Have you seen this in delayed feline CE CT? Or has it seen you?

VRU 2023

Author

Obi Veterinary Education
March 25, 2026

Isabella Guarnera, Alessia Cordella, Swan Specchi, Giovanna Bertolini

Background
The feline lymphatic system is poorly documented, especially regarding large lymphatic vessels and their imaging. Traditional CT lymphangiography methods in veterinary medicine are invasive, limiting their practicality, especially in small animals like cats. During a previous study, researchers observed incidental contrast enhancement of lymphatic structures in cats during delayed CT scans. This observation led to the hypothesis that delayed, non-selective intravenous contrast-enhanced CT could consistently visualize feline lymphatic structures without targeted lymph node injections.

Methods
This was a prospective, multicentric observational descriptive study. Forty-seven cats undergoing total-body CT for various diagnostic reasons were enrolled. All cats received iohexol contrast (2 mL/kg) intravenously, followed by a 10-minute delayed full-body CT scan. Two CT systems (a 16-row MDCT and dual-source 128/192-slice scanners) were used. The scans were evaluated qualitatively for contrast enhancement in the hepatic and mesenteric lymphatic vessels, cisterna chyli, thoracic duct, and the anastomosis of the thoracic duct with the systemic venous system.

Results
In the delayed CT scans, the cisterna chyli was most frequently enhanced (91%), followed by the thoracic duct (83%), mesenteric lymphatic vessels (83%), hepatic lymphatic vessels (81%), and the thoracic duct termination (66%). Visualization was better with higher-slice dual-source CT scanners. For example, hepatic lymphatic vessel enhancement was seen in 92% of cats scanned with dual-source systems compared to 40% with the 16-row MDCT. Similar trends were noted for other structures, likely due to thinner slice reconstruction and superior image quality in advanced scanners.

Limitations
The study did not control for patient comorbidities (e.g., renal or intestinal disease) that could influence contrast dynamics. Only a single delayed scan at 10 minutes post-injection was performed, limiting understanding of the optimal timing for lymphatic visualization. Differences in imaging hardware and protocols between centers could have influenced detectability. The small number of cats scanned with the 16-row MDCT also limits direct comparison between scanner types.

Conclusions
Delayed contrast-enhanced CT without selective lymph node contrast injection can visualize major lymphatic structures in cats. This non-invasive method could serve as a simpler alternative to traditional CT lymphangiography, offering potential applications in clinical diagnostics and surgical planning, especially in conditions like chylothorax. Further research is needed to refine the technique, assess its clinical utility, and determine optimal imaging timing.

F I G U R E 1 Sagittal reconstruction from delayed post-contrast intravenous series showing diffuse enhancement of the lymphatic system in two feline patients (A, B). A, Images acquired with 16-row MDCT unit (Siemens Emotion 16) (Slice thickness 1,5 mm; WW 402; WL 109). 1- thoracic duct; 2- hepatic lymph vessels; 3- celiac trunk; 4- cisterna chyli; 5- mesenteric lymph vessels. B, Images acquired with Dual-source CT 192 × 2(Siemens Somatom Force) volume rendered (Slice thickness 0,6 mm; WW 300; WL 40). 1- thoracic duct; 2- celiac trunk; 3- mesenteric trunk; 4-cisterna chyli; 5- lumbar trunks.

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