Gastrointestinal

Ischemic colitis: diagnosis and supportive management

Clinical Overview and When to Suspect Ischemic Colitis

— Most common form of GI ischemia; incidence rises sharply after age 60

— Female predominance; strong association with cardiovascular comorbidity, atrial fibrillation, CKD, COPD, IBS, and constipation

— "Watershed" zones (splenic flexure — Griffith point; rectosigmoid — Sudeck point) are most vulnerable

— Rectum is usually spared because of dual blood supply (IMA + internal iliac)

— Triggers: hypotension/shock, dehydration, vasoconstrictors, recent cardiac/vascular surgery, hypercoagulability, cocaine/methamphetamine, pseudoephedrine, NSAIDs, digoxin, hormone therapy, chemotherapy (taxanes), and recent endurance exercise (runner's colitis)

— Older outpatient with crampy LLQ abdominal pain followed within 24 hours by bloody or maroon diarrhea, mild tenderness, and stable vitals

— Postoperative AAA repair patient with new bloody stool — assume IC until proven otherwise

— Hemodialysis patient post intradialytic hypotension with new abdominal pain

Board pearl: The triad of sudden crampy abdominal pain + urge to defecate + bloody diarrhea in an older adult with vascular risk factors should anchor you on ischemic colitis before infectious or inflammatory etiologies. Pain out of proportion to exam favors small-bowel mesenteric ischemia, not IC.

Definition: Ischemic colitis (IC) is a transient, low-flow injury to the colonic mucosa from hypoperfusion of small mesenteric vessels — not typically a large-vessel embolic/thrombotic event like acute mesenteric ischemia of the small bowel.

Epidemiology and demographics:

Pathophysiology snapshot:

When to suspect (classic Step 3 vignette):

Severity spectrum: ~85% non-gangrenous and self-limited; ~15% develop gangrene, perforation, or chronic stricture

Right-sided IC (isolated right colon ischemia — IRCI): worse prognosis, often shares SMA territory, higher mortality, more often requires surgery — must be distinguished from acute mesenteric ischemia.

Presentation Patterns and Key History

— Abrupt onset crampy abdominal pain, typically left-sided (splenic flexure/descending/sigmoid)

— Urgent defecation within hours

— Mild-to-moderate hematochezia or bloody diarrhea within 24 hours of pain

— Pain is usually mild-to-moderate and proportionate to exam findings

— Severe, persistent pain out of proportion → suspect transmural/gangrenous IC or acute mesenteric ischemia

— Isolated right colon ischemia: vague periumbilical pain, less bleeding, more nausea — higher mortality

— Fulminant pancolitis variant: rare, often immunocompromised, mimics toxic colitis

— Recent hypotensive event: sepsis, MI, GI bleed, dialysis, marathon, vigorous exercise

— Recent surgery: AAA repair (IMA ligation), cardiac bypass, colorectal surgery

— Medications: vasopressors, digoxin, diuretics, NSAIDs, oral contraceptives/HRT, antipsychotics with anticholinergic effects, opioids, pseudoephedrine, sumatriptan, alosetron, tegaserod, interferon, taxanes, immunotherapy

— Substances: cocaine, methamphetamine, energy drinks

— Constipation history or recent colonoscopy prep

— Hypercoagulable risk in young patients: factor V Leiden, protein C/S deficiency, antiphospholipid syndrome, sickle cell, OCPs

— Anticoagulation use → bleeding severity assessment

— Immunosuppression → broaden infectious differential, lower threshold to admit

— Age <40 with IC → push hypercoagulable + cocaine + vasculitis workup

Key distinction: Acute mesenteric ischemia presents with severe pain out of proportion, minimal early bleeding, and often atrial fibrillation; ischemic colitis presents with milder pain plus early bloody diarrhea. Confusing these two on Step 3 changes both imaging and surgical urgency.

Classic symptom tempo:

Atypical / severe patterns to flag:

Targeted history — the "why now" question is the exam's favorite:

Comorbidity scan: CAD, PAD, atrial fibrillation, HF, CKD, COPD, diabetes, IBS, prior IC, vasculitis (SLE, PAN, Behçet)

Red-flag history that changes triage:

Physical Exam Findings and Hemodynamic Assessment

— Most patients with non-gangrenous IC look uncomfortable but not toxic

— Toxic appearance, rigors, or altered mental status → suspect transmural ischemia, gangrene, perforation, or bacteremia

— HR, BP (orthostatics if volume-depleted), temperature, RR, SpO2, and lactate-driven reassessment

— Tachycardia + fever + hypotension in IC = systemic inflammatory response; escalate care

— Atrial fibrillation on telemetry — shifts differential toward embolic small-bowel ischemia

— Mild-to-moderate tenderness, typically LLQ; bowel sounds usually present

— Voluntary guarding may be present; rebound, rigidity, or involuntary guarding → peritonitis / surgical abdomen

— Distension suggests ileus or megacolon

— Right-sided tenderness in IRCI overlaps with appendicitis, cholecystitis, SMA syndromes

— Gross blood or maroon stool common; frank melena is unusual (favors upper GI source)

