Perinephric hematoma: semi-automated quantification of volume on MDCT: a feasibility study Pedram Rezai, Sandra Tochetto, Mauricio Galizia, Vahid Yaghmai Department of Radiology, Northwestern University-Feinberg School of Medicine, Chicago, IL, USA Abstract Background: To evaluate feasibility and reproducibility of quantification of perinephric hematoma volume on multidetector-row CT (MDCT). Methods: Perinephric hematomas in 63 patients (42 males, 21 females, median age: 49 years) imaged with contrast- enhanced MDCT of the abdomen were evaluated. A semi- automated segmentation software was applied to quantify hematoma volume. Reproducibility for quantification of hematoma volume was evaluated by repeated measure- ments in 20 patients. Statistical analyses were performed by using Student’s t test. Interobserver and intraobserv- er variability was evaluated by Bland–Altman plots. P < 0.05 denoted statistical significance Results: Quantification of hematoma volume was feasible in all cases. One step, direct quantification of volume was possible in 21 patients (33.33%) with small hematomas that did not reach upper and lower renal poles (range: 3.12–183.98 mL; mean: 39.92 mL). Quantification of hematoma size was performed indirectly in 42 patients (66.67%) with larger hematomas that extended beyond the renal poles by subtracting the ipsilateral renal volume from the combined kidney and hematoma volumes (range: 27.08–2431.3 mL; mean: 435.31 mL). Mean quantifica- tion time was 45 and 71 s for small and large hematomas, respectively (P < 0.05). Mean intraobserver and interob- server variability for determination of hematoma volume was 0.14% (95% CI, -1.57% to 1.85%) and 2.04% (95% CI, -1.77% to 5.85%), respectively. There was no significant difference in renal volume between ipsilateral and contra- lateral kidneys (P > 0.05). Conclusion: Quantification of perinephric hematoma was feasible from MDCT data in all patients and was reproducible. Key words: Perinephric hematoma—Semi-automated segmentation—Volumetry—Multidetector-row computed tomography Introduction Hemorrhage into the perinephric space may occur spontaneously [1] or secondary to traumatic or iatrogenic injuries [2–4]. In general, computed tomography (CT) is the imaging modality of choice for the evaluation of re- nal injuries [2, 5–8]. Radiological detection and charac- terization play a central role in the evaluation of patients with renal injuries and in the selection of those who need immediate surgical intervention, as opposed to those in whom non-surgical management is possible [2, 3, 8–11]. For instance, classification of renal injury severity according to the American Association for the Surgery of Trauma (AAST) relies mainly on radiological evaluation of renal injury on CT according to the depth of paren- chymal laceration and involvement of vascular and col- lecting systems [8, 12]. Perinephric hematoma size is indicative of the extent of underlying renal vascular injury and affects management [13–15]. An expanding perinephric hematoma usually requires therapeutic he- mostatic intervention [2, 15]. In addition, hematoma size is suggested to be correlated with clinical outcome [16, 17] and its monitoring maybe a useful indicator of treatment efficacy [18]. Furthermore, the decision to transfuse during the non-operative phase of management may be based on the accurate estimation of blood loss based on hematoma size [19]. Estimation of hematoma size is currently either subjective [4] or based on unidi- mensional [15, 17, 20] and bidimensional [14] measure- ments. Compared to unidimensional and bidimensional measurements, volumetric evaluation and quantification of hematoma size provides a more accurate quantifica- tion of blood-loss. The purpose of this study is to Correspondence to: Vahid Yaghmai; email: v-yaghmai@northwestern.edu ª Springer Science+Business Media, LLC 2010 Published online: 22 June 2010 Abdominal Imaging Abdom Imaging (2011) 36:222–227 DOI: 10.1007/s00261-010-9634-4