Unidentified bright objects of spleen on arterial phase CT: mimicker of splenic vascular injury in blunt abdominal trauma

Özet

PURPOSEWe have described unidentified bright objects of spleen (UBOS), a hitherto undescribed entity, as hyperdense areas on arterial phase (AP) computed tomography (CT) seen in relationto splenic lacerations and are isodense to the normal parenchyma on portal venous phasewith no correlate on digital subtraction angiography (DSA). UBOS mimic splenic vascular injuries like active contrast extravasation and pseudoaneurysm and need to be differentiatedfrom them as it would have implications on patient management. We undertook this study toidentify CT features of UBOS that can differentiate them from splenic vascular injuries and tocalculate their diagnostic accuracy.METHODSThis retrospective study was approved by the institutional ethical committee and the need forinformed consent was waived. Patients with splenic injury who had undergone dual-phase CTand DSA were included. All the lesions that were hyperdense on AP were evaluated for theiroutline, their relation to the adjacent/parallel margins of a laceration (margin sign), string ofbeads appearance, and the presence of adjacent normal parenchyma (adjacent parenchymasign). The Hounsfield unit (HU) of the lesion and the aorta on the AP were also noted. The diagnostic accuracy of various signs for distinguishing UBOS from splenic vascular injuries wascalculated using DSA as the reference standard.RESULTSOf 48 patients, 5 were excluded due to suboptimal quality of the examination or a time difference of more than 6 hours between the CT and DSA. A total of 54 hyperdense lesions weredetected on AP in 43 patients. These were classified as vascular injuries (pseudoaneurysm,n=11; active contrast extravasation, n=11) and UBOS (n=32) based on DSA. The margin sign,string of beads appearance, and ill-defined outline had high specificity (95%, 86%, and 82%,respectively) but low sensitivity (50%, 65%, and 63%, respectively). The adjacent parenchymasign had a moderate sensitivity and specificity of 84% and 77%, respectively. ROC analysisshowed that a difference of 50 HU between the aorta and the lesion had a high sensitivity andspecificity of 88.9% and 90.6%, respectively, with an area under the curve of 0.90.CONCLUSIONAn attenuation difference of over 50 HU between the aorta and the lesion and the presenceof normal adjacent parenchyma had the highest diagnostic accuracy, while an ill-defined outline, string of beads appearance, and margin sign had high specificity but low sensitivity fordifferentiating UBOS from splenic vascular injuries.