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Diagnosing a Shunt on Sonogram

Patient Information

8 Years
Female, Spayed


A tidbit exemplary drawing from the upcoming textbook Clinical Approach to Sonographic Pathology still in editing….yes we are still toiling away on this epic textbook… what was i thinking? Figure; Vazquez & Lindquist.
Strongly shadowing renal calculus in a young dog should alert the potential for ammonium biurate stones and potential liver shunt. This is positive predictive factor 2 for shunt presence. See our abstract in sonopath resources tab. ( ECVIM, Tolousse, France. Sept 8-11, 2010. Sonographic Whole Body Parameters of Portosystemic Shunts in 38 Dogs & Cats.
Overwhelming GB compared to the subnormal hepatic parenchyma seen in this long axis view of the liver with microhepatica with coarse architecture. PPF 3 for shunt presence.
Azygos portion of the spleno-azygos shunt dorsal to the CVC in the near field.

Where the heck is the azygos vein and what shunt goes there? You can diagnose a shunt on a sonogram. Sure, with practice and the right technique you can and we love to do it here in the SonoPath's geeky fun for us with tons of U/S shunt examples in our clinical search engine ( and more are in past cases of the month in the resources tab (

Also see our abstract on the subject in sonopath resources: ( ECVIM, Tolousse, France. Sept 8-11, 2010. Sonographic Whole Body Parameters of Portosystemic Shunts in 38 Dogs & Cats.

Well, the splenoazygos shunt, as we display here, can be found in Florida under the U/S probe of Seth Mitchell, DVM of Mobile Veterinary Imaging of SE Florida. ( Then what do we do with the shunt? Is the shunt surgical? Is it medical? We have criteria to tell the difference and Seth's case is doing well on medical treatment alone after collaborating with SonoPath to ensure this challenging scenario. Come see how it shakes out in the December 2013 SonoPath case of the month (



An 8-year-old FS Maltese was presented for evaluation for severely elevated pre and post-prandial bile acids and mild ALT elevations and subnormal BUN. In addition, the patient was positive for Rocky Mountain spotted fever. Seizure activity was present in the history.

Clinical Differential Diagnosis

Porto-caval shunt, primary portal vein hypoplasia, hepatic fibrosis, liver cirrhosis. Primary CNS disease: inflammatory/infectious, neoplasia, GME.

Image Interpretation

The urinary bladder presented a small concretion that measured 0.5 cm and was non-shadowing. The kidneys presented a significant amount of pelvic mineralization that was non obstructive. The left kidney measured 3.6 cm. Calculus was noted in the left kidney pelvis and measured 1.16 cm. The right kidney measured 4.24 cm with pelvic calculus that measured 1.49 cm. The liver was subnormal in size with coarse architecture and increased portal markings. The vena cava measured 0.74 cm, aorta 0.62 cm. The portal vein was subnormal in size and measured 0.29 cm. An extrahepatic, portosystemic shunt was noted. This was deriving from the splenic vein entrance into the portal vein. This was tortuous and measured approximately 0.5 cm in width and traveled dorsally and entered into the aortic hiatus. This created a splenoazygos shunt and a "double aorta" was formed. Concurrent hepatic disease is likely given the increased portal markings and remodeling.

Sonographic Differential Diagnosis

Spleno-azygos shunt with concurrent chronic inflammatory hepatopathy. Small right calculi were noted in the bladder measuring 0.1 and 0.2 cm each.


Spleno-azygos shunt with chronic inflammatory hepatopathy.


The patient is currently stable on medical management alone and no further seizure activity or other clinical signs have been noted.


    Given the low BUN in this patient there was concern about emerging liver failure especially given the patient's age. It was debatable whether surgical intervention with ameroid constrictor would be the optimal approach as the liver may not have been able to handle the new volume owing to chronic disease and potential for concurrent portal vein hypoplasia. Cystotomy would also be recommended at the time of surgery. Dietary management with Royal Canin hepatic support, high quality adjunct with a minor amount of yogurt or cheddar cheese was also be considered. Lactulose was suggested long term and Metronidazole was recommended for 14 days with nutraceuticals following the scan. Alternatively, a surgical consultation is recommended. If surgical intervention is to be performed, which was the primary recommendation in this case, the surgeon must be prepared for the potential of the onset of portal hypertension at the time of surgery post ameroid placement. Ideally US-guided lievr biopsy would be performed if only medical approach is taken in order to potetnially refine thereapy based on the presence of concurrent disease. Special thanks to Seth Mitchell, DVM of Mobile Veterinary Imaging of SE Florida ( for his submission of this case and continually utilizing the remote consultation & support services of We would also like to thank Dr. Stengard at the Vero Beach Veterinary hospital.  


Small bright well defined bladder calculi typical of ammonium biurate stones. The presence of bladder stones of this type in a young dog should bring shunt potential on the diagnostic radar. Positive predictive factor (PPF) 1 for shunt presence can be seen in our abstract in the SonoPath resources tab. ( ECVIM, Tolousse, France. Sept 8-11, 2010. Sonographic Whole Body Parameters of Portosystemic Shunts in 38 Dogs & Cats.
Strongly shadowing renal pelvic calculus in the left kidney in a young dog. PPF number 2 for shunt.
Strongly shadowing renal pelvic calculus in the right kidney in a young dog. PPF number 2 for shunt.
One, two, three vessels for the price of 2. In this long axis view in the dorsal liver along the diaphragm we should see the CVC in the near field and the aorta in the far field. The Doppler enhanced vessel between them is the azygos shunt creating a "double aorta" that is consistent with azygos shunt (see diagram in still image one). Normally the azygos is not seen and atrophied prior to birth and only the CVC and aorta would be visible in this view.
Tortuous spleno-azygos shunt as it enters the aortic hiatus leaving the abdomen dorsally then enters the thorax cranially. A truly "rock star" image by Dr. Seth Mitchell.