title: Variation in fat content between liver lobes and comparison with histopathological scores in dairy cows with fatty liver.
abstract: BACKGROUND
  The assessment of a liver biopsy remains the gold standard for diagnosing and staging fatty liver in dairy cows, which is often necessary for diagnostic and research purposes. Accuracy of the diagnosis relays on the quality of the biopsy, the assumed representativeness of a small tissue sample for a disease process throughout the liver and accurate human evaluation of histologic specimens. The objective of the present study was to assess the distribution of triacylglycerol (TAG) infiltration throughout the parenchyma of livers with different degrees of fatty liver in dairy cows. In addition, histopathological scores from the corresponding specimens were compared to a quantitative measurement of TAG, as well as the agreement between two observers.
  
  
  METHODS
  Thirty livers with different degrees of lipid infiltration were selected and 10 different locations throughout the liver were assessed. The TAG content was measured enzymatically, calculated in % or mg/g wet weight, and assigned to a scoring system. Corresponding tissue specimens were stained with hematoxylin-eosin (H&E) and Oil red O (ORO) for histopathological evaluation, using a scoring system.
  
  
  RESULTS
  The difference in TAG content between any locations was less than 2%. Based on the scoring system the TAG concentration was even distributed in 79.3% of the livers. Based on kappa statistics the agreement between two pathologists and staining technique in scoring histological specimens was moderate to fair.
  
  
  CONCLUSIONS
  Overall the distribution of TAG throughout the liver and the accuracy of human evaluation of liver biopsies may lead to acceptable diagnoses for clinical purposes. Within the liver lobules a common pattern of lipid distribution depending on severity could be observed. For the staging of lipid infiltration for research projects, some degree of variation needs to be considered.
authors.affiliation: Department of Farm Animals, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, Zurich, Switzerland. cgerspach@vetclinics.uzh.ch.
authors.forename: C
authors.initials: C
authors.lastname: Gerspach
authors.affiliation: Institute of Pharmacology and Toxicology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057, Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Imhasly
authors.affiliation: Department of Farm Animals, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Klingler
authors.affiliation: Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 268, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Hilbe
authors.affiliation: Section of Epidemiology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 270, Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Hartnack
authors.affiliation: Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 268, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Ruetten
mesh_terms: D000818:Animals; D001706:Biopsy / Q000592:standards / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis / Q000473:pathology*; D005234:Fatty Liver / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D005260:Female; D008055:Lipids / Q000032:analysis*; D008099:Liver / Q000737:chemistry* / Q000473:pathology*
chemical_list: D008055:Lipids