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| | + | ==Jaundice (Icterus)== |
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| − | Also known as: '''''Jaundice
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| − | ==Introduction==
| + | *this is a staining of the tissues with bilirubin or bilirubin complexes |
| − | [[File:Jaundiced cat.jpg|thumb|right|Image of a jaundiced cat, note the discoloured pinnae<br><small>(Image source Sabar 2007, Wikimedia Commons)</small>]]
| + | *bile pigments have a strong affinity for elastic tissue and thus the yellowish colour can be easily seen in the sclera and mucous membranes in life and in the aorta at necropsy |
| − | Icterus refers to the staining of tissues by [[Bilirubin|bilirubin]] pigment or bilirubin complexes. Bile pigments such as bilirubin have particular affinity for elastic tissues and the typical yellow/orange colour of icterus is therefore evident in the sclera and mucous membranes in life and in the tunica intima of the aorta at post-mortem examination.
| + | *the serum bilirubion level gives an indication of the degree of icterus |
| | + | **dog's normal range is usually below 0.5mg/100ml |
| | + | **level is at least 2mg/100ml when jaundice is clinically evident |
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| − | The serum bilirubin concentration of an animal indicates the degree of icterus and the condition only becomes clinically evident at levels above 2 mg/100 ml (normal range below 0.5 mg/100 ml). Bilirubin should be measured by a technique which measures the large proportion which is bound to plasma albumin.
| + | ===Causes=== |
| | + | *overproduction of bilirubin |
| | + | **eg haemolytic crises |
| | + | *diffuse [[Liver - Anatomy & Physiology|liver]] disease |
| | + | **where there is a decreased uptake, conjugation, and secretion of bilirubin |
| | + | *reduced outflow of bile into the gut |
| | + | **intrahepatic biliary obstruction eg foreign bodies, tumours, or fibrosis |
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| − | ==Causes of Icterus== | + | ===Classification types=== |
| − | ===Pre-hepatic Jaundice=== | + | ====Haemolytic jaundice==== |
| − | Also sometimes called '''Haemolytic Icterus'''. This condition results from increased red blood cell destruction, overwhelming the capacity of the [[Liver - Anatomy & Physiology|liver]] to conjugate and excrete the bilirubin which is released into the plasma. The majority of the bilirubin is therefore '''unconjugated''' and, unlike the conjugated form, this cannot be excreted by the [[Urinary System Overview - Anatomy & Physiology|kidney]]. Possible causes of haemolysis and prehepatic jaundice include:
| + | *due to increased red cell destruction |
| − | *'''Haemolytic bacteria''', including ''[[Clostridium haemolyticum]]'' in cattle and [[Leptospira|'''Leptospires''']] in various species. | + | **results in increased amounts of bilirubin in the reticuloendothelial system |
| − | *'''Haemolytic parasites''', including '''[[Babesia|Babesiosis]]''' in cattle and dogs and ''[[Feline Infectious Anaemia|Mycoplasma haemofelis]]'' in cats. | + | **the production may be at a rate which exceeds the capacity of the [[Liver - Anatomy & Physiology|liver]] to conjugate and eliminate it |
| − | *'''Immune reactions''' to red blood cells, including: | + | *most of bilirubin is unconjugated |
| − | **[[Neonatal Isoerythrolysis|'''Neonatal isoerthryolysis''']], resulting from the production of antibodies by the dam which are ingested by the neonate in colostrum and subsequently cause destruction of red blood cells. Bilirubin is able to cross the immature blood brain barrier and cause direct damage to the neurones of the brain, a phenomenon called '''kernicterus'''.
| + | *bile pigment is ''not'' excreted in the urine |
| − | **'''Autoimmune haemolytic anaemia''' or [[Immune Mediated Haemolytic Anaemia|'''immune-mediated haemolytic anaemia''']].
| + | **since the [[Urinary System - Anatomy & Physiology#Upper Urinary Tract|kidney]] can excrete only the water soluble conjugate |
| − | **Destruction of red blood cells of '''lambs fed with bovine colostrum'''.
