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