Performing a liver biopsy

Liver biopsy and analysis of samples are important steps in diagnosing hepatic disease. Fine-needle aspirates of the liver tend to have poor diagnostic accuracy, as low as 30% when compared with histopathology in one study, leading to the recommendation for surgical biopsies.¹ Depending on the underlying disease process, these patients may be systemically ill, with prolonged clotting times, ascites, or significant cirrhosis of the liver, which can make surgical biopsies more challenging and at a higher risk for complications. The most significant risk to consider, given the function of the liver, is bleeding. As a result, checking a patient’s clotting times prior to obtaining biopsies is generally recommended.

General liver biopsy principles

When obtaining liver biopsies for a patient, it is important to do so in a manner that maximizes the likelihood of a diagnosis while minimizing risk to the patient. In 2019, the American College of Veterinary Internal Medicine published a consensus statement on the diagnosis and treatment of chronic hepatitis in dogs that outlines recommendations for the procurement of samples and submission processes.

Samples must be large enough that 12 to 15 portal triads are obtained. Additionally, sampling different liver lobes is recommended, as there may be variation between different lobes. Finally, samples should also be submitted for aerobic and anaerobic culture and copper quantification. Twenty to 40 mg of liver are required to submit a sample for copper quantification. Ultimately, this has resulted in the recommendation for a minimum of 3 surgical biopsy specimens from at least 2 liver lobes for histopathology: 1 for anaerobic/aerobic culture and 1 for copper quantification.

Ultrasound-guided biopsy

One of the least invasive options for liver biopsy is using a biopsy instrument, such as a Tru-Cut biopsy device. This core biopsy needle enables sampling larger lesions than a fine-needle aspirate. These samples can be obtained with ultrasound guidance. Studies have found these samples to be 48% to 83% consistent with surgical liver biopsies.^2,3 There is a larger possibility of hemorrhage with this technique compared with fine-needle aspirates, although the likelihood of major life-threatening hemorrhage is low. Although this is certainly the least invasive option that exists for liver biopsy, diagnostic accuracy may be limited by sample size. If relying on needle biopsy for sampling, more than 4 specimens are recommended to ensure the requisite number of portal triads is obtained.⁴ These samples often also need additional care when handling because of their small size. It is easy to crush or otherwise induce artifacts into these samples.

Open liver biopsy techniques

There are multiple techniques for performing liver biopsies via a celiotomy. Ultimately, the choice of technique is at the discretion of the primary surgeon.

One of the easiest techniques is obtaining a biopsy of the periphery of a chosen liver lobe via the guillotine technique. For this technique, a portion of the liver lobe periphery that is more pointed or comes to a taper is selected, and a loop of absorbable suture, such as polydioxanone, is placed around it. The loop is tightened, and the liver lobe is ligated and then transected distal to the suture. This sample can then be submitted for histopathological analysis or, if of an appropriate size, can be divided into different portions for culture and copper quantification. Even if the sample is of an appropriate size to be divided into multiple portions, it is important to remember the previously stated recommendations regarding sampling multiple liver lobes due to potential variation between them.

Another appropriate technique, particularly if a lesion is not on the periphery, is the use of a biopsy punch. This may be used anywhere in the liver, although caution should be used toward the center and hilus of the liver lobe to be biopsied. When using a biopsy punch, care should be taken to penetrate no more than half the depth of the lobe. Some hemorrhage is to be expected, and a gelatin sponge may be placed into the defect that is created. Hemorrhage is reported to be greatest with this technique but rarely requires intervention.²

Finally, it is also acceptable to use vessel sealing devices to seal and transect a portion of the liver. However, a large enough sample must be acquired, as the use of these devices will result in some thermal spread and artifact throughout the edge of the sample.

Laparoscopic liver biopsy

Laparoscopic liver biopsy is a safe technique that results in highly diagnostic samples. The magnification and illumination associated with laparoscopic surgery may also aid in targeted biopsy of lesions, and the use of laparoscopy can result in reduced pain and a faster recovery.^5-7 This is typically performed with two 5-mm single instrument ports or 1 multi-instrument port to facilitate a 5-mm camera and 5-mm cup biopsy forceps. Multiple techniques exist, such as forcefully pulling once the cup biopsy has been closed over a liver lobe, rotating the forceps 360° in one direction after closing until the sample twists off, or even pulling the forceps through the laparoscopic cannula while simultaneously advancing the cannula to use it as a dissection device.

Image courtesy of Rachel Williams, DVM, DACVS-SA

Figure: Liver biopsy.

All these techniques have been proven to be safe and effective, but the twisting technique is reported to have the fewest artifacts.⁸ Some bleeding can be expected with laparoscopic liver biopsies (Figure), but it should be relatively mild and self-limiting. Careful assessment of all biopsy sites for active hemorrhage should be performed prior to closure. If persistent hemorrhage is noted, this may be addressed with electrocautery, a vessel sealing device, or other hemostatic agents, or conversion to an open approach may be necessary.

Postoperative management

Postoperatively, patients should be monitored for pain and hemorrhage. Vital signs may be early indicators of bleeding and should be recorded. Many surgeons recommend checking the packed cell volume/total solids and blood pressure 2 to 4 hours after surgery to monitor for a significant decrease in those values. If that is the case, hemorrhage is a possibility, and a point-of-care ultrasound is prudent to look for evidence and sample if indicated.

Most patients that undergo liver biopsies can be discharged the same day. They should be discharged with analgesics as appropriate for the procedure performed. There is generally no need to discharge patients on antibiotics or steroids, and prescribing these medications should be delayed until the results of the biopsy samples are available.

Rachel Williams, DVM, DACVS-SA, is a clinical assistant professor of small animal surgery at the University of Florida College of Veterinary Medicine in Gainesville. Her professional interests include urogenital surgery, minimally invasive surgery, and wounds and reconstruction. Outside the operating room, she enjoys being outdoors with her dogs, as well as gardening and traveling.

REFERENCES

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8. Buote NJ, Loftus JP, Miller AD. Laparoscopic twist technique has the best overall artifact profile when comparing three laparoscopic hepatic cup biopsy techniques for dogs. Am J Vet Res.2022;83(12):ajvr.22.08.0127. doi:10.2460/ajvr.22.08.0127