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Approach to the Critical Patient
Immediate priorities
Airway and breathing threats
Distress from peritonitis or sepsis
Tachypnea from metabolic acidosis
Splinting from abdominal pain
Oxygenation status
SpO2 < 92% on room air
Supplemental oxygen titration
If altered mental status with sepsis, airway protection planning
Aspiration risk with vomiting
Rapid sequence intubation preparation
Circulation and sepsis threats
Shock physiology
SBP < 90 mmHg
MAP < 65 mmHg
Sepsis screening from perforation or peritonitis
Suspected intraabdominal infection with organ dysfunction
Lactate >= 2 mmol/l
If septic shock, broad spectrum antibiotics within 1 hour
Class I recommendation
Source control planning with surgery
Key early branching
Uncomplicated appendicitis pattern
Localized right lower quadrant pain
No free air or abscess on imaging
Complicated appendicitis pattern
Perforation with peritonitis
Appendiceal abscess or phlegmon
If diffuse peritonitis or sepsis, urgent surgical consult
Source control prioritized
Resuscitation in parallel
Resuscitation and targets
Initial resuscitation
Volume status correction
Balanced crystalloid bolus
Reassess perfusion after each bolus
Perfusion targets
MAP >= 65 mmHg
Urine output >= 0.5 ml/kg/hour
Lactate clearance trend
Repeat within 2 to 4 hours if elevated
Persistent elevation as inadequate source control marker
Monitoring bundle
Continuous vital sign monitoring
Heart rate trend
Blood pressure trend
Serial abdominal exams
Progression to peritonitis
Pain migration pattern
NPO status maintained
Pending surgical decision
Aspiration risk reduction
Immediate consults and decisions
Surgical consultation triggers
Confirmed appendicitis on imaging
General surgery for appendectomy
Timing within 24 hours acceptable if no perforation
Complicated disease
Abscess for percutaneous drainage consideration
Diffuse peritonitis for urgent operation
Key decision points
Operative versus nonoperative management
Patient preference and risk tolerance
Presence of appendicolith
If pregnant or pediatric, radiation-sparing imaging first
Ultrasound as initial study
MRI when ultrasound equivocal
History
Presentation pattern
Classic syndrome
Periumbilical pain
Initial vague visceral pain
Radiating to right lower quadrant
Pain migration to right lower quadrant
Best single historical clue for ruling in
Localization over 12 to 24 hours
Anorexia
Common early symptom
Absence lowers but does not exclude
Associated symptoms
Nausea and vomiting
Typically follows pain onset
Vomiting before pain suggests alternative
Low grade fever
High fever suggests perforation
Rigors as complication marker
Anorexia and obstipation
Reduced bowel function
Diarrhea in pelvic appendix
Atypical presentations and pitfalls
Atypical pain localization
Retrocecal appendix
Flank or back pain
Minimal anterior tenderness
Pelvic appendix
Suprapubic pain
Urinary or rectal symptoms
Diagnostic delay risks
Vague symptoms in early presentation
Pain not yet localized
Reassessment with serial exams
Atypical groups
Older adults with blunted response
Young children with nonspecific symptoms
Risk factors and historical clues
Demographic risk
Peak incidence ages 10 to 30 years
Lifetime risk 7 to 8 percent
Slight male predominance
Family history association
First degree relative risk
Genetic predisposition signal
Historical clues for complication
Duration of symptoms beyond 48 hours
Higher perforation risk
Abscess formation risk
Prior antibiotic-treated episode
Recurrence risk
Appendicolith association
Physical Exam
Vitals and general
Stability snapshot
Temperature
Low grade fever common
High fever >= 39 C as perforation marker
Heart rate
Tachycardia from pain or sepsis
Rising trend as deterioration marker
Blood pressure
SBP < 90 mmHg as shock marker
MAP < 65 mmHg as perfusion marker
General appearance
Patient lying still
Movement worsens peritoneal pain
Knees drawn up for comfort
Toxic appearance
Diaphoresis
Pallor
Abdominal exam
Localized findings
Right lower quadrant tenderness
McBurney point maximal tenderness
Best ruling-in physical sign
Guarding and rigidity
Voluntary guarding early
Involuntary rigidity as peritonitis
