What are "coffee grounds" in vomit indicative of?

The presence of "coffee grounds" in vomit is indicative of old blood. This appearance occurs when blood has been in the stomach long enough for it to be partially digested. The gastric acid breaks down the hemoglobin in red blood cells, resulting in a dark brown or black color resembling coffee grounds. This is often a sign of upper gastrointestinal bleeding, where the bleeding has been occurring over some time, allowing the blood to undergo these changes before being expelled through vomiting.

Fresh bleeding, in contrast, would present as bright red blood in the vomit, while food particles represent undigested material and gastric fluid would be more liquid without any altered blood components. Understanding these different clues can help in assessing the severity and potential causes of the underlying condition that may be causing the vomiting.