An elderly lady from a high-level care nursing home is brought to ED by ambulance with abdominal pain, fevers, vomiting and diarrhoea.

She has a peritonitic abdomen. She is hypotensive on arrival with a RR of 28 and temp of 38.1

VBG shows a severe metabolic acidosis with a lactate of 9. While awaiting a CT abdomen, a CXR is performed

Case 012 CXR 01

Describe and interpret the Chest X-ray


Don’t be fooled by this CXR.

This x-ray is a great example of the difference between a pneumothorax and a skin fold masquerading as a pneumothorax.

On the right we see a true pneumothorax. We can see a visible visceral pleural edge (a thin sharp white line). There are no lung markings peripheral to this.

On the left there are actually two thin sharp white lines, however these lines are not continuous. If we look closely, we can see lung markings peripheral to these lines.

Aside from skin folds, other causes of pneumothorax masquerades are;

  • Bullae
  • Clothing and bedsheets
  • Calcified pleural plaques
Case 012 CXR 01 label

The CT abdomen was then performed


There is sigmoid diverticulitis.

There is pneumoperitoneum and right sided pneumothorax as seen on her CXR.

Case 012 Abdomen CT label 1
Case 012 Abdomen CT label 2
Case 012 Chest CT 2 label


This unusual case shows perforated diverticulitis with gas tracking from the pneumoperitoneum into the thorax.

In other cases, it is also possible for the gas to track in the other direction, that is, a pneumothorax tracking into the abdomen causing pneumoperitoneum.

This is a rare occurrence, and likely secondary to an underlying defect in the diaphragm.




Dr Leon Lam FRANZCR MBBS BSci(Med). Clinical Radiologist and Senior Staff Specialist at Liverpool Hospital, Sydney

Emergency Medicine Education Fellow at Liverpool Hospital NSW. MBBS (Hons) Monash University. Interests in indigenous health and medical education. When not in the emergency department, can most likely be found running up some mountain training for the next ultramarathon.

Sydney-based Emergency Physician (MBBS, FACEM) working at Liverpool Hospital. Passionate about education, trainees and travel. Special interests include radiology, orthopaedics and trauma. Creator of the Sydney Emergency XRay interpretation day (SEXI).

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