Student Case 1

Case submitted by: Debra S. Gibbons, DVM, MS, DACVR, VCA Alameda East Veterinary Hospital, Denver, CO

Signalment: 9 y MN Great Pyrenees

History: Gagging when he eats and vomiting liquid.

Images: 3 images (right lateral recumbent, left lateral recumbent and VD views of the thorax).

Questions

  • Please comment on exposure technique and positioning.
  • What are the radiographic findings/abnormalities?
  • What is your radiographic diagnosis?

Findings

Exposure and positioning: Radiographic exposure is adequate. Positioning is acceptable, although the caudal lung fields are incompletely included on the right lateral recumbent view and the patient is obliquely positioned on the ventrodorsal view. Radiopaque markers were not included on the lateral views.

Radiographic findings: There is generalized, moderate gas dilation of the caudal cervical and intrathoracic portions of the esophagus.  A poorly defined, ventrally distributed, alveolar pattern is noted in the right cranial and middle lung lobes. The remaining lung lobes are normal. The cardiac silhouette is a normal size and shape, without evidence of chamber enlargement. There is a mediastinal shift of the cardiac silhouette to the right, attributed to obliquity in positioning. The pulmonary arteries and veins are similar in size when compared to each other and have a normal branching and tapering shape. The pleural space is normal. There is mild, multifocal spondylosis of the thoracic spine.

Diagnosis

Radiographic diagnosis: Generalized, acquired megaesophagus with secondary aspiration pneumonia. A work-up for the causes of megaesophagus is recommended.

Follow up imaging findings and images with arrows

The open arrows show the region of alveolar disease in the right cranial lung lobe. The closed arrows outline the dilated esophageal walls. The black arrow shows the tracheal stripe sign.

Discussion

1. Megaesophagus

Congenital and acquired megaesophagus occurs in the cat and dog.  The congenital form may be hereditary in both the dog and cat.  The underlying cause of acquired megaesophagus is often unidentified (idiopathic), although other differential diagnoses for megaesophagus include: thoracic trauma, tetanus, organophosphate toxicity, lead toxicity, myasthenia gravis, polymyositis/polymyopathy, autoimmune disease, hypoadrenocortisism, thymoma, dysautonomia (cats), gastrointestinal disease, primary neuromuscular disease, and possibly hypothyroidism1

Radiographic findings of megaesophagus include:

Lateral views: Tracheal stripe sign created by summation of the ventral esophageal wall with the dorsal tracheal wall; a sharp, soft tissue opaque interface from the thoracic inlet to the ventral aspect of T5 or T6 created by the dorsal wall of the dilated cranial thoracic esophagus abutting the paired longus colli muscles; and a pair of thin, parallel, soft tissue opaque stripes that converge over the diaphragm and cranial abdomen representing the dorsal and ventral walls of the gastric dilated esophagus1

VD views: The dilated, gas-filled esophagus may widen the mediastinum and the caudal thoracic esophagus converges to a V at the hiatus of the diaphragm (arrows).1

2. Aspiration pneumonia

Aspiration pneumonia can present as an acute fulminant illness, or a chronic and insidious process. The materials usually aspirated are acidic stomach contents and food. Normal laryngeal and pharyngeal function typically prevent aspiration, however, certain diseases may alter normal laryngeal-pharyngeal function and predispose to aspiration events. Local or systemic neuromuscular disease, irritation and inflammation of the oropharynx secondary to chronic reflux or regurgitation (i.e., megaesophagus, esophageal obstruction, esophagitis, chronic vomiting), and anesthesia are common causes of aspiration pneumonia.2

Radiographic findings of aspiration pneumonia include:

Ventrally dependent, interstitial to alveolar pattern causing increased opacity of the pulmonary parenchyma. The right cranial and medial lung lobes are most commonly affected.

An alveolar pattern results from abnormal cells or fluid within the terminal air spaces of the lung. Determining the character of the material in the alveolus is impossible radiographically. The features of an alveolar pattern include relatively intense soft tissue opacity per unit area of abnormal lung, air bronchograms, lobar sign, indiscrete margins of the abnormal opacity (unless a lobar sign is present), border effacement of the pulmonary vessels and bronchial walls, and border effacement with the heart or diaphragm.3

References

  1. Watrous, BJ. “Esophagus” in Textbook of Veterinary Diagnostic Radiology, 5th edition.  Edited by Donald E.  Thrall.  Saunders Elsevier, 2007, pp. 506-507.
  2. Nelson, OL. Sellon, RK. “Pulmonary Parenchyma Disease” in Textbook of Veterinary Internal Medicine, 6th edition. Edited by Stephen J Ettinger and Edward C. Feldman. Elsevier Saunders, 2005, p. 1259.
  3. Berry, CR. Graham, JP. Thrall, DE. “Interpretation Paradigms for the Small Animal Thorax” in Textbook of Veterinary Diagnostic Radiology, 5th edition.  Edited by Donald E.  Thrall.  Saunders Elsevier, 2007, pp. 474-474.