to be useful in infants and children. Compared with CDS it improves visualisation of especially focally impaired vasculature/perfusion and should be considered a valuable adjunct to conventional investigations. Received: 12 June 1999 Revised: 10 December 1999 Accepted: 11 August 2000     

Arteriovenous fistulas in renal transplants: color Doppler ultrasound observations.

One hundred twenty-six new renal transplants were scanned regularly with color Doppler ultrasound (CDU). In 22 (17.5%) of the grafts there was evidence of postbiopsy arteriovenous (AV) fistula during the first 6 months postoperatively. In 14 cases the fistula closed spontaneously. In the remaining eight, the fistula was still present up to 24 months later (four cases) or until the graft failed (four cases). Additionally, 163 established grafts were scanned for evidence of vascular abnormality. AV fistulas were observed in 15 grafts (8%). Circulatory complications of fistulas observed include vascular steal and a possible association with graft vein and artery stenosis.