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 diuretic duplex Doppler sonography in childhood hydronephrosis

OBJECTIVE: The purpose of this study was to determine the diagnostic value of diuretic duplex Doppler sonography in distinguishing between obstructive and nonobstructive hydronephrosis in children by calculating the resistive indices (RI) before and after administration of furosemide. MATERIAL AND METHODS: We prospectively evaluated 28 kidneys (2 solitary) in 15 patients with unilateral or bilateral neonatal hydronephrosis. All patients underwent diuretic renography and duplex Doppler sonography before and after administration of furosemide. RESULTS: According to the half-time drainage patterns at diuretic renography, 13 kidneys were classified as nonobstructed and 15 as obstructed. At baseline, the mean RI values of nonobstructed and obstructed kidneys were not significantly different (0.66 and 0.64, respectively). Ten minutes after the injection of furosemide, the mean RI values of the nonobstructed and obstructed kidneys were 0.68 and 0.70, respectively. The increase in RI over the baseline 10 min after the diuretic injection was statistically significant (p<0.00001) in the obstructed kidneys. CONCLUSION: The baseline RI value of 0.70 is not a definite value for distinguishing obstructed from nonobstructed systems. An increase in RI of at least 10% over the baseline seems to be a more reliable criterion, especially when it is used in conjunction with diuretic renography.     

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.     

Renal changes from extracorporeal shock-wave lithotripsy: evaluation using Doppler sonography

In this study, duplex Doppler sonography was used to evaluate flow changes within renal intraparenchymal vessels induced by extracorporeal shock-wave lithotripsy (ESWL). We have examined 20 patients with caliceal stones before, 1 h and 24 h after ESWL. Doppler waveforms were obtained both from arteries located near the stone and at least at 3 cm from it, and resistive index (RI) measured. A statistically significant increase of the RI (0.079 ± 0.039 mean increase; P < 0.001) was detected 1 h after ESWL in vessels located near the stone. After 24 h, RI tended to normalize (0.056 ± 0.037 mean decrease; P < 0.001). The residual difference (0.022 ± 0.043; P = 0.399) between mean RI values obtained near the stone before and 24 h after ESWL was mainly due to persistent elevated RI values in three patients with ESWL induced hydronephrosis. No significant RI changes were recognized in intraparenchymal vessels located far from the stone. In all patients, Doppler alterations were not associated with morphologic changes of renal parenchyma. Correspondence to: L. E. Derchi     

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.     

Renal transplant sonography: correlation of Doppler and biopsy results in cellular rejection.

Seventy-one patients with allograft dysfunction had concomitant Doppler sonography and percutaneous biopsy. Forty-one had biopsy proven acute cellular rejection and eight had acute cellular rejection in combination with acute tubular necrosis. Real time ultrasonic appearance and various parameters of Doppler waveform were studied and compared with 30 controls who had a long period of stable function with no previous episodes of rejection or acute tubular necrosis (ATN). Morphological appearances were unhelpful in diagnosing rejection. A resistive index greater than 0.8 in the study group was highly specific for dysfunction but could not differentiate between acute rejection and ATN. However, two patients in the control group of normal transplants had a resistive index of 0.83. An early to mid diastolic notch was highly specific for acute rejection but of low sensitivity. It may be the only Doppler indication of cellular rejection and may be present when the resistive index is in the normal range.     

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.     

Renal transplantation: Use of sonography

The use of sonography in renal transplantation will be reviewed.     

Lower-extremity vascular grafts placed for peripheral vascular disease: prospective evaluation with duplex Doppler sonography

Eighty-five men with 92 vascular grafts placed for peripheral vascular disease of the lower extremity underwent a total of 264 examinations with duplex Doppler over a 2.5-year period. In 64 patients who underwent more than one examination, the total follow-up encompassed 740 months. In 220 native femoral arteries (96.0%) the peak systolic velocity (PSV) was higher than that in the graft. Arteriovenous shunting was associated with a normal PSV and a markedly elevated diastolic component at spectral analysis. Focal fluid collections were common initially near the graft and usually disappeared uneventfully. An average PSV of 32 cm/sec or less was always associated with impending occlusion. The sensitivity of an average PSV of 40 cm/sec or less to indicate impending graft occlusion by the next visit was only 33%; the specificity, 94%. At initial examination, stenoses were associated with high PSV focally in the graft or low PSV with absent diastolic flow.     

