Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_1047_Библиотеки_им_академика_М_И_Перельмана.pdf
56
R. K. Mathur and N. Goyal
in diagnosis but also facilitate demonstration of
ndings to the surgeon, which can be helpful in
surgical planning.
4.2 MDCT Technique
Several MDCT techniques have been utilized
in the evaluation of abdominal wall hernias and
almost all of these are acceptable. The routine
abdominal CT scan is performed in supine position using positive water-soluble oral and IV contrast. The data set acquired can be reconstructed
in multiple other planes without loss of resolution, e.g., a data set if obtained at 5 mm scan
thickness can be retrospectively reconstructed
at sub millimeter scan thickness which permits
exquisite multiplanar reconstruction with isotropic resolution. Some hernial orices/defects are
better appreciated in oblique planes.
In those cases where the hernias are clinically
silent or are suspected, various maneuvers which
create an increase in intraabdominal pressure like
straining/Valsalva maneuver can help precipitate
those hernias which manifest only on increase in
intraabdominal pressure.
Contrast-enhanced CT scan, especially arterial
phase, is necessary for establishing the integrity of
the vascular supply of the bowel wall. Oral contrast is essential in evaluating all types of hernia as
it delineates the bowel loop and enables tracking
of the movement of contents through the bowel.
Real-time MPR images provide useful information supplementing those provided by axial
images and in delineating the size and shape of
the hernial orice and its associated complications, if any. Displaying the images in multiple
anatomical planes increases the understanding of
imaging ndings by the surgeon.
4.2.1 Abdominal Wall Anatomy
(Fig.4.1)
Anterior abdominal wall extends superiorly from
the xiphoid process of sternum and costal cartilage
to the iliac crest and pubic bones of the pelvis inferiorly. Anterior abdominal wall has multiple layers
including skin, subcutaneous fat, fascia (supercial and deep), muscles, fascia transversalis, and
parietal peritoneum. Muscle layer includes the
external oblique muscle, internal oblique muscle,
Rectus abdominis muscle
Transverse abdominis
muscle
Fig. 4.1 CT anatomy of the anterior abdominal wall
Linea alba
Internal oblique muscle
External oblique muscle
Epigastric
Umbilical
Obturator
4 Imaging ofAbdominal Wall Hernias
Incisional
Femoral
lumbar
Inguinal
57
Table 4.1 Types of hernia
Groin hernias Inguinal Femoral
Direct
Indirect
Ventral hernias Anterior Lateral
Umbilical Spigelian
Paraumbilical
Epigastric
Hypogastric
Lumbar
Incisional
Rare Abdominal Pelvic
Interparietal Sciatic
Richter Obturator
Littre Perineal
Traumatic
Fig. 4.2 Pictorial presentation of sites of various abdom-
inal wall hernias
transverse abdominis muscle antero-laterally, and
rectus abdominis muscle anteriorly. The fascia
surrounding the anterolateral muscles fuse anteriorly and attaches to rectus abdominis muscle at
the linea semilunaris. CT images clearly depict
the anterior abdominal wall anatomy, precisely
delineating the layers of anterior abdominal wall,
abdominal wall muscles and peritoneal cavity.
4.3 Types ofAbdominal Wall
Hernias (Fig.4.2)
Hernias may be congenital or acquired and occur
in various anatomical sites of the abdominal wall.
Hernias are primarily classied by the location
and content, majority being inguinal hernias
(75%), followed by femoral hernias (15%) and
umbilical hernias (8%) [1] (Table4.1).
4.4 Groin Hernias
Inguinal hernias: Inguinal hernias are the most
common type of abdominal wall hernias. Two
types of inguinal hernias are indirect and direct.
Indirect inguinal hernias are more common in
children. In adults both direct and indirect hernias are seen with equal frequency.
Indirect hernias pass through the inguinal canal into the scrotal sac lateral to inferior epigastric vessels and occur due to failure
of obliteration of processus vaginalis. It is a
peritoneal extension along the spermatic cord
up to the testis [3]. Inguinal hernias are more
common in male population irrespective of the
age. Direct inguinal hernias are medial to inferior epigastric vessel and result from acquired
defect in transversalis fascia of the Hesselbach
triangle. These are commonly seen in the age
group of 30–40years and are often bilateral [3]
(Fig.4.3).
