What Is Ulcerative Colitis?
Ulcerative colitis (UC) is a chronic inflammatory bowel disease that exclusively affects the mucosa of the colon (large intestine) and rectum. Unlike Crohn's disease, which can affect any part of the gastrointestinal tract, UC is limited to the colon and progresses continuously from the rectum.
The disease manifests with periods of activity (flares) alternating with phases of remission. During flares, the colonic mucosa shows diffuse inflammation, with superficial ulcerations, edema, and bleeding. Global prevalence ranges from 2 to 500 cases per 100,000 inhabitants and is higher in industrialized countries.
Peak incidence occurs between 15 and 30 years of age, with a smaller second peak between 50 and 70 years. It affects men and women equally. The impact on quality of life can be substantial, with significant social, occupational, and emotional limitations during flares.
Colonic Inflammation
UC causes chronic inflammation limited to the mucosa of the colon and rectum, with continuous, ascending progression from the anorectal junction.
Relapsing Course
The disease alternates between flares (active inflammation) and remission (healed mucosa), with variable frequency and intensity.
Immune Basis
Results from a dysregulated immune response against the intestinal microbiota in genetically predisposed individuals.
Pathophysiology
The pathogenesis of UC involves a complex interaction between genetic predisposition, environmental factors, dysbiosis of the intestinal microbiota, and dysregulation of the immune system. More than 200 genetic loci have been associated with inflammatory bowel diseases, many related to epithelial barrier function and immune regulation.
The intestinal epithelial barrier plays a central role in the disease. In patients with UC, there is increased intestinal permeability with impairment of the tight junctions between enterocytes. This allows the translocation of bacterial antigens to the lamina propria, triggering an exaggerated inflammatory response.
In UC, a Th2-type immune response predominates, with excessive production of cytokines such as IL-5, IL-13, and IL-33. Atypical NKT cells produce IL-13, which contributes directly to epithelial barrier dysfunction and cytotoxicity against colonocytes. Neutrophils infiltrate the mucosa, forming crypt abscesses — a characteristic histopathologic finding.
Intestinal dysbiosis is a consistent finding in UC. There is reduced microbial diversity, decreased butyrate-producing bacteria (such as Faecalibacterium prausnitzii), and increased potentially pathogenic bacteria. Butyrate is the main energy substrate for colonocytes, and its deficiency compromises barrier integrity.
Symptoms
UC symptoms depend on the extent and severity of colonic inflammation. The classic presentation includes bloody diarrhea, fecal urgency, and crampy abdominal pain. Extraintestinal manifestations may accompany or even precede intestinal symptoms.
Clinical Manifestations of UC
- 01
Diarrhea with blood and mucus
Cardinal symptom of the disease. Rectal bleeding can range from mild (streaks of blood) to intense with frank hematochezia.
- 02
Urgency and rectal tenesmus
Urgent need to defecate, often passing small amounts of blood and mucus. May cause fecal incontinence.
- 03
Crampy abdominal pain
Predominates in the lower left quadrant. Partially relieved by defecation. Severe pain may indicate complications.
- 04
Increased bowel frequency
Patients with active disease may have 6 to 20 bowel movements per day, including nighttime stools.
- 05
Fatigue and malaise
Systemic inflammation and anemia contribute to significant fatigue, often underestimated by patients.
- 06
Weight loss
Results from reduced food intake (fear of triggering symptoms) and chronic catabolic inflammation.
- 07
Joint manifestations
Peripheral arthritis and sacroiliitis occur in up to 25% of patients — the most common extraintestinal manifestation.
- 08
Cutaneous and ocular manifestations
Erythema nodosum, pyoderma gangrenosum, uveitis, and episcleritis can occur in up to 15% of patients.
Diagnosis
UC diagnosis is based on a combination of clinical, laboratory, endoscopic, and histopathologic findings. No single test confirms the diagnosis alone. Colonoscopy with biopsy is the fundamental examination for diagnosis and assessment of disease extent.
Fecal calprotectin is a noninvasive marker of intestinal inflammation useful for monitoring disease activity and differentiating inflammatory bowel disease from irritable bowel syndrome. Values above 250 mcg/g are highly suggestive of active mucosal inflammation.
