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Xanthochromia is a clinical sign usually indicative of subarachnoid hemorrhage, a type of bleeding that occurs inside the brain. In patients with xanthochromia, the cerebrospinal fluid is yellowish in color because it contains bilirubin, a pigment generated during the breakdown of red blood cells. This can be physically visible in a sample, although techniques like spectrophotometry are usually used to quantify the results, ensuring that a diagnosis is not missed and providing information about how much yellow pigment is present in the fluid sample. These lab tests can be performed in a lab on site or the sample may be sent to another location if a hospital or clinic contracts out lab services.
Samples of cerebrospinal fluid are taken using a technique known as a spinal tap, where a needle is inserted into the spinal canal and used to withdraw a small sample of fluid. Trauma during a spinal tap can cause blood to appear in the cerebrospinal fluid, but notably, the fluid will be reddish, not yellow, because the enzymes in the body have not yet had a chance to break down the blood cells. If a sample is yellowish with xanthochromia, it means that blood has been present in the spinal canal long enough for it to break down into components like bilirubin.
Lab testing has shown that red blood cells can break down remarkably quickly, causing bilirubin to appear shortly after a hemorrhage develops. One thing practitioners have to consider when a patient requires multiple spinal taps is that xanthochromia could be the result of a hemorrhage, or may be caused by trauma during a prior spinal tap. The patient's history must be considered in such situations and doctors may also use medical imaging studies to look for other signs of hemorrhage along the brain and spinal cord.
The term "xanthochromia" is also used more generally in reference to patches of yellow discoloration on the skin. These are also caused by the breakdown of blood and release of bilirubin. As many people have noticed while watching bruises heal, initial deposits of blood are blue to red, and they fade to yellowish-brown over time as the body breaks down the blood cells. Eventually, the bilirubin will also be carried away and expressed by the body. Bilirubin is also the culprit behind jaundice, a yellowish discolouring of the eyes and skin seen in people with liver disease whose bodies cannot eliminate the yellow pigment.