Hemoperitoneum as a manifestation of anaphylaxis in dogs
Josepha DeLay
Animal Health Laboratory, University of Guelph, Guelph, ON
AHL Newsletter 2022;26(1):22.
Recent literature reports have described hemoperitoneum as a significant, potentially fatal outcome of anaphylaxis in dogs. In clinical cases where anaphylaxis is considered, evaluation for presence of abdominal effusion and hemoperitoneum is warranted. Similarly, in dogs where hemoperitoneum is identified, inclusion of anaphylaxis as a differential diagnosis should be considered.
Since August 2021, hemoperitoneum has been identified in 3 dogs with possible anaphylaxis that were necropsied at the AHL. The dogs were young (1, 3, and 4 years of age), of various breeds and sex, and in good body condition. Acute collapse was reported in 2 dogs, both of which were outdoors at the time of the event. In the third dog, clinical signs included acute-onset ptyalism, pallor, diarrhea, and dyspnea. Each dog’s condition rapidly deteriorated, culminating in death or euthanasia within 30 minutes to a few hours.
Postmortem lesions were similar in each dog. Abundant free fluid blood and few variably-sized blood clots in the abdominal cavity were estimated to represent 16% to 65% of each dog’s total circulating blood volume. Prominent gall bladder edema was present in 2 of 3 dogs, and liver had a friable texture in 1 dog. There was no evidence in any of the dogs of hemorrhagic neoplastic or inflammatory abdominal mass lesions, of rupture of abdominal vasculature, or of hemorrhage at other anatomic sites. Two dogs had short, shallow capsular lacerations in spleen or liver that were unassociated with blood clots. It was suspected that these lesions resulted from resuscitation efforts or other physical manipulation, and the small size of the lesions was not considered significant to the development of severe hemoperitoneum. Toxicologic screening for anticoagulants was carried out on liver samples from 2 dogs, and no anticoagulants were detected.
Differential diagnoses for the causes of hemoperitoneum in dogs include blunt-force trauma, abdominal neoplasia (e.g., splenic hemangiosarcoma), acquired or hereditary coagulopathy, and aneurysm. Based on recent reports, anaphylaxis must also be considered as a differential diagnosis for hemoperitoneum in dogs. The clinical history provided for each dog in this series, and presence of gall bladder edema in 2 dogs, provide support for anaphylaxis in these cases. Anaphylaxis is difficult to confirm in dogs and other species, and diagnosis is often one of exclusion in the context of appropriate clinical signs and history.
The pathogenesis of hemoperitoneum associated with anaphylaxis is not well understood. The syndrome has been reported in 1 human case, in which hemorrhage was attributed to disseminated intravascular coagulation (DIC), and is not recognized in other species. In dogs, the liver and gastrointestinal tract are considered target organs for anaphylaxis. One effect of vasoactive mediators released during acute anaphylaxis is venous congestion, involving vena cava as well as other sites. As a result, gall bladder edema and hypoxic hepatic injury may develop, and these antemortem lesions may be detected ultrasonographically and by serum biochemical analysis, respectively. Increased vascular permeability and venous congestion in anaphylaxis may also act synergistically to promote hemoperitoneum. In addition, it is speculated that coagulopathy could be influenced by inflammatory mediators released by mast cells during anaphylaxis, although this mechanism is not fully elucidated. Coagulopathy resulting from insect stings has also been postulated as a cause of hemoperitoneum associated with anaphylaxis. AHL
References
1. Caldwell DJ, et al. Spontaneous hemoperitoneum and anaphylactic shock associated with Hymenoptera envenomation in a dog. J Vet Emerg Crit Care 2018;28:476-482.
2. Hnatusko AL, et al. Anaphylaxis-related hemoperitoneum in 11 dogs. J Vet Emerg Crit Care 2021;31:80-85.
3. Summers AM, et al. Spontaneous abdominal effusion in dogs with presumed anaphylaxis. J Vet Emerg Crit Care 202;31:483-489.