Answer
The precontrast image (Figure 1c) demonstrates a large and irregular high-density collection within the right upper pelvis (white arrows) and high density free fluid along the left lateral abdominal wall (black arrows). The right psoas muscle is obscured (white asterisk, Figure 1c) when compared to the normal psoas muscle on the contralateral side (black asterisk, Figure 1c). The postcontrast image (Figure 1d) shows the same findings and also reveals an enlarged right common iliac artery (red asterisk) and contrast actively extravasating from the artery (red arrow). These findings indicate the presence of a ruptured common iliac artery aneurysm. Both the enlarged common iliac artery aneurysm (red arrow, Figure 1d) and the extravasated contrast (red asterisk, Figure 1d) were confirmed on the three-dimensional reformats of the CT scan (Figure 1e).
An isolated aneurysm of the common iliac artery is uncommon, occurring in only 1% to 2% of the population—the same frequency as aortic aneurysm.1 However, the risk of rupture of this type of aneurysm is high.2 Patients with common iliac artery aneurysm are typically asymptomatic prior to rupture. However, some patients have reportedly presented with claudication, tenesmus/constipation, sciatica, and lower extremity paresis due to nerve compression, as well as urinary obstruction caused by ureteral obstruction.1,3 Once the iliac artery aneurysm has ruptured, patients typically present with acute abdominal, groin, and/or thigh pain, although isolated testicular pain has been described in the literature.1,4
Treatment for iliac artery aneurysm includes open and endovascular repair, depending on patient presentation and the adjacent structures involved. While mortality is low for patients with a nonruptured common iliac aneurysm, acute rupture is present in approximately one out of three cases, and the surgical mortality rate is as high as 55%.3
The patient presented in this case was taken to the operating room where an angiogram of the right common iliac artery (red arrow, Figure 1f) revealed continued acute extravasation of contrast (red asterisk, Figure 1f). Surgical repair was attempted but the patient did not survive due to complications of hypotension and cardiac arrest.