Appendicitis

David Ray Velez, MD
The Operative Review of Surgery. 2023; 1:77-92.

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Table of Contents

Pathophysiology
Presentation
Diagnosis
Treatment

Appendicitis in Pregnancy
Appendicitis in Pediatrics
Similar Pathology

Mnemonics
References

Pathophysiology

Normal Appendix Anatomy

  • Maximal Outer Diameter: 6-mm 1
    • Considered the Most Important Diagnostic Criteria to Exclude Appendicitis 1
  • Maximal Mural Thickness: 3-mm 2,3
  • Length: 8-10-cm 1
  • Luminal Capacity: 1 cc 4
    • Fluid > 0.5 cc Raises Intraluminal Pressure 4
  • “Vermiform Appendix” Simply References the “Worm-Like” Appearance
  • Blood Supply:
    • Appendicular Artery within the Mesoappendix (Off the Ileocolic Artery)
    • Venous Drainage Goes to the Portal System

Function of the Appendix

  • Reservoir for Good Bacteria After Diarrheal Infection Cleans Out the Colon 6
    • *Historically Thought to Be a Vestigial Structure without Function
  • Secretes IgA and Mucin to Assist in this Biofilm Creation 7

Anatomical Positioning 8,9

  • Retrocecal (32-62%) – Behind the Cecum (Most Common)
  • Pelvic (10-37%) – Within Pelvis
  • Subcecal (2-24%) – Inferior to & Extending from the Cecum
  • Preileal (1-19%) – Anterior to Ileum
  • Postileal (0.4-16%) – Posterior to Ileum

Appendicitis Pathology

  • Primarily Caused by Luminal Obstruction and Stasis
    • *Exact Cause is Poorly Understood 11
  • Causes of Luminal Obstruction: 11
    • Appendicolith (Fecalith at the Appendiceal Orifice)
    • Impacted Stool
    • Appendiceal/Cecal Tumor
  • Effects of Luminal Obstruction: 12
    • Swelling and Mucous Secretion
    • Increased Luminal and Intramural Pressures
    • Small Vessel Thrombosis and Lymphatic Stasis
    • Impaired Blood Flow and Venous Congestion
    • Bacterial Infection
    • Can Progress to Ischemia and Necrosis
  • Lymphoid Hyperplasia was Previously Believed to Be a Primary Cause of Appendicitis but Now Disproven – *See Below

Appendix 5

Anatomic Position of the Appendix 10

Presentation

Epidemiology 13

  • Most Common in Age 20-30’s
  • More Common in Men
  • More Common in Patients with Low Socioeconomic Status

Perforation

  • 13-20% Present with Perforation 14
  • Can Present with a Contained Walled-Off Abscess or Free Perforation
  • Most Common Site of Perforation: Antimesenteric Border Just Beyond the Point of Obstruction 15
    • Typically in the Middle Third of the Appendix
    • This Area Has the Poorest Blood Supply
  • Risk Factors for Perforation:
    • Pediatrics 16,17
      • Can Be Significantly Higher for Younger Children < 3-5 Years 17,18
      • Possibly Due to Delayed Diagnosis
      • Due Underdeveloped Omentum it is More Difficult to Wall Off an Abscess After Perforation 19
    • Age > 50 Years 20
    • Symptom Duration > 24 Hours 21
    • Presence of a Fecalith 22,23
    • WBC > 15,000 24
    • CRP > 30,000 25
    • HIV 26
    • In-Hospital Delay to Surgery May Be Associated with Increased Risk of In-Hospital Perforation – Studies Contradictory 27-29
  • Increased Mortality Rate: 5% 30
    • Compared to 0.1% for Non-Gangrenous Appendicitis and 0.6% for Gangrenous Appendicitis 30

