In an elderly man presenting with abdominal pain and a soft pulsatile mass, what condition is most likely?

The most likely condition in an elderly man presenting with abdominal pain and a soft pulsatile mass is an abdominal aortic aneurysm (AAA). This condition is characterized as a dilation of the abdominal aorta that can become significant enough to feel as a pulsatile mass, especially in individuals over the age of 65, where the incidence is notably higher. The abdominal pain associated with an AAA may be sudden and severe, and the presence of a pulsatile mass, typically felt in the midline of the abdomen, further supports this diagnosis.

In contrast, the other options do not typically present with the combination of symptoms described. Cauda equina syndrome often presents with neurological symptoms and bladder dysfunction rather than abdominal pain and a mass. Acute diverticulitis is usually accompanied by localized pain, often in the left lower quadrant, fever, and changes in bowel habits, but a pulsatile mass would not be characteristic. Finally, while adenocarcinoma of the colon can cause abdominal pain, it would not typically produce a soft pulsatile mass; instead, it may cause a more obstructive or irregular mass, and the pain may not have the specific characteristics associated with an AAA. Therefore, the presentation of abdominal pain along with a soft pulsatile mass strongly