The diagnostic value of Doppler ultrasonography after pediatric kidney transplantation

Ultrasonography (US) plays a major diagnostic role in the pre- and post-transplant evaluation of recipient and donor. In most cases, US remains the only necessary imaging modality. After pediatric kidney transplantation, US can ensure immediate bedside diagnosis of vessel patency and possible postoperative non-vascular complications. Criteria for US diagnosis of kidney vessel thrombosis and stenosis in the transplant will be presented. Non-vascular complications after kidney transplantation include hydronephrosis, hematoma, lymphocele, and abscess. US can detect suggestive, but nevertheless non-specific, acute signs (sudden increase in volume and elevated resistive index), and chronic rejection, which therefore remains a histological diagnosis. US is of little or no help in detection of tubular necrosis or drug toxicity, but it can exclude other differential diagnoses. This educational review provides a practical and systematic approach to a multimodal US investigation of the kidney transplant. It includes a short overview on possible indications for contrast-enhanced ultrasonography (CEUS) in children after kidney transplantation.

ACR Appropriateness Criteria® Renal Transplant Dysfunction

Renal transplantation is the treatment of choice in patients with end-stage renal disease because the 5-year survival rates range from 72% to 99%. Although graft survival has improved secondary to the introduction of newer immunosuppression drugs and the advancements in surgical technique, various complications still occur. Ultrasound is the first-line imaging modality for the evaluation of renal transplants in the immediate postoperative period and for long-term follow-up. In addition to depicting many of the potential complications of renal transplantation, ultrasound can also guide therapeutic interventions. Nuclear medicine studies, CT, and MRI are often helpful as complementary examinations for specific indications. Angiography remains the reference standard for vascular complications and is utilized to guide nonsurgical intervention. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

New Dimensions in Renal Transplant Sonography: Applications of 3-Dimensional Ultrasound

BACKGROUND

The aim of this study is to demonstrate the usefulness of adding 3-dimensional (3D) ultrasound in evaluation of renal transplant vasculature compared to 2-dimensional (2D) Duplex ultrasound.

METHODS

One hundred thirteen consecutive renal transplant 2D and 3D ultrasound examinations were performed and retrospectively reviewed by 2 board-certified radiologists and a radiology resident individually; each reviewed 2D and then 3D images, including color and spectral Doppler. They recorded ability to visualize the surgical anastomosis and rated visualization on a subjective scale. Interobserver agreement was evaluated. Variant anastomosis anatomy was recorded. Tortuosity or stenosis was evaluated if localized Doppler velocity elevation was present.

RESULTS

The reviewers directly visualized the anastomosis more often with 3D ultrasound ((Equation is included in full-text article.)=97.5%) compared with 2D ((Equation is included in full-text article.)=54.5%) [difference in means (DM) = 43% (95% confidence interval (CI) = 36%-50%) (P < 0.001)]. The reviewers visualized the anastomosis more clearly with 3D ultrasound (P < 0.001) [difference in medians = 0.5, 1.0, and 1.0, (95% CI = 0.5-1.0, 0.5-1.0, and 1.0-1.5)]. Detection of variant anatomy improved with 3D ultrasound by 2 reviewers [DM = 7.1% and 8.9% (95% CI = 1%-13% and 4%-14%, respectively) (P < 0.05)]. There was high interobserver agreement [(Equation is included in full-text article.)= 95.3%, (95% CI = 91.9%-98.7%) regarding anastomosis visualization among reviewers with wide-ranging experience.

CONCLUSIONS

Direct visualization of the entire anastomosis was improved with 3D ultrasound. Three-dimensional evaluation improved detection of anatomic variants and identified tortuosity as the likely cause of borderline localized elevation in Doppler velocity. The data added by 3D ultrasound may obviate confirmatory testing with magnetic resonance angiography or computed tomographic angiography after equivocal 2D ultrasound results.

Renal transplant vascular complications: the role of Doppler ultrasound

Improvements in the care of kidney transplant recipients and advances in immunosuppressive therapy have reduced the incidence of graft rejection. As a result, other types of kidney transplant complications, such as surgical, urologic, parenchymal, and vascular complications, have become more common. Although vascular complications account for only 5-10 % of all post-transplant complications, they are a frequent cause of graft loss. Ultrasonography, both in B-mode and with Doppler ultrasound, is a fundamental tool in the differential diagnosis of renal allograft dysfunction. Doppler ultrasound is highly specific in cases of transplanted renal artery stenosis, pseudoaneurysms, arteriovenous fistulas, and thrombosis with complete or partial artery or vein occlusion. A single measurements of color Doppler indexes display high diagnostic accuracy and in particular cases are more useful during the post-transplantation follow-up period. More recent techniques, such as contrast-enhanced ultrasound, undoubtedly increase the accuracy of ultrasonography in the diagnosis of vascular complications involving the transplanted kidney.