Jaundice is a symptom complex which is characterized by yellow coloration of tissues and body fluids due to an increase in bile pigment bilrubin and related products.
For understanding causes of jaundice, first we need to learn about metabolism of bilirubin.
Jaundice is also known as icterus.
Hemoglobin released by breakdown of aged cells is broken down into globin and heme. The heme is further broken into iron and bilirubin. Bilirubin attaches to serum albumin and is transported to the liver where it is taken up.
In the liver, bilirubin is separated from albumin and conjugated to glucuronide by glucuronyl transferase. The conjugated bilirubin is water soluble and can be excreted by kidneys.
The conjugated bilirubin is excreted through the bile canaliculi and reaches the intestines where it is converted to stercobilinogen and urobilinogen by the intestinal bacteria. About 70% of this is absorbed in the colon and brought back to the liver and re-excreted (enterohepatic circulation). Unabsorbed stercobilinogen gives brown color to the faces.
Circulating urobilinogen is carried to the kidneys for excretion in the urine as urobilinogen.
Why does Jaundice Occur?
A disease or process which causes increase in bilirubin levels would result in jaundice. Hyperbilirubinemia may arise due to
- Increased bile pigment load to the liver.
- Affection of bilirubin diffusion into the liver cells.
- Defective conjugation.
- Defective excretion.
Normal values of bilirubin are
- Total bilirubin – 1 mg%
- Direct bilirubin – : 0.25 mg%
- Urinary bilirubin is present if direct bilirubin is greater than 0.4 mg% in serum.
- Urine Urobilinogen – 100-200 mg/day
- Fecal stercobilinogen – 300 mg/day
High concentration of bilirubin (hyperbilirubinemia), the bile product and its congeners are responsible for yellow discoloratrion of skin in jaundice. They bind with circulating proteins.
Bilirubin has more affinity for nervous tissue like basal ganglia and elastic tissues such as skin, sclera and blood vessels.
Causes of Jaundice
- Viral hepatitis
- Weil’s disease (Leptospirosis)
- Anesthetic agents: Halothane, chloroform
- Anticoagulants: Phenindione
- Anti-tuberculous drugs: Rifampicin, P.A.S., I.N.H., Thiacetazone
- Metals: Arsenic, mercury, gold, bismuth
- Chemicals: DDT
- X-ray irradiations
- Portal Hypertension
- Biliary cirrhosis
Extra Hepatic Obstruction
- Acute cholecystitis
- Carcinoma of the head of the pancreas
- Neoplasm of bile ducts, gall bladder and ampulla of Vater
- Congenital: Biliary atresia
Intra Hepatic Obstruction
- Cholestatic phase of infective hepatitis
- Drugs – Steroids, chlorpromazine, PAS, sulfonamides, chlorpropamide tolbutamide, methyltestosterone
Hemolytic Causes of Jaundice
There is an increased destruction of red blood cells which causes increase in production of bilirubin. This may occur due to
- Infections like Malaria, Clostridium welchi
- Drugs like L. Methyldopa, quinine, phenacetin, sulfonamides
- Poisons as in: Snake Venom, Favism
- Mismatched blood-tranfusion
- Paroxysmal Cold Hemoglobinuria
- Systemic lupus erythematosis
- Gilbert’s syndrome
- Crigler-Najjar syndrome
- Dubin Johnson syndrome
- Rotor’s syndrome.