Computerized tomographic appearance of renal cysts after extracorporeal shock wave lithotripsy.

We identified cysts in five kidneys of four patients who had lithotripsy. Three of these kidneys were evaluated with CT scans the day before and the day after lithotripsy and showed no change. The other two kidneys were studied by CT only after extracorporeal shock wave lithotripsy; hemorrhage was shown in one and cyst wall thickening in the other.

Acute bilateral diffuse pulmonary shadowing after evacuation of hydatid mole.

Acute bilateral diffuse pulmonary shadowing complicates the resection of hydatid mole approximately 10% of the time. Etiologic factors include trophoblastic emboli, pulmonary emboli, high output congestive failure, and DIC. Prompt recognition and emergency oxygen therapy with PEEP are imperative for survival.

Computed tomography of isolated osteoblastic colon metastases in the bony pelvis.

Skeletal metastases from colorectal carcinoma are unusual and osteoblastic metastases are quite rare. Three cases are described in which an isolated recurrence of a previous colorectal carcinoma occurred within the pelvic bones, without evidence of skeletal metastases elsewhere so that local spread via portocaval anastomoses in the pelvis is postulated. In all three cases, proliferative calcification and new bone formation occurred within an expansile, destructive lesion, suggesting the occurrence of a synergistic effect between the underlying bone and a malignant neoplasm which has a propensity to calcify.

Computed tomography of low periesophageal focal fat collections.

Focal fat collections in the middle compartment of the lower mediastinum are reported in the literature. However, this explanation for a mass in that location is not widely recognized. We found four cases of focal fat collections on routine computed tomography. We then reviewed 100 consecutive computed tomography scans and found another four examples.

Liver metastases: optimization of MR imaging pulse sequences at 1.0 T.

Twenty patients with known liver metastases were examined with magnetic resonance imaging; four different pulse sequences were used and six different images were produced to allow comparison of pulse sequence performance at a 1.0-T field strength. Pulse sequence performance was in each case calculated by measuring contrast-to-noise ratios (C/N) comparing normal liver, metastatic tumors to liver, and background noise. All pulse sequences required approximately the same length of time for data acquisition. Short inversion time inversion-recovery (STIR) sequences yielded the greatest signal difference-to-noise ratio in 17 patients. Phase contrast images produced the greatest contrast ratio in three patients. Although short TR, short TE spin-echo sequences provided the best anatomic detail, in no patient did this sequence yield the greatest signal difference-to-noise ratio in the comparison of liver and tumor. Differences in field strength and in equipment software and hardware may account for the discrepancy between our findings and previously published data.

Epipericardial fat pad: CT findings.

Epicardial and mediastinal fat around the apex of the heart may produce the classic appearance of a cardiac fat pad filling in the anterior cardiophrenic angle on a lateral chest radiograph. A review of 50 computed tomographic (CT) scans of the chest that were normal save for possible cardiomegaly, together with chest radiographs obtained within a 14-day interval, revealed a wide variation in the configuration of this fat pad in 16 patients (32%). Depending on geometric circumstances, the fat pad may produce a well-marginated region of increased density, a region of increased density with poor margination, or an area of reduced density lying anterior to the heart. In an additional four patients (8%), however, a simulation of a cardiac fat pad was produced by cardiomegaly alone or by relative levoposition of the heart. In these four patients, the left side of the heart contacted the chest wall on the left over a larger than normal area and thereby excluded lung from the vicinity, simulating the appearance of a fat pad where none existed.

Tumor invasion of the anterior skull base: a comparison of MR and CT studies.

Seven patients who had tumors arising in the anterior face or paranasal sinuses and invasion of the anterior skull base were evaluated with magnetic resonance (MR) and high resolution CT. Magnetic resonance was superior in evaluating tumor encasement of the carotid artery and invasion of the cavernous sinus; for assessing the relationship of the tumor to the anterior brain, optic nerves, and optic chiasm; in providing coronal images free from dental artifact; and in determining tumor extent within the infratemporal fossa. Bone destruction was more easily observed on CT than MR.

The variable nature of the mediastinal contour lines: CT/chest radiography correlation.