— Empty vault with tenderness on digital exam can suggest higher colonic lesion

— Irregularly irregular pulse → assess for embolic source

— Carotid bruits, AAA, diminished femoral pulses → diffuse atherosclerosis raises IC pretest probability

— Volume status: JVP, mucous membranes, capillary refill, urine output — most IC patients are volume-down

— Livedo reticularis, purpura → think vasculitis, cholesterol emboli, antiphospholipid syndrome

— Cold mottled feet post-cardiac cath → embolic showering

Step 3 management: At first encounter, decide in minutes whether this is mild IC (outpatient candidate with oral hydration and serial exams) vs moderate IC (admit for IV fluids, bowel rest, antibiotics) vs severe IC (NPO, fluid resuscitate, broad antibiotics, surgical consult, ICU) — driven primarily by peritoneal signs, hemodynamics, lactate, and CT severity. A normotensive, afebrile patient with a soft abdomen and minor hematochezia is the prototype for ambulatory observation.

General appearance:

Vital signs to document and trend:

Abdominal exam:

Rectal exam:

Cardiopulmonary and vascular:

Skin and extremities:

Diagnostic Workup — Initial Labs, Imaging, ECG, Biomarkers

— CBC: leukocytosis common; Hgb to gauge bleeding severity

— BMP: AKI from volume depletion; bicarbonate gap suggests ischemia severity

— Lactate: elevation suggests transmural ischemia — sensitive but not specific

— LFTs, lipase: rule out competing intra-abdominal pathology

— Coagulation panel, type and screen if bleeding significant

— CRP: nonspecific but trended for severity

— Stool studies: C. difficile toxin, enteric culture, E. coli O157:H7, ova/parasites, Shiga toxin — IC and infectious colitis frequently coexist on the differential, and you cannot skip this on the exam

— Blood cultures if febrile or septic-appearing

— 12-lead ECG: detect atrial fibrillation (embolic AMI source) and acute ischemia (low-flow trigger)

— Troponin if hypotension or chest symptoms — concurrent MI is common in older IC patients

— CT abdomen/pelvis with IV contrast is the initial test of choice

— Findings: segmental bowel wall thickening, "thumbprinting" from submucosal edema, pericolonic stranding, often at splenic flexure or rectosigmoid

— Pneumatosis coli, portomesenteric venous gas, or pneumoperitoneum → transmural necrosis/perforation, surgical emergency

— CT angiography indicated if mesenteric ischemia (small bowel) cannot be excluded or right colon involved

CCS pearl: On a CCS case of LLQ pain + bloody diarrhea in a 72-year-old, your high-yield opening orders are: IV access, NS bolus, NPO, CBC, BMP, lactate, coags, type and screen, stool studies including C. difficile, blood cultures if febrile, ECG, and CT abdomen/pelvis with IV contrast — then advance the clock and reassess.

Laboratory panel (obtain on every suspected IC patient):

ECG and cardiac workup:

Imaging — first line:

What CT does NOT do: confirm the diagnosis definitively — endoscopy remains the gold standard for non-emergent confirmation

Plain films: limited utility; obtain only if perforation suspected and CT unavailable — look for free air or thumbprinting

Diagnostic Workup — Advanced or Confirmatory Studies

— Perform within 48 hours of presentation in patients without peritonitis, perforation, or gangrene on CT

— Minimal air insufflation and limited extent (to most proximal diseased segment) to avoid perforating ischemic mucosa

— Findings: pale mucosa, petechial hemorrhages, hemorrhagic nodules ("thumbprints" endoscopically), segmental erythema, ulcerations, and the pathognomonic single linear ulcer along the antimesenteric border ("single-stripe sign")

— Biopsy from edge of involved mucosa: ghost cells, mucosal infarction, crypt withering, hyalinized lamina propria, hemosiderin-laden macrophages

— Rectal sparing is typical; pancolitis or rectal involvement should prompt reconsideration

— Indicated when isolated right colon ischemia is identified, or when small-bowel mesenteric ischemia cannot be excluded

— Right colon shares SMA distribution; IRCI patients often have concomitant SMA disease and benefit from vascular assessment

— Hypercoagulable panel: factor V Leiden, prothrombin G20210A, protein C/S, antithrombin III, antiphospholipid antibodies, JAK2

— Urine toxicology for cocaine/amphetamines

— Vasculitis screen: ANA, ANCA, complement, hepatitis serologies

— Echocardiogram if embolic source suspected

Board pearl: The "single-stripe sign" — a single longitudinal ulcer along the antimesenteric colon — is a high-yield endoscopic finding nearly pathognomonic for ischemic colitis and a favorite exam image.

