Diagnostic Ultrasound - Abdomen and Pelvis

Abdominal Wall Hernia
TERMINOLOGY
Definitions
• Hernia: Weakness or defect in fibromuscular wall with
protrusion of an organ/part of an organ through defect
○ Reducible: Recedes spontaneously or with external
pressure (manual or transducer)
○ Incarcerated: Nonreducible
○ Strangulated: Compromised vascular supply of hernia
contents
• Classification: Midline versus lateral hernias
IMAGING
General Features
• Best diagnostic clue
○ Abdominal wall lump due to tissue protruding though a
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 in transversus abdominis aponeurosis just
lateral to rectus sheath (linea semilunaris)
□ 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
○ Epigastric hernia
– Usually small and contains extraperitoneal fat that
protrudes through linea alba (fatty hernia of linea
alba)
– May occasionally be large and contain bowel
○ Umbilical hernia
– Umbilical in children
□ Peritoneal content protrudes through patent
umbilical ring
– Paraumbilical or periumbilical in adults
□ Extraperitoneal fat ± peritoneal contents protrude
through 1 side of umbilical ring
○ Hypogastric hernia
– Very uncommon
○ Spigelian hernia
– Usually extends into subcutaneous layer, though may
pass between transversus abdominis and internal
oblique muscles, or may extend into rectus sheath
□ Can present as flank lump if extends laterally
– Sometimes secondary to trauma
– More prone to strangulation
○ Lumbar hernia
– Usually painless due to wide hernial neck
– Secondary to trauma or surgery
○ Incisional hernia
– Occurs in 10-30% of postoperative patients
– May occur years after surgery, though usually within
1st year
– May go unnoticed by patient and be incidentally
detected on imaging
□ Can be very large
Ultrasonographic Findings
• Grayscale ultrasound
○ High resolution linear transducer; reserve curvilinear
lower frequency for large hernias/overview
– Extended field of view (panoramic) for larger hernias,
diastasis recti
○ Identify relevant muscles and fascial planes
○ Show content of hernia (omentum, bowel, properitoneal
fat, fluid), site/size of abdominal wall defect and
complications
– Omental fat: Echogenic/hypoechoic tissue without
peristalsis
– Bowel: "Target" echo pattern with central echoes due
to air in lumen and visible peristalsis
□ May see valvulae conniventes (small bowel) or
feculent content (large bowel)
□ Variable appearances due to air-fluid content
○ Use of maneuvers such as Valsalva or standing position
to improve detection of hernias
– Document with cine clips
○ Check for reducibility by applying pressure
○ Complications: Irreducible hernia may become
obstructed or strangulated
– Uncommon in noninguinal abdominal wall hernias
– Obstructed hernia: Absence of bowel peristalsis,
narrow neck, dilated bowel, fluid
– Strangulated hernia: Absence of color Doppler flow
within bowel wall or mesentery, swollen bowel wall,
aperistalsis, fluid, echogenic fat
□ Note that absence of color flow is a late sign and
nonstrangulated fat containing hernias do not
show flow
– Other signs are also unreliable, making it difficult to
assess strangulation on ultrasound
CT Findings
• Accurate at assessing presence of hernia and identifying sac
contents as well as site and size of abdominal wall defect
○ Useful for assessing larger deep-seated hernias and
complications
• Hernias may be less evident in supine position but CT can
be performed during Valsalva
MR Findings
• Similar to CT but can use dynamic sequences during
Valsalva
Imaging Recommendations
• Best imaging tool
○ Ultrasound first-line imaging for smaller hernias or
children
– Uniquely dynamic, real-time examination; repeatable,
widely available, inexpensive
Diagnoses: Abdominal Wall/Peritoneal Cavity
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