Inflammatory Bowel Disease: UC Complete

0:00Welcome to Board Pearls. This is episode one of three of the Inflammatory Bowel Disease chapter, in the Colorectal and Pelvic Floor Disorders module. This episode is ulcerative colitis from classification through full medical management: the UC-versus-Crohn distinction, the Mayo score driving severity-tiered therapy, the acute severe UC script with its salvage rule, mesalamine for mild-to-moderate disease, and the positioning of the biologics and small molecules for steroid-dependent or biologic-failure disease.

0:30Inflammatory bowel disease is one immune problem with two faces, and almost every board question turns on keeping them apart. The unifying lesion is a breakdown of tolerance for the gut microbiota in a genetically primed host, and once the inflammatory loop is established it self-amplifies through a cytokine cascade, and that cascade is why the drug list looks the way it does: TNF, the IL-12 and IL-23 pathway, IL-17, and the integrin-mediated trafficking of lymphocytes to the gut are the targets, and every biologic hits one of them. Holding that pathway map is the prerequisite for the drug-selection logic that closes the episode.

1:08The two diseases sort by mechanism and environmental signal. UC is mucosal, continuous, and starts at the rectum and extends proximally without skip lesions. Crohn's is transmural, segmental, and can hit anywhere from mouth to anus, most often involving the terminal ileum. The smoking signal goes opposite directions cleanly: smoking is protective in UC, so a patient with quiescent UC who quits sometimes flares within months, while it's harmful in Crohn's, accelerating stricturing and penetrating behavior and worsening post-operative recurrence. Appendectomy before age twenty for true appendicitis is mildly protective against UC, a paradox the boards return to, and NSAIDs trigger flares of either disease, which is the practical counseling point. The genetics also split: the canonical Crohn's gene impairs Paneth-cell defensin secretion and macrophage handling of bacteria, and its carriers tend toward ileal Crohn's with stricturing or penetrating behavior, and it doesn't associate with UC, while UC has its own susceptibility map, and the shared IL-23 receptor variant is the molecular reason the IL-23-targeting drugs work in both diseases.

2:15The diagnostic anchor for UC is the convergence of clinical picture, endoscopy, histology, and biomarkers: bloody diarrhea with urgency and tenesmus, continuous inflammation extending proximally from the rectum, and crypt distortion with basal plasma cells and crypt abscesses confined to the mucosa. The Montreal extent classification is the anatomic tag to know: E1 is proctitis, E2 is left-sided colitis up to the splenic flexure, and E3 is extensive colitis proximal to the splenic flexure, and that extent drives the drug-delivery decisions. Fecal calprotectin discriminates IBD from functional bowel disease and tracks activity over time, with CRP and ESR supporting but less specific. And a word on the indeterminate case, because it changes the surgical conversation: when colonic inflammation can't be confidently assigned after a full workup, a portion declare themselves over years, often as Crohn's when small-bowel involvement appears, and that matters because a pelvic pouch is less durable if Crohn's later declares itself, so a vignette with pancolitis, ambiguous histology, and no small-bowel disease asking about pouch candidacy is asking you to slow down before promising restorative surgery.

3:31Now severity, because it triggers everything downstream. The Mayo score is the main UC activity index, four components each scored zero to three, stool frequency above baseline, rectal bleeding, endoscopic appearance, and physician global assessment, totaling zero to twelve, with remission at roughly two or less, mild three to five, moderate six to ten, and severe eleven to twelve. The endoscopic subscore is the single most informative component: zero normal, one erythema with decreased vascular pattern, two friability and erosions, three spontaneous bleeding and ulceration. And mucosal healing, defined as an endoscopic subscore of zero or one, is the modern treat-to-target endpoint, because it predicts steroid-free remission, fewer hospitalizations, and less colectomy.

