01Approach to the Critical Patient/attcp61

Immediate priorities

›Hemodynamic status

›Hypotension SBP <90 mmHg

›Aggressive IV fluid resuscitation with crystalloid

›Vasopressors if refractory to fluids

›Tachycardia HR >100 bpm

›Volume assessment

›Atrial fibrillation as precipitant

›If peritoneal signs present, emergent surgical consultation

›Guarding, rigidity, rebound

›Do not delay for diagnostic studies

›Can't-miss diagnoses

›Acute mesenteric ischemia

›Pain out of proportion to exam

›Requires CTA abdomen and pelvis immediately

›Transmural infarction

›Pneumatosis intestinalis on CT

›Portal venous gas on CT

›Right-sided colonic ischemia

›48.4% adverse outcome rate versus 12.1% for non-right-sided disease

›Greater than 50% require surgery

Monitoring and escalation

›Monitoring bundle

›Continuous cardiac monitoring

›Atrial fibrillation identification as precipitant

›Rate control if hemodynamically tolerated

›Serial abdominal exams

›Peritoneal signs emergence

02History/hx96

Presentation pattern

›Classic triad

›Sudden cramping left lower abdominal pain

›Pain typically mild-to-moderate

›Precedes bleeding by hours

›Urgent desire to defecate

›Onset within hours of pain

›Distinguishes from IBD

›Passage of bright red or maroon blood or bloody diarrhea within 24 hours

›Second most common cause of colonic hematochezia

›Accounts for up to 19% of lower GI bleeding

›Symptom prevalence

›Abdominal pain 87% of cases

›Typically left-sided

›Cramping character

›Rectal bleeding 84% of cases

›Bright red or maroon

›Not present in isolated right colon ischemia in 54-75% of cases

›Diarrhea 56% of cases

›Bloody diarrhea most specific

›Watery diarrhea less specific

›Nausea 30% of cases

›Vomiting less common

›Syncope in 6%

Atypical presentations

›Isolated right colon ischemia

›Pain without rectal bleeding in 54-75%

›Higher severity and adverse outcome rate

›Associated with dialysis, sepsis, shock

›Maintain suspicion with severe acute abdominal pain

›Atrial fibrillation plus severe pain plus right-sided colitis suggests acute mesenteric ischemia