Presentation

  • Lifetime Risk of Developing: 7-8% 31
  • Initial Periumbilical Pain that Migrates to the Right Lower Quadrant
    • 50-60% Demonstrate Migration 13
    • Initial Periumbilical Pain Caused Appendix Stretching Leading to Stimulation of T8-10 Visceral Nerve Fibers 32
    • Migrating Right Lower Quadrant Pain Caused by Inflammation of the Surrounding Parietal Peritoneum Leading to Stimulation of the Somatic Nerve Fibers 13
  • Pain Worse with Walking, Jumping or Coughing
  • Anorexia (80-85%) 13
  • Nausea and Vomiting (40-60%) 13
    • Nausea and Anorexia Occur After Pain Once Secondary Visceral Afferent Fibers Stimulate the Medullary Vomiting Center (Occurs Before Pain in Gastroenteritis)
  • Fever

Appendicitis After Resection 33

Diagnosis

Physical Exam Signs Mn
  • McBurney Sign
    • Right Lower Quadrant Tenderness at McBurney’s Point
    • McBurney’s Point: 1/3 the Distance from the Anterior-Superior Iliac Spine (ASIS) to the Umbilicus
    • Sensitivity: 50-94%; Specificity: 75-86% 13
    • Most Reliable Finding
  • Rovsing Sign
    • Right Lower Quadrant Pain with Left Lower Quadrant Palpation
    • Sensitivity: 22-68%; Specificity: 58-96% 13
  • Iliopsoas/Psoas Sign
    • Right Lower Quadrant Pain on Extension of the Right Thigh
    • Indicates: Retrocecal Appendix
    • Sensitivity: 13-42%; Specificity: 79-97% 13
  • Obturator Sign
    • Right Lower Quadrant Pain on Internal Rotation of Right Thigh
    • Indicates: Pelvic Appendix
    • Likely to Associated with Dysuria & Diarrhea
    • Sensitivity: 8%; Specificity: 94% 13
Diagnosis
  • Labs: WBC and CRP
  • First-Line Imaging: Computed Tomography (CT)
    • Study of Choice by the American College of Radiology 34,35
    • IV Contrast Preferred, Oral Contrast Not Necessary 36
    • Sensitivity: 91%; Specificity 90% 13
  • Alternative Imaging Modalities:
    • Ultrasound (US)
      • Some Consider as an Initial Imaging Test Although Negative US Does Not Rule Out Appendicitis and Should Be Followed by CT if US Equivocal 37
      • Preferred for Pediatrics or Pregnant Women to Limit Radiation Exposure 13
      • Sensitivity: 78%; Specificity: 83% 13
    • Magnetic Resonance Imaging (MRI)
      • Most Commonly Used in Pediatrics or Pregnant Women if US Equivocal 13
      • More Expensive and Less Familiarity
  • Radiographic Findings:
    • Appendix Noncompressible
    • Appendix Distended ≥ 6-7 mm
    • Appendix Wall Thickening ≥ 3 mm
    • Appendicolith (40%) 38
      • Associated with More Severe Inflammation and Increases Risk for Perforation
    • Periappendiceal Fluid and Fat Stranding
Complicated Appendicitis Definitions 40
  • Gangrenous Appendicitis with or without Perforation
  • Appendicitis with an Intraabdominal Abscess
  • Appendicitis with Periappendicular Contained Phlegmon
  • Appendicitis with Periappendicular Purulent/Free Fluid
Diagnostic Scoring Systems Prior to Imaging
  • Alvarado Scoring System 41 Mn
    • The Most Commonly Used System in Adults
    • Points:
      • Tenderness in RLQ (2)
      • Migration to RLQ (1)
      • Rebound Tenderness (1)
      • Anorexia (1)
      • Nausea/Vomiting (1)
      • Elevated Temperature (1)
      • Leukocytosis; WBC > 10,000 (2)
      • Shift of Neutrophils (1)
    • Interpretation: 42
      • Low Scores (0-3): Evaluate Other Etiologies (No CT Indicated)
      • Intermediate Scores (4-6): CT Scan
      • High Scores (7-10): Surgical Consultation
    • Low Scores Are Better to “Rule-Out” Appendicitis than High Scores Are to “Rule-In”
      • Score < 3-4 to “Rule-Out” Appendicitis Has 96% Sensitivity
      • Score > 6-7 to “Rule-In” Appendicitis Has 58-88% Sensitivity
  • Pediatric Appendicitis Score (PAS) 43
    • Most Commonly Used in Pediatrics
    • Points:
      • RLQ Tenderness (2)
      • Pain with Cough, Percussion or Hopping (2)
      • Anorexia (1)
      • Nausea/Emesis (1)
      • Migration of Pain (1)
      • Fever (1)
      • Leukocytosis; WBC > 10,000 (1)
      • Neutrophilia; ANC > 7,500 (1)
    • Interpretation: 44
      • Low Scores (0-3): Evaluate Other Etiologies
      • Intermediate Scores (4-6): Imaging
      • High Scores (7-10): Imaging vs Surgery
  • Additional Scoring Systems:
    • Appendicitis Inflammatory Response (AIR) Score 45
    • RIPASA (Raja Isteri Pengiran Anak Saleha Appendicitis) Score 46
    • Eskelinen Score 47
    • Ohmann Score 48
    • Tzanakis Score 49
    • Lintula Score 50
    • Fenyo-Lindberg Score 51
    • Karaman Score 52