4:21Severe UC is hospitalized, and the Truelove-Witts criteria trigger admission: more than six bloody stools a day plus at least one of fever above thirty-seven point eight, heart rate above ninety, hemoglobin under ten and a half, or ESR above thirty. The mechanism of acute severe UC is unchecked inflammation in a normally mucosal disease that starts leaning transmural, so the colon distends, the mucosa shears, and the systemic signal drives the fever and lab derangement, and once it reaches that state it can perforate or progress to toxic megacolon within days, which is why the timeline runs in hours and the decisions are scripted. The inpatient bundle has a fixed shape: stool studies for C. diff because superinfection drives a meaningful fraction of severe flares, flexible sigmoidoscopy with limited insufflation and biopsies to exclude CMV colitis, because CMV in an immunosuppressed UC patient looks like steroid failure and gets ganciclovir rather than more steroid, and cross-sectional imaging to exclude megacolon, defined as a transverse colon over about five and a half to six centimeters, and perforation. Then intravenous methylprednisolone forty to sixty milligrams daily, or equivalent hydrocortisone. The patient eats, antimotility agents are off the table because they precipitate megacolon, and prophylactic anticoagulation is started even with rectal bleeding, because acute severe UC carries a markedly elevated clot risk and the bleeding doesn't buy protection.

5:52The scripted decision point is day three, where the Oxford rule defines steroid non-response: more than eight stools a day, or three to eight stools with a CRP above forty-five. The reason day three matters comes down to colectomy risk, because a patient who meets that threshold has a very high likelihood of needing colectomy on that admission if steroids alone are continued, and that is the entire rationale for moving to salvage rather than escalating the steroid dose. The temptation is to push the steroid because the patient is on one and not yet better, and that temptation costs colons. Salvage is either infliximab or cyclosporine, roughly equivalent for colectomy avoidance at a year in the head-to-head data. Infliximab is five milligrams per kilogram, with a higher induction dose or accelerated dosing considered when albumin is low, because albumin loss into the inflamed colon speeds infliximab clearance. Cyclosporine is a continuous infusion at two milligrams per kilogram per day, targeting a whole-blood level of one hundred fifty to two hundred fifty, converted to oral once response is achieved with thiopurine bridging, and because it carries renal, neurologic, and hypertensive risks and can't be long-term maintenance, infliximab is the more common contemporary salvage outside high-volume cyclosporine centers, with tofacitinib emerging as oral salvage.

7:11Salvage is a single shot, and that rule recurs: if the patient hasn't responded to either infliximab or cyclosporine within five to seven days, the answer is colectomy, typically a subtotal colectomy with end ileostomy and rectal-stump preservation for later restorative surgery, because sequential salvage from one agent to the other carries a high infection rate and is avoided. The emergent surgical indications regardless of medical response are perforation, uncontrolled hemorrhage, and toxic megacolon that doesn't improve within a day or two. The colectomy risk in the modern era is lower than the pre-biologic era, and the acute severe UC patient is the high-acuity slice that drives most of the surgery.

7:49Step back to the much larger mild-to-moderate population, where the foundation is the mesalamine family, and the reason there are so many products is delivery, because the effect depends entirely on getting the active drug to the inflamed mucosa and the small bowel and colon handle it differently, so formulation engineering does the work the molecule can't. One controlled-release form delivers throughout the small bowel and colon, which is why it's the only oral mesalamine with a rationale in small-bowel Crohn's; the pH-dependent forms release in the terminal ileum and colon; the delayed-and-extended-release forms give once-daily colonic delivery for adherence; and the azo-bonded drugs like sulfasalazine and balsalazide are cleaved by colonic bacteria to drop the active drug specifically into the colon. In distal disease the favored move is topical first, because oral preparations can't reliably saturate the rectal mucosa: a one-gram mesalamine suppository nightly reaches the distal fifteen to twenty centimeters and is the answer for proctitis, while a four-gram enema nightly extends to the splenic flexure and is the answer for left-sided disease, with steroid or budesonide foam as alternatives when topical mesalamine fails, though topical mesalamine beats topical steroids head-to-head. And combining oral plus topical mesalamine beats either alone for distal and left-sided disease, which is the favored induction strategy in proctitis and left-sided colitis.

