Case Author(s): Matt Jaksha, M.D. and Jerold Wallis, M.D. , 8/1/97 . Rating: #D2, #Q3

Diagnosis: Mucous plug

Brief history:

41 year old male in ICU with new onset of atrial fibrillation. Rule out pulmonary embolus.


Anterior, RAO and LAO ventilation(top) and perfusion(bottom) images.

View main image(vq) in a separate image viewer

View second image(xr). CXR from the same day.

Full history/Diagnosis is available below

Diagnosis: Mucous plug

Full 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.


Tc-99m DTPA aerosol and Tc-99m MAA


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.


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.


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.

View followup image(xr). CXR from the following day with improved aeration on the left.

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.

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Organ specific)

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Case number: vq023

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