Spontaneous Abdominal Effusion Associated with Presumed Anaphylaxis in Dogs

Anaphylaxis is a type I hypersensitivity reaction that can involve multiple organ systems. Commonly reported causes of anaphylaxis include drugs, insect stings, and blood products.¹ In dogs, the liver and GI tract are primarily impacted, and signs include vomiting, diarrhea with hematochezia, and hepatic congestion leading to portal hypertension and pooling of visceral blood that can rapidly progress to hypovolemic shock with cardiovascular collapse and death. 

In humans, standard treatment involves administration of epinephrine and supportive care (eg, IV fluid therapy), regardless of the trigger.² 

Peer-reviewed veterinary studies on anaphylaxis are limited, but there have been reports of dogs with ultrasound evidence of gallbladder wall changes, portal vein hypertension, and hepatic portal vein hypertension.^3-5 Reports of spontaneous abdominal effusion, including hemoperitoneum, have also been published.^6,7 

This retrospective study described the clinical signs and characteristics of 16 dogs with spontaneous abdominal effusion associated with presumptive diagnosis of anaphylaxis. Three dogs had no effusion on presentation but developed spontaneous effusion within 3 hours of IV fluid resuscitation. Hemorrhagic effusion was described in 8 dogs that underwent abdominocentesis. The most common clinical signs were altered mentation, vomiting, diarrhea, tachycardia, hypothermia, and hypotension. Common diagnostic findings included lactic acidosis, elevated ALT and gamma-glutamyl transferase, and gallbladder wall edema and thickening.

This study highlights the importance of anaphylaxis as a differential diagnosis in dogs with spontaneous hemoperitoneum, as anaphylaxis can be treated with medical management, whereas common interventions for hemoperitoneum include exploratory surgery or humane euthanasia.

Key pearls to put into practice:

Gallbladder wall edema (ie, halo sign) on abdominal ultrasound is not pathognomonic for anaphylaxis but may be one of many clinical findings in dogs with a history suggestive of presumptive anaphylaxis.

Anaphylaxis is an important differential diagnosis in dogs with spontaneous hemoperitoneum. If presumptive anaphylaxis is diagnosed, it is important to carefully evaluate patient history, examine for insect stingers or other clinical signs of allergic reaction, and provide treatment with epinephrine.

Patients with allergic reactions should have serial point-of-care abdominal ultrasonography performed to screen for spontaneous abdominal effusion, as this may indicate ongoing severe clinical signs.