Appendiceal CT in 140 cases. Diagnostic criteria for acute and necrotizing appendicitis.

Computed tomography (CT) was performed in 140 patients with suspected acute appendicitis. Thin collimation (5 mm), intravenous contrast enhancement, 1-second scan times, and supplementary cecal air insufflation were emphasized. CT accuracy was 98% overall (137/140), and 99% in the 124 cases with early surgery. Necrotizing appendicitis was diagnosed by CT with 86% accuracy and 90% positive predictive value.

CT and US of the pancreas.

The diagnostic capabilities of pancreatic imaging continue to improve with technological advancements in computed tomography (CT), ultrasound (US), and magnetic resonance imaging (MRI). To update the practicing radiologist, this article summarizes the current literature on pancreatic imaging, with particular emphasis on CT and US. Pertinent clinical considerations of the disease entities are included, along with illustrative material from the authors' experience.

Sonographic diagnosis of cisternal subarachnoid hemorrhage in the premature infant.

PURPOSE: To evaluate sonographic criteria for the diagnosis of subarachnoid, and particularly cisternal, hemorrhage in the preterm infant. METHODS: The subarachnoid cisterns were studied on cadaveric anatomic sections and on postmortem ultrasonograms, as well as on in vivo ultrasonograms of healthy neonates. Based on the normal ultrasound appearances of these cisterns, criteria were developed for the recognition of abnormal cisternal fluid collections, which strongly suggest the presence of subarachnoid hemorrhage in the premature infant. These criteria were evaluated prospectively in a group of 63 preterm infants who underwent subsequent autopsy. RESULTS: In the 63 infants with neuropathologic verification, increased echogenicity and/or increased echo-free content of the subarachnoid cisterns correctly predicted subarachnoid hemorrhage with an accuracy of 75%, sensitivity of 69%, and specificity of 93%. The positive and negative predictive values were 97% and 46%, respectively. In 47% of the cases, ultrasound correctly detected cisternal subarachnoid hemorrhage before intraventricular hemorrhage could be diagnosed. CONCLUSION: A highly specific, although somewhat insensitive, sonographic diagnosis of subarachnoid hemorrhage can be made from the appearance of the subarachnoid cisterns. The diagnosis of subarachnoid hemorrhage may predate the ultrasound diagnosis of intraventricular hemorrhage and may alert the neonatologist to the need for follow-up sonograms in the absence of ultrasound evidence of intraventricular hemorrhage.

MR imaging of portal venous thrombosis: correlation with CT and sonography.

Fourteen patients with portal venous thrombosis (PVT) diagnosed by CT and/or sonography were studied with MR. Three of the 14 had portal hypertension. The MR findings were compared with those of eight patients with portal hypertension, but without CT or sonographic evidence of PVT. MR imaging showed portal venous thrombosis in all 14 PVT cases. Intraluminal thrombi of less than 5 weeks duration appeared markedly hyperintense relative to liver and muscle on both T1- and T2-weighted images. Older thrombi appeared hyperintense relative to liver and muscle in eight of 11 cases, but only on T2-weighted images. MR showed thrombi in 11% more portal vessels than did CT (MR = 30, CT = 27) and in 28% more vessels than did sonography (MR = 32, sonography = 25). MR also showed 24% more collateral vessels than did CT (MR = 31, CT = 25) and 50% more vessels than did sonography (MR = 33, sonography = 22). Third-echo images (echo time = 96 msec, repetition time = 1500-2150 msec) verified the presence of venous thrombi in 28 (93%) of 30 PVT vessels, and they differentiated flow-related intravascular signal from true thrombi in six (17%) of 36 portal hypertension vessels. We conclude that MR is a valuable tool for imaging portal vein thrombosis. MR is a good substitute for CT and can be more informative than sonography.

Computed tomography and magnetic resonance imaging of a superior gluteal artery pseudoaneurysm.

The magnetic resonance and computed tomography appearances of a superior gluteal artery pseudoaneurysm are described, with emphasis on the relative advantages and disadvantages of these two imaging procedures.

Perirenal spaces: CT evidence for communication across the midline.

