Inguinal Hernia

Published on 06/08/2015 by admin

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Last modified 06/08/2015

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 CT: Arises  anteromedial to origin of inferior epigastric artery and extends through anterior abdominal wall lateral to rectus muscle 

– Contents of inguinal canal (testicular vessels, vas deferens) can be seen as a crescent of density along lateral aspect of hernia as it protrudes
– No compression of femoral artery/vein
• Indirect inguinal hernia: Hernia passes through internal inguinal ring, down inguinal canal, and emerges at external ring

image CT: Arises superolateral  to inferior epigastric vessels and extends lateral to medial within inguinal canal
image Lateral crescent sign not present with indirect hernias
• Ultrasound: Can scan patient either with Valsalva maneuver or in upright position to precipitate hernia

image US can determine reducibility of hernia (unlike CT) and identify reducible hernias that may not be seen on CT

PATHOLOGY

• 75-80% of all hernias occur in inguinal region, with indirect hernias 5x more common than direct
• Indirect inguinal hernia usually a congenital defect due to patency of processus vaginalis, while direct hernias are acquired due to abdominal wall weakness

CLINICAL ISSUES

• Much more common in men than women
• Symptoms often worse when standing, lifting, or straining
• Complications: Incarceration and strangulation (much more common with indirect than direct inguinal hernia)
• Emergent surgical repair (laparoscopic or open) in patients with a strangulated inguinal hernia
• Symptomatic hernias usually surgically repaired on elective basis, although conservative management possible in some asymptomatic or minimally symptomatic patients
• Conservative management possible in patients who are asymptomatic or have minimal symptoms
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(Left) Illustration demonstrates a direct inguinal hernia image, with the hernia neck image located medial to the inferior epigastric artery and vein image.

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(Right) Illustration demonstrates an indirect inguinal hernia image, with the hernia neck image located lateral to the inferior epigastric artery and vein image. The inferior epigastric vessels serve as the key landmark in distinguishing direct and indirect inguinal hernias.
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(Left) Axial CECT in an elderly man who presented with groin pain and a palpable mass demonstrates a right inguinal hernia. Note that the hernia sac is in the right inguinal canal image and medial to the inferior epigastric vessels image, identifying it as a direct inguinal hernia.

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(Right) Axial CECT in an elderly man who presented with a large groin mass and a small bowel obstruction demonstrates a large right inguinal hernia containing sections of the small bowel image, colon image, and omentum image.

TERMINOLOGY

Abbreviations

• Inguinal hernia (IH)

Synonyms

• Pelvic hernia, groin hernia

Definitions

• Inguinal hernia: External hernia with orifice in inguinal location
• External hernia: Abnormal protrusion of intraabdominal tissue through defect in abdominal/pelvic wall, with extension outside abdominal cavity

IMAGING

General Features

• Location

image Indirect IH: Hernia passes through internal inguinal ring, down inguinal canal, and emerges at external ring

– Lateral IH: Arise superior and lateral to epigastric vessels (lateral umbilical fold)
– Can extend along spermatic cord into scrotum (i.e., complete hernia) in males
– Can follow course of round ligament of uterus into labium majus in females
– Juxtafunicular hernia: Indirect hernia that passes outside spermatic cord into surrounding soft tissues
– Occur most often on right in both men and women
image Direct IH: Hernia passes through Hesselbach triangle (in floor of inguinal canal bounded by inguinal ligament, lateral margin of rectus abdominis, and inferior epigastric artery)

– Arise medial to course of inferior epigastric vessels (IEV)
– Not contained in spermatic cord and generally does not pass into scrotum
– Medial umbilical fold divides Hesselbach triangle into medial and lateral parts, and direct IH can be divided into medial and lateral types
• Morphology

image Indirect IH within spermatic cord has smooth contour with an elongated oblique course

– Juxtafunicular hernia has more irregular contour without protrusion into preformed sac
– Dissect through subcutaneous fat and fibrous tissue
image Direct IH appears broad and dome-shaped

CT Findings

• Some IH, particularly when small, have tendency to reduce when patient is supine and may be missed on CT
• Primary landmark is inferior epigastric artery, which arises opposite to origin of deep circumflex iliac artery from external iliac artery
• Direct hernia: Arises  anteromedial to origin of inferior epigastric artery, extends through anterior abdominal wall lateral to rectus muscle, and courses below inferior epigastric artery

image Contents of inguinal canal (testicular vessels, vas deferens) can be seen as a crescent of density along lateral aspect of hernia as it protrudes
image No compression of nearby femoral artery and vein (unlike femoral hernias)
image Relationship of hernia sac relative to pubic tubercle may help differentiate inguinal and femoral hernias

– IH seen anterior to horizontal plane connecting pubic tubercles (femoral hernias posterior)
• Indirect hernia: Arises superolateral  to inferior epigastric vessels and extends lateral to medial within inguinal canal

image Lateral crescent sign seen with direct hernias not present with indirect hernias, as normal contents of inguinal canal are not compressed
• Direct and indirect hernias can very rarely be visualized in same groin: “Saddlebag” or “pantaloon” hernia (combined-type hernia)
• CT very helpful for identifying contents of hernia sac (omental fat, bowel, bladder) and identifying complications (bowel obstruction, ischemia, perforation, etc.)

image IH described as “sliding” hernias when partially retroperitoneal structures (bladder, distal ureters, ascending/descending colon) are within hernia sac

– Key to identify, as blood vessels supplying herniated segments may be injured during surgical repair or trauma
image Appendix within hernia sac: Amyand hernia
image Meckel diverticulum within hernia sac: Littre hernia
image Also helpful if other disease process mimicking or precipitating hernia suspected
image CT should be first-line modality in patients presenting with acute symptoms from hernia

Ultrasonographic Findings

• Some debate in literature regarding efficacy of US in diagnosing hernias: Various studies have shown sensitivities ranging from 29-100%

image Most useful if patient presents nonurgently with history suggesting reducible IH
• Typically high-frequency transducer (> 10 MHz) best, since IH are superficial, but lower frequencies may be utilized in more obese patients

image Ultrasound probe placed longitudinal to inguinal canal and anterior to inferior epigastric artery (at site of origin from external iliac artery)
• Patient initially scanned supine, but advantage of US is ability to scan patient either with Valsalva maneuver or in upright position to precipitate hernia (if hernia not seen at rest in supine position)

image Bowel loops may peristalse within hernia sac and may aid in identification of hernia
image US can determine reducibility of hernia (unlike CT) and identify reducible hernias that may not be seen on CT due to supine scan position
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