# Acute Appendicitis: Diagnosis and Management

## Overview

Acute appendicitis is the most common surgical emergency worldwide, with a lifetime risk of approximately 7 to 8%. Timely diagnosis and appropriate management -- whether operative or, increasingly, non-operative -- are fundamental competencies for the general surgery resident. The clinical spectrum ranges from uncomplicated appendicitis to perforation with abscess or diffuse peritonitis, and the approach to each differs substantially.

## Epidemiology and Pathophysiology

Appendicitis has a peak incidence between 10 and 30 years of age with a slight male predominance. The pathogenesis begins with luminal obstruction, most commonly by a fecalith or appendicolith, though lymphoid hyperplasia, tumor, and parasites are other causes. Obstruction leads to a predictable cascade: increased intraluminal pressure, venous congestion and arterial compromise, bacterial translocation and transmural inflammation, and ultimately gangrene and perforation, which typically occurs within 24 to 72 hours of symptom onset. The perforation rate at presentation is approximately 20 to 30% and is higher at the extremes of age. The bacteriology is polymicrobial, with *E. coli*, *Bacteroides fragilis*, *Peptostreptococcus*, and *Pseudomonas* being the most commonly implicated organisms.

## Clinical Presentation

### Classic Presentation

The classic presentation follows a well-recognized sequence. **Periumbilical pain** migrates to the **right lower quadrant** (McBurney point) over 12 to 24 hours as visceral inflammation becomes parietal. Anorexia is the most consistent early symptom, present in over 90% of cases. Nausea and vomiting typically follow pain onset -- importantly, if vomiting precedes the pain, an alternative diagnosis should be considered. Low-grade fever is common, and a temperature exceeding 38.3 degrees Celsius suggests perforation or another complication.

### Physical Examination Signs

Several examination findings support the diagnosis. **McBurney point tenderness** is elicited one-third of the distance from the anterior superior iliac spine to the umbilicus. The **Rovsing sign** -- right lower quadrant pain elicited by palpation of the left lower quadrant -- indicates referred peritoneal irritation. The **psoas sign** (pain with passive right hip extension) suggests a retrocecal appendix, while the **obturator sign** (pain with internal rotation of the flexed right hip) suggests a pelvic appendix. The **Dunphy sign** -- increased abdominal pain with coughing -- is a sensitive indicator of peritoneal irritation. Progression from localized guarding to rigidity suggests perforation and peritonitis.

### Atypical Presentations

Atypical presentations are common and must be recognized. The **retrocecal appendix**, found in 65% of cases, may present with flank or back pain and less prominent anterior peritoneal signs. A **pelvic appendix** may cause suprapubic pain, urinary frequency, diarrhea, or tenesmus. In **pregnancy**, the appendix is displaced cephalad and laterally, peritoneal signs may be muted, and appendicitis remains the most common non-obstetric surgical emergency. **Elderly** patients frequently present with blunted symptoms and delayed presentation, resulting in perforation rates of 50 to 70%. **Pediatric** patients, particularly those under 5 years, have difficulty localizing pain and higher perforation rates.

## Diagnostic Workup

### Laboratory Studies

The white blood cell count is elevated above 10,000 in 80 to 85% of cases, though a left shift is more reliable than the absolute count. C-reactive protein is typically elevated, and the combination of WBC and CRP improves diagnostic sensitivity; a CRP above 10 mg/L supports the diagnosis. Urinalysis may show sterile pyuria or microscopic hematuria when the appendix lies adjacent to the ureter or bladder and helps rule out urinary tract infection. A beta-hCG is mandatory in all reproductive-age females.

### Clinical Scoring Systems

The **Alvarado Score (MANTRELS)** assigns points as follows:

| Parameter | Points |
|-----------|--------|
| **M**igration of pain to RLQ | 1 |
| **A**norexia | 1 |
| **N**ausea/vomiting | 1 |
| **T**enderness in RLQ | 2 |
| **R**ebound tenderness | 1 |
| **E**levated temperature | 1 |
| **L**eukocytosis (>10,000) | 2 |
| **S**hift to left (>75% neutrophils) | 1 |
| **Total** | **10** |

Score interpretation: 7–10 = high probability (operate); 5–6 = equivocal (observe/image); ≤4 = low probability (discharge with follow-up). The **Appendicitis Inflammatory Response (AIR) Score** incorporates CRP levels and polymorphonuclear percentage and demonstrates better discrimination than the Alvarado score in some validation studies.

