What is hyperbilirubinemia

Bilirubin is a very important indicator clinically. It is necessary to test bilirubin when checking our liver function. It is the waste product after the metabolism of hemoglobin in red blood cells in the blood. When bilirubin exceeds the standard, hyperbilirubinemia will occur. Once this happens, it may indicate that you have a liver disease. So, what is hyperbilirubinemia? Let’s take a closer look below.

Bilirubin is a waste product of the metabolism of hemoglobin in red blood cells in the blood. It is mainly converted from hemoglobin. One gram of hemoglobin can produce 34 mg of bilirubin. When red blood cells age (the life cycle of red blood cells is 120 days), they are broken down by the spleen to produce bilirubin. The bilirubin is then processed by the liver and excreted through the bile duct into the duodenum. Finally, most of it is excreted from the body with feces. A normal person produces 250 to 350 mg of bilirubin per day, of which 80% to 85% comes from aging red blood cells in the blood circulation, and the remaining 15% to 20% comes from the bone marrow and liver, which is called bypass bilirubin. Bilirubin is a waste product for the body. When the bilirubin level in serum is too high, it reveals abnormal information such as liver disease or bile duct obstruction. The high or low serum bilirubin value represents the severity of the abnormality. Generally speaking, direct bilirubin (Bilirubin Direct) below 0.5mg/dl and total bilirubin (Bilirubin Total) below 1.3mg/dl are within the normal range. Bilirubin is an important basis for clinical diagnosis of jaundice and an important indicator of liver function. The normal serum total bilirubin concentration is 1.7-17.1 μmol/L, with one-minute bilirubin below 3.4 μmol/L.

When bilirubin exceeds normal levels, it is called high bilirubin (hyperbilirubinemia). When the total bilirubin is at 34μmol/L, jaundice can be detected clinically; if the serum total bilirubin exceeds the normal range but jaundice is not visible to the naked eye, it is called latent jaundice. Jaundice is most commonly caused by hepatobiliary diseases, but it may also occur in other systemic diseases.

Clinical manifestations

1. Hemolytic jaundice

When a large number of red blood cells are destroyed (hemolysis), excessive unconjugated bilirubin is produced, which exceeds the capacity of liver cells to absorb, bind and excrete, causing unconjugated bilirubin to be retained in the blood and jaundice to occur. feature:

(1) Mild scleral jaundice, fever, back pain, and obvious paleness of the skin and mucous membranes during acute attacks (hemolytic crisis);

(2) No itching of the skin;

(3) Splenomegaly;

(4) There are signs of vigorous bone marrow hyperplasia, such as an increase in peripheral blood reticulocytes, the appearance of nucleated red blood cells, and active proliferation of the bone marrow erythrocyte system;

(5) Increased serum total bilirubin, generally not exceeding 85 μmol/L, mainly due to increased unconjugated bilirubin;

(6) The amount of urobilinogen in the urine increases but there is no bilirubin. In acute attacks, there is hemoglobinuria. In chronic hemolysis, the amount of hemosiderin in the urine increases.

2. Hepatocellular jaundice

Due to liver cell lesions, the uptake, conjugation and excretion of bilirubin are impaired, resulting in a considerable amount of unconjugated bilirubin retained in the blood. At the same time, due to liver cell damage and (or) destruction of the liver lobule structure, conjugated bilirubin cannot be discharged into the small bile ducts normally, and refluxes into the hepatic lymph and blood, resulting in jaundice. feature:

(1) The skin and sclera are light yellow to dark golden yellow, and the skin sometimes itches;

(2) Both unconjugated and conjugated bilirubin in the blood increase;

(3) Bilirubin in urine is positive and urobilinogen is often increased, but at the peak of the disease, urobilinogen is reduced or absent due to intrahepatic bile stasis;

(4) Serum transaminase is significantly elevated;

(5) Hepatitis virus markers in the blood are often positive;

(6) Liver biopsy is important for the diagnosis of diffuse liver disease.

3. Cholestatic jaundice

Intrahepatic cholestasis refers to the decrease in bile production and secretion, as well as the stagnation and concentration of bile from a molecular and cellular perspective. Intrahepatic cholestasis may occur alone or simultaneously with liver parenchymal damage. feature:

(1) Dark yellow, yellow-green or green-brown skin color;

(2) Significant skin itching, which often occurs before jaundice appears;

(3) Increased blood bilirubin, mainly conjugated bilirubin, and a direct reaction in the bilirubin qualitative test;

(4) Urine bilirubin is positive, but urobilinogen is reduced or absent;

(5) The amount of urobilinogen in the stool is reduced or absent, and the stool is light gray or clay-colored;

(6) Increased serum total cholesterol, alkaline phosphatase, and γ-glutamyl transpeptidase, and lipoprotein-X is positive.

4. Congenital non-hemolytic jaundice

(1) Gilbert syndrome is caused by impaired free bilirubin uptake by hepatocytes and insufficient glucuronyl transferase in the microsomes. Unconjugated bilirubin in serum was elevated, liver function tests were normal, red blood cell fragility was normal, gallbladder was well visualized, and liver biopsy was normal.

(2) Dubin-Johnson syndrome is caused by the obstruction of hepatocytes in excreting conjugated bilirubin and other organic anions (indocyanine green, X-ray contrast agents) into the bile duct capillaries, resulting in increased serum conjugated bilirubin, but normal bilirubin uptake and conjugation. The gallbladder is often not visualized with oral cholecystography. The liver appears green-black (black liver), and liver biopsy reveals diffuse brown pigment granules (melanin or adrenaline metabolite polymers) in the hepatocytes.

(3) Rotor syndrome is caused by congenital defects in the uptake of free bilirubin and excretion of conjugated bilirubin by hepatocytes, resulting in increased conjugated bilirubin in the blood and decreased indocyanine green (ICG) excretion test. Most cholecystography shows good imaging, but some shows no imaging. Liver biopsy was normal with no pigment granules in the hepatocytes.

(4) Crigler-Najjar syndrome is caused by the lack of glucuronyl transferase in liver cells, which results in the inability to form conjugated bilirubin. As a result, the concentration of unconjugated bilirubin in the blood is very high, which may be complicated by kernicterus. The prognosis is very poor.