The 59-year-old elephant lost her appetite last month and showed signs of lethargy, and tests revealed a low red blood cell count. Veterinarians performed an ultrasound exam Wednesday and found excessive blood and a clot in Ambika's reproductive tract — likely caused by a ruptured vessel.
"It's potentially very serious, but today she's doing very well," said Suzan Murray, the zoo's chief veterinarian.
The blood clot did not pose an immediate danger and could be serving as a "bandage" for the ruptured vessel, zoo officials said.
Ambika's appetite and behavior have returned to normal over the past week, and her red blood cell count had returned to near-normal levels, Murray said.
The cause of the bleeding and clot is not clear. But Murray said it may be due to age-related changes within Ambika's reproductive tract, such as endometriosis or fibroid tumors, which are common in older elephants that have never given birth.
"Trying to figure out what's going on inside of an elephant is like trying to figure out what's going on inside of a big gray box," Murray said. "There aren't many tools or techniques that we have to look deep inside."
Several zoo departments are working together to help treat Ambika. They plan to monitor for any changes in blood and urine samples at least weekly. Another treatment option may be hormone-modifying medication to help reduce the risk of further bleeding.
Ambika came to the National Zoo from India in 1961 after working in a logging camp, said zoo spokeswoman Peper Long. She was a gift from the children of India. The zoo has two other elephants.
Zoo elephants typically live into their mid to late 50s. Murray said not enough is known about how long elephants live in the wild.