Differential Diagnosis for Right Lower Quadrant Pain in a 46-Year-Old Male
In a 46-year-old male with RLQ pain, appendicitis is the primary concern but represents only approximately 50% of cases—the differential must systematically include gastrointestinal, genitourinary, vascular, and other abdominal pathologies that can present identically. 1, 2
Primary Diagnostic Considerations
Gastrointestinal Causes
Appendicitis remains the most common surgical emergency causing RLQ pain, though it accounts for only about half of cases in adults presenting with this complaint 1, 2. The classic presentation of periumbilical pain migrating to the RLQ with anorexia, nausea, vomiting, fever, and leukocytosis occurs in only 50% of patients 1.
Right-sided colonic diverticulitis is a critical alternative diagnosis that can be clinically indistinguishable from appendicitis and is detected on CT in a significant proportion of patients with RLQ pain 2.
Inflammatory bowel disease (Crohn's disease) affecting the terminal ileum can present with RLQ pain, particularly in this age group 2, 3.
Infectious ileocolitis including conditions like Yersinia enterocolitica, Campylobacter, or other bacterial/viral gastroenteritis can localize to the RLQ 2, 3.
Cecal diverticulitis is less common than left-sided diverticulitis but must be considered in the differential 4.
Bowel obstruction, particularly small bowel obstruction, can present with RLQ pain when the transition point is in this region 2, 5.
Epiploic appendagitis is an underrecognized cause of focal RLQ pain that mimics appendicitis but is self-limited 4.
Omental infarction can present with acute RLQ pain and is often mistaken for appendicitis 4.
Cecal or right colon malignancy should be considered in this age group, particularly if there are associated symptoms like weight loss or change in bowel habits 2, 4.
Genitourinary Causes
Nephrolithiasis with a right ureteral stone can cause referred pain to the RLQ and is a common alternative diagnosis 2.
Pyelonephritis or complicated urinary tract infection can present with RLQ pain, particularly if the right kidney is involved 3.
Testicular torsion (if pain radiates to the groin) must be considered as a surgical emergency 3.
Vascular Causes
Mesenteric ischemia or early mesenteric venous thrombosis can present with RLQ pain, particularly in patients with risk factors for thrombosis 3, 4.
Other Causes
Psoas abscess can present with RLQ pain and may be associated with fever 3, 4.
Rectus sheath hematoma should be considered, particularly in patients on anticoagulation 4.
Hernia (inguinal or femoral) with incarceration can cause RLQ pain 3.
Diagnostic Approach
CT abdomen and pelvis with IV contrast is the gold standard initial imaging study for evaluating RLQ pain in adults, achieving 95% sensitivity and 94% specificity for appendicitis while identifying alternative diagnoses in approximately 50% of cases. 1, 2 This approach has reduced negative appendectomy rates from 16.7% with clinical evaluation alone to 8.7% with preoperative CT 2.
Key Diagnostic Steps
Obtain beta-hCG in all women of reproductive age before imaging to exclude pregnancy and guide imaging choices, though this is not applicable to your male patient 2.
Document specific pain characteristics including onset, migration pattern (periumbilical to RLQ suggests appendicitis), associated symptoms (anorexia, nausea, vomiting, fever), and presence of peritoneal signs (rebound tenderness, guarding) 1, 2.
Perform urinalysis to rule out urinary tract infection or nephrolithiasis as alternative causes 6.
Order CT with IV contrast without waiting for oral contrast, as IV contrast alone provides equivalent diagnostic accuracy and avoids treatment delays that could increase perforation risk 2.
Ensure full abdomen and pelvis coverage on CT, as limiting imaging to the pelvis alone misses 7% of surgical pathology located in the abdomen 2.
Critical Pitfalls to Avoid
Do not assume appendicitis is the only diagnosis—approximately 50% of patients with RLQ pain have alternative diagnoses requiring different management, and 41% of patients with non-appendiceal diagnoses require hospitalization with 22% needing surgical or image-guided intervention 2.
Do not delay imaging for oral contrast administration in suspected appendicitis, as this increases time to diagnosis without improving accuracy 2.
Do not rely on clinical scoring systems alone (such as the Alvarado score), as these have shown mixed results and do not improve diagnostic accuracy sufficiently to replace imaging 1.
Do not order plain radiography routinely, as it has minimal diagnostic value in evaluating RLQ pain 2.