Quiz -Ultrasound Knowledge

The aorta is located to the left of the IVC. It has 2 anterior branches, the coeliac axis and the SMA, which arise from the anterior aspect of the aorta inferior to the liver at the level of T12 (so the coeliac axis may not be seen in the unfasted patient). The IVC is thinner walled. It has 1 structure draining anteriorly, the middle hepatic vein, which enters in the liver parenchyma just inferior to the junction with the right atrium.

The IVC is found to the right of the aorta (except in very rare congenital anomalies), but note that both pulsate.

There is a 6cm AAA. Measurements are taken outer wall to outer wall and the largest diameter is the diagnostic measurement. The position of the superficial calliper in the first image could be deeper, depending on whether the wall is thought to be thickened by a plaque, or if it has not been placed correctly on the outer wall. However, this difference will make no difference to the overall interpretation and subsequent patient management.

In addition, the last two images show a hetrogenous mass in the right abdomen suggestive of a large haematoma.

Once an abdominal aortic aneurysm is detected in the clinical setting of ? ruptured AAA then further ultrasound imaging does not usually alter management (ie the detection of the retroperitoneal haematoma suggesting rupture may be interesting but does not alter management). It is extremely rare for colour Doppler imaging to show an active bleed in a ruptured AAA.

If the patient is very unstable then they may need open repair, but this is now uncommon, and rapid CT is usually performed to allow emergency endovascular repair.

Although the images could be improved by adjusting the depth and gain, there is no aortic aneurysm.

AAA is an important differential for renal colic. History (e.g. previous Hx of stones) and examination (?pulsatile mass) can help, but ultrasound can usually rapidly exclude the diagnosis with more certainty. Other differentials for abdominal pain should be considered but if the clinical picture is typical of renal colic (flank pain, haematuria, etc.) and no ‘red flags’ (fever, single kidney, worsening renal function) then CT KUB can be arranged non-urgently or omitted (typical picture in patient with history of recurrent stones) Local protocols vary on which renal colic patients may not require any imaging.

The aorta is not the only longitudinal, pulsatile vascular structure in the abdomen. The IVC is the vessel in the first 2 images and must not be mistaken for the aorta. Starting with transverse imaging will help prevent this. Loop 03 shows fanning right to left from the IVC onto the aorta.

Although this is likely an incidental finding and the symptoms are probably due to mechanical back pain, a slow rupture cannot be excluded clinically so CT angiogram should be performed. The risk of rupture of an aneurysm of this size is high (25% at 6 months) so urgent referral to vascular surgery is recommended even if there is no leak.

As well as looking for a AAA, POCUS may reveal other pathology such as aortic dissection (although it can’t necessarily rule out these other diagnoses).

POCUS can rule out AAA but only if the entire abdominal aorta is imaged.Pocus cannot rule out aortic dissection, although it is less likely (in the setting of a shocked patient)with the findings of a normal abdominal aorta, normal BELS and normal aortic root. In these situations, the clinical presentation and judgment must direct further investigation and management (which may still require a CT angiogram or other imaging).