The presence of yellow eyes, medically termed scleral icterus, is the most visible symptom of jaundice, which is the overall yellowing of the skin and mucous membranes. Jaundice occurs when there is an excessive amount of a specific pigment circulating in the bloodstream, indicating a disruption in the body’s normal waste processing systems. It requires investigation by a healthcare professional to identify and address the root cause.
The Role of Bilirubin in Yellowing
The yellow color of jaundice comes from bilirubin, a byproduct of the natural recycling of red blood cells. As old red blood cells are broken down in the body, the hemoglobin they contain is converted into unconjugated, or indirect, bilirubin. This type of bilirubin is fat-soluble and travels through the bloodstream bound to a protein called albumin.
The liver takes this unconjugated bilirubin out of the blood and chemically modifies it through conjugation. This process makes the bilirubin water-soluble, creating conjugated, or direct, bilirubin. Once conjugated, the bilirubin can be excreted from the body as part of bile, which flows from the liver through the bile ducts into the small intestine.
The yellowing of the eyes and skin, or hyperbilirubinemia, happens when this process is overwhelmed or blocked. If bilirubin production is too high, the liver cannot process it effectively, or its exit pathway is obstructed, the pigment builds up in the blood. When serum bilirubin levels exceed approximately 3 milligrams per deciliter, the pigment begins to deposit in tissues, starting with the eyes, causing the distinct yellow tinge of jaundice.
Primary Medical Reasons for Jaundice
The causes of jaundice in adults are categorized based on where the disruption occurs along the bilirubin processing pathway.
Pre-hepatic Jaundice
Pre-hepatic jaundice occurs before the blood reaches the liver, generally due to an accelerated rate of red blood cell destruction, a process known as hemolysis. When red blood cells break down too quickly, the liver is overwhelmed by the massive amount of unconjugated bilirubin that needs processing. Conditions like hemolytic anemia or the reabsorption of a large hematoma can lead to this type of excessive bilirubin production.
Hepatic Jaundice
Hepatic jaundice involves damage or disease within the liver itself, compromising its ability to process bilirubin efficiently. This damage can result from viral infections, such as acute or chronic hepatitis, or from toxins like excessive alcohol consumption leading to alcoholic liver disease or cirrhosis. Genetic conditions, such as Gilbert’s syndrome, also fall into this category, where a mild enzyme deficiency slows the liver’s conjugation of bilirubin.
Post-hepatic Jaundice
Post-hepatic jaundice, also known as obstructive jaundice, happens after the bilirubin has been processed by the liver but cannot be excreted. This is caused by a physical blockage in the bile ducts that transport conjugated bilirubin to the intestine. The most common causes of this obstruction are gallstones that have lodged in the common bile duct, or inflammation of the pancreas, known as pancreatitis. Less commonly, this blockage can be due to tumors in the pancreas or bile ducts, which prevent the flow of bile out of the liver.
A Special Case: Yellowing in Newborns
Jaundice is common in newborn babies, affecting many full-term infants within their first week of life. This phenomenon, often called physiological jaundice, is usually temporary and due to the immaturity of the infant’s liver. A newborn’s liver enzymes, specifically those needed for bilirubin conjugation, are not fully developed and cannot process the pigment as quickly as an adult’s. Furthermore, newborns have a higher concentration and faster turnover of red blood cells compared to adults, which naturally increases the amount of bilirubin being produced.
While most cases resolve on their own, monitoring is necessary because very high levels of unconjugated bilirubin pose a risk. Unconjugated bilirubin is neurotoxic and can cross the blood-brain barrier, potentially causing kernicterus, a rare type of permanent brain damage.
When to Seek Medical Care
Any unexplained yellowing of the eyes or skin should prompt a visit to a healthcare provider for a medical evaluation. Jaundice requires professional assessment to determine the underlying disorder. The diagnostic process typically begins with a physical examination and blood tests to measure the total bilirubin level and to differentiate between unconjugated and conjugated bilirubin.
Immediate emergency medical care is necessary if the yellowing is accompanied by specific “red flag” symptoms. These include a high fever and chills, which suggest a possible infection in the bile ducts. The sudden onset of severe abdominal pain or a change in mental status, such as confusion, are also urgent indicators. Further testing, such as imaging procedures like an ultrasound or CT scan, may be used to look for blockages and assess the condition of the liver and associated organs.