The Liver Part 2: Abnormal
Read Below: The Liver Part 2: Abnormal
There are many liver conditions seen in dogs and cats. It is important to consider the following:
- Ultrasonographic changes are seldom pathognomonic
- Multiple pathologies and/or ultrasonographic changes can be present together
- Ultrasound findings should be interpreted alongside the findings of a clinical exam, results of haematology and biochemistry, and cytology/histopathology samples
The ultrasonographic appearance of hepatic disorders can be categorised as diffuse, focal or multifocal.
Diffuse disorders
The differential diagnoses for diffuse disorders typically affecting all liver lobes can be classified by their effect on parenchymal echogenicity: hyperechoic (Figure 1), hypoechoic (Figure 2), or a combination of both (mixed; Figures 3 and 4). Echotexture, size and shape may also be affected.
Diffuse conditions can be difficult to differentiate from poorly defined multifocal disease. Tissue sampling via fine needle aspiration (FNA) or biopsy is often essential to establish a definitive diagnosis.
| Diffuse Hyperechogenicity | Diffuse Hypoechogenicity | Mixed Echogenicity |
| · Steroid Hepatopathy
· Vacuolar hepatopathies · Lipidosis · Fibrosis · Cirrhosis (Figure 4) · Chronic hepatitis · Lymphoma · Mast Cell Tumour |
· Acute hepatitis or cholangiohepatitis
· Passive congestion · Lymphoma · Leukaemia · Amyloidosis · Histiocytic neoplasia |
· Combined processes such as steroid hepatopathy with nodular hyperplasia (Figure 3)
· Hepatitis · Lymphoma · Metastasis · Necrosis · Amyloidosis |
Figure 1. Hyperechoic Liver – in this image the liver (L) is diffusely hyperechoic. The neighbouring spleen (S) appears hypoechoic relative to the liver parenchyma. The margins of the portal vessels within the liver are difficult to visualise given the increase in hepatic echogenicity. (Image courtesy of Dr Sally Griffin, Willows Referrals. Not for reproduction).
Figure 2. Hypoechoic Liver – in this image the liver parenchyma is diffusely hypoechoic. In contrast to Figure 1 the walls of the portal vessels appear more prominent than usual (arrows). (Image courtesy of Dr Sally Griffin, Willows Referrals. Not for reproduction).
Figure 3. Steroid Hepatopathy with Nodular Hyperplasia – The liver appears diffusely hyperechoic with multifocal hypoechoic nodules (arrows).
Figure 4. Hepatic cirrhosis – this image shows part of the liver in a patient with ascites. The liver margins are irregular, and the parenchyma has become hyperechogenic with rounded hypoechoic areas representing nodular regeneration (*). (Image courtesy of Dr Sally Griffin, Willows Referrals. Not for reproduction).
Focal and multifocal disorders
The differential diagnoses for focal or multifocal liver conditions can be categorised as anechoic, hyperechoic, hypoechoic and mixed echogenicity (Figure 5 and 6). Size (or size range), location, number and echotexture should also be described.
As for diffuse conditions affecting the liver, FNA and biopsy sampling are important procedures to help differentiate benign and malignant processes.
Indicators of malignancy include the presence of “target” lesions – nodular areas with a hypoechoic rim and an iso- or hyperechoic centre1 (Figure 5), and masses > 3cm diameter in combination with peritoneal effusion2.
| Anechoic | Hypoechoic | Hyperechoic | Mixed |
| · Cyst
· Cystic tumour · Abscess · Necrosis |
· Nodular hyperplasia
· Lymphoma · Haematoma · Primary neoplasia · Metastatic neoplasia · Necrosis · Complex cyst |
· Nodular hyperplasia
· Granuloma · Mineralisation · Gas · Primary neoplasia · Metastatic neoplasia · Myelolipoma |
· Nodular hyperplasia
· Primary neoplasia · Metastatic neoplasia · Haematoma · Abscess |
Figure 5. Hepatic metastases – two focal lesions within the liver parenchyma (arrows). The larger lesion in the near field of the image shows the features of a “target” lesion – a hypoechoic rim with a more hyperechoic centre.
