Inguinal Hernia

Published on 06/08/2015 by admin

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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
image
(Left) Illustration demonstrates a direct inguinal hernia image, with the hernia neck image located medial to the inferior epigastric artery and vein image.

image
(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.
image
(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.

image
(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
• Primary sonographic landmarks are pubic tubercle and inferior epigastric artery (identified along lateral border of rectus abdominis and can be traced back to external iliac artery)
• Indirect IH: Hernia seen to originate  lateral  to inferior epigastric artery and extend medially towards pubic tubercle

image Valsalva maneuver: Impaired swelling of pampiniform plexus
• Direct IH: Hernia seen to originate medial to inferior epigastric artery and extend anteriorly toward probe

image Valsalva maneuver: In direct IH, distended pampiniform plexus is displaced by hernia sac

Radiographic Findings

• Radiography

image Soft tissue density or gas-containing mass overlying obturator foramen on affected side suggests presence of hernia
image Presence of dilated bowel loops with convergence of distended intestinal loops toward inguinal region suggests bowel obstruction due to inguinal hernia
image Barium examination of small or large bowel: Tapered narrowing or obstruction of intestinal segments entering hernia orifice
image Attempt to reduce hernia manually under fluoroscopy
image Visualize afferent and efferent loops of protruding intestine

MR Findings

• Dynamic evaluation in multiple imaging planes may have advantages

Imaging Recommendations

• Best imaging tool

image CECT in patients with acute symptoms or suspicion of complications related to hernia
image US is appropriate first-line modality in patients with nonurgent presentation
• Protocol advice

image  

DIFFERENTIAL DIAGNOSIS

Femoral Hernia

• Protrusion of abdominal contents through femoral ring and into femoral canal
• Omental fat or bowel herniating into femoral canal medial to femoral vein and inferior to inferior epigastric vessels
• Femoral vein often indented/compressed by hernia sac
• Hernia sac located posterior to horizontal plane of pubic tubercle, while IH located anterior
• More common in women

Lymphadenopathy

• Soft tissue nodule near inguinal ligament might mimic IH clinically, but distinction easily made with imaging
• CT, US help differentiate hernia contents from other groin and scrotal masses

image Hydrocele, varix, lipoma of spermatic cord, undescended testicle, abscess, tumor

Iatrogenic Hematoma

• Arterial puncture following arteriography, needle biopsy, aspiration

image Hematoma may extend into rectus muscle, lateral abdominal wall muscles
image Blood can track directly from groin along transversalis fascia and transversus abdominis muscle
image CT, US, MR: Appearance of blood; extent of lesion changes over time
image Pseudoaneurysm: Perivascular, rounded mass; neck and track connecting with injured artery

Spermatic Cord Lipoma or Liposarcoma

• Rare fat-containing masses that typically grow into scrotum, but can involve inguinal canal and mimic an IH containing omental fat
• Well-differentiated liposarcomas or lipomas may be difficult to differentiate from omental fat in hernia, but lesions usually appear more mass-like and liposarcomas often demonstrate some internal complexity

PATHOLOGY

General Features

• Etiology

image 75-80% of all hernias occur in inguinal region, with indirect hernias 5x more common than direct
image Indirect IH considered most often congenital defect due to patency of processus vaginalis and weakness of crus lateralis at lateral aspect of inguinal canal

– Although congenital, may not become clinically apparent until later in life
image Direct IH considered acquired lesion arising due to weakness in transversalis fascia of posterior wall of inguinal canal in Hesselbach triangle

Gross Pathologic & Surgical Features

• Contents include small bowel loops, mobile colon segments (sigmoid, cecum, appendix)
• Sliding IH: Partially retroperitoneal organs

image Urinary bladder, distal ureters, ascending/descending colon included in herniation
image Retroperitoneal structures constitute sac wall
image Blood vessels supply herniated segments, may be injured during surgical repair or trauma
• Littre hernia: Meckel diverticulum in hernia sac
• Richter hernia: Portion of bowel circumference in sac (antimesenteric)
• Incomplete IH: Sac not extended through external inguinal ring
• Diverticular direct IH: Protrudes from medial inguinal or supravesical fossa

image Small opening in otherwise normal transverse fascia
image Distinct circumscribed neck, protrudes anteriorly more than inferiorly
• Potential indirect IH associated with undescended testis or testis in inguinal canal

image Testicular or spermatic cord hydrocele

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Wide spectrum of presentations depending on hernia size

