Inclusion Criteria

1. Males and females 18-65 years of age.
2. Residents of the United States.
3. Single draining perianal fistula for at least three months despite standard therapy
4. Concurrent therapies are permitted (such as antibiotics, corticosteroids, thiopurines).
5. Have no contraindications to MR evaluations: e.g. pacemaker or magnetically active metal fragments, claustrophobia
6. Ability to comply with protocol
7. Competent and able to provide written informed consent
8. Patients that were treated with an MSC-coated fistula plug in the study IRB#12-009716 or IRB#15-003200

Exclusion Criteria

1. Inability to give informed consent.
2. Clinically significant medical conditions within the six months before administration of MSCs: e.g. myocardial infarction, active angina, congestive heart failure or other conditions that would, in the opinion of the investigators, compromise the safety of the patient.
3. Specific exclusions: Evidence of hepatitis B, C, or HIV
4. History of cancer including melanoma (with the exception of localized skin cancers)
5. Investigational drug within thirty (30) days of baseline
6. A resident outside the United States
7. Previous allergic reaction to a perianal fistula plug.
8. Allergic to local anesthetics
9. Pregnant patients or trying to become pregnant or breast feeding.
10. Non-enterocutaneous tracts (i.e. recto-vaginal, entero-vesicular)