DOI:10.2214/AJR.06.0638
AJR 2007; 188:1356-1364
© American Roentgen Ray Society
Characteristic Locations of Inguinal Region and Anterior Abdominal Wall Hernias: Sonographic Appearances and Identification of Clinical Pitfalls
David A. Jamadar1,
Jon A. Jacobson1,
Yoav Morag1,
Gandikota Girish1,
Qian Dong1,
Mahmoud Al-Hawary1 and
Michael G. Franz2
1 Department of Radiology, TC2910, University of Michigan Hospitals, 1500 E
Medical Center Dr., Ann Arbor, MI 48109.
2 Department of General Surgery, University of Michigan Hospitals, Ann Arbor, MI
48109.
Received May 26, 2006;
accepted after revision September 12, 2006.
Address correspondence to D. A. Jamadar.
Abstract
OBJECTIVE. The purpose of this article is to show the typical
locations of anterior abdominal wall and inguinal region hernias and to
illustrate their sonographic appearances and describe pitfalls in clinical
diagnosis of hernias that may be resolved with sonography.
CONCLUSION. Awareness of the expected locations of anterior
abdominal wall hernias and potential clinical pitfalls allows an accurate
diagnosis of a hernia and helps in differentiating a hernia from other
abnormalities.
Keywords: gastrointestinal radiology • hernia • sonography
Introduction
There are a variety of hernias that may occur through the anterior
abdominal wall. These include inguinal hernias (which may be femoral, direct
inguinal, or indirect inguinal), spigelian hernias, umbilical and
paraumbilical hernias, and epigastric hernias. Incisional hernias may occur
after incisions through the anterior abdominal wall.
On clinical examination, it may be difficult to diagnose a hernia with
certainty. In addition, when a diagnosis of hernia is made, it may be
difficult to differentiate between two hernias that occur close together
anatomically [1]. Occasionally,
a patient who presents clinically with a diagnosis of a hernia may be found to
have another cause for the symptoms. Sonography may be useful not only in
providing the diagnosis but also in identifying the variety of hernia and
providing additional information such as the contents of the hernia and the
extent of reducibility of the hernia contents. These observations may affect
surgical decision making and reconstruction.
We describe the use of sonography in evaluation for anterior abdominal wall
hernias and the expected location of these hernias. We show a spectrum of
abnormalities that may simulate a hernia on clinical examination.
Technical Considerations
Because abnormality is confined to the anterior abdominal wall, using a
high-frequency linear transducer is optimal, at least a 7-MHz transducer.
Knowledge of the surface anatomy of the expected location of the common
anterior abdominal wall hernias is important
(Fig. 1) because such knowledge
provides an anatomic framework around which to work. The patient is initially
scanned in the supine position and then examined in the upright position.
Upright scanning is particularly important for evaluation of a femoral
hernia.
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Fig. 1 —Illustration of anterior abdominal wall shows usual anatomic
location of various anterior abdominal wall hernias. Red line in right lower
quadrant indicates inferior epigastric artery. E = epigastric hernia; P =
periumbilical hernia; U = umbilical hernia; Div = infraumbilical divarication
of the rectus abdominis muscles, which may be seen along entire extent of
linea alba; S = spigelian hernia; I = indirect inguinal hernia; D = direct
inguinal hernia; F = femoral hernia.
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The examination of the inguinal region has been described in the literature
[2]. The inferior epigastric
artery is identified where it passes under the lateral border of the rectus
abdominis muscle. From there it can be followed inferiorly to its origin from
the external iliac artery (EIA), which is just cranial to where the inguinal
ligament crosses the EIA. The inguinal ligament and the EIA are two anatomic
structures that allow differentiation between a direct inguinal, indirect
inguinal, and femoral hernia. The deep inguinal ring lies lateral to the
origin of the inferior epigastric artery above the inguinal ligament, whereas
the neck of a femoral hernia lies below the inguinal ligament and usually
medial to the femoral vein. The anterior abdominal wall can be incrementally
scanned from the epigastrium to the pubic symphysis. The Valsalva maneuver
should be liberally used. A hernia may sometimes be better appreciated during
relaxation immediately after a Valsalva maneuver, when the hernia contents may
be seen to return to their pre-Valsalva location, rather than during the
Valsalva maneuver itself. Scanning patients in the supine and in an upright
position or during a particular maneuver that patients associate with their
hernias may facilitate detection.
