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

Evaluation and Management of Urological Complications Following Pediatric Kidney Transplantation: Experience from a Single Tertiary Center

Background/Objectives: Kidney transplantation is the treatment of choice for children with end-stage renal disease (ESRD), but its outcome can be affected by urological complications, with incidence rates of 2.5-25%. The aim of this study was to evaluate the occurrence of urological complications and their management in a cohort of pediatric kidney transplant recipients. Materials and Methods: A retrospective analysis on 178 patients who received a renal transplant at our Pediatric Kidney Transplant Center between 2011 and 2023 was conducted. Demographic and clinical data were analyzed. Urological complications were categorized as early, intermediate, or late based on their onset time. Results: Out of 178 patients, 28 (15.7%) experienced urological complications. Most patients (61%) had a pre-existing uropathy. Early complications (7-30 days) were all obstructive, namely, ureterovesical junction obstruction and perirenal collections. Intermediate complications (1-3 months) comprised ureteral stenosis, symptomatic vesicoureteral reflux (VUR), and obstructive lymphocele. Late complications (>3 months) included symptomatic VUR and ureteral stenosis, with one case leading to ureteral rupture. Early complications were often detected due to acute graft dysfunction, while late ones were mainly identified during routine clinical, laboratory, or ultrasound follow-up. Urological complications requiring surgical or endoscopic therapy were 13.4%. Most ureteral stenoses were treated with initial endoscopic stents, followed by definitive surgery. VUR was treated with endoscopic correction with a high success rate (75%), while open surgery was reserved for cases where initial treatments failed or complications recurred. No clear correlations were found between patient characteristics and risk of urological complication. Urological complications required multiple diagnostic procedures and therapeutic interventions (+2.5 admissions in mean and approximately +EUR 24,000) compared to an uncomplicated post-transplant course. However, they did not significantly impact transplant outcomes, with a graft survival rate comparable to that of the control group. Conclusions: Regular post-transplant follow-up is crucial, especially for patients with known risk factors, to allow for timely detection and treatment of urological complications, avoiding detrimental effects on graft function and improving transplantation outcomes.

Predictive value of contrast-enhanced ultrasonography for the early diagnosis of renal dysfunction after kidney transplantation: A systematic review and meta-analysis

OBJECTIVES

We aimed to evaluate the changes in renal cortical microperfusion and quantitative contrast-enhanced ultrasonography (CEUS) parameters after kidney transplantation, and to determine the evidence-based value of CEUS in predicting renal dysfunction.

METHODS

The Embase, MEDLINE, Web of Science, and Cochrane Library databases were searched for relevant studies published from 2000 to 2023 on the use of CEUS to assess the renal cortical microcirculation after kidney transplantation. Subject terms and related keywords were combined, and a meta-analysis and systematic review were performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines.

RESULTS

The search yielded six studies involving 451 patients with moderate to high overall quality. The peak intensity (standardized mean difference [SMD]: -0.64, 95% confidence interval [CI] -1.13 to -0.15, p = 0.01) of CEUS was significantly lower in patients with renal dysfunction than in those with stable renal function. However, the time to peak (SMD: 0.28, 95% CI 0.04 to 0.52, p = 0.02) was significantly shorter in patients with renal dysfunction than in those with stable renal function. The total renal cortical microperfusion and renal cortical perfusion intensity were decreased, and the perfusion time was prolonged, in patients with renal dysfunction after kidney transplantation.

CONCLUSION

CEUS parameters can reflect real-time changes in renal cortical microperfusion, thus providing a basis for the early diagnosis of renal dysfunction after kidney transplantation.

[Imaging after kidney transplantation in childhood and adolescence]

The ultrasound (US) examination is the most important imaging procedure in the clinical care of children with chronic kidney disease, the assessment before kidney transplantation and in the acute and chronic phase after successful kidney transplantation. In trained hands, particularly with experience in Doppler sonography, US ensures that vascular complications, such as occlusions, thrombosis, stenosis as well as non-vascular complications, e.g., urinary tract dilatation, abscesses, hematomas, urine leaks or lymphoceles, are cost-effectively and rapidly diagnosed at any time. For the diagnosis of acute rejection, the US signs in the intraindividual course are only suggestive, but not specific. The gold standard for the diagnosis of acute rejection is a kidney biopsy. In these cases, US serves to exclude other causes. The use of multimodal techniques, various Doppler techniques and microvascular procedures, such as superb microvascular imaging (SMI) or B‑flow and contrast-enhanced ultrasonography (CEUS), optimizes the imaging in the context of transplantations in children. Magnetic resonance imaging with diffusion-weighed imaging (DWI), magnetic resonance angiography (MRA) and magnetic resonance urography (MRU) as well as functional MRU (fMRU) performed with the administration of gadolinium-containing contrast agents, are part of the extended diagnostics and possibly necessary for surgical planning in the early phase after kidney transplantation and for long-term assessment after transplantation. Excretory urography is associated with ionizing radiation and intravenous administration of iodine-containing contrast medium and is obsolete in children. Computed tomography (CT) using age-adapted and weight-adapted dose protocols is an alternative in emergencies if MRI is not available.