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Approach to the Critical Patient
Immediate threats
Immediate threats
Hemodynamic instability
If hypotension, resuscitation bay
If shock, broad differential including sepsis, hemorrhage, perforation
Toxic megacolon concern
If severe abdominal distension with systemic toxicity, immediate abdominal radiograph
If colonic diameter 6 cm or greater with toxicity, urgent GI and surgery
Peritonitis concern
If rigidity or rebound, CT abdomen pelvis with IV contrast and surgical consult
Massive gastrointestinal bleeding
If ongoing large volume hematochezia with instability, massive transfusion pathway
Severe dehydration and electrolyte derangement
If altered mental status or arrhythmia risk, telemetry and rapid correction
Initial stabilization bundle
Stabilization bundle
Monitoring and access
Continuous pulse oximetry
Cardiac monitor for significant electrolyte abnormality
Two large bore IV lines
Fluid resuscitation
Isotonic crystalloid bolus for hypovolemia
Reassess after each bolus using blood pressure and urine output
Early antibiotics only when indicated
If sepsis, perforation, abscess, or cholangitis, initiate broad spectrum coverage
If uncomplicated acute severe ulcerative colitis without infection, avoid adjunctive antibiotics
Early specialty activation
GI consult for hospitalized flare or acute severe ulcerative colitis
Surgery consult for toxic megacolon, perforation, refractory hemorrhage, obstruction not improving
Medication safety
Avoid NSAIDs
Avoid antimotility agents if severe colitis or megacolon concern
If high dose steroids planned, infection workup before initiation when feasible
Severity triage targets
Severity triage
Acute severe ulcerative colitis screen
Stool frequency 6 or more per day with blood
Systemic toxicity features
Temperature 37.8 C or higher
Heart rate 90 or higher
Hemoglobin low for age and sex
CRP elevated
Complicated Crohn disease screen
Obstructive symptoms
Suspected intraabdominal abscess
Perianal sepsis
High fever or sepsis physiology
History
Flare characterization
Flare characterization
Diagnosis context
Ulcerative colitis location history
Crohn disease phenotype
Inflammatory
Stricturing
Penetrating
Perianal
Symptom pattern
Stool frequency trend
Blood and mucus
Nocturnal stools
Urgency and tenesmus
Abdominal pain location
Nausea and vomiting
Severity markers
Fever or chills
Syncope or presyncope
Oliguria
Weight loss
Poor oral intake
Triggers and alternate etiologies
Triggers and alternate etiologies
Infectious triggers
Recent antibiotics
Recent hospitalization
Sick contacts
Travel and food exposures
Medication factors
Nonadherence to maintenance therapy
Recent steroid taper
Recent biologic infusion timing
NSAID exposure
Immune suppression risks
Current biologic or JAK inhibitor use
Thiopurine or methotrexate use
Recent high dose steroids
Complication clues
Progressive distension
Obstipation
Severe focal pain
Perianal pain or drainage
Dysuria or pneumaturia
Extraintestinal manifestations and red flags
Systemic features
Extraintestinal manifestations
Uveitis symptoms
Oral ulcers
Erythema nodosum
Pyoderma gangrenosum
Peripheral arthritis
Axial back pain
Thromboembolism symptoms
Pleuritic chest pain
Unilateral leg swelling
Pregnancy and fertility context
Pregnancy possibility
Postpartum status
Physical Exam
General and hemodynamics
General and hemodynamics
Appearance
Toxic appearance
Dehydration signs
Vitals
Fever pattern
Tachycardia
Hypotension or orthostasis
Perfusion
Capillary refill
Mental status
Abdominal and perineal exam
Abdominal and perineal
Abdominal exam
Distension
Bowel sounds
Diffuse tenderness
Focal tenderness
Guarding or rebound
Rectal and perianal exam when appropriate
Gross blood
Fissure
Abscess fluctuance
Fistula opening or drainage
Stoma exam when present
Output volume
Peristomal skin integrity
Extraintestinal exam
Extraintestinal
Skin
Erythema nodosum lesions
Ulcerative lesions consistent with pyoderma
Eyes
Conjunctival injection and photophobia
Joints
Peripheral synovitis
Sacroiliac tenderness
Differential Diagnosis
Bloody diarrhea and colitis phenotype
Bloody diarrhea and colitis
Ulcerative colitis flare
ICD-10 K51 dot 9
SNOMED CT ulcerative colitis
Crohn colitis flare
ICD-10 K50 dot 1
SNOMED CT Crohn disease
Infectious colitis
Clostridioides difficile infection
Campylobacter
Salmonella
Shigella
Shiga toxin producing E coli
CMV colitis in immunosuppressed
Ischemic colitis
Older age or vascular risk
Medication related colitis
NSAID associated colitis
Immune checkpoint inhibitor colitis
Abdominal pain and complication phenotype
Abdominal pain and complications
Toxic megacolon
Colonic dilation with systemic toxicity
Perforation
Peritonitis signs