### Imaging

**CT abdomen/pelvis with IV contrast** is the gold standard in adults, with sensitivity of 94 to 98% and specificity of 95 to 98%. Diagnostic findings include a dilated appendix (greater than 6 mm), wall enhancement, periappendiceal fat stranding, appendicolith, abscess, and free fluid. Routine CT imaging has significantly reduced the negative appendectomy rate from 15 to 25% to below 5%. **Ultrasound** is the first-line study in children and pregnant patients, with sensitivity of 86% and specificity of 81%. The hallmark finding is a non-compressible, aperistaltic, tubular structure greater than 6 mm in diameter with a target sign on cross-section. Ultrasound is operator-dependent and limited by body habitus and retrocecal appendix position. **MRI** is increasingly used in pregnancy when ultrasound is inconclusive, offering sensitivity of 96 to 100% and specificity of 97 to 99% without ionizing radiation.

## Management

### Uncomplicated Acute Appendicitis

#### Appendectomy (Standard of Care)

**Laparoscopic appendectomy** is the preferred approach in most patients, offering reduced wound infections, less postoperative pain, faster recovery, and the ability to examine the entire abdomen. The technique typically uses three ports. The mesoappendix is divided with an energy device, clips, or stapler. The appendix base is secured with endoloops or a stapler, with both methods being acceptable; the stapler is particularly useful for a wide or inflamed base. **Open appendectomy** is performed through a McBurney (muscle-splitting) or Rocky-Davis (transverse) incision and remains appropriate when laparoscopy is unavailable or as a conversion. The base is ligated with an absorbable suture, and the stump may be inverted, though inversion has no proven benefit. Regarding **timing**, appendectomy should be performed within 24 hours of diagnosis, but there is no significant benefit to middle-of-the-night surgery compared to a next-morning operation for uncomplicated cases.

#### Antibiotics-First (Non-Operative) Strategy

The **CODA trial** (2020) demonstrated that antibiotics were non-inferior to surgery for uncomplicated appendicitis at 30 days, but 29% of patients crossed over to appendectomy by 90 days. The **APPAC trials** reported a 27% recurrence at 1 year and 39% at 5 years with the antibiotics-first approach. Patient selection is critical: only CT-confirmed uncomplicated cases without appendicolith, abscess, or perforation should be considered. The presence of an appendicolith is associated with a substantially higher failure rate (41% versus 14%). This strategy is appropriate when a patient values avoiding surgery and accepts the risk of recurrence, and shared decision-making is essential.

### Complicated Appendicitis

**Perforated appendicitis with diffuse peritonitis** requires urgent appendectomy (laparoscopic or open) with broad-spectrum antibiotics covering gram-negatives and anaerobes, along with peritoneal lavage and drainage as needed.

**Appendiceal abscess or phlegmon** is initially managed non-operatively with IV antibiotics and percutaneous drainage if the abscess exceeds 3 to 4 cm, with a success rate of 80 to 90%. **Interval appendectomy** has traditionally been recommended 6 to 8 weeks later to prevent recurrence (10 to 20% risk) and to exclude underlying neoplasm, especially in patients over 40 years where the risk of neoplasm found at interval appendectomy ranges from 10 to 29%. Some argue that interval appendectomy is unnecessary if symptoms resolve and colonoscopy with imaging excludes neoplasm.

### Perioperative Antibiotics

A single preoperative dose of a second-generation cephalosporin (cefoxitin) or cefazolin plus metronidazole is standard. For uncomplicated appendicitis, no postoperative antibiotics are needed. For complicated cases (perforated or gangrenous), IV antibiotics are continued for 3 to 5 days, guided by clinical improvement including resolution of fever, normalization of white blood cell count, and return of bowel function.

