Difference between revisions of "Icterus"

Latest revision as of 15:40, 4 January 2023

Also known as: Jaundice

Introduction

Image of a jaundiced cat, note the discoloured pinnae
(Image source Sabar 2007, Wikimedia Commons)

Icterus refers to the staining of tissues by 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 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 of Icterus

Pre-hepatic Jaundice

Also sometimes called Haemolytic Icterus. This condition results from increased red blood cell destruction, overwhelming the capacity of the 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 kidney. Possible causes of haemolysis and prehepatic jaundice include:

Haemolytic bacteria, including Clostridium haemolyticum in cattle and Leptospires in various species.
Haemolytic parasites, including Babesiosis in cattle and dogs and Mycoplasma haemofelis in cats.
Immune reactions to red blood cells, including:
- 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.
- Autoimmune haemolytic anaemia or immune-mediated haemolytic anaemia.
- Destruction of red blood cells of lambs fed with bovine colostrum.
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.
Inherited defects of red blood cell enzymes, including phosphofructokinase and pyruvate kinase.
Microangiopathic damage to red blood cells as they pass through narrow or damaged blood vessels, as in haemangiosarcomata, disseminated intravascular coagulation (DIC) or vasculitis.
Oxidative damage to red blood cells, caused by paracetamol in cats, onion poisoning in dogs and 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.

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.

Hepatic Jaundice

Also referred to as Toxic Icterus. Liver cell damage may lead to jaundice by two main mechanisms:

In acute hepatic necrosis and 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.
In chronic 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.
In reality, these situations occur together. There is both excessive unconjugated and conjugated bilirubin in the blood.
Examples:
- Leptospira icterohaemorrhagica in the dog.
- Rift Valley fever virus.
- Some plant poisonings (Lantana)
- Some fungal infections (Aflatoxicosis)

Post-hepatic Jaundice

Also called Obstructive Icterus. This occurs due to an 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:

Intraluminal obstructions:
- 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.
- Gall bladder mucoceles produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
- Biliary neoplasia, most commonly cholangiocellular cystadenoma (in cats) or carcinoma (in dogs).
- 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.
Extraluminal obstructions:
- Pancreatitis, pancreatic abscess or neoplasm
- Biliary tract rupture
- Pyloric or duodenal mass

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.

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.

Links

Also see Bilirubin.

Icterus Learning Resources
Vetstream To reach the Vetstream content, please select	Canis, Felis, Lapis or Equis
Flashcards Test your knowledge using flashcard type questions	Liver Pathology Flashcards
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Icterus publications Icterus in dogs publications Icterus in cats publications Icterus in horses publications Icterus in farm animals publications

