Hepatic hemangiomas vs metastases: MR differentiation at 1.5 T

We retrospectively studied the value of MR imaging at 1.5 T in distinguishing hepatic hemangiomas (n = 15) from metastases (n = 15) by using (1) lesion/liver signal-intensity ratios, (2) contrast/noise ratios, and (3) T2 relaxation time on long TR/TE spin-echo (SE) sequences. Lesion/liver margin sharpness, lesion shape, and overall lesion morphologic pattern were evaluated also. Univariate logistic regression analysis of the quantitative data showed that T2 was the only statistically significant (p less than .02) variable for distinguishing a hemangioma from a metastasis. A receiver-operator-characteristic plot of T2 produced an area of 0.80 (+/- 0.08). T2 values for these lesions still overlapped with those for metastases. Morphologically, hemangiomas were sharply marginated (80%), rounded or oval (93%), homogeneous, hyperintense lesions (73%), whereas metastases were poorly marginated (66%) and inhomogenous (67%) lesions. The marked, hyperintense appearance was present in 27% of metastases. Retrospective, multivariate logistic regression analysis of T2 and the presence of hyperintense morphology did not improve results based on T2 alone. Morphologic criteria are helpful in differentiation, as some metastases have a prolonged T2 and are not homogenous, hyperintense lesions. In cases where T2 or morphology are equivocal, other diagnostic tests may help confirm the MR findings. We currently use a T2 of greater than 88 msec and the presence of hyperintense morphology to diagnose hemangiomas. Despite both quantitative and qualitative analysis, data for these hemangiomas and metastases still overlap.

Extravasation of nonionic radiologic contrast media: efficacy of conservative treatment

The authors report four large-volume (greater than 20-mL) extravasations in adults and one intermediate-volume (18-mL) extravasation in an infant of iopamidol, a nonionic contrast medium, that occurred during dynamic enhanced computed tomography. The largest volume that extravasated (in two patients) was 150 mL. Although all five patients initially had swelling, erythema, and/or pain after extravasation, all recovered uneventfully. The authors suggest that emergent surgical drainage of all large-volume extravasations, a procedure that was recently recommended, is unnecessary. Large extravascular collections of nonionic contrast media can be well tolerated and are often resorbed without adverse sequelae.

Primary peritoneal neuroblastoma: computed tomography findings

Primary peritoneal tumors are rare neoplasms. The computed tomography findings in an adult patient with a primary peritoneal neuroblastoma are described. Discussion of these uncommon neoplasms and this unusual presentation of neuroblastoma forms the basis of this report.

A common ancestor for human placental 17 beta-hydroxysteroid dehydrogenase, Streptomyces coelicolor actIII protein, and Drosophila melanogaster alcohol dehydrogenase

A computer-based comparison of the amino acid sequences of human placental 17 beta-hydroxysteroid dehydrogenase and Streptomyces coelicolor actIII protein, which is important in the synthesis of the antibiotic actinorhodin, gives an alignment score 12.15 standard deviations higher than that of 1000 comparisons of randomized sequences of these proteins. The probability of getting this score by chance is 3 x 10(-34). Comparison of actIII protein with Drosophila melanogaster alcohol dehydrogenase yields a score of 10.3 standard deviations (P = 3.5 x 10(-25)). Based on these similarities, we propose that 17 beta-hydroxysteroid dehydrogenase, actIII protein, and Drosophila alcohol dehydrogenase are derived from a common ancestor.

Dynamic, incremental computed tomography using a high heat capacity tube, solid-state detector, and automated injector. Potential in body imaging

Using a new graphite tube, a prototype solid scintillating detector, and an automated injector, improvements were made in body computed tomography image quality. First, more scans with shorter interscan delay could be obtained with the improved tube. Second, liver image quality was improved with the use of higher techniques and a more consistent contrast bolus delivery with a mechanical injector. Last, body surveys were improved because the higher heat capacity tube provided the ability to rapidly scan and examine an entire region during the injection of contrast.