›Requires CTA even without bleeding

›Post-surgical ischemic colitis

›Aortic surgery most common trigger

›Inferior mesenteric artery ligation

›Occurs 0.5-10% after aortic repair

›Young patients with drug or hypercoagulable etiology

›Cocaine and methamphetamine use

›Oral contraceptive use

Risk factors

›Patient-level risk factors

›Age 65 years or older

›Relative risk 3.7 times at age 70-79 versus 50-59

›Female sex predominance F:M approximately 3.5:1

›Cardiovascular disease

›Hypertension, atrial fibrillation, CHF, coronary artery disease

›Peripheral arterial disease OR 4.1

›Metabolic comorbidities

›Diabetes mellitus OR 1.76

›Dyslipidemia OR 2.12

›Chronic organ disease

›COPD

›Chronic kidney disease or dialysis

›Hypercoagulable states

›Factor V Leiden, antiphospholipid syndrome

›More relevant in younger patients or recurrent IC

›Precipitating factors

›Constipation

›Most common precipitant in elderly

›Polypharmacy with constipation-inducing drugs

›Dehydration or hypotension

›Recent illness with dehydration

›Hypotensive episodes

›Recent procedures

›Aortic surgery, cardiac catheterization

›Recent colonoscopy prep agents

Medication history

›Contributing medications to elicit

›Constipation-inducing agents

›Opioids, anticholinergics, calcium channel blockers

›Diuretics, digoxin

›Vasoconstrictors

›Triptans: naratriptan, sumatriptan

›Ergotamines, vasopressors

›IBS drugs with highest reported ORs

›Alosetron

›Tegaserod

›Other agents

›NSAIDs, immunomodulators, antipsychotics

›Oral contraceptives and hormonal therapy

›Colonoscopy prep agents

›PEG 3350

›Sodium phosphate agents

Past history and social history

›Relevant past medical history

›Prior episodes of ischemic colitis

›5-year recurrence rate 7-13%

›Identify and modify recurrence risk factors

›Prior aortic or cardiac surgery

›Inferior mesenteric artery territory at risk

›Prior abdominal surgeries

›Dialysis dependence

›Higher severity and adverse outcomes

›Right-sided involvement more common

›Social history

›Cocaine and methamphetamine use

›Vasoconstriction mechanism

›Younger patient presentation

›Smoking history

›Peripheral vascular disease risk

›Atherosclerosis contribution

03Physical Exam/exam60

Vital signs

›Hemodynamic assessment

›Blood pressure

›SBP <90 mmHg is a severity predictor

›Orthostatic changes for volume depletion

›Heart rate

›HR >100 bpm is a severity predictor

›Irregular rhythm suggesting atrial fibrillation

›Temperature

›Fever >38 C suggests moderate to severe disease

›Hypothermia as sepsis marker

›Respiratory rate

›Tachypnea with abdominal sepsis

›Oxygen saturation for systemic compromise

Abdominal exam

›Abdominal tenderness

›Left lower quadrant tenderness most common

›Splenic flexure and sigmoid distribution

›Corresponds to watershed areas

›Right lower quadrant or diffuse tenderness

›Isolated right colon ischemia pattern

›Increased surgical risk

›Abdominal distension

›Ileus or obstruction

›Colonic dilation

›Peritoneal signs

›Voluntary guarding

›Early peritoneal irritation

04Differential Diagnosis/ddx67

Life-threatening diagnoses

›Acute mesenteric ischemia

›Cannot-miss diagnosis

›ICD-10 K55.0

›Pain out of proportion to exam

›Distinguishing features

›Involves small bowel

›Severe constant pain

›CTA required urgently

›Bowel perforation

›Free air on imaging

›ICD-10 K63.1

›Requires emergent surgery

›From transmural ischemic colitis

›Progression of untreated IC

›Peritoneal signs

›Large bowel obstruction

›Cecal or sigmoid volvulus

›ICD-10 K56.2

›CT differentiates

›Obstructing colorectal malignancy

›ICD-10 C18.9

›Colonoscopy and CT confirm

Common mimics

›Infectious colitis

›C. difficile colitis

›ICD-10 A04.7

›Recent antibiotic use, watery diarrhea

05Laboratory Tests/lt82

Core hematology and chemistry

›Complete blood count

›Leukocytosis WBC >15 times 10 to the 9 per L

›Severity marker for ischemic colitis

›Predictor of adverse outcome

›Anemia

›Hemoglobin <75 mmol/mol for transfusion threshold

›Active GI bleeding assessment

›Thrombocytosis or thrombocytopenia

›Thrombocytopenia as DIC marker in severe disease

›Sepsis complication

›Comprehensive metabolic panel

›BUN elevated

›BUN >7.1 mmol/L is a severity marker

›Dehydration contribution

›Sodium <136 mmol/L

›Severity marker

›Fluid and electrolyte derangement

›Creatinine elevation

›Renal hypoperfusion

›AKI complication of severe disease

Severity markers and metabolic assessment

›Lactate

›Elevated lactate suggests tissue hypoperfusion or necrosis

›Lactate >2 mmol/L indicates bowel ischemia concern

›Repeat every 2-4 hours if elevated

›Critical for ruling out bowel necrosis

›Rapidly rising lactate with peritoneal signs requires emergency surgery

06Diagnostic Tests/dt103

Scoring Systems

›ACG severity classification

›Mild disease criteria

›Hemodynamically stable

›Less than 3 of 6 severity markers

›Moderate disease criteria

›Hemodynamically stable but 3 or more severity markers

›Severity markers: isolated right colon ischemia, WBC >15 times 10 to the 9 per L, hemoglobin <120 mmol/mol, sodium <136 mmol/L, BUN >7.1 mmol/L, LDH >350 U/L

