General Information

Biopsy of the hepatobiliary tree is often required for investigation of hepatobiliary disease. Techniques for biopsy of the hepatobiliary tree include needle biopsy (Tru-cut biopsy), laparoscopic biopsy (cup forceps), surgical biopsy (i.e. wedge or guillotine biopsy), and liver lobectomy. Gall bladder sampling most often involves cholecystectomy, but incisional biopsies may also be taken.

• Selection of the appropriate biopsy technique is at the veterinarian’s discretion. This decision should be made in conjunction with the patient’s clinical state, coagulation capability and results of other diagnostic testing, and clinical differentials.
• In general, pathologists prefer biopsies that are obtained laparoscopically or surgically. These samples tend to have fewer artefacts, allow for enhanced assessment of the liver architecture, and provide sufficient tissue for additional testing (such as immunohistochemistry, PARR, and special stains including copper staining). However, needle biopsies are a less invasive sampling technique and may be more appropriate for certain patients.

Submission form and relevant patient history

The pathologist will interpret the biopsy histology in the context of the available clinical information.

• Please include the full animal details and a detailed clinical history. Include a description of the lesions and their distribution, the timeframe and progression of disease, any previous or ongoing treatments (including antibiotics), and travel history.
• Include the results of any bloodwork (including serum biochemistry, bile acid stimulation testing, and coagulation testing), including the reference ranges
• If cytology or other testing has been performed, please include the previous submission number (if performed at VPG) or include a copy of the results (if performed elsewhere)
• If photos or imaging results are available, please include these because they can aid the pathologist in accurate interpretation

Photos can be uploaded to PATHPORT, emailed to [email protected], or printed and attached to the submission form.

Sampling guidelines

Current guidelines for investigation of hepatobiliary disease recommends a minimum of 12-15 portal tracts be available for histologic examination. Artefacts introduced during sampling, such as crush, shearing, or puncture of the liver by sponges in cassettes, can reduce the number of intact lobules and inhibit histologic interpretation.

 

To maximise the pathologist’s ability to achieve a diagnosis and to have adequate tissue for additional tests, multiple needle biopsies (>4, ideally from a 14 gauge needle) or laparoscopic, cup forceps biopsies (2-4) are required.

• Multiple lobes should be sampled and labelled according to the lobe from which they were obtained (if it can be identified). If specific lesions are sampled (for example masses), these should be placed in a separate pot and labelled.
• Biopsies for histology should be placed in a labelled pot containing 10% neutral buffered formalin at a ratio of 10:1 (formalin : tissue).
  • Put needle biopsies in a mesh cassette, taking care not to crush the samples. Avoid using sponges, which can puncture the tissue and introduce artefact.

Large biopsies, including partial or complete lobectomies, may not fix fully. To enhance fixation, incise the lesional areas such as masses.

• If margin assessment is required, avoid incising the margin. If you have histologic marking ink at your clinic, consider applying the ink to the margin prior to placing the sample in formalin and/or incising it.
• Note: Staples must be cut out of the tissue before it can be processed. Consequently, if surgical margins are stapled, this may interfere with histologic margin assessment.

 

Liver lobe with 2 masses (yellow stars). To improve fixation, incise the lobe at approximately 2cm intervals. Avoid the surgical margins.

Sampling of patients with suspected canine chronic hepatitis

Laparoscopic biopsies are preferred for sampling patients with suspected chronic hepatitis. However, needle biopsies may also provide sufficient tissue for diagnosis, if enough biopsies are obtained. The current ACVIM consensus guidelines for investigation of canine chronic hepatitis recommend obtaining  biopsies for histology, culture, and copper quantification.

• Histology: 3 laparoscopic biopsies or 4+ full length, 14 gauge (2cm long) needle biopsies, placed in labelled pot(s) of 10% neutral buffered formalin
  • Copper staining of formalin-fixed liver biopsies is recommended for patients with suspected chronic hepatitis, to allow for assessment of copper accumulation in relation to the pathologic changes. Copper staining may be performed as part of the initial histologic assessment or can be requested after the histology has been performed.
• Copper quantification: 1 laparoscopic biopsy or 1 full length, 14 gauge (2cm long) needle biopsy in a sterile, liquid free, labelled pot
  • Note that copper quantification requires approximately 20-40mg of liver (wet weight). Insufficient amounts of tissue may yield inaccurate results. This equates to approximately 1 full length 14 gauge (2cm long) needle biopsy or ½ of a 5mm laparoscopic biopsy specimen. A full length 18 gauge needle biopsy provides only 3-5mg of tissue.
• Culture: 1 laparoscopic biopsy in a sterile, liquid-free, labelled pot
  • In some cases (for example, sampling of liver abscesses), a swab may be indicated. These should be placed in the appropriate transport medium, labelled, refrigerated until transport, and transported to the laboratory as quickly as possible.

Sampling of patients with suspected biliary disease

In patients with suspected biliary disease (including cats with cholangiohepatitis), evaluation of bile, bile “sludge”, cholecystoliths/choledocholiths, and/or the gall bladder may be indicated in addition to liver histology

• Culture can be performed on fluid, bile sludge and/or stones, and gall bladder and liver (swabs or tissue).
  • These should be placed in the appropriate transport medium or a sterile container. Culture samples should be refrigerated until they are sent via courier to the appropriate laboratory, as quickly as possible.
• Cytology specimens of the liver and/or bile should be placed in a separate parcel from formalin samples because formalin fumes can alter cellular morphology, limiting cytologic interpretation.
• The gall bladder has a thick wall, which can slow the rate of formalin penetration and inhibit fixation. To expedite fixation, it can be incised. If margin assessment is required, avoid cutting into the relevant margin.

Sampling of patients with suspected lymphoma

Formalin fixation can inhibit PCR including PARR (PCR for antigen receptor rearrangement), which may be recommended by the pathologist to investigate for a clonal lymphocyte population and the diagnosis of lymphoma.

• If lymphoma is suspected clinically (particularly in cats with suspected lymphocytic cholangitis/cholangiohepatitis or small cell lymphoma), consider placing one biopsy sample in saline for PARR, if needed.

Interpreting the Pathology Report

We will always strive to give you a definitive diagnosis. However, in some cases, for various reasons this may not be possible. In those cases we will provide an opinion on the most likely diagnosis and possible differential diagnosis and discuss further diagnostic tests, if applicable. In particular in cases with some uncertainty regarding the diagnosis, it is important to compare to the clinical picture, list of clinical differential diagnoses, and results of other tests (e.g. imaging) that you may have done. We are always happy to discuss any questions you may have regarding the histopathology report.

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Quick Facts

• Aim for 4+ needle (14g) or 2-4 laparoscopic cup biopsies for liver histology.
• Consider taking samples for liver cytology, culture, copper quantification, and PARR.
• Bile, choleliths, bile sludge, and gall bladder sampling may also be indicated.
• Clearly label all samples with the patient name and site.
• Make incisions into larger samples (avoiding marginal areas) to aid fixation.
• Histology samples should be put in labelled, leak-proof containers containing 10% neutral buffered formalin.
• Cytology slides should be clearly labelled with the patient name and site and placed in break-free slide holders in a separately labelled bag.
• Include the submission form in a labelled bag. The pathologist will incorporate any provided clinical information into their interpretation, so we thank you for your thoroughness.

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For more information on our histopathology services please visit our Histopathology page or contact us by calling 0117 951 1283 or emailing [email protected].

Reference:

Webster CRL, Center SA, Cullen JM, et al. ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med. 2019; 33: 1173–1200. https://doi.org/10.1111/jvim.15467