Accurate determination of renal function in mice is a major impediment to the use of murine models in acute kidney injury. The purpose of this study was to determine if early changes in renal function could be detected using dynamic gamma camera imaging in a mouse model of ischemia-reperfusion (I/R) injury. C57BL/6 mice (n= 5/group) underwent right nephrectomy, followed by either 30 min of I/R injury or sham surgery of the remaining kidney. Dynamic renal studies (21 min, 10 sec/frame) were conducted prior to surgery (baseline) and at 5, 24, and 48 h by injection of Tc-99m-MAG3 (~1.0 mCi/mouse) via the tail vein. The percent of injected dose (%ID) in the kidney was calculated for each 10 sec interval after MAG3 injection, using standard region of interest analyses. A defect in renal function in I/R treated mice was detected as early as 5 h after surgery compared to sham-treated mice, identified by the increased %ID (at peak) in the I/R treated kidneys at 100 s (p<0.01) that remained significantly higher than sham-treated mice for the duration of the scan until 600 s (p<0.05). At 48 h, the renal scan demonstrated functional renal recovery of the I/R mice and was comparable to sham-treated mice. Our study shows that using dynamic imaging, renal dysfunction can be detected and quantified reliably as early as 5 h after I/R insult, allowing for evaluation of early treatment interventions.