Case reveal

Findings:

• Throughout the ventral aspect of the pleural space, a large volume of soft tissue opaque material border effaces the cardiac silhouette and cranioventral aspect of the diaphragm. This soft tissue opacity has an undulating dorsal margin. 
• In the cranioventral thorax, there are tubular gas and soft tissue opacities consistent with small intestine.

• Overlying the caudodorsal thorax, there is a large volume of gas ventral to the diaphragm.  A gas-fluid interface is identified, presumably in the stomach, that partially extends beyond the cranial margin of the diaphragm.

• In the caudal lung lobes, a homogeneous increase in soft tissue opacity decreases the conspicuity of the pulmonary vasculature.

Conclusions:

• Diaphragmatic hernia with small intestinal and likely at least partial gastric herniation. Concurrent herniation or the liver, spleen or other part of the gastrointestinal tract may also be considered.
• Mild to moderate pleural effusion (e.g. hemothorax, chylothorax, or associated with a reactive inflammatory or less likely neoplastic process).
• Caudally distributed unstructured interstitial pulmonary pattern, most likely representing atelectasis due to pulmonary hypoinflation; however, pneumonia or hemorrhage/contusion cannot be excluded.

Thoracic ultrasound:

• Small intestinal segments are identified within the right hemithorax, surrounded by a large amount of pleural effusion. The spleen was also fount in the left hemithorax adjacent to the heart. Part of the stomach was identified within the caudal thorax.

Case outcome:

• Human euthanasia was elected.

A little bit more…

• Diaphragmatic rents are rare in horses and may occur with or without herniation of abdominal viscera (Romero et al., Hart et al.). Note: A true hernia is characterized by the migrating organs being enclosed within a hernial sac. In contrast, if there is no hernial sac, the condition is referred to as a false hernia or rupture. Most congenital and all acquired diaphragmatic hernias are false hernias, therefore may be more accurately refers as a diaphragmatic rupture or diaphragmatic tear (Kelmer et al.).
• Etiologies may be traumatic (such as from racing, trailer accidents, or foaling) or congenital (Romero et al., Hart et al.).
• The interval between the traumatic event that causes the defect and its detection, often during a colic episode, is more influenced by the later migration and strangulation of the intestines through the tear than by the initial discomfort from the tear’s formation (Romero et al.).
• Clinical signs range from mild to severe signs of colic, usually with dyspnea (Romero et al., Hart et al.). Other nonspecific signs, like tachycardia, may be observed and make the diagnosis process challenging (Romero et al.). The severity of the clinical signs is not associated with survival (Hart et al.).
• The size of the tear is linked to the severity of clinical symptoms. Smaller tears tend to be more constrictive when the intestine enters the ring and are often associated with the herniation of the small intestine. In contrast, larger tears are typically linked to the herniation of larger organs, such as the large colon (Romero et al.)
• Congenital diaphragmatic hernias are identified most commonly in the left dorsal tendinous part of the diaphragm. This is theorized to be due to incomplete fusion of the pleuroperitoneal fold (Kelmer et al.). Both congenital diaphragmatic hernias are most often left-sided.

• Transthoracic ultrasonography and thoracic radiography are the preferred imaging modalities to diagnose diaphragmatic hernias. Smaller foals may also undergo CT (Romero et al.).
• Correction of the defect requires surgery using a variety of methods reported. Rents that are dorsally located are reported to carry a worse prognosis than those located ventrally. This may be due to the more limited access of rents that are dorsal, making closure difficult or impossible in some cases (Hart et al.)
• Diaphragmatic hernias carry a poor prognosis. Romero et al. reports a survival rate of 23% for all horses that presented with a diaphragmatic hernia, and a surgical success rate of 46%.

References:

• Kelmer G, Kramer J, Wilson DA. Diaphragmatic hernia: etiology, clinical presentation and diagnosis. Compendium Equine. 2008;3:28-36.
• Hart SK, Brown JA. Diaphragmatic hernia in horses: 44 cases (1986–2006). Journal of Veterinary Emergency and Critical Care. 2009 Aug;19(4):357-62.
• Romero AE, Rodgerson DH. Diaphragmatic herniation in the horse: 31 cases from 2001–2006. The Canadian Veterinary Journal. 2010 Nov;51(11):1247.