Special Surgery 25. Acute Appendicitis: Symptomatics, Diagnostics, Treatments

I. Definition, Etiology and Pathogenesis

Definition

• Acute appendicitis = acute inflammation of the vermiform appendix
• One of the most common causes of acute surgical abdomen
• Typical site: right iliac fossa / right lower quadrant (RLQ)
• May progress from catarrhal inflammation → phlegmonous/suppurative → gangrenous → perforated appendicitis

Anatomical Points

• Appendix arises from cecum at convergence of taeniae coli
• Position is variable:

• Retrocecal: most common; pain may be flank/back; psoas sign possible
• Pelvic: suprapubic pain, diarrhea, urinary symptoms; obturator sign possible
• Pre-ileal/post-ileal: pain may be less localized early
• Subhepatic appendix: can mimic cholecystitis

Etiology

• Main mechanism: luminal obstruction
• Causes:

• Lymphoid hyperplasia: common in children/young adults, often after viral infection
• Fecalith / appendicolith
• Foreign body
• Parasite infection
• Neoplasm: carcinoid/NET, adenocarcinoma, mucinous neoplasm, cecal cancer
• Crohn disease or other inflammatory narrowing

Pathogenesis

• Appendiceal obstruction → stasis of mucosal secretion
• Stasis → bacterial overgrowth + local mucosal inflammation
• Inflammation → transmural spread of infection
• Increasing intraluminal pressure → venous outflow obstruction
• Venous obstruction → edema of appendiceal wall
• Edema + pressure → arterial inflow compromise
• Ischemia → gangrenous appendicitis +/- perforation
• Perforation → localized abscess/phlegmon or diffuse peritonitis

Microbiology

• Polymicrobial intestinal flora
• Common organisms:

• Gram-negative rods: Escherichia coli and other Enterobacterales
• Anaerobes: Bacteroides fragilis group
• Streptococci and other mixed enteric bacteria

II. Symptomatics and Complications

Typical Clinical Features

• Abdominal pain:

• Starts centrally/periumbilically due to visceral pain
• Then localizes to RLQ when parietal peritoneum becomes irritated
• Classical point: McBurney point = junction of lateral and middle third from right ASIS to umbilicus
• Lanz point = right third of line connecting both ASIS
• Pain worsens with coughing, walking, movement or transport

• Anorexia: very common
• Malaise
• Nausea and vomiting:

• Usually vomiting occurs after pain starts
• Vomiting before pain suggests gastroenteritis more than appendicitis

• Low-grade fever
• Constipation or diarrhea
• Urinary frequency/dysuria if pelvic appendix irritates bladder/ureter

Physical Signs

• McBurney point tenderness
• Localized guarding in RLQ
• Blumberg sign / rebound tenderness:

• Pain when examiner suddenly releases abdominal wall compression
• Suggests peritoneal irritation

• Rovsing sign:

• RLQ pain during palpation of the left lower quadrant

• Psoas sign:

• RLQ pain by passive extension of right hip
• Or pain with flexion of right hip against resistance with stretched leg
• Suggests retrocecal appendix irritating psoas muscle

• Obturator sign:

• RLQ/hypogastric pain during internal rotation of flexed right hip and knee
• Suggests pelvic appendix irritating obturator internus muscle

• Rectal or pelvic tenderness may occur with pelvic appendix
• Diffuse rigidity, severe rebound and sepsis → perforation/diffuse peritonitis

Atypical Presentations

• Children:

• Rapid progression
• Higher perforation risk
• May present with diarrhea, fever, irritability

• Elderly:

• Less pain, less fever, delayed presentation
• Higher perforation and malignancy risk

• Pregnancy:

• Symptoms can be atypical
• Appendix may be displaced upward with gestational age
• Early diagnosis is important because perforation increases fetal and maternal risk

• Retrocecal appendix:

• Less anterior tenderness
• Flank/back pain or psoas irritation

• Pelvic appendix:

• Suprapubic pain, diarrhea, tenesmus or urinary symptoms

Complications

• Perforation → localized or diffuse peritonitis
• Appendiceal abscess
• Appendiceal phlegmon / inflammatory mass
• Sepsis and septic shock
• Postoperative wound infection
• Postoperative intra-abdominal abscess
• Adhesive small bowel obstruction later
• Pylephlebitis: septic thrombophlebitis of portal venous system, rare

III. Diagnostics and Differential Diagnosis

Clinical Assessment

• Diagnosis is based on history + physical examination + labs + selective imaging
• Assess for peritonitis and sepsis first
• Clinical scores can support risk stratification:

• Alvarado score: useful to exclude in low-risk patients, not enough alone to confirm in adults
• AIR score / Adult Appendicitis Score: useful adult risk stratification tools
• Pediatric Appendicitis Score: supportive in children, not diagnostic alone

• High suspicion with peritonitis → urgent surgical review
• Intermediate probability → observation and systematic imaging
• Low probability → consider discharge/observation with clear return instructions depending on clinical situation

Laboratory Tests

• CBC:

• Leukocytosis with neutrophilia is typical
• Normal WBC does not fully exclude appendicitis

• CRP:

• Often elevated
• Higher values suggest advanced/complicated inflammation

• Electrolytes, urea/creatinine if vomiting, dehydration or operation likely
• Urinalysis:

• Can be normal
• Mild pyuria/hematuria can occur if appendix is near ureter/bladder
• Marked urinary findings suggest urological pathology

• Pregnancy test in women of reproductive age
• Blood gas/lactate if sepsis, shock or ischemia suspected

Imaging

Ultrasound

• First-line in children and pregnant women
• Useful first imaging test when skilled operator is available
• Findings:

• Non-compressible blind-ending tubular structure in RLQ
• Outer diameter usually >6 mm
• Wall thickening
• Appendicolith with shadowing
• Periappendiceal fluid or abscess
• Inflamed surrounding fat

• Limitations: operator-dependent, obesity, bowel gas, retrocecal appendix

CT Abdomen/Pelvis with IV Contrast

• Most accurate commonly used imaging test in adults
• Indicated when diagnosis is uncertain, patient is older, differential is broad, or complication is suspected
• Findings:

• Dilated appendix >6 mm
• Wall thickening and enhancement
• Periappendiceal fat stranding
• Appendicolith
• Periappendiceal fluid, abscess, phlegmon
• Extraluminal air or free fluid in perforation
• Alternative diagnosis if not appendicitis

• Low-dose CT is preferred when appropriate to reduce radiation

MRI

• Useful in pregnancy after inconclusive ultrasound if available
• Also useful in children as second-line imaging where available
• No ionizing radiation

Classification by Severity

• Uncomplicated appendicitis:

• Inflamed appendix without perforation, abscess, phlegmon or diffuse peritonitis

• Complicated appendicitis:

• Gangrenous appendicitis
• Perforation
• Appendiceal abscess
• Appendiceal phlegmon
• Diffuse peritonitis

Differential Diagnosis

• Gastrointestinal:

• Gastroenteritis
• Meckel diverticulitis
• Cecal or sigmoid diverticulitis
• Crohn disease / terminal ileitis
• Mesenteric lymphadenitis
• Colon cancer, especially in elderly/right-sided symptoms
• Epiploic appendagitis

• Urological/retroperitoneal:

• Renal colic
• Pyelonephritis
• Urinary tract infection
• Testicular torsion in males

• Gynecological:

• Ectopic pregnancy
• Ovarian torsion
• Ruptured ovarian cyst
• Pelvic inflammatory disease
• Mittelschmerz / menstrual pain

• Other surgical abdomen:

• Perforated peptic ulcer
• Acute cholecystitis with low/subhepatic appendix differential
• Pancreatitis
• Bowel obstruction