## Special Considerations

### Appendicitis in Pregnancy

Appendicitis complicates approximately 1 in 500 to 1,500 pregnancies. Perforation increases the fetal loss rate from 1.5% to 6%, underscoring the importance of timely diagnosis. Imaging should begin with ultrasound, followed by MRI if inconclusive. Laparoscopic appendectomy is safe in all trimesters per SAGES guidelines. The patient should be positioned in the left lateral decubitus position to avoid caval compression, and an open entry technique is preferred for establishing pneumoperitoneum.

### Incidental Findings at Appendectomy

When a **normal appendix** is found at surgery, it should still be removed to eliminate future diagnostic confusion. The surgeon should inspect the terminal ileum for Meckel diverticulum, Crohn disease, and mesenteric lymphadenitis. **Appendiceal neuroendocrine tumors (carcinoid)** are managed based on size: tumors less than 1 cm are cured by appendectomy alone; tumors 1 to 2 cm usually require only appendectomy, with right hemicolectomy reserved for mesoappendiceal invasion, positive margins, or high-grade histology; tumors greater than 2 cm require right hemicolectomy. **Appendiceal mucinous neoplasms** must be handled carefully to avoid rupture, which can cause pseudomyxoma peritonei, and require formal oncologic workup.

### Stump Appendicitis

Stump appendicitis -- inflammation of a residual appendiceal stump after incomplete appendectomy -- is rare but increasingly recognized. It should be considered in any patient with recurrent right lower quadrant pain after prior appendectomy and is treated by completion appendectomy.

<image>Anatomical illustration showing the various positions of the appendix relative to the cecum: retrocecal (65%), pelvic (31%), subcecal (2%), preileal (1%), and postileal (0.5%). Include McBurney point marked at one-third the distance from the right anterior superior iliac spine to the umbilicus, with surface anatomy landmarks labeled.</image>

<image>CT scan illustration showing diagnostic findings of acute appendicitis: a dilated appendix greater than 6mm in diameter with wall thickening and enhancement, surrounding periappendiceal fat stranding, and an appendicolith within the lumen. Adjacent panels showing normal appendix for comparison and complicated appendicitis with periappendiceal abscess formation.</image>

<image>Surgical illustration of laparoscopic appendectomy technique showing the three-port setup, identification and division of the mesoappendix with an energy device, and securing the base of the appendix with endoloops. Include a detail panel showing the critical step of identifying the appendiceal-cecal junction and the window created in the mesoappendix.</image>

## Clinical Pearls

Anorexia is the most consistent early symptom of appendicitis; if the patient is hungry, the diagnosis should be reconsidered. Pain that begins before vomiting is the classic sequence in appendicitis; vomiting before pain onset suggests gastroenteritis. The presence of an appendicolith on CT is associated with higher rates of perforation and failure of non-operative management. In the elderly, a normal WBC does not exclude appendicitis, and perforation rates exceed 50% in patients over 60 due to delayed presentation. A "normal" appendix found at surgery should still be removed to prevent future diagnostic confusion, and the surgeon should always inspect the terminal ileum and pelvis. The negative appendectomy rate should be below 5% in the era of routine CT imaging. Patients over 40 years with complicated appendicitis should have a follow-up colonoscopy to exclude cecal malignancy, even if interval appendectomy is not planned. Stump appendicitis, although rare, should be considered in patients with recurrent right lower quadrant pain after prior appendectomy.

## References

- CODA Collaborative. A randomized trial comparing antibiotics with appendectomy for appendicitis. *N Engl J Med*. 2020;383:1907-1919.
- Salminen P, Paajanen H, Rautio T, et al. Antibiotic therapy vs appendectomy for treatment of uncomplicated acute appendicitis: the APPAC randomized clinical trial. *JAMA*. 2015;313(23):2340-2348.
- Di Saverio S, Podda M, De Simone B, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. *World J Emerg Surg*. 2020;15:27.
- Bhangu A, Soreide K, Di Saverio S, et al. Acute appendicitis: modern understanding of pathogenesis, diagnosis, and management. *Lancet*. 2015;386(10000):1278-1287.