Gallbladder hematoma presenting as a mucocele in a dog

Dominique Comeau

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2024;28(2):30.

The gallbladder and a liver biopsy from a 6-year-old male neutered Brussels Griffin dog were submitted to the Animal Health Laboratory following a history of vomiting.  On ultrasound examination, abundant hyperdense material had been noted in the gallbladder, which raised concern for gallbladder mucocele.  A cholecystectomy was performed.  The submitted gallbladder was enlarged and the capsule over the surface appeared intact.  On the cut section, the tissue was divided into two structures with a large, round structure filled with dark red blood compressing the gallbladder into a thin crescent-shaped rim around one side (Fig. 1).  This appearance was confirmed histologically where the tissue formed two “lumina” divided by a discontinuous fibrous septa, but surrounded by a continuous fibrous capsule.  The first lumen was lined by gallbladder mucosa with occasional ectatic glandular structures, and was filled with abundant bile mixed with a small amount of hemorrhage.  Along one side, the gallbladder wall underwent transmural necrosis with marked attenuation of the epithelium which gave way to complete loss of the wall (Fig. 2).  This focal area of disruption was surrounded by hemorrhage and abundant fibrin.  The rupture communicated with an enclosed space contained within the same fibrous capsule which was unlined by any epithelium, and contained abundant hemorrhage and clumps of fibrin with rare neutrophils.  There was a small amount of liver parenchymal tissue along the far border of the fibrous wall, at the edge of the section opposite to the viable gallbladder tissue.

This lesion was diagnosed as a mural hematoma of the gallbladder.  There were also changes consistent with early mucocele formation in the compressed gallbladder.  The granulation tissue surrounding the hematoma indicated a degree of chronicity, and may explain why the hematoma was not evident externally during surgery or trimming, as it was well-contained by fibrous tissue which blended with the gallbladder capsule.

Gallbladder hematomas are rarely reported in humans, and a single case report of spontaneous gallbladder mural hematoma in a dog was found in the literature.  In that case as well as in ours, the clinical presentation was indistinguishable from a gallbladder mucocele.  Possible causes of gallbladder hematomas identified in human cases include blunt force trauma to the abdomen, underlying coagulopathy, cholelithiasis, and gallbladder neoplasia.  In this case and the other reported canine case, no cause was identified. A swab from the tissue was submitted for bacterial culture and no bacteria were isolated.  Surgical removal was uncomplicated, and the dog recovered well from surgery.   AHL

Figure 1. Cross section of the gallbladder at the time of trimming. The compressed gallbladder lumen is forming a crescent on the left side of the image, and the hematoma forms the majority of the tissue on the right. The white arrows indicate the fibrous septa separating these structures.

Figure 2. Histologic cross section of the gallbladder with the same orientation as figure 1. The hematoma is on the right with abundant blood in the lumen. The gallbladder forms a compressed, crescent structure on the left, with an incomplete fibrous septa between them (indicated by the arrows). The inset shows the gallbladder mucosa on the left and the unlined fibrous wall of the hematoma on the right. H&E

References

1. Jerrems O, et al. Spontaneous mural gallbladder hematoma in a dog. Can Vet J  2020;61(1):35-28.

2. Jung YM, et al. Intramural gallbladder hematoma mimicking gallbladder neoplasm in a 55-year-old male patient. J Korean Surg Soc 2011;81(3):216-220.