🏥Diagnostic Criteria for UC
- 1.Compatible clinical presentation: bloody diarrhea, rectal urgency, abdominal pain
- 2.Colonoscopy: continuous mucosal inflammation starting at the rectum, without skip áreas
- 3.Biopsy: crypt architectural distortion, chronic inflammatory infiltrate in the lamina propria, crypt abscesses
- 4.Exclusion of infectious causes (stool culture, C. difficile testing, parasitology)
- 5.Exclusion of colonic Crohn's disease (absence of granulomas, transmural involvement, or skip lesions)
DISEASE EXTENT (MONTREAL CLASSIFICATION)
| CLASSIFICATION | EXTENT | FREQUENCY |
|---|---|---|
| E1 — Proctitis | Limited to the rectum (up to 15 cm) | 30-40% of cases |
| E2 — Left-sided colitis | Up to the splenic flexure | 30-40% of cases |
| E3 — Pancolitis | Beyond the splenic flexure | 20-30% of cases |
DIFFERENTIAL DIAGNOSIS
Differential Diagnosis
Colonic Crohn's Disease
- May involve the entire GI tract
- Transmural lesions
- Fistulas, strictures
- Granulomas on biopsy
Diagnostic Tests
- Colonoscopy with biopsy
- MRI of the small bowel
Infectious Colitis (Salmonella, Shigella, E. coli O157)
- Acute onset
- Positive stool culture
- High fever
Diagnostic Tests
- Stool culture
- Fecal PCR
IBS
Read more →- No bleeding
- Normal calprotectin
- Normal colonoscopy
Diagnostic Tests
- Fecal calprotectin
- Colonoscopy
C. difficile Colitis
- Recent antibiotic use
- Severe watery diarrhea
- Positive toxin
- Toxic megacolon = urgent surgery
Diagnostic Tests
- Toxin A/B
- PCR
Ischemic Colitis
- Older adults
- Atherosclerotic disease
- Abdominal pain + sudden bleeding
- Mesenteric ischemia = emergency
Diagnostic Tests
- Contrast-enhanced CT
- Colonoscopy
Crohn's Disease vs. Ulcerative Colitis: A Critical Distinction
The distinction between colonic Crohn's and UC is fundamental for treatment — and in 10-15% of cases it is not possible (indeterminate colitis). In UC, inflammation is continuous, starts in the rectum, and extends proximally, involving only the mucosa and submucosa. In Crohn's disease, lesions are discontinuous ("skip lesions"), can affect any segment of the GI tract, are transmural, and frequently produce fistulas, strictures, and abscesses. Biopsy is essential: noncaseating granulomas are diagnostic of Crohn's.
The practical implication is significant: vedolizumab and ozanimod have a specific indication for UC; ustekinumab is more commonly used in Crohn's; curative surgery (total colectomy) is an option in severe refractory UC, but not in Crohn's. Magnetic resonance imaging of the small bowel is mandatory when Crohn's is suspected, to assess the small intestine, which colonoscopy cannot reach. The gastroenterologist defines the diagnosis based on the totality of clinical, endoscopic, and histologic findings.
Infectious Colitis and C. difficile: Rule Out Infection Before Immunosuppression
Infectious colitis caused by Salmonella, Shigella, Campylobacter, or E. coli O157:H7 can mimic UC with abrupt onset: bloody diarrhea, fever, and abdominal pain. The distinction is temporal — acute infectious colitis resolves within days to weeks with (or without) treatment; UC is chronic and recurrent. Stool culture and multiplex fecal PCR (which detects multiple pathogens simultaneously) are mandatory at first presentation of bloody diarrhea, before starting corticosteroids or immunosuppressants.
Clostridioides difficile can occur in UC patients — and is a pitfall: it can simulate a UC flare, leading to mistaken intensification of immunosuppression while the infection worsens. Toxin A/B testing should be requested in any UC patient with worsening symptoms, especially after recent antibiotic therapy. Oral vancomycin treatment is urgent — delayed diagnosis increases the risk of toxic megacolon.