9:13Oral dosing for moderate disease is four point eight grams a day for induction, with the higher dose supported over the lower one for faster mucosal response at similar safety, down-titrated to two point four grams once remission is sustained. For extensive colitis, oral induction dosing with adjunctive topical therapy at the start is appropriate, and if there's no response within four to eight weeks, the move is systemic steroids or advanced therapy. Oral budesonide in its colonic-release form at nine milligrams daily is an alternative for mild-to-moderate disease in patients who fail or don't tolerate mesalamine, with high first-pass metabolism limiting systemic steroid exposure. And sulfasalazine deserves its own slot when peripheral arthritis accompanies UC, because it links the active drug to a sulfa moiety that treats the joints, which pure mesalamine doesn't, dosed up to four grams a day with mandatory folic acid because it inhibits folate absorption, with the sulfa moiety driving most of the side effects, hypersensitivity and hemolysis especially with G6PD deficiency, commonly reversible oligospermia that matters for fertility counseling, and the rare organ hypersensitivities the pure drugs can also cause. So the favored vignette is the UC patient with peripheral inflammatory arthritis where sulfasalazine wins because the joints respond.

10:31A few mesalamine-class traps earn the test: mesalamine can paradoxically worsen colitis as a hypersensitivity reaction, where the answer is to stop the drug, not push the dose, which is the counterintuitive part; interstitial nephritis is the most important idiosyncratic effect across the class, so creatinine is checked at baseline and periodically because it's reversible if caught early; and pancreatitis, pericarditis, hepatitis, and pneumonitis are the answers to the rare hypersensitivity vignettes. And mesalamine is a UC drug, with a limited role in Crohn's covered next episode.

11:03When mesalamine fails or the patient presents moderate-to-severe, the menu opens into biologics and small molecules, organized by mechanism, because mechanism predicts who responds and fails and the boards test exactly that. TNF blockade is the broadly effective foundation, and the newer agents match or exceed it in selected scenarios with differentiated safety, and the exceptions are the teaching. Anti-TNF in UC means infliximab intravenously and adalimumab subcutaneously, plus golimumab, which is UC-approved but not Crohn-approved because the Crohn trials missed their endpoint, while certolizumab is the mirror image, Crohn-only and useful in pregnancy because it barely crosses the placenta. All the anti-TNF agents require tuberculosis screening with an interferon-gamma release assay or skin test plus chest film and hepatitis B screening before starting, with latent TB treated before the biologic and hepatitis B carriers needing concurrent antiviral therapy, because reactivation of either can be fatal, while hepatitis C is screened but doesn't contraindicate. The class risks are serious bacterial infection with intracellular organisms, invasive fungal infection like histoplasmosis in endemic areas, drug-induced lupus, demyelinating disease which is why it's avoided in multiple sclerosis, worsening heart failure which is why it's avoided in advanced heart failure, and lymphoma, with the hepatosplenic T-cell lymphoma signal in young men on combination anti-TNF and thiopurine, so when combination therapy is needed the workaround is anti-TNF plus methotrexate. Biosimilars are clinically equivalent.

