Detailed per-oral small bowel examination vs. enteroclysis. Part II: Radiographic accuracy

Accuracy of the detailed per-oral small bowel series and enteroclysis was compared in 134 patients known to have (or not have) disease of the small bowel. Overall sensitivity of the per-oral examination was 92% and specificity 94%, compared to 94% and 89%, respectively, for enteroclysis. There was no difference between the two in Crohn disease, adhesions, and metastatic disease; however, enteroclysis was thought to be more effective in delineating peritoneal adhesions in patients with obstruction. The authors conclude that while the per-oral study and enteroclysis are equally valid methods of examining the small bowel, the per-oral study is preferable as a screening examination because it requires less time, has fewer side effects, and involves a lower radiation exposure.     

Multiphasic examinations of the stomach: efficacy of individual techniques and combinations of techniques in detecting 153 lesions

Multiphasic examinations of 153 gastric abnormalities observed radiologically and endoscopically were reviewed to determine the efficacy of four radiologic techniques and of several common combinations of these techniques for examining the stomach. There were 68 gastric ulcers, 12 ulcer scars, 44 cases of gastritis including 27 with erosions, 24 benign neoplasms, and five malignancies. Double-contrast, compression, mucosal relief, and full-column techniques detected 82%, 65%, 62%, and 51%, respectively, of all lesions diagnosed with the complete multiphasic examinations. Results indicate that the greater the number of techniques employed, the more accurate the examination, with biphasic and multiphasic examinations detecting 9%-18% more lesions overall than simple single- or double-contrast studies.     

Radiology and the Health Policy Agenda for the American People

Eleven radiologists appointed by the major radiological societies participated for the past 5 years in the development of the Health Policy Agenda for the American People. The Agenda is an action plan to address a wide variety of serious problems in medicine. The first phase involved establishment of 159 principles, broad value statements that were the foundation of the project. Phase 2 involved the development of policy proposals on 38 urgent issues for action in medical science; education; health resources; delivery mechanisms; evaluation, assessment, and control; and payment for services. These proposals are summarized in this report. The activities and recommendations of representatives for the field of radiology are described. The Agenda has been released, and an implementation phase has begun. It will likely be of great importance to the practice of radiology over the next decade. Important issues can be addressed by acting with the coalitions that are being formed from among the more than 150 participating organizations.     

Thrombosed synthetic hemodialysis access fistulas: failure of fibrinolytic therapy

Seven episodes of acute thrombosis occurring in five patients with polytetrafluoroethylene dialysis fistulas were treated with local infusions of low-dose streptokinase. Bleeding from previous dialysis puncture sites necessitated stopping the infusion in six out of seven patients, although in one of these six, the graft reopened. The seventh patient had never been dialyzed through the graft and thrombolysis was achieved without incident. Surgery was avoided in only one patient. The authors contend that in these patients the risks of fibrinolytic therapy outweigh the benefits. Surgical thrombectomy, coupled with intraoperative angiography and possible angioplasty, is the preferred method of treating these patients. Venography prior to the creation of the fistula helps the surgeon avoid diseased vessels and may avert early failure of the fistula.     

Effects on the buoyant density of rabbit platelets of ADP and agents that increase the concentration of cyclic AMP

Rabbit platelets were aggregated by adenosine diphosphate (ADP), allowed to deaggregate and then separated into density subpopulations by centrifugation through discontinuous Stractan density gradients. Although ADP causes little or no release of the contents of the amine storage granules of rabbit platelets, ADP caused a decrease in platelet density as compared with control platelets subjected to the same procedures except for exposure to ADP. The density change persisted for at least four hours. The apparent size of platelets stimulated with ADP increased initially, but returned to control values during a one-hour period. A similar decrease in platelet density was observed with an albumin density gradient. Under conditions in which aggregation did not occur in response to ADP with ethylenediaminetetraacetic acid (EDTA) in the medium, little or no decrease in platelet density was observed. Agglutination with polylysine did not change platelet density. Thus, not only agents such as thrombin and plasmin that cause the release of the contents of the platelet granules decrease platelet density, but ADP also has this effect. Platelets would be exposed to all of these stimuli during thromboembolic processes, and their effect on platelets may account for the decrease in platelet density observed previously in experiments with rabbits with indwelling aortic catheters. Agents that increase the concentration of cyclic AMP (cAMP) in platelets (PGE1, adenosine, dibutyryl cAMP, forskolin, and papaverine) also decreased platelet density. This effect persisted when the platelets were washed and resuspended in fresh medium and was also demonstrable in plasma. Platelet size was gradually increased by prostaglandin E1 (PGE1) which maintains platelets in a disc shape and does not cause the release of granule contents, indicating that the decrease in platelet density caused by PGE1 may be attributable to platelet swelling.     

The inhibitory effects of exogenous arachidonic acid on rabbit platelet aggregation and the release reaction

Although arachidonic acid causes rabbit platelet aggregation and the release of granule contents in suspensions of washed platelets when used in concentrations of approximately 50-300 microM, higher concentrations (500 microM) cause neither aggregation nor release. Suspensions of platelets from rabbits wee exposed to arachidonic acid (250 microM) for 15 min, allowed to recover in the presence of PGE1 for 30 min, washed, and resuspended; in some experiments, the platelets were treated with aspirin before being exposed to arachidonic acid. Aggregation of platelets pretreated with arachidonic acid was inhibited in response to ADP; this effect was greater with the non-aspirin- treated platelets and persisted for at least 4 hr after resuspension. The association of 125I-fibrinogen with the platelets as a result of ADP stimulation was also inhibited. Aggregation and release of granule contents in response to collagen and low concentrations of thrombin was inhibited, but the inhibition could be overcome by higher concentrations. Thrombin induced further release of granule contents from platelets exposed to arachidonic acid without pretreatment with aspirin. Platelets that had been exposed to arachidonic acid, either with or without pretreatment with aspirin, did not aggregate or undergo further release upon stimulation with arachidonic acid after they were washed and resuspended. Inhibition of the lipoxygenase pathway with eicosatetraynoic acid (ETYA) or nordihydroguaiaretic acid (NDGA) did not affect the inhibition caused by arachidonic acid, so it is unlikely that a product of this pathway is responsible for the inhibition. Mixing experiments indicated that the pretreated platelets did not form a thromboxane-A2-like activity, and that they were unresponsive to aggregation and release induced by products formed from arachidonic acid. Experiments with 3H-arachidonic acid showed that after 45 min of incubation with platelets, only 1.1% of the 3H-arachidonic acid remained as free arachidonic acid in the platelets. Although cyclic-AMP was slightly increased 1 min after the addition of arachidonic acid, the cyclic-AMP concentration was the same as that of control platelets after the platelets were washed and resuspended, indicating that increased cyclic-AMP is not likely to be responsible for the persistent inhibitory effect. Thus, the inhibitory effect of pretreatment with arachidonic acid is a general effect on responses to a variety of aggregating agents that act through different mechanisms, and the inhibition is not related to thromboxane-A2 formation. The possibility of membrane perturbation resulting in the unavailability of receptors may explain the persistent inhibitory effect, but the responsible reactions have not been identified.