Abdominal Ultrasound


Abdominal Ultrasound, Duodenal Pylorus and Antral Ultrasound, Small Bowel Ultrasound, Abdominal Free Air on Ultrasound

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