Radiographic Signs That Could Save Dogs From Paraquat Poisoning

Thoracic radiographic features of fatal paraquat intoxication in eleven dogs

Yan-Wun Kuo, Lee-Shuan Lin, Yi-Chia Li, Kuan-Sheng Chen

Background

Paraquat is a highly toxic herbicide still used in some countries, with ingestion leading to acute lung injury and typically fatal outcomes in both humans and animals. While its clinical and pathological effects are known, detailed descriptions of thoracic radiographic findings in dogs remain limited. This study aimed to characterize radiographic features of confirmed paraquat intoxication in dogs, in hopes of identifying signs that might aid early diagnosis.

Methods

This retrospective study reviewed cases from two veterinary teaching hospitals in Taiwan between 2014 and 2019. Eleven dogs with confirmed paraquat poisoning based on urine colorimetric assays were included. Thoracic radiographs were assessed for patterns such as pneumomediastinum, interstitial and alveolar opacities, and other thoracic abnormalities. Radiographic evaluations were performed by two observers with experience in veterinary radiology. Clinical data and laboratory findings were also analyzed.

Results

The most common clinical signs were dyspnea (100%) and anorexia (82%). Pneumomediastinum was the most prevalent radiographic finding (91%), followed by symmetrical increased lung opacity (64%), especially in the caudodorsal lung fields. Other features included pneumothorax (27%), pleural effusion (27%), and subcutaneous emphysema (18%). One case also had pneumoretroperitoneum. All dogs died, either naturally or by euthanasia due to clinical deterioration.

Limitations

The study’s retrospective design and small sample size limit generalizability. Only one dog underwent histopathological examination, which restricts correlation between radiographic and pathological findings. Some diagnostic imaging, such as echocardiography or full inspiratory/expiratory radiographs, was not performed due to the critical state of patients.

Conclusions

Pneumomediastinum and diffuse or symmetrical interstitial or alveolar lung patterns are consistent thoracic radiographic features of paraquat intoxication in dogs. In regions where paraquat remains in use, its intoxication should be considered in dyspneic dogs with no history of trauma who show pneumomediastinum on radiographs. Early identification through imaging may guide confirmatory testing and inform prognosis.

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