MR evaluation of adrenal masses at 1.5 T

We retrospectively studied the value of MR imaging at 1.5 T to distinguish between nonadenomatous (n = 17) and adenomatous (n = 15) adrenal masses on the basis of (1) signal-intensity ratios on T1- and T2-weighted spin-echo images, (2) T2 relaxation times, and (3) T2 relaxation-time ratios. Univariate and then multivariate logistic regression were applied to these quantitative parameters to determine which of these best discriminated nonadenomas from adenomas, and whether or not more than one of these parameters improved the prediction. The adrenal mass/liver signal-intensity ratio on T2-weighted spin-echo images could not be used to differentiate nonadenomas from adenomas. Adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images, adrenal/liver T2 relaxation-time ratios, and adrenal mass T2 relaxation times were best for distinguishing nonadenomas from adenomas. By using a T2 value of greater than 61 msec, the true-positive ratio/false-positive ratio of differentiating nonadenomas from adenomas was 100%/20%; at greater than 82 msec, it was 64%/0.06%. The adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images and the adrenal/liver T2 relaxation-time ratios showed similar inherent discriminatory capacity. Overlap remains despite the use of these parameters. On the basis of this preliminary information, we conclude that MR has merit for the characterization of adrenal masses at 1.5 T. T2 relaxation time of the adrenal mass shows the greatest promise for discriminating nonadenomas from adenomas.

Similarity between tyrosyl-tRNA synthetase and the estrogen receptor

Residues 1-42 of Escherichia coli tyrosyl-tRNA synthetase are similar to residues 293-334 of the human estrogen receptor. A computer analysis yields a comparison score that is 8.2 standard deviations higher than that obtained with 10,000 comparisons of randomized sequences of these segments (P = 1.2 X 10(-16). This part of tyrosyl-tRNA synthetase binds ATP, which suggests that residues 293-334 of the human estrogen receptor are part of an ATP binding site.

Pulmonary septic emboli mimicking metastatic rhabdomyosarcoma

Central venous catheters have proven to be an important aid for the care of pediatric patients with malignancies receiving chemotherapy. A rare complication of such catheters is pulmonary septic emboli. This report describes a 15-year-old white girl with rhabdomyosarcoma who developed pulmonary nodules while on chemotherapy. These lesions appeared to be metastatic rhabdomyosarcoma. However, an excisional biopsy showed the lesions to be septic emboli. The patient was placed on antibiotic therapy and responded well. She was able to continue with her "front-line" therapy because the nodules were confirmed not to be metastatic disease.

Human placental 17 beta-hydroxysteroid dehydrogenase is homologous to NodG protein of Rhizobium meliloti

The amino acid sequence of human placental 17 beta-hydroxysteroid dehydrogenase (17 beta-OH-steroid dehydrogenase) was found to be similar to that of the NodG protein of Rhizobium meliloti. The computer-based comparison score is 11.5 SD higher than that obtained with 2500 comparisons of randomized sequences of these proteins. The probability of getting such a score by chance is 6 x 10(-31). 17 beta-OH-steroid dehydrogenase is also similar to Klebsiella aerogenes ribitol dehydrogenase and Escherichia coli glucitol-6-phosphate dehydrogenase. We propose that the steroid recognition site on 17 beta-OH-steroid dehydrogenase evolved from an ancestral recognition site for polyols such as ribitol and glucitol-6-phosphate.

Location of enzymatic and DNA-binding domains on E. coli protease La

Escherichia coli protease La is an ATP-dependent enzyme that has a DNA-binding site. The locations of the enzymatic and DNA-binding sites are not known. We report that a 75-residue segment at the carboxy-terminus of the protease La is similar to part of Bacillus licheniformis beta-lactamase, a serine enzyme. The comparison score is 8.2 standard deviations higher than that obtained with 10,000 comparisons of randomized sequences of these segments. The probability of obtaining such a score by chance is 1.2 x 10(-16). We also find that a 107-residue segment in the amino-terminus half of protease La is similar to part of the sopB protein, a DNA-binding protein of the plasmid F of E. coli. The comparison score for these segments is 8 standard deviations (P = 6 x 10(-16)). These strong amino acid sequence similarities suggest the locations of the catalytic serine and the DNA-binding domains of protease La.

Similarity between phospholipase C and the regulatory domain of protein kinase C

We report that a 100 residue segment in the carboxy-terminus half of phosphatidylinositol-specific phospholipase C is similar to a segment in the amino-terminus half of protein kinase C. The computer-based comparison score is 9.5 standard deviations higher than that of 2500 comparisons of randomized sequences of these segments (P = 10(-21), suggesting that the two segments have similar biological properties. Phospholipase C has a segment that is homologous to part of the non-catalytic domain of src kinase and other tyrosine protein kinases. The similarity of phospholipase C with protein kinase C, a serine/threonine kinase suggests that novel exon shuffling occurred among serine/threonine and tyrosine kinases and phospholipase C.

