Severe constipation or fecal impaction (ICD-10 K59.00)
Rectal vault stool
No transition point on CT
Acute appendicitis (ICD-10 K35.80)
RLQ focal pain
Leukocytosis pattern
Acute diverticulitis (ICD-10 K57.32)
LLQ focal tenderness
Pericolic fat stranding
Laboratory Tests
Core tests
Baseline labs
Complete blood count
Leukocytosis for ischemia or perforation concern
Hemoglobin trend for malignancy or bleeding concern
Electrolytes and renal function
Sodium and potassium derangements from dehydration
Creatinine for contrast planning and AKI risk
Liver panel
Alternative diagnosis screen
Baseline for operative planning
Perfusion and sepsis markers
Ischemia and infection assessment
Lactate
Elevated lactate as ischemia or shock marker
Normal lactate does not exclude early ischemia
Venous blood gas
Metabolic acidosis pattern
pCO2 compensation pattern in mmHg
Blood cultures if sepsis concern
Two sets before antibiotics when feasible
Do not delay antibiotics in shock
Coagulation and transfusion planning
Bleeding and procedure readiness
INR and aPTT
Anticoagulant effect screen
Baseline for emergent surgery
Type and screen
Operative readiness
Hemodynamic instability pathway
PITFALLS
Lab interpretation traps
Mild leukocytosis common in dehydration
Normal WBC does not exclude strangulation
Rising lactate trend more concerning than isolated value
Diagnostic Tests
Scoring Systems
Risk stratification frameworks
Sepsis screening (qSOFA or SIRS)
Altered mentation
SBP ≤ 100 mmHg
RR ≥ 22/min
Shock severity (lactate-guided resuscitation)
Lactate ≥ 2 mmol/l as abnormal
Lactate ≥ 4 mmol/l as high risk
Peritonitis triggers for operative pathway
Rebound tenderness
Involuntary guarding
MRI
MRI role
Pregnancy or radiation avoidance scenarios
Non-contrast MRI abdomen as alternative when stable
Limited availability and longer acquisition time
Contraindications and limitations
Unstable patient
Metallic implant constraints
CT
CT abdomen and pelvis utility
CT with IV contrast as first-line in most suspected large bowel obstruction
Transition point localization
Etiology suggestion
CT ischemia and perforation signs
Pneumatosis intestinalis
Portal venous gas
Free intraperitoneal air
Mesenteric edema or ascites
Reduced bowel wall enhancement
Closed-loop and competent ileocecal valve considerations
Marked cecal dilation risk
Increased perforation risk with progressive diameter
Ultrasound
Bedside ultrasound adjunct
FAST or free fluid assessment
Free fluid in hypotension pathway
Peritoneal fluid as severity marker
Limited LBO performance
Poor colonic gas windows
Not a rule-out test
Disposition
Level of care
Admission decisions
Inpatient admission as default for suspected large bowel obstruction
ICU criteria
Vasopressor requirement
Rising lactate despite fluids
Respiratory failure
Transfer criteria
No on-site colorectal surgery capability
Need for emergent endoscopy and no local access
Operative vs nonoperative pathway
Operative indications
Peritonitis
Perforation evidence
Ischemia evidence
Complete obstruction with clinical decline
Temporizing or bridging options
Endoscopic decompression for sigmoid volvulus without peritonitis
Colonic stent for malignant obstruction in selected settings
Discharge criteria
Discharge rarity and constraints
Large bowel obstruction generally not discharge-eligible from ED
Discharge only if obstruction excluded and symptoms resolved with alternative diagnosis established
Treatment
Initial supportive care
Supportive bundle
NPO status
Oral meds held unless essential
Aspiration risk reduction
IV fluids
0.9% sodium chloride 500-1000 ml bolus
Repeat bolus based on perfusion and urine output
Electrolyte correction
Potassium chloride IV 10 mmol/hour via peripheral line
Magnesium sulfate IV 2 g over 1 hour if low
Antiemetics
Ondansetron IV 4 mg
Repeat 4 mg every 6-8 hours as needed
Gastric and colonic decompression
Decompression strategy
Nasogastric tube
Persistent vomiting
Significant distention
Rectal tube consideration
Distal colonic decompression attempt in selected cases
Avoid if suspected perforation
Analgesia protocols
Pain control
Fentanyl IV 25-50 micrograms
Repeat every 5-10 minutes to effect
Caution with hypotension and respiratory depression
Hydromorphone IV 0.2-0.5 mg
Repeat every 10-15 minutes to effect
Lower starting dose in older adults
Acetaminophen IV 1 g
Maximum 4 g/day
Lower maximum in liver disease
Antibiotics
Broad-spectrum coverage indications
Suspected ischemia
Lactate elevation or CT ischemia signs
Severe continuous pain pattern
Suspected perforation
Free air or peritonitis
Sepsis physiology
Preoperative prophylaxis pathway
Timing within 60 minutes of incision when operative
Redose if prolonged surgery per protocol
Empiric regimens
Piperacillin-tazobactam IV 4.5 g
Repeat every 6-8 hours
Renal dose adjustment
Ceftriaxone IV 2 g
Metronidazole IV 500 mg
Metronidazole repeat every 8 hours
Ertapenem IV 1 g
Once daily dosing
Option for beta-lactam allergy patterns based on local guidance
Definitive management by etiology
Malignant obstruction
Surgical management options
Resection with primary anastomosis in selected stable patients
