Long-Term Prognostic Impact of Contrast-Enhanced Ultrasound and Power Doppler in Renal Transplantation

Variations of renal Doppler indices during the initial 24-hour predict acute kidney injury in patients with sepsis: A single-center observational case-control clinical study

BACKGROUND AND OBJECTIVE

The aim of this retrospective observational case-control study was to examine the significance of different renal Doppler marker variations within the initial 24-hour period as potential predictors of Acute Kidney Injury (AKI) in patients with sepsis.

METHODS

A total of 198 sepsis patients were enrolled and categorized into two groups: the AKI group (n = 136) and the non-AKI group (n = 62). Three renal Doppler indices, Renal Resistive Index (RRI), Power Doppler Ultrasound (PDU) score and Renal Venous Stasis Index (RVSI), were measured within 6h (T0) and at 24h (T1) after ICU admission.

RESULTS

The AKI group had more hypertension patients than the non-AKI group (p = 0.047). The cases of the AKI group showed higher levels of CRP (p = 0.001), PCT (p < 0.001), lactate (p < 0.001), AST (p = 0.003), ALT (p = 0.049), total bilirubin (p = 0.034), BNP (p = 0.019) and cTnI (p = 0.012). The RRI at T1 was significantly higher in the AKI group (p = 0.037). AKI group exhibited a lower incidence of reduced RRI at T1 compared with non-AKI group (p < 0.001). After controlling for age, sex, and BMI through partial correlation analysis, the results indicated significant associations between SA-AKI and CVP (r = -0.473), SOFA score (r = 0.425), lactate (r = 0.378), and RRI reduction (r = -0.344) in sepsis patients. The multivariate logistic regression analysis showed that variables including CVP, SOFA score, CRP, lactate, VIS, and RRI not reduced following 24h of ICU treatment were predictive indicators for early detection of SA-AKI in sepsis patients.

CONCLUSION

CVP, SOFA score, CRP, lactate, VIS, and RRI not reduction following 24h of ICU treatment can be utilized as predictive indicators for early detection of SA-AKI in sepsis patients.

Quantitative ultrasound for non-invasive evaluation of subclinical rejection in renal transplantation

OBJECTIVES

This study aimed to investigate the predictive efficacy of shear-wave elastography, superb microvascular imaging (SMI), and CEUS for allograft rejection in kidney transplants without graft dysfunction.

METHODS

From January 2021 to November 2021, 72 consecutive patients who underwent both allograft biopsy and ultrasound were evaluated. Blood test results were obtained within a week of the ultrasound examinations, which were performed before the protocol biopsy. Resistive index (RI), tissue viscoelasticity, vascular index, and quantitative CEUS parameters were measured. Patients were divided based on biopsy results into the rejection and non-rejection groups.

RESULTS

Among the 72 patients, 21 patients had pathological characteristics of acute rejection. RI of allograft was significantly higher in the rejection group (p = 0.007), compared to the non-rejection group. There were no significant between-group differences in vascular indices of SMI, mean elasticity, and mean viscosity. Meanwhile, among the parameters obtained by the time-intensity curve on CEUS, the cortical and medullary ratios of average contrast signal intensity, peak enhancement, wash-in area AUC, wash-in perfusion index, wash-out AUC, and wash-in and wash-out AUC were significantly different between the two groups (p < 0.05). In the receiver operating characteristic curve analysis for predicting allograft rejection, the AUC was 0.853 for the combination of six CEUS parameters, RI, and blood urea nitrogen.

CONCLUSIONS

Among non-invasive quantitative ultrasound measurements, CEUS parameters are the most useful for diagnosing subclinical allograft rejection. Furthermore, the combination of CEUS parameters, RI, and blood urea nitrogen may be helpful for the early detection of renal allograft rejection.

KEY POINTS

• Among non-invasive quantitative ultrasound measurements, CEUS parameters are the most useful for the diagnosis of subclinical allograft rejection. • On CEUS, the C/M ratios of MeanLin, PE, WiAUC, WiPI, WoAUC, and WiWoAUC are significantly lower in the rejection group; the combination of these showed reliable predictive performance for rejection. • The combination of CEUS parameters, RI, and BUN has a high predictive capability for subclinical allograft rejection.

