What is the most likely cause and recommended evaluation for a male patient with isolated right lower‑quadrant pain and normal urinalysis and complete blood count?

Right Lower Quadrant Pain in Males with Normal Labs

Most Likely Diagnosis

In a male patient with isolated right lower quadrant pain and normal urinalysis and CBC, appendicitis remains the most likely diagnosis—fever and leukocytosis are absent in approximately 50% of appendicitis cases, and clinical assessment alone misdiagnoses appendicitis in 34-68% of cases. 1, 2

Immediate Diagnostic Approach

Obtain a contrast-enhanced CT scan of the abdomen and pelvis with IV contrast (no oral contrast needed) as the definitive next step. 3, 2

Why CT is Essential

• CT demonstrates 85.7-100% sensitivity and 94.8-100% specificity for acute appendicitis, far superior to clinical assessment alone 1, 2
• CT identifies alternative diagnoses in 23-45% of patients presenting with RLQ pain, fundamentally changing management 2, 4
• Preoperative imaging reduces negative appendectomy rates from 14.7-25% down to 1.7-7.7% 2
• Both abdomen and pelvis must be scanned—scanning pelvis alone misses 7% of pathology requiring surgery located outside the typical appendiceal region 4

Critical Pitfalls to Avoid

• Never exclude appendicitis based on absence of fever—fever is absent in ~50% of confirmed appendicitis cases 1, 2
• Never rely on normal WBC count to rule out appendicitis—laboratory findings have limited diagnostic power with a positive likelihood ratio of only 2.47 2
• Never delay CT beyond 12 hours if symptoms persist or worsen—conditions like perforated appendicitis require urgent intervention 3
• Never discharge without establishing mandatory 24-hour follow-up due to measurable false-negative rates in low-risk presentations 2

Differential Diagnoses to Consider

CT will evaluate for these alternative conditions that mimic appendicitis:

• Epiploic appendagitis (inflammation of colonic fat appendages)—presents with localized RLQ tenderness at McBurney's point, normal labs, and requires only conservative treatment 5, 6
• Right colonic diverticulitis (8% of alternative diagnoses) 2
• Cecal pathology including inflammatory bowel disease 3
• Ureteral stones (despite normal urinalysis, stones may not cause hematuria) 3, 7
• Intestinal obstruction (3% of cases) 2
• Mesenteric pathology including ischemia 3

What Radiologist Should Evaluate

The CT report must specifically assess: 3, 2

• Appendix diameter (>8.2 mm is highly suggestive of appendicitis)
• Periappendiceal fat stranding and inflammatory changes
• Appendicoliths and intraluminal gas
• Right colon for diverticulitis or other pathology
• Kidneys and ureters for stones or obstruction
• Mesentery and vessels for ischemia or vascular complications
• Epiploic appendages for inflammation/torsion

Management Algorithm Based on CT Results

If CT Confirms Appendicitis (appendix >8.2 mm with periappendiceal infiltration):

• Immediate surgical consultation regardless of clinical improvement—probability of true appendicitis is >90% 2

If CT Shows Borderline Findings (appendix 7-8 mm without clear inflammation):

• Hospital observation for 24 hours with serial abdominal exams every 6-12 hours 2
• Repeat CBC to monitor leukocytosis trend 2

If CT is Negative:

• Safe discharge requires: normal CT, absence of peritoneal signs, ability to tolerate oral intake, and reliable follow-up access 2
• Mandatory 24-hour follow-up with strict return precautions 2
• Instruct patient to return immediately for fever, vomiting, worsening pain, or peritoneal signs 2

If CT Shows Alternative Diagnosis:

• Epiploic appendagitis: conservative management with NSAIDs and observation 5, 6
• Diverticulitis or other inflammatory conditions: appropriate medical or surgical management 7

Why Not Ultrasound First?

• Ultrasound is operator-dependent and often nondiagnostic in adults, particularly males with body habitus limitations 1
• Ultrasound is reserved for pediatric patients to avoid radiation, followed by CT if nondiagnostic 2
• In adult males with RLQ pain, proceeding directly to CT avoids delays and provides comprehensive evaluation 3, 2

Conservative Observation Without Imaging is Inappropriate

• Clinical determination of appendicitis is notoriously poor with negative appendectomy rates as high as 25% without imaging 2
• NSAIDs can mask evolving symptoms and delay diagnosis of progressive appendicitis 2
• Discharging based solely on normal labs risks missing early appendicitis or other serious pathology requiring intervention 2