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Animals suffering from extra-hepatic biliary obstruction (EHBO) are often profoundly unwell. The reduced flow of bile salts into the gastro-intestinal (GI) tract allows GI bacteria to proliferate and eventually translocate across the intestinal wall. In addition, biliary stasis reduces the function of Kupffer cells within the liver, reducing their ability to remove and neutralise translocated bacteria from the portal blood. These animals should be stabilised adequately before any surgical repair is attempted.
Animals suffering from extra-hepatic biliary obstruction (EHBO) are often profoundly unwell. The reduced flow of bile salts into the gastro-intestinal (GI) tract allows GI bacteria to proliferate and eventually translocate across the intestinal wall. In addition, biliary stasis reduces the function of Kupffer cells within the liver, reducing their ability to remove and neutralise translocated bacteria from the portal blood. These animals should be stabilised adequately before any surgical repair is attempted.
====Jaundice====
* Jaundice is also known as icterus.
* Jaundice is a yellowish discoloration due to excessive levels of bilirubin in plasma.
** Seen in tissues that are normally white, e.g.
*** Fat
*** Intima of blood vessels
*** Sclera
* Bilirubin stains brown with H&E, like both haemosiderin and lipofuscin.
** Must be distinguished from each other by special stains.
*** Bilirubin stains bright green with a Fouchet stain.
=====Production of Bilirubin=====
* Red blood cells either undergo:
** Phagocytosis, in the case of ageing cells.
** Haemolysis, in haemolytic crises.
* Haemoglobin is freed from the red cells and is further broken down in the reticulo-endothelial system to haeme and globulin.
** Haeme is a mixture of iron and porphyrin.
** Both the iron and globulin are recycled for further use in erythropoiesis.
* The porphyrin from haemoglobin breakdown is converted to biliverdin.
** A green pigment
*** May contribute to the greenish appearance seen in local bruising.
* Biliverdin is subsequently changed into bilirubin.
* The bilirubin is then bound to albumin, and transported in the blood to the [[Liver - Anatomy & Physiology|liver]].
** In the hepatocyte, bilirubin is released from the albumin and conjugated with glucuronic acid.
*** Forms conjugated bilirubin.
**** Excreted into the intestine via the bile ducts.
===== Prehepatic (Haemolytic) Icterus=====
* Due to excessive production of bilirubin due to haemolysis, e.g.
** [[Babesia|Babesiosis]]
** [[Leptospira|Leptospirosis]]
** Copper poisoning in sheep.
* There is excessive unconjugated bilirubin in the blood.
=====Hepatic (Toxic) Icterus=====
* Due to [[Liver - Anatomy & Physiology|liver]] cell damage.
** In hepatocytic [[Necrosis - Pathology|necrosis]], the liver cannot conjugate bilirubin.
*** Results in increased levels of unconjugated bilirubin in the blood.
** In less severe damage, the hepatocytes swell and bile caniculi are pressed closed.
*** There is therefore intrahepatic obstruction conjugated bilirubin accumulated in the blood.
* In reality, these situations occur together.
** There is both excessive unconjugated and conjugated bilirubin in the blood.
* Examples:
** [[Leptospira|''Leptospira icterohaemorrhagica'']] in the dog.
** Rift Valley fever virus.
** Some plant poisonings.
*** Lantana.
** Some fungal infections.
*** Aflatoxicosis.
=====Post-Hepatic (Obstructive) Icterus=====
* Due to the flow of bile being obstructed, for example by:
** [[Biliary Tract - Obstruction|Gallstones]]
** [[Parasites|Parasites]]
*** [[Ascaris suum|''Ascaris suum'']] in the bile ducts of pigs.
** [[Neoplasia - Pathology|Tumours]]
*** Adenocarcinoma of pancreas presses upon and occludes the bile duct.
* Results in excessive conjugated bilirubin in the blood.
* Constructive icterus causes, out of the three types of icterus,
** The most elevated levels of bilirubin in the blood
** The greatest discoloration of the tissues of the body.
=====Van de Berg Test=====
* This test can distinguish between the different types of jaundice, based on whether the bilirubin is conjugated or not.
* Plasma from the jaundiced animal is treated with an aqueous solution of a reagent (diazotised sulphanilic acid).
** Gives a red-purple colour.
*** The intensity of this colour is directly proportional to the amount of water-soluble (i.e. conjugated ) bilirubin in the sample.
** Further addition of alcohol intensifies the colour if there is non-water-soluble (i.e. unconjugated) bilirubin also present.
*** The intensified colour is directly proportional to the total amount of bilirubin present in the sample.
** The difference between the two readings gives the amount of unconjugated bilirubin in the sample.
==Test yourself with the Liver Pathology Flashcards==
==Test yourself with the Liver Pathology Flashcards==
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