Colonoscopy — diagnostic gold standard:

Flexible sigmoidoscopy: acceptable alternative when splenic flexure/sigmoid involvement is suspected and full prep is contraindicated

Contraindications to endoscopy: peritonitis, free air, hemodynamic instability, suspected gangrene — go to OR instead

CT/MR angiography:

Workup in young patients (<40) or recurrent IC:

Differentiating from IBD on biopsy: absence of chronic features (no crypt distortion, no granulomas), presence of hemosiderin and ghost cells favor IC

Risk Stratification and First-Line Management Logic

— Mild IC: segmental colitis, no high-risk features, no peritoneal signs, stable vitals, isolated to left colon → outpatient or short observation feasible

— Moderate IC: ≥3 of: male sex, hypotension (SBP <90), tachycardia, abdominal pain without rectal bleeding, BUN >20, Hgb <12, LDH >350, Na <136, WBC >15, colonic wall thickening, right colon involvement → admit

— Severe IC: any of peritonitis, pneumatosis, portal venous gas, gangrene on endoscopy, isolated right colon ischemia with multi-organ failure, pancolonic involvement → ICU + surgery consult

— Right-sided / pancolonic involvement

— Male sex

— Lack of rectal bleeding (paradoxically — implies transmural rather than mucosal)

— Tachycardia, hypotension, peritoneal signs

— Elevated lactate, LDH, WBC; low Hgb, Na, albumin

— CKD, HF, COPD, vasopressor use

— Bowel rest (NPO initially; advance as tolerated within 24–48 h)

— IV fluid resuscitation with isotonic crystalloid; target euvolemia and adequate urine output

— Optimize perfusion: discontinue vasoconstrictors, NSAIDs, digoxin if feasible; treat arrhythmias; replete electrolytes

— Empiric antibiotics: broad-spectrum coverage (ceftriaxone + metronidazole, or piperacillin-tazobactam) for moderate-to-severe IC — animal data suggest reduced bacterial translocation; not required for mild cases per some guidelines but commonly given on the exam

— Serial abdominal exams every 4–6 hours

— VTE prophylaxis with mechanical means; pharmacologic if bleeding controlled

— Pain control: avoid vasoconstrictive agents and opioid overuse that masks peritonitis

Step 3 management: Mild IC = oral hydration, clear liquids advancing, hold offending meds, follow-up in 1–2 weeks with repeat sigmoidoscopy at 2–3 months only if symptoms persist. Moderate-severe IC = admit, IV fluids, NPO, empiric antibiotics, surgical consult on standby.

Severity classification (ACG 2015 framework, adapted):

Risk factors for poor outcome to memorize:

First-line management pillars (non-gangrenous IC):

Pharmacotherapy — First-Line Drug Regimen

— Goal: cover enteric Gram-negatives and anaerobes to reduce bacterial translocation across compromised mucosa

— Ceftriaxone 1–2 g IV daily + metronidazole 500 mg IV q8h — standard combination

— Alternative monotherapy: piperacillin-tazobactam 3.375 g IV q6h or 4.5 g q8h

— Penicillin-allergic: ciprofloxacin + metronidazole

— Duration: 3–7 days, longer if perforation or abscess

— Mild IC: antibiotics often omitted in current guidelines but frequently still tested as standard inpatient practice

— Lactated Ringer's or normal saline; avoid overload in HF/CKD

— Reassess every 4 hours; target MAP ≥65, UOP ≥0.5 mL/kg/h

— Vasoconstrictors: pseudoephedrine, triptans, ergots, cocaine

— Digoxin (mesenteric vasoconstriction)

— NSAIDs

— Diuretics if volume-depleted

— Estrogen-containing OCPs/HRT (especially in young women with IC)

— Constipating agents: anticholinergics, opioids when possible

— Vasopressin and high-dose norepinephrine if alternatives exist; switch to dobutamine or low-dose pressors if perfusion is the limiting issue

— Acetaminophen first-line

— Low-dose opioids cautiously; avoid masking peritonitis

— Avoid NSAIDs

— Most IC is not thromboembolic — routine anticoagulation is NOT indicated

— Exception: confirmed hypercoagulable state, mesenteric vein thrombosis, or coexisting atrial fibrillation with embolic risk — then anticoagulate after bleeding controlled

Board pearl: Steroids worsen outcomes in IC even when biopsy shows inflammation; never give empiric steroids for "possible colitis" until you have excluded ischemia. This is a classic Step 3 trap when distinguishing IC from IBD flare.

Antibiotics (moderate-to-severe IC):

IV fluids:

Medications to STOP (high-yield):

Pain control:

PPI: consider if GI bleeding or stress ulcer risk

Anticoagulation paradox:

Vasodilators (papaverine, glucagon): investigational; not standard for IC

Corticosteroids: AVOID — increase perforation risk and obscure exam

Procedures, Surgical Management, and Endoscopic Considerations

— Peritonitis on exam

— Pneumatosis intestinalis with clinical deterioration

— Portomesenteric venous gas

— Pneumoperitoneum / perforation

— Massive ongoing hemorrhage

— Fulminant colitis with sepsis

— Gangrene on endoscopy

— Failure to improve after 48–72 hours of optimal medical therapy

— Isolated right colon ischemia with hemodynamic instability

— Segmental colectomy with primary anastomosis or end colostomy (Hartmann's procedure) depending on contamination, hemodynamics, and tissue viability

— Intraoperative assessment of bowel viability with serosal inspection, Doppler, or fluorescence; avoid leaving marginally viable bowel — second-look laparotomy in 24–48 h is acceptable

— Mortality of emergent colectomy for gangrenous IC: 30–60%

— Endoscopic balloon dilation for short, symptomatic ischemic strictures (3–6 weeks post-event, after complete healing)

