A Tour of the Abdominal Wall: an Assessment of Hernias by Multidetector Computed Tomography

Home , Lumbar triangle, Obturator hernia, Spigelian hernia

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A Tour of the Abdominal Wall: An Assessment of Hernias by Multidetector Computed Tomography

G. Matzke, G. Espil, J.P. Dos Ramos Alferes, N. Larrañaga, A. Oyarzún and S. Kozima

Imaging Department, Hospital General de Agudos Dr. Cosme Argerich, Ciudad Autónoma de Buenos Aires,Argentina

Abstract Even if the diagnosis of abdominal wall hernias is clinical, and the most appropriate test is ultrasound, in a large number of cases hernias are difficult to evaluate, or their presence is notsuspected because of the patient’s biotype, the absence of symptoms, the presence ofcomplications, or the appearance of rare hernias. Additionally, abdominal wall weakness resulting from surgery leads to eventration of sometimes unusual organssuch as the liver, bladder, or appendix. The use ofmultidetector computed tomography (MDCT) is of great advantage when it is difficult to establish a diagnosis by other methods. Hernia may also be an incidental finding that should be considered for potential future complications. In this paper, we describe the main MDCT findings in abdominal wall hernias, including umbilical,epigastric, hypogastric, inguinal, Spigelian, lumbar, obturator, intercostal, and incisional hernias,as well as their content.

Keywords: Abdominal wall; Hernia; Multidetector computed tomography

Introduction tients with abdominal wall scarring)3. Abdominal wall hernias are the protrusion of the abdominal Abdominal wall hernias that may be found from the cephalic contents through an area of anatomic weakness, while an to the caudal area include: epigastric, ventral, Spigelian, lum- eventration is a subcutaneous protrusion of the intraabdomi- bar, inguinal, femoral and obturator hernias. Incisional her- nal contents through a weakened area of the abdominal or nias, in turn, may be located at any site, as they do not follow lumbar wall resulting from a previous surgical procedure, a a cephalocaudal direction. Their accurate classification may 4 gap secondary toblunt trauma or to congenital malforma- be established by anatomic repairs . tion (referred to as incisional hernia in the English-speaking The aim of this paper is to describe MDCT findings of the literature)1. various types of abdominal wall hernias (inguinal, femoral, Predisposition to the development of hernias is often related obturator, Spigelian, lumbar, intercostal, ventral and incision- to any cause of increased intraabdominal pressure1, with the al) and their content, evaluating the presence of incarceration most common causes being obesity, chronic cough and asci- and obstruction (table 1). tes. Conditions that favor localized or generalized weakening of the abdominal wall, such asaging, trauma, previous Review surgery and deficient collagen, should also be considered2. Hernias of the abdominal wall are common findings on multi- Inguinal hernias detector computed tomography (MDCT), ranging from small Inguinal hernias, whether direct or indirect, are the most hernias with fat content to large sacs containing loops or or- common abdominal wall hernias. They occur both in chil- gans3. MDCT provides an excellent anatomic detail of the ab- dren (most often the indirect type) and adults (both direct dominal wall, allowing accurate identification of wall hernias and indirect types), and up to 15% of athletes complain of and their differentiation from other abdominal masses, such pubalgia5. as tumors, hematomas or abscesses. In addition, this method The inguinal canal is a diagonal passage formed by the apo- allows detection of eventrations in patients who are difficult neuroses of the three abdominal wall muscles. The anterior to evaluate (e.g., obese patients,postsurgical patients or pa- wall is formed by the aponeuroses of the internal and exter-

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Table 1: Type of hernias and their locations.

