Diagnostic Ultrasound - Abdomen and Pelvis

Approach to Sonography of Abdominal Wall/Peritoneal Cavity
more extensive masses and collections CT or MR are indicated
given their wider field and depth of view. Furthermore, CT and
MR are less limited by body size and not limited by gas which
may be present in a hernia or abdominal wall abscess.
Patients should be examined supine initially with images in
transverse and longitudinal planes. Hernias should be
distinguished from soft tissue masses by position, sonographic
appearance and dynamic maneuvers. Evaluation for groin or
abdominal wall hernia is not complete without provocative
maneuvers such as Valsalva, coughing or standing positions.
Compression with the transducer is used to determine
reducibility of hernias; however, too much probe pressure
may reduce a hernia and prevent detection unless provocative
maneuvers are utilized. Stored cine clips are very useful for
review. For the posterior abdominal wall, patients are initially
imaged prone. Comparison to the other side is very helpful for
all hernias and subtle masses.
Groin hernias: Initially, the transducer is oriented transversely
and over the lateral rectus muscle half way between the
umbilicus and pubis. The inferior epigastric artery and vein are
identified posterior to the rectus muscle and followed
inferiorly as they course laterally. Spigelian hernias are located
along the lateral edge of the rectus muscle, typically where
the inferior epigastric artery is lateral to the muscle. Where
the inferior epigastric artery arises from the external iliac
artery localizes the deep inguinal ring. The transducer is then
rotated to be parallel and perpendicular to the inguinal canal.
Indirect inguinal hernias arise between the external iliac artery
and the proximal inferior epigastric artery. Moving the
transducer inferomedially identifies the superficial inguinal
ring. Direct inguinal hernias protrude through here, inferior
and medial to the inferior epigastric artery. Next the
transducer is placed below and parallel to the the inguinal
canal and evaluation is made for femoral hernias. The
saphenofemoral junction identifies the femoral canal. Most
femoral hernias are medial to the common femoral vein. At all
these locations, systematic evaluation is made at rest and
during Valsalva. Hernia size and contents such as fat, fluid or
peristalsing bowel are assessed. Tenderness and reducibility
are evaluated. Evaluation of the asymptomatic contralateral
potential hernia sites are recommended.
Incisional or ventral hernias: A similar protocol with dynamic
maneuvers is used at the site of symptoms. Incisional hernias
occur at surgical sites and penetrate through muscle. They
may be quite large and may require a curvilinear transducer or
CT when complex or complicated by strangulation. In the
midline a true hernia should be distinguished from rectus
diastasis which stretches the linea alba along its entire length.
Epigastric or ventral hernias are more focal.
Masses: Targeted ultrasound for masses includes high
resolution gray scale imaging supplemented by color and
power Doppler. Panoramic techniques can be very helpful to
show the relationship of the mass to surrounding structures.
Fluid collections/hematomas: In addition to above, look for
swirling or mobile internal echoes with compression of the
collection, which is a sign of an abscess or acute bleeding.
Hematomas in the rectus sheath may be associated with
active bleeding, which may be detected with color Doppler if
profuse.
Peritoneal Cavity
A 2-5 MHz curvilinear transducer is typically required to assess
the deeper recesses of the peritoneal cavity unless the patient
is small. The anterior peritoneum or superficial intraperitoneal
lesions can be evaluated with a linear higher frequency 8-15
MHz transducer.
Ascites: The most common indication for ultrasound of the
peritoneal cavity is a search for ascites. Right and left upper
and lower quadrants and the midline pelvis are assessed for
free fluid. Fluid initially collects in the hepatorenal recess and
rectovesical pouch spilling over into the rest of the peritoneal
cavity as the volume increases. Causes of ascites such a
hepatic cirrhosis or hepatic congestion may be detected
during the search for fluid. In the setting of abdominal trauma,
ultrasound is used to screen for intraperitoneal bleeding.
Ascites is complex when it contains internal echoes and
septations. This may be secondary to infection (bacterial or
fungal peritonitis), hemorrhage or malignancy. Ultrasound
guidance is useful to target the paracentesis for most
diagnostic value.
Tumor: Malignant ascites is complex and associated with
omental or peritoneal masses and nodules. A careful search
for these ancillary signs and a primary tumor such as ovarian
carcinoma is recommended. A more specific tissue diagnosis
may be derived from biopsy of the solid masses.
Selected References
1. Arend CF: Static and dynamic sonography for diagnosis of abdominal wall
hernias. J Ultrasound Med. 32(7):1251-9, 2013
2. Robinson A et al: Meta-analysis of sonography in the diagnosis of inguinal
hernias. J Ultrasound Med. 32(2):339-46, 2013
3. Wagner JM et al: Accuracy of sonographic diagnosis of superficial masses. J
Ultrasound Med. 32(8):1443-50, 2013
Diagnoses: Abdominal Wall/Peritoneal Cavity
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