›Severe disease criteria

›Any peritoneal signs or hemodynamic instability

›Pneumatosis or portal venous gas on CT

›Predictors of adverse outcome

›Right-sided colonic involvement

›48.4% adverse outcome rate versus 12.1% for left-sided

›Greater than 50% require surgery

›Pancolonic involvement

›Mortality rate approximately 21%

›ICU admission required

›Peritoneal signs at presentation

›Emergent surgery required

›High mortality without prompt intervention

Scoring Systems additional tools

›Clinical prediction of severity

›Sun et al. systematic review of 2823 patients from 22 studies

›Peritoneal signs, hypoalbuminemia, and chronic kidney disease as predictors of surgery

›Isolated right colon ischemia as strongest predictor of poor outcome

›Hemodynamic parameters

›SBP <90 mmHg independently predicts adverse outcome

›HR >100 bpm as severity predictor

MRI

›Magnetic resonance imaging role

›Limited role in acute ischemic colitis

›CT is preferred in acute setting due to speed and availability

›MRI best for subacute or chronic evaluation

›MRI findings in ischemic colitis

›Mural thickening of affected segment

›Pericolonic fat stranding

›Diffusion restriction in transmural infarction

›MR angiography

›Evaluation of mesenteric vasculature when CTA contraindicated

›Renal insufficiency with gadolinium risk assessment

›Less sensitive than CTA for acute thrombus

›Mesenteric vein thrombosis evaluation

›Alternative to CTA in younger patients

›Radiation avoidance consideration

CT

›CT abdomen and pelvis with IV contrast

›First-line imaging for ischemic colitis evaluation

›CTA protocol if acute mesenteric ischemia cannot be excluded

›Sensitivity approximately 82% for ischemic colitis

›Classic CT findings in ischemic colitis

›Segmental colonic wall thickening

›Pericolonic fat stranding

›Thumbprinting appearance from submucosal edema

›CT findings indicating severity

›Pneumatosis intestinalis

›Gas within bowel wall indicates transmural infarction

›Emergency surgical consultation trigger

›Portal venous gas

›Indicates severe transmural ischemia or infarction

›Emergency surgical consultation trigger

›Pneumoperitoneum

›Bowel perforation

›Emergent operative intervention

›CT angiography for mesenteric vessels

›Indicated if acute mesenteric ischemia suspected

›Pain out of proportion to exam

›Right-sided colitis without obvious precipitant

›Identifies superior and inferior mesenteric artery occlusion

›Thrombus versus embolus characterization

›Guides vascular surgery or interventional radiology consultation

›Identifies mesenteric venous thrombosis

›Portal and mesenteric vein evaluation

›Anticoagulation consideration if thrombosis confirmed

Ultrasound

›Abdominal ultrasound

›Limited primary diagnostic role for ischemic colitis

›Used as initial screen if CT unavailable

›Operator dependent and bowel gas limited

›Ultrasound findings suggestive of ischemic colitis

›Segmental colonic wall thickening greater than 3 mm

›Pericolonic fluid

›Decreased or absent Doppler flow in severe disease

›Point-of-care ultrasound

›Adjunct to clinical assessment

›Free fluid assessment in peritoneum

›Not diagnostic for ischemic colitis alone

›Cardiac POCUS

›LV function assessment

›Right heart strain evaluation

›Atrial fibrillation evaluation

›Colonoscopy as primary diagnostic tool

›Gold standard for diagnosis

›Sensitivity greater than 90% for mucosal ischemia

›Performed within 48 hours of presentation when hemodynamically stable

›Colonoscopy findings

›Pale or cyanotic mucosa

›Mucosal hemorrhage and ulceration

›Sharp segmental demarcation from normal to ischemic mucosa

›Rectal sparing characteristic of ischemic colitis

›Gangrene findings on colonoscopy

›Blue-black nodules and dusky mucosa

›Emergency surgical consultation trigger

›Do not attempt biopsies if gangrenous

›Contraindications to colonoscopy

›Peritoneal signs or hemodynamic instability

›Pneumatosis or portal venous gas on CT

›Perforation on imaging

07Disposition/dispo57

Admission criteria

›Indications for admission

›Hemodynamic instability

›SBP <90 mmHg or HR >100 bpm

