Hernia
Inguinal, femoral, and ventral hernias plus the dangerous variants and repair decisions for the Surgery Shelf.
Source: First Aid 2026 (first-aid-usmle-bible) — no TPoT text for this chapter; FA cited by topic.
High-Yield Points
- Indirect inguinal hernia (most common overall, esp. males/infants): protrudes through the deep (internal) ring, LATERAL to the inferior epigastric vessels, follows the spermatic cord, can descend into the scrotum. Cause = patent processus vaginalis (congenital).
- Direct inguinal hernia: bulges through Hesselbach triangle, MEDIAL to the inferior epigastric vessels, from a weak transversalis fascia (acquired, older men). Rarely strangulates.
- Hesselbach triangle borders: inferior epigastric vessels (superolateral), rectus abdominis (medial), inguinal ligament (inferior).
- Femoral hernia: below the inguinal ligament, through the femoral canal medial to the femoral vein; more common in women; highest risk of incarceration/strangulation → always repair.
- Incisional (ventral) hernia: through a prior surgical incision; risk factors obesity, wound infection, poor closure. Umbilical: in adults linked to ↑intra-abdominal pressure (ascites/cirrhosis, obesity, multiparity); congenital umbilical hernias usually close by age 2.
- Hiatal hernia: sliding (type I) — GEJ slides above the diaphragm (most common, causes reflux); paraesophageal (type II) — GEJ stays put while the fundus herniates → risk of incarceration/volvulus, repair when symptomatic.
- Incarceration = irreducible; strangulation = compromised blood supply (ischemia) → pain out of proportion, fever, leukocytosis, peritonitis = surgical emergency.
- Repair: tension-free mesh (Lichtenstein) is standard for adults (lowest recurrence); use primary tissue repair / avoid mesh in a contaminated field (strangulated necrotic bowel). Watchful waiting is acceptable for minimally symptomatic, reducible inguinal hernias — but never for femoral hernias.
Key Tables / Differentials
Inguinal vs femoral hernia
| Indirect inguinal | Direct inguinal | Femoral | |
|---|---|---|---|
| Path | Deep ring, lateral to inf. epigastrics | Hesselbach, medial to inf. epigastrics | Femoral canal, below inguinal ligament |
| Cause | Patent processus vaginalis (congenital) | Weak floor (acquired) | Wide femoral canal |
| Demographics | Young males, infants | Older men | Women |
| Into scrotum? | Yes | Rarely | No |
| Strangulation risk | Moderate | Low | High → always repair |
Dangerous/less-common variants
| Hernia | Key feature |
|---|---|
| Obturator | Thin elderly woman; Howship-Romberg sign (medial thigh/knee pain); bowel obstruction |
| Spigelian | Through linea semilunaris (lateral rectus edge); risk of incarceration |
| Richter | Only the antimesenteric bowel wall strangulates → ischemia without full obstruction |
Board Pearls
- Lateral to inferior epigastrics = indirect; medial = direct (think "MD's don't lie": Medial = Direct).
- Femoral hernia in an older woman with a small bowel obstruction → repair (don't observe).
- Pain out of proportion + fever + leukocytosis in a previously reducible hernia → strangulation → emergent surgery.
- Strangulated hernia with necrotic/contaminated field → tissue repair, avoid mesh.
Classic Vignette Triggers
- "Bulge lateral to inferior epigastric vessels descending into the scrotum, young man" → indirect inguinal.
- "Reducible bulge medial to inferior epigastric vessels, older man" → direct inguinal.
- "Groin bulge below the inguinal ligament in a woman, now obstructed" → femoral hernia → repair.
- "Thin elderly woman, bowel obstruction + medial thigh pain" → obturator hernia (Howship-Romberg).
- "Bowel obstruction with strangulation but lumen still patent" → Richter hernia.
- "Chest pain, can't pass NG tube, retching without vomiting" → paraesophageal hernia with volvulus (Borchardt triad).