PSPal Surgery

Why does the INR rise in obstructive jaundice?

And what it means when vitamin K brings it back down.

Written and clinically reviewed by , consultant minimally invasive and bariatric surgeon, Al-Makassed Hospital, Jerusalem, and Assistant Professor of Surgery, Al-Quds University. Last updated .

The short answer

Vitamin K is fat-soluble, so it can only be absorbed inside the bile acid micelles formed in the small intestine. In obstruction, bile acids never reach the gut, no micelles form, vitamin K is not absorbed, and the clotting factors that depend on it — II, VII, IX and X — fall. Factor VII has the shortest half-life, so the prothrombin time and INR rise first. Give vitamin K intravenously and, if the liver itself is healthy, the INR comes back down.

The chain of events

  1. A stone or tumour blocks the bile duct.
  2. Bile acids no longer reach the duodenum.
  3. Without bile acids above their critical concentration, no mixed micelles form.
  4. Fat and the fat-soluble vitamins A, D, E and K cannot cross the unstirred water layer to the brush border.
  5. Hepatic γ-carboxylation of factors II, VII, IX and X — which requires vitamin K — slows.
  6. Factor VII has a half-life of only about 4–6 hours, so it falls first, and the extrinsic pathway it drives is exactly what the prothrombin time measures. The INR rises.

This is a direct consequence of the physiology on the bile acid side of the book — micelles are what carry fat-soluble vitamins to the enterocyte.

The vitamin K response

Give 10 mg of vitamin K intravenously and repeat the INR after 12 to 24 hours.

If the INR corrects

This supports vitamin K deficiency from cholestasis. The hepatocytes can still manufacture clotting factors — they were simply short of the cofactor. The problem is in the duct, not the liver cell.

If the INR does not correct

This raises concern for impaired hepatic synthetic function. The liver cannot make the factors even when supplied with vitamin K, which points towards advanced parenchymal disease or acute liver failure.

Read it as a clue, not a verdict

The response to vitamin K is a useful bedside discriminator, not an absolute test. Correction can be partial, patients often have more than one problem at once, and sepsis, antibiotics, malnutrition and poor oral intake all contribute to vitamin K deficiency independently of the bile duct.

Why it matters practically

  • Correct the INR before any procedure. ERCP with sphincterotomy, percutaneous transhepatic cholangiography and surgery all carry a bleeding risk in a coagulopathic, jaundiced patient.
  • Protect the kidneys at the same time. Jaundiced patients are prone to acute kidney injury: give intravenous fluids, monitor urine output, and avoid NSAIDs, aminoglycosides and unnecessary contrast.
  • Watch the trend. In acute hepatitis, a rising INR with a falling ALT is a warning sign, not reassurance.

The same mechanism, other consequences

Vitamin K is only one of four. The same missing micelles mean vitamin A (night vision), vitamin D (bone) and vitamin E are all poorly absorbed in prolonged cholestasis, and undigested fat appears in the stool as steatorrhoea — greasy, pale and difficult to flush.

Related pages

PhysiologyEmulsification vs micellesWhy micelles are what matter for vitamin absorption.MechanismPale stools and dark urineThe other consequence of bile not reaching the gut.InterpretationReading liver function testsWhere the INR fits among the others.OverviewThe three types of jaundiceWhere the block is.