Computed tomographic-derived measurements of shunt fraction and hepatic perfusion in dogs with a single extrahepatic portosystemic shunt in a clinical setting

Use of intraoperative transsplenic injection of agitated saline to confirm temporary full attenuation of congenital extrahepatic portosystemic shunts in dogs

OBJECTIVE

To describe the use of intraoperative transsplenic injection of agitated saline (TIAS) and confirm temporarily full attenuation of extrahepatic portosystemic shunt (EHPSS) in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

A total of 40 dogs.

METHODS

Medical records of dogs that underwent surgical attenuation of EHPSS between January 2014 and May 2021 were reviewed. A ventral midline celiotomy was performed, the EHPSS identified and dissected, and temporal occlusion performed using Rummel tourniquets or silicone vascular loops. A wide range microconvex transducer was used to visualize the right atrium via a subxiphoid acoustic window. Agitated saline was injected into the splenic parenchyma while the right atrium was ultrasonographically monitored before and after temporary occlusion of the EHPSS. Case details, intra- and postoperative findings, and long-term outcome were recorded.

RESULTS

The agitated saline was immediately identified within the right atrium after injection into the splenic parenchyma before temporary occlusion of the EHPSS in all cases. After temporary occlusion, the agitated saline was not observed within the right heart, except in two dogs in which a second vessel bypassing the liver circulation was identified. No intra- or postoperative complications were recorded. Long-term clinical outcome was considered good to excellent in all cases.

CONCLUSION

Intraoperative TIAS confirmed temporary full attenuation of EHPSS.

CLINICAL SIGNIFICANCE

Intraoperative TIAS is an easy, safe and reproducible technique to assess intraoperative full occlusion of EHPSS.

Computed Tomographic Hepatic Volumetry in Dogs with Congenital Portosystemic Shunts

CTHV is a non-invasive and accurate method for assessing liver volume in dogs. CTHV has not been studied in each type of extrahepatic PSS in dogs. This study aimed to use CTHV to compare liver volumes in dogs with different types of PSSs that had been confirmed by computed tomography angiography. Dogs with PSSs were retrospectively included and categorized into IH, EHPC, EHPA, or EHPP shunt groups. Manual CTHV was performed, and the normalized liver volume (nLV) and the difference in nLV from the estimated liver volume calculated based on body weight (LV%diff) was calculated. The study included 57 dogs: 20 IH, 21 EHPC, 9 EHPA, and 7 EHPP. The median nLV (cm3/kg) and LV%diff (%) for each group were as follows: IH 17.3 (-40.4%); EHPC 16.9 (-60.3%); EHPA 15.1 (-56.7%); and EHPP 17.2 (-59.2%), respectively. There were no significant differences in nLV among the PSS types. However, LV%diff was significantly more pronounced in the EHPC and EHPA groups compared with the IH group. Additionally, smaller dogs exhibited more severe microhepatia, with a significant positive correlation between LV%diff and body weight (p < 0.01). These findings suggest that microhepatia severity varies by shunt type and is more severe in smaller dogs, highlighting the need for further research to understand the underlying mechanisms.

Enlargement of the hepatic artery is present in dogs with a congenital extrahepatic portosystemic shunt and is independent of shunt insertion into the systemic circulation

The accurate diagnosis of portovascular anomalies has been facilitated by improvements in diagnostic imaging technology. In humans, hepatic arterial blood flow changes in response to the reduction in portal blood flow. The hepatic arterial buffer response characterizes an intrinsic regulatory mechanism in response to reduced portal venous blood flow, which results in hepatic arterial enlargement. At the authors' institution, enlargement of the hepatic artery has been anecdotally observed in a population of dogs with extrahepatic portosystemic shunting, consistent with previous literature that documents variability in hepatic arterial size. In this retrospective, blinded, analytical study, a hepatic artery:aorta (Ha:Ao) ratio was assessed on CT studies from 112 dogs, with (n = 43) and without (n = 69) an extrahepatic congenital portosystemic shunt in order to compare the hepatic artery size independent of body weight between the two populations. A significant increase in the Ha:Ao ratio was documented in dogs with an extrahepatic portosystemic shunt (EHPSS) compared with those dogs with no EHPSS independent of the location of shunt insertion into the systemic circulation (P < .001). Three cases had repeat CT after surgery, and all had Ha:Ao ratio reductions following treatment. The authors propose that this may be an additional imaging feature observed in dogs with an EHPSS.

Diameter of the shunt vessel in dogs with incidental extrahepatic portosystemic shunts

Clinical signs of extrahepatic portosystemic shunts (EHPSS) depend on the amount of blood shunted. In this study, dogs with EHPSS without noticeable clinical signs including 34 left gastro-phrenic, 3 left gastro-azygos and 2 left spleno-gonadal shunts were evaluated. In dogs with EHPSS without noticeable clinical signs, the median maximum diameter of the shunt vessel was significantly smaller compared to PV (p < 0.005). Whenever the diameter of the EHPSS is small in relation to the diameter of the PV, it seems likely that no obvious clinical signs of EHPSS are observed by the owners.

Congenital portopulmonary shunt in a cat

A 9-year-old spayed female crossbreed cat with chief complaints of anorexia and hypersalivation had high serum concentrations of ammonia and fasting and postprandial total bile acid. Therefore, she was referred to our hospital. On the first evaluation, haematology, serum chemistry, radiography and ultrasonography findings suggested that she had a congenital portosystemic shunt. CT revealed a shunt vessel from the left gastric vein to the left pulmonary vein. During median celiotomy and sternotomy, gross findings and mesenteric portography revealed abnormal vessel shunting from the left gastric vein to the left pulmonary vein. Complete ligation of the shunt vessel was achieved. She recovered without any complications. Postoperative serum chemistry revealed that ammonia and total bile acid levels decreased to within the reference intervals. This report is the first to describe the clinical features and surgical outcome of a cat with a congenital portopulmonary shunt.