Interfacing of the lung with the mediastinum produces a number of mediastinal lines including those due to the innominate veins, left subclavian artery, paratracheal stripe, both anterior and posterior junction lines, the azygo-esophageal recess, descending aorta and paraspinal lines. Displacement or absence of one or more of these lines may be due to an abnormality of mediastinal contour or may indicate a mediastinal mass, but can occur in normal subjects. Correlative findings between chest radiography and chest computed tomography in 50 normal subjects illustrate the variable nature of these lines.

MRI vs. high-resolution CT scanning: evaluation of the anterior skull base.

While magnetic resonance imaging (MRI) is no longer a tool of the future, its availability is limited. Most hospitals still use high-resolution computed tomography (CT) scanning as their major imaging modality. Although numerous articles point to the improved diagnostic uses of MRI--as compared to high-resolution CT--a change from high-resolution CT scanning to MRI scanning throughout the United States would cost billions of dollars. We should, therefore, delineate those clinical situations in which magnetic resonance imaging is distinctly superior to high-resolution CT scanning. It is already an accepted fact that MRI provides improved imaging of the central nervous system, but, while recent articles maintain the superiority of MRI head and neck imaging, the advantages to the clinician are less clear. We present representative cases of large malignant tumors of the frontal, ethmoid, and sphenoid sinuses, in which the full extent of the disease which involved intracranial structures and the orbit was better defined on the MRI scan than it was on the high-resolution CT scan. Decisions concerning the involvement of the infratemporal fossa, the cavernous sinus, the optic chiasm, the pituitary, and the frontal lobes were more easily made when based upon magnetic resonance imaging, while the tumor involvement as evaluated by CT scanning was much less clear. Establishment of the problem regions of the head and neck--when magnetic resonance imaging is superior to high-resolution CT scanning--will assist in identification of the true need for this tool in the practice of the otolaryngologist--head and neck surgeon.

Tumor detection with phase-contrast imaging: an evaluation of clinical potential.

The conspicuity of a variety of human tumors outside the liver, with a broad spectrum of histologic types, was evaluated using phase-contrast imaging (proton chemical shift imaging, proton spectroscopy) and the results compared with the data obtained using routine T1- and T2-weighted magnetic resonance (MR) imaging sequences. In all cases, tumors were most conspicuous using the phase-contrast technique. In two instances, the tumors could be discerned only by this method, being undetectable by any routine MR pulse sequence. The use of phase-contrast imaging is recommended as an adjunct to standard MR sequences when evaluating for either the presence or extent of a tumor, regardless of its anatomic location or histologic type.

Respiration artifacts in MR imaging: reduction by breath holding.

Respiratory motion commonly produces degradation of image quality on magnetic resonance scans of the upper abdomen due to artifacts produced in the direction of the phase encoding gradient. Such artifacts may be reduced, although not eliminated, on image sequences obtained with relatively short acquisition times by means of breath holding during the middle 20% of the sequence.

Quantitation of the prominent medullary pyramid: a reappraisal.

We propose a revised objective measurement of the size of the renal medullary pyramid in the assessment of the prominent renal pyramid: the medullary-renal ratio (MRR). (Formula: see text). This is a more accurate assessment of the size of the renal pyramid relative to the size of the kidney than the previously proposed medullary pyramid index, which fails to take into account the varying morphology of otherwise normal kidneys.

Efficacy of abdominal computed tomography in evaluation of possible abdominal abscess.

A retrospective analysis was made of all abdominal computed tomography scans performed because of clinical suspicion of an abscess at our institution over a 12-month period. Of 130 patients examined, 45 patients had had abdominal surgery within the previous 2-week period. Of these patients, 14 were found to have abscesses on computed tomography, with three known false-negative studies. An additional nine patients had sterile postoperative collections. Nine patients had had an abdominal abscess previously diagnosed, and five of these had a residual abscess. A total of seven abscesses were found by computed tomography in 76 patients who had had no surgery in the previous 2 weeks, with one known false-negative study. High-risk categories of nonoperative patients were identified. Only one positive study occurred in a patient without a high clinical index of suspicion for an intraabdominal abscess, although a total of 50 patients fell into this low-risk, nonoperative category. The cost-effectiveness of computed tomography studies in such low-risk patients is questioned.

