Ischemic colitis (IC) is the most common form of intestinal ischemia, resulting from sudden, often transient reduction in mesenteric blood flow to the colon, predominantly affecting watershed areas (splenic flexure/Griffith point and rectosigmoid junction/Sudeck point). [1-2] It is the second most common cause of colonic hematochezia, accounting for up to 19% of lower GI bleeding. [2] Median age is 70 years, with a female predominance (F:M ~3.5:1). [1][3] Over 95% of cases are non-occlusive in etiology. [1]
The following figure demonstrates the classic radiographic and endoscopic appearance of ischemic colitis, including thumbprinting on barium enema and the ulcerated, hemorrhagic mucosal pattern on colonoscopy:
1. History
- Classic triad (temporal sequence): Sudden cramping left lower abdominal pain → urgent desire to defecate → passage of bright red/maroon blood or bloody diarrhea within 24 hours of pain onset [5]
- Pain is typically mild-to-moderate and precedes bleeding [5]
- Most common symptoms: abdominal pain (87%), rectal bleeding (84%), diarrhea (56%), nausea (30%) [5]
- Symptom onset is rapid — manifests within hours, unlike IBD or infectious colitis [6]
- Ask about recent hypotensive episodes, dehydration, recent surgery (especially aortic), recent colonoscopy prep, new medications, constipation, illicit drug use (cocaine, methamphetamine)
- Important negative: Isolated right colon ischemia (IRCI) often presents with pain but without rectal bleeding (only 25–46% have hematochezia) — maintain suspicion in patients with acute severe abdominal pain, especially with dialysis, sepsis, or shock [5]
2. Alarm Features
- Peritoneal signs on exam (guarding, rigidity, rebound)
- Hemodynamic instability: hypotension (SBP <90 mmHg), tachycardia (HR >100)
- Abdominal pain without rectal bleeding (suggests IRCI or acute mesenteric ischemia [AMI])
- Isolated right-sided colitis — 48.4% adverse outcome rate vs. 12.1% for non-right-sided; >50% require surgery [2][7]
- Pancolonic involvement — mortality rate ~21% [1]
- Pneumatosis intestinalis or portal venous gas on CT (transmural infarction) [5]
- Gangrene on colonoscopy (blue-black nodules, dusky mucosa) [6]
- Lactic acidosis, rising WBC, worsening pain despite treatment
- Features suggesting AMI: atrial fibrillation + severe pain + IRCI [5]
3. Medications
Contributing medications
- Constipation-inducing drugs (opioids, anticholinergics, calcium channel blockers) — most common precipitant in older adults [1]
- Diuretics, digoxin, NSAIDs [1]
- Vasoconstrictors: triptans (naratriptan, sumatriptan), ergotamines, vasopressors [8]
- IBS drugs: alosetron, tegaserod (highest reported ORs for drug-induced IC) [8]
- Immunomodulators, antipsychotics, oral contraceptives/hormonal therapy [5][9]
- Illicit drugs: cocaine, methamphetamine [5]
- Colonoscopy prep agents (PEG 3350, sodium phosphate/Osmoprep) [1][8]
Treatment medications
- IV fluids for resuscitation
- Broad-spectrum antibiotics for moderate-to-severe disease (e.g., ciprofloxacin + metronidazole or piperacillin-tazobactam) [5]
- No antibiotics needed for mild disease [1][5]
Contraindicated/avoid
- NSAIDs, vasoconstrictors, opioids (worsen ischemia/constipation)
- Glucocorticoids are not recommended for IC (unless treating underlying vasculitis) [5]
- Antithrombotic therapy is not needed in >95% of cases (non-occlusive etiology) [1]
4. Diet
- Acute phase: NPO / bowel rest with IV hydration until symptoms improve [5]
- Advance to clear liquids, then low-residue diet as tolerated
- Long-term: Adequate hydration to prevent dehydration-triggered recurrence; high-fiber diet to prevent constipation [1]
- Avoid excessive caffeine or alcohol that may contribute to dehydration
5. Review of Systems
- GI: Abdominal pain character/location, bloody vs. non-bloody diarrhea, nausea/vomiting, constipation history
- Cardiovascular: Chest pain, palpitations, dyspnea (screen for MI, arrhythmia, CHF)
- Vascular: Claudication, prior DVT/PE (peripheral arterial disease, hypercoagulable state)
- Constitutional: Fever, dizziness, syncope (6% present with syncope) [5]