›Requiring IV resuscitation

›Moderate or severe disease by ACG criteria

›Three or more severity markers

›Peritoneal signs

›Inability to tolerate oral intake

›Vomiting or severe nausea

›Significant pain limiting oral intake

›Right-sided or pancolonic involvement

›Higher adverse outcome rate

›Colonoscopy within 48 hours required

›Significant comorbidities

›Elderly, CHF, CKD, COPD

›Dialysis dependence

ICU admission criteria

›ICU level care indications

›Peritoneal signs with hemodynamic instability

›Pre-operative stabilization

›Vasopressor requirement

›Lactic acidosis with hemodynamic compromise

›Lactate >4 mmol/L with instability

›Rising lactate despite resuscitation

›Suspected bowel necrosis or infarction

›Pneumatosis intestinalis on CT

›Portal venous gas on CT

08Treatment/t86

Mild disease management

›Bowel rest and fluid resuscitation

›NPO status with IV fluid resuscitation

›Normal saline or lactated Ringer

›Rate 125-250 mL/hr adjusted to hemodynamic response

›Nasogastric decompression if ileus

›Intermittent suction

›Advance diet after clinical improvement

›Medication management

›Discontinue offending medications

›NSAIDs, vasoconstrictors, constipation-inducing drugs

›Diuretics and digoxin reassessment

›No antibiotics for mild disease

›ACG Clinical Guideline recommendation

›Advance to diet as symptoms resolve

›Treat precipitating conditions

›CHF with diuresis cautiously

›Rate control for atrial fibrillation

›Dehydration correction

Moderate disease management

›Antibiotics for moderate disease

›Ciprofloxacin plus metronidazole regimen

›Ciprofloxacin 400 mg IV every 12 hours

›Adjust for renal function

›Oral switch when tolerating

›Metronidazole 500 mg IV every 8 hours

›Anaerobic coverage for bacterial translocation

›500 mg orally three times daily for oral switch

›Alternative broad-spectrum antibiotic

›Piperacillin-tazobactam 3.375 g IV every 6 hours

›Single agent coverage for enteric gram-negatives and anaerobes

›Adjust for renal function

›Duration typically 5-7 days depending on clinical response

›Surgical consultation for moderate disease

›Early surgical consultation required

›ACG Clinical Guideline recommendation

›Right-sided or pancolonic involvement prompts urgent consultation

›Serial monitoring while awaiting surgical assessment

›Abdominal exams every 4-6 hours

›Serial CBC, lactate, BMP

Severe disease management

›Emergent surgical consultation

›Peritoneal signs or hemodynamic instability

›Immediate operative planning

›Do not delay surgery for further workup

›Surgical options

›Segmental colectomy for limited disease

›Anastomosis versus diverting stoma based on contamination

›Diverting stoma preferred in contaminated field

›Subtotal or total colectomy for pancolonic infarction

›End ileostomy with Hartmann procedure

›High mortality with pancolonic infarction

›ICU resuscitation

›Vasopressor support for refractory hypotension

›Norepinephrine first-line 0.01-0.5 mcg/kg/min

›Titrate to MAP >65 mmHg

›Arterial line monitoring

›Vasopressin 0.03 units/min as adjunct if norepinephrine dose escalating

›Add to norepinephrine not replace

›Fixed dose

›Broad-spectrum antibiotics immediately

›Piperacillin-tazobactam 3.375 g IV every 6 hours

›Covers enteric gram-negatives and anaerobes

›Adjust for renal function

›Add vancomycin if MRSA risk or hospital-acquired sepsis

›Vancomycin 15-20 mg/kg IV every 8-12 hours

›Target AUC/MIC 400-600

Anticoagulation

›Anticoagulation decision

›Not indicated in greater than 95% of cases

›Non-occlusive etiology predominates

›ACG Clinical Guideline recommendation

›Indicated only if mesenteric venous thrombosis identified on CT

›Therapeutic anticoagulation with heparin

›Heparin IV infusion titrated to aPTT 60-100 seconds

›Transition to LMWH or direct oral anticoagulant

›Anticoagulation if mesenteric arterial embolism identified

›Vascular surgery or interventional radiology consultation

›Heparin bridging while planning intervention

Contraindicated treatments

›Treatments to avoid

›Glucocorticoids

›Not recommended for ischemic colitis