Type of hernia Location

Inguinal Direct:medial to the epigastric vessels Indirect: within the inguinal canal, lateral to the epigastric vessels Femoral Protruding through the femoral canal below the inguinal ligament, medially to the femoral vessels Obturator Protruding through the obturator foramen, between the obturator and pectineal muscles Lumbar Disruption of thoracolumbar fascia at insertion of aponeurosis of internal oblique and transverse abdominal muscles Spigelian At the junction of the semilunar line and the arcuate line Ventral Umbilical: secondary to weakness in the umbilical canal Epigastric: at midline through linea alba above umbilicus Hypogastric: at midline through linea alba below umbilicus Abdominal intercostal It occurs through a lower intercostal space by various mechanisms Incisional (eventration) It may occur at any site of the abdomen where there is an incision or wall weakness

Figure 1 Axial multidetector computed tomography image Figure 2 Axial multidetector computed tomography image shows an indirect inguinal hernia (curved arrow) with fat shows a direct inguinal hernia (curved arrow), medial to fem- and small bowel loops contents. Note the epigastric vessels oral vessels (straight arrow), containing bowel loops. Note (black arrow) and the hernia neck (straight white arrows). the epigastric vessels (black arrow). nal oblique muscles, the posterior wall by the transversalis labia majora, respectively. The neck of the hernia sac may be fascia and the conjoint tendon, the superior wall by the apo- seen at the deep inguinal ring 1 (ﬁg. 1). A ﬁnding that helps neuroses of the internal oblique and transverse muscles, and characterization of this type of hernia is “the hook sign”, the inferior wall by Poupart’s inguinal ligament1. which takes its name from the concave shape adopted by the The indirect inguinal hernia passes through the internal ingui- proximal course of the inferior epigastric artery on the axial nal ring into the inguinal canalto emerge through the exter- plane when compressed by an indirect hernia6. nal inguinal ring, arising lateral and superior to the course of Direct hernias emerge above the inguinal ligament medially the inferior epigastric vessels. It may extend along the sper- to the inferior epigastric vessels, and are generally acquired. matic cord or the round ligament into the scrotum or the Their incidence increases with age due to weakening of the

40 Rev. Argent. Radiol. 2017;81(1): 39-49 G. Matzke et al.

a b

Figure 3 Coronal (a) and axial (b) multidetector computed tomography images show a femoral hernia (curved arrow in b) with fat content and a loop of small bowel (straight arrow in a), causing closed loop intestinal obstruction. Note the change in loop diameter (curved arrow in a).

Table 2: Location of inguinal and femoral hernias.

Indirect inguinal hernia Direct inguinal hernia Femoral hernia

Hernia neck anterior to the inguinal ligament, Hernia neck anterior to the inguinal ligament, Posterior to the lateral to the inferior epigastric vessels medial to the inferior epigastric vessels inguinal ligament, Search for the hook sign Crescent Sign medial to the femoral vessels transversalis fascia in the Hesselbach triangle1. They are more which is formed by the deep fascia (fascia lata) of the thigh common in men and are less oftenassociated with strangula- and contains the femoral artery, the femoral vein, and the fem- tion of the loops, possibly because they usually do not tra- oral canal, from lateral to medial1.This type of hernia is more verse the entire course of the canal4 (fig.2). The inguinal canal common in women and it usually occurs on the right side4. contents are compressed laterally, while the fat of the canal On MDCT the neck of the hernia sac can be seen as a nar- is shaped as a moon crescent, resulting in the crescent sign (a row protrusion through the femoral ring, caudal to the origin finding that is helpful for characterization of direct inguinal of the inferior epigastric vessels and medial to the common hernias)7. femoral vein, which often appears compressed by the hernia sac (fig. 3). Sometimes at clinical examination it is difficult to differentiate between femoral and inguinal hernias; there- Femoral hernia fore MDCT plays an important role in differentiation and as- Less common than inguinal hernias, femoral hernias occur sessment of hernia contents2. The hernia sac most frequently when the peritoneal content protrudes into the femoral canal contains small bowel loops; however, the appendix may also with the femoral vein and artery4. This region is simpler than be found within this canal, which is rare (1% of cases) and the inguinal canal in its configuration, bordered superiorly by known as De Garengeot hernia9 (table 2). the inguinal ligament, medially by the medial border of the adductor muscle, laterally by the Sartorius muscle with the ilio- Obturator hernia psoas, pectineal and long adductor muscles forming its floor8. The clinical diagnosis of obturator hernia is difficult because its The main characteristic of the triangle is the femoral sheath, incidence is uncommon, its location is deep and there are few

