However, without recognition newborns do not enter the care pathway to prevent serious complications. It can be surprisingly hard to detect jaundice, especially in newborns with dark skin. Neonatal jaundice presents with yellow discolouration of a skin and mucous membranes. Thankfully, kernicterus is very rare in practice. In clinically practice, kernicterus is often used to describe the presence of acute or chronic bilirubin encephalopathy (see clinical features). Kernicterus is a pathological term, which describes the yellow staining of cerebral tissue, particularly in the deep grey matter of the brain due to bilirubin deposition. Therefore, if hyperbilirubinaemia is left untreated it can lead to devastating short and long-term complications. Unconjugated bilirubin is potentially toxic to neural tissue in newborns and able to cross the blood-brain barrier. Renal excretion: small proportion enters enterohepatic circulation and reabsorbed.Degradation to urobilinogen and subsequent excretion in faeces. Intestinal modification: further metabolism by bacteria.Biliary excretion: active excretion of bilirubin into bile.Mediated by enzyme glucuronosyltransferase. Addition of glucuronic acid: process known as glucuronidation.A small proportion is absorbed and excreted by the kidneys. It makes bilirubin more water soluble and thus allows excretion through the biliary system via bile. This involves processing unconjugated bilirubin in the liver into conjugated bilirubin (or direct bilirubin). This unconjugated bilirubin (or indirect bilirubin) is transported to the liver bound to albumin and undergoes conjugation. Biliverdin is subsequently converted to bilirubin by biliverdin reductase. Haemoglobin is initially broken down to biliverdin. Crigler-Najjar is more severe as it leads to a profound reduction or absence of the enzyme activity, whereas Gilbert’s has mildly reduced activity leading to a benign course.īilirubin is the breakdown product of haemoglobin, which is transferred to and processed by the liver. They cause an unconjugated hyperbilirubinaemia. They are both due to mutations within the UGT1A1 gene locus, which encodes glucuronosyltransferase. Gilbert and Crigler-Najjar syndrome are disorders of biliary conjugation, which is an important step in bilirubin metabolism that takes place in the liver. Obstruction (biliary): congenital obstruction and malformations (e.g.Inborn errors of metabolism: Gilbert syndrome, Crigler–Najjar syndrome.Haemolysis: blood group incompatibility (ABO, rhesus), glucose-6-phosphate deficiency (G6PD).Jaundice due to an underlying disorder is termed pathological jaundice. ‘Breastmilk jaundice’ is typically used to refer to a prolonged physiological jaundice in breastfed newborns. Factors associated with breastfed jaundice include decreased caloric intake, increased enterohepatic cycling and actual constituents of breastmilk. Newborns breastfed are more likely to develop physiological jaundice than bottle-fed. Metabolism, circulation and excretion of bilirubin: slower in neonatesīreastfeeding is closely linked with physiological jaundice.Due to higher turnover, bilirubin levels greater. Red blood cells: shorter lifespan in neonates.Key factors that predispose to physiological jaundice: Most cases appear at 2 days of age and subsequently decreases by day 10. There is no underlying cause, although it is more common in newborns who are breastfed for unknown reasons. This refers to the generally harmless jaundice, which occurs within the first few weeks of life. If neonatal jaundice extends beyond 14 days of life, we call it prolonged jaundice. It may coexist with physiological jaundice. Pathological jaundice refers to a wide range of causes, some more severe than others. The majority of cases occur secondary to physiological jaundice within the first weeks of life. There are multiple causes of neonatal jaundice. Neonatal jaundice is most commonly due to ‘physiological’ jaundice, which occurs within the first weeks of life.
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