Case discussion
01Clinical context
A patient with known Crohn's disease underwent CT imaging to evaluate perianal pain and swelling. The study aimed to assess for septic complications and bowel involvement.
02Key imaging findings
CT shows a left perianal abscess measuring approximately 3.8 × 3.2 × 4.0 cm with surrounding inflammatory fat stranding. A fistulous tract extends from right to left across the perianal region, about 2.8 cm long, with probable external opening at 11 o'clock and suspected internal opening near 7 o'clock. Segmental thickening of the terminal ileum wall indicates active Crohn's disease. Mildly enlarged bilateral para-aortic lymph nodes are likely reactive. Bilateral sacroiliitis is present, consistent with enteropathic arthropathy. A small benign lytic lesion is seen in the right ischium, and a probable incidental sacral Tarlov cyst is noted. No bowel obstruction, pneumoperitoneum, or intra-abdominal abscess detected.
03Diagnostic reasoning
The diagnosis was established on contrast-enhanced CT, which clearly demonstrated the left perianal abscess with surrounding inflammatory changes and the fistulous tract crossing the perianal region. The location of probable external and internal openings was inferred from the tract orientation. Segmental ileal wall thickening was noted, consistent with active Crohn's disease. Additional findings of sacroiliitis and lymphadenopathy were identified, supporting systemic inflammatory involvement.
04Questions for clinical practice
What is the recommended management for the perianal abscess and fistula? Surgical drainage of the abscess combined with medical therapy for Crohn's disease is typically required. How often should imaging be repeated? Follow-up imaging depends on clinical response but is usually performed if symptoms persist or worsen. Does the sacroiliitis require separate treatment? Yes, sacroiliitis related to enteropathic arthropathy may need rheumatologic evaluation and treatment.
05Teaching point
CT imaging is essential in evaluating complex perianal septic disease in Crohn's patients, delineating abscess size, fistula anatomy, and associated bowel and joint involvement. Recognizing these features guides surgical and medical management to prevent complications.
Shown for education. De-identified — no identifiable patient data. A radiology report is a specialist opinion and must be read with the full clinical context by the treating physician.