Intraabdominal abscess
Fever with focal tenderness
Small bowel obstruction
Vomiting and obstipation
Appendicitis
Right lower quadrant focality
Ovarian and gynecologic causes
Ectopic pregnancy
Ovarian torsion
Laboratory Tests
Core labs for severity and safety
Core labs
Hematology
Complete blood count for anemia and leukocytosis
Neutrophilia compatible with inflammation or steroids
Severe anemia as marker of hemorrhage or chronic disease
Chemistry
Electrolytes for dehydration and diarrhea losses
Potassium depletion risk
Magnesium depletion risk
Creatinine for volume status and medication dosing
Albumin for severity and drug pharmacokinetics
Inflammation
CRP for severity trend
ESR optional for trend context
Hepatobiliary
ALT AST ALP GGT bilirubin for PSC or drug injury
Coagulation
INR for liver dysfunction and procedural planning
Lactate when shock, sepsis, or ischemia concern
Venous blood gas with lactate in unstable patients
Stool and infection evaluation
Stool evaluation
C difficile testing
NAAT or two step algorithm per local lab
High priority before escalating immunosuppression
Bacterial stool testing
Culture or multiplex PCR panel based on availability
Shiga toxin testing when clinically indicated
Ova and parasites when risk factors present
Travel exposure
Prolonged symptoms
Fecal calprotectin when outpatient differentiation needed
Higher values support inflammatory activity
Immunosuppression safety labs
Immunosuppression safety
Pregnancy test before teratogenic or radiologic exposure
Blood cultures if febrile or septic
Viral hepatitis screening when starting biologics if not previously done
Hepatitis B surface antigen and core antibody
TB screening when starting biologics if not previously done
IGRA preferred in BCG vaccinated
If severe flare with planned rescue therapy, baseline lipid and magnesium for calcineurin inhibitor safety
Diagnostic Tests
Scoring Systems
Scoring systems
Truelove and Witts acute severe ulcerative colitis criteria
Stool frequency 6 or more per day with blood
At least one systemic toxicity feature
Temperature 37.8 C or higher
Heart rate 90 or higher
Hemoglobin low for age and sex
CRP elevated
Mayo score for ulcerative colitis activity
Stool frequency subscore
Rectal bleeding subscore
Endoscopic appearance subscore
Physician global assessment subscore
Harvey Bradshaw Index for Crohn disease activity
General well being
Abdominal pain
Liquid stools per day
Abdominal mass
Complications count
Pediatric Ulcerative Colitis Activity Index
Stool frequency
Rectal bleeding
Abdominal pain
Activity level
Nocturnal stools
Examination findings
MRI
MRI
MR enterography for Crohn small bowel assessment
Active inflammation features
Wall thickening and hyperenhancement
Edema
Complication features
Fistula tracts
Abscess
Stricture characterization
Pelvic MRI for perianal Crohn disease
Fistula classification
Abscess mapping for drainage planning
Safety and logistics
Gadolinium avoidance in severe renal impairment when possible
Longer acquisition time compared with CT
CT
CT
CT abdomen pelvis with IV contrast for complication evaluation
Abscess detection
Pericolonic or intraabdominal collections
Obstruction evaluation
Transition point
Closed loop concern
Perforation evaluation
Free air
Free fluid
CT enterography in selected Crohn evaluations
Small bowel inflammation and strictures
Acute severe colitis imaging adjunct
If toxic megacolon concern, abdominal radiograph preferred for serial diameter tracking
Ultrasound
Ultrasound
Point of care ultrasound adjuncts
IVC assessment for volume status adjunct
Free fluid assessment when perforation concern
Perianal and superficial abscess evaluation
Bedside soft tissue ultrasound for fluctuance confirmation
Hepatobiliary ultrasound when cholestasis pattern
Gallstones
Bile duct dilation
Disposition
Admission and level of care
Admission and level of care
Admit indications
Acute severe ulcerative colitis criteria met
Inability to maintain hydration or oral intake
Severe pain requiring parenteral analgesia
Significant anemia requiring transfusion
Electrolyte derangement requiring IV replacement
Suspected abscess, obstruction, perforation, or toxic megacolon
Systemic infection concern in immunosuppressed
ICU indications
Shock physiology
Ongoing major hemorrhage
Toxic megacolon with systemic instability
Postoperative or high risk airway needs
Discharge criteria for mild flare
Discharge criteria
Clinical stability
Normal blood pressure without IV fluids
No high fever
Tolerating oral hydration
Low complication concern
No peritonitis
No severe distension
No persistent vomiting
Outpatient plan secured
Rapid GI follow up arranged
Stool studies plan if not completed
Clear return precautions provided
Treatment
Supportive care