IV. Treatment

Initial Management

• Surgical assessment
• NPO / nil per os
• IV cannula, fluids if dehydrated or septic
• Analgesia: do not withhold pain relief
• Antiemetics
• Broad-spectrum antibiotics covering Gram-negative and anaerobic bacteria if appendicitis likely and operation/non-operative therapy planned
• Pregnancy test before imaging/operation in women of reproductive age
• Informed consent: bleeding, infection, bowel injury, stump leak, abscess, conversion, negative appendectomy

Surgical Treatment: Appendectomy

• Standard definitive treatment
• Laparoscopic appendectomy is preferred in most patients
• Advantages of laparoscopy:

• Diagnostic view of whole abdomen/pelvis
• Less wound infection
• Less pain and faster recovery
• Useful in obese patients and women of reproductive age

• Open appendectomy:

• Used in selected cases, resource-limited settings or if laparoscopy contraindicated/unavailable
• Typical incision: McBurney/Gridiron or Lanz incision

Operative Principles

1. Explore abdomen and confirm diagnosis
2. Identify appendix at cecal taeniae convergence
3. Control mesoappendix / appendicular artery
4. Secure appendiceal base with clips, ligature or stapler
5. Remove appendix in retrieval bag if laparoscopic
6. Irrigate/suction pus if needed
7. Drain only selectively, not routine for uncomplicated cases

Antibiotic Strategy

• Preoperative antibiotics:

• Single broad-spectrum dose within 0-60 min before incision
• Reduces wound infection and intra-abdominal abscess

• Uncomplicated appendicitis after appendectomy:

• No postoperative antibiotics needed after adequate operation

• Complicated appendicitis:

• Postoperative broad-spectrum antibiotics
• Duration depends on source control and clinical response
• Usually short course, about 3-5 days after adequate source control

Non-Operative Treatment

• Can be considered in selected stable patients with uncomplicated appendicitis
• Best candidates:

• CT/US-confirmed uncomplicated appendicitis
• No appendicolith
• No perforation, abscess, phlegmon or peritonitis
• Reliable observation and follow-up possible

• Method:

• NPO initially
• IV antibiotics → switch to oral antibiotics when improved
• Serial abdominal examinations
• Repeat labs/imaging if deterioration or no improvement

• Important counseling:

• Risk of early failure
• Risk of recurrence later
• Appendicolith increases failure and perforation risk
• Hidden complicated appendicitis or tumor is possible, especially in older adults

• Not appropriate if perforation, diffuse peritonitis, sepsis, appendicolith with high risk, pregnancy or diagnostic uncertainty requiring operation

Appendiceal Abscess or Phlegmon

• Stable patient with localized abscess/phlegmon:

• IV antibiotics
• Image-guided percutaneous drainage if drainable abscess
• Careful observation

• Emergency operation if:

• Diffuse peritonitis
• Sepsis not controlled
• Failed conservative/drainage treatment
• Free perforation

• Interval appendectomy:

• Not always routine after successful non-operative abscess treatment
• Consider if recurrent symptoms, appendicolith, or malignancy concern
• Colonoscopy/CT follow-up is important in older adults to exclude cecal/appendiceal tumor

Special Cases

• Pregnancy:

• Early surgical consultation
• US first; MRI if US inconclusive and available
• Surgery preferred when appendicitis is likely; perforation is worse for mother and fetus

• Children:

• US first-line
• Appendectomy standard; antibiotics can be discussed only in selected uncomplicated cases without appendicolith
• Lower threshold for treatment because perforation can occur quickly

• Elderly:

• CT often useful because differential is broad
• Higher perforation and malignancy risk
• Consider colonoscopy after recovery if not recently performed

Exam-Focused Algorithm

1. RLQ pain + anorexia + nausea/vomiting after pain + low fever → suspect appendicitis
2. Check peritoneal signs, pregnancy test, WBC/CRP and urinalysis
3. Use US first in children/pregnancy; CT in adults when uncertain or complicated disease suspected
4. Uncomplicated appendicitis → laparoscopic appendectomy preferred; antibiotics only in selected informed patients
5. Complicated appendicitis/peritonitis → antibiotics + urgent source control
6. Abscess/phlegmon in stable patient → antibiotics +/- percutaneous drainage, then follow-up