Rebound tenderness
Peritoneal irritation
Localized to right lower quadrant
Provocative signs
Rovsing sign
Left lower quadrant palpation causes right pain
Referred peritoneal irritation
Psoas sign
Pain on right hip extension
Retrocecal appendix association
Obturator sign
Pain on internal hip rotation
Pelvic appendix association
Complication and special exams
Peritonitis screen
Diffuse rigidity
Generalized peritonitis from perforation
Surgical emergency
Absent bowel sounds
Ileus from inflammation
Peritoneal sign correlation
Adjunct exams
Rectal and pelvic exam selectively
Pelvic appendix tenderness
Gynecologic mimics in females
PITFALLS
Normal exam early does not exclude
Reassessment when suspicion persists
Differential Diagnosis
Life threats and surgical mimics
Immediate threats
Perforated appendicitis with sepsis
ICD-10 K35.32 association
Diffuse peritonitis
Ruptured ectopic pregnancy
Positive pregnancy test
Hemodynamic instability
Mesenteric ischemia
Pain out of proportion
Lactic acidosis
Common surgical mimics
Acute diverticulitis
Left lower quadrant in sigmoid disease
Cecal diverticulitis right sided overlap
Cholecystitis
Right upper quadrant tenderness
Murphy sign
Small bowel obstruction
Distension and vomiting
Prior surgery history
Gynecologic and urologic differentials
Gynecologic causes
Ovarian torsion
Sudden severe unilateral pain
Adnexal mass on ultrasound
Pelvic inflammatory disease
Cervical motion tenderness
Vaginal discharge
Ruptured ovarian cyst
Mid cycle onset
Free fluid in pelvis
Urologic and other causes
Ureteric colic
Colicky flank to groin pain
Hematuria
Mesenteric adenitis
Viral prodrome in children
Self limited course
Gastroenteritis
Diarrhea predominant
Diffuse rather than localized pain
Laboratory Tests
Core labs
Infection and inflammation
Complete blood count
Leukocytosis supports diagnosis
Normal count does not exclude
CRP elevation
Adds to inflammatory picture
Combined with WBC improves accuracy
Neutrophil predominance
Left shift supports inflammation
Used in inflammatory response scoring
Metabolic and organ function
Electrolytes and renal function
Dehydration from vomiting
Baseline before contrast imaging
Liver and lipase
Exclude biliary or pancreatic mimics
Right upper quadrant overlap
Pregnancy and urinalysis
Beta hCG
All persons of childbearing potential
Exclude ectopic pregnancy
Guides radiation-sparing imaging
Urinalysis
Pyuria from adjacent appendiceal inflammation
Exclude urinary tract infection
Hematuria suggests ureteric colic
Sepsis and perfusion labs
Lactate
>= 2 mmol/l as hypoperfusion marker
Repeat within 2 to 4 hours if elevated
Blood cultures
Severe illness or septic presentation
Prior to antibiotics when feasible
Type and screen
Preoperative preparation
Anticipated operative blood loss
Diagnostic Tests
Scoring Systems
Risk stratification tools
Alvarado score
Migratory right iliac fossa pain 1 point
Anorexia 1 point
Nausea or vomiting 1 point
Tenderness right lower quadrant 2 points
Rebound tenderness 1 point
Elevated temperature 1 point
Leukocytosis 2 points
Left shift of neutrophils 1 point
Score <= 4 low risk
Score 5 to 6 indeterminate
Score >= 7 high probability
Appendicitis Inflammatory Response score
Incorporates CRP and WBC and neutrophil percentage
Stratifies low intermediate high risk
Pediatric Appendicitis Score
Validated in children
Guides imaging versus observation
Limitations
Scores stratify rather than confirm
Imaging required in indeterminate range
Clinical trajectory supersedes single score
MRI
MRI abdomen and pelvis role
Preferred when ultrasound equivocal in pregnancy
Avoids ionizing radiation
High sensitivity and specificity for appendicitis
Second line in children
When ultrasound nondiagnostic
Avoids CT radiation
Findings
Appendiceal diameter > 7 mm
Periappendiceal fluid and fat stranding
Limitations
Availability and cost
Longer acquisition time
CT
CT abdomen and pelvis indications
First line in nonpregnant adults
Sensitivity over 90 percent
Specificity over 90 percent
Intravenous contrast generally recommended
Improves diagnostic accuracy
Renal function and allergy review
Findings
Appendiceal diameter > 6 mm
Wall thickening and fat stranding
