Case 11
History
This 41 year old male was admitted with necrotizing pancreatitis. Subsequent
complications include abdominal abscess. He now presents with new onset of
atrial fibrillation. Ventilation-perfusion lung scintigraphy is requested to
rule out pulmonary emboli.
Anterior, RAO and LAO ventilation(top) and perfusion(bottom) images.
Diagnosis: Mucous plug
Radiopharmaceutical:
Tc-99m DTPA aerosol and Tc-99m MAA
Findings:
The ventilation and perfusion of the right lung are normal. There is almost a
complete lack of ventilation and perfusion to the left lung.
The comparison chest radiograph shows diffuse opacification of the left
hemithorax with apparent volume loss.
Discussion:
Although standard interpretation criteria places perfusion abnormalities with
corresponding radiographic abnormalities into the "intermediate"
category, pulmonary emboli would be unlikely to result in the scintigraphic
pattern seen in this case. Mucous plugging of the left mainstem bronchus with
reflex vasoconstriction and volume loss is a more likely explanation for this
appearance. Pneumonia and/or pleural effusion are possible, though these alone
would not explain the left-sided volume loss.
Followup:
After the patient was suctioned via the endotracheal tube, his condition
improved significantly. The next day's chest radiograph showed improvement in
aeration of the left lung.
Major teaching point(s):
Lack of ventilation to an entire lung is unlikely to result from a pulmonary
embolus. Mucous plugging in an intubated patient can cause this finding, and
appropriate clinical measures (e.g. suctioning or bronchoscopy) should be taken.
Differential Diagnosis List
Foreign body, mediastinal/hilar mass, any lesion obstructing the airway.