Advancements in imaging modalities for post-kidney transplant monitoring: A focus on contrast-enhanced ultrasound.

Early and accurate detection of posttransplant complications is critical for preserving graft function and optimizing long-term outcomes. Although conventional ultrasound (US) is widely used in transplant monitoring, its limitations in assessing microvascular perfusion and early complications have prompted growing interest in contrast-enhanced US (CEUS). CEUS provides real-time, nonnephrotoxic imaging of microvascular perfusion, making it well-suited for kidney transplant patients. We conducted a systematic review of 19 studies evaluating the use of CEUS in kidney transplant monitoring, focusing on its diagnostic accuracy, comparison with conventional US, and its role in detecting vascular complications, rejection, and perfusion abnormalities. CEUS demonstrated high diagnostic performance, with sensitivity up to 90% and specificity up to 95% for detecting vascular complications, such as transplant renal artery stenosis and transplant renal artery or vein thrombosis. CEUS also showed utility in the early detection of acute tubular necrosis and rejection. However, significant variability was noted in CEUS parameters across studies, largely due to differences in imaging software and methodology, highlighting the need for standardization. Despite its potential, the absence of standardized reference values for CEUS parameters remains a barrier to widespread clinical adoption. Further research is needed to establish these benchmarks and optimize CEUS integration into routine transplant surveillance.