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S. Unterer1
1Clinic of Small Animal Medicine, Centre for Clinical Veterinary- Medicine Faculty of Veterinary Medicine, Munich, Germany
Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, LMU Munich
When investigating chronic liver disease, a cytological or histopathological assessment of liver tissue is frequently required. Prior to invasive sampling, it is necessary to exclude extrahepatic causes of elevated serum enzyme activities (e.g. due to endocrinopathies), extrahepatic causes of bilirubin elevation (e.g. due to sepsis), and extrahepatic causes of structural changes of the liver (e.g. due to steroid administration). Portosystemic vascular anomalies should be ruled out as well. If structural focal liver changes are present, preference should be given to less invasive technique such as contrast-enhanced ultrasonographic examination
over a liver biopsy to differentiate between benign and malignant nodes. Postoperative bleeding is the most common complication of liver biopsy. In order to minimize the risk of bleeding, biopsy can be performed when following hemostatic parameters are determined: platelet count (> 100 000 platelets/μl), platelet function (mucosal bleeding time <4 min), fibrinogen concentration (>50% of the lower limit of the reference interval), and coagulation times (< 1.5 fold prolonged). Various techniques for invasive liver sampling can be employed: 1. Fine needle aspiration (FNA) biopsy of the liver 2a. Ultrasound- assisted needle biopsy (Tru-cut biopsy) of the liver 2b. Laparoscopic or surgical biopsy of the liver 1: Fine needle aspiration (FNA) biopsy of the liver FNA is a simple and inexpensive method for investigating liver diseases. Due to its low complication rate, it is often the first invasive diagnostic step. The following changes are usually
being detected: A) Hepatic lipidosis Hepatic lipidosis, typically with vacuolization of >50% hepatocytes can
be easily detected on cytology. Hepatic lipidosis occurs usually during the course of another disease due to anorexia. It is sometimes possible that hepatic lipidosis is diagnosed by the cytological examination of a liver aspirate, but the inciting cause, for example an infiltrative hepatic disease, is not being recognized. B) Bacterial and parasitic infections of the liver and the bile duct In cats, neutrophilic cholangitis is a common cause of bile
duct inflammation due to bacterial infection arising from the intestinal tract. Cytological examination and culture (including antibiogram) of the bile is necessary for an exact diagnosis and for the optimization of treatment. An ultrasound-guided gallbladder aspiration is a safe method when specific rules are being observed. Gallbladder should be well filled and should be located close to the ultrasound probe. Patient should be anesthetized, so that movement does not occur during the aspiration. Additionally, a second person should aspirate the bile through an extension tube, so that the person performing the aspiration can fully concentrate on the procedure, and ensure that the needle moves as little as possible. Furthermore, gallbladder should be completely emptied, so that the intravesical pressure is low, and the risk of
a bile leakage through the puncture site is minimized. Analgesic administration is recommended before aspiration, and an intravenous broad-spectrum antibiotic administration is indicated after the aspiration in case
of suspected bacterial cholangitis. Bacteria or other infectious agents (e.g. Echinococcus sp.) can also be detected on liver cytology. C) Neoplasia
Round cell neoplasms such as lymphoma and mast cell tumor are easily diagnosed on liver cytology. Primary hepatic epithelial neoplasms (i.e. hepatocellular and cholangiocellular carcinoma) can sometimes
pose a diagnostic challenge. Hepatocytes from hepatocellular adenoma and some well-differentiated hepatocellular carcinomas cannot be differentiated from normal hepatocytes or hepatocytes in hyperplastic
or regenerative nodules. Therefore, in cases of solid neoplasia, a histological examination is often necessary for the assessment of infiltration and for definitive diagnosis. Mesenchymal neoplasms (hepatic sarcomas) often exfoliate poorly, resulting in low numbers of cells available for cytological evaluation. If non-diagnostic FNA samples are obtained, liver disease cannot be completely ruled out. In these cases, it is recommended to obtain biopsy samples for histopathological assessment.
2. Histopathological examination is often necessary
to diagnose inflammatory, neoplastic, fibrotic and degenerative changes in the liver tissue. Important parenchymal liver diseases such as chronic hepatitis
in the dog and various cholangitis forms in the cat can only be recognized from an adequate liver biopsy. 2a: Ultrasound-assisted needle biopsy (Tru-cut biopsy) of the liver
This procedure can be performed in sedated patients, is considered a low-risk and is cheap. Tru-cut biopsy
is contraindicated when a small, ultrasonographically poorly recognizable liver or abdominal effusion are detected on ultrasonographic examination. High-spring shot biopsy should not be used in cats, as the strong
An Urban Experience

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