— Elective segmental resection for chronic ischemic strictures causing obstruction or persistent segmental colitis

— Avoid stenting ischemic strictures — higher perforation risk

— CO2 insufflation preferred over air to reduce barotrauma

— Limited extent; do not push past visible disease

— Biopsies from ulcer edges, not base

— Sigmoidoscopy at 48–72 h post-op if bloody diarrhea or unexplained leukocytosis

— Mucosal-only ischemia → supportive care

— Transmural → re-operation

— IMA reimplantation considerations during initial AAA repair reduce subsequent IC

CCS pearl: If your CCS patient with IC develops a rigid abdomen, rising lactate, free air on repeat imaging, or refractory acidosis on hospital day 2 — call general surgery STAT, type and cross, broaden antibiotics, transfer to ICU, and prepare for emergent laparotomy. Delays in escalation are scored unfavorably.

Indications for urgent surgical consultation:

Operative approach:

Post-acute interventions:

Endoscopy logistics in acute phase:

Special procedural scenario — post-AAA repair IC:

Special Populations — Elderly and Renal/Hepatic Impairment

— Mean age at presentation ~70; prevalence rises with each decade

— Higher burden of CAD, PAD, atrial fibrillation, polypharmacy — all converge on hypoperfusion risk

— Atypical presentation common: vague pain, confusion, decreased oral intake, falls — IC may be diagnosed only after delirium workup

— Higher complication rates: perforation, stricture, mortality

— Pain may be blunted — do not rely on classic "out of proportion" framing

— Polypharmacy review is therapeutic: hold digoxin, diuretics, anticholinergics, NSAIDs, vasoconstrictive decongestants, opioids when possible

— Intradialytic hypotension is a leading IC trigger

— Coordinate with nephrology to reduce ultrafiltration rates, switch to longer/gentler sessions, add midodrine cautiously

— Avoid nephrotoxic antibiotics; renal-dose all therapy — piperacillin-tazobactam, ceftriaxone (no adjustment), metronidazole (mild reduction in severe disease), ciprofloxacin (dose-adjusted)

— Contrast-enhanced CT: weigh contrast-induced AKI risk against diagnostic necessity — modern iso-osmolar contrast in adequately hydrated patients is generally acceptable

— Cirrhotic patients have splanchnic vasodilation but paradoxical low effective volume — increased IC susceptibility, especially with SBP, variceal bleed, or large-volume paracentesis without albumin

— Metronidazole accumulates in severe cirrhosis — reduce dose

— Avoid NSAIDs absolutely; opioid sensitivity heightened

— Coagulopathy complicates endoscopic biopsy — discuss with hepatology and GI

— Digoxin, loop diuretics if volume-depleted, NSAIDs, anticholinergics, calcium channel blockers contributing to hypotension, alpha-blockers, OTC pseudoephedrine

Step 3 management: In any elderly IC patient, your discharge plan must include a medication reconciliation explicitly listing held/discontinued agents and a written plan for restart vs permanent discontinuation, communicated to the primary care physician — this is both a quality measure and a Step 3 favorite.

Elderly (the modal IC patient):

CKD and dialysis patients:

Hepatic impairment:

Polypharmacy red list to deprescribe in the elderly with IC:

Special Populations — Young Adults, Pregnancy, and Other Subgroups

— Cocaine and methamphetamine — leading cause in young patients

— Estrogen-containing OCPs and HRT — disproportionate IC risk, especially with smoking

— Long-distance runners and endurance athletes — splanchnic shunting + dehydration ("runner's colitis")

— Hypercoagulable states: factor V Leiden, prothrombin gene mutation, antiphospholipid syndrome, protein C/S deficiency

— Vasculitis: SLE, polyarteritis nodosa, Behçet, Henoch-Schönlein

— Sickle cell disease — microvascular occlusion

— Workup mandatory: hypercoagulable panel, urine tox, autoimmune serologies, echocardiogram if applicable

— Rare but reported, particularly third trimester or postpartum

— Hypercoagulable physiology, mechanical compression, preeclampsia, hyperemesis-related dehydration

— Imaging: prefer ultrasound and MRI without gadolinium over CT when possible

— Multidisciplinary management with OB and surgery; teratogenic considerations for medications (avoid metronidazole in first trimester when possible; ceftriaxone safe)

— VTE prophylaxis with LMWH if not actively bleeding

— Post-AAA repair: 1–7% incidence; sigmoid most affected due to IMA sacrifice

— Cardiac bypass surgery: low-flow state intraop

— Colorectal surgery: anastomotic vascular compromise

— Threshold for early sigmoidoscopy is low

— Counseling on hydration, gradual training, avoiding NSAIDs pre-run

— Usually self-limited; recurrence reduced by behavior modification

— CMV colitis, neutropenic enterocolitis (typhlitis), and C. difficile all mimic IC

— Lower threshold for endoscopy with biopsy and viral PCR

Board pearl: A young woman on combined OCPs who smokes presenting with bloody diarrhea after a marathon — the answer is ischemic colitis. Discontinue OCPs and counsel on smoking cessation as part of management.

