Correct answer to Q1 is: Heterogenic abdominal free fluid and normal flow in the portal vein

Correct answer to Q2 is: Small bubbles in the free fluid indicating free gas

Correct answer to Q3 is: You call the referring physician immediately and inform him/her about your findings and suggest that he/she consults with an abdominal surgeon.

Discussion

Pneumoperitoneum indicates a possible GI-perforation and you should inform the referring physician immediately and suggest that he/she consults with an abdominal surgeon. The patient’s situation will determine whether further imaging is needed or if the patient should go to theatre. Usually a contrast enhanced CT (CECT) is requested when there is a suspicion of free gas in the abdomen, but ultrasound has a high sensitivity of up to 95% when evaluated by physicians with at least 3 years of abdominal ultrasound experience⁽¹⁾.

In the presented case the referring physician consulted with an abdominal surgeon, who took the patient to the theatre without further diagnostic imaging. The free gas was caused by a perforated duodenal ulcer.

Additional Image

Figure 2: CECT of the abdomen 10 days after surgery shows pneumoperitoneum, a large amount of free fluid and a hematoma between the liver and the pancreas. Also there is a surgical drain with a reported high output.

Additional Discussion

Findings of the above amount of free gas and free fluid 10 days after surgery is unusual and there should be a high suspicion of reperforation of the ulcer, which was the case for the this patient. Reperforation of a perforated ulcer after initial surgery is reported to be around 5.4% (2).

Conclusion

When a patient presents with symptoms of GI-perforation the imaging gold standard is a CT of the abdomen. However, this may be impossible if the patient is unstable. Often the initial imaging modality in patients with abdominal pain is ultrasound. As spontaneous pneumoperitoneum may have a high clinical impact on patient management it is important to be familiar with and recognize the sonographic findings of free intraabdominal gas. In this case the free intraabdominal gas was dispersed between large amounts of free fluid providing a good sonographic window / visualization of the air bubbles. In other cases with less or no free fluid the sonographic findings differ and you may instead see a reverberation artefact, which can be small or large depending on the amount of free gas (3,4).

When scanning the abdomen, keep in mind that you may miss the important finding of free gas if you compress the abdomen too much with the transducer.

Conflicts of interest

The authors declare no conflict of interest

References

1. Nazerian et al. Accuracy of abdominal ultrasound for the diagnosis of pneumoperitoneum in patients with acute abdominal pain: a pilot study. Critical Ultrasound J (2015) 7:15
2. Byrne et al. Short-term outcomes after emergency surgery for complicated peptic ulcer disease from the UK National Emergency Laparotomy Audit: a cohort study. BMJ Open. 2018 Aug 20;8(8):e023721.
3. Jones R. Recognition of pneumoperitoneum using bedside ultrasound in critically ill patients presenting with acute abdominal pain. Am J Emerg Med. 2007 Sep;25(7):838-41
4. Khor M et al. Sonographic detection of pneumoperitoneum. BJR Case Rep. 2017 May 4;3(4)