Ultrasonographic findings of gastrointestinal histoplasmosis in dogs

Abstract

Histoplasmosis, a mycotic infection caused by Histoplasma spp, can infect the gastrointestinal tract of dogs. Clinical signs of gastrointestinal histoplasmosis can include diarrhea, profound weight loss, anorexia, and vomiting. Rectal scrape for cytology can provide a quick diagnosis, but if negative abdominal ultrasound is often pursued. Ultrasonographic abnormalities in dogs with gastrointestinal histoplasmosis have rarely been reported. This retrospective, single-center case series aimed to describe the ultrasonographic features of gastrointestinal histoplasmosis in dogs. Nineteen cases with a diagnosis of gastrointestinal histoplasmosis confirmed with gastrointestinal cytology or histopathology (N = 15) or gastrointestinal lymph node cytology (N = 4) that had undergone an abdominal ultrasound examination from 2005 to 2020 were included. Ultrasound images were reviewed by an American College of Veterinary Radiology (ACVR)-certified veterinary radiologist and diagnostic imaging resident. Eighteen cases had sonographic abnormalities within the gastrointestinal tract. The colon was the most affected organ. Colonic thickening and abnormal wall layering were the most frequent findings (N = 16 dogs); thickening ranged from 0.36 to 1.2 cm. Diffuse, multifocal, and focal thickening patterns were seen. Sixteen patients had abnormal wall layering of the colon (complete loss of layering or altered with partial loss of layering). Other frequent findings included lymphadenopathy, small intestinal thickening with abnormal wall layering and peritoneal effusion. Based on the authors' review of the literature, this is the first description of ultrasonographic findings of gastrointestinal histoplasmosis in a group of dogs. Although abnormal gastrointestinal wall layering seen sonographically is most frequently associated with neoplasia, this is not pathognomonic. Gastrointestinal histoplasmosis should be considered as a differential diagnosis due to the similarities and overlap of ultrasonographic features.

Evaluation of serum 25‐hydroxyvitamin D, C‐reactive protein, and haptoglobin as biomarkers in dogs newly diagnosed with histoplasmosis

“…Interestingly, this hypothesis was not supported in our cohort, because serum 25(OH)D concentrations were no different in dogs with and without GI tract involvement. However, the majority of dogs in our study had disease confirmed or suspected in the large intestine with less suspicion of small intestinal disease, a distribution commonly seen in dogs with GI histoplasmosis 1,8 . In addition, the small number of dogs included in this comparison could have affected the identification of a significant difference if such a difference was present.…”

“…However, the majority of dogs in our study had disease confirmed or suspected in the large intestine with less suspicion of small intestinal disease, a distribution commonly seen in dogs with GI histoplasmosis. 1 , 8 In addition, the small number of dogs included in this comparison could have affected the identification of a significant difference if such a difference was present. Also, GI tract involvement could not be definitively confirmed or excluded in dogs without cytological or histopathological samples acquired from the small and large intestine.…”

“…Clinical disease in dogs can be limited to the lungs, or disseminate via blood and lymphatics to a wide array of extra‐pulmonary sites. 2 , 4 , 5 , 6 , 7 , 8 , 9 , 10 …”

“…After inhalation, microconidia convert to the yeast form in the terminal bronchioles of the lungs. Clinical disease in dogs can be limited to the lungs, or disseminate via blood and lymphatics to a wide array of extra‐pulmonary sites 2,4‐10 …”

“…Clinical disease in dogs can be limited to the lungs, or disseminate via blood and lymphatics to a wide array of extra-pulmonary sites. 2,[4][5][6][7][8][9][10] Vitamin D plays an integral role in the innate immune response against infections. Calcitriol, the active metabolite of vitamin D, enhances leukocyte phagocytizing and killing capacity, increases antimicrobial peptide production, dampens exuberant proinflammatory responses, and sequesters iron from pathogens.…”