How to perform a surgical hepatic biopsy - Veterinary Medicine
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How to perform a surgical hepatic biopsy
An open surgical method greatly improves your chances of obtaining a diagnostic liver biopsy sample. The specific biopsy technique you should use depends on the site from which you are sampling.


VETERINARY MEDICINE


PERIOPERATIVE CONSIDERATIONS

All patients should undergo presurgical diagnostic tests (complete blood count, platelet count, serum chemistry profile, coagulation tests, urinalysis) to determine which perioperative treatments should be administered. For example, animals with liver disease may present with vomiting that could result in dehydration and electrolyte abnormalities. Preoperative potassium or magnesium deficiencies may cause ileus, arrhythmias, and other complications during or after surgery, so they are best corrected before anesthesia. Animals with severe liver disease or sepsis may have prolonged clotting times, requiring crossmatching and transfusion before surgery.2,3 Animals suspected of having neoplasia should undergo staging of their disease, including thoracic radiography and abdominal ultrasonography. Aspirates obtained during ultrasonography may provide a diagnosis in some patients, obviating the need for surgery.

If possible, fast patients for 12 hours before surgery. Preoperatively, administer fluids and analgesics. Give hypoalbuminemic patients colloidal fluids such as hetastarch or plasma to provide oncotic pressure support. Choose premedicants and dosages with care since metabolism of some drugs may be delayed when liver dysfunction is present. We commonly use an opiate combined with a benzodiazepine in dogs and cats or a combination of ketamine and diazepam in cats. If acepromazine is administered as a sedative, the total dose should not exceed 0.25 mg. Induction can be performed with intravenous propofol or by mask induction with isoflurane. Clip patients undergoing liver biopsy to the midsternal level, and clip patients receiving feeding tubes farther laterally on the abdomen. All patients should have an appropriately sized endotracheal tube with an inflated cuff. During anesthesia, continuous-rate infusions of fentanyl can be administered to reduce gas anesthetic requirements.9,10 These infusions can be continued postoperatively to provide analgesia.

Ideally, respiratory and cardiac function and oxygenation should be monitored during anesthesia with a capnograph, electrocardiograph, arterial blood pressure monitor, and pulse oximeter. Maintaining intraoperative blood pressure with fluids and oncotic support is critical in patients with liver disease since reduced hepatic perfusion can have deleterious effects on postoperative liver function. Forced-air heating blankets (e.g. Bair Hugger—Arizant Healthcare) can be used to keep patients warm during the procedure.

Prophylactic antibiotics are usually unnecessary in patients undergoing liver biopsy. Be prepared to take culture samples during the procedure and to place feeding tubes in some patients. Cautery should be available intraoperatively for patients with coagulopathies. Count the sponges and laparotomy pads before the abdomen is opened and again before it is closed to prevent iatrogenic peritoneal foreign bodies. Suction all fluid from the abdominal cavity before closure.

Postoperative treatments, complications, and prognosis vary depending on the underlying disease process and the patient's condition. Most animals continue to receive fluid support and analgesics after surgery. In patients that are not vomiting, small amounts of food and water can be offered within eight hours of the procedure.

OPEN SURGICAL BIOPSY TECHNIQUE

Make a ventral midline abdominal incision. The incision should extend cranially to the level of the xiphoid to improve exposure of the liver, particularly if it is small. Liver exposure can be improved by removing the falciform fat and by carefully incising the triangular ligaments or by placing moistened laparotomy pads between the liver and the diaphragm.2,3 Examine the entire liver visually and by gentle palpation for nodules, cavitations, and other abnormalities.


Figures 1,2
Obtain samples at the junction of normal and diseased tissue to ensure that both abnormal and normal hepatocellular structures are included.11 If the liver is diffusely affected, obtain biopsy samples from the most accessible location, usually the liver margin. In conditions in which lesions are distributed irregularly, obtain samples from multiple lobes to increase the likelihood of obtaining a diagnostic sample. Although affected liver margins typically suggest parenchymal disease, their greater distance from hepatic blood supply may predispose them to fibrosis, obscuring the underlying pathology. Misdiagnosis of hepatic fibrosis can be avoided by taking larger or multiple samples.2,12


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Source: VETERINARY MEDICINE,
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