CT features of cutaneous and subcutaneous canine mast cell tumors and utility of conventional and indirect lymphography to detect clinically unknown mast cell tumors and to map the sentinel lymph nodes.

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.

CT features of divisional bile ducts in healthy Labrador Retrievers.

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%) .

Comparison of sonographic and CT findings for the identification of renal nodules in dogs and cats.

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).

Computed tomographic-lymphography as a complementary technique for lymph node staging in dogs with malignant tumors of various sites.

Locoregional lymph nodes are routinely examined in order to define the spatial extent of neoplastic disease. As draining patterns of certain tumor types can be divergent from expected anatomical distribution, it is critical to sample the lymph nodes truly representing the draining area. The aim of this bicenter prospective pilot study was to describe the technique of computed tomographic (CT)-lymphography for primary draining lymph node mapping in tumor staging in dogs. Forty-five dogs with macro- or microscopic tumors in specified localizations were evaluated. Depending on body weight, 0.8-2 ml contrast agent (iohexol) was injected into four quadrants around the tumor, and CT-images were obtained at 1, 3, 6, 9, and 12 minutes post-injection. Attenuation of chosen regions of interest (Hounsfield units (HU)) and patterns of enhancement were assessed for 284 lymph nodes in the precontrast study with median HUs of 31.1 (Interquartile range (IQR) = 18.4) and for 275 in the intravenous postcontrast study with 104.3 HU (IQR = 31.2) (paired Wilcoxon test, P < 0.001). In the CT-lymphography study, 45 primary draining lymph nodes with a significantly higher median HU value of 348.5 (IQR = 591.4) (one-sample t-test, P < 0.001) were identified. Primary draining lymph nodes were found to be clearly visible after 1-3 minutes after local injection, often concurrent with a good visibility of the lymphatic vessel system. The herein described technique of peritumorally injected CT-contrast agent followed by subsequent CT-lymphography for primary draining lymph node mapping works well in a majority of cases in all investigated sites and warrants further validation for different tumor entities.

COMPUTED TOMOGRAPHIC FEATURES OF PHARYNGEAL NEOPLASIA IN 25 DOGS.

Computed tomography (CT) is commonly used to investigate head tumors in dogs, however little information is available for lesions of the pharyngeal area. The purpose of this multicentric, retrospective, cross-sectional study was to describe the CT findings in a sample of dogs with pathologically confirmed pharyngeal neoplasia and determine whether any CT features allowed differentiation of tumor type. Location of lesions, size and shape, margins, relationship with surrounding structures and vessels, attenuation characteristics and enhancement pattern, regional lymph node changes, and presence of metastasis were recorded by three observers (1 DECVDI). The effect of final diagnosis on each CT feature was tested. A total of 25 dogs were included: 15 with carcinomas, five sarcomas, four melanomas, and one lymphoma. The oropharynx and laryngopharynx were more frequently involved. Among tumor groups, lesions were of similar size, irregularly shaped, had ill-defined margins, and had moderate-to-marked heterogeneous contrast enhancement. Lysis of hyoid bones was recorded in two carcinomas and infiltration of the lingual artery occurred in one case. Marked medial retropharyngeal lymphoadenomegaly was recorded in 11 of 14 carcinomas, in all sarcomas and in two of four melanomas. The single lymphoma case showed ill-defined thickening of the oropharyngeal and laryngeal wall with retropharyngeal and mandibular lymphadenomegaly. Lung metastases were found in two of five sarcomas and two of four melanomas. Findings from the current study did not support the hypothesis that CT features could be used to predict pharyngeal tumor type in dogs. However, CT was helpful for determining mass extension, lymph node involvement, and distant metastatic spread.