Gastric Point of Care Ultrasound in Adults: Image Acquisition and Interpretation

Current NPO guidelines do not specifically address patients with delayed gastric emptying or bowel obstruction. Utilizing point-of-care ultrasound to assess the gastric contents allows providers to have more accurate information regarding these patients and appropriately risk stratify their likelihood of pulmonary aspiration. These protocols will hopefully allow perioperative practitioners to better assess the gastric contents of patients requiring sedation or endotracheal intubation.

With more accurate data, the practitioner will be better able to risk stratify and minimize the likelihood of pulmonary aspiration. Portions of this protocol will be utilized to research the gastric emptying patterns of unique patient populations, such as those with diabetes, bowel obstructions, hiatal hernias, or who are taking the novel medication glucagon-like peptide-1 receptor agonists. Begin by positioning the patient in the supine position.

After selecting a low frequency probe, set the preset to abdominal mode. Place the probe on the patient's subxiphoid region in the sagittal plane, orienting the probe marker in a cephalad direction. Next, fan the probe from the patient's left to right until the liver appears on the left side of the screen.

Then visualize a pulsatile aorta in the long axis deep in the image, followed by the gastric antrum, just caudal, and deep to the superficial liver edge. Ensure that the abdominal aorta is positioned at the deeper edge of the image. If the inferior vena cava is observed instead of the aorta, correct the ultrasound beam angle.

If the stomach is visible at the pylorus level rather than the antrum, adjust the probe placement by fanning leftward until the aorta becomes visible. Then identify the muscularis propria of the stomach. For image acquisition, click Acquire to save a video clip of the current sonographic view.

Next, position the patient in the right lateral decubitus for the quantitative estimation of total gastric volume. Obtain an image of the gastric antrum at its maximum expansion containing only clear liquids. Freeze the image.

Then activate the trace tool and trace out the cross-sectional area of the gastric antrum along the outer hyperechoic layer of the wall representing the cirrhosa. Click on Save and use the given formula to estimate the gastric fluid volume. In the subxiphoid sagittal view, the gastric antrum lies coddled to the liver's tip and superficial to the aorta.

In this study, the appearance of the antrum under different conditions as shown. Recently consumed clear liquids create a starry night effect due to refracting light, while solid foods result in a hyperechoic air fluid boundary called the frosted glass appearance. After one to two hours, the air dissipates from the frosted glass image, revealing a hyperechoic heterogeneous content.

Begin by positioning the patient in the supine position. After selecting a low frequency probe, set the preset to abdominal mode. Place the probe on the left mid axillary line in the longitudinal plane of the patient's body to obtain a left upper quadrant or LUQ coronal gastric body view.

Start with image optimization by identifying the spleen and the left hemi diaphragm. Then fan posteriorly from the spleen to identify the kidney. Once these landmarks are identified, angle the transducer in an anterior direction to obtain a view of the gastric body.

Then click Acquire to save a video clip of this sonographic view. For LUQ anterior transverse gastric body view, place the probe on the anterior surface of the patient's abdomen. Then optimize the image by fanning the probe cranial to coddle until the gastric body is seen deep into the spleen.

Then click on Acquire to save a video clip of the current sonographic view. In LUQ coronal view, the gastric body appears anterior to the spleen and the absence of haustra distinguishes it from the large bowel. The LUQ anterior transverse view shows a distended gastric body containing both solid and liquid contents.