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Staci M. Spears Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

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Robin S. White Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

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Marina J. McConkey Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

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History

A 9-year-old 5.1-kg (11.2-lb) neutered male domestic shorthair cat was admitted to the emergency service at the University of Florida Small Animal Hospital because of clinical signs of lethargy and anorexia of 1 week's duration and a single episode of tachypnea. The cat had undergone right-sided pneumonectomy (resulting in removal of most of the right lung) with thoracic omentalization for treatment of pyothorax 4 years earlier. The patient also received a diagnosis of hypertrophic cardiomyopathy 2 months earlier, for which it was being treated with diltiazem.

At the onset of clinical signs a week prior, the cat was brought to a veterinarian at an emergency clinic and was noted to be febrile. Because of the fever, the cat began treatment with enrofloxacin. The following morning, the patient was still lethargic and anorexic, so the cat was brought to its primary (ie, the referring) veterinarian. The referring veterinarian performed abdominal and thoracic focused assessment with sonography for trauma (AFAST and TFAST) and thoracic and abdominal radiography. A scant amount of pleural effusion was detected on ultrasonographic images (not shown).

At the time of emergency admission to the university, physical examination findings were largely unremarkable, with only a slight increase in respiratory effort and a static grade II/VI heart murmur consistent with the cat's history of previously diagnosed hypertrophic cardiomyopathy. Echocardiography, which was undertaken to understand the severity of cardiac disease given the possibility of general anesthesia, revealed mild mitral valve regurgitation and mild left ventricular hypertrophy consistent with hypertrophic cardiomyopathy. No abnormalities were detected on CBC and serum biochemistry analysis. Thoracic and abdominal radiographic images from the referring veterinarian were reviewed (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen and thorax of a 9-year-old 5.1-kg (11.2—lb) neutered male domestic shorthair cat that was evaluated because of clinical signs of lethargy and anorexia of 1 week's duration and a single episode of tachypnea.

Citation: Journal of the American Veterinary Medical Association 252, 12; 10.2460/javma.252.12.1463

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretation

A linear soft tissue opacity is noted extending from the cranial aspect of the abdomen into the right hemithorax (Figure 2). The soft tissue opacity is surrounded by fat opacity. On the ventrodorsal projection, there is border effacement of the heart by either fluid or soft tissue; however, on the lateral projection the cardiac silhouette is not border effaced so the surrounding opacity is likely fat, rather than fluid.

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. A—Notice the ventral fat opacity crossing the diaphragm and entering the thorax (arrows). There is also subjective cranial displacement of the stomach. B—Notice the well-marginated, linear, soft tissue opacity extending cranially toward the diaphragm (caudal-most arrow). Also notice the adjacent fat and soft tissue opacities in the caudal aspect of the right hemithorax (cranialmost arrow). Additional findings include radiographic changes to the right fifth and sixth ribs, which is consistent with the history of thoracotomy.

Citation: Journal of the American Veterinary Medical Association 252, 12; 10.2460/javma.252.12.1463

Radiographic changes to the right fifth and sixth ribs are evident, which is consistent with the history of thoracotomy. On the lateral radiographic projection, there is also subjective cranial displacement of the stomach, which may suggest microhepatica or hepatic herniation into the thorax.

Differential diagnoses for the abnormal soft tissue and fat opacities in the thorax included a diaphragmatic hernia with displaced abdominal viscera, pyothorax, or thoracic mass. Peritoneal-pericardial diaphragmatic hernia was not considered because the cardiac silhouette was not border-effaced with abdominal contents as is commonly seen with peritoneal-pericardial diaphragmatic hernia. This cat also had undergone thoracic surgery, and peritoneal-pericardial diaphragmatic hernia was not noted previously.

Computed tomography of the thorax and abdomen revealed diaphragmatic herniation of omentum and spleen into the right hemithorax via a 2.5-cm-diameter opening in the diaphragm. At the level of the diaphragm, the spleen was also focally, mildly narrowed (Figure 3). Adjacent to the splenic vein within the right caudal aspect of the pleural space was a well-defined ovoid, soft tissue-attenuating structure (measuring 1 cm in length) thought to be a splenic lymph node. The right caudal lung lobe was markedly medially compressed, and the remaining right-sided lung lobes were not identified. In the remaining pulmonary parenchyma, there was a mild, ventrally distributed interstitial pulmonary pattern. The right fourth and sixth intercostal spaces were markedly widened, and the right fifth intercostal space was narrowed. On the right second rib, there was moderate, smoothly margined, well-defined osseous proliferation. Moderate bilateral osteophyte formation associated with the femoral heads and acetabula was evident. Computed tomography also revealed the gallbladder to be positioned between the lobes of the left division of the liver. The right kidney was round and enlarged, and the left kidney was small. No fluid was noted in the pleural space.

