Final answer:
The most likely diagnosis for a patient with a tearing pain radiating to the lower back, absent femoral pulses, and a pulsatile mass just superior to the umbilicus is an abdominal aortic aneurysm.
Step-by-step explanation:
The patient presenting with a tearing pain radiating to his lower back, absent femoral pulses, and a pulsatile mass superior to the umbilicus is suspected of having an abdominal aortic aneurysm (AAA). This condition is characterized by the dilation of the abdominal aorta, which can lead to a life-threatening rupture if not promptly treated. The symptoms described align with common clinical presentations of an AAA, rather than other conditions like a ruptured appendix, acute pancreatitis, or myocardial infarction, thus making choice A the most likely diagnosis.