Rev. Argent. Radiol. 2017;81(1): 39-49 41 A Tour of the Abdominal Wall: An Assessment of Hernias by Multidetector Computed Tomography

specific signs and symptoms, as those associated with obtura- herniation of the small bowel between the external obturator tor nerve compression (Howship-Rombeng sign)10. The obtura- and pectineal muscles, with small bowel obstruction with no tor foramen is formed by the continuity of the pubic and ischial apparent cause3 (fig. 4). bones, and it is covered by the obturator membrane, except in the anterosuperior aspect, where it is perforated by the obtu- Spigelian hernia rator artery, vein and nerve, which travel along a 2-3-cm tunnel A Spigelian hernia is a rare acquired ventral hernia4. It occurs formed by the internal and external obturator muscles. Perito- through defects in the aponeuroses of the internal oblique neal hernia develops through this defect11. and transverse abdominal muscles, with a typical location at Obturator hernias occur more commonly in elderly multipa- the junction of the semilunar line with thesemicircular or ar- rous women, secondary to weakness of the pelvic floor, but cuate line3. It occurs laterally to the rectus abdominis muscle they may also be seen in patients with increased abdominal and inferiorly to the umbilicus and it is nearly always found pressure and in frail elderly patients1. above the level at which the inferior epigastric vessels perfo- Specific diagnosis can be made if the pelvic MDCT shows rate the posterior wall of the rectus abdominis sheath1. a b

Figure 4 Axial (a) and coronal (b) multidetector computed tomography images of a left obturator hernia (curved arrows). Straight arrows reveal the obturator foramen. a b

Figure 5 Axial multidetector computed tomography image of right (a) Spigelian hernia with fat content (curved arrow), lateral to the anterior rectus abdominis muscle (straight arrow), and left (b) Spigelian hernia (curved arrow) with fat and small bowel loops contents (straight arrow).

42 Rev. Argent. Radiol. 2017;81(1): 39-49 G. Matzke et al.

Clinical diagnosis of Spigelian hernias is not easy because The most common etiologies are thought to be trauma or such hernias extend between muscular or fascial layers of the surgery. anterior abdominal wall. The hernia orifice may be small and Intercostal hernias are mostly located under the ninth rib and difficult to locate, and often contains omental fat (fig. 5a), the main symptoms are lower chest swelling and pain. Com- small bowel loops (fig. 5b) or metastatic implants12 (fig. 6). plications are similar to those of other hernias, namely, incarceration and strangulation (fig. 8). Lumbar hernia Diagnosis is made by MDCT, which detects the hernia sac Lumbar hernias may occur at weak points in the posterolat- protruding between the ribs16. eral abdominal wall4: the superior lumbar triangle or triangle of Grynfelt, bordered superiorly by the twelfth rib, medially Ventral hernia by the quadratus lumborum muscle, laterally by the internal Ventral hernias include all hernias in the anterior and lateral oblique muscle and posteriorly by the spinal muscle; and the abdominal wall, such as umbilical, epigastric and hypogas- inferior lumbar triangle or Petit triangle bordered by the ex- tric hernias1. Umbilical hernias consist of protrusion of the ternal oblique muscle anteriorly, the latissimus dorsi muscle abdominal content through the umbilical ring. They are the posteriorly, and the iliac crest inferiorly 2,13. most common type and have a variable size, ranging from Lumbar hernias are most often acquired (occurring spontane- very small (most usually) to middle-sized17 (fig. 9). They are ously, secondary to trauma or postsurgically). Spontaneous ten times more common in women and their risk factors in- hernias account for approximately 50% of all lumbar hernias clude multiple pregnancies, ascites and obesity3 (fig. 10). Epi- and most frequently occur in the superior triangle; they may gastric hernias, in turn, develop on the linea alba, between contain bowel loops, retroperitoneal fat or the kidney14. the xiphoid process (fig. 11) and the umbilicus, while hypo- Symptoms may be varied and confusing. Sometimes patients gastric hernias occur on the midline below the umbilicus1. present with lumbar pain or post-incisional neuralgia1 (fig. 7). Incisional hernias (Eventration) Intercostal Hernia An eventration is a subcutaneous protrusion of the intraab- Called abdominal intercostal hernia by some authors, this is a dominal contents through a weakened area of the abdominal rare condition of which very little is known15. It causes protru- or lumbar wall resulting from a previous surgical procedure, sion of fat or abdominal viscera under an intact diaphragm. a gap secondary to blunt trauma or to congenital malfor-

