How do you differentiate between an inguinal (in the groin area) hernia and a femoral (relating to the thigh) hernia?

Differentiating Inguinal from Femoral Hernias

The key anatomical relationship that distinguishes inguinal from femoral hernias is their position relative to the inguinal ligament - inguinal hernias occur anterior/superior to the inguinal ligament, while femoral hernias occur posterior/inferior to it.

Anatomical Landmarks and Physical Examination

Inguinal Hernia Characteristics

• Located above and medial to the pubic tubercle
• Descends through the inguinal canal following the path of the spermatic cord in males or round ligament in females
• More common in males due to the natural weakness created by the processus vaginalis during testicular descent 1
• Often extends into the scrotum in males when large
• Typically presents as a bulge that appears with increased intra-abdominal pressure (coughing, straining)

Femoral Hernia Characteristics

• Located below and lateral to the pubic tubercle
• Emerges through the femoral canal, medial to the femoral vein
• More common in females
• Rarely extends into the labium
• Often smaller and less obvious than inguinal hernias
• Associated with higher risk of incarceration and strangulation 1

Physical Examination Technique

1. Patient Positioning: Have the patient stand upright to increase intra-abdominal pressure and make hernias more apparent 1

2. Visual Inspection: Look for asymmetry or bulging in the groin area

3. Palpation Technique:

   • Place index finger over the external inguinal ring (just above and lateral to the pubic tubercle)
   • Ask patient to cough or perform Valsalva maneuver
   • Feel for a bulge or impulse against your fingertip

4. Distinguishing Features on Palpation:

   • Inguinal hernia: Palpable above the inguinal ligament and medial to femoral vessels
   • Femoral hernia: Palpable below the inguinal ligament and medial to the femoral pulse 2

5. Invagination Test (for males):

   • Gently invaginate scrotal skin with index finger
   • Follow the spermatic cord upward toward the external ring
   • An inguinal hernia will be felt as a bulge against the fingertip during coughing

Imaging Studies for Confirmation

When physical examination is inconclusive, imaging can be valuable:

Ultrasound

• First-line imaging modality due to availability, low cost, and no radiation
• Dynamic inguinal ultrasound (DIUS) has high sensitivity (97.6%) and specificity (99.8%) 3
• Technique:
  • Use high-frequency linear transducer (6-10 MHz)
  • Examine patient in supine and standing positions
  • Apply compression to assess compressibility of structures
  • Have patient perform Valsalva maneuver to provoke hernia

CT Scan

• Useful for complex or recurrent cases
• Key findings for differentiation:
  • Inguinal hernias: Hernia sac extends medial to pubic tubercle
  • Femoral hernias: Hernia sac remains lateral to pubic tubercle with compression of the femoral vein 4, 5
  • Relationship to inguinal ligament is the definitive criterion - inguinal hernias are anterior, femoral hernias are posterior 5

Common Pitfalls and Caveats

1. Small femoral hernias can be easily missed on physical examination due to their location deep to the inguinal ligament

2. Obese patients may have difficult-to-palpate hernias, requiring imaging for confirmation

3. Women have higher rates of misdiagnosis - ultrasound or MRI is often needed for accurate diagnosis 6

4. Incarcerated hernias may present with bowel obstruction symptoms rather than a visible bulge

5. Recurrent hernias after previous repair may have altered anatomy, making clinical diagnosis challenging

Summary of Key Differentiating Features

Feature	Inguinal Hernia	Femoral Hernia
Location	Above inguinal ligament	Below inguinal ligament
Relation to pubic tubercle	Medial	Lateral
Gender predominance	Males	Females
Risk of strangulation	Lower	Higher
Palpation	Felt at external ring	Felt below inguinal ligament
CT finding	Sac extends medial to pubic tubercle	Sac remains lateral with femoral vein compression

Early and accurate differentiation between these hernia types is crucial for appropriate surgical planning and to minimize the risk of complications, particularly the higher strangulation risk associated with femoral hernias 1.