A 48-year-old man presented to the ED via emergency medical services after experiencing two episodes of syncope following the acute onset of right lower quadrant pain. He was unresponsive at the time of presentation. His vital signs were notable for tachycardia with a heart rate of 130 beats/minute. Although normotensive at initial presentation, the patient’s blood pressure began to fall rapidly. Laboratory values revealed a decreased hemoglobin and hematocrit of 5 g/dL and 18.1%, respectively.
Following his stabilization, a computed tomography (CT) scan of the abdomen and pelvis was performed. Figures 1a and 1b represent selected noncontrast and postcontrast axial images obtained through the lower abdomen/upper pelvis.
What is the diagnosis?