›ACG Clinical Guideline recommendation

›Unless treating underlying vasculitis

›Opioid analgesics

›Worsen constipation and ischemia

›Mask peritoneal signs

›NSAIDs

›Worsen mesenteric ischemia

›Avoid in any severity

09Special Populations/sp78

Pregnancy

›Ischemic colitis in pregnancy

›Rare but reported

›Hypercoagulable state of pregnancy increases risk

›Third trimester most common timing

›Physiologic considerations

›Increased IVC compression reduces venous return

›Inferior mesenteric vein compression in late pregnancy

›Normal lactate may be slightly lower in pregnancy

›Diagnostic considerations in pregnancy

›CT with IV contrast

›Risk-benefit favors CT in severe presentations

›Fetal radiation dose with abdominal CT approximately 8-49 mGy

›MRI without gadolinium preferred if time allows for subacute presentation

›Ultrasound as first-line if stable

›No radiation

›Limited sensitivity for ischemic colitis

›Treatment in pregnancy

›IV fluid resuscitation

›Crystalloid resuscitation safe

›Left lateral decubitus position to relieve IVC compression

›Antibiotics if moderate to severe

›Cefazolin 1-2 g IV every 8 hours safe in all trimesters

›Metronidazole: Category B, generally safe after first trimester

›Avoid ciprofloxacin in pregnancy

›Obstetric and surgical co-management

›Fetal heart rate monitoring in viable pregnancy

›Timing of delivery if severe maternal illness

10Background/b97

Epidemiology

›Incidence and prevalence

›Most common form of intestinal ischemia

›Second most common cause of colonic hematochezia

›Accounts for up to 19% of lower GI bleeding episodes

›Annual incidence approximately 6.1-7.2 per 100,000 person-years

›True incidence likely underestimated due to spontaneous resolution

›Increasing recognition with CT and colonoscopy availability

›Demographics

›Median age 70 years

›Predominantly elderly population

›Age-related risk factors predominate

›Female predominance

›Female to male ratio approximately 3.5:1

›Hormonal and vascular differences hypothesized

›Etiology distribution

›Greater than 95% non-occlusive etiology

›Transient reduction in mesenteric blood flow

›Low-flow state without identifiable occlusion

›Less than 5% occlusive etiology

›Mesenteric artery thromboembolism

›Mesenteric venous thrombosis

›Recurrence and outcomes

›5-year recurrence rate 7-13%

›Identify and modify individual risk factors

›Underlying cardiovascular disease major driver

›Majority of cases resolve within 1-2 weeks

›Transient self-limited course in most

›Approximately 20% develop chronic ischemic colitis

Pathophysiology

›Watershed area vulnerability

›Splenic flexure at Griffith point

›Junction of SMA and IMA territories

›Most susceptible to low-flow ischemia

›Rectosigmoid junction at Sudeck point

›Junction of IMA and hypogastric artery territories

›Second most common site

›Rectum usually spared

›Dual blood supply from IMA and hypogastric arteries

›Rectal sparing distinguishes IC from IBD

›Mechanisms of ischemia

›Non-occlusive low-flow states

›Cardiogenic shock or congestive heart failure

›Hypovolemia and dehydration

›Vasospasm from vasoconstrictors or drugs

›Occlusive mechanisms

›Arterial embolism most common occlusive cause

›Atrial fibrillation as source of cardioembolism

›Mesenteric venous thrombosis from hypercoagulable state

›Mechanical causes

›Colonic distension from obstruction increasing intraluminal pressure

›Reducing mucosal blood flow below critical threshold

›Colonoscopy prep with hyperosmolar agents

›Injury cascade

›Initial mucosal ischemia

›Superficial hemorrhage and ulceration

›Reversible with restoration of flow

›Progression to submucosal injury

›Edema causing thumbprinting on imaging

›Increased mucosal permeability and bacterial translocation

›Transmural infarction

›Full-thickness necrosis

›Pneumatosis intestinalis

›Perforation risk

Therapeutic Considerations

›Evidence base for management

›ACG Clinical Guideline 2015 primary evidence source

›Brandt LJ et al. American Journal of Gastroenterology 2015

›Defines severity classification and management algorithm