Polar infarct in a transplanted kidney: cause of a pseudomass

Ultrasonography has become fairly standard for assessing common complications of renal transplantation such as hydronephrosis, urinomas, and lymphoceles. Infarctions are a less common complication that may occur in the setting of transplant rejection. We report a case in which an apparent solid mass on sonography proved to represent normal residual renal parenchyma in a kidney with a small shrunken lower pole due to infarction.

Is vitellogenin an ancestor of apolipoprotein B-100 of human low-density lipoprotein and human lipoprotein lipase?

Vitellogenin, an ancient animal protein, is the major yolk protein of eggs, where it is used as a food source during embryogenesis. Here it is shown that vitellogenins, including those from the invertebrates Caenorhabditis elegans and Drosophila melanogaster, contain domains that are homologous with parts of apolipoprotein B-100 (apoB-100) of human low-density lipoprotein and human lipoprotein lipase. As vitellogenins are likely to have been used by invertebrates during embryogenesis well before the circulation of lipids appeared in vertebrates, it is suggested that copies of a precursor gene, serving a function similar to vitellogenin, were modified to code for part of apoB-100 and lipoprotein lipase in vertebrates. In addition to providing a link between invertebrates and vertebrates for proteins involved in lipid transport, these homologies suggest new functions for vitellogenin other than being a yolk food for the developing embryo.

Computed tomography of the ileocecal region

The CT scans in 25 patients without ileocecal pathology and 52 patients with ileocecal abnormalities were retrospectively reviewed. The ileocecal region was identified in 18/25 (72%) of patients without pathology. Thirty of 52 patients with ileocecal pathology had inflammatory disease: Crohn's (13), appendicitis (9), abscess (6), and typhlitis (2). CT was complementary to barium studies, demonstrating wall thickening, pericolonic inflammatory change, masses, fascial thickening, and fistulae. Twenty patients had malignancy: primary carcinoma (9), metastases (7), and lymphoma (4). In all patients with carcinoma a mass was identified. Pericolonic stranding represented tumor extension in 5/6 patients. Metastases were identified as extrinsic ileocecal masses in all 7 patients. Liver, mesenteric and omental metastases were present in 8/20 patients. In patients with lymphoma there was wall thickening and two had additional pericecal lymphadenopathy. In 2 patients with hypoalbuminemia, findings included: wall thickening, mesenteric, and subcutaneous edema.

Computed tomography of primary retroperitoneal malignancies

The CT examinations and medical records of 33 patients with primary retroperitoneal malignancies were reviewed. Computed tomography findings were then compared with those from scans performed on 122 patients with non-Hodgkin lymphoma who presented during the same time interval. Primary retroperitoneal neoplasms had three distinct CT appearances. Twenty-one patients (64%) had large soft tissue masses. Seven patients (21%) had masses with fatty density components, and five patients (15%) had tumors that were primarily of water attenuation. With the exception of those liposarcomas that contained recognizable fat, CT could not distinguish among the different cell types. Seventeen patients with non-Hodgkin lymphoma had large dominant retroperitoneal soft tissue masses that resembled primary retroperitoneal malignancies. In most cases, however, CT was able to differentiate these tumor masses from primary retroperitoneal tumors. Although 19 of 20 sarcomas of soft tissue attenuation were heterogeneous, only six of the 17 lymphomas presenting as dominant masses had such an appearance. Computed tomography is extremely helpful in initially evaluating patients with primary retroperitoneal tumors and in assisting the surgeon in planning his or her approach by accurately defining tumor extent.

Hepatic adenoma: MR appearance mimicking focal nodular hyperplasia

A hepatic adenoma (HA) nearly isointense to normal liver on short and long repetition and echo time spin echo pulse sequences is presented. Contrary to previous expectations, the case shows that a single hepatic mass with these signal characteristics on magnetic resonance without a scar may represent either HA or focal nodular hyperplasia.

CT appearance of focal pseudomembranous colitis

Previous reports of the CT findings of pseudomembranous colitis (PMC) have demonstrated the diffuse form of the disease. Although the focal nature of PMC is well recognized in the gastrointestinal literature, this manifestation has not been stressed in CT reports. We present three cases of focal colonic thickening detected on CT that proved to be PMC.