The perirenal spaces may communicate across the midline, anterior to the lower aorta and vena cava. The connecting channel has a relatively narrow anteroposterior dimension on computed tomographic (CT) scans, both in vivo and in injected cadavers. It may therefore be difficult to visualize on abdominal radiographs and may be mistaken for unopacified bowel on CT scans. The midline extension of perirenal fluid is usually contiguous to the lower abdominal great vessels anteriorly but does not surround them completely, possibly because of fibrous septa within the perivascular fat. Hematomas from ruptured aortic aneurysms extend mainly into the perirenal spaces. Thus, the lower abdominal great vessels are located, in effect, within the midline extension of these spaces. Superiorly, the perirenal spaces extend to the diaphragm, abutting the lateral and anterior margins of the psoas and quadratus lumborum muscles and the bare area of the liver. Inferiorly, perirenal collections appear to diverge into the pelvis, along the psoas muscles, ureters, and iliac vessels.

Computed tomography appearance of adrenal vein thrombosis.

The computed tomography appearance of adrenal hemorrhage secondary to adrenal vein thrombosis is illustrated. The lesion appeared radiolucent, with a small focal calcification, mimicking an adrenal adenoma. Hypercoagulopathy was an underlying factor in this patient with myelofibrosis and chronic myelogenous leukemia.

Computed tomography of renal aspergillosis.

The CT and sonographic findings of a case of localized, invasive aspergillosis of the kidney are presented.

CT of fibrous tissues and tumors with sonographic correlation.

Fibrous tissues and tumors may appear hyperdense relative to muscles and solid viscera on CT both before and after IV contrast injection. In addition, fibrous tissues generally have a homogeneously hypoechoic sonographic appearance. The diagnostic value of these criteria is illustrated in a group of 21 fibrous tissue abnormalities that includes retroperitoneal, mediastinal, and perigraft fibrosis, sclerosing pseudotumor of the orbit, generalized fibromatosis, desmoids, malignant fibrous histiocytoma, and normal tendons and ligaments. It is concluded that while hyperdensity on CT and echopenia on sonography are not pathognomonic of fibrous tissue, they occur with sufficient frequency that their presence raises the possibility of a fibrous lesion.

Intraperitoneal paravesical spaces: CT delineation with US correlation.

The urinary bladder, obliterated umbilical arteries, and inferior epigastric vessels located within the extraperitoneal space of the anterior abdominal wall indent the anterior parietal peritoneum, forming intraperitoneal paravesical fossae. These are the supravesical space and the medial and lateral inguinal fossae. More posteriorly, the peritoneum covering the bladder is reflected onto the rectum to form the rectovesical space, which is divided by the uterus into an anterior vesicouterine recess and a posterior rectouterine pouch, or cul-de-sac. The cul-de-sac is continuous with the pararectal and ovarian fossae and is bounded posterolaterally by the rectouterine (sacrogenital) folds. These peritoneal compartments form a large potential space for the accumulation of ascites and are separated from the equally large extraperitoneal paravesical spaces by only a thin layer of peritoneum or peritoneum and umbilicovesical fascia. The computed tomographic scans of 100 patients with ascites were reviewed, with particular attention to the differentiation between intraperitoneal and extraperitoneal paravesical collections. The scans of intraperitoneal collections were found to have certain characteristic appearances, including inferior displacement of the distended urinary bladder, visualization of the umbilical folds, and preservation of the preperitoneal fat.

Extraperitoneal paravesical spaces: CT delineation with US correlation.

The extraperitoneal space around the urinary bladder is lamellate, just like the retroperitoneal space around the kidneys. The bladder, urachus, and obliterated umbilical arteries lie within the perivesical space, surrounded by umbilicovesical fascia, analogous to the perinephric space within the renal fascia. A much larger prevesical space, analogous to the anterior pararenal space, lies anterior and lateral to the umbilicovesical fascia. Posterior to the urinary bladder, the lower uterine segment or seminal vesicles lie within the perivesical space, rather than in a separate compartment, corresponding to the posterior pararenal space. The cul-de-sac, and the inferolateral extension of its peritoneal layers as the rectovaginal or rectovesical septum, separate the posterior perivesical space from the rectum. The sectional anatomy of these spaces, and particularly their computed tomographic and ultrasound appearances, were noted in normal anatomic sections, patients with extraperitoneal fluid collections, and a cadaver into which fluid was injected.

Computed tomography, sonography, and MR imaging of abdominal tuberculosis.

The CT, sonographic, and magnetic resonance findings of a case of abdominal tuberculosis are presented. A diffusely thickened, enhanced peritoneum was imaged best on CT. Sonography was the only imaging modality to demonstrate septations within the tuberculous ascites. Magnetic resonance contributed no additional information.