Young adults (<40) with IC — always look for a secondary cause:

Pregnancy:

Postoperative IC (high-yield niche):

Athletes and exertional IC:

Immunocompromised patients:

Complications and Adverse Outcomes

— Gangrene and perforation (~15% of IC cases) — mortality 30–60%; presents with peritonitis, sepsis, free air on imaging

— Toxic megacolon — colonic dilation >6 cm with systemic toxicity; rare but life-threatening

— Massive lower GI hemorrhage — uncommon; consider alternative diagnoses (diverticular bleed, AVM) if severe

— Sepsis with bacterial translocation — Gram-negative bacteremia, anaerobic infection

— Acute kidney injury from hypovolemia and contrast/nephrotoxin exposure

— Concurrent acute MI in older patients — share underlying atherosclerosis and low-flow physiology

— Segmental ulcerating colitis — persistent inflammation mimicking IBD for weeks to months

— Protein-losing colopathy — hypoalbuminemia, edema

— Persistent diarrhea, fatigue, weight loss

— Ischemic strictures — fibrotic narrowing at watershed zones; present with obstructive symptoms weeks to months after acute event

— Chronic segmental colitis — recurrent abdominal pain and bleeding, may require elective resection

— Recurrent ischemic colitis — 5–10% within 5 years; recurrence prompts hypercoagulable and vascular workup

— Right-sided / pancolonic involvement

— Need for surgery

— Age >75

— Hemodialysis

— Hypotension on presentation

— Lactate >2; LDH elevated

— Comorbid CHF, COPD, CKD

— Fear of recurrence, dietary restriction, deconditioning in elderly

— Stoma adjustment for those requiring Hartmann's

Key distinction: A patient with IC who develops new obstructive symptoms 6 weeks later has an ischemic stricture, not recurrence — confirm with CT and colonoscopy, treat with endoscopic dilation for short strictures or elective resection for symptomatic long strictures. Do not restart anti-inflammatory therapy as if it were IBD.

Acute complications:

Subacute complications:

Chronic complications:

Mortality predictors:

Quality-of-life sequelae:

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Hemodynamically stable but requires IV fluids, antibiotics, NPO, serial exams

— Comorbidities precluding safe outpatient management

— Inadequate oral intake or significant bleeding requiring monitoring

— Right-sided involvement even when otherwise stable

— Hypotension requiring vasopressors despite adequate resuscitation

— Lactate >4 or progressive rise

— Multi-organ dysfunction

— Suspected gangrene, pneumatosis with clinical deterioration

— Pre/post-op status with high physiologic risk

— Massive hemorrhage requiring multiple transfusions

— At admission for any moderate-severe IC for co-management

— Immediately for peritonitis, free air, gangrene, or failure to improve at 48–72 h

— Vascular surgery if isolated right colon ischemia with mesenteric arterial disease

— All hospitalized IC patients for confirmatory colonoscopy within 48 h

— Guidance on timing of biopsy and follow-up endoscopy

— Cardiology if atrial fibrillation, ischemic cardiomyopathy, or concurrent ACS

— Hematology if recurrent or young-patient IC for thrombophilia evaluation

— Nephrology if dialysis-related or AKI complicated

— Nutrition for prolonged NPO or post-resection patients

— Age <60 (relative)

— Stable vitals, no peritonitis

— Mild segmental left-sided disease on CT

— Tolerating oral intake

— Reliable follow-up within 1–2 weeks

— Caregiver support and ability to return promptly if worsening

CCS pearl: On a CCS case, if the patient's lactate rises from 2.4 to 4.8 over 6 hours despite fluids and antibiotics, change location to ICU, call surgery, and obtain repeat CT abdomen/pelvis with contrast — do not wait for peritoneal signs. Trend lactate every 4–6 hours in moderate-severe IC.

Admit to general medical floor (typical moderate IC):

ICU admission criteria:

Surgical consultation — when to call:

GI consultation:

Other consults:

Outpatient management criteria (mild IC):

Key Differentials — Same-Category GI Causes

— Pain out of proportion to exam, often periumbilical

— Atrial fibrillation, recent MI, embolic source common

— Minimal early bleeding; bloody diarrhea is a late, ominous sign

— CT angiography is the test; intervention is embolectomy or thrombolysis

— Higher mortality (50–80%); time-critical

— Younger patients, subacute course, weeks-to-months of symptoms

— Continuous rectal involvement (UC) or skip lesions with perianal disease (Crohn)

— Biopsy shows crypt distortion, granulomas (Crohn); no ghost cells

— Responds to steroids — which are contraindicated in IC

— C. difficile — recent antibiotics, healthcare exposure, watery diarrhea ± blood; toxin PCR/EIA

— Shiga toxin–producing E. coli O157:H7 — undercooked beef, HUS risk; avoid antibiotics

— Salmonella, Shigella, Campylobacter — fever, leukocytosis, recent travel/food exposure

— CMV colitis — immunocompromised; biopsy with inclusion bodies

— Entamoeba histolytica — travel; flask-shaped ulcers

— Painless brisk hematochezia (diverticular bleed) vs LLQ pain + fever (diverticulitis)

— CT shows pericolic stranding, diverticula, occasionally abscess

— Older patient with iron deficiency, weight loss, change in bowel habits

— May coexist with or mimic chronic segmental IC stricture

— Colonoscopy with biopsy distinguishes

— History of pelvic radiation (prostate, cervical, rectal cancer)

— Telangiectasias on endoscopy; treat with argon plasma coagulation

Key distinction: On Step 3, steroids are the wrong answer for IC but the right answer for IBD; antibiotics are wrong for E. coli O157:H7 but right for moderate-severe IC and many other bacterial colitides. Match the therapy to the precisely diagnosed entity.