Evaluation for an incisional hernia may be challenging because the incision
and the tissue distortion by the application of sutures in closing the
incision may result in asymmetry and abnormal movement during a Valsalva
maneuver. Typically, the visible skin incision is an indication of the
approximate incision through the deeper tissues, but this is not always the
case [3]
(Fig. 2). The skin incision may
be shorter than the peritoneal incision, necessitating routine sonographic
evaluation beyond the limits of the visible skin scar
(Fig. 2). Incisional hernias
may also occur lateral to the surgical scar where the suture passed through
the muscle and fascia (Fig. 2).
Last, an incision near an anatomic location where a hernia may occur
necessitates differentiation from an incisional hernia. This may occur, for
example, with an appendectomy scar and an inguinal hernia
(Fig. 3).
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Fig. 2 —Illustration of anterior abdominal wall shows three surgical
incisions, two in which skin incision may not accurately reflect incision
through deeper tissues. Lower abdominal Pfannenstiel incision (bikini cut) is
curvilinear cutaneous and subcutaneous incision (A), but vertical component of
incision is between rectus abdominis muscles, with potential for incisional
hernia (vertical rectangle). Subcostal skin incision (B) is often
shorter than deeper incision with extension along line of incision both
medially and laterally. There is potential for hernia (ovals). Third,
midline vertical incision (C) shows suture perforations (circles) on
either side, a site for incisional hernias (curved arrow).
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Fig. 3 —55-year-old man with clinically diagnosed right groin hernia.
Sonography cranial and parallel to inguinal ligament revealed indirect
inguinal hernia adjacent to appendectomy scar (not shown). Preoperative
diagnosis modified surgical approach. Sonogram after Valsalva maneuver shows
hernia (H) and inferior epigastric artery (arrow). Right side of
image is medial side of structures on sonogram.
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Anterior Abdominal Wall Hernias
Abdominal wall hernias are diagnosed on sonography by visualizing abdominal
contents moving either through an abdominal wall defect or bulging due to
abnormal thinning of the anterior abdominal wall. The abdominal contents may
appear echogenic due to fatty tissue or bowel. The presence of peristalsis
indicates the latter. Fluid and gas may also be seen in the bowel lumen, and
fluid may be seen in the hernial sac and surrounding the herniated contents.
The Valsalva maneuver and often upright positioning are usually required to
detect a hernia.
Inguinal hernias include the indirect inguinal hernia, in which the origin
is lateral to the inferior epigastric artery and superior to the inguinal
ligament (Fig. 4); the direct
inguinal hernia, which is located medial to the inferior epigastric artery and
superior to the inguinal ligament (Fig.
5A,
5B); and the femoral hernia,
located inferior in relation to the inguinal ligament and usually medial to
the femoral vein (Fig. 6). The
uncommon spigelian hernia occurs along the linea semilunaris (the lateral
border of the rectus abdominis) just superior to the inferior epigastric
artery where this artery passes under the lateral border of the rectus
abdominis muscle (Fig. 7).
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Fig. 4 —40-year-old woman with right indirect inguinal hernia. In sonogram
with scanning cranial and parallel to inguinal ligament, inferior epigastric
artery (curved arrow) marks medial boundary of deep inguinal ring and
neck of this hernia (H). Lateral boundary (straight arrow) is less
clearly seen. Right side of image is medial side of structures on
sonogram.
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Fig. 5A —41-year-old man with new inguinal and suprapubic fullness and direct
inguinal hernia. Pre-Valsalva maneuver transverse oblique sonogram shows
external iliac artery (A), inferior epigastric artery (curved arrow),
superior pubic ramus (arrowheads), and echogenic superficial boundary
of hernia (straight arrows) not clearly demarcated. V = femoral
vein.
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Fig. 5B —41-year-old man with new inguinal and suprapubic fullness and direct
inguinal hernia. Post-Valsalva maneuver transverse oblique sonogram shows
echogenic boundary of hernia (straight arrows), which originates
medial to inferior epigastric artery (curved arrow). A = external
iliac artery.
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Fig. 6 —35-year-old man with right femoral hernia. Sonogram caudad and
parallel to inguinal ligament shows femoral vein (arrows) distorted
and displaced ventrally by retrovascular femoral hernia (H). Femoral artery
(A) is lateral in relation to hernia.