- Urologic: Decreased urine output (dehydration, shock)
- Neurologic: Altered mental status (sepsis, hypoperfusion)
6. Collateral History and Family History
- Confirm medication list with pharmacy/family — especially recent additions or dose changes of antihypertensives, opioids, or constipation-inducing agents
- Recent procedures: aortic surgery, cardiac catheterization, colonoscopy [1]
- Recent illness with dehydration, hypotension, or prolonged immobility
- Family history: Hypercoagulable disorders (Factor V Leiden, antiphospholipid syndrome) — more relevant in younger patients or those with recurrent IC [1]
- Social history: cocaine/methamphetamine use, smoking, functional status
7. Risk Factors
- Age ≥65 years (3.7× relative risk at age 70–79 vs. 50–59) [1]
- Female sex [1][3]
- Cardiovascular disease: Hypertension, atrial fibrillation, CHF, coronary artery disease [1][10]
- Peripheral arterial disease (OR 4.1) [10]
- Diabetes mellitus (OR 1.76) [10]
- Dyslipidemia (OR 2.12) [10]
- COPD [1][11]
- Chronic kidney disease / dialysis [5]
- Constipation — most common precipitant in elderly [1]
- Polypharmacy — especially constipation-inducing drugs, diuretics, NSAIDs [1]
- Recent surgery: Aortoiliac instrumentation, cardiopulmonary bypass [1]
- Shock/sepsis/hypovolemia [2]
- Hypercoagulable states (younger patients) [1]
8. Differential Diagnosis
- Acute mesenteric ischemia (AMI) — cannot-miss; more severe, involves small bowel, pain out of proportion to exam; CTA required if suspected [5]
- Infectious colitis — C. difficile, E. coli O157:H7, Salmonella, Shigella, CMV; stool studies differentiate [1][6]
- Inflammatory bowel disease (Crohn's, UC) — chronic/relapsing course, younger patients, different distribution; biopsy helps distinguish [6]
- Diverticulitis — typically painless bleeding or LLQ pain with fever; CT differentiates [5]
- Colorectal malignancy — obstructing lesion; colonoscopy with biopsy [1]
- Radiation colitis — history of pelvic radiation
- Drug-induced colitis — NSAIDs, fibrates; histologically milder inflammation than IC [12]
- Distinguishing feature of IC: Abrupt onset (hours), segmental distribution with sharp demarcation, watershed area involvement, rectal sparing [2][6]
9. Past Medical History
- Prior episodes of ischemic colitis (5-year recurrence rate 7–13%) [1]
- Cardiovascular disease history (MI, CHF, atrial fibrillation, PVD)
- Prior aortic or cardiac surgery
- History of hypercoagulable disorders or DVT/PE
- Chronic constipation
- Dialysis dependence
- Prior abdominal surgeries (adhesions, altered anatomy)
10. Physical Exam
- Vitals: Hypotension (SBP <90), tachycardia (HR >100) — both predictors of severity [5][7]
- Abdomen: Mild-to-moderate tenderness over the involved segment (typically LLQ); distension
- Peritoneal signs (guarding, rigidity, rebound) → emergent surgical consultation [5]
- Rectal exam: Gross blood, maroon stool; assess for masses
- Cardiovascular: Irregular rhythm (atrial fibrillation), murmurs, signs of CHF
- Peripheral vascular: Diminished pulses, signs of PVD
- Skin: Mottling, livedo reticularis (vasculitis), signs of dehydration
11. Lab Studies
- CBC: Leukocytosis (WBC >15 × 10⁹/L is a severity marker); anemia (Hgb <12 g/dL) [5]
- BMP: BUN >20 mg/dL (severity marker), sodium <136 mEq/L, creatinine (renal function) [5]
- Lactate: Elevated suggests tissue hypoperfusion/necrosis [13]
- LDH: >350 U/L is a severity marker [5]
- CRP / Procalcitonin: Elevated; may help triage severity [11]
- D-dimer: May predict severity [11]
- Lactic acid: Critical for ruling out bowel necrosis
- Coagulation studies: PT/INR, PTT
- Blood cultures: If sepsis suspected
- Stool studies: C. difficile toxin, stool culture, ova and parasites — to rule out infectious colitis [1]
- Type and screen if significant bleeding
- Thrombophilia workup (antiphospholipid antibody, Factor V Leiden): Consider in younger patients or recurrent IC; generally not needed in elderly [1]
12. Imaging
First-line: CT abdomen/pelvis with IV and oral contrast [5]
- Findings: Segmental bowel wall thickening, thumbprinting, pericolonic fat stranding ± ascites [5]
