Ever since the FDA stopped making doctors seek approval to perform fecal transplants on Clostridium difficile patients (C. difficile) in early 2013, the procedure has become more widely accepted. The method, which involves introducing fecal matter from a healthy donor into the gut of an unhealthy donor, has a 90 percent success rate, so its increasing popularity should come as no surprise. Perhaps more surprising is that, until now, few researchers have tried to freeze donated stool to see if it works as well as the fresh kind. Fortunately, a group of researchers at the Massachusetts General Hospital have given it the old clinical study try. And — lo and behold — frozen poo works, too.

C. difficile is a serious infection that kills 14,000 people in the US each year. Symptoms can range from diarrhea to serious inflammation of the colon. And unfortunately, 30 percent of patients experience recurrent infections. Treating the infection with antibiotics can work, but there's always a chance that these medications could make the infection worse by killing off healthy gut bacteria. Doctors have turned to fecal matter to cure C. difficile infections because it's thought that stool transplants help restore healthy microbes in a patient's gut. But the procedure has one major drawback: it's pretty time sensitive.

It's pretty time sensitive

Elizabeth Hohmann,  an infectious disease expert at the Massachusetts General Hospital who worked on the study, published today in the journal Clinical Infectious Diseases, explained in an email to The Verge that "we like to treat patients for at least four days with vancomycin — an antibiotic — at the time of [C. difficile] relapse." After these four days, the physicians stop the vancomycin treatment for a short period and then proceed with the transplant. This, Hohmann said, can be a "challenging time frame for a patient to 'find their own donor' and get that person tested."

People can't eat allergens in the days leading up to the donation

Furthermore, if a donor has eaten common allergens — such as nuts and eggs — in the days prior to the donation, their fecal matter won't be suitable for some patients. In short, the whole process can end up taking much longer than it should, which can compromise the treatment's effectiveness. Freezing donations could therefore provide physicians with more flexibility. As the study shows, frozen, prescreened fecal matter from a donor who is unrelated to a patient is just as effective in curing recurrent C. difficile infections as a fresh stool sample.

In the experiment, doctors obtained fecal matter from what the researchers called "exceptionally healthy adults" who refrained from eating common allergens in the days leading up to donation. The feces were then filtered and diluted before being screened for hazardous microbes and frozen. Finally, researchers re-tested the donors in the four weeks following the donation to make sure that they didn't have any hidden infections at the time of the screening.

20 patients received thawed donations

Once the researchers were satisfied with the donors and their samples, they introduced the thawed fecal matter into the guts of 17 adults and three children who had experienced at least three bouts of mild to moderate C. difficile infections. Half the donors received the fecal matter through gastrointestinal tubes, whereas the other half received it by way of colonoscopy.

The researchers found that a single dose of thawed fecal matter was enough to cure 14 out of the 20 study participants. Five of the remaining six participants received a second treatment, and four were cured — a result that amounts to an overall success rate of 90 percent. Given the small sample size, the doctors repeated the trial with an additional set of 11 patients. Once again, they obtained a success rate of 90 percent.

One patient was self-administering fecal enemas

They're now investigating whether it might be possible to administer the donations in capsules that would remain intact until they reached the small intestine. Such a delivery method would, for obvious reasons, likely be preferred by patients.

As for the participant who declined to receive a second treatment, researchers said they later discovered that he had been self-administering fecal enemas, using donations from his roommate. "Some people are undertaking this at home for a variety of medical purposes," Hohmann said. "There's a lot about it on the internet." But DIY fecal transplants should be avoided, she said, because feces obtained from people in one's entourage aren't screened for hazardous microbes — and that friendly, neighborhood donor might not be as healthy as a patient would like to think.