HealthTap, the doctor question and answer service that has recently been expanding into a care provider directory and referral network, has acquired the health business of Avvo, a Q&A website that connects users to lawyers and doctors, for an undisclosed amount.

HealthTap will add about 13,000 new doctors to its network, bringing its total to more than 30,000 physician users, CEO Ron Gutman told MobiHealthNews in an interview. It's not just the raw numbers that are exciting, he said, but the way the acquisition diversifies their base of physicians.

"We added more specialties, so it broadens our coverage and our reach," he said, adding that the move takes them from 115 specialties to 128. "What excites me most is the local aspect of it. We're gaining a much broader geographic coverage."

In addition to the network of physician users (which recently added a ranking system to its functionality), HealthTap has a directory of doctors and dentists around the country, as well as a database of which colleagues each doctor refers patients to. Last month, HealthTap launched its DocConnect system, which presents that referral data to patients in map form. The acquisition will bring the total number of doctors and dentists in that directory to 1.2 million, Gutman said.

"We’re in the process right now of matching the referral data we have to all the physicians in the directory," he said. "A good percentage of them we will be able to match, because we had referral data for more than just the doctors in our network. It’s a very, very extensive directory, so you can imagine it’s a huge data task." HealthTap estimated the number of network and referral connections at 30 million.

Avvo will continue to provide their legal answers service, which was their initial focus when they launched in 2007. They added their health section in November 2010.

"Avvo’s legal business is booming, and ... we’ve decided to focus 100 percent of our attention on expanding our consumer legal services and helping lawyers grow their business," Mark Britton, founder and CEO of Avvo, said in a statement. "Just as Avvo is the premier destination for people looking for legal advice, HealthTap is the leading source for trusted answers to health questions and peer-reviewed medical professionals, which makes HealthTap the right choice to carry on the conversation between consumers and medical professionals."

"I think they will continue doing well in legal," Gutman said of Avvo. "They were excited to sell and it was a quite a competitive deal."

Gutman told MobiHealthNews that although the client base was a key part of HealthTap's first acquisition, it's not the only thing HealthTap is gaining.

"We acquired the entire health section lock, stock, and barrel: the physicians in the network, all the questions and answers, all the data, connections between the doctors," he said.