Lower lobe collapse due to pleural effusion: a CT analysis.

In the presence of a pleural effusion, volume loss is seen in the adjacent lung, primarily in the lower lobe. With a modest effusion a compliant lower lobe may show displacement and generalized volume loss without focal atelectasis, but more commonly segmental atelectasis does occur, typically in the posterior basal segment. Large effusions result in a major degree of lower lobe collapse. The collapsed lobe tends to be uplifted by the fluid and compressed toward the hilum with consequent stretching and attenuation of the inferior pulmonary ligament, rather than collapsing posteriorly and medially.

Sonography of experimental acute renal vein occlusion.

Complete occlusion of the renal vein in five rabbits with the kidney in its normal position was followed by high-resolution ultrasound. Early changes consisted of moderate renal enlargement and a diffuse increase in renal echogenicity with a fine echo pattern. On the average, renal length increased by only 13%. Delayed changes were a gradual reduction in renal echogenicity, falling to below baseline, with blurring of the corticomedullary boundary. Intrarenal hemorrhage alone occurred in only one kidney. Perirenal hematoma were seen in two other cases associated with localized intrarenal hemorrhage adjacent to the point of capsular rupture (overall renal morphology was preserved). The relative subtlety of the changes observed contrasts with previously reported data and is felt to preclude a specific diagnosis.

The sonographic evaluation of hydronephrosis with progressive ureteric obstruction. An experimental model.

An experimental animal model was set up to examine the interrelationship between urine flow and progressive ureteric stenosis in producing sonographically detectable hydronephrosis. In four rabbits with mild ureteric stenosis or no stenosis the renal pelvis showed little distension even with rapid diuresis. Progressively tighter ureteric stenoses resulted in progressive renal pelvic distension accentuated by diuresis. The implication is that the normal, unobstructed ureter in the rabbit is able to remove urine from the kidney as fast as it may be produced, even during conditions of maximal diuresis. Therefore, in the absence of any other factor that may contribute to overdistension of the upper urinary tract, a state of diuresis will not simulate hydronephrosis.

Plexiform neurofibroma of the pelvis in neurofibromatosis: CT findings.

Three cases of intrapelvic plexiform neurofibromas are presented in patients with neurofibromatosis. In all three cases computed tomography demonstrated widespread sheets of nodular tissue lying in an extraperitoneal location in front of the sacrum or extending along the pelvic sidewalls . Symptomatology in these patients related to compression of either nerve roots or adjacent vessels. It is important to differentiate these lesions from pelvic lymphadenopathy to prevent a mistaken diagnosis of malignant disease.

Computed tomography of mural thrombosis in the hypereosinophilic syndrome.

The hypereosinophilic syndrome characteristically involves multiple organs. Its most severe debilities are associated with cardiac and central nervous system complications. Endothelial damage can result in intracardiac thrombosis, endocardial fibrosis, and progressive congestive failure. Computerized tomography is of value in making the diagnosis of an intracardiac mass. Simultaneous evaluation of the pericardiac and extracardiac structures may aide in the distinction of a thrombus from a neoplasm.

The renal parenchymal stone: a benign calcified renal mass.

Five patients are described, each with a densely calcified solitary mass in a peripheral location in the kidney. There was exophytic projection of the calcification in 4 cases. Three lesions were so completely calcified as to be regarded as stones. The bulk of the lesion was calcified in the 2 other cases, in which the noncalcified portion was either avascular or hypovascular. In no case was there evidence of a soft-tissue mass extending beyond the confines of the calcification. Pathologic correlation in 1 case showed only calcification in association with some renal scarring, and in a second case demonstrated an old organized and calcified abscess. Long-term follow-up in the other 3 cases has demonstrated complete stability without evidence of tumor. All cases are believed to represent examples of calcified renal parenchymal scars, resulting from old granulomatous disease, renal abscess, or hematoma. We propose that these lesions be regarded as solitary renal parenchymal stones without malignant potential, rather than calcified masses. The significance of the findings for patient management are discussed.