Appendicolith in approximately 25 percent
Complication assessment
Free air indicating perforation
Abscess or phlegmon
Evidence and guidance
CT more reliable than ultrasound in adults
AAST guideline support
Reduces negative appendectomy rate
Ultrasound
Graded compression ultrasound
Preferred initial study in children and pregnancy
Avoids ionizing radiation
Operator dependent sensitivity
Diagnostic findings
Noncompressible blind-ending tubular structure
Diameter > 6 mm
Target sign on cross section
Secondary signs
Periappendiceal fluid
Increased echogenic fat
Limitations and adjuncts
Nonvisualization does not exclude
Proceed to MRI or CT when high suspicion
Body habitus limitation
Point of care ultrasound
Free fluid screen
Excludes gynecologic mimics
Disposition
Level of care selection
Admission indications
Confirmed appendicitis
Surgical admission for appendectomy
NPO and IV antibiotics
Complicated disease
Perforation or abscess
Need for drainage or operation
Sepsis or hemodynamic instability
SBP < 90 mmHg
Lactate >= 2 mmol/l with infection
ICU indications
Septic shock
Vasopressor requirement
Rising lactate despite resuscitation
Severe peritonitis with organ dysfunction
Acute kidney injury
Respiratory compromise
Discharge and observation criteria
Observation candidates
Equivocal imaging with low risk score
Serial abdominal exams
Repeat labs and imaging if worsening
Nonoperative management candidate
Uncomplicated appendicitis without appendicolith
Reliable follow up
Follow up plan
Surgical follow up after discharge
Wound check after appendectomy
Recurrence counseling after antibiotics
Interval evaluation for malignancy
Age >= 35 years after nonoperative management
Colonoscopy or imaging surveillance
Treatment
Resuscitation and supportive care
Immediate measures
NPO status
Pending operative decision
Aspiration risk reduction
Intravenous fluids
Balanced crystalloid resuscitation
Correct dehydration from vomiting
Antiemetics
Ondansetron 4 mg IV for nausea
Reduces aspiration risk
Pain management
Multimodal analgesia priority
Does not delay diagnosis or mask peritonitis
AAFP supported approach
Acetaminophen
1 g IV or PO every 6 hours
Maximum 4 g per 24 hours
Opioids as needed
Morphine 0.1 mg/kg IV titrated
Reassess pain after dosing
Preoperative antibiotics
Timing and rationale
Administer as soon as diagnosis made
Reduces surgical site infection
Class I recommendation
Single preoperative dose for uncomplicated disease
Postoperative antibiotics not required
WSES and JAMA guidance
First line regimens
Cefoxitin IV
2 g IV preoperatively
Covers gram negatives and anaerobes
Cefazolin plus metronidazole
Cefazolin 2 g IV
Metronidazole 500 mg IV
Cefotetan IV
2 g IV preoperatively
Alternative cephamycin
If severe beta lactam allergy
Ciprofloxacin plus metronidazole
Ciprofloxacin 400 mg IV
Metronidazole 500 mg IV
Aztreonam plus metronidazole
Aztreonam 2 g IV
Metronidazole 500 mg IV
Surgical management
Laparoscopic appendectomy
Gold standard and procedure of choice
Shorter hospitalization 2.6 versus 3.4 days
Earlier return to activity 14 versus 21 days
Lower surgical site infection
48 to 70 percent decrease versus open
Shorter parenteral analgesia duration
Timing flexibility
Safe delay within 24 hours
No increased adverse outcomes
Open appendectomy
Reserved indications
Extensive adhesions
Hemodynamic instability precluding laparoscopy
Conversion considerations
Difficult anatomy
Inability to identify appendix
Nonoperative and complicated management
Antibiotic-only therapy
Selected uncomplicated appendicitis
Approximately 60 percent treated successfully
Acknowledged safe option in guidelines
Typical regimen
Ertapenem 1 g IV daily initial
Followed by oral cefdinir and metronidazole 7 to 10 days
Appendicolith reduces success
Appendectomy rate 41 versus 25 percent
Complication rate 20.2 versus 3.5 percent
If no improvement within 48 hours, appendectomy
Worsening symptoms
Diffuse peritonitis or sepsis
Complicated appendicitis
Appendiceal abscess in stable patient
Percutaneous drainage plus antibiotics
Avoids immediate difficult surgery
Postoperative antibiotics in complicated disease
Short course 2 to 3 days
De escalation based on cultures
Special Populations