Supportive care
Fluids and electrolytes
Isotonic crystalloid
Titrate boluses to perfusion and urine output
Reassess after each bolus
Potassium replacement
If potassium low, replete per local protocol
Telemetry if severe hypokalemia
Magnesium replacement
If magnesium low, replete per local protocol
Co replete with potassium when both low
Analgesia and antiemetics
Acetaminophen
Maximum daily dose per hepatic status
Avoid combination duplicates
Opioids with caution in severe colitis
If needed, lowest effective dose
Monitor for ileus and megacolon
Antiemetic options
Ondansetron
QT risk review in electrolyte derangement
Nutrition
Enteral nutrition preferred when tolerated
Avoid routine bowel rest
Total parenteral nutrition not used solely for bowel rest in acute severe ulcerative colitis
Venous thromboembolism prophylaxis
Pharmacologic prophylaxis for hospitalized flares unless contraindicated
Low molecular weight heparin dosing per weight and renal function
Continue despite non massive hematochezia when safe
Ulcerative colitis flare pharmacotherapy
Ulcerative colitis pharmacotherapy
Mild to moderate outpatient flare
Oral mesalamine
Total daily dose 2 g to 4.8 g
Once daily or divided based on formulation
Rectal mesalamine for distal disease
Suppository 1 g nightly or enema per formulation
Add to oral therapy for proctitis or left sided disease
Oral corticosteroid for inadequate response
Prednisone 40 mg daily
Taper after response with steroid sparing plan
Acute severe ulcerative colitis inpatient induction
IV corticosteroids
Methylprednisolone IV 40 mg to 60 mg daily
Reassess response at day 3
Hydrocortisone IV 100 mg every 6 hours alternative
Avoid doses higher than guideline range without clear rationale
DVT prophylaxis concurrent
Initiate unless contraindicated
High VTE risk in active colitis
Avoid adjunctive antibiotics without infection
Do not add empiric antibiotics solely for acute severe ulcerative colitis
Steroid refractory acute severe ulcerative colitis rescue
Rescue decision at day 3 to day 5 of IV steroids
If inadequate response by day 3, initiate rescue pathway
Early surgical discussion in parallel
Infliximab
5 mg per kg IV induction dose
Repeat at week 2 and week 6 standard schedule
Consider accelerated dosing protocol per local expert pathway
Cyclosporine
Continuous IV infusion 2 mg per kg per day
Target trough level 150 ng per mL to 250 ng per mL per local protocol
Transition to oral cyclosporine with bridging plan when stabilized
Sequential rescue caution
Avoid routine infliximab after cyclosporine or cyclosporine after infliximab due to adverse event risk
If considering third line rescue, multidisciplinary decision with surgery
Crohn disease flare pharmacotherapy
Crohn pharmacotherapy
Mild ileocecal disease
Budesonide controlled ileal release 9 mg daily
Typical course up to 8 weeks then taper
Not for severe disease or extensive colitis
Moderate to severe luminal flare
Systemic corticosteroid induction
Prednisone 40 mg to 60 mg daily
Taper with steroid sparing maintenance plan
If inpatient severe flare, methylprednisolone IV 40 mg to 60 mg daily
Reassess within 72 hours
Biologic or small molecule escalation with GI
Anti TNF therapy options
Infliximab or adalimumab
Consider combination with thiopurine in selected patients per risk profile
Vedolizumab option
Gut selective mechanism for induction and maintenance
Ustekinumab option
IL 12 23 pathway
Perianal or fistulizing disease adjuncts
Antibiotics as adjunct when infection or perianal sepsis concern
Metronidazole option
Neuropathy risk with prolonged use
Ciprofloxacin option
Tendinopathy and QT risk review
Drainage for abscess
If abscess present, source control before escalation of immunosuppression
Complication specific management
Complication management
Toxic megacolon pathway
Bowel rest
NPO with close monitoring
Avoid opioids when possible
Broad spectrum antibiotics
If megacolon suspected, cover gram negative and anaerobes
Add coverage per local sepsis protocol
High dose IV steroids for inflammatory etiology
If suspected IBD driven megacolon, IV corticosteroids per acute severe ulcerative colitis protocol
Immediate surgical involvement
Obstruction in Crohn disease
Cross sectional imaging confirmation
Differentiate inflammatory edema versus fixed fibrotic stricture
Surgical and GI co management
Nasogastric decompression when persistent vomiting
Titrate based on output and symptoms
Intraabdominal abscess
Antibiotics plus drainage strategy
Percutaneous drainage when accessible
Culture directed narrowing when results available
Severe anemia
Transfusion thresholds individualized
If symptomatic anemia or hemodynamic compromise, transfuse
Iron repletion planning after stabilization
