Acute appendicitis

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Core Mechanism: Acute appendicitis is a progressive inflammatory illness driven by luminal obstruction of the appendix, a blind-ending structure arising from the cecum.
• The Cellular Breakdown: Obstruction (most commonly by a fecalith or localized lymphoid hyperplasia) leads to isolated appendiceal luminal distention. As intraluminal pressure exceeds venous perfusion pressure, the appendiceal wall suffers vascular congestion and ischemia.
• The Fatal Cascade: Ischemia promotes bacterial overgrowth and transmural inflammation. If left untreated, the structurally compromised wall undergoes gangrenous necrosis and eventual perforation, spilling intestinal contents and leading to localized or diffuse peritonitis. Perforation rates are exceedingly high (up to 70% within 48 hours) in children under 3 to 4 years old due to their inability to articulate early symptoms.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Stabilization: Keep the patient strictly nil per os (NPO) immediately upon suspicion of the diagnosis to avoid delaying operative intervention.
• Resuscitation: Establish IV access and administer isotonic fluids (0.9% Normal Saline or Lactated Ringer's) to maintain hydration and correct volume depletion.
• Analgesia and Antiemetics: Administer prompt parenteral opiate analgesia, such as Morphine 0.1 mg/kg IV (or typically 2-5 mg in adults), and an antiemetic like slow IV metoclopramide 10 mg.
• Targeted Antibiotic Therapy: Initiate broad-spectrum IV antibiotics covering aerobic and anaerobic gram-negative organisms upon diagnosis or if signs of peritonitis are present.
• First-line options: Piperacillin/tazobactam 4.5 g IV (Pediatric: 100 mg/kg), Ampicillin/sulbactam 3 g IV (Pediatric: 75 mg/kg), or Cefoxitin 2 g IV.
• Penicillin-allergic alternative: Metronidazole 500 mg IV plus Ciprofloxacin 400 mg IV.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• "Can't-Miss" Mimics:
• Gynecologic/Obstetric: Ruptured ectopic pregnancy, ovarian torsion, and pelvic inflammatory disease (PID).
• Genitourinary: Testicular torsion (31% of cases present as abdominal pain without localized testicular pain), nephrolithiasis, and severe pyelonephritis.
• Gastrointestinal: Intussusception (in children), gastroenteritis, and mesenteric ischemia.
• Prioritized Diagnostic Workup:
• Urinalysis & Pregnancy Test: Mandatory for all females of childbearing age to rule out ectopic pregnancy. Note that UA may be abnormal (sterile pyuria) simply due to periureteral inflammation from the appendix.
• Laboratory Panel: CBC with differential and CRP. While a mild leukocytosis (WBC >10,000/mm³) is characteristic, no single WBC count or CRP level can definitively confirm or exclude the diagnosis.
• Imaging Stratification:
• Pediatrics, Pregnant Women, and Young Nonobese Adults: Graded compression ultrasound (US) is the mandatory first-line modality.
• Nonpregnant Adults: CT abdomen and pelvis with IV contrast is the gold standard.
• Indeterminate Pregnant Patients: Proceed to non-contrast MRI to avoid ionizing radiation.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Point-of-Care Ultrasound (POCUS):
• Scan the right lower quadrant (RLQ) looking for a tubular, blind-ended, noncompressible structure arising from the cecum.
• A positive scan reveals an outer-wall to outer-wall diameter dilatation (typically >6 mm). Look for surrounding free fluid, an obstructing echogenic fecalith with posterior acoustic shadowing, and an echogenic inflammatory reaction (fat stranding) surrounding the appendix.
• CT Abdomen/Pelvis:
• Look for an enlarged appendix, periappendiceal fat stranding, appendicoliths, and evaluate for complications such as localized abscess formation, free fluid, or gross perforation.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• The Alvarado Score: A validated 10-point clinical decision rule for acute appendicitis.
• Symptoms: Migration of pain (1), Anorexia/urinary acetone (1), Nausea/vomiting (1).
• Signs: RLQ tenderness (2), Rebound pain (1), Temperature $\ge$ 37.7°C (1).
• Labs: Leukocytosis $\ge$ 10,000/$\mu$L (2), PMN $\ge$ 75% (1).
• Clinical Disposition by Score:
• Score 1–4 (Low Risk): ~30% probability. Consider alternative diagnoses and safely discharge with close follow-up.
• Score 5–7 (Moderate Risk): ~66% probability. Requires imaging (US/CT), serial examinations, or hospital admission/observation.
• Score 8–10 (High Risk): 87-93% probability. Strongly consider prompt surgical consultation for appendectomy.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Deadly Cognitive Trap (Withholding Analgesia): Refusing to give opioids out of fear that it will "mask" the abdominal exam. Critical Action: Early administration of IV opioids is safe, strongly recommended, and actually improves the reliability of the physical exam and sonography without masking peritonitis.
• Deadly Cognitive Trap (Dismissing via Urinalysis): Anchoring on a diagnosis of a UTI because of white or red blood cells in the urine. Correction: An inflamed appendix resting on the ureter or bladder can cause secondary urinary abnormalities.
• Critical Action (Pediatric & Elderly Presentations): Recognizing that appendicitis presents atypically at the extremes of age. Two-thirds of appendicitis malpractice cases stem from diagnostic delays, particularly when concomitant constipation masks the classic presentation.

7. MCQ MASTERCLASS (Written Exam Tips)

• Classic Buzzwords: "Periumbilical pain migrating to the RLQ" and "Pain preceding vomiting." (If vomiting precedes the pain, lean toward gastroenteritis).
• Anatomical Distractor: The tip of the inflamed appendix is retrocecal in 74% of cases and pelvic in 21%. Exam questions frequently use this to trick candidates by presenting a patient with right upper quadrant (RUQ) pain (especially during the third trimester of pregnancy as the uterus displaces the appendix upward) or isolated flank/pelvic pain.
• Imaging Distractor: A hemodynamically unstable patient with an acute surgical abdomen is presented. The distractor is "Order an emergent CT scan." Correction: Unstable patients with rigid abdomens bypass the scanner; they require resuscitation and immediate exploratory laparotomy.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Initial Assessment Hook: "Given the patient's classic presentation of migratory right lower quadrant pain and anorexia, I am highly concerned for acute appendicitis, while remaining vigilant to rule out genitourinary or gynecological mimics like ectopic pregnancy."
• The Resuscitation & Diagnostic Command: "I will immediately place the patient NPO and establish IV access. I am ordering 0.1 mg/kg of IV Morphine to control their pain, which will not mask peritonitis and will facilitate a better exam. I will send a CBC, CRP, Urinalysis, and a stat urine pregnancy test. Because this is a young, nonobese patient (or pediatric/pregnant), I am ordering a graded compression RLQ ultrasound as my initial imaging."
• The Definitive Disposition: "With imaging confirming an inflamed appendix >6 mm, I am initiating broad-spectrum IV antibiotics with Piperacillin-Tazobactam. I am consulting General Surgery immediately for operative management via appendectomy."