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Biomedical subjects

W D Evans

Publications and source records attributed to W D Evans.

At least 37 records · Page 2Linked to original sources
PubMed1997

Does vasectomy predispose to osteoporosis?

OBJECTIVE: To investigate whether vasectomy, which causes immunological and histological changes to the testes and changes to the hypothalamo-pituitary axis, could influence bone mineral density (BMD) and predispose to osteoporosis. PATIENTS AND METHODS: From patients referred to the Bone Densitometry Clinic, the BMD of L1-L4 and of the hip was analysed in 25 vasectomized men and compared with that in age-matched controls, ensuring that both groups had no secondary causes which might predispose to osteoporosis. RESULTS: In the spine, the mean (standard deviation) BMD was 1.00 (0.19) g/cm2 for the vasectomized men and 0.96 (0.14) g/cm2 for the controls. In the hip (femoral neck and total, respectively) the means were 0.79 g/cm2 and 0.90 g/cm2 for the vasectomized men and 0.72 g/cm2 and 0.96 g/cm2 for the controls. None of the differences were statistically significant. CONCLUSION: This study does not support the hypothesis that vasectomy may be a risk factor for osteoporosis.

Adult↗
PubMed1997

Inflammatory bowel disease and predisposition to osteopenia.

The prevalence of osteopenia in children with inflammatory bowel disease (IBD) is unknown. The effect of nutritional state, disease activity, and steroid therapy on bone mineral content (BMC) of whole body, lumbar spine, and left femoral neck measured by dual energy x ray absorptiometry in 32 children with IBD was assessed by comparison with 58 healthy local school children. Using the control data, a predicted BMC was calculated taking into account bone area, age, height, weight, and pubertal stage. The measured BMC in children with IBD was expressed as a percentage of this predicted value (% BMC). Mean (SD) % BMC was significantly reduced for the whole body and left femoral neck in the children with IBD (97.0 (4.5)% and 93.1 (12.0)% respectively, p < 0.05). Of the children with IBD, 41% had a % BMC less than 1 SD below the mean for the whole body and 47% at the femoral neck. Reduction in % BMC was associated with steroid usage but not with the magnitude of steroid dose, disease activity, or biochemical markers of bone metabolism. In conclusion, osteopenia is relatively common in childhood IBD and may be partly related to the previous use of steroids.

Adolescent↗
PubMed1996

Impaired matching of perfusion and ventilation in heart failure detected by 133xenon.

In severe chronic heart failure (CHF) the ventilatory cost of CO2 elimination during exercise (VE/VCO2) is increased, suggesting ventilation/perfusion (V/Q) mismatch. The relationship of exercise VE/VCO2 regression slope m to deadspace ventilation was studied in 15 patients with CHF who underwent cardiopulmonary exercise testing and arterial blood gas monitoring. Regional lung ventilation and perfusion was studied, using 133xenon, at rest and peak exercise in a further group of 10 CHF patients and in five normal subjects. VE/VCO2 slope m correlated well with deadspace ventilation at peak exercise in the 15 patients with CHF. We therefore used exercise VE/VCO2 slope m to categorize CHF patients undergoing 133xenon imaging into groups with increased (slope m > 36) or normal (slope m < 36) exercise deadspace ventilation. In normals, resting V/Q determined by 133xenon showed a gravitational gradient, which improved on exercise as a result of relative increases and of relative reductions in regional perfusion; no significant changes in regional ventilation distribution were detected. In patients with CHF who had normal slope m (n = 5), rest and exercise V/Q were similar to the normal subjects. In CHF patients with increased slope m (n = 5) however, the resting gravitational gradient of V/Q was lost, and there were no significant changes in relative perfusion distribution on exercise. These findings suggest that the increased ventilatory cost of CO2 elimination found in certain patients with CHF is related to inability to coordinate and optimise the relative distribution of lung perfusion with respect to ventilation during exercise.

Adult↗
PubMed1996

Iron absorption from a natural mineral water (Spatone Iron-Plus).

Spatone Iron-Plus is a naturally occurring mineral water from Trefriw Wells Spa in Gwynedd, Wales, UK which contains approximately 0.3 mg of iron per ml as ferrous sulphate. The water has been taken as a tonic since Victorian times. Iron absorption from Spatone Iron-Plus was measured in a whole body counter after labelling the water with [59Fe] ferrous sulphate. Absorption studies were carried out in 13 subjects. Mean absorption for 10 ml of Spatone Iron-Plus taken on an empty stomach was 23 percent. Absorption was related to body iron stores as assessed by serum ferritin. In subjects with a serum ferritin concentration of <10 mu g/I, absorption was approximately 40 percent but was <10 percent in subjects with ferritin concentrations of approximately 200 mu g/I. This study indicates that Spatone Iron-Plus provides iron in a highly bio-available form.

