If the claimant did not immediately know they were injured, they get additional time to file a medical malpractice claim. While many injuries are immediately apparent, others can take time to discover. For example, health care providers leaving surgical tools or instruments inside the body cavity—while not something that happens constantly—is a relatively well-known type of medical negligence. Surgical sponges are the most common instrument left in the body cavity, and they tend to soak up blood and blend with the surrounding tissues. Surgeons can carelessly overlook them before they close up the patient. Unfortunately, because the patient's surgery has concluded and there is no way to easily see where the surgeon left the tool, they might not discover the injury unless it caused immediate problems. Otherwise, it would remain where it was left, slowly damaging the organ and resulting in symptoms that can take a while to figure out.