Appendicitis with Fecalith 39

Perforated Appendicitis 39

Treatment

Definitive Management

  • Uncomplicated Appendicitis: Laparoscopic Appendectomy
    • *See Appendectomy
    • May Consider Nonoperative Management with Antibiotics Alone for Select Patients – *See Below
  • Complicated Appendicitis (Phlegmon/Abscess): Antibiotics & Interval Appendectomy at 6-8 Weeks
    • Percutaneous Drainage if Abscess > 3-4 cm
    • Antibiotic Course:
      • After Percutaneous Drainage: 4 Days 54
      • If Unable to Perform Percutaneous Drainage: 7 Days
    • 80% Successful in Avoiding Appendectomy on Initial Admission 55
  • Free Perforation: Appendectomy

Intraoperative Findings

  • Normal Appendix: Historically Recommended That the Appendix was Always Resected Even if Normal at Diagnostic Laparoscopy for Acute Right Iliac Fossa Pain
    • Goal: Prevent Risk of Diagnostic Confusion in the Future
    • Debated in Modern Practice 56
  • Friable Base: Partial Cecectomy
    • Take Care to Preserve the Ileocecal Valve
  • Suspect Chron’s Disease and Cecum Inflamed: No Intervention

Nonoperative Management

  • Some Promote Antibiotic Treatment Alone for Uncomplicated Acute Appendicitis 57
    • Not Recommended for Complicated Appendicitis
  • *In General, Surgical Management is Preferred but May Consider Nonoperative Management if Unfit for Surgery or the Patient Refuses Surgery
  • Benefits:
    • Most Respond Clinically
    • Faster Return to Work (Not for Complicated/Perforated Cases)
    • No Increased Perforation Rate
    • 89-91% Are Able to Avoid Surgery at Initial Admission
  • Negatives:
    • High Recurrence Rates
      • 29% Require Appendectomy by 90 Days 57
        • 25% Without Appendicolith 57
        • 41% With Appendicolith 57
      • 14-40% Require Appendectomy within the First Year 57-60
      • 40-50% Require Appendectomy within the First 5-Years 57,61
      • 28x Higher Rates of Complications 57
    • Treatment Efficacy at 1-Year: 62
      • Nonoperative Management: 63.8%
      • Surgical Management: 93%
    • Contraindicated if Fecalith Present – High Rate of Complicated Appendicitis that May be Underestimated on Imaging
  • Immunocompromised and Significant Comorbidity Patients Have Mostly Been Excluded from Prior Studies with Uncertain Efficacy