| + | *diseases |
| − | *'''Hypophosphataemia''', which may occur in cattle with '''post-parturient haemoglobinuria''', in animals with '''diabetic ketoacidosis''' (DKA) which are rapidly stabilised with insulin and in '''refeeding syndrome'''.
| + | **''Babesiosis'' |
| − | *'''Inherited defects of red blood cell enzymes''', including phosphofructokinase and pyruvate kinase.
| + | **isoimmune reactions eg newborn foal whose dam has elaborated specific antibody against its red cells |
| − | *'''Microangiopathic damage''' to red blood cells as they pass through narrow or damaged blood vessels, as in '''haemangiosarcomata''', [[Disseminated Intravascular Coagulation|'''disseminated intravascular coagulation (DIC)''']] or '''[[Vasculitis|vasculitis]]'''.
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| − | *'''Oxidative damage''' to red blood cells, caused by '''paracetamol''' in cats, '''onion poisoning''' in dogs and [[Copper Toxicity|'''copper toxicity''']] in many species. Ingestion of red maple leaves may also cause haemolysis in horses, as may brassicas (such as rape and kale) in cattle and sheep.
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| − | Haemolysis which is sufficiently severe to cause icterus is likely to be life-threatening due to the reduction in oxygen-carrying capacity of the blood. Animals affected acutely may require transfusions of whole blood, packed red blood cells or synthetic bovine haemoglobin and it may be advisable to provide oxygen by nasal catheter, flow-by or mask. In addition, the presence of large amounts of haemoglobin may cause acute intrinsic renal failure (in addition to the pre-renal failure caused by reduced oxygen delivery to the kidneys) and neonates may suffer from kernicterus, direct damage to the central nervous system caused by bilirubin.
| + | ====Obstructive jaundice==== |
| | + | *due to bile duct obstruction |
| | + | *accumulation of conjugated bilirubin |
| | + | *bile pigment ''is'' excreted in the urine |
| | + | *bile pigment will be diminished in the faeces |
| | + | *diseases |
| | + | **carcinoma involving the head of the [[Pancreas - Anatomy & Physiology|pancreas]] |
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| − | ===Hepatic Jaundice=== | + | ====Hepatocellular jaundice==== |
| − | Also referred to as '''Toxic Icterus'''. [[Liver - Anatomy & Physiology|Liver]] cell damage may lead to jaundice by two main mechanisms:
| + | two factors are concerned in the production of jaundice following [[Liver - Anatomy & Physiology|liver]] cell damage |
| − | *In '''acute hepatic necrosis''' and [[Hepatic Lipidosis|'''hepatic lipidosis''']], damaged cells swell to such a degree that flow of bile in the canaliculi is obstructed. There is therefore intrahepatic obstruction and conjugated bilirubin accumulates in the blood. | + | *damage to [[Liver - Anatomy & Physiology|liver]] cells can interfere with the passage of bile along the bile capillaries |
| − | *In '''chronic [[Liver Failure|liver failure]]''', so much hepatic function is lost that the bilirubin produced by the constant turnover of red blood cells cannot be taken up and conjugated, leading to an accumulation of unconjugated bilirubin in the blood.
| + | **eg intrahepatic obstruction |
| − | * In reality, these situations occur together. There is both excessive unconjugated and conjugated bilirubin in the blood. | + | *[[Liver - Anatomy & Physiology|Liver]] cell damage may cause failure of conjugation and therefore excretion failure of bile pigment |
| − | * Examples: | |
| − | ** [[Leptospira|''Leptospira icterohaemorrhagica'']] in the dog.
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| − | ** [[Rift Valley Fever|Rift Valley fever virus]].