Femoral hernia: Femoral hernias are less frequent than inguinal hernias and are more common in females. Anatomically these hernias pass
through the femoral canal, medial to femoral
vein and posterior to the inguinal ligament [3, 4].
These hernias are more common on the right side
[5] (Fig.4.4).
The femoral artery and inferior epigastric artery form the basis for differentiation
between inguinal and femoral hernia (Fig.4.5).
Radiologically it is difcult to differentiate
between these two hernias, and femoral hernias
have a higher tendency to incarcerate [5, 6].
58
R. K. Mathur and N. Goyal
a
b
c
*
Fig. 4.3 Inguinal hernia; axial images (arrow) depicting bilateral inguinal hernia (arrows) with right-sided herniation
of fat and left-sided herniation of bowel loops (∗) as hernial contents
a
b
c
Fig. 4.4 Femoral hernia; Axial (a, b), MPR coronal (c), and sagittal images (d) hernial orice (arrow) with bowel in
hernial contents
d
Indirect inguinal hernia
Femoral vessels
4 Imaging ofAbdominal Wall Hernias
Fig. 4.5
Differentiation of
femoral from direct
and indirect inguinal
hernia
59
Inferior epigastric artery
direct inguinal hernia
Femoral hernia
4.5 Ventral Hernias
Ventral hernias occur in anterior and lateral
abdominal wall. Midline ventral hernias include
umbilical, paraumbilical, epigastric, and hypogastric hernias. Amongst these, umbilical hernias
are the most common.
small, seen more commonly in women, and are the
most common type of ventral hernia. Umbilical hernia occurring in children is due to failure of closure
of umbilical ring. During the embryonic period,
there is physiological herniation of intestinal loops
through the umbilicus, which returns to abdominal
cavity by the 12th week of gestation. In the middle-aged and elderly they occur due to increased
intraabdominal pressure secondary to ascites, obesity, and sometimes large intraabdominal masses.
Umbilical hernias are usually small and run a higher
risk of incarceration (Fig.4.6). Hernial contents are
either omental fat or bowel loops (Fig.4.7).
are abdominal wall defects, through the linea alba
adjacent to the umbilicus, and are due to diastasis of the rectus abdominis muscle [7] (Fig.4.8).
Paraumbilical hernias superior to umbilicus are
called epigastric hernias and inferior to umbilicus
are called hypogastric hernias. Epigastric hernias, like umbilical hernias, contain fat, vessels,
and sometimes abdominal viscera. These hernias
Umbilical Hernia: Umbilical hernias are usually
Paraumbilical Hernia: Paraumbilical hernias
are usually clinically occult and become apparent
only after onset of complications like incarceration and strangulation.
Paramedian Hernia: Paramedian hernias are
defects lateral to the midline and usually have
omentum and small bowel as hernial contents.
These are relatively less common; however, the
risk of incarceration is high.
Spigelian Hernia: Spigelian hernia occurs
through the defect in anterior abdominal wall
adjacent to the linea semilunaris and is also known
as spontaneous lateral ventral hernia. The hernial
defect is located in Spigelian fascia between the
lateral border of rectus abdominis muscle and
linea semilunaris. Linea semilunaris is the curved
tendinous intersection on either side of rectus
abdominis muscle and extends from the cartilage
of ninth rib to the pubic tubercle and is formed
by aponeurosis of internal oblique muscle, reinforced laterally by external oblique muscle and
posteriorly by transversus abdominis muscle.
Spigelian hernia is usually is seen at the site
of decient posterior sheath and it is interparietal
with herniation occurring through the aponeurosis
of transverse and internal oblique muscles. It is
contained within the intact aponeurosis of external oblique muscle i.e. between the muscles of
abdominal wall. Incidence is about 1.5% of all the
abdominal wall hernias. The contents are usually
omentum and small bowel loops [8] (Fig.4.9).
