100+ Free Cert Gastroenterology(SA) Phys Practice Questions

Explanation: For mild-to-moderate left-sided ulcerative colitis, high-level evidence and international guidelines (ECCO, ACG, SAGES) recommend combination therapy with oral 5-ASA (mesalazine 2.4 g – 4.8 g daily) plus topical 5-ASA (mesalazine 1 g suppository or enema daily). Combination therapy is significantly superior to either oral or topical mesalazine monotherapy for rapid symptom resolution and mucosal healing.

Explanation: Non-caseating epithelial granulomas and transmural inflammation spanning across all gut wall layers are hallmark features of Crohn's disease. Ulcerative colitis is characterized by mucosal and submucosal inflammation limited to the colon, whereas Crohn's can affect any part of the GI tract from mouth to anus with discontinuous ('skip') lesions.

Explanation: According to the Oxford (Travis) criteria, patients with ASUC evaluated on Day 3 of IV corticosteroid therapy who have >8 bloody stools per day OR 3 to 8 bloody stools per day accompanied by a CRP >45 mg/L have an 85% risk of requiring colectomy during that admission. This mandates immediate discussion of rescue therapy (infliximab or ciclosporin) or surgery.

Explanation: Head-to-head randomized trials (GETAID CYCLICAL trial and UK CONSTRUCT trial) demonstrated equivalent efficacy between IV Infliximab (5 mg/kg) and IV Ciclosporin (2 mg/kg) for steroid-refractory ASUC in terms of short-term response, 90-day colectomy rates, and long-term colectomy-free survival. Infliximab is often preferred due to ease of administration and lack of need for therapeutic drug level monitoring.

Explanation: The optimal multidisciplinary approach for complex fistulizing perianal Crohn's disease involves: (1) prompt surgical control of sepsis via incision/drainage of perianal abscesses and non-cutting seton insertion, (2) temporary antibiotic therapy (ciprofloxacin/metronidazole), and (3) induction and maintenance anti-TNF therapy (Infliximab), ideally combined with a thiopurine (combination therapy).

Explanation: TPMT testing identifies patients at risk for severe azathioprine-induced myelosuppression. Intermediate metabolizers (heterozygous low/intermediate TPMT activity) accumulate high levels of active cytotoxic 6-thioguanine nucleotides (6-TGN) if given standard doses; guidelines recommend starting at 30%–50% of the standard dose (e.g. 1.0–1.25 mg/kg/day) with frequent CBC monitoring. Absent TPMT activity requires complete avoidance or >90% dose reduction.

Explanation: Thiopurine shunting (hypermethylation) is characterized by low 6-TGN and excessively high 6-MMP levels, causing therapeutic failure and hepatotoxicity. Adding low-dose Allopurinol (100 mg daily) inhibits xanthine oxidase, shifting metabolism toward 6-TGN production. Because Allopurinol dramatically increases 6-TGN levels, the azathioprine dose MUST be reduced to 25%–33% of the original dose (e.g., 37.5–50 mg/day) with mandatory blood count monitoring.

Explanation: Colorectal cancer surveillance colonoscopy in patients with extensive ulcerative colitis or Crohn's colitis (involving >1/3 of colon) should commence 8 years after the onset of IBD symptoms (not date of diagnosis). In patients with concomitant Primary Sclerosing Cholangitis (PSC), surveillance begins immediately upon PSC diagnosis and continues annually.

Explanation: The presence of Primary Sclerosing Cholangitis (PSC) in patients with IBD dramatically increases the risk of colorectal dysplasia and adenocarcinoma (up to 4-fold to 5-fold higher than IBD alone). Guidelines recommend annual surveillance colonoscopy with high-definition chromoendoscopy and targeted biopsies starting immediately upon PSC diagnosis, regardless of IBD activity or duration.

Explanation: When secondary loss of response to infliximab is driven by high-titer anti-drug antibodies (immunogenic loss of response) accompanied by undetectable or low drug levels, dose escalation of infliximab is ineffective as the antibodies rapidly clear the drug. The patient should be switched out-of-class (e.g., Ustekinumab, Vedolizumab, or Risankizumab) or to a second anti-TNF (Adalimumab), ideally with immunomodulator co-therapy to prevent anti-drug antibody formation against the new agent.