Inclusion Criteria:

* Informed consent will be obtained before any study-related procedures
* Age \>/= 18 and \* Diagnosis of Chronic Pouchitis or Crohn's-like disease of the pouch based on the following criteria:

* Chronic Antibiotic-Dependent Pouchitis: Recurrent symptoms of pouchitis (frequency, urgency, bleeding, abdominal pain or cramping, or pelvic discomfort) that respond to antibiotic therapy but relapse shortly after stopping antibiotics, thus necessitating continuous antibiotic therapy to achieve symptom control.
* Chronic Antibiotic Refractory Pouchitis: Lack of response to standard antibiotic therapy, requirement of a longer duration of antibiotic therapy than expected with minimal improvement in symptoms, in association with typical symptoms of pouchitis (frequency, urgency, bleeding, abdominal pain or cramping, or pelvic discomfort).
* Crohn's-like disease of the pouch: Presence of a perianal or other fistula that developed at least 12 months after the final stage of Ileal Pouch Anal Anastomosis (IPAA) surgery, stricture of the pouch body or pre-pouch ileum, or the presence of pre-pouch ileitis. Pouch body inflammation (pouchitis) may often coexist in the setting of Crohn's-like disease of the pouch.
* Participants with a proven history of ulcerative colitis and history of 1,2, modified -2 or 3 stage IPAA and ileostomy takedown
* Ability to access internet for electronic database entry
* Only those individuals for whom a provider is considering initiating mirikizumab for the treatment of chronic pouchitis or Crohn's-like disease of the pouch will be eligible for participation.

Exclusion Criteria:

* Prior exposure to mirikizumab
* Known hypersensitivity to mirikizumab or its metabolites
* Current infection with Clostridioides difficile
* Known HIV or active Hepatitis B/C
* Clinically significant liver disease (Primary Sclerosing Cholangitis with LFT's \<1.5 upper limit of normal can be included)
* Severe hepatic impairment, defined as Child-Pugh Class C
* Known decreased kidney function with a glomerular filtration rate \<45 ml/min/1.732
* History of malignancy, except for basal cell carcinoma, non-metastatic squamous cell carcinoma of the skin, or prior malignancy with curative therapy completed at least 5 years prior to screening and no recurrence.
* Clinically significant laboratory results at screening or baseline, as judged by the Investigator from local testing.
* Female who is pregnant, breast-feeding or intends to become pregnant or is of child-bearing potential and not using a highly effective contraceptive method.
* Participation in any clinical trial of an approved or non-approved investigational medicinal product within 30 days before screening.
* Any disorder, which in the investigator's opinion might jeopardize participant's safety or compliance with the protocol.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 3/13/2025. Questions regarding updates should be directed to the study team contact.