60
ab
R. K. Mathur and N. Goyal
Fig. 4.6 USG reveals anterior abdominal wall defect
marked as (+). There is herniation of omentum and bowel
in the hernial sac (arrow). (a) Umbilical hernia; CT
showing midline anterior abdominal wall defect with her-
niation of omentum through it. (b) Small umbilical hernia
showing separation of rectus abdominis muscle and herniation of omental fat limited to subcutaneous fat
Fig. 4.7 Afferent and efferent loops in anterior abdomi-
nal wall hernia. White arrow depicts afferent loop and red
arrow depicts efferent loop. Herniated bowel is normal in
caliber with normal attenuation of omentum suggesting
nonobstructed hernia
4 Imaging ofAbdominal Wall Hernias
Fig. 4.8 Paraumbilical hernia containing omental fat and no vessels (arrow)
61
a
*
c
Fig. 4.9 Spigelian hernia. (a, b, c and d) Contiguous axial
sections through lower abdomen showing herniation of
bowel and omentum through the spigelian fascia with
white arrow depicting intact external oblique muscle, (∗)
b
d
depicting hernial contents and arrow head depicting internal oblique and transverse abdominis muscles. (b) Arrow
in gure (b) depicts the hernial defect
62
Quadratus lumborum
external
oblique
internal
oblique
erector spinae
ab
R. K. Mathur and N. Goyal
4.6 Lumbar Hernias
Lumbar hernias are less common than groin or
anterior abdominal wall hernias. These hernias
occur posteriorly through the defects in lumbar
muscle. Lumbar hernia generally occurs through
the posterior fascia below the 12th rib, bounded
by the erector spinae muscle medially and
external oblique muscle laterally and iliac crest
inferiorly.
Lumbar hernia can be of two types, occurring
through superior or inferior lumbar triangle. The
hernia through superior lumbar triangle is called
Fig. 4.10 Normal
anatomy of the
posterior abdominal
wall muscle depicting
site of lumbar hernia
(arrow)
Grynett-Lesshaft and is bounded by internal
oblique muscle anteriorly, 12th rib superiorly
and spinal muscles posteriorly [9]. The inferior
lumbar hernia called Petit is bounded by external
oblique muscle anteriorly, iliac crest inferiorly,
and lattisimus dorsi posteriorly [9] (Fig.4.10).
Lumbar hernias are usually a sequel to surgery or previous trauma [9]. They occur more
commonly in males with age ranging from 50 to
70 years. Contents of lumbar hernia vary from
bowel loops, retroperitoneal fat, and kidneys with
strangulation being a common complication [8]
(Fig.4.11).
psoas
transversalis fascia
Fig. 4.11 Lumbar hernia: defect along the lumbar triangle (a, b) reveals herniation of large bowel through the wall
defect. (c, d) Sagittal and coronal MPR images reveal the hernia through lumbar muscles
4 Imaging ofAbdominal Wall Hernias
cd
Fig. 4.11 (continued)
63
4.7 Incisional Hernias
Incisional hernias occur as complications of
prior abdominal surgery due to breakdown of
fascia. More commonly seen with vertical incisions compared to transverse incision with a high
prevalence in obese patients, and chronic smokers [3,10]. These hernias occur in rst the few
months following abdominal surgery and the incidence ranges from 0.5 to 13.9% [10]. Incidence
of incisional hernias is reported to be as high as
41% following surgery for aortic abnormalities
[10, 11]. 5–10% of incisional hernias remain dormant for up to 5years [10].
Parastomal hernias are a subtype of incisional
hernias. They occur adjacent to a stoma and are
therefore difcult to detect clinically. CT shows
bowel loops herniating through the opening of
stomal site.
4.7.1 Other Rare Hernias
oftheAbdominal Wall
Interparietal: Interparietal hernias are also called
interstitial hernias. The hernial sac is limited
between the abdominal wall muscles without
extension into the subcutaneous tissue.
Richter: Richter hernia refers to the herniation of antimesentric wall of bowel without
involving the entire wall circumferentially. It can
occur through any of the abdominal wall hernial
orices described above. It usually does not lead
to bowel obstruction.
Litter: It is a type of inguinal hernia which
contains Meckel’s diverticulum.
Complications, as in other types of hernias,
are incarceration and strangulation.
4.7.2 Other Hernias ofthePelvic
Floor
Pelvic hernias occur mainly in elderly women
and are acquired due to a weakness in muscles of
the pelvic oor.