Adult↗
PubMed1995

Factors affecting the in vivo precision of broad-band ultrasonic attenuation.

The in vivo precision of broad-band ultrasonic attenuation (BUA) was measured in one normal male volunteer over periods of one day and six weeks and in a group of 10 volunteers over a period of two weeks using a Walker Sonix UBA 1001 bone mineral analyser in which the foot is immersed in a water tank. Coefficients of variation ranged from 1-3% and, in general, there was no difference in BUA variance between right and left feet. However, right foot BUA values were consistently greater than those of the left, but there was no difference between mediolateral and lateromedial transmission. The use of preboiled water improved precision and reduced measurement time. In addition, factors affecting BUA precision were investigated in the individual volunteer. Equipment stability and conditions of immersion (immersion time, water depth, water temperature and concentration of a detergent wetting agent) had comparatively little effect on BUA values. On the other hand, the effects of foot positioning were more pronounced: rotation about the long axis of the foot, translation across the water tank and foot movement in the dorsal-plantar direction each contributed a maximum of 1.5-2.0% variation in BUA. However, both rotation about the long axis of the leg and foot movement in the heel-toe direction could change BUA by as much as 9%. It is likely that foot positioning will limit the precision achievable with this technique.

Adult↗
PubMed1995

Bile acid dysfunction after clam enterocystoplasty.

OBJECTIVE: To determine if the bowel dysfunction that develops in approximately 12% of patients after a clam enterocystoplasty is due to disruption of the enterohepatic circulation of bile acids. PATIENTS AND METHODS: Fourteen symptomatic patients (mean age 36 years, range 21-65) who had undergone clam enterocystoplasty were investigated by bowel frequency charts, hydrogen breath tests of expired air and the retention of radioactive 75Se-labelled homocholic acid-taurine (SeHCAT), a synthetic bile acid. Patients with abnormal results were commenced on anion-exchange resins and the symptoms evaluated 6 weeks later. RESULTS: The interruption of bile acid circulation, as estimated by SeHCAT, occurred in most of the patients studied and was due to surgical resection of the terminal ileum. All hydrogen breath tests were normal, excluding bacterial overgrowth as a cause of diarrhoea. Bowel frequency correlated well with the percentage of SeHCAT retained. Anion-exchange resins were successful in relieving the symptoms if patients complied well with the treatment. CONCLUSIONS: After clam enterocystoplasty, some patients have bowel dysfunction caused by the interruption of the enterohepatic circulation of bile acids. These patients can be identified using bowel frequency charts and treated by anion-exchange resins.

Adult↗
PubMed1995

The validity of estimating total body fat and fat-free mass from skinfold thickness in adults with growth hormone deficiency.

The regression equations of Durnin and Womersley for estimating total body fat (TBF) and fat-free mass (FFM) from skinfold thickness were validated for adult GH-deficient (GHD) patients by comparing the values of TBF and FFM from the prediction equations with the directly measured values from dual energy x-ray absorptiometry. Twenty-seven male and 24 female patients (aged 21-61 yr) were studied. GHD was isolated in 5 cases and was part of a spectrum of hypopituitarism due to a variety of causes in 46 cases. The mean period of GHD was 6.9 +/- 4.6 yr. All patients were receiving stable replacement therapy. The validation statistics showed no significant differences (P > 0.05) between measured and predicted values of TBF and FFM in either males (24.5 vs. 24.9 and 65.5 vs. 65.8 kg) or females (24.6 vs. 26.3 and 44.7 vs. 43.9 kg). Mean differences were smaller in males (0.4 and 0.2 kg) than females (1.7 and -0.8 kg); they were less than 1% in males and less than 2% in females. Therefore, the Durnin and Womersley equations are suitable for general use with GHD patients. Using TBF (kilograms) from dual energy x-ray absorptiometry as the dependent variable and the log of the sum of skinfold thickness as the independent variable, linear regression equations were formulated to predict TBF in GHD patients. The lowest SE of estimate was 3.8 kg in males and 4.6 kg in females. To determine their general applicability, these equations will need to be cross-validated.

Absorptiometry, Photon↗
PubMed1994

Measurement of height: practical considerations for the study of osteoporosis.