Figure 6 Axial multidetector computed tomography image Figure 7 Axial multidetector computed tomography image of a Spigelian hernia of a secondary implant in the abdominal of a small right lumbar hernia with retroperitoneal fat con- wall (curved arrow). The anterior rectus abdominis muscle is tent (curved arrow), located posteriorly to the right kidney shown as reference (straight arrow). (straight arrow).

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Figure 8 Coronal multidetector computed tomography im- Figure 9 Axial multidetector computed tomography identi- age of a left intercostal hernia with fat and small bowel loops ﬁes a small umbilical hernia (curved arrow) with mesenteric content (straight arrow), showing intercostal spaces involved fat content, medially to both anterior rectus abdominis mus- (curved arrows). cles (straight arrows).

Figure 10 Axial multidetector computed tomography of an Figure 11 Axial multidetector computed tomography shows umbilical hernia (curved arrow) with fat and small bowel a large epigastric hernia (curved arrow) with left lobe of the loops content (straight arrow). liver protruding (straight arrows). mation. It may occur in any surgical incision on the abdomi- toms within the first year, although 5-10% may remain silent nal wall, including the laparoscopic trocar insertion sites. It for a long period until their detection2. is more commonly encountered in association with vertical Radiological studies may be used to visualize the herniated seg- than with transverse incisions1. ments and to evaluate associated complications such as intesti- Most incisional hernias develop during the first 4 months af- nal obstruction. They are often used in those patients who are ter surgery, a critical period for the healing of muscular layers difficult to evaluate, such as those with marked obesity, easily of the abdominal wall18. They may manifest signs and symp- reducible hernia content or large scars19 (figs. 12 and 13).

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Figure 12 Axial multidetector computed tomography image Figure 13 Axial multidetector computed tomography iden- shows a middle-sized incisional hernia (curved arrow) con- tiﬁes a transverse incisional hernia (curved arrow) showing taining small bowel loops (straight arrow). eventration of the bladder roof (straight arrow).

Figure 14 Axial multidetector computed tomography image shows a large epigastric hernia (curved arrow) with protrusion of the left lobe of liver (black straight arrow), pyloric antrum and bowel loops (white straight arrow). a b

Figure 15 Axial (a) and coronal (b) multidetector computed tomography images show markedly distended gallbladder herniation (curved arrows).

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Figure 16 Axial multidetector computed tomography image Figure 17 Axial multidetector computed tomography of the of an umbilical hernia (curved arrow) with a solid implant abdomen shows an umbilical hernia (curved arrow) with peri- (straight arrow) secondary to an ovarian tumor (Sister Mary toneal fat content (white straight arrow) and ascites (black Joseph’s node). straight arrow).

Figure 18 Axial multidetector computed tomographyimage Figure 19 Axial multidetector computed tomographyimage shows lumbar hernia (curved arrow) containing part of the shows a large bilateral inguinal hernia (curved arrows) with right lobe of liver (straight arrow). distended small bowel loops (straight arrow). a b

Figure 20 Axial (a) and sagittal (b) multidetector computed tomography detects an inguinal hernia (curved arrow) with protruding bladder roof (cystocele) (straight arrow).

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Figure 21 Axial multidetector computed tomography identi- ﬁes a small right inguinal hernia (curved arrow) containing the vermiform appendix (straight arrow), conﬁrmed by surgery (Amyand hernia). a b

Figure 22 Axial (a) and coronal (b) multidetector computed tomography images showvermiform appendix (curved arrow) within the femoral canal, medial to the femoral vessels (straight arrow). This hernia is known as De Garengeot hernia.

Figure 23 Axial multidetector computed tomography shows Figure 24 Sagital multidetector computed tomography of a transverse incisional hernia (curved arrow) containing a an incisional hernia (curved arrow) with protruding bladder transplanted kidney (black straight arrow) and the bladder (straight arrow). roof (white straight arrow).

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