Hernias

Overview

A hernia is an abnormal protrusion of an organ or the fascia of an organ outside the cavity that normally contains. It occurs through a defect in the surrounding tissue structure (the hernial orifice). Protrusion of intra-abdominal contents usually occurs through congenital and acquired weakened portions of the abdominal wall. Similar weaknesses occurs in aneurysms (weak parts of vessel walls) and diverticula (weak parts of bowel). Hernias are usually aggravated or caused by anything that increases intra-abdominal pressure.

Hernias in the inguinal region include indirect, direct, and femoral (75-80%). Incisional hernias account for 8-10%, umbilical hernias 3-8% and others hernias (Spigelian, obturator, and epigastric) account for <1%

Definition of terms

Term	Definition
Hernia sac	Peritoneum or processus vaginalis covering the herniated contents
Reducible hernia	Hernia that can be pushed back into the normal position in the abdomen through th edefect. Most are benign (uncomplicated) but still need to be treated as they can progress to become incarcerated then strangulated.
Incarcerated hernia	Hernia cannot be pushed back into it’s normal position in the abdomen. Acute incarceration occurs due to swelling of the hernia contents due to reduced venous and lymphatic outflow while chronic incarceration occurs due to adhesions. At risk of strangulation.
Strangulated hernia	Tissues within the hernia become ischemic and then necrotic due to obstruction of arterial blood flow. This is a surgical EMERGENCY! Patients are usually septic presenting with fever in addition to nausea, vomiting and pain. Femoral hernias are more likely to strangulate
Obstructing hernia	Small bowel obstruction due to herniation
Inguinal hernia	Hernia whose contents enter into the inguinal canal
Indirect inguinal hernia	Congenital form of inguinal hernia where the hernia contents enter the inguinal canal through the deep inguinal ring (lateral to inferior epigastric vessels)
Direct inguinal hernia	Acquired form of inguinal hernia in which the hernia contents enter the inguinal canal through a defec tin the posterior wall (medial to inferior epigastric vessels)
Femoral hernia	Hernia whose contents enter the femoral canal through the femoral ring (below the inguinal ligament)
Obturator hernia	Hernia whose contents pass through the obturator foramen. Associated with pain along the mid-anterior thigh. More common in women than men (elderly, nulliparous woman due to laxity of surrounding ligaments). Compression of the obturator nerve can presents as Howship-Romberg sign or Hannington-Kiff sign.
Epigastric hernia	Herniation of intra-abdominal contens through the linea alba (usually multiple)
Spigelian hernia	Herniation of abdominal contents inferolateral to the navel (lateral to the rectus abdominis at the level of the arcuate line)
Pantaloon hernia	Hernia with direct and indirect components
Amyand’s hernia	Inguinal hernia containing the appendix
De Garengeot’s hernia	Incarcerated femoral hernia that contains the appendix
Littre’s hernia	Abdominal wall hernia containing a Meckel’s diverticulum
Richter’s hernia	Part of the circumference of the bowel wall has herniated, and is strangulated without obstruction

Summary of common types of hernias

	Indirect inguinal hernia	Direct inguinal hernia	Femoral hernia	Incisional hernia	Umbilical hernia
Location	Deep inguinal ring	Hasselbach’s triangle (posterior wall)	Below the inguinal ligament	Incision-site	Navel
Patient history	M > F; all ages	M> F; mostly older men	F > M; pregnnacy, history of hernia repair	Post-operative, History of wound infection	Paediatric; occasionally adults
Signs and symptoms	Groin mass +/- pain, worse with straining	Groin mass +/- pain, worse with straining	Inguinal-area mass +/- pain	Abdominal mass over incision site	Protrusion through the navel
Treatment	Herniorraphy/Hernioplasty/Herniotomy in children	Herniorrhaphy/Hernioplasty	Herniorrhaphy	Herniorrhaphy after recovery	Herniorrhaphy after age 3 or if it is symptomatic/complicated

Abdominal wall hernias in children

Hernia	Description
Congenital inguinal hernia	Indirect hernia resulting from a patent processus vaginalis. Occurs in 1% of term babies and is more common in premature boys. 60% are on the right while 10% are bilateral. Surgical repair is indicated as soon as it is diagnosed due to risk of incarceration
Infantile umbilical hernia	Symmetrical bulge at the umbilicus. More common in premature babies. Majority resolve without intervention before age of 2 years. Rarely complicates.

• Risk factors for hernias
  • Factors that increase intra-abdominal pressure
    • Straining
    • Coughing
    • Lifting (strenuous exercise and manual labor)
    • Pregnancy
    • Ascites
    • Obesity
    • Chronic obstructive pulmonary disease, asthma or chronic bronchitis (chronic cough)
    • Constipation
  • Factors that cause abdominal weakness
    • Smoking (impairs collagen synthesis)
    • Uncontrolled diabetes mellitus (impairs collagen synthesis)
    • Abdominal wall injury (including surgical incisions)
    • Connective tissue diseases and collagen disorders (congenital weakness of the abdominal wall)
    • Patent processus vaginalis
  • Demographic factors
    • Male sex (27% lifetime risk of developing hernias)
    • Older age (due to tissue weakness)
    • Family history
• Physial examination
  • Reducibility
  • Cough impulse
  • Tenderness
  • Overlying skin changes
  • Multiple defects or the contralateral side
  • Signs of previous repair
  • Scrotal content for inguinal hernia
  • Other associated pathologies
• Investigations
  • Ultrasound: best initial test to identify occult hernia due to the ability to demonstrate the hernia in real time while the patient performs valsava. 86% sensitivity and 77% specificity.
  • CT-scan: less sensitive and specific for identifying occult hernias that ultrasound. Can differentiate the types of hernia. Particularly useful in complex incisional hernia to determine the number and size of the muscle defects, content, and presence or absence of adhesions or intra-abdominal pathology
  • MRI: high sensitivity and specificity imaging for identifying occult hernias and differentiating the types of groin hernias.
  • Herniography (peritoneography): invasive test performed under fluoroscopy. Contrast is injected into the peritoneal cavity and the images are taken whyle the patient performs valsava. Most sensitive and specific test for occult hernias.
  • Plain radigraph: may demonstrate a hiatus or

Mesh in Hernia Repair

Mesh refers to prosthetic material used to strengthen hernia repair. They can be synthetic or bilogical. Mesh can be used to bridge a defect, plug a defect or augment repair.

Types of mesh based on gross structure

Structure	Mesh
Net mesh	Woven or knitted mesh (porous) that allow fibrous tissue to grow in between the strands. These become adherent and integrated into host tissues within a few months. They may be fixed using glue, sutures, or staples (which may be absorbable)
Sheet mesh	Non-porous mesh that does nt allow host tissue to grow but becomes encapsulated by fibrous tissue. Requires strong non-absorbable suture to prevent mesh migration.

Types of mesh based on material

Material	Description
Polypropylene	A strong monfilament net with hydrphobic properties that prevents bacterial in-growth
Polyester	A braided filament mess with hydrophilic that allows rapid vascular and cellular infiltration hence providing a strong host-tissue interface
Polytetrafluorethane (PTFE)	Flat sheets that do not allow tissue in-growth. Used as a non-adhesive barrier between tissue layers. This is suitable for intraperitoneal use (along with polycellulose and collagen mesh)
Polyglycolic acid	Absorbable mesh used in temporary abdominal wall closure and to buttress sutured repairs. They have no role in hernia repair.