Bile salts cause the itching
In obstructive jaundice, a stone in the common bile duct prevents bile from reaching the duodenum. Bile contains bile salts (bile acids), conjugated bilirubin, cholesterol, and other substances. When flow is blocked, these components back up into the liver and then into the bloodstream. Retained bile salts deposited in the skin cause the pruritus of obstructive jaundice. The itching can be intense, is often worse at night, and leads to scratching, broken skin, and poor sleep.
What bilirubin does and does not do
Conjugated bilirubin that spills into the blood gives the skin and sclerae their yellow color and, because it is water-soluble, is excreted in urine, making it dark. Lack of bilirubin reaching the gut leaves the stools pale or clay-colored. Bilirubin is therefore responsible for the color changes of jaundice, but it is not the cause of the itching. This distinction is a classic exam point: her four presenting features, jaundice, itching, dark urine, and pale stools, each have a specific mechanism.
| Finding | Cause |
|---|
| Yellow skin and sclerae | Conjugated bilirubin in blood and tissues |
| Itching (pruritus) | Bile salts deposited in the skin |
| Dark urine | Water-soluble conjugated bilirubin excreted by the kidneys |
| Pale stools | No bilirubin reaching the intestine |
Why the other substances are wrong
Urea accumulates in severe kidney failure and can crystallize on the skin as uremic frost; uremic pruritus is a kidney problem, not a biliary one. Ammonia accumulates in liver failure and crosses into the brain, causing hepatic encephalopathy with confusion and asterixis, not itching. Watch out! Conjugated bilirubin is tempting because it is the most familiar word linked to jaundice, but it explains the color, not the pruritus.
Nursing care for pruritus
Comfort measures include cool baths or tepid showers, mild soap, emollients, loose cotton clothing, a cool room, and keeping the nails short to reduce skin damage from scratching. Cholestyramine may be ordered; it binds bile salts in the intestine so they are excreted. The definitive treatment is relieving the obstruction, after which itching subsides. Key point! In obstructive jaundice, bilirubin causes the yellow color and bile salts cause the itch.