Fecal Microbiota Transplantation (FMT) is a medical procedure that involves transferring stool from a healthy donor into a recipient’s gastrointestinal tract to restore microbial balance. This process reintroduces a complex community of beneficial microorganisms into a disrupted gut environment. FMT is primarily used to treat recurrent Clostridioides difficile infection, an illness causing severe diarrhea that is often difficult to treat with antibiotics alone. The procedure aims to introduce healthy gut flora that can outcompete and prevent the return of the harmful bacteria.
Preparing the Donor Material
The process begins with rigorous screening of potential donors, as safety and quality control are paramount for the transplant material. A comprehensive questionnaire is used to assess the donor’s medical history, lifestyle, and risk factors for transmissible diseases. This initial step is highly selective, with some stool banks reporting that less than three percent of applicants ultimately qualify to donate.
Donors who pass the preliminary screening undergo extensive laboratory testing on both their blood and stool samples. Blood tests rule out infectious agents such as HIV, hepatitis A, B, and C, and syphilis. Stool samples are analyzed to check for harmful bacteria, parasites, and the presence of C. difficile itself. This screening ensures the donated material is free from known pathogens before transplantation.
Once a sample is accepted, it moves to a specialized laboratory for processing. The donated stool is typically mixed with a solution, often saline or glycerol, and then homogenized. This mixture is strained or filtered to remove solid particles, resulting in a liquid slurry that contains the concentrated microbial community. This final product can then be used immediately, or it is often frozen for storage in a stool bank until it is needed.
The prepared material takes two main forms for administration: a liquid slurry for direct delivery or freeze-dried material enclosed in capsules. Freezing the material allows for a ready supply of tested donor stool, which is often preferred for logistical reasons. The capsules contain the freeze-dried microbes and are designed with an acid-resistant coating to prevent the bacteria from being destroyed by stomach acid before reaching the intestines.
Patient Readiness for the Procedure
The recipient must undergo specific preparation steps to create the best environment for the incoming microbes. If the patient is being treated for a C. difficile infection, they must first complete a course of antibiotics, such as vancomycin, to reduce the existing harmful bacteria. Following this treatment, a washout period is necessary, typically stopping all antibiotics at least 48 hours before the transplant.
A cleansing of the colon is generally required so the donor material can coat the intestinal lining effectively. This preparation is similar to that for a standard colonoscopy, involving a clear liquid diet and consuming a laxative or bowel prep solution. Emptying the colon allows the transplanted microbiota maximum surface area for implantation and growth.
For patients receiving the transplant via the lower gastrointestinal tract, such as with a colonoscopy, bowel preparation is necessary. However, preparation instructions vary depending on the chosen delivery method. Some non-invasive options, like certain enemas or capsules, require less or no bowel preparation.
Methods of Transplant Delivery
The prepared fecal material can be introduced into the recipient’s gastrointestinal tract through several different pathways. The choice of method often depends on the patient’s condition, the location of the infection, and the general feasibility of the procedure.
Colonoscopy is the most common and historically preferred method, especially for lower gastrointestinal issues. During this procedure, a flexible tube with a camera is inserted through the rectum and advanced into the colon. The donor slurry is administered through a channel in the scope, typically delivered to the right side of the colon or the cecum. This method allows the physician to visually inspect the intestinal lining but requires sedation and standard bowel preparation.
The material can also be delivered through the upper gastrointestinal tract using an upper endoscopy or a nasogastric tube (NGT). An upper endoscopy involves passing a scope through the mouth, while an NGT is a thin tube inserted through the nose into the stomach or small intestine. This route is selected when a colonoscopy is not possible, though the microbes must survive the stomach acid to reach the colon.
A less invasive option is the retention enema, which delivers the liquid material directly into the rectum. The enema is administered by a nurse, and the patient is asked to retain the liquid for about 30 minutes to allow the microbes to spread into the colon. This method does not require sedation or full bowel preparation, making it a simpler and more accessible procedure.
Oral capsules represent the least invasive delivery route, utilizing the freeze-dried donor material. Patients simply swallow the acid-resistant capsules with water in an outpatient setting. This method avoids the need for sedation or endoscopy and, while sometimes still recommending a brief fast, often eliminates the need for a full bowel preparation.