638 - Association of Contrast-Enhanced Ultrasound Perfusion Parameters with Histopathologic Findings in Pediatric Kidney Transplants

Publication Number: 638.3808

Bernarda Viteri, Children's Hospital of Philadelphia, Philadelphia, PA, United States; Tatiana Morales, Childrens Hospital of Philadelphia, Plymouth Meeting, PA, United States; Brenda Laventure, CHOP, Not Hispanic or Latino, PA, United States; Tricia Bhatti, Children's Hospital of Philadelphia and Perelman School of Medicine at The University of Pennsylvania, Philadelphia, PA, United States; Jarcy Zee, Childrens Hospital of Philadelphia, Philadelphia, PA, United States; Laith R. Sultan, Childrens Hospital of Philadelphia, Philadelphia, PA, United States; SANDRA AMARAL, CHOP, Wynnewood, PA, United States; Children's Hospital J. Philadelphia, Children's Hospital of Philadelphia, Philadelphia, PA, United States

Background: Kidney biopsy is the gold standard for diagnosis of kidney transplant dysfunction but is invasive and limited by sampling error.

Objective: Contrast-enhanced ultrasound (CEUS) provides a non-invasive alternative to biopsy for assessing the perfusion of kidney transplant allografts. We compared CEUS parameters with histopathological measures of dysfunction.

Design/Methods: This prospective, single-center study enrolled pediatric kidney transplant recipients aged 6 to 21 years undergoing clinically indicated biopsies from Nov 2020 to Sept 2024. Patients who consented and had no contraindications for CEUS were included. CEUS imaging was performed within 48 hours of the biopsy. After intravenous administration of ultrasound contrast agent (0.03 mL/kg) a 2-minute cine loop of the transplanted kidney was performed. Four parenchymal regions of interest (ROI) were identified in post-processing using Interactive Data Language (IDL) software. IDL depicted the CEUS parameters for each ROI over time: mean transit time (MTT), time to peak (TTP) and peak enhancement (PE). Perfusion index (PI) was calculated. The ROI values were compared to three histopathologic outcomes per Banff 2017 criteria: chronic allograft damage index (CADI) score, rejection, and total inflammation (ti), which was categorized as 0 vs.1-3. A generalized estimating equations model was used to account for repeated measures.

Results: Forty CEUS exams were performed, with two incomplete clips excluded. Thus, 38 exams from 27 subjects (74% male) were analyzed; from 50% surveillance and 50% for-cause biopsies. The median age at the CEUS exam was 15.5 years (IQR: 6). Median (IQR) eGFR was 68.6 (20.3) mL/min/1.73m2, and the median (IQR) time from transplant to biopsy was 14.5 (23) months. Median (IQR) MTT was 57 (41.2) seconds, TTP was 12.69 (13.49) seconds, PE was 136 (28.71), and PI was 27.47 (1.45). Median (IQR) CADI was 2 (2), 25 biopsies (65.8%) had a ti of 0, and rejection was found in 15 biopsies (39.5%). MTT was significantly associated with CADI (β: 0.38 per 10 seconds, p = 0.001) and ti (OR: 1.52, p = 0.01). TTP (β: 0.07, p = 0.002) and PE (β: 0.02, p = 0.04) were also associated with CADI.

Conclusion(s): We demonstrated that as CEUS-derived perfusion parameters, specifically mean transit time, time to peak and peak enhancement increase, CADI also does. Mean transit time was also strongly associated with increasing inflammation, indicating that slower blood flow through tissue is linked to both greater damage and inflammation. These findings suggest that CEUS may play a role as a non-invasive tool for early detection of allograft dysfunction.