We seek to demonstrate the use of, point of care ultrasound, or POCUS, to evaluate the anatomy and pathology of the abdominal aorta. POCUS has excellent sensitivity and specificity for the evaluation of abdominal aortic aneurysm and excellent specificity for the evaluation of abdominal aortic dissection. Some of the challenges include ensuring POCUS users have adequate training and ensuring they can identify pathology and artifacts with accuracy.
This protocol is comprehensive and can be performed and interpreted by the same individual in less than five minutes. This is faster than computed tomography angiography, especially when the patient is critically ill and not stable enough to leave the critical care area for an imaging test To perform a point of care ultrasound evaluation of the abdominal aorta, select a 2.5 to 3.5 megahertz curvilinear probe, which provides the best visualization for most adults. Alternatively, use the phased array probe of one to five megahertz, commonly called cardiac probe, which is typically used for echocardiography.
Use the abdominal preset on the machine regardless of the probe used. Set the mode to B mode or two dimensional gray scale, and the depth to 20 centimeters. Adjust the depth once the aorta is visualized to keep the aorta in the midfield of the screen.
Choose a lower frequency range for patients with a high body mass index to improve image acquisition. To begin scanning, position the patient supine with the abdomen exposed. Hip flexion, if tolerated by the patient, relaxes the abdominal muscles and may improve image acquisition.
Apply ultrasound gel to the transducer. Orient the transducer in the transverse plane with the indicator toward the patient's right. Ensure that the indicator position matches the one displayed on the screen.
Place the transducer just distal to the patient's xiphoid process and apply light pressure to visualize the anterior aspect of the vertebra. With its hyperechoic shadow-casting casting, arch. Slide the transducer caudally until the celiac trunk is visualized.
The celiac trunk is short and quickly bifurcates into the hepatic artery and splenic artery, which together form the seagull sign. Capture these images for later review by clicking the button on the system that records clips. Slide the transducer caudally to view the superior mesenteric artery, or SMA.
Coming off the anterior aorta, SMA follows a path parallel to the aorta to course inferiorly. The splenic vein courses anterior to the SMA, and the left renal vein courses between the SMA and the aorta. Measure the AP diameter of the supra renal aorta by optimizing a live image of the aorta in this location, and then pressing the system's freeze button.
Press caliper or measure, and move the track ball or touch pad of the system to the outer edge of the anterior wall, the adventitia, and click select. Next, move the track ball or touch pad again to the outer edge of the posterior wall and click select. Wait for the system to generate a measurement.
Click the button on the system that saves still images to save this image as a still image containing the measurement. Continue scanning in a transverse plane to visualize the entirety of the aorta through the bifurcation, and capture the images. When a live image of the distal aorta is optimized, measure the AP diameter of the infrarenal aorta.
Press caliper or measure and move the track ball or touch pad of the system to the outer edge of the anterior wall, the adventitia, and click select. Move the track ball or touch pad again to the outer edge of the posterior wall and click select. Wait for the system to generate a measurement.
Save the still image as demonstrated previously. Adjust the depth as the abdominal aorta courses caudally through the abdomen becoming more superficial and tapering slightly. Continue scanning caudally through the aortic bifurcation into the left and right iliac arteries, adjusting the depth to maintain the aorta in vertebral body in the middle of the screen.
Capture images while scanning through the bifurcation. When imaging the abdominal aorta in the transverse plane, an aorta measuring greater than three centimeters was considered Aneurysmal. Such aneurysms also showed the presence of a hematoma filling most of the lumen.
The presence of an intimal flap within the lumen of the aorta indicated aortic dissection. Depending on the chronicity of the dissection, the flap was either thin and moved with the pulsations of the aorta, or thickened and had an adjacent hematoma. An acute thoracic aortic dissection was found to extend through the abdominal aorta and into the right iliac artery.
To begin scanning, position the patient supine with the abdomen exposed. Hip flexion, if tolerated by the patient, relaxes the abdominal muscles and may improve image acquisition. Apply ultrasound gel to the transducer.
Place the transducer transversely in the proximal abdomen in the transverse plane with the indicator toward the patient's right. Ensure that the indicator position matches the one displayed on the screen. Starting in the subxiphoid area, scan to obtain a transverse view of the aorta.
Once the transverse view of the aorta is optimized, rotate the probe clockwise with the indicator pointing towards the patient's head. Following the aorta as the image becomes longitudinal on the screen. Acquire images while scanning, caudally, examining for aneurysmal dilations and save these images for later review by clicking the button on the system that records clips.
To obtain a longitudinal view of the aorta in the coronal plane, if possible, position the patient in the left lateral decubitus position for better image acquisition. Place the transducer in the coronal plane at the mid-axillary line on the patient's right with the indicator pointing cranially. Scan the aorta in the coronal plane.
The aorta will be visualized deep into the IVC if both vessels are imaged. The abdominal aortic pseudo thrombus was a reverberation artifact resulting from the reflection of the ultrasound beam between the anterior and posterior walls of the SMA.