Acute mesenteric ischemia (AMI) of the small bowel:

Inflammatory bowel disease (IBD):

Infectious colitis:

Diverticulitis with bleeding or diverticular hemorrhage:

Colorectal malignancy:

Radiation proctocolitis:

Key Differentials — Other-Category Causes

— Acute MI with referred abdominal pain — inferior MI especially; check ECG and troponin in every elderly patient with abdominal pain

— Abdominal aortic aneurysm rupture — sudden severe pain, hypotension, pulsatile mass; bedside US

— Aortic dissection extending to mesenteric vessels

— Nephrolithiasis — colicky flank-to-groin pain, hematuria on UA

— Pyelonephritis — fever, CVA tenderness, pyuria

— Ovarian torsion or ruptured ectopic pregnancy in reproductive-age women — pelvic exam and bHCG mandatory

— Acute pancreatitis — epigastric pain, lipase elevation

— Cholecystitis/cholangitis — RUQ pain, fever, jaundice

— Mesenteric venous thrombosis — subacute pain, hypercoagulable patient; CT venous phase

— Sickle cell vaso-occlusive crisis with abdominal involvement

— Henoch-Schönlein purpura in children/young adults — palpable purpura + abdominal pain + hematuria

— DKA presenting with abdominal pain — check glucose, anion gap

— Adrenal insufficiency

— Lead poisoning, porphyria (rare)

— PID, tubo-ovarian abscess

— Endometriosis with bowel involvement

— IBS — chronic, no bleeding, normal labs

— Constipation with stercoral ulcer — can itself precipitate IC

— C. difficile pseudomembranes vs IC mucosal infarction — biopsy distinguishes; do not assume

Board pearl: Always order an ECG in elderly patients with abdominal pain. A silent inferior MI presenting as abdominal pain has cost test-takers and clinicians alike. The same patient may have BOTH an MI and ischemic colitis from the resulting low-flow state — diagnose and treat both.

Cardiovascular:

Genitourinary:

Hepatobiliary/pancreatic:

Vascular and hematologic:

Toxic/metabolic:

Pelvic and gynecologic:

Functional and benign:

Pseudomembranous appearance mimics:

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Tolerating diet (advanced from clears to regular over 24–48 h)

— Afebrile, hemodynamically stable, normalized WBC and lactate

— Pain controlled on oral acetaminophen

— Bleeding resolved or trivial

— Reliable follow-up arranged with PCP and GI

— Permanently discontinue vasoconstrictive OTCs (pseudoephedrine), recreational cocaine/amphetamines, ergots/triptans if avoidable

— Discontinue or substitute estrogen-containing OCPs/HRT — switch to progestin-only or non-hormonal contraception

— Hold and reassess digoxin, NSAIDs, diuretics, anticholinergics; restart only if benefit clearly outweighs IC recurrence risk

— Review opioids and minimize

— Address atherosclerosis: statin therapy if ASCVD risk warrants, antihypertensives to control BP without precipitating hypotension, smoking cessation counseling and pharmacotherapy

— Diabetes optimization with A1c target individualized

— Atrial fibrillation: assess CHA2DS2-VASc; if anticoagulation indicated and bleeding resolved, restart within 7–14 days of acute IC

— Aspirin is not routinely started for IC alone but continue if indicated for established ASCVD

— Avoid dual antiplatelet therapy unless cardiac indication

— Young patients, recurrent IC, family history → hematology referral

— Resume regular diet; no specific long-term restriction

— Adequate hydration, fiber for constipation prevention

— Limit caffeine, alcohol acutely

— Resume gradually; counsel endurance athletes on hydration and NSAID avoidance

Step 3 management: The single most important discharge order in IC is the explicit deprescription list sent to the PCP, paired with a follow-up colonoscopy at 2–3 months to confirm mucosal healing and rule out an underlying malignancy or IBD masquerade.

Discharge readiness checklist:

Medication reconciliation (the highest-yield discharge task):

Cardiovascular risk modification:

Antiplatelet considerations:

Hypercoagulable evaluation referral:

Dietary counseling:

Activity:

Follow-Up, Monitoring Parameters, and Rehabilitation/Counseling

— PCP visit: vitals, abdominal exam, weight, hydration status, medication reconciliation review

— Labs: CBC, BMP, CRP to confirm resolution

— Symptom screen: persistent diarrhea, bleeding, abdominal pain, obstructive symptoms

— Reassess held medications for permanent vs temporary discontinuation

— GI clinic visit

— Repeat colonoscopy at 2–3 months if symptoms persist, segmental involvement on initial exam, or to exclude underlying neoplasm — particularly if initial colonoscopy was limited

— Evaluate for stricture formation if obstructive symptoms emerge

— Resume age-appropriate colorectal cancer screening per USPSTF (45–75 average risk)