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Fig. 7 —41-year-old woman with left spigelian hernia. Transverse sonogram
along linea semilunaris shows lateral border of rectus abdominis (R) and flank
muscles (F) and between them, bowel (B) and extraperitoneal fat (EF) of
hernia.
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Epigastric hernias occur anywhere between the xiphoid process and the
umbilicus and initially consist of extraperitoneal fat that has protruded
through the linea alba (Fig.
8). An umbilical hernia usually occurs in children through a weak
umbilical scar (Fig. 9),
whereas a paraumbilical hernia occurs through the linea alba just above the
umbilicus (Fig. 10) or, less
commonly, just below the umbilicus.
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Fig. 8 —44-year-old woman with epigastric hernia. Longitudinal sonogram
along linea alba shows defect (arrows) in linea alba through which
extraperitoneal fat herniates. Hernia (H) shows no movement during Valsalva
maneuver, which is not unusual for these hernias when small.
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Fig. 10 —69-year-old man with supraumbilical fullness and paraumbilical
hernia. Transverse sonogram shows defect in linea alba through which
extraperitoneal fat herniates (arrows). Rectus abdominis muscles (R)
can be seen on either side of defect.
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Divarication (or separation) of the rectus abdominis muscles (Fig.
11A,
11B) occurs along the linea
alba and is due to stretching and thinning of the linea alba along its length.
This may be seen in elderly multiparous women. The Valsalva maneuver results
in separation of the right and left rectus abdominis muscles and bulging of
the attenuated linea alba.
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Fig. 11A —35-year-old woman with infraumbilical divarication of rectus
abdominis. Pre-Valsalva maneuver transverse sonogram shows both rectus
abdominus muscles (R) closely approximated to midline. Arrowheads show medial
extent of rectus abdominis muscles.
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Fig. 11B —35-year-old woman with infraumbilical divarication of rectus
abdominis. Post-Valsalva maneuver transverse sonogram shows separation of
rectus abdominis muscles (R). Arrowheads show medial extent of rectus
abdominis muscles.
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The incisional hernia presents different diagnostic problems depending on
the anatomy of the incision and the specific layer of abdominal wall closure
that has failed (Fig. 12). An
understanding of the specific incision and careful evaluation with the
Valsalva maneuver are essential to detect these hernias.
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Fig. 12 —39-year-old woman with right upper quadrant discomfort medial to
cholecystectomy incision with incisional hernia (corresponds to medial right
upper quadrant incisional hernia illustrated in
Fig. 2). Transverse oblique
sonogram shows extraperitoneal fat (F) and hernia (H) between posterior rectus
abdominis (R) and adjacent fascia defect (arrows). This unusual
hernia was not appreciated at laparoscopy, and repeat open surgery was
performed to repair hernia, with resolution of symptoms.
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In general, complications of hernias include an irreducible hernia, an
obstructed hernia, and a strangulated hernia. An irreducible hernia is one in
which the contents cannot be reduced in the absence of any other complication.
An obstructed hernia is one in which a loop of viable bowel within the hernia
becomes obstructed. A strangulated hernia is one in which there is vascular
compromise to the bowel within a hernia.
Clinical Pitfalls in Hernia Evaluation
Sonography can be useful to rule out hernia in situations in which this
disease is erroneously suspected by the clinician. Atrophy of the anterior
abdominal wall muscles, as may occur after a surgical incision or after
transverse rectus abdominis myocutaneous flap surgery, with displacement of
the muscles may allow an intraabdominal viscus to be more easily palpable and
present clinically as a possible hernia (Fig.
13A,
13B). Focal spasm in an
abdominal wall muscle may present as a painful transient mass (Fig.
14A,
14B), whereas an incised
abdominal wall muscle that has not healed completely may present as a focal
bulge after abdominal wall contraction during the Valsalva maneuver (Fig.
15A,
15B).
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Fig. 13A —69-year-old woman with complicated bilateral transverse rectus
abdominis myocutaneous flap surgeries and absence of both rectus abdominis
muscles who presented with palpable left upper quadrant mass for exclusion of
incarcerated hernia. Sonograms show palpable abnormality secondary to
abdominal wall atrophy. No hernia is seen. Oblique sonogram shows spleen (S),
which is palpable and simulates mass. K = kidney.
