Diaphragmatic Hernia in Dogs and Cats: Diagnosis, Imaging Strategies, and the Impact of AI

Diaphragmatic Hernias in Dogs and Cats: Diagnosis, Imaging Strategies, and the Impact of AI

A diaphragmatic hernia occurs when abdominal viscera protrude through a defect in the diaphragm into the thoracic cavity. In small animals, these defects are categorized as either congenital or acquired, with traumatic ruptures, often secondary to blunt force, comprising the majority of clinical cases.

While many diaphragmatic hernias represent an acute, life-threatening compromise to cardiopulmonary stability, others may remain clinically silent for years. However, the potential for sudden incarceration of organs or the development of pleural effusion means that even incidental findings necessitate careful monitoring and strategic surgical planning. Timely recognition remains paramount to preventing a transition from a stable state to one of acute respiratory failure or obstructive shock.

Diagnosing a diaphragmatic hernia can often be straightforward, when obvious displacement of gas-filled bowel is noted within the thoracic cavity. That being said, when only small amounts of abdominal viscera are displaced or concurrent disease is present, the diagnosis becomes more challenging. Particularly in complicated presentations, AI-assisted tools provide a critical “second set of eyes”, enhancing detection and contributing to accurate, early diagnosis.

Types of Diaphragmatic Hernias

While the mechanical failure of the diaphragm is the common denominator, the clinical presentation and surgical implications vary significantly based on the etiology.

1. Traumatic Diaphragmatic Hernias

The most prevalent form encountered in emergency medicine. Traumatic diaphragmatic hernias typically result from an acute increase in intra-abdominal pressure while the glottis is open, leading to a pleuroperitoneal pressure gradient that ruptures the diaphragm at its weakest points.

• Location: Tears most frequently occur in the costal muscles or at the musculotendinous junction.
• Visceral Involvement: The liver is the most common herniated organ (often leading to concurrent pleural effusion via venous congestion), followed by the small intestines, stomach, and spleen.
• The space occupying nature of the abdominal viscera in the thoracic cavity can lead to cardiovascular compromise, particularly if a large organ like a gas-dilated stomach is displaced.

2. Congenital Diaphragmatic Hernias

Congenital hernias are developmental anomalies often diagnosed during unrelated diagnostic workups.

• Peritoneopericardial Diaphragmatic Hernia (PPDH): The most common congenital defect, resulting from a failure of the septum transversum to fuse. Unlike traumatic cases, abdominal viscera communicate directly with the pericardial sac rather than the pleural space.
• Hiatal Hernias: Though less common, these involve the protrusion of the esophagus or stomach through the esophageal hiatus and are often associated with dynamic respiratory issues or regurgitation.

Clinical Signs: When to Suspect a Hernia

The signs of a diaphragmatic hernia can vary significantly depending on the organs involved, the volume of herniated contents, and whether the presentation is acute or chronic. Respiratory compromise is the most common presentation, but gastrointestinal or systemic signs may also occur.

Imaging: Radiography as a First-Line Tool

Radiographs are the first line diagnostic when a diaphragmatic hernia is suspected. Familiarity with anatomy and well-positioned, collimated radiographs are critical for accurate interpretation. While the radiographic findings vary by hernia type, some common findings are listed below.

AI-Assisted Detection: A Second Set of Eyes

SignalPET’s AI technology has proven valuable in improving the accuracy and speed of radiographic interpretation, especially in subtle or easily missed conditions like diaphragmatic hernias.

AI is a reliable support tool to help clinicians differentiate between pulmonary pathology and actual herniation, even when clinical signs are ambiguous.

SignalPET in Action: Case Examples

Case 1: Acute Dyspnea Post-Trauma (Dog)

• Presentation: Respiratory distress after being hit by a car.
• Radiograph: Suspected lung contusion.

The left diaphragmatic crus is displaced dorsally with shifting of the cardiac silhouette to the right. The stomach and a portion of the liver are cranially displaced with the diaphragm. 

AI Flag: Diaphragmatic Hernia.

Case 2: The cat suddenly collapsed.

• Presenting Complaint: Pet parents report that the kitten tires easily and is not as playful as littermates.
• Notable on physical examination: Muffled Heart Sounds
• Radiographs at first glance: The cardiac silhouette has a globoid shape and is moderately enlarged.

There are angular soft tissue opaque structures associated with the cardiac silhouette. The cardiac silhouette is globoid and enlarged. On both projections the cardiac apex contacts the diaphragm with border effacement. There is less liver than expected within the abdominal cavity with mild cranial displacement of the gastric axis. 

AI Flag: SignalPET Flagged suspicion of a diaphragmatic hernia on the study.

Treatment and Prognosis

The definitive treatment for most diaphragmatic hernia is surgical repair via midline celiotomy. Severe trauma complicates repair as stabilization is needed prior to surgery. Ultimately a large number of individual factors, including the chronicity of the hernia, need to be taken into account when managing these cases.

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