— In patients with chronic segmental ischemic colitis, annual symptom assessment and consideration of resection if recurrent

— Cardiovascular follow-up: BP, lipids, A1c, antiplatelet review

— Atrial fibrillation: ensure anticoagulation restart documented and adherence verified

— CKD/dialysis: nephrology coordination on intradialytic BP management

— HF: weight monitoring, diuretic reassessment to avoid recurrence

— Recurrence risk ~5–10% over 5 years; signs to return for: severe pain, bloody stool, fever, vomiting, inability to tolerate intake

— Hydration during illness, travel, exercise

— Smoking cessation, weight management, exercise rehabilitation

— OCP/HRT alternatives discussion with women's health

— Substance use counseling and referral if cocaine/methamphetamine involved

— Elderly post-hospitalization: physical therapy, fall prevention, nutritional rehab

— Post-colectomy patients: ostomy nurse education, body image counseling, dietary adjustment

Board pearl: A patient with prior IC who returns 8 weeks later with progressive cramping and obstipation has an ischemic stricture until proven otherwise — order CT and refer for colonoscopy with possible dilation. Do not reflexively diagnose recurrent IC.

Short-term follow-up (1–2 weeks post-discharge):

Intermediate follow-up (4–8 weeks):

Long-term surveillance:

Monitoring parameters in patients with comorbidities:

Counseling content:

Rehabilitation considerations:

Ethical, Legal, and Patient Safety Considerations

— Colonoscopy in IC carries elevated perforation risk; ensure documentation of discussion of bleeding, perforation, and need for emergent surgery

— In delirious or sedated elderly patients, identify surrogate decision-maker per state hierarchy; document capacity assessment

— For emergency surgery (gangrene), proceed under implied consent when surrogate unreachable and delay would cause harm — document attempts and rationale

— Elderly patients with gangrenous IC and multiple comorbidities face mortality of 30–60% with surgery

— Initiate palliative care consultation early; discuss code status, intubation preferences, surgical risk vs comfort-focused care

— Honor advance directives; engage healthcare proxy

— Discharge medication reconciliation errors — restarting NSAIDs, digoxin, or vasoconstrictors without indication is a sentinel patient-safety event

— Use of structured handoff (e.g., SBAR, I-PASS) when transferring care to PCP and GI follow-up

— Explicit written communication of held medications, follow-up colonoscopy schedule, and red-flag symptoms

— Medication reconciliation must occur at admission, transfer, and discharge — three checkpoints

— Cocaine/methamphetamine-induced IC: counseling and referral to substance use treatment; not directly reportable but documented

— Suspected elder neglect contributing to dehydration and IC: mandatory reporting to Adult Protective Services

— Restart anticoagulation thoughtfully; document risk-benefit and timing; communicate to outpatient team

— Disparities in access to colonoscopy and surgical care; ensure follow-up arrangements account for transportation, insurance, language

— Report nosocomial C. difficile if it complicates inpatient course; antibiotic stewardship in IC management to avoid unnecessary broad-spectrum exposure

— Time-stamped exams, lactate trends, and surgical consult times protect both patient and clinician medicolegally if deterioration occurs

Step 3 management: When a frail 88-year-old with gangrenous IC has a living will declining major surgery, the ethical answer is palliative comfort-focused care with family and palliative-care involvement, not coercive operative consent — and you must document the discussion explicitly.

Informed consent for endoscopy in the acutely ill:

Goals-of-care conversations:

Transition-of-care risks (Step 3 favorite):

Mandatory reporting and substance use:

Anticoagulation safety:

Health equity considerations:

Patient safety culture:

Documentation pearls:

High-Yield Associations and Rapid-Fire Clinical Facts

— Watershed zones: splenic flexure (Griffith point) and rectosigmoid junction (Sudeck point)

— Rectum spared due to dual blood supply (IMA + internal iliac)

— Post-AAA repair (IMA ligation)

— Cardiopulmonary bypass

— Hemodialysis hypotension

— Cocaine, methamphetamine, pseudoephedrine

— Estrogen-containing OCPs/HRT

— Long-distance running

— Digoxin, NSAIDs, diuretics

— Sepsis, GI bleed, hypovolemia

— "Thumbprinting" on CT or plain film

— Segmental wall thickening at splenic flexure

— Pneumatosis coli → transmural ischemia

— Portomesenteric venous gas → surgical emergency

— Single-stripe sign (linear ulcer on antimesenteric border)

— Hemorrhagic nodules ("endoscopic thumbprints")

— Rectal sparing

— Ghost cells, crypt withering, hemosiderin-laden macrophages, hyalinized lamina propria

— Bowel rest, IV fluids, antibiotics, hold offending meds

— No steroids

— No routine anticoagulation

— Colonoscopy within 48 h

— Surgery for peritonitis, gangrene, or failure of medical therapy

— AMI: pain out of proportion + afib

— IBD: chronic, steroid-responsive

— Infectious: stool studies

— Diverticulitis: focal LLQ + diverticula on CT

— Malignancy: weight loss, iron deficiency

Board pearl: The most commonly missed Step 3 diagnosis adjacent to IC is silent inferior MI in the elderly — always 12-lead ECG and troponin in older patients with abdominal pain.

