How should I evaluate and manage an adult with right lower quadrant pain, fever, anorexia, nausea/vomiting, and neutrophilic leukocytosis suggestive of appendicitis?

Approach to Suspected Appendicitis in Adults

Obtain contrast-enhanced CT of the abdomen and pelvis with IV contrast immediately as the definitive diagnostic test for any adult presenting with right lower quadrant pain, fever, anorexia, nausea/vomiting, and leukocytosis suggestive of appendicitis. 1, 2

Initial Clinical Assessment

Key Clinical Features to Document:

• Pain migration pattern: Classic appendicitis begins with periumbilical or epigastric pain that migrates to the right lower quadrant within 12-24 hours 1, 3
• Associated symptoms: Anorexia, nausea, and vomiting are present in approximately 90% of cases when combined with RLQ pain 3, 4
• Fever presence: Fever is absent in approximately 50% of appendicitis cases, so its absence does NOT exclude the diagnosis 1, 5
• Peritoneal signs: Check for rebound tenderness, guarding, and rigidity in the RLQ 1
• Psoas sign: Test for pain with hip extension or flexion, which suggests retroperitoneal irritation from a retrocecal appendix 3

Critical Pitfall: Clinical assessment alone misdiagnoses appendicitis in 34-68% of cases, with negative appendectomy rates of 14.7-25% when relying on examination without imaging 1. Even with classic presentation, imaging is essential because typical features are only present in ~50% of cases 1.

Diagnostic Imaging Algorithm

Primary Imaging Recommendation:

• CT abdomen/pelvis with IV contrast (without oral contrast) achieves 85.7-100% sensitivity and 94.8-100% specificity for appendicitis 1, 2, 3
• CT without enteral contrast allows rapid acquisition without delays from oral contrast administration 1
• CT identifies alternative diagnoses in 23-45% of patients with RLQ pain, fundamentally changing management 1, 2

Alternative Ultrasound-First Approach (institutional preference):

• Point-of-care ultrasound or graded compression ultrasound may be performed first 2
• If ultrasound is nondiagnosive, equivocal, or limited by body habitus, proceed immediately to CT 1, 2
• Combined ultrasound-then-CT strategy achieves 99% sensitivity and 91% specificity 1
• Limitation: Ultrasound has significantly reduced accuracy in obese patients (false diagnosis rate 46.2% in obese females vs 38.5% in non-obese) 2

For reproductive-age women: Consider transvaginal ultrasound before CT to evaluate gynecologic causes (ovarian torsion, ectopic pregnancy, ovarian cyst, PID), which account for 21.6% of alternative diagnoses 1

Laboratory Testing

• Complete blood count: Leukocytosis with left shift supports but does not confirm appendicitis; normal WBC reduces probability (negative likelihood ratio 0.25) but does not exclude it 1, 5
• C-reactive protein: Significantly elevated in appendicitis; normal inflammatory markers (WBC + CRP) have 100% negative predictive value 3

Important caveat: 15.6% of confirmed appendicitis cases present with isolated RLQ pain without fever or elevated inflammatory markers 5. Do not discharge based on normal labs alone.

CT Interpretation and Risk Stratification

High-Risk CT Findings (proceed directly to surgery):

• Appendiceal diameter ≥8.2 mm with periappendiceal fat stranding 1
• Appendicolith present 1, 4
• Appendiceal diameter >13 mm 4
• Mass effect or abscess formation 4

These findings predict >90% probability of true appendicitis and 40% failure rate with antibiotics-first approach 1, 4.

Borderline Findings (7-8 mm diameter without periappendiceal changes):

• Consider 24-hour hospital observation with serial abdominal exams every 6-12 hours 1
• Repeat CBC to monitor leukocytosis trend 1
• Proceed to surgery if symptoms progress or peritoneal signs develop 1

Management Based on CT Results

CT Confirms Appendicitis:

• Immediate surgical consultation for appendectomy (laparoscopic preferred) 1, 3, 4
• Initiate broad-spectrum antibiotics: piperacillin-tazobactam monotherapy OR cephalosporin/fluoroquinolone + metronidazole 4
• If perforated with abscess: consider percutaneous drainage followed by interval appendectomy 1, 3

CT Negative but High Clinical Suspicion Persists:

• Proceed to diagnostic laparoscopy, which provides both diagnostic confirmation and therapeutic intervention 1, 2, 3

CT Identifies Alternative Diagnosis:

• Common findings include right colonic diverticulitis (8%), ureteral stones, intestinal obstruction (3%), gynecologic pathology (21.6%), and other GI conditions (46%) 1
• Manage according to specific diagnosis identified 1

Supportive Care During Evaluation

• IV fluid resuscitation for dehydration from vomiting 3
• Antiemetics: metoclopramide, prochlorperazine, or ondansetron 3
• Mild analgesia: Avoid opioids initially as they may mask evolving symptoms 1
• NPO status while awaiting imaging and surgical evaluation 1

Discharge Criteria and Follow-Up

Safe discharge requires ALL of the following:

• Normal CT scan without evidence of appendicitis 1
• Absence of peritoneal signs on exam 1
• Ability to tolerate oral intake 1
• Reliable access to 24-hour follow-up 1

Mandatory return precautions: Instruct patients to return immediately for worsening pain, fever development, persistent vomiting, or increasing abdominal tenderness 1. False-negative rates exist even in low-risk presentations, necessitating close follow-up 1.