Abdominal Wall Hernia

KEY FACTS

Clinical Issues

• Tissue protruding though defect in abdominal wall

Most abdominal wall hernias are point specific
• Midline hernias

Epigastric: Usually small

Umbilical: In children

Paraumbilical: In adults

Hypogastric: Rare
• Lateral hernias

Spigelian: Defect in transversus abdominis fascia alongside lateral border of rectus abdominis muscle (linea semilunaris) and lateral border of rectus sheath

Lumbar: Occur in 2 areas of potential weakness in flank

Superior lumbar triangle (Grynfeltt hernia) with erector spinae medially, 12th rib superiorly, and internal oblique muscle laterally

Inferior lumbar triangle (Petit hernia) with latissimus dorsi muscle medially, iliac crest inferiorly, and external oblique muscle laterally

Diagnostic Checklist

• For all abdominal wall masses, exclude presence of hernia
• If hernia confirmed, determine nature of herniated content (extraperitoneal fat, omentum, bowel) and site and size of abdominal wall defect

Routinely use Valsalva maneuver ± examination in standing position if symptoms exacerbated by standing

– Can perform Valsalva by asking patient to blow against back of hand
• Observe for reducibility and consider whether bowel, if present, is obstructed or strangulated

Such complications are uncommon in noninguinal abdominal wall hernias

– Since these hernias have either wide neck or, if neck is narrow, rarely contain bowel

TERMINOLOGY

Definitions

• Hernia: Abnormal protrusion of organ or part of organ out of cavity in which it is normally contained

Reducible: Hernia that can disappear either spontaneously or with external pressure

Obstructed: Hernia leading to mechanical bowel obstruction

Strangulated: Hernia causing mechanical constriction of vascular supply to contents of hernia

Incarcerated: Hernia that cannot be reduced
• Types of abdominal wall hernia: Midline (epigastric, umbilical, hypogastric), lateral (spigelian, lumbar), and incisional

IMAGING

General Features

• Best diagnostic clue

Abdominal wall lump due to tissue protruding though defect in abdominal wall
• Location

Midline hernias

– Epigastric: Between xiphisternum and umbilicus

– Umbilical: Umbilical or immediate paraumbilical region

– Hypogastric: Between umbilicus and pubic symphysis

Lateral hernias

– Spigelian

Defect along linea semilunaris in transversus abdominis aponeurosis just lateral to rectus sheath

Most commonly located near arcuate line

– Lumbar: Occur in 2 potentially weak areas of flank

Superior lumbar triangle (Grynfeltt hernia) bounded by erector spinae medially, 12th rib superiorly, and internal oblique muscle laterally

Inferior lumbar triangle (Petit hernia) bounded by latissimus dorsi muscle medially, iliac crest inferiorly, and external oblique muscle laterally

Incisional hernia: Located at surgical incisional site
• Morphology

Abdominal wall; anatomy

– Layers: Skin, subcutaneous fat, musculofascial layer, transversalis fascia, and extraperitoneal fat

– Musculofascial layer

Anterior wall: Paired rectus muscles enclosed by rectus sheath (aponeurosis of internal oblique, external oblique, and transversus abdominis muscles), which laterally forms linea semilunaris and centrally fuses to form linea alba

Anterolateral-lateral wall: External oblique, internal oblique, and transversus abdominis

Posterior wall: Quadratus lumborum and erector spinae muscles

– Arcuate line: Lower margin of posterior rectus sheath ends at arcuate line, midway between umbilicus and pubic symphysis

– Distal to arcuate line, rectus muscle is separated from peritoneum only by transversalis fascia, as aponeuroses of internal oblique, external oblique, and transversus abdominis pass anterior to rectus muscle

Epigastric hernia

– Usually small and contains extraperitoneal fat that protrudes through linea alba (fatty hernia of linea alba)

– May occasionally be large and contains bowel

Umbilical hernia

– Umbilical in children

Peritoneal content protrudes through patent umbilical ring

– Paraumbilical in adults

Extraperitoneal fat ± peritoneal contents protrudes at side of umbilical ring

Hypogastric hernia

– Very uncommon

Spigelian hernia

– Defect in transversus abdominis fascia between lateral border of rectus abdominis muscle (linea semilunaris) and lateral border of rectus sheath

This section of transversalis fascia is known as spigelian fascia

– Tends to occur within 6 inches above imaginary line connecting both anterior superior iliac spines

– Usually extends into subcutaneous tissue, though may pass between transversus abdominis and internal or external oblique fascia or may extend into rectus muscle

Can present as flank lump if extends laterally

Lumbar hernia

– Usually painless due to wide hernial neck

Incisional hernia

– Occurs in 0.5-14.0% of postoperative patients

– May occur years after surgery, though usually occurs within 1st year

– May go unnoticed by patient and be incidentally detected on imaging

Can be very large

CT Findings

• Accurate at assessing presence of hernia, site, and size of abdominal wall defect and identifying sac contents

Useful for assessing larger deep-seated hernias