Point-of-care ultrasound in the acute abdomen and gastrointestinal emergencies: An evidence-based guide and the case for standardisation

Table 3 The authors’ proposed specification: What a consensus process would need to fix before these applications can be standardised

Consensus item	SBO	Gastric assessment	Free fluid beyond trauma	Biliary tract
Minimum image set	Number of quadrants required for a complete study is undefined; segmental obstruction means an incomplete survey can be falsely negative. Fix: Mandated quadrants and documented images per quadrant	Supine and RLD antral views are used inconsistently; some thresholds are supine-derived and others RLD-derived. Fix: Both positions mandatory, each documented	Number and identity of dependent recesses varies outside the FAST protocol; pelvic views may be omitted in non-trauma scanning. Fix: Defined recess set for the non-traumatic indication	Long-axis and short-axis gallbladder views, wall measurement site and duct view are not standardised. Fix: Mandated views including the point of wall measurement
Measurement convention	No published convention specifies outer-to-outer vs inner-to-inner, plane, or whether maximal or averaged loop diameter is used, a difference capable of exceeding the 2.5 mm separating the 2.5 cm and 2.75 cm thresholds. Fix: Single defined convention	Antral CSA is derived by different formulae and at different antral levels. Fix: One formula, one anatomical level, one patient position per stated threshold	Volume estimation and the distinction between trace, small, moderate and large collections are undefined; agreement falls to kappa 0.48-0.65 for this distinction. Fix: Defined volume categories with anchoring images	Wall thickness is measured at unspecified sites and on discordant scales, > 3 mm in the emergency literature against ≥ 4 mm in TG18. Fix: One threshold, one measurement site, one wall (anterior)
Definition of a positive study	Whether dilatation alone suffices, or dilatation plus abnormal peristalsis, or plus interloop fluid, varies between studies. Fix: Explicit rule for the composite	A positive study means different target volumes in different sources (empty stomach, > 1.25 mL/kg, aspiration-relevant content). Fix: State the target volume with the threshold	Any anechoic fluid vs a clinically significant volume is not distinguished. Fix: Population-specific definition, since physiological pelvic fluid differs by sex and pregnancy status	Number and combination of signs required is unstated; agreement is kappa 0.85 for gallstones but 0.37 for the composite diagnosis. Fix: Defined minimum criteria set, aligned to TG18
Reporting lexicon	Terms for peristaltic patterns and the valvulae sign are used inconsistently across the literature. Fix: Controlled vocabulary with defined terms	Perlas grades 0-2 are well defined but quantitative and qualitative results are reported interchangeably. Fix: Report grade and CSA separately, never as equivalents	Descriptors of volume and location vary. Fix: Standardised recess names and volume categories	Sonographic Murphy sign has no standardised elicitation, defined transducer pressure or accounting for prior analgesia. Fix: Defined elicitation protocol, or removal of the sign from criteria
Reference standard	CT, surgical findings and final clinical diagnosis are used interchangeably across pooled studies. Fix: Single specified standard, or pre-specified stratification by standard	Aspirated volume, endoscopic volume and model-predicted volume are used as equivalents. Fix: One standard; and outcome studies linking measurement to aspiration rather than to volume	Trauma-derived standards (CT, laparotomy) are applied to non-traumatic populations. Fix: Indication-specific reference standard	Final diagnosis, pathology and TG18 give materially different specificity (17.1% vs 85%-94%). Fix: TG18 as the uniform standard, with the index test measured on the same scale
Training volume for credentialing	No application-specific minimum; the attending-resident sensitivity gap is 14.7 percentage points. Fix: Application-specific case minimum with competency assessment	No emergency-setting training standard exists; the available reliability study used three raters and healthy volunteers. Fix: Defined supervised case volume	FAST credentialing exists but is trauma-specific and does not cover non-traumatic indications. Fix: Extension of credentialing to the non-traumatic indication	Credentialing exists in most curricula but is not tied to demonstrated agreement on wall thickness or the Murphy sign. Fix: Competency demonstrated per sign, not per application
Quality assurance	No archived-image review requirement; loop measurement cannot be audited if images are not stored. Fix: Mandatory archiving of the measured loop	No QA mechanism described in any cited source. Fix: Archived antral images with periodic measurement audit	Where archiving exists it is trauma-oriented. Fix: QA review of non-traumatic studies, with attention to small collections	QA review is described in stewardship literature but is not sign-specific. Fix: Periodic audit of wall measurement and of Murphy-sign documentation
Priority reliability studies required	Inter-observer agreement for loop-diameter measurement: No published kappa or ICC was identified for this measurement, on which the entire branch turns	Inter-observer agreement for antral CSA in an emergency population; and any study linking measurement to aspiration rather than to volume	Inter-observer agreement for detecting a small collection in a non-traumatic emergency population, none identified	Inter-observer agreement for millimetre wall-thickness measurement in an emergency setting (none identified) and a second, multicentre study of the sonographic Murphy sign

Each cell states the current position in the literature followed by the specific item a consensus process would need to fix. Statements that no data were identified refer to the searches described in the METHODOLOGY section. CSA: Cross-sectional area; CT: Computed tomography; FAST: Focused Assessment with Sonography for Trauma; ICC: Intraclass correlation coefficient; QA: Quality assurance; RLD: Right lateral decubitus; TG18: Tokyo Guidelines 2018; SBO: Small-bowel obstruction.