Yellowing of the white part of the eyes (sclera) is medically known as scleral icterus or jaundice. This discoloration is a visible symptom, not a disease itself, indicating an underlying medical issue that requires prompt investigation. The yellow hue is caused by the accumulation of bilirubin, a yellow-orange pigment, in the bloodstream and tissues. Since the body normally keeps bilirubin levels low, its buildup signals a disruption in the metabolic pathway.
Understanding Bilirubin and Scleral Yellowing
Bilirubin is a natural byproduct of recycling old or damaged red blood cells, which are broken down primarily in the spleen and liver. During this process, the heme component of hemoglobin is converted into unconjugated bilirubin. This unconjugated form is water-insoluble and must be bound to the protein albumin to travel through the blood to the liver.
Once in the liver cells, an enzyme attaches glucuronic acid to the bilirubin, a process called conjugation. This step makes the bilirubin water-soluble, changing it into conjugated bilirubin, which is ready for excretion. Conjugated bilirubin is a major component of bile, which the liver secretes into the small intestine to aid in digestion and is then eliminated through the stool.
Causes Originating from Liver Disease and Bile Obstruction
When the liver is damaged or the bile drainage system is blocked, the normal excretion of conjugated bilirubin is impaired, leading to its accumulation in the blood. This category of causes can be split into hepatic (liver cell dysfunction) and post-hepatic (bile duct obstruction) issues. Damage to the liver cells can be caused by conditions such as acute hepatitis, which may stem from viral infections (Hepatitis A, B, or C) or severe alcohol consumption.
Chronic liver diseases, including cirrhosis, involve long-term scarring that progressively reduces the liver’s ability to process and excrete bilirubin. Non-alcoholic fatty liver disease, often associated with obesity and metabolic syndrome, is an increasingly common source of chronic liver injury that can eventually lead to jaundice. Certain medications, like excessive doses of acetaminophen or some prescription drugs, can also cause liver toxicity and impair bilirubin processing.
Jaundice can also result from a physical blockage preventing bile, which contains conjugated bilirubin, from flowing out of the liver into the intestine. The most frequent cause of this obstructive (post-hepatic) jaundice is the migration of gallstones into the common bile duct. This blockage causes bile to back up into the liver and subsequently into the bloodstream.
Other forms of bile obstruction include tumors, particularly those arising in the pancreas, bile ducts (cholangiocarcinoma), or the gallbladder. Inflammation of the bile ducts (cholangitis) or chronic pancreatitis can also narrow the ducts and impede bile flow. Gallstone obstruction often causes severe, sudden abdominal pain, while tumor-related obstruction can be painless, allowing jaundice to progress unnoticed.
Causes Stemming from Blood Cell Breakdown
The excessive destruction of red blood cells, occurring before the bilirubin reaches the liver, is known as pre-hepatic or hemolytic jaundice. This condition overwhelms the liver’s capacity to conjugate the massive influx of unconjugated bilirubin. Conditions causing this rapid destruction are collectively known as hemolytic anemias.
Inherited disorders like sickle cell disease and thalassemia cause the production of abnormally shaped or fragile red blood cells that are prematurely destroyed. Enzyme deficiencies, such as Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, also make red blood cells susceptible to destruction when exposed to certain drugs or infections. Autoimmune hemolytic anemia occurs when the body’s immune system mistakenly attacks and destroys its own red blood cells. Certain infections like malaria or reactions to blood transfusions can also trigger massive hemolysis.
Not all yellowing is due to bilirubin. Carotenemia, caused by consuming excessive amounts of beta-carotene-rich foods like carrots or squash, can turn the skin yellow or orange. However, carotenemia typically spares the sclera, which remains white, making it easy to differentiate from true jaundice.
When Immediate Medical Attention is Necessary
Any yellowing of the sclera is an abnormal finding requiring medical consultation to identify the underlying cause. Jaundice should never be ignored, as it can signal a serious issue with the liver, gallbladder, or blood.
Certain accompanying symptoms act as “red flags” and indicate a need for immediate emergency care. These include a sudden onset of high fever and chills, suggesting a serious infection like cholangitis in the bile ducts. Severe, unrelenting abdominal pain, particularly in the upper right quadrant, could indicate an acute obstruction caused by gallstones or acute pancreatitis.
Other urgent symptoms include mental changes such as confusion or excessive drowsiness, which can be a sign of advanced liver failure affecting brain function. The presence of unusually dark urine and pale, clay-colored stools strongly suggests a complete blockage of the bile duct, preventing the normal excretion of bilirubin. Seeking prompt medical evaluation is the only way to determine the cause of the bilirubin buildup and begin appropriate treatment.