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

Table 4 Evidence-versus-proposal matrix for each action node of the integrated algorithm (Figure 1): What the node rests on, and whether it is derived from evidence or proposed by the authors

Algorithm action node	Evidence type	Evidence supporting the node	Status	Ref.
Step 1: Instability/red-flag check precedes any scan	Expert recommendation	Consensus statements on emergency POCUS scope; no comparative trial of scan-first vs resuscitate-first	Authors’ proposal	Kameda and Taniguchi[7], Oto et al[8]
Step 2: Operator competency precondition	Evidence-informed	Operator-level subgroup estimates differ by application and do not all run the same way: For appendicitis the EP subgroup is lower than the pooled estimate on both axes (sensitivity 80% vs 91%, specificity 92% vs 97%), whereas for cholecystitis the EP subgroup matches the pooled sensitivity (71% vs 71%) and exceeds the pooled specificity (92% vs 85%). Competency is therefore required as a precondition because performance is operator-dependent in an application-specific direction, not because EP performance is uniformly lower	Evidence-based (subgroup estimates), authors’ proposal (credentialling requirement)	Huang et al[25], Matthew Fields et al[35]
Step 3: Symptom cluster sets pretest probability and orders the scans	Authors’ construction	No study compares symptom-ordered POCUS sequencing against a fixed protocol	Authors’ proposal	N/A
Biliary branch: Gallstones + sonographic Murphy sign + wall > 3 mm as the rule-in trigger	Evidence-based	Pooled specificity 94.4% (88.2%-97.5%) for EP-performed POCUS; TG18 uses wall ≥ 4 mm	Evidence-based	Yokoe et al[21], Wilson et al[32]
Biliary branch: Negative scan does not exclude cholecystitis	Evidence-based	Pooled EP sensitivity 70.9% (62.3%-78.2%); LR- accordingly poor	Evidence-based	Wilson et al[32]
Biliary branch; fever + jaundice + dilated duct triggers the cholangitis pathway	Guideline-based	TG18 diagnostic criteria (systemic inflammation + cholestasis + imaging) and severity grading	Evidence-based (guideline)	Okamoto et al[81], Kiriyama et al[88]
SBO branch: Dilated loops > 2.5 cm as the rule-in trigger	Evidence-based	Pooled sensitivity 92.4% (89.0%-94.7%), specificity 96.6% (88.4%-99.1%), LR+ 27.5	Evidence-based	Gottlieb et al[9]
SBO branch: 2.75 cm as a candidate refined threshold	Authors’ construction	Proposed in a bedside-threshold analysis; no reliability data exist for bowel-loop diameter at this precision	Authors’ proposal: Explicitly unvalidated	Shokoohi et al[11]
SBO branch, CT still required for transition point, aetiology, ischaemia, perforation	Evidence-based	Consistent statement across the SBO syntheses; POCUS not evaluated for these endpoints	Evidence-based	Gottlieb et al[9], Shokoohi et al[10], Motavaselian et al[30]
Free-fluid branch, free fluid in Morison’s pouch or pelvis as the rule-in trigger	Evidence-based	Ectopic pregnancy cohort; prehospital FAST pooled specificity 0.970 (0.953-0.983)	Evidence-based	Lin et al[19], Moore et al[31]
Free-fluid branch: Ectopic pregnancy excluded only by seeing an intrauterine pregnancy	Evidence-based	Pooled FAST sensitivity 0.74 (0.65-0.81) in blunt trauma; absent free fluid carries no exclusionary value for ectopic pregnancy	Evidence-based	Stengel et al[18], Moore et al[31]
Aorta/renal branch, aortic diameter ≥ 3 cm; POCUS does not identify rupture	Evidence-based	Aneurysm detection sensitivity 98.3%, specificity 99.8%; no pooled estimate for rupture detection	Evidence-based	Shaban et al[34]
Gastric parallel branch: Perlas grade and antral CSA stratify aspiration risk	Evidence-based	IPD meta-analysis: Grade 0/1 gives 98% probability of being below the risk threshold; ED intubation cohort sensitivity 100%, specificity 87%	Evidence-based (against a surrogate endpoint)	Perlas et al[26], Asokan et al[27]
Gastric parallel branch; thresholds are position- and population-specific, not interchangeable	Evidence-based	Distinct CSA thresholds by position and population across the source studies	Evidence-based	Perlas et al[26]
Third exit; non-diagnostic study treated separately from a negative study	Authors’ construction	No source study reports a distinct action pathway for non-diagnostic examinations	Authors’ proposal, a principal original contribution	N/A
Serial scanning after an interval where the picture is evolving	Expert recommendation	No comparative evidence for serial abdominal POCUS in this setting	Authors’ proposal	N/A
Secondary redirect applications when the entry scan is negative or non-diagnostic	Evidence-based (component estimates), authors’ construction (the redirect rule)	Appendicitis EP sensitivity 80%, specificity 92%; hydronephrosis sensitivity 70.2%; AAA detection 98.3%	Mixed, estimates evidence-based, sequencing proposed	Shaban et al[34], Matthew Fields et al[35], Miller et al[36], Wong et al[37]
Governing principle, every application rules in better than it rules out	Evidence-based	Direct consequence of the sensitivity/specificity asymmetry documented in Table 1	Evidence-based	Gottlieb et al[9], Shokoohi et al[10], Stengel et al[18], Lin et al[19], Huang et al[25], Wilson et al[32]

N/A in the reference column indicates that no source study addresses the node, which is therefore an authors’ proposal rather than an evidence-derived step. It is provided so that a reader can separate the evidence synthesised in this review from the pathway the authors construct from it; the algorithm as a whole has not been prospectively validated. AAA: Abdominal aortic aneurysm; CSA: Cross-sectional area; CT: Computed tomography; ED: Emergency department; EP: Emergency physician; IPD: Individual-patient-data; LR+: Positive likelihood ratio; LR-: Negative likelihood ratio; SBO: Small-bowel obstruction; TG18: Tokyo Guidelines 2018; POCUS: Point-of-care ultrasound; N/A: Not applicable; FAST: Focused Assessment with Sonography for Trauma.