Making the transition: the role of helical CT in the evaluation of potentially acute thoracic aortic injuries.

OBJECTIVE: The purpose of this study was to show that helical CT could be used at our center in lieu of routine aortography to examine patients who have had serious blunt chest trauma. We also wanted to assess the potential savings of using CT to avoid unnecessary aortography. MATERIALS AND METHODS: The institutional review board approved the parallel imaging-CT immediately followed by aortography-of patients presenting with blunt chest trauma between August 1997 and August 1998. To screen patients for potential aortic injuries, we performed parallel imaging on 142 patients, and these patients comprised our patient population. CT examinations of the patients were reviewed for signs of injury by radiologists who were unaware of each other's interpretations and the aortographic results. Findings of CT examinations were classified as negative, positive, or inconclusive for injury. Aortography was performed immediately after CT. The technical and professional fees for both transcatheter aortography and helical CT were also compared. RESULTS: Our combined kappa value for all CT interpretations was 0.714. The aortographic sensitivity and negative predictive value were both 100%. Likewise, the sensitivity and negative predictive value of CT were 100%. The total costs of performing aortography were estimated at approximately $402,900, whereas those for performing helical CT were estimated at $202,800. CONCLUSION: Helical CT has a sensitivity and negative predictive value equivalent to that of aortography. Using CT to eliminate the possibility of mediastinal hematoma and to evaluate the cause of an abnormal aortic contour in a trauma patient allows us to use aortography more selectively. Avoiding the performance of unnecessary aortography will expedite patient care and reduce costs. We report the results of our experience with CT and how our center successfully made this transition in the initial examination of patients with serious thoracic trauma.

Anterior clear space: how clear? How often? How come?

PURPOSE: To compare the opacity of the retrosternal clear space with that of the retrocardiac region on normal lateral chest radiographs, to measure the clear space, and to evaluate the reasons for these findings. MATERIALS AND METHODS: Left lateral chest radiographs and computed tomographic scans of 38 patients with normal studies were evaluated and the results were correlated. RESULTS: In 19 (50%) patients, retrosternal and retrocardiac opacity were equal. In 16 (42%), the retrosternal region was more opaque than the retrocardiac region (10 of 12 women, six of 26 men). The difference between the sexes was statistically significant (P = .002). In only nine (24%) patients was the anterior margin of the ascending aorta defined on the lateral study. Mean sternum-to-aorta distance in these patients was 29 mm. CONCLUSIONS: Retrosternal opacity greater than retrocardiac opacity on lateral chest radiographs is a frequent normal finding, especially in women. Sternum-to-aorta distance may be difficult to measure, and distance greater than 2.5 cm may be normal in some persons.

Chronic traumatic pseudoaneurysm of the thoracic aorta: a report of two cases following gunshot injury.

Gunshot injury to the thoracic aorta is nearly always fatal. Although the victim usually will succumb to exsanguination or tamponade in the minutes following injury, unusual cases of occult injury occur when a pseudoaneurysm, occlusion, or fistula forms at the site of injury. We report two patients with gunshot injury to the thoracic aorta that resulted in chronic pseudoaneurysms that went undetected for 325 and 46 days, respectively. Computed tomography and aortography were utilized to verify these pseudoaneurysms, and both patients underwent successful surgical repair.

Cardiac valve reconstruction and replacement: a brief review.

Surgical methods for improving the function of diseased cardiac valves are valve reconstruction (valvuloplasty) and valve replacement with mechanical prostheses, biologic prostheses, or homograft (donor) valves. Reconstruction is used primarily for incompetent mitral and tricuspid valves and addresses each part of the valve apparatus individually. Annuloplasty rings are often used to restore the size and shape of the valve orifice. Long-term anticoagulation therapy is not necessary. The designs of mechanical prostheses have evolved since the early caged-ball prostheses. Current models are noted for their durability. Patients who undergo implantation of these prostheses must also undergo long-term anticoagulation therapy. Biologic prostheses made from porcine valves or bovine pericardium are not as durable as their mechanical counterparts, but they do not require long-term anticoagulation therapy. Homografts are used in relatively few centers. They have good hemodynamics and do not necessitate long-term anticoagulation therapy. Radiologists should be familiar with the radiographic appearance of the various valve prostheses and annuloplasty rings and with the advantages and disadvantages of their use in cardiac valvular surgery.

"Hyperdense" aortic wall: potential pitfall in CT screening for aortic dissection.

Opacity of the aortic wall as compared with the nonopacified blood in the lumen has been utilized as one of the criteria for the diagnosis of aortic dissection. It has also been suggested that this finding may be indicative of severe anemia. We evaluated the frequency and implications of aortic wall hyperdensity in 107 consecutive chest CT examinations in patients with no indication of aortic dissection clinically or by other imaging modalities, and whose hematocrit was known. The density of the wall correlated with the patient's age and presence of calcification. Presence or absence of anemia was not a statistically significant factor, although marked conspicuousness of the wall below the age of 60 years did suggest anemia. Atherosclerosis is the most likely explanation for wall visibility in nonanemic patients.