Contrast-enhanced voiding urosonography (CEVUS) as a safe alternate means of assessing vesicoureteral reflux in pediatric kidney transplant patients

BACKGROUND

Although voiding cystourethrogram (VCUG) is currently the gold standard in VUR evaluation, there is ionizing radiation exposure. Contrast-enhanced voiding urosonography (CEVUS) uses ultrasound contrast agents to visualize the urinary tract and has been reported to be safe and effective in VUR evaluation in children. CEVUS application has yet to be specifically described in VUR evaluation in the pediatric kidney transplant population. The purpose of this study was to report the use of CEVUS and VCUG in evaluating and managing VUR in pediatric renal transplant patients.

METHODS

Retrospective review was conducted for pediatric kidney transplant patients (18 years and younger) who underwent VCUG or CEVUS to assess for transplant VUR from July 2019 through June 2021. Demographic information, reason for VUR evaluation, fluoroscopy time, and postimaging complications were evaluated. Costs of imaging modalities were also considered.

RESULTS

Eight patients were evaluated for transplant VUR during the study period. Of the 3 patients who underwent VCUG, all 3 had VUR (median grade 3). Median fluoroscopy time was 18 s and dose-area product was 18.7 uGy*m² . Of the 5 patients who underwent CEVUS, 4 had VUR (median grade 4). There were no complications for either modality. Based on clinical and radiographic findings, patients were recommended no intervention, behavioral modification, or ureteral reimplantation. The total cost of CEVUS was $800 less than that of VCUG.

CONCLUSION

CEVUS can provide an alternate means of safely evaluating VUR in kidney transplant patients with similar outcomes, potentially lower costs, and no exposure to ionizing radiation.

Contrast-Enhanced Ultrasonography Value for Early Prediction of Delayed Graft Function in Renal Transplantation Patients

OBJECTIVES

Delayed graft function (DGF) is a common early complication after kidney transplantation. The aim of the present study was to evaluate the value of contrast-enhanced ultrasonography (CEUS) in the early prediction of DGF after kidney transplantation.

METHODS

A total of 89 renal transplant recipients were retrospectively enrolled and divided into DGF group or normal graft function (NGF) group according to the allograft function. Conventional Doppler ultrasound and CEUS examination data on the first postoperative day were collected and analyzed.

RESULTS

The resistive indices of segmental and interlobar artery in the DGF group were significantly higher than those in the NGF group (0.71 ± 0.17 versus 0.63 ± 0.08, P = .006; 0.70 ± 0.16 versus 0.62 ± 0.08, P = .004, respectively). The patients experiencing DGF had significantly lower PI-c (14.7 dB ± 6.1 dB versus 18.5 dB ± 3.3 dB, P = .001) and smaller AUC-c (779.8 ± 375.8 dB·seconds versus 991.0 ± 211.7 dB·seconds, P = .003), as well as significantly lower PI-m (12.6 dB ± 5.9 dB versus 15.9 dB ± 3.9 dB, P = .006), shorter MTT-m (30.7 ± 9.4 seconds versus 36.3 ± 7.1 seconds, P = .01), and smaller AUC-m (P = .007). Multivariate analysis demonstrated that PI-c, AUC-c, and MTT-m were independent risk factors for DGF. The area under the receiver operating characteristic curve values of the combined predicted value (PI-c + MTT-m, PI-c + AUC-c + MTT-m) of DGF incidence were bigger than that of PI-c, AUC-c, or MTT-m.

CONCLUSIONS

CEUS parameters of the cortex and medulla have a good value for an early prediction of DGF after renal transplantation.

Diagnostic value of contrast-enhanced ultrasound (CEUS) in kidney allografts - 12 years of experience in a tertiary referral center

BACKGROUND

B-Mode and Doppler ultrasound are standard diagnostic techniques for early postoperative monitoring and long-term follow-up of kidney transplants. In certain cases, contrast-enhanced ultrasound (CEUS) is used to clarify unclear Doppler findings.

OBJECTIVE

To investigate the diagnostic performance of CEUS in the workup of renal allograft pathologies.