Obturator hernias pass through the obturator foramen between the pectineus and obturator
muscles, and are more commonly seen on the
right side [9].
Sciatic hernias pass through the greater and
lesser sciatic foramina. Contents of the obturator
64
R. K. Mathur and N. Goyal
and sciatic hernia are usually small bowel loops
or rarely ureter or urinary bladder [9].
Perineal hernias are not common and seen
mainly in elderly females occurring in gluteal
region, adjacent to labia majora and anus [9, 12].
4.8 Traumatic Hernias
Blunt traumas resulting from high-velocity
motor vehicle accidents lead to sudden increase
in intraabdominal pressure resulting in disruption
of abdominal wall musculature and herniation
of abdominal contents. These defects can range
from small to large depending upon the severity
of the injury and due to the degree of compression on impact [13].
The common sites of posttraumatic hernias are
through the areas of relative anatomic weakness,
which are lumbar region and the lower abdomen
[13]. Abdominal contents can herniate into the
chest through a diaphragmatic rupture. These
hernias are also associated with other intraabdominal injuries in about 60% of cases [13].
4.9 Complications ofAbdominal
Wall Hernias
Bowel obstruction, incarceration, and strangulation are the most common complications of
abdominal wall hernias [14]. Common presenting symptoms of complications of hernia are
abdominal pain and distention.
Clinical evaluation will usually be difcult if
complications are present, because of pain and
tenderness. However, it may reveal an abdominal
mass, which is tender, rm, and irreducible.
Further complications will lead to peritoneal
signs, which will present as dehydration, discoloration of skin, and derangements of systemic
vital signs [15].
Imaging studies are necessary to differentiate hernia from other causes of abdominal mass
and abdominal pain, when symptoms or clinical
assessment is confusing [6]. Imaging studies also
help to evaluate the complications of hernia and
associated systemic manifestations, improving
patient outcome [16]. Accurate and timely diagnosis is mandatory for early diagnosis and appropriate management of complications.
4.9.1 Bowel Obstruction
Abdominal wall hernias are the second most
common cause of small bowel obstruction with
an incidence of about 10–15% [17].
Bowel obstruction occurs after the strangulation or incarceration of the hernia with the transition point at the hernial orice or within the
hernial sac.
The commonest content in abdominal wall
hernia is the omentum and bowel loops. If it
contains bowel then there is an afferent and an
efferent loop. The proximal segment of bowel
herniating through the defect is afferent loop
and the distal segment of bowel entering back
in abdominal cavity through the defect is the
efferent loop (Fig.4.7). The obstruction usually
occurs at either the entry point of afferent loop or
exit point of efferent loop, and sometimes within
the herniated loop due to a twist.
CT ndings will reveal dilatation of bowel
loops proximal to the site of obstructed hernia and normal or collapsed bowel distal to the
obstruction (Fig.4.12). The bowel loops within
the hernial sac may or may not be dilated. The
dilatation will depend on whether the obstruction
is occurring at the point of entry or at the point
of exit. There will be narrowing of the afferent or
efferent limbs at the hernial orice.
The extent of dilatation of the proximal bowel
loop indicates the degree of obstruction, and if
it is acute or subacute, complete or incomplete.
One nding of obstructions is “Fecal sign” which
is identied by presence of particulate material
mixed with gas within the lumen of obstructed
dilated bowel loops.
4.9.2 Incarceration
Incarceration refers to the clinical diagnosis of an
irreducible hernia, when the hernial contents cannot be reduced or pushed back into the peritoneal
4 Imaging ofAbdominal Wall Hernias
65
a
b
*
c
d
e
Fig. 4.12 Obstructed anterior abdominal wall hernia: (a)
arrow showing afferent loop which is dilated (b) Arrow
showing collapsed efferent loop. The site of obstruction is
at the entry point of bowel. There is marked dilatation of
bowel loop proximal to efferent loop in the abdomen and
there is uid in hernial sac due to mesenteric congestion.
(c, d) MPR images in sagittal and coronal planes depicting the hernia. (e) Conservative management of hernia
with manual reduction of hernia and no bowel loops are
seen in the hernial sac