Crohn Disease vs Ulcerative Colitis

Why CT-guided percutaneous drainage is correct

• A psoas abscess larger than 3-4 cm complicating Crohn's disease should first be controlled with image-guided percutaneous drainage plus broad-spectrum antibiotics.
• An active abscess or sepsis is a contraindication to escalating biologic therapy, so infliximab must be held until the infection resolves.
• Source control by drainage, rather than immediate surgery, lets the inflammation settle so any definitive resection can be done electively under better conditions.

Why the others are wrong

• Broad-spectrum IV antibiotics alone — A 5-cm drainable collection needs source control; antibiotics without drainage will not clear it (premature closure on medical therapy alone).
• Intensified infliximab dosing — Escalating immunosuppression during an active infection is contraindicated and would worsen the abscess (right-disease-wrong-step).
• Open surgical abscess drainage — A retroperitoneal psoas collection of this size is readily accessible percutaneously, which achieves the same source control with far less morbidity in an immunosuppressed patient; open drainage is reserved for collections that cannot be reached or that fail image-guided drainage.

Why Oral plus topical 5-aminosalicylic acid is correct

• Continuous inflammation extending proximally from the rectum, crypt abscesses, and absent granulomas are diagnostic of ulcerative colitis with extensive (left-sided to transverse) involvement
• The stem's afebrile, hemodynamically stable, non-anemic picture with only mildly elevated inflammatory markers defines mild-to-moderate (not acute severe) disease, for which 5-ASA is first-line
• For mild-to-moderate extensive UC, combined oral mesalamine plus topical (rectal) mesalamine is superior to either alone and is the ACG/AGA-recommended initial therapy
• Corticosteroids, immunomodulators, and biologics are escalation steps reserved for 5-ASA failure or moderate-to-severe disease

Why the others are wrong

• Ciprofloxacin plus metronidazole — antibiotics do not treat the underlying inflammation of UC and are reserved for infectious colitis or septic Crohn complications (confused-with infectious colitis)
• Azathioprine — an immunomodulator for steroid-dependent or steroid-refractory disease, not initial induction therapy, and it is too slow in onset for first-line use (right-class-wrong-line)
• Oral prednisone induction therapy — systemic corticosteroids induce remission in moderate-to-severe UC or after an adequate 5-ASA trial fails; this patient meets neither condition, and steroid toxicity is unjustified before optimized mesalamine is attempted (escalation-too-early)

Additional high-yield points

• UC vs Crohn: continuous involvement, rectal involvement, no granulomas, and mucosal (non-transmural) inflammation favor UC
• Acute severe UC (Truelove-Witts: >=6 bloody stools/day PLUS fever, tachycardia, anemia, or raised ESR/CRP) instead requires admission, IV corticosteroids, VTE prophylaxis, infection testing, and rescue-therapy planning
• Begin colonoscopic dysplasia surveillance 8-10 years after diagnosis in extensive colitis