References

Gorman N (1998) Canine Medicine and Therapeutics Blackwell Sciences

Webinars

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@@ Line 1: / Line 1: @@
-==Description==
-Icterus refers to the staining of tissues by 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 slcera and mucous membranes in life and in the tunica intima of the aorta at post mortem examination.
-Bilirubin is a pigment of red blood cells which is released into plasma cells when these cells are degraded in the '''monocytic phagocyte system (MPS)'''.  This '''unconjugated''' bilirubin is transported in plasma bound to albumin and taken up into hepatocytes where it is conjugated with glucuronic acid.  The resultant '''conjugated''' bilirubin is secreted into bile which then moves into the small intestine.  The conjugated bilirubin is degraded to '''urobilinogen''' by gastro-intestinal bacteria and a small proportion of this product is reabsorbed and excreted in the urine.  The remaining urobilinogen is further degraded to '''stercobilin''', a brown pigment which contributes to the colour of faeces.  Therefore, in animals with complete biliary obstruction, urobilinogen is absent from the urine and the faeces have a white/grey 'acholic' colour due to the absence of stercobilin.  Small quantities of conjugated bilirubin are found in the urine of normal dogs because it has a low renal threshold.
+Also known as: '''''Jaundice
+==Introduction==
+[[File:Jaundiced cat.jpg|thumb|right|Image of a jaundiced cat, note the discoloured pinnae<br><small>(Image source Sabar 2007, Wikimedia Commons)</small>]]
+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 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.
@@ Line 8: / Line 10: @@
 ==Causes of Icterus==
 ===Pre-hepatic Jaundice===
-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 - Anatomy & Physiology|kidney]].  Possible causes of haemolysis and prehepatic jaundice include:
+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:
-*'''Haemolytic bacteria''', including ''Clostridium haemolyticum'' in cattle and '''Leptospires''' in various species.
+*'''Haemolytic bacteria''', including ''[[Clostridium haemolyticum]]'' in cattle and [[Leptospira|'''Leptospires''']] in various species.
-*'''Haemolytic parasites''', including '''Babesiosis''' in cattle and dogs and ''Mycoplasma haemofelis'' in cats.
+*'''Haemolytic parasites''', including '''[[Babesia|Babesiosis]]''' in cattle and dogs and ''[[Feline Infectious Anaemia|Mycoplasma haemofelis]]'' in cats.
 *'''Immune reactions''' to red blood cells, including:
-**'''Neonatal isoerthryolysis''', resulting from the production of antibodies by the dam which are ingested by the neonate in colsotrum 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'''.
+**[[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'''.
-**'''Autoimmune haemolytic anaemia''' or '''immune-mediated haemolytic anaemia'''.
+**'''Autoimmune haemolytic anaemia''' or [[Immune Mediated Haemolytic Anaemia|'''immune-mediated haemolytic anaemia''']].
 **Destruction of red blood cells of '''lambs fed with bovine colostrum'''.
 *'''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'''.
 *'''Inherited defects of red blood cell enzymes''', including phosphofructokinase and pyruvate kinase.
-*'''Microangiopathic damage''' to red blood cells as they pass through narrow or damaged blood vessels, as in '''haemangiosarcomata''', '''disseminated intravascular coagulation (DIC)''' or '''vasculitis'''.
+*'''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]]'''.
-*'''Oxidative damage''' to red blood cells, caused by '''paracetamol''' in cats, '''onion poisoning''' in dogs and '''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.
+*'''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.
 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.
 ===Hepatic Jaundice===
-[[Liver - Anatomy & Physiology|Liver]] cell damage may lead to jaundice by two main mechanisms:
+Also referred to as '''Toxic Icterus'''. [[Liver - Anatomy & Physiology|Liver]] cell damage may lead to jaundice by two main mechanisms:
-*In '''acute hepatic necrosis''' and '''hepatic lipidosis''', damaged cells swell to such a degree that flow of bile in the canaliculi is obstructed.
+*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.
-*In '''chronic 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.
+*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.
+* 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|Rift Valley fever virus]].
+** Some plant poisonings (''Lantana'')
+** Some fungal infections ([[Mycotoxins|Aflatoxicosis]])
 ===Post-hepatic Jaundice===
-This occurs due to an 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:
+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:
 *'''Intraluminal obstructions''':
-**'''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.
+**'''[[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.
-**'''Gall bladder mucocoeles''' produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
+**'''Gall bladder mucoceles''' produce a kiwi sign on radiographs and may be a sequel to cystic mucinous hyperplasia of the gall bladder mucosa.
-**'''Biliary neoplasia''', most commonly cholangiocellular adenoma (in cats) or carcinoma (in dogs).
+**'''Biliary neoplasia''', most commonly cholangiocellular cystadenoma (in cats) or carcinoma (in dogs).
+**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.
 *'''Extraluminal obstructions''':
-**'''Pancreatitis''', '''pancreatic abcess''' or '''neoplasm'''
+**[[Pancreatitis|'''Pancreatitis''']], '''pancreatic abscess''' or '''neoplasm'''
-**'''Biliary tract rupture'''
+**[[Biliary Tract Rupture|'''Biliary tract rupture''']]
 **'''Pyloric''' or '''duodenal mass'''
 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.
+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.
+==Links==
+Also see [[Bilirubin]].
+{{Learning
+|flashcards = [[Liver_Flashcards_-_Pathology|Liver Pathology Flashcards]]
+|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>
+[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>
+[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>
+[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]
+|Vetstream = [https://www.vetstream.com/felis/Content/Disease/dis02694.asp Bile duct disease]
+}}
 ==References==
@@ Line 44: / Line 68: @@
+{{review}}
+==Webinars==
+<rss max="10" highlight="none">https://www.thewebinarvet.com/internal-medicine/webinars/feed</rss>
 [[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]]
-[[Category:To_Do_-_James]]
+[[Category:Expert Review]]