Anatomy:

Classic triggers (memorize):

Symptom triad: sudden crampy abdominal pain → urge to defecate → bloody diarrhea within 24 h

Imaging buzzwords:

Endoscopy buzzwords:

Biopsy buzzwords:

Management buzzwords:

Mortality factors: right-sided involvement, male sex, lack of rectal bleeding, hypotension, elevated lactate

Prognosis: 85% resolve with supportive care; 15% develop gangrene/perforation/stricture; 5–10% recurrence

Differential lightning round:

Drug to permanently stop in young woman with IC: combined OCPs

Test to order in young IC patient: hypercoagulable panel, urine toxicology

Board Question Stem Patterns

Key distinction: When the stem says "pain out of proportion" → AMI; when it says "crampy pain followed by bloody diarrhea" → IC. This single phrase reliably differentiates the two on the exam.

Stem 1 — The classic: 72-year-old woman with atrial fibrillation, HTN, and HF presents with sudden crampy LLQ pain followed by bloody diarrhea. Stable vitals, mild LLQ tenderness, no peritonitis. CT shows splenic flexure wall thickening. → Answer: ischemic colitis; manage with IV fluids, bowel rest, empiric antibiotics, and colonoscopy within 48 h.

Stem 2 — Post-AAA: Patient on POD 2 after open AAA repair develops bloody diarrhea and rising WBC. → Answer: flexible sigmoidoscopy at bedside; manage based on depth of ischemia.

Stem 3 — Young woman: 32-year-old marathon runner on OCPs and a smoker presents with LLQ pain and hematochezia after a long run. → Answer: ischemic colitis; discontinue OCPs, counsel smoking cessation, hydration education.

Stem 4 — Cocaine user: 28-year-old man with chest pain, abdominal pain, and bloody diarrhea after binge cocaine use. ECG with sinus tachycardia. → Answer: cocaine-induced ischemic colitis; avoid beta-blockers, supportive care, substance use referral.

Stem 5 — Differentiating from AMI: 78-year-old with atrial fibrillation, severe periumbilical pain out of proportion, minimal exam findings, lactate 6. → Answer: acute mesenteric ischemia (small bowel), not IC; CT angiography and emergent vascular surgery.

Stem 6 — Wrong-answer trap: "Which medication should be initiated?" with options including prednisone, infliximab, mesalamine. → Answer: none of these; corticosteroids and biologics are contraindicated in IC.

Stem 7 — Stricture: Patient with prior IC returns 8 weeks later with cramping, distension, obstipation. → Answer: ischemic stricture; CT abdomen, colonoscopy, endoscopic dilation or elective resection.

Stem 8 — Surgical escalation: IC patient on hospital day 2 develops fever, rigid abdomen, free air on CT. → Answer: emergent laparotomy with segmental colectomy.

Stem 9 — Right-sided IC: Patient with isolated right colon ischemia on CT. → Answer: CT angiography to evaluate SMA; lower threshold for surgical intervention.

Stem 10 — Discharge planning: Stable IC patient ready for discharge. → Answer: discontinue offending medications, arrange PCP follow-up in 1–2 weeks, repeat colonoscopy at 2–3 months if segmental disease.

One-Line Recap

Ischemic colitis is a transient, low-flow mucosal injury of the colon — most often at the splenic flexure in an older adult with vascular risk factors — diagnosed by CT plus colonoscopy within 48 hours, managed with bowel rest, IV fluids, empiric antibiotics, and discontinuation of vasoconstrictive medications, with surgery reserved for peritonitis, gangrene, perforation, or failure of medical therapy.

Board pearl: When in doubt on Step 3, "pain out of proportion + afib = AMI" and "crampy pain + bloody diarrhea + elderly = IC" — and the right answer almost never involves steroids or empiric anticoagulation for IC.

Diagnosis: Sudden crampy LLQ pain → bloody diarrhea within 24 h in an older adult = IC until proven otherwise; CT shows segmental wall thickening/thumbprinting; colonoscopy within 48 h confirms with single-stripe sign and biopsy showing ghost cells and hemosiderin-laden macrophages.

Management: NPO, IV crystalloid, empiric ceftriaxone + metronidazole (or pip-tazo) for moderate-severe disease, hold digoxin/NSAIDs/vasoconstrictors/OCPs, serial abdominal exams, surgery for peritonitis, pneumatosis with deterioration, portomesenteric gas, gangrene, or failure to improve at 48–72 h. No steroids. No routine anticoagulation.

Special populations: Young patients warrant hypercoagulable workup, urine toxicology, and OCP/smoking review; elderly require explicit medication reconciliation and palliative discussions when surgery carries high mortality; post-AAA repair patients require low threshold for bedside sigmoidoscopy.

Disposition and prevention: 85% resolve with supportive care; permanent discontinuation of offending drugs; CV risk-factor optimization (statin, BP, glucose, smoking); repeat colonoscopy at 2–3 months if symptoms persist or to exclude underlying malignancy; counsel on recurrence (5–10%) and red-flag return symptoms; arrange PCP follow-up within 1–2 weeks with structured handoff to prevent transition-of-care errors.