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Fig. 13B —69-year-old woman with complicated bilateral transverse rectus
abdominis myocutaneous flap surgeries and absence of both rectus abdominis
muscles who presented with palpable left upper quadrant mass for exclusion of
incarcerated hernia. Sonograms show palpable abnormality secondary to
abdominal wall atrophy. No hernia is seen. Very thin anterior abdominal wall
is better appreciated by close proximity of underlying bowel (B). Note
centimeter scale to right of image.
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Fig. 14A —27-year-old woman with history of transient painful swelling in
right epigastrium and muscle bulge from focal spasm. Pre-Valsalva maneuver
longitudinal sonogram shows right proximal rectus abdominis muscle
(arrows) directly under focal discomfort.
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Fig. 14B —27-year-old woman with history of transient painful swelling in
right epigastrium and muscle bulge from focal spasm. Post-Valsalva maneuver
longitudinal sonogram in same location as A shows right proximal rectus
abdominis muscle bulging focally (arrows), clinically simulating
hernia.
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Fig. 15A —42-year-old man with focal discomfort and bulge adjacent to right
paramedian appendectomy scar, presumed secondary to postsurgical tissue
scarring. Longitudinal sonogram over right rectus abdominis muscle (M) shows
focal hyperechoic scar (S) at location of patient discomfort.
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Fig. 15B —42-year-old man with focal discomfort and bulge adjacent to right
paramedian appendectomy scar, presumed secondary to postsurgical tissue
scarring. Transverse sonogram shows rectus abdominis muscle (M) and focal
hyperechoic scar (S).
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A normal structure may be noticed for the first time and present as a mass
(Fig. 16). The xiphoid process
may become noticeable after weight loss and present as an epigastric mass. In
this anatomic location, an epigastric hernia may be simulated.
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Fig. 16 —49-year-old man with prominent xiphoid process. Sagittal midline
epigastric sonogram shows hypoechoic cartilaginous xiphoid process (X), which
has ventral curve. Tip (arrow) is closest to overlying skin and under
palpable abnormality.
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Enlarged lymph nodes are often found in the inguinal region. Although
normal inguinal lymph nodes may have a short-axis diameter that measures up to
1.5 cm [4,
5], malignancy may be present
even if the node is not enlarged. Even nodes thought to be normal in size may
raise concern for an inguinal hernia (Fig.
17).
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Fig. 17 —25-year-old woman with right inguinal lymph nodes. Sonogram caudad
and parallel to inguinal ligament shows lymph node (arrows), with
fatty hilum (Hi) medial to femoral artery (A) and femoral vein (V).
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A saphenous varix (Fig. 18)
is a specific diagnosis that can be confused clinically with a femoral hernia,
particularly if it is thrombosed
[6]. This focal dilatation of
the saphenous vein proximal to its passage through the cribriform fascia in
the groin may be differentiated from a femoral hernia on sonography
[7].
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Fig. 18 —53-year-old woman with left saphenous varix. Sonogram over proximal
long saphenous vein shows focal variceal dilation (V) along proximal long
saphenous vein (VV) just before it traverses cribriform fascia to anastomose
with femoral vein (F).
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A hematoma (Fig. 19) or a
focal fluid collection (Fig.
20) may present deep in relation to an incision as a mass. These
can be differentiated from an incisional hernia by their location within the
abdominal wall and the absence of movement during a Valsalva maneuver.
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Fig. 20 —50-year-old woman with wound abscess. Longitudinal sonogram shows
tubular structure with hypoechoic contents (A) with thick and irregular walls
(curved arrows) of wound abscess. Wavy echogenic structure
(straight arrows) deep in relation to abscess is abdominal wall mesh
from prior midline vertical incisional hernia repair.
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An endometrioma (Fig. 21)
after surgery due to endometrial seeding of the surgical incision has been
well described [8] and may
present as a mass. This is also differentiated from an incisional hernia with
sonography by its location within the abdominal wall, indistinct margins, and
absence of movement during a Valsalva maneuver.
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Fig. 21 —34-year-old woman after caesarian section with subcutaneous
endometrioma. Longitudinal sonogram over scar shows ill-defined heterogeneous
mass with indistinct margins and minimal vascularity of endometrioma (E)
superficial to rectus abdominis muscle (R).
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Conclusion
Knowledge of the variety of anterior abdominal wall hernias and their
typical locations and an understanding of the anatomy of surgical scars are
essential to identify anterior abdominal wall and inguinal hernias. Awareness
of the processes that simulate hernias clinically can aid in providing an
accurate diagnosis.
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Abstract
Introduction
