To identify predictive factors of adalimumab (anti TNF) response in patients with luminal Crohn's disease complicated by intra-abdominal and/or pelvic abscess after complete resolution of infection.

Multicenter prospective observational cohort.

Initial management of sepsis and abscess (Before anti-TNF therapy initiation) i. Antibiotics. ii. Percutaneous drainage will be performed every time when possible iii. Surgical drainage will be performed if percutaneous drainage is not accessible or fails iv.

Concomitant medications :

• Steroids will be rapidly tapered and stopped.
• Azathioprine, 6-mercaptopurtine, 5-ASA derivatives and methotrexate will be maintained at a stable dose.
• If not present at inclusion, immunosuppressors could be introduced at the discretion of investigator
• Antibiotics could be used if needed for infections not related to intra-abdominal abscess recurrence and Crohn's disease. v.

Supportive care including artificial nutrition will be started if necessary.

2. Anti-TNF therapy:

- The anti-TNF agent will be adalimumab, administered as subcutaneous injection of 160 mg at W0, 80 mg at W2, followed by 40 mg every 2 weeks.

Inclusion Criteria:

• Age greater than 18 years.
• Diagnosis of Crohn's disease (confirmed by clinical evaluation and a combination of endoscopic, histological, radiological, and/or biochemical investigations according to European guidelines)
• AND diagnosis of spontaneous intra-abdominal and/or pelvic abscess according to radiologic criteria confirmed by US, CT or magnetic resonance enterography (MRE).
• In patients who have not responded despite a full and adequate course of therapy with a corticosteroid and/or an immunosuppressant or who are intolerant to or have medical contraindications for such therapies
• Written consent MAIN

Exclusion Criteria:

• Age under 18 years. - Absence of written consent. - Post-operative abscess (occurring within 12 weeks after intestinal resection). - Isolated intra-parietal abscess of small intestine or colon. - Need for immediate surgery including irreversible bowel obstruction, peritonitis or uncontrolled sepsis. - Perineal abscess complicating perianal Crohn's disease. - Abscess developing under anti-TNF therapy. - Previous failure or intolerance to adalimumab. - Contraindication to anti-TNF therapy.

Patients presenting a luminal Crohn's disease complicated by an intra abdominal and/or pelvic abscess meeting the inclusion criteria and followed or addressed in one of the participating centers will be enrolled in the pre-inclusion phase of the study consisting in abscess drainage and antibiotic therapy as recommended by local and European guidelines.

- After the initial pre-inclusion phase of the study, if there is a complete resolution of sepsis and abscess confirmed by MRE, patients for whom the treating physician decides to introduce adalimumab according to local and European Guidelines will be included in the anti-TNF treatment phase.