History
A 12-year-old 4.8-kg spayed female domestic shorthair cat presented for a 2-week history of vomiting and a 3-day history of inappetence. The cat was evaluated by the primary veterinarian, who performed abdominal radiographs that were suspicious for a partial gastrointestinal obstruction and recommended that the cat be referred.
On physical examination, the cat was bright, alert, and responsive. Vital signs were within normal limits, and no abnormalities were noted on auscultation or palpation. A blood gases and electrolyte variables analysis (Critical Care Xpress analyzer; Nova Biomedical) was performed and revealed decreased oxygen saturation (89.2%; reference range, 96.5% to 99.9%), hyponatremia (147.0 mmol/L; reference range, 148.1 to 153.4 mmol/L), and hypochloremia (115.9; reference range, 116.0 to 123.3 mmol/L). An abdominal focused assessment with sonography for trauma, triage, and tracking was performed and showed no abnormalities or free fluid. Abdominal radiographs were performed in 3 orthogonal planes (Figure 1).
Right lateral (A), left lateral (B), and ventrodorsal abdominal radiographic projections of a 12-year-old 4.8-kg spayed female domestic shorthair cat evaluated for a 2-week history of vomiting and 3-day history of inappetence.
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Right lateral (A), left lateral (B), and ventrodorsal abdominal radiographic projections of a 12-year-old 4.8-kg spayed female domestic shorthair cat evaluated for a 2-week history of vomiting and 3-day history of inappetence.
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Right lateral (A), left lateral (B), and ventrodorsal abdominal radiographic projections of a 12-year-old 4.8-kg spayed female domestic shorthair cat evaluated for a 2-week history of vomiting and 3-day history of inappetence.
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Diagnostic Imaging Findings and Interpretation
The stomach was normal, and the small intestines were normally distributed and had uniform normal diameter, with no evidence of mechanical obstruction. Incidentally, best seen on the left lateral projection, a thin, curvilinear mineral tissue opaque structure was present in the descending colon. In the region of the accessory lung lobe/caudal mediastinum, there was a large, broad-based, rounded homogenous fat opaque mass (4 X 3 cm), which partially border effaced with the cranial margin of the diaphragm (Figure 2).
Same radiographic projections as in Figure 1. There is a large, broad-based, rounded homogeneous fat opaque mass in the region of the accessory lung lobe/caudal mediastinum that is partially border effacing the cranial margin of the diaphragm (white arrows; A through C). There is a small, curvilinear, thin mineral opaque structure present in the descending colon (black arrow; B).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Same radiographic projections as in Figure 1. There is a large, broad-based, rounded homogeneous fat opaque mass in the region of the accessory lung lobe/caudal mediastinum that is partially border effacing the cranial margin of the diaphragm (white arrows; A through C). There is a small, curvilinear, thin mineral opaque structure present in the descending colon (black arrow; B).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Same radiographic projections as in Figure 1. There is a large, broad-based, rounded homogeneous fat opaque mass in the region of the accessory lung lobe/caudal mediastinum that is partially border effacing the cranial margin of the diaphragm (white arrows; A through C). There is a small, curvilinear, thin mineral opaque structure present in the descending colon (black arrow; B).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Based on the radiographic findings, the main differential diagnoses for the caudoventral thoracic mass included ventral diaphragmatic hernia (such as central tendinous and Morgagni) and primary pulmonary neoplasm (such as bronchogenic carcinoma).
An abdominal ultrasound was performed to further assess the gastrointestinal tract and the fat opaque mass seen in the caudal thorax. The gastrointestinal tract was within normal limits. Cranial to diaphragm, a 4.8 X 3.1-cm broad-based to rounded, mildly heterogenous, hypoechoic mass was appreciated with a 0.7-cm communication into the abdominal cavity. No vascular flow connecting the mass to the liver was seen using Doppler interrogation. The top differential for the hypoechoic thoracic mass was a herniation of abdominal content.
Following that, a thoracic CT was performed for further evaluation. The previously observed caudal thoracic mass was isoattenuating and continuous to the abdominal falciform fat through a small defect within the central tendinous portion of the diaphragm (Figure 3). It was concluded that the falciform fat was herniated into the ventral portion of the caudal mediastinum.