– May be asymptomatic in many (especially when small), present as palpable lump in groin, heavy sensation in groin, or cause groin pain

image Symptoms often ↑ when standing, lifting, or straining
– Incarcerated or strangulated hernias may have severe fulminant presentations
image Most hernias diagnosed on clinical examination (without imaging), with hernia best palpated with patient standing, coughing, or performing Valsalva maneuver
• Physical exam: Recumbent and upright position; may be reducible; audible bowel sounds; ± tenderness

image Indirect hernia lightly touches tip of finger

– Examining finger placed along spermatic cord at scrotum, passed into external ring along canal
– During maneuvers that increase intraabdominal pressure
image Direct IH causes forward bulge low in canal
• Incarcerated or strangulated IH: Bowel distension; painful, often tense swelling in groin or scrotum
• Diagnosis by history and physical examination

Demographics

• Age

image Indirect IH may occur from infancy to old age, but generally present by 5th decade

– Occurs in 1-3% of all children with 1.5-2x greater incidence in premature infants
– Pediatric IH almost always indirect with increased incarceration risk

image Usually right (60-75%) but often bilateral (10-15%)
image Direct IH increases in incidence with age
• Gender

image Indirect IH 5-10x more common in men
image Direct IH occurs mostly in men
• Epidemiology

image ∼ 5% of men who develop IH require surgery
image Bilateral patent processus vaginalis occurs in up to 10% of patients with indirect IH

Natural History & Prognosis

• Complications: Incarceration, strangulation, and bowel obstruction

image Direct IH rarely incarcerated and has a lower association with strangulation
image Indirect IH accounts for 15% of intestinal obstructions
image Diverticulitis, appendicitis, or primary/metastatic tumor may occur within hernia sac
• IH may recur after herniorrhaphy in ∼ 20%

image Direct IH may develop after indirect IH repair
image Diverticular hernias: Form of recurrence
• Multiple hernias: 1 usually direct

image May obscure smaller clinically significant hernias
• Saddlebag, pantaloon, combined IH: Simultaneous occurrence of direct and indirect IH in same groin

image Separation of 2 adjacent hernia sacs by IEV creates bilocular appearance

Treatment

• Emergent surgical repair (laparoscopic or open) in patients with a strangulated IH
• Symptomatic hernias surgically repaired on elective basis
• Conservative management possible in patients who are asymptomatic or have minimal symptoms

DIAGNOSTIC CHECKLIST

Consider

• Indirect IH protrude from lateral inguinal fossa
• Direct IH are from medial and supravesical fossae

image
(Left) Coronal CECT demonstrates multiple dilated loops of small bowel image in the pelvis, compatible with small bowel obstruction.
image
(Right) Coronal CECT in the same patient demonstrates that the small bowel extends into a right inguinal hernia image with a transition point in the hernia sac. This incarcerated hernia could not be manually reduced, and urgent surgery was performed for repair.
image
(Left) Grayscale ultrasound of an inguinal hernia shows small bowel loops image in the right scrotal sac image. Note the contralateral left scrotum and testis image.

image
(Right) Coronal T2 MR demonstrates a “sliding” inguinal hernia containing a portion of the bladder image. Sliding inguinal hernias contain portions of partially retroperitoneal structures, such as the bladder, and care must be taken at surgery to avoid damage to these structures or their supplying vessels.
image
(Left) Barium small bowel follow-through study in a patient with a right inguinal hernia shows the herniated small bowel image lying over the right femoral head. Note the constriction of the bowel image as it passes through the inguinal ring.

image
(Right) Grayscale ultrasound shows echogenic omentum image herniating into the inguinal canal. Note the fluid image within hernia sac and inferiorly displaced ipsilateral testis image. Omental fat on US is echogenic or slightly hypoechoic tissue without peristalsis.
image
Axial CECT shows a hernia sac image lying anterior to the right femoral vessels. A contrast-opacified small bowel is present within the hernia, but no sign of bowel obstruction is seen.

