Juhyang Park 1 2, Daji Noh 3, Sang-Kwon Lee 1, Kija Lee 1

Background
Anomalous venous drainage involving the left hepatic vein (LHV) into the coronary sinus is extremely rare in humans and had not been reported in veterinary patients until this case. The report presents a Selkirk Rex cat with recurrent lower urinary signs, diagnosed with a portosystemic shunt (PSS) and a novel vascular anomaly involving the LHV. The anomaly is hypothesized to result from a shared embryologic disruption in venous development.

Methods
A 16-month-old male Selkirk Rex cat with hematuria, dysuria, and oliguria underwent radiography, abdominal ultrasound, and computed tomographic angiography (CTA) using a 16-multidetector CT scanner and 3D reconstructions. Intraoperative observations were made during portosystemic shunt banding and cystostomy. Histopathology and stone analysis were also conducted.

Results
CTA revealed an anomalous vessel from the LHV bypassing the caudal vena cava (CVC) to drain into a mildly dilated coronary sinus, which in turn connected to the right atrium. An extrahepatic splenocaval shunt and multiple urinary calculi were identified. The LHV passed through the diaphragm via a separate defect from the caval foramen. Surgery confirmed the vascular anomaly. Histopathology showed hepatic lobular atrophy with portal vein hypoplasia; the bladder stone was composed of ammonium urate. Ten-month follow-up showed no progression of vascular anomalies, though cystitis persisted mildly.

Limitations
Limitations include the absence of macroscopic documentation of the LHV-coronary sinus connection and the inability to confirm the vessel entry into the sinus via echocardiography. Transesophageal echocardiography was not performed, potentially missing subtle findings.

Conclusions
This is the first documented case in veterinary medicine of an anomalous connection between the LHV and the coronary sinus. Although typically asymptomatic, such anomalies may be relevant for surgical planning. CTA is the diagnostic gold standard. The concurrent portosystemic shunt and vascular anomaly suggest a shared embryological origin. Radiologists should screen for such anomalies in patients with congenital cardiovascular malformations.

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