Interval Appendectomy

  • Definition: Appendectomy Done After a Trial of Nonoperative Management with Antibiotics
    • Generally Done After 6-8 Weeks
  • Comparison to an Immediate Appendectomy for Complicated Appendicitis:
    • Decreased Risk of Complications (SBO, Prolonged Ileus, Surgical Site Infection & Reoperation) 63
    • May Have Longer Return to Activity (Debated) 63,64
  • Some Recommend Against Interval Appendectomy Due to Low Recurrence Rate, Although One of the Most Compelling Reason for Interval Appendectomy is the Increased Risk of Neoplasm After Perforation
    • Risk of Recurrence: 5-38%
    • Risk of Neoplasm After Interval Appendectomy for Complicated Appendicitis: 11% 65
    • If Interval Appendectomy is Forgone, Patients Over 40 Years Old Should Have an Interval Colonoscopy and CT 30

Incidental (Prophylactic) Appendectomy

  • Definition: Appendectomy During Another Separate Procedure without Evidence of Appendicitis
  • Goal: Eliminate Future Risk of Appendicitis
  • Indications Not Defined
  • Associated with Complications and Generally Avoided 66
  • Contraindications: 67
    • Unstable Hemodynamics
    • Established Crohn’s Disease
    • Inaccessible Appendix
    • Predetermined Plan for Radiation Treatment
    • Pathologically or Iatrogenically Immunosuppressed
  • Most Often Done for Patients Under Age 30-35 Years (Highest Incidence) During Hysterectomy, Cholecystectomy, Sigmoidectomy, or Trauma Laparotomy

Laparoscopic Appendectomy 53

Appendicitis in Pregnancy

General Information

  • Overall Pregnant Women are Less Likely than Nonpregnant Women to Have Appendicitis 68
  • The Most Common Non-Obstetric Indication for Surgery During Pregnancy
  • Appendix Perforation is More Common – Possibly Due to Diagnostic Challenges and Hesitancy to Operate on Pregnant Women 69,70

Considerations by Trimester

  • First Trimester:
    • Appendicitis is the Most Common Cause of Acute Abdominal Pain
  • Second Trimester:
    • Most Frequent Trimester 68
  • Third Trimester:
    • Lowest Overall Rate of Appendicitis 71
    • Most Likely to Perforate 69,70

Risks/Outcomes

  • Maternal Morbidity and Mortality are Similar to Nonpregnant Women 72
  • Uncomplicated Appendicitis: 73,74
    • Fetal Loss: 1.5-2.0%
    • Preterm Labor: 6%
  • Complicated Appendicitis: 73,74
    • Fetal Loss: 8-36%
    • Preterm Labor: 11%
  • Highest Risk for Fetal Mortality: Appendix Rupture
  • In General, Appendectomy During Pregnancy Does Not Negatively the Child 75

Presentation

  • Only 50-60% Have a Classical Clinical Presentation
  • May Instead Present with Heartburn, Flatulence, or Diarrhea
  • Location of Pain:
    • Most Commonly at McBurney’s Point Regardless of Trimester 76,77
    • May Migrate to the Right Mid-Upper Quadrant in the Third Trimester Due to a Gravid Uterus 78,79
  • Leukocytosis May Be Normal in Pregnancy 80

Treatment

  • Uncomplicated Appendicitis: Appendectomy
    • Optimal Approach Remains Inconclusive 81
    • Laparoscopic vs Open Appendectomy
      • Laparoscopic Associated with Lower Overall Complications and Shorter Length of Stay 81
      • Laparoscopic Associated with Higher Rate of Fetal Loss (Odds Ratio 1.82) 81,82
      • Similar Rates of Preterm Labor 82
    • Laparoscopic Trocar Placement: *See Appendectomy
    • Open Incision: Generally Recommended to Make at McBurney’s Point or the Site of Maximal Pain (Possibly More Cephalad)
  • Complicated Appendicitis:
    • Phlegmon/Abscess: Debated
      • Poor Evidence to Guide Decision Making
      • Consider Antibiotics with Percutaneous Drainage and Interval Appendectomy (Similar to Nonpregnant Patients) vs Immediate Appendectomy
    • Free Perforation: Open Appendectomy

