Atypical Gastric Ultrasound Appearance Immediately after Food Intake

Gastric point-of care-ultrasound (POCUS) is an emerging clinical tool. Its utility in guiding clinical decision-making relies on the ability to differentiate between the appearance of an empty stomach; fluid-filled stomach (clear versus particulate fluid); ‘early solid’ content; and ‘late solid’ content, with the most accurate imaging obtained when the patient is scanned in the right lateral decubitus (RLD) position [1]. The typical appearance of early solids is often referred to as a ‘frosted glass’ pattern, where the anterior wall of the antrum is visible with large acoustic shadowing posteriorly (Fig. 1a). This appearance is caused by air swallowed during eating, creating a mucosa-air interface indicated by multiple ‘ring-down’ artefacts on the anterior gastric wall which blur the posterior wall [1-4]. In contrast, the appearance of late solids occurs after the air is displaced, and a distended antrum with mixed echogenicity is seen (Fig. 1b). To our knowledge, all published descriptions of gastric ultrasound to date describe the frosted glass appearance immediately after food intake. In a study of six healthy volunteers, all volunteers demonstrated a late solid sonographic appearance when scanned 90 min after ingesting a solid meal [3]. However, the time period over which this occurs is described within the literature as “variable” [2]. Here, we present and discuss atypical gastric ultrasound images captured during a gastric POCUS workshop, immediately after food ingestion in a healthy woman in her early 20s with no relevant medical or surgical history. Initial ultrasound images of a fasted stomach were as expected (Fig. 1c). However, images captured immediately after a small meal showed a late solids appearance (Fig. 1d). This unexpected finding was again confirmed on repeat imaging of the same individual some weeks later. To our knowledge, this is the first report of the complete absence of the characteristic frosted glass appearance immediately after ingestion of food, giving the false appearance of a late solids state. We hypothesise that this is due to a lack of air being swallowed during ingestion. External observation of the subject's chewing and swallowing pattern did not reveal any obvious deviation from normal. It is difficult to comment on the true incidence of this finding, given that studies investigating the sonographic transition from early to late solids appearance have small sample sizes. Coupled with the lack of previous case reports, we believe this atypical appearance to be a rare finding. The clinical significance of this report is that a late solids appearance may be seen immediately after ingestion of food, giving the false impression that approximately 60–90 min has passed since ingestion. Adverse impact on patient care can be avoided if gastric POCUS is subsequently used to confirm an empty antrum, rather than relying on a specific timeframe after ingestion of food. This observation adds to the knowledge base of gastric sonography as it emerges as a routine clinical tool. This report was published with the written consent of the subject. The authors obtained additional written consent for the use of the ‘typical’ gastric ultrasound images. NS is the convener of the POCUS North Shore gastric ultrasound workshop. No external funding declared. Open access publishing was facilitated by The University of Auckland, as part of the Wiley - The University of Auckland agreement via the Council of Australian University Librarians.