Figure 3—
Figure 3—

Postcontrast dorsal reformatted CT image of the cat in Figure 1. Notice the extension of the spleen and omentum from the abdomen into the thorax through a diaphragmatic opening (arrow). Omentum is present in the thorax (asterisk). At the level of the diaphragm, the spleen is focally, mildly narrowed. A soft tissue window (slice thickness, 1 mm; window width, 400 Hounsfield units; window level, 40 Hounsfield units) was used to obtain the CT image.

Citation: Journal of the American Veterinary Medical Association 252, 12; 10.2460/javma.252.12.1463

Treatment and Outcome

An exploratory laparotomy with partial diaphragmatic herniorrhaphy was performed. A portion of the omentum, the spleen, and the left limb of the pancreas were found crossing the abdomen and extending through the right side of the diaphragm through an enlarged opening that was originally created during the patient's pneumonectomy and omentalization 4 years earlier. The spleen and pancreas were not firmly adhered to the thorax and were easily retracted back into the abdomen. The spleen appeared to be in good condition with a mild midbody narrowing but no obvious congestion, and the herniated portion of the pancreas had only minor edema. Some adhesions between the omentum in the thorax were broken down, and part of the omentum was retracted back into the abdomen. The diaphragmatic opening was closed tightly around the remaining omentum, and the abdomen was routinely closed. Thoracic and abdominal radiography was performed the following morning, and results confirmed proper position of the spleen in the abdomen. The patient was discharged from the hospital to the care of its owner with instructions for exercise restriction for several weeks. The patient was reportedly eating well and acting normally 4 days after surgery. On follow-up phone call with the cat's owner 4.5 months following surgery, the patient was reported to have an excellent appetite, normal behavior, and no signs of respiratory disease.

Comments

Thoracic omentalization is a technique that can be used to treat pleural effusion. It has been reported to treat idiopathic chylothorax in dogs and cats when thoracic duct ligation is not effective in relieving accumulation of pleural fluid.1,2 It has also been used to treat neoplastic pleural effusion in cats.3 The successful use of omentum in treating nonhealing wounds, abscesses, and effusions is thought to be largely the result of its large surface area for fluid absorption and its microscopic anatomy.4,5 In healthy dogs, the omentum contains phagocytes that ingest particulate matter in the peritoneum to protect the abdomen from infection and inflammation. There may also be pinocytic activity that allows for the uptake of fluid from the abdomen into the omentum.5 In the cat of the present report, the omentalization of the thorax following pneumonectomy successfully managed any pleural effusion for many years. During thoracic omentalization, an incision is made in the pars costalis of the diaphragm and omentum is pulled through the diaphragm and tacked in the thorax. The incision should be tight enough around the omentum so as not to allow herniation of other abdominal organs, but not so tight as to strangulate blood supply of the omentum.

In the cat of the present report, shifting of the omentum over time or stretch in the diaphragmatic incision allowed for abdominal contents (ie, spleen and left limb of pancreas) to slip through the hernia, resulting in compression of the remaining right caudal lung lobe, compression of the spleen, and mild edema of the herniated pancreas. We suspect these changes resulted in the patient's subsequent lethargy, anorexia, and tachypnea. Although the herniated organs were in good condition, it is reasonable to assume that strangulation of the spleen and pancreas or herniation of other organs would be possible as well. Herniation of the pancreas could also lead to pancreatitis.

Although hyperinflation of the remaining lung lobes may be expected following pneumonectomy, this was not found on CT for the cat of the present report. The normal physiologic response to removal of a large portion of lung parenchyma is to improve diffusion capacity by changes in perfusion to the remaining parenchyma, generation of new alveoli, or both. In this cat, it appeared that most of the physiologic compensation occurred via changes in blood flow and perfusion.

