Introduction

• The procedure is best performed in a quiet room with reduced lighting.
• The patient should be still for the examination, often sedation is required.
• A nurse is required to assist in restraint of the patient.
• Optimal probe to skin contact is required.
• The patient identification, date and name of practice should be entered into the ultrasound machine before commencing the procedure.
• Images of the examination should be kept for future reference, either as thermal prints, on video tape, on multiformat camera, or saved on hard disc.

Uses

• Assessment of:
  • Palpable or radiographic hepatomegaly     .
  • Radiographic microhepatica     .
  • Palpable or radiographic hepatic mass.
  • Palpable or radiographic cranial abdominal mass.
  • Metastatic disease.
  • Ascites.
  • Jaundice.
  • Abnormalities in hepatic biochemical parameters.
  • Fever of unknown origin.

Advantages

• Non-invasive.
• Straightforward.
• Non-painful.
• Available in many practices.
• Allows guided biopsies.
• Short time required for assessment - 10-15 min, dependent upon patient compliance and skill of ultrasonographer.

Experience will significantly reduce time required.

Disadvantages

• Requires clipping of patient's coat.
• Normal ultrasonographic appearance does not exclude disease.
• Abnormal ultrasonographic appearance does not always represent significant disease.
• Similar ultrasonographic appearance with different diseases.

Problems

• Inadequate probe-skin contact.
• Inadequate clipping of coat.
• Inadequate use of ultrasound gel.
• Inadequate restraint of an active cat. Significant gastric distention from aerophagia reduces visibility. Avoid sedatives that aggravate gastric activity.
• Equipment failure.

Alternatives

• Radiography  Radiography: abdomen  : provides information about size, shape, radiopacity and margination of organ but not internal architecture.
• Cytopathology: fine needle aspirates   Fine-needle aspirate  can be obtained from the liver for cytological examination. The diagnostic value of this technique is improved by combining it with ultrasonography to guide the needle to the site of interest (particularly with focal lesions).
• Histopathology: percutaneous trucut biopsy or surgical biopsy taken at laparotomy. The diagnostic value of the former is also enhanced by combining it with ultrasonography.
• MRI/CT: provide detailed information about architecture of organ but use limited by reduced availability of equipment except through referral centers.
• Angiography: portovenography can be used to assess the portal vein.

Criteria

• Is the ultrasound examination appropriate?
• Can hepatic disease be confirmed without it?
• Can intra-abdominal metastatic disease be confirmed without it?
• Will the examination tell you what you need to know?
• Will the management of the patient be affected by the findings?
• Do you possess appropriate skills required?
  • Knowledge of normal anatomy, including location, vascular supply and drainage, and lymphatic drainage.
  • Knowledge of the normal ultrasonographic appearance.
  • Knowledge of the parenchymal variations seen with non-neoplastic disease.

Equipment

Procedure

Normal anatomy

Pathological changes

Contrast enhanced ultrasonography

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Hittmair K M, Vielgrader H D & Loupal G (2001) Ultrasonographic evaluation of gallbladder wall thickness in cats. Vet Rad Ultra 42 (2), 149-155 PubMed.
• Nyland T G, Koblik P D, Tellyer S E et al (1999) Ultrasonographic evaluation of biliary cystadenomas in cats. Vet Radiol Ultrasound 40 (3), 300-306 PubMed.
• Biller D S, Kantrowitz B & Miyabayashi T (1992) Ultrasonography of diffuse liver disease - A review. J Vet Intern Med 6 (2), 71-76 PubMed.
• Lamb C R, Hartzband L E, Tidwell A S et al (1991) Ultrasonographic findings in hepatic and splenic lymphosarcoma in dogs and cats. Vet Radiol 32 (3), 117-120 VetMedResource.

Other sources of information

• Lamb C R (1998) Ultrasonography of portosystemic shunts in dogs and cats. Vet Clin North Am Small Anim Pract 28 (4), 725-753.
• Partington B P, Biller D S (1998) Hepatic imaging with radiology and ultrasound. Vet Clin North Am Small Anim Pract 28 (4), 725-753.
• Miles K G (1997) Sonography of the liver, pancreas, and alimentary tract. In Consultations in Feline Internal Medicine. Ed: August J R; W B Saunders Company, Philadelphia: pp 79-90.
• Nyland T G, Mattoon J S & Wisner E R (1995) Ultrasonography of the liver. In Veterinary Diagnostic Ultrasound. Eds: Nyland T G & Mattoon J S; W B Saunders Company, Philadelphia. pp 52-73.