Osteoporotic vertebral fractures result in loss of height and so regular measurement of stature may be a useful method for detecting the onset of the disease and monitoring its progress. The aim of this study was to evaluate the reliability of height measurement in a clinical setting by estimating its precision and the effects of diurnal variation and supine bone densitometry. Duplicate measurements of standing height were made in 50 normal volunteers (25 female) in the morning and 7h later; similar measurements were made in 25 female patients before and after densitometry (spine, one hip and whole body). Portable Harpenden stadiometers were used. The pooled standard deviation (coefficient of variation) ranged from 0.9 mm (0.05%) to 1.7 mm (0.11%). Significant height decrease (> 6 mm) occurred in volunteers during the course of a day while patients showed a significant increase (> 5 mm) after lying supine for an average period of 49 min. Height can be estimated precisely if measurements are made consistently, i.e. using the same equipment and technique, at the same time of day and before bone densitometry. The provision of stadiometers in primary care surgeries and hospital clinics would provide a simple, inexpensive and non-invasive method of assessing the progress of spinal osteoporosis.

Absorptiometry, Photon↗
PubMed1994

The effect of oestradiol implants on regional and total bone mass: a three-year longitudinal study.

OBJECTIVE: Although there is evidence from cross-sectional studies that percutaneous oestrogen administration protects against menopausal bone loss, few longitudinal data are available. We have examined the effect of 3 years' treatment with percutaneous oestradiol on total body calcium, spinal trabecular bone mineral density and radial bone mineral content in post-menopausal women. DESIGN AND PATIENTS: Twenty-nine post-menopausal women, aged 37-55 years, who had undergone hysterectomy and had experienced the onset of menopausal symptoms within the previous 2 years, were studied before and for 3 years during hormone replacement with oestradiol implants, given at approximately 6-monthly intervals. MEASUREMENTS: Total body calcium was measured by prompt gamma neutron activation analysis, spinal trabecular bone mineral density by quantitative computed tomography and radial bone mineral content by single-photon absorptiometry. RESULTS: There was a significant increase in the mean total body calcium, spinal trabecular bone mineral density and radial bone mineral content over the 3 years of the study. The mean (+/- SEM) percentage change per annum was +2.4% (+/- 0.8) for total body calcium (P < 0.01), +3.3% (+/- 0.6) for spinal trabecular bone mineral density (P < 0.001) and +1.2% (+/- 0.6) for radial bone mineral content (P < 0.05). CONCLUSIONS: Percutaneous oestradiol replacement therapy prevents menopausal bone loss and is associated with a sustained and significant increase in total body calcium, spinal trabecular bone mineral density and radial bone mineral content over a 3-year treatment period. Oestradiol implants thus have skeletal effects comparable to those of oral or transdermal oestrogens.

Administration, Cutaneous↗
PubMed1993

A four-year longitudinal study of bone loss in patients with inflammatory bowel disease.

Serial measurements of spinal trabecular and radial cortical bone density were made over 4 years in 70 patients with inflammatory bowel disease. Mean rates of bone loss for the cohort differed little from rates reported in normal populations; however, some patients showed increased rates of loss, including patients whose bone density at entry to the study was already well below normal. There was a significant correlation between the amount of corticosteroid prescribed and spinal trabecular bone loss in males, but no significant correlation with other clinical parameters. Increased rates of bone loss emphasise the need for bone densitometry and prophylactic measures in patients with inflammatory bowel disease.

Adult↗
PubMed1993

Hormone replacement therapy prevents bone loss in patients with inflammatory bowel disease.

Patients with inflammatory bowel disease have an increased prevalence of osteoporosis, and suffer high rates of spinal bone loss. Hormone replacement therapy (HRT) is effective in the treatment and prevention of osteoporosis but has not been studied in patients with inflammatory bowel disease. A two year prospective study of HRT in inflammatory bowel disease was performed in 47 postmenopausal women aged 44 to 67 years with ulcerative colitis (25) or Crohn's disease (22). Patients had radial and spinal bone density measured annually by single photon absorptiometry and quantitative computed tomography respectively. The mean (95% confidence intervals) annual change in radial bone density was +1.42%/yr (+0.58 to +2.26; P < 0.005) and for spinal bone +2.60%/yr (+1.06 to +4.15; p < 0.005). There was no significant correlation between rates of change of bone density at the two sites, or between the rates of change and the initial bone density either in the radius or spine. Twelve patients were given prednisolone during the study, and their rates of change for spinal bone density were lower, but values were not statistically significantly different from those who did not receive corticosteroids. Changes in bone density for patients with ulcerative colitis and Crohn's disease were not significantly different. The change in bone density did not correlate with the patients' age or number of years after the menopause. It is concluded that HRT is effective in prevention of bone loss in postmenopausal women with inflammatory bowel disease.

Adult↗
PubMed1993

Bone loss in normal British women; a 5 year follow-up.