Ischemic Colitis: Urgent Diagnosis in Older Patients with Bleeding
Ischemic colitis is the most common ischemic disease of the gastrointestinal tract and predominantly affects older adults with atherosclerosis, diabetes, heart failure, or vasoconstrictor use. It manifests with sudden-onset crampy abdominal pain followed by bloody diarrhea — a presentation that can be confused with a UC flare. The preferred location is the left colon (splenic flexure and sigmoid colon), which has borderline vascular flow.
Contrast-enhanced CT of the abdomen shows colonic wall thickening with parietal edema, sometimes pneumatosis. Colonoscopy reveals pale or hemorrhagic mucosa with segmental distribution — an endoscopic distinction from UC, which is continuous and starts at the rectum. Most cases of ischemic colitis resolve spontaneously with supportive care; cases with transmural or progressive ischemia require urgent surgery.
Treatment
UC treatment has two main goals: induce remission during flares and maintain remission long term. The therapeutic approach follows a stepwise ("step-up") strategy, starting with less aggressive medications and intensifying as needed.
The current therapeutic target goes beyond symptom control — the goal is mucosal healing (endoscopic remission), associated with better long-term outcomes, including lower risk of colectomy and colorectal neoplasia.
Aminosalicylates (5-ASA)
First line for mild to moderate disease. Oral and/or topical mesalamine (suppository, enema). Local anti-inflammatory action on the colonic mucosa. Effective for inducing and maintaining remission.
Corticosteroids
Indicated for moderate to severe flares that do not respond to 5-ASA. Oral prednisone or budesonide, or intravenous hydrocortisone in severe cases. Should not be used for maintenance.
Immunomodulators
Azathioprine, 6-mercaptopurine, or methotrexate for corticosteroid-dependent patients. Take 8-12 weeks for full effect. Used as steroid-sparing agents.
Biologic Therapy
Anti-TNF (infliximab, adalimumab), anti-integrin (vedolizumab), or anti-IL-12/23 (ustekinumab) for moderate to severe refractory disease. JAK inhibitors (tofacitinib) are an oral alternative.
Acupuncture as Treatment
Acupuncture has been investigated as complementary therapy in UC, focused on modulating intestinal inflammation and relieving symptoms such as abdominal pain, diarrhea, and fatigue. Experimental and clinical studies suggest plausible mechanisms for its anti-inflammatory effect on the gastrointestinal tract.
The main proposed mechanism involves activation of the cholinergic vagal anti-inflammatory reflex. Stimulation of specific points activates somatic afferent fibers that modulate vagus nerve activity, promoting acetylcholine release at splanchnic nerve terminals. Acetylcholine acts on alpha-7 nicotinic receptors of intestinal macrophages, reducing the production of pro-inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6.
Preliminary clinical studies — including some randomized trials — show that acupuncture and moxibustion may improve disease activity índices and quality of life in patients with mild to moderate UC. However, most studies have methodologic limitations, and current evidence is insufficient to recommend acupuncture as standalone treatment. Its role is complementary, adjunctive to conventional treatment.
Prognosis
Most UC patients have a favorable prognosis with appropriate treatment. About 50% have mild disease that can be controlled with aminosalicylates. Life expectancy matches the general population in most cases.
The main long-term concern is the increased risk of colorectal cancer, which is related to disease extent, duration (especially after 8-10 years), presence of primary sclerosing cholangitis, and family history. Regular colonoscopic surveillance with serial biopsies is essential for early detection of dysplasia.
Approximately 10-15% of patients require colectomy over their lifetime, generally for disease refractory to medical treatment, acute complications (toxic megacolon, perforation), or dysplasia/neoplasia. Total proctocolectomy with ileal pouch is the standard procedure, with good functional results in most cases.
Myths and Facts
Myth vs. Fact
Ulcerative colitis is caused by stress
Stress can trigger flares, but does not cause the disease. UC results from genetic predisposition, intestinal dysbiosis, and immune dysregulation. Stress is a modulating factor, not a causal one.