- These findings are suggestive but not specific — also seen in diverticulitis, IBD, infectious colitis [5]
CT Angiography (CTA): Perform if: [5]
- Isolated right colon ischemia (IRCI) suspected
- AMI cannot be excluded
- Severe presentation
Ominous CT findings
- Pneumatosis intestinalis and portomesenteric venous gas → transmural infarction [5]
- Free intraperitoneal fluid (predictor of need for surgery) [13]
When imaging is unnecessary: Mild, classic left-sided presentation in a stable patient may proceed directly to colonoscopy [5]
Arteriography: Rarely needed; consider if CTA negative but AMI still suspected [5]
13. Special Tests
Colonoscopy (gold standard for diagnosis): [5][14]
- Perform within 48 hours of presentation in absence of peritoneal signs [5]
- Use minimal insufflation, preferably CO₂ [1][5]
- Obtain biopsies unless gangrene is present [5]
- Do NOT perform if peritoneal signs, pneumatosis, or evidence of gangrene on CT [5]
Key endoscopic findings: [5-6]
- Erythema (83.7%), edema (69.9%), friability (42.6%)
- Superficial ulcerations including the colon single-stripe sign (CSSS) — a linear ulcer ≥5 cm along the longitudinal axis of the left colon; indicates milder disease with better prognosis (0% surgery vs. 27% for circumferential disease) [5]
- Deep ulcerations (21.7%), blue-black nodules suggestive of gangrene (5.5%) [5]
- Segmental distribution with abrupt transition between normal and abnormal mucosa [2]
- Rectal sparing (dual blood supply) [2]
Histopathology: Mucosal/submucosal hemorrhage, edema, capillary thrombi, neutrophil infiltration; pathognomonic ghost cells rarely observed [6]
Severity scoring (ACG proposed classification): [5]
- Mild: Typical symptoms, segmental (not right-sided), no risk factors for poor outcome
- Moderate: ≤3 of: male sex, SBP <90, HR >100, pain without bleeding, BUN >20, Hgb <12, LDH >350, Na <136, WBC >15K, mucosal ulceration on colonoscopy
- Severe: >3 of the above OR peritoneal signs, pneumatosis, gangrene, pancolonic/IRCI distribution
14. ECG
- Obtain ECG in all patients to evaluate for:
- Atrial fibrillation — associated with thromboembolic mesenteric ischemia [1-2]
- Acute MI or ischemia (may be the precipitating event) [1]
- Arrhythmias contributing to low-flow state
- Continuous telemetry monitoring for moderate-to-severe disease
15. Assessment
- IC is self-limited in the majority of cases, resolving with supportive care [1][5]
- 15% may develop bowel necrosis or ischemic strictures [1]
- Mortality: Overall 8–10%; rises to 21% with right-sided or pancolonic involvement; surgical mortality ~39% [1-2][5]
- 5-year recurrence rate: 7–13% [1]
- Atypical presentations to recognize: IRCI without bleeding, post-surgical IC (especially after aortic surgery), young patients with drug-induced or hypercoagulable etiologies [1][5]
16. Treatment Plan
Mild disease (majority of patients)
- Bowel rest (NPO), IV fluid resuscitation [5]
- Discontinue offending medications (NSAIDs, vasoconstrictors, constipation-inducing drugs) [1]
- Treat precipitating conditions (dehydration, CHF, arrhythmia)
- Serial abdominal exams, monitor pain/fever/bleeding/WBC [1]
- No antibiotics needed for mild disease [1]
- Advance diet as symptoms improve
Moderate disease
- All of the above PLUS:
- Broad-spectrum antibiotics (e.g., ciprofloxacin + metronidazole, or piperacillin-tazobactam) [5]
- Surgical consultation [5]
- Serial labs (CBC, lactate, BMP)
Severe disease
- Emergent surgical consultation [5]
- Aggressive resuscitation, ICU admission
- Broad-spectrum antibiotics
- Surgery indicated for: peritoneal signs, pneumatosis/portal venous gas, gangrene on colonoscopy, clinical deterioration despite medical management, pancolonic or IRCI with hemodynamic instability [5]
- Surgical options: segmental colectomy, subtotal/total colectomy with diverting stoma [5]
Anticoagulation: Only if mesenteric venous thrombus or thromboembolism identified [1]
17. Disposition
Admit (most patients presenting to ED): [5]
- Hemodynamic instability or need for IV resuscitation
- Moderate or severe disease by ACG criteria