Appendicitis in Pediatrics

Appendicitis in Pediatrics

Similar Pathology

Appendiceal Lymphoid Hyperplasia

  • Definition: Increased Size of Lymphoid Tissue within the Appendix
  • A Physiologic Response to Inflammation 83
  • Often Associated with Inflammatory Conditions Such as Viral Gastroenteritis or Mesenteric Adenitis 83
  • Previously Believed to Be a Primary Cause of Appendicitis but Now Disproven 83
  • Can Mimic Appendicitis with a Noncompressible and Dilated Appendix 84
  • Most Successful Parameters to Distinguish Appendicitis from Lymphoid Hyperplasia: 84
    • Periappendiceal Fluid Collection
    • Lamina Propria Thickness ≤ 1 mm

Mesenteric Lymphadenitis (Mesenteric Adenitis)

  • Also Known as “Pseudoappendicitis”
  • Definition: Mesenteric Lymph Node Inflammation
    • A Self-Limiting Inflammatory Condition that Resolves Over 1-10 Weeks
    • Can Be a Primary/Nonspecific Etiology or Secondary
  • Often Presents Similar to Appendicitis
  • Most Common in Pediatrics
    • More Common than Appendicitis in the First Decade of Life 85
  • Secondary Causes: 86
    • Viral Infection – Most Common Cause
      • Gastroenteritis
      • Upper Respiratory Infection (URI)
    • Bacterial Infection
    • Inflammatory Bowel Disease
    • Lymphoma
  • Diagnosis: Generally Made by Imaging (US or CT) 85
    • Must First Rule Out Other Diagnoses
  • Treatment: Supportive Care (Fluid Resuscitation and NSAID’s) 85,86
    • No Biopsy or Surgery Necessary

Periappendicitis

  • Definition: Appendiceal Serosal Inflammation without Mucosal Inflammation
    • Caused by Non-Appendiceal Inflammation
  • Often Presents Similar to Appendicitis
  • 1-5% of Appendices Resected for Clinical Acute Appendicitis are Found to Have Periappendicitis Alone 87
  • Causes: 87
    • Salpingitis (Gonococcal or Chlamydial) – Most Common Cause 87
    • Pelvic Inflammatory Disease (PID)
    • Peritoneal Tuberculosis
    • Inflammatory Bowel Disease (IBD)
    • Infectious Colitis
    • Diverticulitis
    • Urologic Disease
    • Distant Perforation Elsewhere
    • Colonic Neoplasia
    • Valentino’s Syndrome: Periappendicitis Caused by a Perforated Gastric/Duodenal Ulcer 88
  • Diagnosis May Be Difficult to Make Preoperatively
  • Treatment: Based on Underlying Cause

Appendiceal Mucocele (Non-Neoplastic Mucinous Lesion/Retention Cyst)

Appendix Cancer

Mnemonics

Signs of Appendicitis

  • McBurney Sign – “Burns” Right Over the Appendix
  • Rovsing Sign – Think “Roving” Pain Elicited from a Distant Site
  • Psoas Sign (Pso-Po) – Posterior (Retrocecal Position)
  • Obturator Sign (Ob-Ob) – Obstetrics (Pelvic Location & Internal Rotation to Pelvis)

Alvarado Score

  • Often Referred to as “MANTRELS” Score
  • M: Migration to RLQ (1)
  • A: Anorexia (1)
  • N: Nausea/Vomiting (1)
  • T: Tenderness in RLQ (2)
  • R: Rebound Tenderness (1)
  • E: Elevated Temperature (1)
  • L: Leukocytosis; WBC > 10,000 (2)
  • S: Shift of Neutrophils (1)

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