What is the most likely diagnosis for a patient with chronic constipation, abdominal distension, vomiting, and a tender non-reducible swelling in the right groin, with X-ray findings of a distended small bowel and multiple fluid levels?

Femoral Hernia with Incarceration

The most likely diagnosis is A. Femoral hernia, based on the classic anatomical location (below and lateral to the pubic tubercle), presentation with small bowel obstruction, and the tender non-reducible nature of the swelling.

Anatomical Localization

The key distinguishing feature is the location of the groin swelling relative to the pubic tubercle 1:

• Femoral hernias emerge below and lateral to the pubic tubercle, passing through the femoral canal medial to the femoral vessels 2
• Inguinal hernias (both direct and indirect) appear above and medial to the pubic tubercle 1
• The patient's swelling is specifically described as "below and lateral to pubic tubercle," which is pathognomonic for femoral hernia 2

Clinical Presentation Consistent with Femoral Hernia

This patient demonstrates the classic triad of femoral hernia complications 2:

• Small bowel obstruction (distended abdomen, vomiting, X-ray showing distended small bowel with air-fluid levels) 1
• Incarceration/strangulation (tender, non-reducible mass) 2, 3
• Higher risk demographics (femoral hernias are more common in women and have the highest propensity for strangulation among groin hernias, accounting for 2-4% of all groin hernias) 2

Why Other Options Are Incorrect

Direct inguinal hernia (Option B): Would present above and medial to the pubic tubercle, not below and lateral 1. Direct hernias protrude through Hesselbach's triangle and emerge through the superficial inguinal ring 1.

Indirect inguinal hernia (Option D): Also appears above and medial to the pubic tubercle, following the inguinal canal and potentially descending into the scrotum in males 1. The anatomical location described excludes this diagnosis 2.

Metastatic lymph node (Option C): Would not cause the acute mechanical small bowel obstruction pattern seen on X-ray (distended loops with multiple air-fluid levels) 1. Lymph nodes do not typically become "non-reducible" in the same manner as hernias, and would not produce the tympanic quality on percussion associated with gas-filled bowel 1.

Clinical Significance and Management Implications

Femoral hernias carry the highest mortality of all abdominal wall hernias due to their propensity for strangulation 2, 4:

• The narrow, rigid femoral ring predisposes to incarceration and subsequent bowel ischemia 2
• Emergency surgical intervention is required when signs of strangulation are present (tenderness, non-reducibility, bowel obstruction) 1, 2
• CT imaging with IV contrast should be obtained urgently to assess for bowel ischemia, though the clinical presentation already mandates surgical exploration 1, 3

Ultrasound findings that would support this diagnosis include aperistaltic non-reducible bowel loops, free fluid in the hernia sac, and lack of color Doppler flow in entrapped bowel 3.

The chronic constipation history is a red herring—while it may have contributed to straining and hernia development, the acute presentation with mechanical obstruction and the specific anatomical location definitively point to femoral hernia 1, 2.