Computed tomography, sonography, vesiculography, and MR imaging of a seminal vesicle cyst.

A case of crossed ectopia of seminal vesicle cyst is reported. Magnetic resonance (MR) appearance of the seminal vesicle cyst is described first. Brief review of the literature for the seminal vesicle cyst is made and role of new imaging modalities including ultrasound, CT, and MR is discussed.

The portacaval space: CT with MR correlation.

Between the portal vein and the inferior vena cava lies a small space that may be occupied by multiple anatomic structures including the caudate and papillary processes of the caudate lobe of the liver, portacaval lymph nodes, replaced or accessory right hepatic arteries, posterosuperior pancreaticoduodenal vessels, the cystic duct, and the epiploic foramen to the lesser sac. The sectional anatomy of these structures is illustrated in this paper with particular emphasis on the portacaval nodes. Unlike the adjacent celiac lymph nodes, portacaval nodes appear rectangular or elliptical on transverse sections and may measure up to 1.3 cm in anteroposterior dimension. They may mimic portions of the pancreas, liver, or biliary tract on sectional images.

Posterior peritoneal recesses: assessment using CT.

Intraperitoneal compartments may extend posteriorly to the level of known retroperitoneal structures at several locations within the abdomen. These locations include the posterior subhepatic or hepatorenal space, the splenorenal space, the retropancreatic recess, the paracolic gutters, and the pararectal fossae. Because of their posterior location, fluid collections within these compartments may be mistaken radiologically for retroperitoneal masses. The sectional anatomy of these spaces, and particularly their appearance on computed tomographic scans, are illustrated in this paper.

The oblique coronal view in sonography of the retroperitoneum.

The abdominal aorta and inferior vena cava can be seen easily from the right flank on a longitudinal coronal-oblique sonogram, using the liver as an acoustic window. With this view, tortuosity of the abdominal aorta can be shown, just as it appears on frontal aortography in 70% of cases, and similar to aortography in 27% of cases. The proximal renal and common iliac arteries can be demonstrated in 73% and 82% of cases, respectively, when aneurysms are absent, and in 45% and 82% of patients when aortic aneurysms are present. Enlarged posterior abdominal lymph nodes may be detected with accuracy, sensitivity, and specificity of 90% when compared to computed tomography (CT). Prominent gonadal vessels and anomalous or duplicated venae cavae can be displayed longitudinally, just as they might appear on venography. The coronal oblique view from the right flank, and occasionally from the left flank, can be a valuable addition to the standard views obtained during abdominal sonography. It is also a valuable supplement to CT in the differentiation of paraaortic vessels from enlarged lymph nodes.

CT of the pericardial recesses.

Within the pericardial cavity there are several recesses where fluid can collect in close contiguity to the major bronchi and lymph nodes. These include the transverse sinus, behind the ascending aorta and pulmonary trunk; the oblique sinus, behind the left atrium; and the left pulmonic recess, between the left pulmonary artery and the left superior pulmonary vein. There are also smaller pericardial recesses between the superior and inferior pulmonary veins, posterolateral to the superior vena cava, and between the inferior vena cava and coronary sinus. An understanding of sectional anatomy is valuable for differentiation of fluid within these recesses from mediastinal masses or enlarged lymph nodes on computed tomographic scans.

Posterior hepatodiaphragmatic interposition of the colon: ultrasonographic and computed tomographic appearance.

High posterior hepatodiaphragmatic interposition of the colon is an unusual normal variant that may mimic posterior hepatic lesions, posterior retroperitoneal masses, or a disrupted right diaphragm on sonography. The correct diagnosis of this entity may be suggested on plain abdominal films, and is made easily with computed tomography.

Accessory fissures of the liver: CT and sonographic appearance.

Invaginations of the liver by the diaphragm form accessory fissures that may mimic the major hepatic fissures on sectional images. Accessory fissures are most common in the superior right hepatic lobe. Their average incidence on computed tomographic (CT) scans is 25%. Their frequency increases with age, approaching 70% in the seventh and eighth decades. Their depth may equal or exceed 2 cm in one-third of cases. Multiple accessory fissures may mimic pathologic liver nodules on CT and may be associated with diaphragmatic scalloping or eventration on the chest film. When only parts of these fissures are seen sonographically, they may be mistaken for echogenic liver lesions. The differentiation of accessory fissures from the major hepatic fissures, from pathologic lesions, and from sonographic pseudofissure artifacts is discussed.