12:41Vedolizumab is the gut-selective alternative, a monoclonal against the integrin that traffics lymphocytes specifically to gut mucosa, so systemic immunosuppression is minimal and the safety sits close to placebo, but the onset is slower, often by six to ten weeks, which is why it's not the first move in acute severe disease. It outperformed adalimumab in moderate-to-severe UC in the head-to-head trial, which is the headline for the class, and it doesn't carry the brain-infection signal of the older broader integrin blocker because its target is gut-selective. The trade-off is that the gut-restricted blockade has limited effect on extraintestinal manifestations, so a UC patient with prominent peripheral arthritis or uveitis is not the vedolizumab patient. Ustekinumab targets the shared subunit of IL-12 and IL-23 and is approved for both diseases, weight-based intravenous induction then ninety milligrams subcutaneously every eight weeks, effective in anti-TNF failures with low immunogenicity, no boxed warning, and favorable safety. Risankizumab and mirikizumab are the more selective IL-23 inhibitors, now approved across both UC and Crohn's, with intravenous induction and subcutaneous maintenance, and the conceptual advantage of the selective blockade is preserving IL-12 signaling, which may mean a better infection profile. The shared IL-23 pathway is the molecular reason these work across both diseases.

14:05The JAK inhibitors are the oral small molecules. Tofacitinib is a pan-JAK inhibitor for UC, induction ten milligrams twice daily then maintenance five, with escalation back to ten allowed in patients without clot risk, and upadacitinib is JAK1-selective and approved for both diseases, induction forty-five milligrams daily then maintenance fifteen or thirty. The class carries a boxed warning from rheumatoid-arthritis post-marketing data: serious infection particularly herpes zoster reactivation, major cardiovascular events, malignancy, thrombosis, and mortality, so the recombinant zoster vaccine is recommended before starting any JAK inhibitor regardless of age, and routinely in adults fifty and up before any biologic, and they raise lipids, cause cytopenias, and need monitoring. Their advantage is rapid onset within days to weeks, oral dosing, and efficacy in anti-TNF failures. And the sphingosine-1-phosphate modulators, ozanimod and etrasimod, are approved for UC, working by trapping lymphocytes in lymph nodes so fewer traffic to inflamed tissue, requiring a titration on initiation because of cardiac effects with a baseline ECG, excluding patients with conduction block or recent cardiac events, with a baseline eye exam for macular edema risk and varicella status checked, and they induce lymphopenia by design and raise zoster risk.

15:25So how do you choose? Match mechanism to patient. Anti-TNF stays the broad-effect first choice, especially when extraintestinal manifestations are prominent, because those respond to systemic TNF blockade in a way gut-selective vedolizumab can't. Vedolizumab pulls forward in moderate-to-severe UC when infection or malignancy risk argues against systemic immunosuppression, because the gut-selective profile is safer. The JAK inhibitors are the oral move in anti-TNF failure when there's no clot risk and the patient isn't in the older cardiac-risk group, and when rapid onset matters. Ustekinumab and the selective IL-23 inhibitors pull forward for low-immunogenicity injectable maintenance and in anti-TNF failures. And the sphingosine-1-phosphate modulators are the oral option for UC in a patient with a clean cardiac and eye exam who wants a pill without the JAK cardiovascular signal. Pregnancy data favor anti-TNF, vedolizumab, and ustekinumab and rule out the JAK inhibitors, and coverage and prior failures fill in the rest.

16:35So how does UC sit together? It sorts from Crohn's on three discriminators: the pattern of inflammation, the smoking direction, and the signature genetics. Severity then sends the patient down a fixed escalation, topical and oral mesalamine, then systemic steroid, then biologic or small molecule. The acute severe patient runs a hard-coded inpatient script with day three as the salvage trigger and the single-shot rule. And the moderate-to-severe drug choice is a mechanism-to-patient match: TNF blockade covers the extraintestinal-manifestation vignette, vedolizumab buys gut-selective safety, the IL-23 inhibitors stretch across both diseases, the JAK inhibitors deliver rapid oral therapy at a real safety cost, and the sphingosine-1-phosphate modulators give an oral option in a clean cardiac and eye patient.

17:27Episode two turns that framework on Crohn's, where the dominant question stops being severity and becomes phenotype: the Montreal location-behavior-age classification, the risk stratification driving step-up versus top-down therapy, and the phenotype-specific algorithms for perianal disease and post-operative recurrence.

17:47For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode one of three of chapter fourteen, and I'll see you in the next one.