EPSS: One Name, two meanings.

The ultrasound image demonstrated the EPSS, i.e. Enhanced Peritoneal Stripe Sign.

This sign is diagnostic of pneumoperitoneum, first described in 1999 by Muradali.

Small amount of free fluid is seen ventral to the liver (blue arrow). The yellow arrow points to the peritoneum, which is usually a single (sometimes described as double) continuous hyperechoic line. As you trace the peritoneum from the left to right, notice it becomes enhanced in the middle of the image.

This enhancement of the peritoneum (red arrow) is caused by the presence of free air that lies just beneath the peritoneum. And we are certain that it is air, rather than some focal peritoneal processes, because this hyperechoic line casts a dirty shadow, typical of soft tissue-air interface. All structures that lie in the shadow (i.e. liver in this case) “disappeared”.

If a picture paints a thousand words, perhaps a video would do even more.

Notice how free air moves beneath the peritoneum: the position of the interface between enhanced and non-enhanced peritoneum changes as the patient breathes. Indeed, this phenomenon is similar to the Lung Point seen in pneumothorax; which the contributor here refers to as the Peritoneal Point. And yes, there is a smaller air bubble just to the left of the Peritoneal Point.

The patient was brought to the operating theatre: the hemo-pneumoperitoneum found by the bedside was caused by a perforated pyloric ulcer. It was repaired and the patient recovered well.

Lesson learnt:

  • Look for EPSS when suspecting perforated viscus.

  • Air is visible on ultrasound; what lies below is not.

  • When “FASTing” a non-traumatic patient, consider the gutters.

There are several other signs of pneumoperitoneum which we will examine them in our future posts, as well as in the abdominal ultrasound course.


Muradali D, Wilson S, Burns PN, Shapiro H, Hope-Simpson D. A specific sign of pneumoperitoneum on sonography: enhancement of the peritoneal stripe. AJR Am J Roentgenol. 1999 Nov;173(5):1257-62


Dr. Toh Hong Chuen

Acute and Emergency Care Centre, Khoo Teck Puat Hospital. Singapore



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