II. Precautions
- Decreased efficacy in obese patients or in excessive bowel gas
- Abdominal Ultrasound is a developed skill, and higher efficacy and avoidance of pitfalls improves with experience
III. Protocol: Duodenal-Antral Sweep
- Indications: Epigastric Pain Evaluation
- Differentiates Antacid responsive pain (Gastritis, Duodenitis) from other etiologies (Pancreatitis, referred pain)
- Graded compression with focal significant tenderness over the duodenum, pylorus, antrum suggests pain source
- Starting position
- Curvilinear probe over the epigastrium in longitudinal orientation (sagittal axis, 12:00)
- Identify the pylorus as key landmark
- Directly compress pylorus with increasing pressure
- Slide probe gradually into patient's right, over the duodenum
- Follow the pylorus into the duodenum
- Apply graded compression along the path of the duodenum
- Slide probe back over the duodenum, pylorus and over the Stomach antrum
- Slide back over the pylorus and move toward patient's left over the antrum
- Antrum will appear as stack of pancakes when empty
- At each position, apply graded compression
- Upward (cephalad) pressure over the Abdomen will isolate tenderness over the Stomach and Small Bowel
- Posterior pressure will be applied to Pancreas and other deeper structures
IV. Protocol: Small Bowel Evaluation
- Indications
- Evaluate for Small Bowel Obstruction
- Starting position
- Patient may direct position of maximal pain or
- Sweep the Abdomen from side to side to find characteristic fluid filled Small Bowel
- Findings suggestive of Small Bowel Obstruction
- Small Bowel dilation >2.5 cm
- No peristalsis (typically seen in normal Small Bowel on Ultrasound)
- Alternatively, bidirectional (back and forth flow) or whirlpooling (swirling fluid) may be seen
- Skip areas (focal ileus interspersed with peristalsis) may be seen with Gastroenteritis
- Small Bowel wall thickness >4 mm may be seen with Small Bowel ischemia
- Efficacy in Small Bowel Obstruction diagnosis
- Test Sensitivity: 88%
- Test Specificity: 96%
V. Protocol: Abdominal Free Air Evaluation
- Indications
- Evaluate for intraabdominal free-air (e.g. bowel perforation)
- Starting position
- Right upper quadrant at inferior liver edge
- Curvilinear probe in longitudinal orientation (sagittal axis, 12:00)
- Identify the peritoneal stripe (linear white, echogenic line)
- Soft tissue boundary between peritoneum and intraabdominal space
- Findings of intraabdominal free air
- Reverberation (ring-down) artifact below peritoneal stripe (White rays or descending from peritoneal stripe)
- Precautions
- Intraluminal air may be confused with free air (intraluminal air should curve away from the abdominal wall)
- Small amounts of free air may not demonstrate reverberation artifact
- Efficacy in free air diagnosis
- Test Sensitivity: 85%
- Test Specificity: 100%
VI. References
- Bacon and Brader (2018) Crit Dec Emerg Med 32(2): 23-9