Biomedical subjects
Publications and source records attributed to W A Rubenstein.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Explore the source record for details and available documents.
The computed tomographic (CT) appearances of 19 hyperdense renal cysts in nine patients are reported. Sixteen of these cysts were found over a period of only 1 year with state-of-the-art CT equipment. Hyperdense renal cysts are probably more common than suggested by case reports. Their rate of detection can be expected to increase with the wider availability of fast CT scanners using thin collimation. A CT diagnosis of benign hyperdense renal cyst can be made if a lesion meets all of the following criteria: (1) smoothly outlined imperceptible wall with sharp demarcation from the kidney; (2) before intravenous contrast injection, homogeneous internal content with CT numbers 40%-240% higher (70%-240% higher for lesions 10 mm or more in diameter) than renal parenchyma; and (3) after intravenous contrast injection, persistent internal homogeneity and insignificant enhancement (less than 6%) relative to normal renal cortex. For masses exceeding 15 mm in diameter, sonography can be a valuable confirmatory test.
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.
The CT applications described above are based on our experience with an integrated ultrasound-CT approach, tailored to the patient and aimed at reducing radiation and invasive diagnostic procedures. This approach is not presented as the ideal example to be followed by all. Rather, it is only a sample of the many possible uses of CT. Though there may be many disagreements with our approach, there can be no doubt that CT has revolutionized diagnostic abdominal imaging, to the benefit of all concerned.
Invaginations of the muscular fibers of the diaphragm into the upper abdomen may appear as nodules of soft tissue density on computed tomographic (CT) sections in deep inspiration. If these nodules indent the adjacent stomach or distal transverse colon, they may mimic small mural tumors or metastatic implants. Similar nodules protruding from the diaphragmatic crura into the adjacent retroperitoneal fat may be mistaken for enlarged lymph nodes on CT. Differential diagnosis of these pseudotumors from pathologic lesions is based on their continuity peripherally with the diaphragm and their separation from the hollow viscera by subdiaphragmatic fat. Decubitus and expiratory CT sections are valuable diagnostic aids.