ABSTRACT
Various (99m)Tc DTPA scintigraphic quantitative parameters for renal graft function assessment have been recommended, but none is universally accepted. In this study, 439 dynamic renal transplant scintigraphies (DRTS) were retrospectively analysed. In the first set of studies, four observers analysed the 47 random DRTS and interobserver agreement of eleven derived parameters was assessed. In the other set of studies, 181 instances of DRTS, performed on 127 recipients with renal biopsies within five days of each other were selected for correlation with pathology. Hilson's Perfusion index (HI), ΔP, P:Pl, P:U & T10 were selected for this analysis. The pathologies were categorized into renal vascular compromise (RVC; n = 20), acute tubular necrosis (ATN; n = 40), vascular rejection (VR; n = 34), interstitial rejection (IR; n = 33), normal (NOR; n = 36) and unclassified pathologies (n = 18). A majority of the parameters showed good Intraclass correlation (ICC). HI differentiated well between grafts with RVC and the remainder of the study cohort, (p < 0.0001; AUC = 0.84); at a cut-off > 278, it had 84% sensitivity and 78% specificity (Likelihood ratio = 3.8). At < 278, it had 98% 'negative' predictive value for RVC. HI also showed reasonable association with VR (p = 0.02; AUC = 0.62) and IR (p = 0.009; AUC = 0.65). However, significant overlap of HI values between various subgroups was noted. Other parameters had good ICC but were not effective in differentiating graft pathologies. Of the measured parameters, only HI proved to be useful for the pathological assessment, particularly in the identification of vascular compromise. This parameter, however, has lower specificity in differentiating the other pathologies.
ABSTRACT
BACKGROUND: Early evaluation of renal allograft prognosis is important for identification and targeted management of 'at-risk' grafts but is difficult in the absence of established tests. Tc-99m diethylene triamine pentaacetic acid renal transplant scintigraphy is a useful noninvasive method for assessing graft function. We aimed to assess the relative role of quantitative scintigraphic parameters in the immediate postoperative period for the assessment of short-term and long-term prognoses. METHODS: Data from 290 dynamic renal transplant scintigraphy procedures, performed on 161 recipients on day 1 (D1) or day 4 (D4) after transplantation, were analysed to derive various perfusion parameters [Kirchner's Index, Hilson's Index (HI), kidney-to-aorta ratio and ΔP] as well as nonperfusion parameters (graft washout t (1/2), P : PI ratio, P : U ratio, R20/3, T10 and T20) using regions of interest within the whole renal graft and iliac artery. Information on graft survival up to 1 year (as a measure of short-term prognosis) and serum creatinine at 1 year (regarded as a predictor for longer-term prognosis) was collected. Mann-Whitney tests, receiver-operating characteristic curve analyses and odds ratios were used to assess the utility of each parameter in stratifying the risk for graft failure within 1 year. Correlations between each parameter and 1-year serum creatinine were tested using Spearman's rank correlation. RESULTS: Eleven grafts failed within 1 year. All perfusion parameters on both D1 and D4 showed significant differences between the failure and survival groups (P=0.026-0.0005). No significant between-group differences were observed for nonperfusion parameters except for R20/3 on D1 (P=0.0298). Receiver-operating characteristic analysis showed moderate accuracy for HI and ΔP on both D1 and D4 (area under the curve: 0.73-0.84); ΔP of longer than 6.0 s on D4 was associated with 24.9 times higher relative risk for graft failure within 1 year (sensitivity 88% and specificity 83%). For the assessment of long-term prognosis, a moderate correlation was found between most perfusion parameters (Kirchner's Index, HI and kidney-to-aorta ratio on both D1 and D4) and 1-year serum creatinine (ρ=0.40-0.50; P ≤ 0.0001). The nonperfusion parameters showed only weak correlation. CONCLUSION: Perfusion assessment using HI and ΔP is useful in the assessment of graft prognosis. This can be achieved as early as D1 and D4 after transplantation.