METHODS

A systematic search for CEUS examinations of renal transplants conducted in our department between 2008 and 2020 was performed using the following inclusion criteria: i) patient age ≥18 years and ii) confirmation of diagnosis by biopsy and histopathology, imaging follow-up by CEUS, contrast-enhanced computed tomography (ceCT), contrast-enhanced magnetic resonance imaging (ceMRI), or angiography, or intraoperative findings. Exclusion criteria were: i) CEUS performed in the setting of a study and ii) CEUS for other indications than dedicated renal transplant examination. Statistical analysis was performed separately for subgroups with different indications (focal vs non-focal).

RESULTS

Overall, 78 patients were included in the statistical analysis, which revealed high sensitivity (92.2%, 95% -confidence interval [CI] 81.5-96.9%) and high specificity (88.9%, 95% -CI 71.9-96.1%) of CEUS.

CONCLUSIONS

The high diagnostic performance demonstrated here and the superficial location of kidney allografts advocate the additional use of CEUS in the follow-up of renal transplant recipients.

Quantitative contrast-enhanced ultrasound for the differentiation of kidney allografts with significant histopathological injury

OBJECTIVE

To identify specific quantitative contrast-enhanced ultrasound (CEUS) parameters that could distinguish kidney transplants with significant histopathological injury.

METHODS

Sixty-four patients were enrolled in this prospective observational study. Biopsies were performed following CEUS and blood examination.

RESULTS

28 biopsy specimens had minimal changes (MC group), while 36 had significant injury (SI group). Of these, 12 had rejection (RI group) and 24 non-rejection injury (NRI group). In RI and NRI groups, temporal difference in time to peak (TTP) between medulla and cortex (ΔTTPm-c) was significantly shorter compared to the MC group (5.77, 5.92, and 7.94 s, P = 0.048 and 0.026, respectively). Additionally, RI group had significantly shorter medullary TTP compared to the MC group (27.75 vs. 32.26 s; P = 0.03). In a subset of 41 patients with protocol biopsy at 1-year post-transplant, ΔTTPm-c was significantly shorter in the SI compared to the MC group (5.67 vs. 7.67 s; P = 0.024). Area under receiver operating characteristic curves (AUROCs) for ΔTTPm-c was 0.69 in all patients and 0.71 in patients with protocol biopsy.

CONCLUSIONS

RI and NRI groups had shorter ΔTTPm-c compared to the MC group. AUROCs for both patient groups were good, making ΔTTPm-c a promising CEUS parameter for distinguishing patients with significant histopathological injury.

Imaging of Renal Transplant Complications throughout the Life of the Allograft: Comprehensive Multimodality Review

The kidney is the most commonly transplanted solid organ. Advances in surgical techniques, immunosuppression regimens, surveillance imaging, and histopathologic diagnosis of rejection have allowed prolonged graft survival times. However, the demand for kidneys continues to outgrow the available supply, and there are efforts to increase use of donor kidneys with moderate- or high-risk profiles. This highlights the importance of evaluating the renal transplant patient in the context of both donor and recipient risk factors. Radiologists play an integral role within the multidisciplinary team in care of the transplant patient at every stage of the transplant process. In the immediate postoperative period, duplex US is the modality of choice for evaluating the renal allograft. It is useful for establishing a baseline examination for comparison at future surveillance imaging. In the setting of allograft dysfunction, advanced imaging techniques including MRI or contrast-enhanced US may be useful for providing a more specific diagnosis and excluding nonrejection causes of renal dysfunction. When a pathologic diagnosis is deemed necessary to guide therapy, US-guided biopsy is a relatively low-risk, safe procedure. The range of complications of renal transplantation can be organized temporally in relation to the time since surgery and/or according to disease categories, including immunologic (rejection), surgical or iatrogenic, vascular, urinary, infectious, and neoplastic complications. The unique heterotopic location of the renal allograft in the iliac fossa predisposes it to a specific set of complications. As imaging features of infection or malignancy may be nonspecific, awareness of the patient's risk profile and time since transplantation can be used to assign the probability of a certain diagnosis and thus guide more specific diagnostic workup. It is critical to understand variations in vascular anatomy, surgical technique, and independent donor and recipient risk factors to make an accurate diagnosis and initiate appropriate treatment.^©RSNA, 2019.

