Deep venous thrombosis and pulmonary embolism after major reconstructive operations on the spine. A prospective analysis of three hundred and seventeen patients

We performed a prospective study of 317 patients in order to determine the prevalence of deep venous thrombosis after reconstructive operations on the spine; 126 of the patients were examined with duplex ultrasound assessments of the lower extremities to ensure that no asymptomatic thrombi were being missed. Thigh-high stockings and sequential pneumatic compression of the lower extremities were used, in all patients, for prophylaxis against venous thrombosis. No antiplatelet agents or anticoagulant medications were administered. There was no evidence of thrombosis on any of the duplex ultrasound studies. Subsequently, venous thrombosis developed and was treated successfully in one of the 126 tested patients and in one of the 191 untested patients, and a fatal pulmonary embolus developed in one of the untested patients. The over-all clinical prevalence of thrombotic complications was 0.9 per cent (three complications in 317 patients). All three of the patients who had clinical evidence of thrombosis had had an anterior lumbar procedure because of a degenerative disorder or trauma; however, we could not prove that this approach or these diagnoses were significant risk factors for thrombosis (p < 0.05). While it is possible that some thrombi may have escaped both clinical and ultrasonic detection, such thrombi apparently were not enough of a danger to warrant the use of intensive prophylactic procedures that are associated with more risk. On the basis of this prospective study, therefore, we think that routine screening for the detection of asymptomatic thrombosis in patients who have had a procedure on the spine is unwarranted.

Mediastinal masses: alternative approaches to CT-guided needle biopsy

PURPOSE

To determine how the use of alternative anatomic approaches to mediastinal masses in biopsies guided with computed tomography (CT) affects success and complication rates.

MATERIALS AND METHODS

The medical records and imaging studies in 36 consecutive patients who underwent percutaneous mediastinal biopsy were reviewed. Alternative techniques to avoid penetration of the visceral pleura during biopsy of mediastinal masses were used in 12 patients. These included a pleural space approach through pleural effusion or iatrogenic pneumothorax, lateral decubitus positioning, and direct semicoronal scanning to guide suprasternal biopsy.

RESULTS

Adequate material for diagnosis was obtained in 34 of 36 patients (94%), 22 of 22 biopsies (100%) of anterior mediastinal masses, six of eight biopsies (75%) of middle mediastinal masses, and six of six biopsies (100%) of posterior mediastinal masses. Pneumothorax occurred in two of 36 patients (6%); this low complication rate was associated with infrequent use of the transpulmonary approach.

CONCLUSION

CT guidance can enable an individualized approach to a mediastinal mass to avoid penetration of the visceral pleura, large blood vessels, and bronchial tree and thereby lower the rate of complications.

Sonographic parallel channel sign: a reappraisal

Tubular structures proximal to the right and left hepatic ducts, when seen with ultrasonography, are generally considered to be abnormally dilated ducts. However, newer, electronically focused transducers reveal peripheral tubular structures paralleling portal venous branches. The diameters of all visible tubular structures that would have been thought to be bile ducts were measured in 50 persons with no evidence of hepatobiliary disease. "Ducts" were seen with the following frequencies: right hepatic, 100%; right anterior, 100%; right posterior, 88%; left hepatic, 98%; left medial, 62%; left lateral, 96%; left lateral superior, 54%; and left lateral inferior, 54%. All ducts proximal to the right and left hepatic ducts were 2 mm or less in diameter. Those proximal to the common hepatic ducts averaged approximately 20% of the diameters of their accompanying portal veins. Except for 4% of the left lateral inferior ducts, no ducts proximal to the common hepatic ducts were more than 40% the diameter of their respective portal vein branches. Mere observation of parallel channels proximal to the right and left hepatic ducts is therefore not evidence of biliary dilatation.

Evaluation of ectopic bone by CT

The CT appearance of ectopic bone and its maturation in 25 patients were correlated with the findings on radiographs and bone scans. Ossification progressed from an early appearance of soft-tissue density of lower attenuation than muscle to a calcific density paralleling radiographic and scintigraphic evidence of bone formation. Persistent unossified, low-density soft tissue was detected adjacent to mineralized areas of ectopic bone in 14 patients up to 16 years after neurologic injury, often with bone-scan evidence of maturity of the ectopic bone. This soft tissue most likely corresponds to immature, unossified connective tissue, which may have a potential for ossification. Detection of areas of soft-tissue density by CT and their avoidance during surgical resection of an ankylosing mass of ectopic bone may reduce intraoperative hemorrhage and postoperative ectopic bone recurrence.

Bolus contrast medium enhancement for distinguishing pleural from parenchymal lung disease: CT features

Various morphologic criteria have been proposed to distinguish pleural from pulmonary parenchymal processes using CT. Although these criteria are helpful in most instances, they are not infallible. In a retrospective review of chest CT over a 1 1/2 year period, previously described signs were not sufficient to distinguish pleural from parenchymal disease in five patients who underwent routine contrast-enhanced CT. This was true in cases of large, localized areas of air-space disease and in cases of combined pleural and parenchymal disease. In these patients bolus intravenous contrast medium administration at the plane of major abnormality proved extremely useful for diagnosis by directly demonstrating pulmonary blood vessels and/or contrast enhancement in parenchymal processes.

Hypervascular hepatic metastases: CT evaluation

Recent reports have indicated that non-contrast material-enhanced scans are of less value than urographic contrast material-enhanced studies in the computed tomographic (CT) evaluation of hepatic metastases. The authors retrospectively reviewed the CT scans of 28 patients with hypervascular liver metastases to determine whether these metastases were more likely to become isodense with the liver after contrast material enhancement, thus necessitating the performance of non-contrast-enhanced scanning. Non-contrast-enhanced and contrast-enhanced incremental dynamic scanning was performed in patients with proved liver metastases from carcinoid tumors (13 patients), islet cell neoplasms (ten patients), pheochromocytomas (four patients), or renal cell carcinoma (one patient). Eleven of the 28 patients (39%) had metastases with non-contrast liver-to-lesion attenuation differences greater than 15 HU. These metastases subsequently became isodense or nearly isodense on contrast-enhanced scans. The authors conclude that non-contrast-enhanced CT scanning should be performed in patients with suspected liver metastases from tumors that are usually hypervascular.

CT Diagnosis of a Mycotic Aneurysm of the Thoracoabdominal Aorta

The CT appearance of a mycotic aneurysm involving the thoracoabdominal aorta with adjacent vertebral osteomyelitis is presented. Specific CT features of the aneurysm, such as lack of intimal calcification and adjacent bone destruction or abscess, may allow the diagnosis to be made in the appropriate clinical setting.

Silicone encircling bands for retinal detachment: CT appearance

Silicone encircling bands are placed around the eyeball routinely during retinal detachment surgery. We present two cases that show the characteristic appearance of such a band on CT.

Neonatal osteomyelitis examined by bone scintigraphy

Thirty-three infants less than six weeks of age and suspected of having osteomyelitis were examined by bone scintigraphy. Each of the 25 sites of proved osteomyelitis in 15 individuals demonstrated abnormal radionuclide localization. Ten additional scintigraphically positive but radiographically normal sites were detected. Optimal quality scintigrams of the growth plate complex and osteomyelitis in neonates appeared similar to those in older children. All neonates suspected of having osteomyelitis should be studied with bone scintigraphy following initial radiographs.