Hernias

High-yield ABSITE review organized by hernia type. Anatomy first, then inguinal, femoral, umbilical, ventral/incisional, and the eponymous zebras you’ll see on oral boards.

Basic Principles

• Underlying principle of a good hernia repair: tension-free.
• Most common cause of a recurrent hernia: wound infection.
• Rank as a cause of SBO: 2nd to adhesions (worldwide: adhesions still #1 in developed settings; hernias are #1 in the developing world because elective repairs are less common).

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Abdominal Wall Anatomy

Layers just off midline (anterior to posterior): skin → subcutaneous fat (Camper’s) → Scarpa’s fascia → anterior rectus sheath → rectus muscle → posterior rectus sheath → preperitoneal fat → peritoneum.

Layers lateral to the rectus: skin → subcutaneous fat (Camper’s) → Scarpa’s fascia → external oblique → internal oblique → transversus abdominis → transversalis fascia → preperitoneal fat → peritoneum.

• Arcuate line: where the posterior rectus sheath ends, approximately one-third of the way from umbilicus to pubic symphysis. Below the arcuate line, all aponeurotic layers pass anterior to the rectus.
• Blood supply to the rectus: superior and inferior epigastric arteries.
• Inguinal ligament: extension of the external oblique aponeurosis.
• Cremaster muscle: extension of internal oblique muscle fibers.

Hesselbach’s Triangle

• Medial: lateral edge of the rectus sheath.
• Inferior: inguinal ligament.
• Lateral: inferior epigastric vessels.
• A hernia in Hesselbach’s triangle is a direct inguinal hernia.

Embryology at the Umbilicus

• Omphalomesenteric (vitelline) duct → Meckel’s diverticulum.
• Urachus → median umbilical ligament.
• Obliterated umbilical arteries → medial umbilical ligaments.
• Obliterated umbilical vein → ligamentum teres (round ligament of the liver).
• Midgut: herniates at 6 weeks, returns at 10 weeks.
• Omphalocele: defect through the umbilical stalk, sac covered.
• Gastroschisis: defect inferior/right of the umbilicus, no sac.

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Inguinal Hernias

Direct vs Indirect

• Indirect: lateral to inferior epigastrics; congenital (patent processus vaginalis).
• Direct: medial to inferior epigastrics (through Hesselbach’s); acquired (weakness in the inguinal floor).
• Risk factors for direct hernia: obesity, smoking, ascites, poor nutrition, any chronically elevated intra-abdominal pressure.

Spermatic Cord Contents

Cremasteric muscle fibers, testicular artery, vas deferens, pampiniform venous plexus, ilioinguinal nerve, and the genital branch of the genitofemoral nerve.

Key Nerves in Open Repair

• Ilioinguinal — most commonly injured, usually when opening the external oblique aponeurosis.
• Iliohypogastric.
• Genital branch of the genitofemoral.

Key Nerve in Laparoscopic Repair

• Lateral femoral cutaneous nerve — injured by a tack placed too laterally (lateral to the iliopubic tract, into the “triangle of pain”).

Open Repair Options

• Bassini: conjoint tendon (transversalis + internal oblique) sutured to the inguinal ligament.
• Shouldice: same reconstruction as Bassini but in 4 layers; lowest recurrence of the pure tissue repairs.
• Lichtenstein: mesh sewn between the conjoint/transversalis and the inguinal ligament — the classic modern open tension-free repair.
• Plug and patch: mesh plug in the internal ring followed by an overlying Lichtenstein patch.
• McVay (Cooper’s): conjoint tendon sutured to Cooper’s ligament; the open repair for a femoral hernia (also usable for inguinal if mesh is contraindicated).

Laparoscopic Repair

• TEP (totally extraperitoneal) and TAPP (transabdominal preperitoneal).
• A posterior mesh covers the internal ring, Hesselbach’s triangle, and the femoral space in a single patch.
• Main fixation structure: Cooper’s ligament.

Critical Laparoscopic Triangles

• Triangle of Doom: contains the iliac vessels; medial, apex at the iliopubic tract, bounded by the vas deferens medially and the spermatic vessels laterally. Do not tack here.
• Triangle of Pain: contains nerves (lateral femoral cutaneous, femoral branch of genitofemoral, femoral nerve); lateral to the spermatic vessels, below the iliopubic tract. Do not tack here.

Pediatric Repair

• High ligation of the sac at the internal ring. No mesh, no floor repair.

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Femoral Hernias

• Highest risk: women and the elderly.
• Defect: below the inguinal ligament, medial to the femoral vein, within the femoral canal.
• Open repair: McVay — open the inguinal floor and close the femoral space by suturing the conjoint tendon to Cooper’s ligament.
• High risk of incarceration/strangulation — lower threshold to repair when found.

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Umbilical Hernias

• Most are congenital; typical contents are preperitoneal fat.
• Pediatric: wait until age 5 to see if it closes spontaneously; repair before starting school if still open.
• Adult primary repair (no mesh) appropriate for defects < 1 cm; otherwise mesh.
• Cirrhotic + massive ascites + symptomatic umbilical hernia: control the ascites first (medical management or TIPS) before elective repair — operating through uncontrolled ascites has a very high morbidity.

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Ventral / Incisional Hernias

Risk Factors

Wound infection, obesity, COPD, smoking, steroid use, diabetes. Stop smoking before elective repair — strongest modifiable risk factor for recurrence.

