The appearance of a yellowish tint in the white part of the eyes, known as icterus or, more generally, jaundice, can be disconcerting. This color change is not a disease itself but a visible symptom signaling an underlying biological process is not functioning correctly. This yellowing indicates an accumulation of a specific substance in the bloodstream, which then deposits in tissues like the skin and eyes. Understanding the mechanism behind this symptom is the first step toward identifying the cause.
Understanding Bilirubin and the Color Change
The yellow discoloration is caused by the buildup of bilirubin, a pigment that is a byproduct of the normal recycling of old red blood cells. When red blood cells break down, their hemoglobin is converted into this yellowish compound. This initial form, called unconjugated bilirubin, is not water-soluble and must be transported through the blood, typically bound to albumin. The liver takes up this unconjugated bilirubin, modifies it to become water-soluble (conjugated bilirubin), and prepares it for excretion. When the concentration of bilirubin in the blood (hyperbilirubinemia) reaches approximately 2 to 3 milligrams per deciliter, the yellow color becomes noticeable, often beginning in the eyes.
Causes Originating from Blood Cell Breakdown
One category of causes occurs before the liver processes bilirubin, often called pre-hepatic jaundice. These conditions involve the rapid or excessive destruction of red blood cells, a process known as hemolysis. The volume of bilirubin produced overwhelms the liver’s capacity to process and excrete the pigment quickly enough.
Specific conditions causing this high rate of breakdown include inherited disorders like sickle-cell anemia or thalassemia, where red blood cells are prone to premature destruction. Enzyme deficiencies, such as Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, can also lead to sudden episodes of hemolysis. In these cases, the liver may be healthy, but it cannot keep pace with the influx of unconjugated bilirubin.
Causes Related to Liver Function
A second major group of causes involves issues that occur within the liver itself, preventing the organ from performing its processing function. This is known as hepatic jaundice, resulting from damage to the liver cells (hepatocytes) responsible for conjugating bilirubin. If these cells are damaged, they cannot efficiently transform unconjugated bilirubin into its water-soluble, excretable form.
Liver Damage and Disease
Acute viral hepatitis (A, B, or C) is a common example where liver inflammation impairs bilirubin metabolism, often accompanied by nausea and fatigue. Chronic liver diseases, such as cirrhosis, severely limit the liver’s ability to process bilirubin. Cirrhosis involves scarring where healthy tissue is replaced by non-functional scar tissue, often resulting from long-term alcohol use or chronic viral hepatitis.
Genetic and Drug-Induced Causes
Genetic conditions like Gilbert’s syndrome also fall into this category, characterized by a reduced efficiency of the enzyme responsible for conjugating bilirubin, leading to mild, intermittent yellowing. Certain medications or toxins can similarly cause drug-induced liver injury, disrupting the function of the hepatocytes.
Causes Related to Blocked Bile Ducts
The third category, post-hepatic or obstructive jaundice, involves a blockage after the liver has successfully processed the bilirubin. Conjugated, water-soluble bilirubin is meant to be excreted in bile, which drains from the liver through bile ducts into the small intestine. When this drainage pathway is physically obstructed, the bile is forced back into the bloodstream, leading to hyperbilirubinemia.
The most frequent cause of this obstruction is gallstones lodged in the common bile duct. Inflammation and infection of the bile ducts, known as cholangitis, can also create a blockage, often presenting with fever and abdominal pain. More serious causes include tumors originating in the pancreas or the bile ducts themselves, which compress the ducts and prevent bile flow. A key sign of this obstruction is often pale or clay-colored stools, because bilirubin cannot reach the intestine to provide its normal brown color.
When Immediate Medical Attention is Necessary
Any instance of yellowing of the eyes or skin should prompt a medical evaluation, as it is never a normal state for an adult. A medical professional will perform blood tests to measure the total bilirubin level and determine the ratio of unconjugated to conjugated bilirubin, which helps pinpoint the area causing the issue. Treatment depends entirely on the underlying cause, ranging from addressing a blood disorder to treating liver inflammation or surgically removing an obstruction.
Emergency medical attention is necessary if the yellowing is accompanied by severe symptoms. These signs include high fever, significant abdominal pain, sudden mental confusion, or lethargy, which can suggest a serious infection or advanced liver failure. Additionally, very dark urine or extremely pale, clay-colored stools alongside jaundice indicates a potentially severe and urgent blockage requiring prompt diagnosis.