Bilious output refers to bile, a yellow-green fluid produced by the liver and stored in the gallbladder. The color of bile can provide important clues about health and disease. In this article, we will examine the normal and abnormal colors of bile and what they may indicate.
What is Bile?
Bile is a digestive fluid produced continuously by the liver and stored in the gallbladder. It contains water, electrolytes, bile acids, cholesterol, phospholipids, and bilirubin. The main functions of bile include:
- Emulsifying fats – bile breaks down large fat droplets into smaller droplets so they can be digested
- Neutralizing stomach acid – bile contains bicarbonate which helps neutralize acidic chyme from the stomach
- Excreting bilirubin – a waste product from old red blood cells
- Excreting cholesterol – bile salts help remove excess cholesterol from the body
Bile flows from the liver through the bile ducts and is stored in the gallbladder. After a meal, the gallbladder contracts and releases bile into the small intestine to aid in digestion. The color of bile is often used clinically as an indicator of health or disease.
Normal Color of Bile
Normal bile is yellow-green in color. The pigments that contribute to this color include:
- Bilirubin – a yellowish pigment from the breakdown of old red blood cells. It makes up about 10% of bile.
- Biliverdin – a greenish pigment that results from the metabolism of bilirubin. It makes up about 10% of bile.
- Cholesterol – white or pale yellow crystalline compounds that make up about 30% of bile.
- Bile salts – composed of bilirubin, biliverdin, and other ions that make bile water-soluble and appear green.
The normal yellow-green color of bile comes from the combination of these pigments. However, abnormalities in the liver, gallbladder, or bile ducts can alter bile production and change its color.
Abnormal Color of Bile
Changes in the color of bile can signify disease processes. Some abnormal colors of bile include:
| Color | Cause |
|---|---|
| Dark Yellow | Increased bilirubin due to conditions like cirrhosis or gallstones |
| Brown | Very high levels of bilirubin due to liver disorders |
| Gray or Chalky White | Thickened bile due to gallbladder disorders |
| Dark Green | Presence of bile pigments and iron in bile |
| Black or Red | Bleeding in the biliary system from ulcers, cancers, trauma |
Let’s examine some of the specific conditions that can alter the color of bile:
Increased Bilirubin
High levels of bilirubin turn bile darker yellow or brown. This is often seen with:
- Cirrhosis – liver scarring impairs bilirubin excretion
- Gallstones – can obstruct bile flow and cause bilirubin buildup
- Viral hepatitis – inflammation of the liver
- Cancer in the liver, bile ducts, or pancreas can compress bile ducts
Gallbladder Disorders
Blockage of the bile ducts from gallstones or cancer leads to thickened, chalky bile. Gallbladder inflammation can also cause thickened bile. Conditions include:
- Cholecystitis – inflammation of the gallbladder
- Cholangitis – inflammation of the bile ducts
- Gallstones – most common cause of duct obstruction
- Gallbladder cancer – rare cause of bile thickening
Liver Disease
Many liver disorders can alter bile pigmentation or consistency:
- Hepatitis – swelling and inflammation of the liver
- Cirrhosis – severe liver scarring
- Primary biliary cholangitis – autoimmune disorder damaging bile ducts
- Primary sclerosing cholangitis – chronic inflammation and scarring of bile ducts
Bleeding
Rarely, bleeding into the biliary system can turn bile black or reddish. Causes include:
- Bile duct ulcers
- Cancers in the liver, bile ducts, or pancreas
- Gallbladder trauma or surgery
Diagnosing Abnormal Bile Color
Changes in bile color are often first noticed during gallbladder surgery or when drainage tubes are placed during surgery. Diagnostic tests that allow direct visualization of bile to assess its color include:
- Abdominal ultrasound – uses sound waves to image the gallbladder and bile ducts
- ERCP (endoscopic retrograde cholangiopancreatography) – scope passed through the mouth into the small intestine to inject dye into the bile ducts. Can obtain bile samples.
- MRCP (magnetic resonance cholangiopancreatography) – MRI to image the biliary system.
- Percutaneous transhepatic cholangiography – dye injected through the skin into bile ducts, allowing x-ray visualization.
Blood tests can also suggest bile abnormalities by detecting high bilirubin levels or liver enzymes:
- Total/direct bilirubin – elevated in bile obstruction
- Alkaline phosphatase (ALP) – elevated with bile duct blockage
- Aminotransferases (ALT/AST) – elevated with hepatitis, cirrhosis, and other liver disorders
Treatment of Abnormal Bile Color
Treatment focuses on identifying and managing the underlying disorder leading to the abnormal bile color. This may include:
- Treating infections or inflammation of the liver or bile ducts with antibiotics or anti-inflammatory medications
- Relieving bile duct obstructions, often with ERCP
- Draining excess bile or infected bile from the gallbladder or bile ducts
- Controlling symptoms of itching with bile acid sequestrants, antihistamines, rifampin
- Managing cirrhosis complications
- Surgery to remove gallstones or cancers obstructing bile flow
In most cases, successful treatment of the underlying condition will resolve abnormal bile pigmentation. Close follow-up is necessary to monitor resolution of bile color changes.
Conclusion
The color of bile can provide important clues to hepatobiliary health. Normal bile is yellow-green, but may become darker with increased bilirubin, pale if thickened, or brown with severe liver disease. Reddish or black bile indicates bleeding. By recognizing abnormal bile colors, physicians can identify obstructed ducts, liver infections, cirrhosis, and cancers earlier – leading to quicker treatment. Analyzing bile color, along with imaging and lab tests, improves diagnosis and monitoring of many hepatobiliary conditions.