Mesh Placement

• Underlay (retrorectus / preperitoneal): lowest recurrence; preferred.
• Onlay: on top of the fascia.
• Inlay: bridging the defect — highest recurrence, avoid when possible.
• Mesh choice: macroporous synthetic for clean cases; biologic mesh if the field is contaminated (CDC class III/IV) or if bowel resection is needed for an incarcerated hernia.

Component Separation

When primary fascial closure can’t be achieved:

• Anterior component separation: incise the external oblique aponeurosis.
• Transversus abdominis release (TAR): incise the transversus abdominis.
• Posterior component separation: incise the posterior rectus sheath.

Fascial Closure Technique

• Small bites (5 mm × 5 mm) with a slowly-absorbing monofilament, suture-length–to–wound-length ratio ≥ 4:1. This is the STITCH result (see related paper). Small bites roughly halve the 1-year incisional hernia rate versus 1 cm × 1 cm bites.

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Eponymous / Special Hernias (Quick Hits)

• Spigelian: at the junction of the semilunar line and arcuate line; an intramuscular (interparietal) hernia, often missed on exam.
• Amyand: appendix inside an inguinal hernia sac. Primary repair (no mesh) if appendicitis is present.
• Littre: Meckel’s diverticulum inside a hernia sac.
• Pantaloon: coexisting direct and indirect hernias straddling the inferior epigastric vessels.
• Sliding: a retroperitoneal structure (bladder, cecum, sigmoid) forms part of the sac wall. Do not open the sac — reduce en bloc.
• Richter’s: only part of the antimesenteric bowel wall is in the sac. Can strangulate without obstruction — classic oral-board answer.
• Obturator: groin pain and medial thigh pain with internal rotation of the hip (Howship–Romberg sign). Seen in thin, elderly women. Often presents as SBO.

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Rapid-Fire Questions

• Q: Direct vs indirect hernia — how do you tell?
  A: Relative to the inferior epigastric vessels. Lateral = indirect (through the internal ring). Medial = direct (through Hesselbach’s floor).

• Q: What sits in Hesselbach’s triangle?
  A: Rectus medially, inguinal ligament inferiorly, inferior epigastrics laterally. A hernia there is a direct.

• Q: Contents of the spermatic cord?
  A: “Three arteries, three nerves, three other things” — testicular/cremasteric/artery of the vas; ilioinguinal, genital branch of genitofemoral, sympathetic; vas deferens, pampiniform plexus, lymphatics.

• Q: What’s in the Triangle of Doom?
  A: The external iliac vessels. Do not tack there during laparoscopic repair.

• Q: What’s in the Triangle of Pain?
  A: Lateral femoral cutaneous nerve, femoral branch of the genitofemoral, femoral nerve. Tacks here cause chronic groin/thigh pain.

• Q: Most commonly injured nerve in open inguinal hernia repair?
  A: Ilioinguinal, when opening the external oblique aponeurosis.

• Q: Most commonly injured nerve in laparoscopic inguinal hernia repair?
  A: Lateral femoral cutaneous nerve.

• Q: You’ve done a McVay and get brisk arterial bleeding at Cooper’s — source?
  A: Corona mortis, an anastomotic branch between the obturator and external iliac (or inferior epigastric) arteries.

• Q: Intraoperative femoral vein injury while placing a suture in the floor — what do you do?
  A: Pull the suture, hold pressure. Convert or call vascular if it doesn’t stop.

• Q: 2-year-old with a 1 cm umbilical hernia — repair now?
  A: No. Observe until age 5. Repair before school if it hasn’t closed.

• Q: Cirrhotic with tense ascites and an umbilical hernia — fix it?
  A: Control the ascites first (diuresis, consider TIPS), then repair. Operating through uncontrolled ascites is high-morbidity.

• Q: Incarcerated hernia, you do a bowel resection, now what mesh?
  A: Biologic mesh or pure tissue repair — avoid permanent synthetic in a contaminated field.

• Q: Where does mesh go, and which placement has the worst recurrence?
  A: Underlay > onlay > inlay for recurrence prevention. Inlay = highest recurrence, avoid.

• Q: Optimal fascial closure technique for a midline laparotomy?
  A: Continuous single-layer closure with slowly-absorbing monofilament, 5 mm × 5 mm small bites, suture length–to–wound length ratio ≥ 4:1 (STITCH trial).

• Q: One month out from an open inguinal mesh repair, wound infection with purulent drainage around the mesh — what do you do?
  A: Explant the mesh. You can’t salvage infected prolene.

• Q: Old woman, thin, with SBO and medial thigh pain worsened by hip internal rotation?
  A: Obturator hernia. Howship–Romberg sign.

• Q: Doing an open inguinal hernia repair, skeletonized the cord, can’t find a hernia?
  A: Open the floor and look for a femoral hernia.

• Q: Part of the bowel wall is in the sac and it’s strangulated, but the patient has no obstruction — what is it?
  A: Richter’s hernia.

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Quick-Reference Cards

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Related Landmark Papers

• STITCH — small-bites vs large-bites fascial closure for elective midline laparotomy. 13% vs 21% 1-year incisional hernia rate.

Related Case Prep

• Exploratory Laparotomy — midline opening and closure technique.

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References

1. Fischer’s Mastery of Surgery, 7th ed. — Abdominal Wall Hernias chapters.
2. Muysoms FE, et al. European Hernia Society guidelines on the closure of abdominal wall incisions. Hernia. 2015.
3. Deerenberg EB, et al. STITCH trial. Lancet. 2015.
4. Fitzgibbons RJ, Forse RA. Groin Hernias in Adults. NEJM. 2015.