Diverting stoma in unstable or high-risk anastomosis
Endoscopic stent consideration
Bridge to surgery in selected left-sided malignant obstruction
Palliative intent for unresectable disease
Diverticular stricture or inflammatory stricture
Operative pathway
Resection strategy planning
Diversion consideration if contamination or instability
Sigmoid volvulus
Endoscopic detorsion if no peritonitis
Flexible sigmoidoscopy decompression
Rectal tube placement post-detorsion
Surgery if failed endoscopic decompression or ischemia
Resection and diversion options
High recurrence risk without definitive surgery
Cecal volvulus
Surgical management as primary approach
Right hemicolectomy consideration
Cecopexy in selected cases
Thromboprophylaxis and supportive inpatient care
VTE prophylaxis
Enoxaparin SC 40 mg daily
Dose adjustment in renal impairment
Hold for active bleeding or urgent procedure per protocol
Mechanical prophylaxis
Intermittent pneumatic compression devices
Early mobilization when feasible
Evidence and guideline signals
Evidence-based positioning
Class I recommendation based on consensus for urgent surgery in peritonitis or perforation physiology
Class IIa recommendation based on guideline consensus for endoscopic decompression in uncomplicated sigmoid volvulus
ACEP Level C style evidence framing for lactate and CT ischemia signs as escalation triggers
Special Populations
Pregnancy
Pregnancy considerations
Maternal stabilization priority
Shock correction to preserve uteroplacental perfusion
Early obstetrics notification in viable gestations
Imaging adjustments
Ultrasound as adjunct only
MRI as alternative when stable and available
Medication safety
Opioids for severe pain with monitoring
Avoid NSAIDs in later pregnancy
Geriatric
Older adult risk profile
Malignancy prevalence higher
Weight loss history
Iron deficiency anemia pattern
Atypical presentations
Blunted fever response
Minimal tenderness despite ischemia
Medication sensitivity
Lower opioid starting doses
Higher delirium risk
Pediatrics
Pediatric differences
Large bowel obstruction uncommon
Hirschsprung-associated obstruction pattern
Congenital malformations
Weight-based resuscitation
Crystalloid 20 ml/kg bolus for shock
Weight-based opioid and antiemetic dosing
Early pediatric surgery involvement
Lower threshold for transfer
Radiation minimization strategy
Background
Epidemiology
Frequency and causes
Common etiologies
Colorectal cancer as leading cause in adults
Diverticular stricture as common benign cause
Volvulus epidemiology
Sigmoid volvulus association with chronic constipation
Cecal volvulus in younger adults relative to sigmoid
Pathophysiology
Mechanism and complications
Proximal dilation and pressure
Increased intraluminal pressure with ongoing gas and fluid accumulation
Bacterial overgrowth and translocation risk
Ileocecal valve competence effects
Closed-loop physiology when competent
Rapid cecal dilation and perforation risk
Ischemia pathways
Venous congestion preceding arterial compromise
Transmural necrosis leading to perforation and sepsis
Therapeutic Considerations
Management principles
Early recognition of ischemia and perforation
CT ischemia signs as high-risk markers
Lactate trend as perfusion marker
Source control emphasis
Operative intervention for perforation or necrosis
Antibiotics as adjunct, not definitive source control
Bridge strategies in malignancy
Stent vs urgent surgery based on stability and local expertise
Oncologic staging planning when stabilized
Patient Discharge Instructions
Copy discharge instructions
Discharge guidance when obstruction excluded or resolved alternative diagnosis
Hydration plan
Frequent oral fluids as tolerated
Avoid alcohol and dehydration triggers
Diet guidance
Small frequent meals
Avoid very large high-fiber boluses until fully improved
Medications
Use antiemetic as prescribed
Avoid opioids if possible due to constipation risk
Return to ED now triggers
Worsening abdominal pain
Persistent vomiting
No stool or no flatus with increasing distention
Fever or rigors
Blood in stool
Fainting or severe weakness
Follow-up plan
Primary care within 24-72 hours
Urgent GI or surgery referral if cancer or stricture concern
References
Clinical guidelines and evidence sources
Guideline sources
American Society of Colon and Rectal Surgeons clinical practice guidelines for colon cancer and obstructing colon cancer
European Society of Gastrointestinal Endoscopy guideline on colonic stenting for malignant large bowel obstruction
World Society of Emergency Surgery guidance on management of colonic volvulus and large bowel obstruction pathways
Surviving Sepsis Campaign guidelines for sepsis and septic shock resuscitation targets
Decision support and reviews
Evidence summaries
Review literature on CT findings predicting ischemia in bowel obstruction
Systematic reviews comparing stent bridge-to-surgery vs emergency surgery outcomes in left-sided malignant obstruction
Emergency general surgery texts on volvulus decompression and recurrence risk
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.