Special Populations
Pregnancy
Pregnancy
Maternal fetal priorities
Disease control prioritized to reduce adverse outcomes
Active disease higher risk than most maintenance medications
Medication safety highlights
Avoid methotrexate
Teratogenic and contraindicated
Corticosteroids acceptable for induction when needed
Monitor gestational diabetes and hypertension risk
Anti TNF therapy generally compatible through pregnancy
Timing of late gestation dosing individualized
Imaging preferences
Ultrasound and MRI preferred when feasible
CT only when urgent diagnostic need
Geriatric
Geriatric
Presentation and risk
Higher infection risk on immunosuppression
Lower fever response possible
Medication considerations
Steroid adverse effects amplified
Delirium risk
Hyperglycemia risk
Thromboembolism prophylaxis emphasis
Balance bleeding risk with high baseline VTE risk
Alternate diagnoses
Ischemic colitis higher likelihood
Vascular history and hypotension context
Pediatrics
Pediatrics
Severity scoring
PUCAI for ulcerative colitis activity
Hospitalization thresholds per pediatric GI pathway
Steroid dosing patterns
Prednisone 1 mg per kg per day typical induction
Maximum dose per pediatric protocol
IV methylprednisolone 1 mg per kg per day to 1.5 mg per kg per day inpatient
Maximum 60 mg per day common cap
Growth and nutrition focus
Malnutrition screening
Early dietitian involvement
Exclusive enteral nutrition option in Crohn disease induction
Pediatric centered strategy with specialist guidance
Background
Epidemiology
Epidemiology
Disease burden
Chronic relapsing inflammatory disorders of gastrointestinal tract
Ulcerative colitis limited to colon
Crohn disease can involve any GI segment
Peak onset pattern
Young adult predominance with secondary older age peak
Family history increases risk
Pathophysiology
Pathophysiology
Immune dysregulation
Mucosal immune activation with barrier dysfunction
Microbiome and environmental interactions
Ulcerative colitis features
Continuous mucosal inflammation starting at rectum
Superficial ulceration with bleeding
Crohn disease features
Transmural inflammation with skip lesions
Strictures from fibrosis
Fistulas from penetrating disease
Therapeutic Considerations
Therapeutic considerations
Steroids as induction only
Not effective for maintenance in Crohn disease
Steroid sparing transition required
Biologic therapy goals
Symptom control plus mucosal healing
Reduced hospitalization and surgery risk
Infection risk management
Screen and vaccinate when possible before immunosuppression
Monitor for opportunistic infections during flares
Antibiotics role
Not routine for uncomplicated ulcerative colitis flare
Targeted use for abscess or sepsis
Patient Discharge Instructions
copy discharge instructions
copy discharge instructions
Diagnosis and plan
Flare of inflammatory bowel disease possible
Medication plan as prescribed
Hydration and diet
Oral fluids with electrolytes
Small frequent meals as tolerated
Medication cautions
Avoid NSAIDs
Avoid loperamide if severe abdominal pain, distension, or fever
Follow up
GI follow up within 1 week or sooner if worsening
Stool test follow up if sent
Return to ER now for red flags
Fainting or severe weakness
Inability to keep fluids down
Fever 38.0 C or higher with worsening symptoms
Severe or increasing abdominal pain
New abdominal distension or no gas or stool
Large volume blood in stool or black tarry stool
Chest pain or shortness of breath
New one sided leg swelling
References
Clinical guidelines and key sources
Clinical guidelines and key sources
ACG Clinical Guideline Ulcerative Colitis in Adults 2019
Acute severe ulcerative colitis IV steroids methylprednisolone 60 mg per day or hydrocortisone 100 mg three to four times daily
AGA Clinical Guidance Management of Moderate to Severe Ulcerative Colitis
IV methylprednisolone dose equivalent 40 mg to 60 mg daily in hospitalized acute severe ulcerative colitis
British Society of Gastroenterology guideline on inflammatory bowel disease 2025
Rescue therapy timelines and colectomy triggers in acute severe ulcerative colitis
ACG Clinical Guideline Crohn Disease 2025 update
Corticosteroids induction only and early steroid sparing strategy
Canadian Association of Gastroenterology Clinical Practice Guideline Luminal Crohn Disease 2019
Anti TNF and newer biologic sequencing recommendations
ECCO Guidelines on Therapeutics in Ulcerative Colitis Surgical Treatment 2022
Surgical indications and perioperative considerations
Evidence labeling note
ACEP Level A B C not established for inflammatory bowel disease flare specific pathways
Class I IIa IIb terminology used only when explicitly stated in cited society guidance
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.