Presumed mediastinal cysts have a low prevalence in canine thoracic computed tomographic studies.

Mediastinal cysts (MCs) are rare lesions that can arise from embryonic remnants of various mediastinal structures. MCs usually are incidental findings in dogs and cats; however, they can reach a mass-like appearance. The description of MCs on CT in dogs is limited. This retrospective, single-center, descriptive, prevalence study aimed to determine the prevalence of presumed mediastinal cysts (PMCs) in dogs and assess their CT characteristics. Dogs that underwent a thoracic CT scan from January 2019 to August 2021 were included. CT images were evaluated for the presence of PMCs by two diagnostic imaging interns, two last year diagnostic imaging residents, and a board-certified veterinary radiologist. Number, location, margins, shape, volume, size, mass effect, and attenuation values of PMCs were assessed. A total of 866 CT scans were reviewed, and 49 PMCs were identified. The prevalence of PMCs in dogs was 5.66%. English Bulldog and mixed-breed dogs were subjectively overrepresented; however, the possibility of population bias could not be excluded. PMCs were subjectively more frequently observed in male dogs. The PMCs were predominantly round, small, solitary fluid-filled findings localized in the cranioventral mediastinum, with well-defined margins, homogeneous attenuation, and no contrast enhancement. The median attenuation value was 6.32 HU (range: -20.16 to 23.45 HU) precontrast and 7.58 HU (range: -2.45 to 20.79 HU) postcontrast, and the median volume was 1.19 cm3 (range: 0.02-45.32 cm3). Although the prevalence of PMCs was low in our sample population, findings supported prioritizing a differential diagnosis of incidental PMC for dogs with the above imaging characteristics.

Anatomical classification of feline congenital extrahepatic portosystemic shunts based on CT angiography: A SVSTS and VIRIES multi-institutional study in 231 cats.

The prevalence of anatomical-based subtypes of feline congenital extrahepatic portosystemic shunts (EHPSS) has not been completely elucidated. The goal of this study was to use CT angiography to create an anatomical-based nomenclature system for feline congenital EHPSS. Additionally, subjective portal perfusion scores were generated to determine if intrinsic portal vein development was associated with different shunt conformations or patient age at the time of CT. The SVSTS and VIRIES list services were used to recruit cases. Data collected included patient DOB, gender, breed, weight, CT date, and reported diagnosis. Shunts were classified based upon (1) the shunt portal vessel(s) of origin, (2) the shunt systemic vessel(s) of insertion, and (3) any substantial portal vessels contributing to the shunt. Additionally, hepatic portal perfusion was subjectively scored between 1 (poor/none) and 5 (good/normal) based on the caliber of the intrahepatic PVs. A total of 264 CT scans were submitted from 29 institutions. Due to exclusion criteria, 33 (13%) were removed, leaving 231 CT scans to be included. Twenty-five different EHPSS anatomies were identified with five classifications accounting for 78% of all shunts (LGP [53%], LGC-post [11%], LCG [7%], LGC-pre [4%], and PC [4%]). Shunt origin involved the left gastric vein in 75% of the described classifications. Significant differences were identified among the five most common shunt types with respect to age at the time of CT scan (P = .002), breed (P < .001), and subjective portal perfusion score (P < .001). This refined anatomical classification system for feline EHPSS may enable improved understanding, treatment comparisons, and outcome prediction for cats with these anomalies.

Delayed non-selective contrast-enhanced CT can reveal spontaneous contrast enhancement of the lymphatic system in cats.

The authors incidentally observed that, on delayed postcontrast CT studies, feline patients could show increased attenuation of the lymphatic system. The aim of the present study was to evaluate if the lymphatic system of feline patients undergoing intravenous administration of contrast medium might consistently enhance on delayed postcontrast CT studies. Feline patients that underwent CT examination for variable diagnostic purposes were included in this multicentric observational descriptive study. A 10-min delayed postcontrast whole-body CT series was obtained for all cats enrolled and the following anatomic structures were systematically assessed: mesenteric lymphatic vessels, hepatic lymphatic vessels, cisterna chyli, thoracic duct, and anastomosis of the thoracic duct with the systemic venous system. A total of 47 cats were included in the study. The mesenteric lymphatic vessels showed enhancement in the selected series in 39 of 47 (83%) patients and the hepatic lymphatic vessels in 38 of 47 (81%) patients. The cisterna chyli, thoracic duct, and the point of anastomosis of the thoracic duct with the systemic venous circulation were enhanced in 43 (91%), 39 (83%), and 31 of 47 (66%) cats, respectively. This study confirms the initial observation. The mesenteric and hepatic lymphatic system, the cisterna chyli, the thoracic duct, and its anastomosis with the systemic venous circulation of feline patients undergoing intravenous administration of iodinated contrast medium can show spontaneous contrast enhancement in non-selective 10-min delayed contrast-enhanced CT series.