image
Axial CECT shows an inguinal hernia causing small bowel obstruction. Note the entrapped and thickened small bowel in the right inguinal hernia sac image.
image
Axial CECT at a higher level in the same patient demonstrates a dilated small bowel image from obstruction.
image
Axial CECT of a right inguinal hernia image contains herniated fat. The fat is somewhat “dirty” or infiltrated in appearance, suggesting incarceration or ischemia of herniated fat.
image
Axial CECT at a higher level in the same patient demonstrates abdominal wall defect image.
image
CECT shows an incarcerated small bowel with perforation within the inguinal hernia sac. Note the thickened small bowel within the large hernia sac image.
image
Axial CECT shows a dilated small bowel entering the inguinal canal and the leaving collapsed bowel image.
image
Axial CECT shows a “knuckle” of fluid-filled small intestine strangulated within the right inguinal hernia image.
image
Axial CECT shows a left inguinal hernia containing only fat and spermatic cord.
image
Small bowel follow through shows a large portion of the small intestine within the scrotum due to a right inguinal hernia.
image
Axial CECT shows a left inguinal hernia at the upper end of the inguinal canal. There is a mass effect due to the herniated fat and bowel.
image
Axial CECT shows a left inguinal hernia containing a sigmoid colon. Also note the right thigh hematoma.
image
Axial CECT shows a right inguinal hernia with the colon in the upper scrotum.
image
Axial CECT in an elderly woman shows a left inguinal hernia, right obturator hernia image, and pessary image.
image
Coronal CECT demonstrates a large right inguinal hernia image in a patient who reported a long history of a growing bulge in the groin. The hernia contains multiple small bowel loops, portions of the colon, and small ascites image.
image
Axial CECT in an elderly man who presented with sepsis and a large right scrotal mass demonstrates a large scrotal abscess image from perforated incarcerated bowel within an inguinal hernia.
image
Axial CECT in the same patient illustrates a collection of bowel image and omental fat image within the hernia sac.

SELECTED REFERENCES

1. Burkhardt, JH, et al. Diagnosis of inguinal region hernias with axial CT: the lateral crescent sign and other key findings. Radiographics. 2011; 31(2):E1–12.

2. Lassandro, F, et al. Abdominal hernias: Radiological features. World J Gastrointest Endosc. 2011; 3(6):110–117.

3. Light, D, et al. The role of ultrasound scan in the diagnosis of occult inguinal hernias. Int J Surg. 2011; 9(2):169–172.

 

Narci, A, et al. O. Preoperative sonography of nonreducible inguinal masses in girls. J Clin Ultrasound. 2008; 36(7):409–412.

Cherian, PT, et al. Radiologic anatomy of the inguinofemoral region: insights from MDCT. AJR Am J Roentgenol. 2007; 189(4):W177–W183.

Suzuki, S, et al. Differentiation of femoral versus inguinal hernia: CT findings. AJR Am J Roentgenol. 2007; 189(2):W78–W83.

Robinson, P, et al. Inguinofemoral hernia: accuracy of sonography in patients with indeterminate clinical features. AJR Am J Roentgenol. 2006; 187(5):1168–1178.

Alam, A, et al. The accuracy of ultrasound in the diagnosis of clinically occult groin hernias in adults. Eur Radiol. 2005; 15(12):2457–2461.

van den Berg, JC. Inguinal hernias: MRI and ultrasound. Semin Ultrasound CT MR. 2002; 23(2):156–173.

Shadbolt, CL, et al. Imaging of groin masses: inguinal anatomy and pathologic conditions revisited. Radiographics. 2001; 21(Spec No):S261–S271.

Zhang, GQ, et al. Groin hernias in adults: value of color Doppler sonography in their classification. J Clin Ultrasound. 2001; 29(8):429–434.

Toms, AP, et al. Illustrated review of new imaging techniques in the diagnosis of abdominal wall hernias. Br J Surg. 1999; 86(10):1243–1249.

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