Normal and abnormal pancreas in children: US studies

The real-time ultrasound images of the pancreas in 273 children without pancreatic disease were prospectively analyzed to determine the normal appearance of the pancreas. The dimensions of the head, body, and tail of the pancreas were correlated with patient age, weight, height, and body surface area. Correlation between pancreatic dimensions and patient age was as good as or better than that obtained with the other physical parameters. In general, the normal pancreas had a similar sized head and tail with a thinner body as compared with the abnormal pancreas, and an echogenicity that was equal to or slightly greater than that of the liver. Analysis of the images of 13 patients with pancreatitis showed that the presence of a dilated main pancreatic duct was the most useful feature in suggesting an abnormality. Evaluation of pancreatic size, configuration, and echogenicity was not reliable in the differentiation of the normal from the abnormal pancreas.     

Cervical spinal fractures: CT detection

Although computed tomography (CT) is commonly used in addition to plain radiographs to evaluate cervical spinal fractures, it may fail to detect some clinically significant fractures. Cervical spinal fractures were produced in cadavers, studied with CT, and documented by cryomicrotomy. The CT scans were interpreted independent of the anatomic sections. Pedicle and lateral mass fractures were regularly unrecognized on CT scans. In these cases, widening and hemarthrosis of the adjacent facet joints were evident. A widened facet joint is an indirect sign of an occult cervical spinal fracture.     

Benign extraaxial tumors: contrast enhancement with Gd-DTPA

Meningiomas, acoustic neuromas, and other benign extraaxial tumors have little contrast with adjacent brain tissue on conventional magnetic resonance (MR) images. The contrast enhancement produced by intravenous administration of 0.1 mmol/kg of gadolinium-DTPA in these tumors was measured on T1 MR images. Acoustic neuromas showed the greatest enhancement (average, 310%), meningiomas the next greatest (average, 180%), and neurofibromas, glomus tumors, and pituitary microadenomas the least enhancement. The degree of enhancement was almost always greater at 3 minutes than at 25 or 55 minutes. Contrast between the tumor and adjacent tissue resulted from tumor enhancement in neuromas, meningiomas, and neurofibromas and from enhancement of the surrounding tissue in pituitary microadenomas.     

Quantitative US attenuation in normal liver and in patients with diffuse liver disease: importance of fat

Two methods are used to estimate ultrasound attenuation in liver. These were based on amplitude change and frequency change as a result of depth dependent attenuation. Evaluation of the two methods against a family of calibrated phantoms yielded correlation coefficients of 0.98 and 0.99, respectively. Liver attenuation in 26 control subjects was 0.50 and 0.52 dB/MHz/cm, respectively. Liver attenuation was estimated in 50 patients who later underwent liver biopsy. Comparison with quantitative histologic results showed that the presence of fat alone accounted for the increased attenuation associated with cirrhosis. Similar high attenuation values were found in patients with fatty infiltration. Fibrosis alone did not result in elevated liver attenuation. Cirrhotics without fatty infiltration had attenuation similar to that of the controls. Mechanisms of action are discussed.     

Rectal guiding tube to facilitate distal colonic stent insertion

Self‐expanding metallic stents for the treatment of acute colonic obstruction is a recent technique showing promising results. Traditionally metallic stents have used a colonoscope as the portal for stent insertion. Our rectal guiding tube has been devised to enable continuous opacification of the colon without contrast or colonic content leakage and provide a rigid portal through which to insert the metallic stent safely. In many situations concomitant use of a colonoscope is not necessary, especially in left‐sided or more distal colonic lesions.     

Role of human hepatic cytochrome P450 1A2 and 3A4 in the metabolic activation of estrone

The metabolic activation of estrone (E1), a potent estrogen was investigated using recombinant human cytochrome P450 enzymes, 1A2, 2B6, 2C8, 2C9, 2C9R144C, 2E1, 3A4, 3A5 and liver microsomes from 14 human organ donors. At least five products of E1 were detected and quantitated by HPLC and gas chromatography-mass spectrometry (GC-MS). Among these metabolites, 16alpha-OH-E1, 2-OH-E1 and 4-OH-E1, which are believed to be associated with estrogen carcinogenesis in animals, were definitively identified. Of all P450s examined, 1A2 and 3A4 exhibited the highest activities with turnovers of 3.4 and 2.5 nmol/min/nmol P450 for the total metabolism of E1, respectively, while 3A5, 2C9 and 2C9R144C showed moderate activities. 2B6, 2E1 and 2C8 did not produce any significant amount of products. 1A2 formed almost exclusively the 2- OH-E1 at a rate of 3.3 nmol/min/nmol but 3A4 preferentially formed the metabolite X1 (an unknown hydroxylation product) and 16alpha-OH-E1. Kinetic characterization showed that the Km values of 1A2, 3A4 and 3A5 were 14, 95 and 64 microM and Vmax were 5.43, 0.68 and 0.35 min(-1), respectively. All human liver microsomes were capable of metabolizing estrone and a 4-fold variation was seen between individuals. The relative amount of metabolites formed was generally 2-OH-E1 > metabolite X1 > 4-OH-E1 > 16alpha-OH-E1 > metabolite X2. 3A4/5 enzyme complex was assessed by inhibitory monoclonal antibody specific for 3A4/5 to contribute 60-88% to the formation of individual metabolites in human liver except for 2-OH-E1 (3%). The formation of 2-OH-E1 and 16alpha-OH-E1 by 14 human liver microsomes was significantly correlated with caffeine 3-demethylation supported by 1A2 (r2 = 0.87) and with testosterone 6beta-hydroxylation by 3A4 (r2 = 0.66), respectively. Thus the metabolic patterns exhibited by human liver are likely due to the combined activities of the P450 1A2 and 3A4 enzymes.