TCRN Practice Exam 2026 – Complete Prep for Your Test

Bilateral flank bruising is a classic indicator of retroperitoneal bleeding. This condition occurs when blood accumulates in the retroperitoneal space, which is located behind the peritoneum (the lining of the abdominal cavity). The bruising happens because the retroperitoneal area is supplied by blood vessels that, when ruptured or torn, can lead to bleeding that tracks down to the flanks. The bruising may take time to develop and become evident, but the presence of bilateral flank bruising is strongly associated with significant trauma or injuries that affect the organs located in the retroperitoneal area, such as the kidneys, aorta, or lumbar veins.

In contrast, intraperitoneal bleeding typically does not lead to bilateral flank bruising but rather presents with signs like abdominal distension or rigidity. Conditions like pneumothorax or thoracic aortic injury involve different injury mechanisms where bruising would not appear in the flank specifically. Thus, the presence of bilateral flank bruising is most accurately associated with retroperitoneal bleeding.