Thoracic radiographic features of fatal paraquat intoxication in eleven dogs

Abstract

Background: Paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) is a toxic herbicide. Accidental ingestion of paraquat in animals and humans causes respiratory failure and death. Aim: To describe the radiographic features of confirmed paraquat intoxication in a group of dogs and determines whether any identified features can facilitate this diagnosis. Methods: Eleven dogs diagnosed with paraquat intoxication were selected from two institutions between November 2014 and August 2019 comprising five males (all intact) and six females (one intact and five spayed). The mean age was 3.9±2.9 (SD) years and their mean weight was 11.6±5.0 kg. The tentative diagnosis were confirmed through analysis of their urine samples using a colorimetric assay (paraquat concentation 0.39 μg/ml ranging from 0.19-0.65 μg/ml), and their clinical signs were reviewed. Thoracic radiographs were evaluated for the presence of pneumomediastinum, lung patterns (interstitial or alveolar) and their locations (caudodorsal, cranioventral, diffuse, or symmetrical), subcutaneous emphysema, pneumoretroperitoneum, and pneumothorax. Results: The most common clinical signs were dyspnea (11/11, 100%) and anorexia (9/11, 82%). Pneumomediastinum (10/11, 91%) and symmetrically increased lung opacity (7/11, 65%) were the most common radiographic features. Pneumothorax (3/11, 27%), pleural effusion (3/11, 27%), subcutaneous emphysema (2/11, 18%), and pneumoretroperitoneum (1/5, 20%) were the less common findings. None of the dogs survived. Conclusion: Pneumomediastinum and diffuse or symmetrical interstitial or alveolar lung patterns are the most common radiographic features in dogs with paraquat intoxication. Clinical relevance: In countries where this herbicide is not banned, paraquat intoxication should be considered if dogs with no history of trauma present with pneumomediastinum.

Progressive tension pneumomediastinum in an adult miniature schnauzer

“…There is an increased amount of subcutaneous emphysema, most evident along the ventral and left lateral thorax foreign body have been reported as underlying causes of pneumomediastinum. 1,[3][4][5][6][7] The pathophysiology of spontaneous pneumomediastinum has been described by Macklin et al 17 in 1939. A downward pressure gradient from the alveolus to the vascular sheath allows for leakage of air through the ruptured alveoli into the vascular sheaths.…”

“…Pneumomediastinum, defined as the accumulation of air within the mediastinum, is a well-described condition in the human and veterinary literature. [1][2][3][4][5][6][7][8] It is classified as primary or secondary depending on the underlying aetiology. 2 Primary pneumomediastinum, also known as spontaneous pneumomediastinum, is usually a self-limiting condition and resolves within a few days.…”

“…4 Secondary pneumomediastinum frequently resolves with treatment of the underlying cause. 1,[3][4][5][7][8][9][10] Tension pneumomediastinum (TPM) is a rare and potentially fatal complication of pneumomediastinum in which the mediastinal air cannot escape from the mediastinum or is leaking into the mediastinum faster than it can escape. 9,10,[11][12][13] If left untreated, it may lead to severe respiratory distress, cardiovascular compromise and death.…”

“…Pneumomediastinum, defined as the accumulation of air within the mediastinum, is a well‐described condition in the human and veterinary literature 1–8 . It is classified as primary or secondary depending on the underlying aetiology 2 .…”

“…Primary pneumomediastinum, also known as spontaneous pneumomediastinum, is usually a self‐limiting condition and resolves within a few days 4 . Secondary pneumomediastinum frequently resolves with treatment of the underlying cause 1,3–5,7–10 . Tension pneumomediastinum (TPM) is a rare and potentially fatal complication of pneumomediastinum in which the mediastinal air cannot escape from the mediastinum or is leaking into the mediastinum faster than it can escape 9,10,11–13 .…”