Diagnostic Ultrasound - Abdomen and Pelvis
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Diagnostic Ultrasound - Abdomen and Pelvis

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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 609

Approach to Sonography of Abdominal Wall/Peritoneal Cavity Diagnoses: Abdominal Wall/Peritoneal Cavity (Left) Transverse ultrasound shows the right inguinal area over an intermittent lump. During the Valsalva maneuver, fat and peristalsing bowel st were seen to bulge inferomedially from the origin of the inferior epigastric artery on the external iliac artery ſt, compatible with an indirect inguinal hernia. (Right) Transverse panoramic ultrasound shows the abdominal wall of a lump developing after umbilical hernia repair. The lump corresponds to a small fluid collection ſt. The abdominal fascia st was intact. (Left) Transverse ultrasound of the right upper quadrant performed for painful mass shows an ovoid collection with internal echoes ſt. No flow was seen on color Doppler. The liver st and gallbladder were normal. (Right) NECT in the same patient on anticoagulants confirms a hematoma ſt in the right rectus sheath. There is surrounding fat stranding st. (Left) Transverse highresolution color Doppler ultrasound of an umbilical mass shows a lobulated soft tissue mass ſt, which was firm and had internal vascularity. Biopsy showed an epithelioid sarcoma. (Right) NECT in the same patient shows the umbilical metastasis ſt; however, CT also showed diffuse omental tumor st but no ascites, which would have enhanced detection of the omental mass. 610

Approach to Sonography of Abdominal Wall/Peritoneal Cavity<br />

Diagnoses: Abdominal Wall/Peritoneal Cavity<br />

(Left) Transverse ultrasound<br />

shows the right inguinal area<br />

over an intermittent lump.<br />

During the Valsalva maneuver,<br />

fat <strong>and</strong> peristalsing bowel st<br />

were seen to bulge<br />

inferomedially from the origin<br />

of the inferior epigastric artery<br />

on the external iliac artery<br />

ſt, compatible with an<br />

indirect inguinal hernia.<br />

(Right) Transverse panoramic<br />

ultrasound shows the<br />

abdominal wall of a lump<br />

developing after umbilical<br />

hernia repair. The lump<br />

corresponds to a small fluid<br />

collection ſt. The abdominal<br />

fascia st was intact.<br />

(Left) Transverse ultrasound of<br />

the right upper quadrant<br />

performed for painful mass<br />

shows an ovoid collection with<br />

internal echoes ſt. No flow<br />

was seen on color Doppler.<br />

The liver st <strong>and</strong> gallbladder<br />

were normal. (Right) NECT<br />

in the same patient on<br />

anticoagulants confirms a<br />

hematoma ſt in the right<br />

rectus sheath. There is<br />

surrounding fat str<strong>and</strong>ing st.<br />

(Left) Transverse highresolution<br />

color Doppler<br />

ultrasound of an umbilical<br />

mass shows a lobulated soft<br />

tissue mass ſt, which was<br />

firm <strong>and</strong> had internal<br />

vascularity. Biopsy showed an<br />

epithelioid sarcoma. (Right)<br />

NECT in the same patient<br />

shows the umbilical<br />

metastasis ſt; however, CT<br />

also showed diffuse omental<br />

tumor st but no ascites, which<br />

would have enhanced<br />

detection of the omental<br />

mass.<br />

610

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