Pregnancy
Pregnancy considerations
Most common nonobstetric surgical emergency
Diagnosis challenged by displaced appendix
Right upper quadrant pain in later gestation
Imaging approach
Ultrasound as initial study
MRI when ultrasound equivocal
CT only when benefits outweigh risks
Antibiotic selection
Beta lactams generally preferred
Avoid tetracyclines and fluoroquinolones when possible
Surgical approach
Laparoscopic appendectomy feasible in pregnancy
Obstetric involvement for fetal monitoring
Geriatric
Older adult features
Atypical presentation
Blunted fever and leukocytosis
Delayed presentation common
Higher perforation rate
Diagnostic delay contribution
Higher morbidity and mortality
Malignancy consideration
Appendiceal or cecal tumor mimic
Interval colonoscopy after nonoperative care
Comorbidity impact
Renal dosing adjustment
Perioperative risk assessment
Pediatrics
Pediatric differences
Diagnostic challenge
Nonspecific symptoms in young children
Higher perforation rate when delayed
Imaging preference
Ultrasound first to avoid radiation
MRI when ultrasound nondiagnostic
Reliable pediatric exam signs
Decreased bowel sounds
Positive psoas obturator and Rovsing signs
Weight based antibiotics
Piperacillin tazobactam 100 mg/kg per dose IV every 8 hours
Ceftriaxone 50 mg/kg IV daily plus metronidazole 10 mg/kg IV every 8 hours
Background
Epidemiology
Frequency and burden
Most common reason for emergency abdominal surgery worldwide
Annual incidence 96.5 to 100 per 100,000 adults
Lifetime risk 7 to 8 percent
Age distribution
Peak incidence ages 10 to 30 years
Occurs across all ages
Diagnostic accuracy
Over 90 percent with history exam labs and imaging
Appendicolith present in approximately 25 percent
Pathophysiology
Mechanisms
Luminal obstruction
Fecalith or appendicolith
Lymphoid hyperplasia
Progressive inflammation
Increased intraluminal pressure
Venous congestion and ischemia
Bacterial proliferation
Wall invasion
Transmural inflammation
Complication pathways
Perforation with peritonitis
Abscess and phlegmon formation
Therapeutic Considerations
Management strategy principles
Operative versus nonoperative decision
Patient preference and recurrence risk
Appendicolith favors surgery
Antibiotic stewardship
Single preoperative dose for uncomplicated disease
Short course for complicated disease
Source control priority
Drainage of abscess in stable patients
Urgent operation for diffuse peritonitis
Surveillance after nonoperative care
Recurrence monitoring
Counsel on return symptoms
Higher recurrence with appendicolith
Neoplasm detection
Age >= 35 years follow up
Interval imaging or colonoscopy
Patient Discharge Instructions
copy discharge instructions
Appendicitis home care after treatment
Take all antibiotics exactly as prescribed until finished
Rest and gradually increase activity as tolerated
Keep surgical incisions clean and dry
Use prescribed pain medication as directed
Warning signs to return to the ER
Worsening or spreading abdominal pain
Fever above 38.5 C or shaking chills
Persistent vomiting or inability to keep fluids down
Redness pus or swelling at the incision
Abdominal swelling or hardness
Fainting or feeling lightheaded
Follow up
Surgical follow up appointment as scheduled
Wound check and suture or staple removal if needed
Return promptly if symptoms recur after antibiotic-only treatment
Recovery tips
Avoid heavy lifting until cleared by your surgeon
Stay hydrated and eat as tolerated
Walk regularly to reduce clot risk
References
Guidelines and key sources
Guideline sources
WSES Jerusalem Guidelines 2025 diagnosis and treatment of acute appendicitis
AAST emergency general surgery guideline summaries acute appendicitis
American College of Surgeons gastrointestinal surgical emergencies guidance
Key reviews and trials
JAMA review diagnosis and management of acute appendicitis in adults 2021
NEJM treatment of acute uncomplicated appendicitis 2021
AAFP acute appendicitis efficient diagnosis and management 2018
Decision tools and coding
Alvarado score and Appendicitis Inflammatory Response score
Pediatric Appendicitis Score
ICD-10 K35 acute appendicitis coding family
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.