A 67-year-old hypertensive man presents with lower abdominal pain and back pain. An expansive abdominal mass is palpated lateral and superior to the umbilicus. What is the best investigation for this patient?
**Core Concept**
A large abdominal mass in a hypertensive patient, particularly one with lower abdominal and back pain, suggests a possible abdominal aortic aneurysm (AAA). This condition involves the dilation of the abdominal aorta, which can lead to rupture and life-threatening bleeding.
**Why the Correct Answer is Right**
The best investigation for a suspected abdominal aortic aneurysm is computed tomography (CT) angiography. This imaging technique provides detailed information about the size and location of the aneurysm, as well as the patency of the surrounding blood vessels. CT angiography involves the injection of a contrast agent, which highlights the aorta and its branches, allowing for precise measurement of the aneurysm and assessment of its risk of rupture. The high sensitivity and specificity of CT angiography make it the gold standard for diagnosing AAA.
**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasound is a useful screening tool for AAA, but it is not as sensitive or specific as CT angiography for detecting and characterizing aneurysms. While ultrasound can provide useful information, it is not the best investigation for this patient.
**Option B:** Magnetic resonance angiography (MRA) is another imaging modality that can be used to diagnose AAA. However, MRA is typically less sensitive than CT angiography for detecting smaller aneurysms and may not provide as much detail about the surrounding blood vessels.
**Option C:** Plain abdominal radiographs are not sufficient for diagnosing AAA. While they may show an abdominal mass, they do not provide enough information about the size, location, or characteristics of the aneurysm.
**Option D:** Angiography involves the injection of a contrast agent into the aorta to visualize the blood vessels. While it can be used to diagnose AAA, it is typically reserved for patients who have already been diagnosed with an aneurysm and require further evaluation or treatment.
**Clinical Pearl / High-Yield Fact**
A key clinical pearl to remember is that a palpable abdominal mass in a hypertensive patient, particularly one with lower abdominal and back pain, is highly suggestive of AAA. Prompt imaging with CT angiography is crucial to rule out this life-threatening condition and guide further management.
**Correct Answer: C. Magnetic resonance angiography (MRA) is another imaging modality that can be used to diagnose AAA. However, MRA is typically less sensitive than CT angiography for detecting smaller aneurysms and may not provide as much detail about the surrounding blood vessels.