Acute post-tonsillectomy negative pressure pulmonary edema.

A female, 28-year patient was submitted to tonsillectomy and developed respiratory discomfort immediately after the procedure. At the following day, posteroanterior and lateral chest radiography demonstrated coalescent, poorly defined opacities in both lungs, sparing the periphery and characterizing the so called "butterfly wing" pattern, compatible with a diffuse alveolar process. The cardiac image was normal (Figure 1A). Three days after the procedure, without any use of medication, radiographic images (same views) revealed the opacities disappearance (Figure 1B).

Figure 1

A: Posteroanterior chest radiographic image showing bilateral, coalescent, poorly defined opacities, characterizing the so called “butterfly wing” pattern, which is typical of alveolar process. The cardiac image is normal. These images were acquired on the following day after tonsillectomy. The patient presented with mild dyspnea. B: Posteroanterior chest radiographic image acquired three days after the procedure. Complete resolution of the alveolar process demonstrated on the previous images.

Negative pressure pulmonary edema (NPPE) represents a rare occurrence in surgeries (0.094%), most frequently reported in buccomaxillary-facial and oral surgeries due to the probability of upper airway obstruction(. This condition is divided into two classes, namely, type I NPPE caused by upper airway obstruction such as, for example, post-tracheal extubation laryngospasm, epiglotiditis, tracheal cannula obstruction and postoperative vocal cord paralysis(. Type II NPPE occurs after corrective surgical procedures for chronic airway obstruction such as tonsillar hyperplasia, sleep apnea, tumors and acromegaly(. In such cases, the treatment should be aimed at reverting hypoxia and decreasing the pulmonary fluid volume(. The prognosis is good, with recovery at the first 24 hours.(.

Radiographic and chest CT findings of NPPE include interstitial edema progressing to alveolar edema in more severe cases. Generally, regression of symptoms and radiological finding is observed within two or three days(. Many diseases present with radiological sings of diffuse alveolar process but this is not a specific finding in any of them(. In the present case, the patient was healthy, with no comorbidity at the immediate postoperative period following upper airway surgery (tonsillectomy), presenting spontaneous resolution in only three days. Despite the nonspecificity of the radiological pattern, the preoperative history of the patient and the prompt resolution allowed for ruling out other causes, and NPPE was the only remaining possible diagnosis. Thus, the authors considered to be unnecessary to proceed with the diagnostic investigation with other imaging methods and laboratory tests.