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| − | ** Some plant poisonings (''Lantana'')
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| − | ** Some fungal infections ([[Mycotoxins|Aflatoxicosis]])
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| − | ===Post-hepatic Jaundice===
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| − | Also called '''Obstructive Icterus'''. This occurs due to an [[Biliary Tract Obstruction|obstruction in the biliary tract]] which normally carriers bile from the liver and gall bladder to the duodenum. Conjugated bilirubin is found in the urine but, in complete obstruction, urobilinogen will be absent from the urine and stercobilin from the faeces. Possible causes of post-hepatic jaundice include:
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| − | *'''Intraluminal obstructions''':
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| − | **'''[[Choleliths]]''' ('gall stones') are much less common in animals than they are in humans. They are usually composed of bilirubin salts in dogs and calcium carbonate in cats, although they are very rare in the latter species.
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| − | **'''Gall bladder mucoceles''' produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
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| − | **'''Biliary neoplasia''', most commonly cholangiocellular cystadenoma (in cats) or carcinoma (in dogs).
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| − | **Aberrant migration of '''intestinal parasites''', including ''[[Ascaris suum]]'' in pigs and ''[[Parascaris equorum]]'' in horses. This occur particularly when worms have been treated with an anthelmintic that causes spasticity of the muscles.
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| − | *'''Extraluminal obstructions''':
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| − | **[[Pancreatitis|'''Pancreatitis''']], '''pancreatic abscess''' or '''neoplasm'''
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| − | **[[Biliary Tract Rupture|'''Biliary tract rupture''']]
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| − | **'''Pyloric''' or '''duodenal mass'''
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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.
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| − | Obstructive icterus results in excessive conjugated bilirubin in the blood. Out of the three types of icterus, it causes the most elevated levels of bilirubin in the blood and the greatest discoloration of the tissues of the body.
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| − | ==Links==
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| − | Also see [[Bilirubin]].
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| − | {{Learning
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| − | |flashcards = [[Liver_Flashcards_-_Pathology|Liver Pathology Flashcards]]
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| − | |literature search = [http://www.cabdirect.org/search.html?q=title%3A%28icterus%29+OR+title%3A%28jaundice%29 Icterus publications]<br>[http://www.cabdirect.org/search.html?q=%28%28od%3A%28dogs%29%29%29+AND+%28%28title%3A%28icterus%29+OR+title%3A%28jaundice%29%29%29 Icterus in dogs publications]<br>
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| − | [http://www.cabdirect.org/search.html?q=%28%28od%3A%28cats%29%29%29+AND+%28%28title%3A%28icterus%29+OR+title%3A%28jaundice%29%29%29 Icterus in cats publications]<br>
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| − | [http://www.cabdirect.org/search.html?q=%28%28od%3A%28horses%29%29%29+AND+%28%28title%3A%28icterus%29+OR+title%3A%28jaundice%29%29%29 Icterus in horses publications]<br>
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| − | [http://www.cabdirect.org/search.html?q=%28%28od%3A%28cattle%29+OR+od%3A%28sheep%29+OR+od%3A%28goats%29+OR+od%3A%28pigs%29%29%29+AND+%28%28title%3A%28icterus%29+OR+title%3A%28jaundice%29%29%29 Icterus in farm animals publications]
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| − | |Vetstream = [https://www.vetstream.com/felis/Content/Disease/dis02694.asp Bile duct disease]
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| − | }}
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| − | ==References==
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| − | Gorman N (1998) '''Canine Medicine and Therapeutics''' ''Blackwell Sciences''
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| − | {{review}}
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| − | ==Webinars==
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| − | <rss max="10" highlight="none">https://www.thewebinarvet.com/internal-medicine/webinars/feed</rss>
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| | [[Category:Liver_-_General_Pathology]] | | [[Category:Liver_-_General_Pathology]] |
| − | [[Category:Liver Diseases - Cat]][[Category:Liver Diseases - Dog]][[Category:Donkey]][[Category:Liver Diseases - Horse]][[Category:Liver Diseases - Cattle]][[Category:Liver Diseases - Sheep]][[Category:Alimentary Diseases - Goat]]
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| − | [[Category:Expert Review]]
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