Apparatus seen on chest radiographs after cardiac surgery in adults.

The authors review the purpose, radiographic appearance, and possible complications of various tubes, catheters, and wires seen on chest radiographs after cardiac surgery. Drainage tubes, temporary epicardial wire electrodes, surgical clips, intraaortic counterpulsation balloon, atrial pressure monitor catheters, and sternal wires are reviewed. Because recent articles have discussed the Swan-Ganz catheter and automatic implantable cardioverter defibrillator, these are not covered in depth.

Mediastinal histoplasmosis granuloma: evaluation with CT.

Mediastinal granuloma secondary to histoplasmosis was described in three patients. Computed tomographic scans in each patient demonstrated a large, low-attenuation mediastinal mass crossed by enhancing septae. Other granulomatous diseases may produce similar abnormalities. The differential diagnosis of such lesions was discussed.

Mediastinal carinal bronchogenic cyst: is its mere presence an indication for surgical excision?

A notion has prevailed that carinal bronchogenic cyst and other congenital mediastinal cystic lesions, particularly those occurring in older children and adults, are usually asymptomatic, innocuous, and frequently only an incidental finding on routine chest roentgenogram or postmortem examination. Some physicians, therefore, have adopted a policy of observation for these patients. Our experience, however, as demonstrated in three cases reported herein, and the experience of others, clearly shows that carinal bronchogenic cyst is far from being usually asymptomatic and innocuous, but in fact often produces a broad spectrum of clinical manifestations, some of which are life-threatening. Mere observation not only places these patients at serious risk, but also increases the possibility of missed diagnosis and delayed treatment of those lymphoproliferative malignancies involving mediastinal lymph nodes that can mimic a carinal bronchogenic cyst. Computerized tomography (CT) is the single most important method of making a diagnosis of carinal bronchogenic cyst. We believe strongly that the mere presence of a mediastinal carinal bronchogenic cyst is an indication for surgical excision.

Retrocardiac phantom image on hypocycloidal chest tomograms.

A phantom image produced by displaced blur margins of the cardiac silhouette and mimicking a paraspinous retrocardiac mass was noted in 50% of 125 hypocycloidal full chest tomograms. It was reproduced on tomograms of a chest phantom. Careful comparison with routine posteroanterior and lateral chest radiographs prevents misinterpretation.

Another look at the "ring-around-the-artery" in pneumomediastinum.

Gas surrounding the right pulmonary artery has been observed in three patients, including two in whom it was demonstrated around the intrapericardial right pulmonary artery on frontal films. This would provide a pathway for occasional development of spontaneous pneumopericardium.

Blunt traumatic rupture of the right hemidiaphragm: experience in 12 patients.

In a 9-year period (1972 to 1981), 35 patients with blunt traumatic rupture of the diaphragm were seen in our institution; 12 had involvement of the right hemidiaphragm, an incidence of approximately 34%. In 9 of these 12 patients, the right-sided diaphragmatic injuries were seen soon after the accident (acute), and in 3, late after the accident (chronic). A large diaphragmatic rent, usually 10 cm or more, without any predilection to a specific area of the right hemidiaphragm, was a frequent operative finding. Expectedly, the most common viscus that was injured or herniated through the defect was the liver. Total or nearly total herniation of the liver was noted in 5 patients and partial herniation, in 1. Injury to the juxtahepatic vena cava or hepatic vein, or both, was also encountered in 5 patients. This highly lethal injury accounted for the 3 deaths in the series, all of which were directly related to an uncontrollable exsanguinating hemorrhage from the injured vena cava or hepatic vein. The surgical approach for repair of a ruptured right hemidiaphragm is best individualized. The right thoracotomy approach through a right posterolateral incision is preferred for chronic diaphragmatic injury. It is also our choice in patients in whom acute right-sided injuries are definitively diagnosed and who are hemodynamically stable. This approach not only provided the best exposure of the defect, but also made the repair of associated retrohepatic caval injury surprisingly easy in at least 2 of our patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Descending necrotizing mediastinitis.

From January 1975 through July 1981, ten patients with mediastinitis complicating an oropharyngeal infection, that is, a form of mediastinitis best termed as DNM, were encountered at our institution. Based upon rather relatively stringent diagnostic criteria, 21 other instances were found in the literature from 1960 to 1980, a time period well into the antibiotic era. The predominant underlying oropharyngeal infection was of odontogenic origin, specifically, infection involving the mandibular molars. Bacteriologically, DNM is most frequently a polymicrobial process, with anaerobes playing a major role. Although there has been a decline in the over-all incidence of DNM since the introduction of antibiotics, its morbid and lethal nature persists, as evidenced by the present prohibitive mortality of approximately 42 per cent. Delayed diagnosis and inadequate drainage procedures are the primary underlying factors contributing to this high mortality. At present, CT scan is the single most important tool for the early diagnosis of DNM. This noninvasive procedure also helps determine the adequacy of the surgical drainage procedure performed. However, with all the presently available diagnostic tools, it is still the high index of suspicion by physicians toward patients with unrelenting oropharyngeal or deep neck infection that is of utmost importance for making an early diagnosis of DNM. In view of our experience and that of others, we believe that only through aggressive combined medical and surgical management can the highly morbid, if not lethal, course of DNM be reversed. It should be emphasized that, to accomplish successful operative intervention, a thorough knowledge of the complex anatomy of the region is crucial.