Dorsal plane reconstruction thoracic CT image in the soft tissue window of the cat in Figures 1 and 2. Notice the defect of the diaphragm where the falciform fat content from the cranioventral abdominal cavity courses through to reach the caudoventral mediastinum (closed arrows). Incidentally, the right middle lung lobe is collapsed (open arrows).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Dorsal plane reconstruction thoracic CT image in the soft tissue window of the cat in Figures 1 and 2. Notice the defect of the diaphragm where the falciform fat content from the cranioventral abdominal cavity courses through to reach the caudoventral mediastinum (closed arrows). Incidentally, the right middle lung lobe is collapsed (open arrows).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Dorsal plane reconstruction thoracic CT image in the soft tissue window of the cat in Figures 1 and 2. Notice the defect of the diaphragm where the falciform fat content from the cranioventral abdominal cavity courses through to reach the caudoventral mediastinum (closed arrows). Incidentally, the right middle lung lobe is collapsed (open arrows).
Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.10.0440
Treatment and Outcome
Surgical correction was not pursued. The cat was discharged with maropitant citrate (3.3 mg/kg, PO, q 24 h), ondansetron (1.2 mg/kg, PO, q 8 to 12 h, as needed), and mirtazapine 2% transdermal ointment (1.2 in to the inner surface of the ear pinna, q 48 h). The cat has since been doing well at home and a follow-up appointment was not needed.
Comments
Traumatic diaphragmatic ruptures are more common. A true diaphragmatic hernia occurs when abdominal contents herniate through the diaphragm into the thoracic cavity and are covered by a serous membrane. These herniations occur in regions that are anatomically weaker. Common clinical presentations for a diaphragmatic hernia include respiratory signs, such as dyspnea and coughing, or gastroenteric signs, such as inappetence or vomiting. However, these hernias could also be an incidental finding. The most common cause of a diaphragmatic hernia is trauma. Direct or indirect injuries to the diaphragm could cause a focal diaphragmatic herniation.1 While less common, diaphragmatic hernias may also have a congenital origin. Congenital diaphragmatic hernias commonly occur in aortic hiatus, esophageal hiatus, and caval foramen. Certain abdominal organs or structures, such as the liver, gallbladder, falciform fat, spleen, and stomach, are more likely to herniate depending on the location of the herniation.1,2
The most common differential diagnoses for an accessory lung lobe or caudal mediastinal mass on a thoracic radiograph typically include a cyst, hematoma, abscess, neoplasia or granuloma.3 A retrospective study4 of 7 dogs with caval foramen hernias diagnosed on CT showed that thoracic radiographs, in 6 of 7 (86%) animals, exhibited a dome-shaped, broad-based caudal mediastinal lesions. Given its location, other ventral diaphragmatic hernias, such as central tendinous, Morgagni (retrosternal) or other ventrally located hernia should be considered. In the present report, a large, rounded homogenous fat opaque mass in the region of the accessory lung lobe/caudal mediastinum was noted on thoracic radiographs and was diagnosed as a falciform fat diaphragmatic herniation on CT.
In conclusion, this case shows the importance of including diaphragmatic herniations as a differential when considering an accessory lung lobe or caudal mediastinal mass. Additionally, it is important to consider the use of CT for further evaluation and characterization of diaphragmatic herniations.
References
- 1.↑
Hunt GB, Johnson KA. Diaphragmatic, pericardial, and hiatal hernia. In: Slatter D, ed. Textbook of Small Animal Surgery. 3rd ed. Elsevier Saunders; 2003:471–497.
- 2.↑
Hyun C. Radiographic diagnosis of diaphragmatic hernia: review of 60 cases in dogs and cats. J Vet Sci. 2004;5(2):157–162.
- 3.↑
Thrall DE. The mediastinum. In: Thrall DE, ed. Textbook of Veterinary Diagnostic Radiology. 6th ed. Elsevier Saunders; 2013:554–565
- 4.↑
Kim J, Kim S, Jo J, Lee S, Eom K. Radiographic and computed tomographic features of caval foramen hernias of the liver in 7 dogs: mimicking lung nodules. J Vet Med Sci. 2016;78(11):1693–1697.