To assess the rates of loss, forearm and spinal bone mineral were remeasured in 16 out of 18 peri- and post-menopausal women aged 45 to 60 years who had taken part in a previously reported cross-sectional study. The mean interval between measurements was 4.8 years (range 4.2-5.3 years). The mean (95% confidence interval (CI)) annual change in radial bone mineral density was -0.78%/year (-1.73 to +0.18%; not significant) and in spinal bone mineral -2.41%/year (-3.55 to 1.27%; p < 0.001). There was considerable variation in the rate of change in radius and spine, and between individuals. There was no significant correlation between rates of bone loss at either site, or between rates of loss and the initial bone density at either the radius or spine. There was no significant correlation between the rates of change and the age or number of years post-menopause of the women. There was no significant change in the Z score for the forearm (mean -0.20; 95% CI -0.65 to +0.25) or for the spine (mean -0.04; 95% CI -0.30 to +0.22). There have been no previous longitudinal studies of the changes of bone density in normal British women. These results show considerable variation between individuals, and rates of change at one site cannot be predicted from measurements at another site. Untreated, some normal individuals have high rates of loss that cannot be predicted from baseline values, age or number of years post-menopause.

Absorptiometry, Photon↗
PubMed1992

Factors affecting bone density in young adults.

A 14-y follow-up of 581 children who took part in a randomized controlled trial of the effect of a milk supplement on growth of children was conducted to investigate the supplement's effect on adult bone mineral content (BMC) and density (BMD). BMC and BMD of the nondominant forearm were measured by single-photon absorptiometry in 371 subjects (64%) aged 20-23 y, at a proximal site (shaft of radius and ulna) and at a distal site near the wrist. BMCs and BMDs tended to be higher in the intervention group (NS). Cross-sectionally, BMD was positively associated with body weight (P less than 0.01) in both sexes; inversely associated with alcohol consumption (P less than 0.05), and positively with manual occupation (NS) in men; positively associated with current intakes of calcium (P less than 0.05), vitamin D (P less than 0.01), and sports activity during adolescence (P less than 0.01), and inversely with parity (NS) in women. In multiple linear-regression analysis body weight and sports activity during adolescence were stronger determinants of female BMD than was diet.

Adult↗
PubMed1992

Longitudinal study of cortical bone loss in patients with inflammatory bowel disease.

Bone mineral density of the radius was measured by single-photon absorptiometry in 50 patients with inflammatory bowel disease. Thirty-three had Crohn's disease and 17 ulcerative colitis; 25 were women. The mean age was 45 years (range, 18-70 years). Measurements were repeated in 39 of them after a mean follow-up period of 7.9 years (range, 7.1-8.2 years). In female patients the mean (95% confidence interval) annual change in radial bone mineral density was -0.74% (-1.34% to -0.14%) (P = 0.022), the greatest bone loss occurring in postmenopausal women (mean, -1.16% (-2.01% to -0.30%)). In male patients the mean annual rate of bone loss was -0.07% (-0.41% to 0.28%) (P = NS). Patients with abnormally low values at the first measurement remained osteopenic at the second measurement, whilst some others with normal values initially showed increased rates of bone loss and had a subnormal bone mineral density after the follow-up period. These results show increased rates of cortical bone loss in some patients with inflammatory bowel disease and emphasize the need to monitor bone mass in these patients so that prophylactic measures can be instituted.

Absorptiometry, Photon↗
PubMed1991

Total body calcium in patients with inflammatory bowel disease: a longitudinal study.

1. Serial measurements of total body calcium have been made by prompt gamma-neutron activation analysis in 13 patients with inflammatory bowel disease over a mean period of 23 months. Changes in spinal trabecular bone mineral density and radial shaft bone mineral content were also assessed by using quantitative computed tomography and single photon absorptiometry, respectively. 2. The mean annual decreases (95% confidence intervals) were: total body calcium, 7.8% (-12.0 to -3.7%; P less than 0.001); spinal trabecular bone mineral density, 2.5% (-5.0 to +0.1%; 0.05 less than P less than 0.1), radial bone mineral content, 2.1% (-3.4 to -0.8%; P less than 0.01). 3. No significant correlations were found between rates of change of the three variables. However, there were significant positive correlations between the baseline values for total body calcium and radial bone mineral content (r = 0.638, P less than 0.05), spinal bone mineral density and radial bone mineral content (r = 0.854, P less than 0.01), and total body calcium and spinal bone mineral density (r = 0.876, P less than 0.001). 4. These results demonstrate rapid decreases in total body calcium in patients with inflammatory bowel disease which, in conjunction with the significant decrease in radial shaft bone mineral content, indicate increased rates of cortical bone loss. Whilst values for bone mass at different skeletal sites showed positive correlations within individuals, no relationship was found between the rates of change in bone mass at these sites. 5. The rapid bone loss observed in some subjects emphasizes the importance of early detection of osteoporosis by bone densitometry and the need for effective prophylactic measures to be established in this group of patients.

Absorptiometry, Photon↗