Figure 6. Hepatocellular carcinoma – a large heterogenous focal mass showing mixed echogenicity is visible in the cranial part of the liver (arrows).
Liver Sampling
Due to the variability in appearance of hepatic pathologies, sampling for cytology and histopathology is essential in order to achieve a definitive diagnosis.
Ultrasound-guided percutaneous FNA and tissue core biopsy can both be performed. Using ultrasound allows prior assessment of the depth and position of the area to be sampled. Similarly, doppler ultrasonography can be used to assess the vascularity of the region prior to sampling. Post-procedure ultrasonography allows monitoring of the sampled area for haemorrhage.
Fine needle aspirates – Usually performed as a “first line” procedure for liver sampling. This can be carried out with patients under sedation. A 20-22 gauge needle is used and both aspiration and non-aspiration techniques can be performed. A non-aspiration technique was shown to result in less blood contamination in splenic samples3. Appropriate needle length will be dependent on the depth of the region to be sampled. A 1.5inch needle can be used for diffuse pathologies. Fine needle aspiration can also be used to drain cavitary lesions such as cysts.
Tissue core biopsy – These should be performed under general anaesthesia, and coagulation status should be assessed prior to the procedure via screening tests such as platelet count, prothrombin time (PTT) and activated thromboplastin time (APTT) Depending on the size of the patient, a 16-18 gauge needle is used with a 2 cm sample notch.
Manual, automatic and semi-automatic needles can be used, though it is important to be familiar with the type used and the “throw” of the needle.
Consideration should also be given to surgical liver (wedge) biopsy in cases where pathology or local anatomy makes percutaneous sampling unsafe. An example of this would be in cases of microhepatica where a safe percutaneous window to access the liver may not be found.
References
- Cuccovillo A., Lamb C.R. (2002) Cellular features of sonographic target lesions in the liver and spleen of 21 dogs and a cat. Veterinary Radiology and Ultrasound 43: 275-278.
- Guillot M., d’Anjou M.A., Alexander K., Bdard C., Desnoyers M., Beauregrad G., Del Castillo J.R.E. (2009) Can sonographic findings predict the results of liver aspirates in dogs with suspected liver disease? Veterinary Radiology and Ultrasound 50: 513-518.
- Le Blanc C.J., Head L.L., Fry M.M. (2009) Comparison of aspiration and non-aspiration techniques for obtaining cytologic samples from the canine and feline spleen. Veterinary Clinical Pathology 38: 242-246.
Further reading
d’Anjou M.A., Penninck D (2015) Liver, In: Atlas of Small Animal Ultrasonography 2nd edn., Eds. Penninck D., d’Anjou M.A., John Wiley & Sons, Inc. Chichester, pp 183-238.
Gaschen L. (2009) Update on hepatobiliary imaging. Veterinary Clinics of North America: Small Animal Practice 39: 439-467.
Griffin S. (2018) Feline abdominal ultrasonography: what’s normal? what’s abnormal? The liver. Journal of Feline Medicine and Surgery 21: 12–24.
Larson M. (2018) Liver and Spleen, In: Textbook of Veterinary Diagnostic Radiology7th edn., Ed. Thrall D., Elsevier, St. Louis, pp 792-822.
Liffman R., Courtman N. (2017) Fine needle aspiration of abdominal organs: a review of current recommendations for achieving a diagnostic sample. Journal of Small Animal Practice 58: 599–609.
Nyland T.G., Larson M., Mattoon J.S. (2015) Liver, In: Small Animal Diagnostic Ultrasound 3rd edn., Eds. Mattoon J.S., Nyland T.G., Elsevier, St. Louis, pp 332-399.
Rademacher N. (2011) Liver, In: BSAVA Manual of Canine and Feline Ultrasonography, Eds. Barr F., Gaschen L., BSAVA publications, Gloucester, pp 85-99.
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