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Computed tomography is frequently used to stage canine mast cell tumors (MCTs). The aims of this prospective, observational study were to describe the CT features of MCTs, to evaluate the performance of CT in detecting additional or incidental MCTs, to distinguish between cutaneous (cMCT) or subcutaneous (scMCT) MCTs, and to identify one or multiple sentinel lymph nodes (SLNs) by indirect CT lymphography (ICTL). Seventy‐two dogs affected by 111 MCTs were included. The recorded parameters were: shape, size, attenuation (Hounsfield units [HU]), location (cutaneous or subcutaneous), and presence of fat stranding. The SLNs were compared with the regional lymph nodes and supplementary MCTs were registered. Mast cell tumors mostly appeared with well‐defined margins (89%), round/oval shape (71%), homogeneous enhancement (90%) with a mean postcontrast density of 62.0 ± 23.4 HU and associated with fat stranding (43%). Cutaneous mast cell tumors were more frequently round (P =.003), whereas scMCTs were oval (P =.011) with a larger mean maximal diameter (2.91 ± 1.57 cm vs 1.46 ± 1.28 cm, P =.002) and more feeding vessels (77% vs 39% P =.044). Compared with histopathology, CT accuracy in differentiating cMCTs and sMCTs was 57%, with an interobserver agreement of 88% (three reviewers). Indirect CT lymphography showed the SLN in 82 of 85 (97%) cases, 32% of them not corresponding to the regional node. CT showed additional or incidental MCTs in 23 of 72 (32%) dogs. In conclusion, the common CT appearance of canine cMCTs and scMCTs is reported with some statistical differences between the two categories. CT is useful in identifying clinically undetected MCTs and SLNs, although it shows low accuracy in distinguishing between cMCT and scMCT. [ABSTRACT FROM AUTHOR]

Computed tomography (CT) is increasingly being used for the study of gallbladder and bile duct diseases. The first step in interpreting CT findings is understanding the cross‐sectional anatomy of the structures involved, but there are no published studies describing the CT features of the divisional bile ducts. In dogs, anatomic studies report two common patterns including three or four divisional bile ducts. The aim of this retrospective, descriptive, anatomical study was to describe the size and pattern of the visible divisional bile ducts, based on their location and extension, using contrast‐enhanced CT in a group of Labrador Retrievers without evidence of hepatobiliary diseases. The correlation between the biliary duct number and dimensions, and the visceral fat area percentage (VFA%) was also evaluated. The right lateral divisional duct (RLD) was visualized in four of 40 dogs, the left lateral divisional duct (LLD) in nine of 40 dogs, and in 17 of 40 dogs, both were simultaneously visualized. In 10 of 40 dogs, the RLD and LLD were not highlighted. When visible, the RLD has a median diameter of 0.23 cm and a median length of 0.82 cm. The LLD has a median diameter of 0.23 cm and a median length of 2.72 cm. The median diameter of the common bile duct before and after the insertion of divisional bile ducts was 0.23 and 0.25 cm, respectively. No correlation with the VFA% was found. At least one of the divisional bile ducts could be visualized using contrast‐enhanced CT in the majority of sampled dogs (75%). [ABSTRACT FROM AUTHOR]

Ultrasonography (US) and computed tomography (CT) are used to diagnose neoplastic and non‐neoplastic focal renal lesions in dogs and cats; however, comparative studies between these two diagnostic tools are lacking. The aim of this retrospective, methods comparison study was to evaluate and compare the performance of US compared to CT in identifying at least one renal nodule in animals with confirmed focal renal lesions. Imaging studies of animals with uni‐ or bilateral renal nodules smaller than 3 cm that underwent both US and CT and that had a pathologically confirmed diagnosis were reviewed. Animals with renal cysts and infarcts were excluded. Recorded features for both modalities included the following: shape, size, number, localization, margins, renal profile. For CT only, recorded features also included attenuation (HU) and pattern of enhancement. For US only, recorded features also included echogenicity, echostructure, and rate of visibility. Final diagnosis was obtained by cytology or histopathology. Using CT, lesions were identified in all 39 (100%) kidneys of 18 dogs and seven cats. Most lesions were multiple, cortical, well‐defined, iso‐attenuating (precontrast), hypo‐attenuating, and moderately enhancing (postcontrast). Using US, lesions were identified in 29 of 39 (74%) kidneys. Overall, nine (31%) lesions were poorly visible; 10 (26%) kidneys appeared normal; in 17 (59%) organs, lesions' number was underestimated. Isoechoic, non‐protruding lesions were difficult to identify by US. Ultrasonography underestimated renal lesions compared to CT in 59% of the kidneys (P = 0.001). Final diagnoses included metastatic disease (n = 16), infiltration by feline lymphoma (n = 4), primary neoplasia (n = 3), and non‐neoplastic benign lesions (n = 2). [ABSTRACT FROM AUTHOR]

OBJECTIVE: The aim of this study was to evaluate the CT features of pulmonary metastases in dogs with hemangiosarcoma (HSA) at various sites. Additionally, the CT characteristics of extrapulmonary metastases in the same population were assessed. METHODS: Retrospective, observational, and descriptive study conducted from April 2013 to January 2024. Dogs with histologically confirmed HSA and suspected or cytologically/histologically confirmed lung metastases were included. Dogs were excluded if they had a second primary tumor or only 1 unsampled pulmonary nodule. RESULTS: 33 dogs were included, with 26/33 [78.8%] having more than 10 metastatic pulmonary nodules. Most nodules were generalized (24/33 [72.7%]), miliary (29/33 [87.9%]) to subcentimetric (32/33 [97%]) in size, well-defined margins (29/33 [87.9%]), or a perilesional halo sign (24/33 [72.7%]). When more than 10 nodules were present, a generalized distribution was prevalent, while a peripheral location was more common when 2 to 10 nodules were present (P < .0001). In 32/33 (97%) cases, a pulmonary vessel was directly connected to the nodule (feeding vessel). After contrast administration, most lung metastases appeared homogenous (26/33 [78.8%]), although some showed areas of intense enhancement (5/33 [15.1%]) a feature also observed in extrapulmonary metastases with varying frequency (0% to 85.7%). CONCLUSIONS: Pulmonary HSA metastases were characterized by generalized, small (miliary/subcentimetric), well-defined nodules, commonly associated with a halo sign and feeding vessel. Intralesional areas of spotty postcontrast linear or amorphous strong hyperdensity were frequently observed especially in extrapulmonary metastases. CLINICAL RELEVANCE: These features may help radiologists and clinicians orient their diagnosis toward metastatic HSA. [ABSTRACT FROM AUTHOR]