›Majority of evidence from observational studies

›No randomized controlled trials for specific IC treatments

›Extrapolation from ischemia and sepsis literature

›Antibiotic rationale

›Bacterial translocation from ischemic mucosa

›Enteric gram-negative organisms predominate

›Anaerobic organisms also present

›Antibiotics recommended for moderate to severe disease

›No benefit demonstrated for mild disease

›ACG Clinical Guideline recommendation

›Duration typically 5-7 days

›Guided by clinical response

›De-escalate based on culture results

›Surgical decision framework

›Emergency surgery indicated for

›Peritoneal signs or hemodynamic instability

›Pneumatosis intestinalis or portal venous gas

›Gangrene on colonoscopy

›Clinical deterioration despite medical management

›Elective surgery for

›Persistent symptoms beyond 2-3 weeks

›Protein-losing colopathy

›Recurrent sepsis

›Symptomatic stricture as sequela

›Special therapeutic considerations

›Isolated right colon ischemia

›Higher surgical rate requires early consultation

›More aggressive monitoring protocol

›Post-aortic surgery ischemic colitis

›Mandatory colonoscopy within 48 hours after aortic repair

›High mortality without early detection

11Patient Discharge Instructions/pdi30

copy discharge instructions

›Discharge instructions for ischemic colitis

›What is ischemic colitis

›Temporary reduced blood flow to part of your colon caused inflammation and bleeding

›Most cases heal on their own within 1-2 weeks

›Diet instructions

›Start with clear liquids then advance to low-residue diet

›Drink at least 8 glasses of water per day to stay hydrated

›Avoid alcohol and excessive caffeine which can cause dehydration

›High-fiber diet long-term to prevent constipation once recovered

›Medications to take

›Take all prescribed antibiotics for the full course

›Use stool softeners as directed to prevent constipation

›Take any prescribed medications for heart rhythm or blood pressure

›Medications to avoid

›Do not take NSAIDs such as ibuprofen, naproxen, aspirin unless prescribed by your doctor

›Do not take opioid pain medications unless absolutely necessary as they worsen constipation

›Inform your doctor before restarting any blood pressure or heart medications

›Activity

›Rest as needed

›Resume normal activity gradually as symptoms improve

›Follow-up appointments

›See your gastroenterologist within 1-2 weeks

›A colonoscopy will likely be scheduled to check healing and rule out other causes

›Return to the emergency department immediately if you experience

›Worsening or severe abdominal pain

›Increased or recurrent bloody stools

›Fever above 38 degrees Celsius or 100.4 degrees Fahrenheit

12References/r52

Guidelines and key sources

›ACG Clinical Guideline on Colon Ischemia

›Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ

›Epidemiology, Risk Factors, Patterns of Presentation, Diagnosis, and Management of Colon Ischemia

›American Journal of Gastroenterology 2015

›doi 10.1038/ajg.2014.395

›Primary guideline defining severity classification and management algorithm

›Defines mild, moderate, and severe disease categories

›Recommends against glucocorticoids and routine anticoagulation

›Gastrointestinal Surgical Emergencies Textbook

›Aaron AE et al. American College of Surgeons 2021

›Comprehensive surgical management framework

›Available at facs.org

›Indications for surgical intervention and operative approaches

›Peritoneal signs, pneumatosis, portal venous gas, gangrene

›Segmental versus subtotal colectomy decision framework

›Systematic review of severity predictors

›Sun D, Wang C, Yang L, Liu M, Chen F

›Predictors of the Severity of Ischaemic Colitis: Systematic Review of 2823 Patients From 22 Studies

›Colorectal Disease 2016

›PMID 27206727

›Isolated right colon ischemia as strongest predictor of adverse outcome

›Peritoneal signs, hypoalbuminemia, and CKD also predictive

›Informs ACG severity classification

Supporting evidence

›Clinical characteristics analysis

›Hong SS. Analysis of Clinical Characteristics of 117 Cases of Ischemic Colitis

›BMC Gastroenterology 2025

Evidence & Review