Defective platelet-fibrinogen interaction in hereditary canine thrombopathia.

A unique, intrinsic, hereditary canine platelet disorder attributable to abnormal fibrinogen receptor availability is described. Thrombopathic platelets from 13 severely affected basset hounds failed to aggregate in response to all agonists tested except thrombin. Normal platelet interaction with the various stimuli was inferred on the basis of their ability to elicit unimpaired shape change in thrombopathic platelets. No quantitative differences in major platelet membrane glycoproteins, intraplatelet fibrinogen, adenine nucleotides, or serotonin uptake were detected. Dense granule secretion was impaired. The ultrastructural appearance of thrombopathic platelets was normal. Fibrinogen-platelet interaction was evaluated by reacting platelet-rich plasma (PRP) with fibrinogen coupled to polymeric acrylonitrile beads and scoring the extent of stimulus-induced agglutination. The aggregatory responses of normal and thrombopathic platelets were closely correlated with fibrinogen receptor availability. In contrast to human platelets, epinephrine-stimulated canine platelets did not interact with immobilized fibrinogen, and arachidonate generally induced only weak agglutination. Thrombopathic platelets agglutinated fibrinogen beads at reduced rates when stimulated with physiologic doses of thrombin and high-dose calcium ionophore, A23187. Our data suggest that thrombin-mediated induction of canine platelet fibrinogen receptors may proceed by pathway(s) alternate to those shared by other platelet agonists, and/or that secreted granule constituents may act synergistically with thrombin to overcome inhibition of signal-response-coupled reactions mediating the interaction of fibrinogen with its receptor. This congenital platelet defect provides further evidence, in a species other than human, for the pivotal role of fibrinogen receptor induction in platelet aggregation.

Platelet and fibrinogen kinetics in healthy and African swine fever-affected swine: [75Se]selenomethionine-labeling study.

Platelet and fibrinogen survival times were determined in healthy pigs and in pigs infected with African swine fever (ASF) virus. Cohort labeling with [75Se]selenomethionine was performed. The platelet survival time in healthy pigs was 5.3 +/- 0.7 days, and the fibrinogen survival time was 6.7 +/- 0.8 days. Early deaths and profound thrombocytopenia prevented calculation of accurate platelet and fibrinogen survival times in ASF virus-infected animals. The ASF virus-infected pigs died of extensive hemorrhage and effusions while thrombocytopenic; however, there was normal thrombocytopoiesis during infection, as measured by incorporation of the radionuclide into platelets. There was a slight decrease in plasma fibrinogen concentration when the platelet count decreased. A dysfunctional fibrinogen was present late in the infection.

The value of digital rectal examination before barium enema.

The authors recommend that the radiologist perform a digital examination of the rectum before barium enema. Rectal examination may disclose unsuspected lesions, facilitate tube insertion, indicate inadequate preparation of the colon, and aid in the decision of whether a rectal balloon is to be used.

Rectal balloon catheters and the barium enema examination.

Inflation of a rectal balloon during the barium enema examination has the potential for obscuring rectal lesions or causing rectal injury. The purpose of this communication is to emphasize a rationale for the radiologist that minimizes the use of rectal balloons and reduces the risk of rectal injury when inflation of a rectal balloon is necessary.

Predictability of rectal incontinence on barium enema examination.

The aim of this study was to determine if digital assessment of anal sphincter tone predicts whether a rectal balloon is needed to prevent incontinence during a barium enema examination. During an 8 month , 306 patients scheduled for barium enema examination were evaluated. Immediately before each examination as good, fair, or poor. The barium enema was then performed in a conventional manner. Leakage of even small amounts of barium was scored as rectal incontinence. Ability to retain the barium enema correlated closely with the strength of rectal bone, regardless of patient sex or age. For different sphincter tones the incidence of rectal incontinence was: good, 2%, fair, 30%; and poor, 90%. From these findings it is recommended that, irrespective of patient age and sex, the use of rectal balloon catheters be limited to patients with poor or fair rectal tone.

Rectal balloons: complications, causes, and recommendations.

Nine previously unreported rectal injuries caused by barium-enema examinations have been reviewed. In each case, the injury occurred in conjunction with inflation of a rectal balloon. Analysis of the clinical material suggested that certain mechanical properties of balloon catheter tips might transfer mechanical stress to the rectal wall and contribute to the observed injuries. Careful manometric evaluation of in vivo rectal balloons suggest that significant anatomic differences in patients may be clinically important. Further experimental bench studies revealed undesirable mechanical properties in many commercially available rectal balloon catheters. These mechanical problems include low compliance, asymmetrical inflation, strong lateral and anterior displacement of a firm catheter tip into the restraining wall, and self-obstruction of the balloon deflation outlet by the inflated baloon. Many of these problems were clinically confirmed by careful in vivo observations and by evidence collected from the nine cases of rectal injury. A series of practical prophylactic procedures are recommended.

An evaluation of colon cleansing regimens.

To study the efficacy of colon cleansing regimens, 500 hospital outpatients were randomly assigned to one of four regimens. Two featured castor oil followed by phosphate enema and two used magnesium citrate and bisacodyl. For the 349 patients who completed all components of the regimens, quality of the subsequent barium enema examination was scored by three radiologists in a blind manner. Regimens featuring magnesium citrate and bisacodyl were found to be significantly superior to those featuring castor oil. Calcium bisdiocytl sulfosuccinate did not improve the quality of colon cleansing but appeared to decrease the incidence of abdominal cramping in patients receiving magnesium citrate and bisacodyl. It is hoped that the investigative approach used in this study may serve as a model for future testing of colon cleansing regimens.