Diagnostic imaging was crucial to the diagnosis and treatment of this cat. Fat opacity from the thoracic omentalization was expected in thoracic radiographs, but there was a soft tissue or fluid opacity that necessitated further imaging. Computed tomography allowed for explicit visualization of the spleen herniated through the diaphragm and entering the thorax. The pancreas was not noted to be involved until direct observation during surgery.

Thoracic omentalization is an effective treatment for managing certain types of pleural effusion and was successful in treating the disease of the cat of the present report. However, it should be noted that herniation of abdominal contents through the diaphragmatic incision could be a potential long-term complication, and should be considered if a patient with a history of this procedure develops dyspnea or generalized weakness and lethargy. Thoracic and abdominal radiography and CT were crucial to the diagnosis and treatment of this cat.

Acknowledgments

The authors thank Dr. Bradley Schmidt for the radiographic images.

References

  • 1. da Silva CA, Monnet E. Long-term outcome of dogs treated surgically for idiopathic chylothorax: 11 cases (1995–2009). J Am Vet Med Assoc 2011;239:107113.

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  • 2. Lafond E, Weirich WE, Salisbury SK. Omentalization of the thorax for treatment of idiopathic chylothorax with constrictive pleuritis in a cat. J Am Anim Hosp Assoc 2002;38:7478.

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  • 3. Talavera J, Agut A, Fernandez del Palacio J, et al. Thoracic omentalization for long-term management of neoplastic pleural effusion in a cat. J Am Vet Med Assoc 2009;234:12991302.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Hosgood G. The omentum—the forgotten organ: physiology and potential surgical applications in dogs and cats. Compend Contin Educ Pract Vet 1990;12:4550.

    • Search Google Scholar
    • Export Citation
  • 5. Huyghe S, de Rooster H, Doom M, et al. The microscopic structure of the omentum in healthy dogs: the mystery unraveled. Anat Histol Embryol 2016;45:209218.

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    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen and thorax of a 9-year-old 5.1-kg (11.2—lb) neutered male domestic shorthair cat that was evaluated because of clinical signs of lethargy and anorexia of 1 week's duration and a single episode of tachypnea.

  • Figure 2—

    Same radiographic images as in Figure 1. A—Notice the ventral fat opacity crossing the diaphragm and entering the thorax (arrows). There is also subjective cranial displacement of the stomach. B—Notice the well-marginated, linear, soft tissue opacity extending cranially toward the diaphragm (caudal-most arrow). Also notice the adjacent fat and soft tissue opacities in the caudal aspect of the right hemithorax (cranialmost arrow). Additional findings include radiographic changes to the right fifth and sixth ribs, which is consistent with the history of thoracotomy.

  • Figure 3—

    Postcontrast dorsal reformatted CT image of the cat in Figure 1. Notice the extension of the spleen and omentum from the abdomen into the thorax through a diaphragmatic opening (arrow). Omentum is present in the thorax (asterisk). At the level of the diaphragm, the spleen is focally, mildly narrowed. A soft tissue window (slice thickness, 1 mm; window width, 400 Hounsfield units; window level, 40 Hounsfield units) was used to obtain the CT image.

  • 1. da Silva CA, Monnet E. Long-term outcome of dogs treated surgically for idiopathic chylothorax: 11 cases (1995–2009). J Am Vet Med Assoc 2011;239:107113.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Lafond E, Weirich WE, Salisbury SK. Omentalization of the thorax for treatment of idiopathic chylothorax with constrictive pleuritis in a cat. J Am Anim Hosp Assoc 2002;38:7478.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Talavera J, Agut A, Fernandez del Palacio J, et al. Thoracic omentalization for long-term management of neoplastic pleural effusion in a cat. J Am Vet Med Assoc 2009;234:12991302.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Hosgood G. The omentum—the forgotten organ: physiology and potential surgical applications in dogs and cats. Compend Contin Educ Pract Vet 1990;12:4550.

    • Search Google Scholar
    • Export Citation
  • 5. Huyghe S, de Rooster H, Doom M, et al. The microscopic structure of the omentum in healthy dogs: the mystery unraveled. Anat Histol Embryol 2016;45:209218.

    • Crossref
    • Search Google Scholar
    • Export Citation

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