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.     

Renal masses--evaluation by amplitude coded colour Doppler sonography and multiphasic contrast-enhanced CT.

OBJECTIVE: To assess the efficacy of amplitude coded colour Doppler US (aCDS) in the evaluation of renal masses as shown by multiphasic contrast-enhanced CT. MATERIAL AND METHODS: Eighty patients (155 kidneys) with suspicion of renal masses underwent aCDS and spiral CT. The findings were classified into normal kidneys, kidneys with tumours, kidneys with cysts, and those with "other findings" (i.e. bleeding, calcifications, inflammation, parenchymal hypertrophy). The aCDS findings were compared to CT results and to histological findings or clinical, laboratory and follow-up data. RESULTS: Eighteen renal cell carcinomas and 8 other tumours were found; 78 kidneys had cysts, 12 polycystic kidneys and 10 fibrotic kidneys were detected, 20 kidneys showed other findings. Diagnostic aCDS data were obtained in 129 kidneys (83.2%) showing pathology with an accuracy of 94%. CT adequately showed pathology in all patients with some diagnostic uncertainty in the evaluation of complicated cysts. CONCLUSION: Though contrast-enhanced multiphasic spiral CT is the method of choice for evaluating renal masses, US including aCDS can provide valuable information, particularly in differentiating vascularized from non-vascularized lesions and in the evaluation of complicated renal cysts.     

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.     

Renal allografts: evaluation by MR imaging

The value of magnetic resonance (MR) imaging in assessing renal transplants was prospectively studied in 45 patients with 46 allografts. Four allografts were imaged at two different times, and separate diagnoses were given for both examinations. Therefore, this study was based on 50 proved diagnoses: nine normally functioning allografts, four allografts with acute tubular necrosis (ATN), 29 with acute rejection, one with chronic rejection, five with cyclosporin nephrotoxicity, and two with local inflammation secondary to adjacent abscess. Twenty-seven of the allografts had concomitant fluid collections. Normal renal structures with preservation of corticomedullary contrast (CMC) on T1-weighted images were demonstrated in all the normally functioning allografts. Decreased or absent CMC on T1-weighted images, reflecting a long T1 relaxation time for cortex, was found to be the most consistent sign of acute renal allograft rejection (27/29). No abnormalities on on MR images were observed in allografts compromised by cyclosporin nephrotoxicity. Hydronephrosis of the renal allograft was easily diagnosed with MR. Perirenal abscess (three cases) and perirenal hematomas (five cases), because of their higher MR signal intensity on T1-weighted images (TR = 0.5 sec, TE = 28 msec), could be differentiated from clinically insignificant postoperative fluid seromas (seven cases), lymphoceles (11 cases), and urinoma (one case).     

Maternal-fetal Doppler sonography: potential or reality

Doppler sonography, in its varying forms, has been used by numerous researchers to evaluate the maternal-fetal circulation. Unfortunately, as can be seen from this review, few sweeping conclusions can be drawn from the literature to date. Doppler certainly seems a worthwhile adjunct in the evaluation of patients with any of a number of abnormalities that affect maternal-fetal circulation. Unfortunately, considering the discrepancies in the literature and the recent controversy regarding the use of pulsed and color Doppler in pregnancy, the examination is often avoided. However, there are certainly instances where Doppler can provide unique and valuable information. In these situations, the prudent use of Doppler should be encouraged.     

FM sonography in diffuse liver disease: prospective assessment and blinded analysis

FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.