Azygos vein abutting the posterior wall of the right main and upper lobe bronchi: a normal CT variant.

In 9% of 78 normal computed tomographic examinations, the azygos vein was interposed between the posterior wall of the right-main or right-upper-lobe bronchi and lung in the azygoesophageal recess. Observation of the azygos vein on contiguous scans will generally allow a confident identification of this normal variant. Contrast enhancement will elucidate difficult cases.

The effect of search time on perception.

A group of 100 carefully selected chest radiographs was read by ten observers, five experienced and five inexperienced. The radiographs were chosen to present the readers with a disproportionately large number of both subtle abnormalities and nonpulmonary lesions. Each reader was allowed to search the radiographs for as long as appropriate, up to a maximum of four minutes. The length of time taken for each observation was recorded to the nearest second. The time-perception data were plotted on both linear and semilogarithmic graphs. The results showed that experienced readers concluded their visual search while positive detection rate was higher than the rate for false-positives. For lesions in the central phasic, with both a rapid and a slow component of perception. If these data are plotted on a semilogarithmic scale, each of the two components plots as a straight line. For lesions in the periphery of the radiograph (chest wall and upper abdomen), the time-perception curve is monophasic, showing only a slow component.

Visible muscle of the diaphragm: sign of extraperitoneal air.

Epiphrenic air collections may be difficult to compartmentalize. The air may be in the peritoneal cavity, extraperitoneal or extrapleural spaces, or in a pleural cavity. Extraperitoneal and extrapleural air usually comes from a pneumomediastinum, but it may arise from an intraabdominal source, such as a ruptured second part of the duodenum. Pneumoperitoneum is frequently the only radiographic sign of a perforated hollow viscus. The radiologist is confronted with an important differentiation. A pneumoperitoneum may indicate a need for abdominal surgery and a pneumothorax may require surgical aspiration; but extraperitoneal and extrapleural air require no specific treatment, assuming that the source of the air can be ascertained and the quantity does not compromise respiration. A new sign is described to assist in the recognition of extraperitoneal and extrapleural air. When the muscle bundles of the diaphragm are outlined by air, the air must be between the parietal peritoneum and parietal pleura and thus be extraperitoneal and/or extrapleural in location. This sign was observed in five patients.

Hepatic and thoracic amaebiasis.

Sonographic and radiographic fidings were reviewed in 27 patients with hepatic amebiasis. Sonography usually demonstrated nonspecific, peripheral, hypoechoic lesions. The only diagnostic sonographic appearance was a combination of a hypoechoic lesion and diaphragmatic disruption, which was found in four patients. About 50% of the patients had accompanying radiographic abnormalities that were nondiagnostic. These included elvation of the right hemidiaphragm, basilar pulmonary infiltrates, and pleural effusions. Liver abscesses occasionally grew during the first 2 weeks of treatment even though the patients were responding well to medical therapy. Lesions frequently became more anechoic and better defined on follow-up examinations. Successfully treated abscesses may calcify rather than diminish.

Anaerobic pleural and pulmonary infections.

Radiographic findings are reviewed for 69 patients with bacteriologically proven anaerobic infections in the thorax. On the initial films, the disease was confined to the lung parenchyma in 50%, and to the pleura in 30% of patients. The other 20% had combined pleural and parenchymal disease. Over 50% of cases had lung necrosis on the initial films, and many patients who began with a noncavitary pneumonia developed necrosis during hospitalization despite antimicrobial therapy. Once necrosis developed, resolution was slow with an average closure of 65 days for lung abscesses. Parenthymal disease was usually confined to one anatomic site. This site was almost always in a basal or posterior part of the lungs. Pleural effusions tended to progress very rapidly and always proved to be empyemas. Many empyemas occurred without recognizable pneumonic disease. A few were nosocomial, occurring as a complication of surgery, penetrating chest wounds, or subphrenic abscesses. Many patients developed empyemas as a complication of parenchymal disease, frequently while on antimicrobial therapy. Almost all empyemas required surgical drainage with either a rib resection or decortication.

Left lateral decubitus sonography of gallstones in the contracted gallbladder.

A prospective study of the accuracy in diagnosing gallstones using ultrasonography in the absence of a fluid-filled gallbladder was done over a 20 month period; 91 patients were studied. A focal echo complex with acoustic shadowing was shown to be a highly reliable criterion for diagnosing gallstones in a contracted gallbladder when (1) it was demonstrated on longitudinal, transverse, and left lateral decubitus views, and (2) the configuration of the echo complex remained the same.