Current status of imaging diagnosis in the transplanted kidney. A review of the literature with a special focus on contrast-enhanced ultrasonography

Objectives

Ultrasonographic scanning is currently the most widespread imaging diagnostic procedure. The method provides real-time morphological, vascular and elastographic information in a non-invasive manner. In recent years, harmonic vascular examination has become accessible using intravenous contrast agents. In urological pathology, this procedure is used in the detection and evaluation of vascular and ischemic complications, in the classification of complex cysts according to the Bosniak system, also in the renal lesions with uncertain etiology and in acute pyelonephritis for the detection of abscesses. The contrast agent (SonoVue) is angiospecific and can be used in patients transplanted immediately after surgery without adverse effects or impaired renal function. Thus, it is desirable to be used in the nephrological pathology of the renal graft and to develop diagnostic models based on the evaluation of renal microvascularization, as well as the quantitative data resulting from the graphical representation of the specific parameters. The purpose of this review is to evaluate the current state of the literature regarding the place and role of contrast substance ultrasound in the early diagnosis of acute renal graft dysfunction and to make a differential diagnosis of this pathological entity.

Method

This review quantifies the role of contrast ultrasound in the diagnosis of acute complications of the renal graft. The research was conducted based on the databases PubMed, MedScape, Cochrane, according to the search criteria such as contrast-enhanced ultrasound + kidney transplant, “time intensity curves” + “kidney transplant”, filtered for the period 2004–2018.

Results

In the nephrological pathology of the renal graft, contrast-enhanced ultrasound is a valuable tool, superior to Doppler ultrasound in predicting the evolution of the renal graft, identifying very small early defects in renal microvascularization. A number of studies succeeded in identifying acute graft dysfunction, some of which establish its etiology - humoral rejection versus acute tubular necrosis. On the other hand, the contrast-enhanced ultrasound parameters do not have the ability to distinguish between cellular and humoral rejection.

Conclusions

If, at present, the histopathological examination is the only one that can differentiate with certainty the cause of acute renal graft dysfunction, we consider that contrast-enhanced ultrasound, as a non-invasive imaging technique, opens a favorable perspective for increasing the survival of the renal graft and decreasing the complications in the renal transplant. The combination of other ultrasound techniques, together with contrast-enhanced ultrasound, could lead to the development of new diagnostic models.

State-of-the-Art Renal Imaging in Children

Imaging modalities for diagnosing kidney and urinary tract disorders in children have developed rapidly over the last decade largely because of advancement of modern technology. General pediatricians and neonatologists are often the front line in detecting renal anomalies. There is a lack of knowledge of the applicability, indications, and nephrotoxic risks of novel renal imaging modalities. Here we describe the clinical impact of congenital anomalies of the kidneys and urinary tract and describe pediatric-specific renal imaging techniques by providing a practical guideline for the diagnosis of kidney and urinary tract disorders.

Renal vascular resistance is increased in patients with kidney transplant

BACKGROUND

Despite improvement in short-term outcome of kidney transplants, the long-term survival of kidney transplants has not changed over past decades. Kidney biopsy is the gold standard of transplant pathology but it's invasive. Quantification of transplant blood flow could provide a novel non-invasive method to evaluate transplant pathology. The aim of this retrospective cross-sectional pilot study was to evaluate positron emission tomography (PET) as a method to measure kidney transplant perfusion and find out if there is correlation between transplant perfusion and histopathology.

METHODS

Renal cortical perfusion of 19 kidney transplantation patients [average time from transplantation 33 (17-54) months; eGFR 55 (47-69) ml/min] and 10 healthy controls were studied by [15 O]H2O PET. Perfusion and Doppler resistance index (RI) of transplants were compared with histology of one-year protocol transplant biopsy.

