What is the best course of action for evaluating and managing right-sided abdominal pain in a patient with a recent menstrual period?

Management of Right-Sided Abdominal Pain in a Patient with Recent Menstrual Period

Ultrasound (transvaginal and transabdominal) is the initial imaging study of choice for evaluating right-sided abdominal pain in a patient who recently had their menstrual period. 1, 2

Initial Diagnostic Approach

Step 1: Rule Out Pregnancy

• Perform a urine or serum β-hCG test to exclude pregnancy-related conditions, even if the patient reports recent menstruation 2

Step 2: Laboratory Testing

• Complete blood count (CBC) to assess for leukocytosis (suggesting infection or inflammation)
• Urinalysis to evaluate for urinary tract infection or hematuria
• Liver function tests and pancreatic enzymes if upper abdominal pain is present
• Consider CA-125 if ovarian pathology is suspected 2

Step 3: Imaging Based on Pain Location

For Right Upper Quadrant Pain:

• Ultrasound is the initial imaging study of choice (sensitivity 88%, specificity 80% for cholecystitis) 1
• Look for:
  • Gallstones, gallbladder wall thickening, pericholecystic fluid (cholecystitis)
  • Liver abnormalities (hepatitis, abscess)
  • Right-sided adnexal pathology that may refer pain upward

For Right Lower Quadrant Pain:

• Ultrasound (transvaginal and transabdominal) as first-line imaging 1, 2
  • Evaluate for ovarian cysts, torsion, or masses
  • Assess for appendicitis (though less sensitive than CT)
  • Look for free fluid in the pelvis
• If ultrasound is non-diagnostic and appendicitis is suspected:
  • CT abdomen and pelvis with IV contrast is recommended (sensitivity 95%, specificity 94%) 1

Special Considerations for Menstrual-Related Pain

Gynecologic Causes to Consider:

• Ovarian cysts (functional cysts may enlarge during menstruation)
• Endometriosis (can cause cyclic pain that worsens during menstruation, including bowel endometriosis) 3
• Pelvic inflammatory disease (PID) exacerbation
• Pelvic venous congestion syndrome (worsens during menstruation)

Non-Gynecologic Causes That May Correlate with Menstruation:

• Inflammatory bowel disease flares (can correlate with menstrual cycle)
• Irritable bowel syndrome (often worsens during menstruation)
• Familial Mediterranean Fever (rarely can present with attacks during menstruation) 4

Management Algorithm

1. If ultrasound shows gynecologic pathology:

   • Ovarian cyst: Conservative management if simple and <5cm
   • Complex ovarian mass: Gynecology consultation
   • Signs of ovarian torsion (enlarged ovary, minimal/absent blood flow): Immediate gynecology consultation

2. If ultrasound is non-diagnostic and symptoms persist:

   • For suspected appendicitis or diverticulitis: CT abdomen/pelvis with IV contrast 1
   • For suspected gynecologic conditions with equivocal ultrasound: MRI pelvis without and with contrast 1

3. If both ultrasound and CT are non-diagnostic:

   • Consider MRI for better soft tissue characterization, especially for suspected endometriosis 1
   • MRI with T2-weighted imaging can demonstrate edema, fluid collections, and adhesions 1

Common Pitfalls to Avoid

• Don't assume right-sided pain in a menstruating woman is always gynecologic in origin; consider appendicitis, urolithiasis, and other non-gynecologic causes
• Don't rely on conventional radiography for initial evaluation as it has limited diagnostic value for abdominal pain 1
• Don't forget to consider referred pain patterns (e.g., right shoulder pain from diaphragmatic irritation)
• Don't overlook the possibility of bowel endometriosis, which can cause cyclic abdominal pain during menstruation 3
• Don't skip pregnancy testing, even with reported recent menstruation, as bleeding can occur in early pregnancy

By following this evidence-based approach, clinicians can efficiently diagnose the cause of right-sided abdominal pain in patients who have recently had their menstrual period, leading to appropriate treatment and improved outcomes.