A specific diet cures ulcerative colitis
No diet has been proven to cure UC. However, individualized dietary adjustments may help control symptoms during flares. Avoiding foods that worsen symptoms is reasonable, but extreme restrictions can lead to nutritional deficiencies.
Biologics are "very strong drugs" and should be avoided
Biologic therapies are safe and highly effective when indicated. The risk of complications from inadequately treated disease is greater than the risks of biologics. Early introduction in patients with moderate to severe disease can prevent irreversible damage.
Every UC patient will need surgery
Only 10-15% of patients require colectomy. With current treatments, including biologics and JAK inhibitors, the colectomy rate has been declining significantly.
When to Seek Help
UC requires regular medical follow-up with a gastroenterologist. Recognizing flare signs early and seeking timely care can prevent serious complications and shorten active inflammation.
Frequently Asked Questions about Ulcerative Colitis
UC has no definitive medical cure — it is a chronic disease with a variable course. However, total colectomy (surgical removal of the colon) is curative for the intestinal disease. With appropriate treatment, most patients achieve prolonged remission and normal quality of life. The goal of modern treatment is deep remission — clinical, endoscopic, and histologic.
UC affects exclusively the colon and rectum, with continuous, superficial inflammation (mucosa). Crohn's disease can involve any segment of the digestive tract (from mouth to anus), with transmural inflammation (the entire thickness of the intestinal wall), potentially forming fistulas, strictures, and granulomas. Treatment and prognosis differ between the two conditions.
Diet does not cause UC, but can modulate symptoms. During flares, foods such as dairy, insoluble fiber, fatty foods, and ultra-processed foods may worsen diarrhea. An anti-inflammatory diet, rich in omega-3 and cooked vegetables, may help maintain remission. Dietary restrictions should be guided by a nutritionist specialized in IBD.
Preliminary clinical studies suggest that acupuncture — especially combined with moxibustion — may relieve symptoms such as abdominal pain, distension, and fatigue and improve quality of life in patients with mild to moderate UC or in remission. Current evidence has methodologic limitations and does not allow conclusions about an effect on the disease course. Acupuncture does not replace aminosalicylates, corticosteroids, immunosuppressants, or biologics — it acts as a complementary resource, and any medication adjustment is always made by the attending gastroenterologist. No pharmacologic interactions with conventional treatments have been described.
Seek emergency care immediately if you experience: more than 6 bloody bowel movements per day, fever above 38.5°C / 101.3°F, severe and diffuse abdominal pain, abdominal distension (suspected toxic megacolon), signs of acute anemia (extreme pallor, severe weakness), or any rapid deterioration in general condition. These situations constitute a severe flare with risk of life-threatening complications.
Biologics (anti-TNF, vedolizumab, ustekinumab) are approved and safe medications when used under medical prescription and monitoring. Main risks include opportunistic infections, reactivation of latent tuberculosis (mandatory screening before starting) and, rarely, infusion reactions. The risk-benefit profile is favorable in most patients with moderate to severe UC refractory to other therapies.
Yes. Patients with extensive UC (pancolitis) and long-standing disease (> 8-10 years) have an increased risk of colorectal cancer. For this reason, periodic colonoscopic surveillance is recommended — generally every 1-3 years after 8-10 years of extensive disease. Adequate inflammation control reduces this risk.
Yes, in remission. Regular physical activity benefits IBD patients in remission — it reduces stress, improves mood, preserves muscle mass, and may have a systemic anti-inflammatory effect. During flares, exercise should be adapted to tolerance. The physician can guide the appropriate activity level for each phase of the disease.
Yes. Most women with UC in remission have uncomplicated pregnancies. Active disease during pregnancy is associated with higher risk of preterm delivery and low birth weight — só pregnancy planning during remission is essential. Some UC medications are safe in pregnancy; others must be substituted. Joint follow-up with a gastroenterologist and obstetrician is essential.
Duration varies widely. With appropriate treatment, mild to moderate flares typically enter remission within 2-6 weeks. Severe flares may require hospitalization and inpatient care for days to weeks. Without treatment, flares tend to be prolonged and progress to complications. Starting correct treatment early is the most important factor for shortening and controlling the flare.
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