RESULTS

Renal cortical perfusion of healthy control subjects and transplant patients were 2.7 (2.4-4.0) ml min- 1 g- 1 and 2.2 (2.0-3.0) ml min- 1 g- 1, respectively (p = 0.1). Renal vascular resistance (RVR) of the patients was 47.0 (36.7-51.4) mmHg mL- 1min- 1g- 1 and that of the healthy 32.4 (24.6-39.6) mmHg mL- 1min-1g-1 (p = 0.01). There was a statistically significant correlation between Doppler RI and perfusion of transplants (r = - 0.51, p = 0.026). Transplant Doppler RI of the group of mild fibrotic changes [0.73 (0.70-0.76)] and the group of no fibrotic changes [0.66 (0.61-0.72)] differed statistically significantly (p = 0.03). No statistically significant correlation was found between cortical perfusion and fibrosis of transplants (p = 0.56).

CONCLUSIONS

[15 O]H2O PET showed its capability as a method in measuring perfusion of kidney transplants. RVR of transplant patients with stage 2-3 chronic kidney disease was higher than that of the healthy, although kidney perfusion values didn't differ between the groups. Doppler based RI correlated with perfusion and fibrosis of transplants.

Contrast-enhanced ultrasonography in chronic glomerulonephritides: correlation with histological parameters of disease activity

PURPOSE

To compare contrast-enhanced ultrasonography (CEUS)-derived time-intensity (TI) curves with histological findings in kidneys of patients affected by chronic glomerulonephritides (GN) in the early stage of disease.

METHODS

Research ethics committee approval and patient written informed consent were obtained. Thirty-one patients who showed clinical and laboratory signs of GN, with preserved renal function, were consecutively enrolled. They underwent kidney CEUS, from which TI curves were obtained, and kidney biopsy. TI curves were compared with clinical data, ultrasound (US) Doppler, and histological parameters.

RESULTS

The persistence of contrast agent signal during the wash-out phase was found to be correlated with the degree of disease activity (p = 0.016) and in particular with the presence of mesangial hyperplasia (p = 0.008). No correlation was observed between TI curves and clinical or Doppler US-derived parameters.

CONCLUSIONS

The persistence of contrast agent signal in the wash-out phase of CEUS appears to reflect a disturbance of perfusion in glomerular capillaries in the early stages of GN. We found that the histological element directly correlated with the prolonged wash-out was mesangial hyperplasia.

Diagnostic Value of Conventional Ultrasonography Combined with Contrast-Enhanced Ultrasonography in Thyroid Imaging Reporting and Data System (TI-RADS) 3 and 4 Thyroid Micronodules

BACKGROUND The present study was conducted to investigate the diagnostic performance of conventional ultrasonography (US) combined with contrast-enhanced ultrasonography (CEUS) in thyroid micronodules with thyroid imaging reporting and data system (TI-RADS) category 3 and 4. MATERIAL AND METHODS The features of conventional US and CEUS ion 102 case of thyroid micronodule samples, which were diagnosed based on pathological and clinical examination, were retrospectively analyzed. Logistic regression analysis was used to analyze the diagnostic accuracy in malignant thyroid micronodules. Receiver operator characteristic (ROC) curve was used to assess the performance of those 2 technologies. RESULTS A significant difference in age was found between the benign and malignant groups. The benign and malignant groups showed significant differences in shape, margin, aspect ratio (A/T) ≥1, microcalcification, suspicious lymph gland, enhancement time, enhancement pattern, enhancement intensity, nodule sizes, enhancement margins, and rim-like enhancement. Logistic regression analysis of conventional US showed that A/T ≥1, irregular shape, microcalcification, and suspicious lymph glands are risk factors for thyroid micronodules, while logistic regression analysis of CEUS showed that slow enhancement time and absence of rim-like enhancement are risk factors for thyroid micronodules. Logistic regression analysis of conventional US combined with CEUS demonstrated that A/T ≥1, microcalcification, suspicious lymph gland, slow enhancement time, and absence with rim-like enhancement are risk factors. The ROC curve for conventional US, CEUS, and conventional US combined with CEUS were 90.0%, 90.7%, 99.0%, respectively. CONCLUSIONS Our results show that conventional US combined with CEUS had superior diagnostic performance for TI-RADS 3 and 4 thyroid micronodules compared with conventional US and CEUS alone.