- Inability to tolerate oral intake
- Significant comorbidities (elderly, CHF, CKD, COPD)
- Need for colonoscopy within 48 hours
- Right-sided or pancolonic involvement
ICU admission
Observation/short stay
Discharge (select cases)
- Mild, self-limited symptoms that have resolved
- Tolerating oral intake, stable vitals
- Reliable outpatient follow-up with GI within 1–2 days
Surgical consultation triggers
- Any moderate or severe disease [5]
- Right-sided or pancolonic involvement [2]
- Clinical deterioration despite conservative management [5]
- Persistent symptoms >2–3 weeks or protein-losing colopathy [5]
- Recurrent sepsis after apparent recovery [5]
18. Follow Up / Return Precautions
Follow-up timing
- GI follow-up within 1–2 weeks after discharge for mild disease
- Colonoscopy with biopsy if not performed during admission (to exclude malignancy, IBD, infection) [1]
- Repeat colonoscopy in 1–2 months to assess healing and rule out underlying lesion
Return precautions — instruct patients to return immediately for:
- Worsening or recurrent abdominal pain
- Increased or recurrent bloody stools
- Fever, chills, rigors
- Dizziness, lightheadedness, syncope
- Inability to tolerate oral fluids
Patient counseling
- Avoid dehydration — maintain adequate fluid intake, especially during illness [1]
- Avoid constipation — use stool softeners, adequate fiber [1]
- Avoid overtreatment of hypertension — particularly during acute illness (risk of hypoperfusion) [1]
- Review and minimize unnecessary medications that predispose to IC [1]
- Expected recovery: Most episodes resolve within 1–2 weeks without sequelae [5]
- Recurrence risk: ~7–13% over 5 years; identify and modify individual risk factors (arrhythmia, cardiovascular disease, vasoactive drugs) [1-2]
References
1. Colorectal Cancer Screening and Surveillance and Other Colon Conditions in the Older Adult. — Calderwood AH, Shaukat A. The American Journal of Gastroenterology. 2025.
2. Gastrointestinal Surgical Emergencies Textbook. — Ashley E. Aaron, Andrea Amabile, Ciro Andolfi, et al American College of Surgeons (2021). 2021.
3. Analysis of Clinical Characteristics of 117 Cases of Ischemic Colitis. — Hong SS. BMC Gastroenterology. 2025.
4. Intestinal ischemia and vasculitides. — Juan‐Ramón Malagelada, Carolina Malagelada Yamada's Atlas of Gastroenterology. 2022.
5. ACG Clinical Guideline: Epidemiology, Risk Factors, Patterns of Presentation, Diagnosis, and Management of Colon Ischemia (CI). — Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ. The American Journal of Gastroenterology. 2015.
6. Differential Diagnosis of Inflammatory Bowel Disease: Imitations and Complications. — Gecse KB, Vermeire S. The Lancet. Gastroenterology & Hepatology. 2018.
7. The Predictors of the Severity of Ischaemic Colitis: A Systematic Review of 2823 Patients From 22 Studies. — Sun D, Wang C, Yang L, Liu M, Chen F. Colorectal Disease : The Official Journal of the Association of Coloproctology of Great Britain and Ireland. 2016.
8. Assessing the Association Between Drug Use and Ischaemic Colitis: A Retrospective Pharmacovigilance Study Using FDA Adverse Event Data. — An J, Wu K, Wu T, et al. BMJ Open. 2025.
9. Ischemic Colitis as a Complication of Medication Use: An Analysis of the Federal Adverse Event Reporting System. — Bielefeldt K. Digestive Diseases and Sciences. 2016.
10. Risk Factors Associated With the Development of Ischemic Colitis. — Cubiella Fernández J, Núñez Calvo L, González Vázquez E, et al. World Journal of Gastroenterology. 2010.
11. Bad Blood: Ischemic Conditions of the Large Bowel. — Rizwan R, Feuerstadt P. Current Opinion in Gastroenterology. 2022.
12. Triggers of Histologically Suspected Drug-Induced Colitis. — Brechmann T, Günther K, Neid M, Schmiegel W, Tannapfel A. World Journal of Gastroenterology. 2019.
13. Ischemic Colitis: Risk Factors for Eventual Surgery. — Paterno F, McGillicuddy EA, Schuster KM, Longo WE. American Journal of Surgery. 2010.
14. Diagnostic Methods and Drug Therapies in Patients With Ischemic Colitis. — Xu Y, Xiong L, Li Y, Jiang X, Xiong Z. International Journal of Colorectal Disease. 2021.