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W J Walker

Publications and source records attributed to W J Walker.

At least 19 recordsLinked to original sources
PubMed2003

Estimation of effective vaccination rate: pertussis in New Zealand as a case study.

In some cases vaccination is unreliable. For example vaccination against pertussis has comparatively high level of primary and secondary failures. To evaluate efficiency of vaccination we introduce the idea of effective vaccination rate and suggest an approach to estimate it. We consider pertussis in New Zealand as a case study. The results indicate that the level of immunity failure for pertussis is considerably higher than was anticipated.

Child↗
PubMed2002

Uterine artery embolisation for symptomatic fibroids: clinical results in 400 women with imaging follow up.

OBJECTIVE: To evaluate the mid-term efficacy and complications of uterine artery embolisation in women with symptomatic fibroids. To assess reduction in uterine and dominant fibroid volumes using ultrasound and magnetic resonance imaging. DESIGN: Prospective observational single-centre study. SETTING: A district general hospital in Surrey and a private hospital in London. METHODS: Four hundred consecutive women were treated between December 1996 and February 2001. Indications for treatment were menorrhagia, menstrual pain, abdominal swelling or bloating and other pressure effects. Uterine artery embolisation was performed using polyvinyl alcohol particles and platinum coils. MAIN OUTCOME MEASURES: Imaging was performed before embolisation and at regular intervals thereafter. Clinical evaluation was made at regular intervals after embolisation to assess patient outcome. RESULTS: Bilateral uterine artery embolisation was achieved in 395 women, while 5 women had a unilateral procedure. With a mean clinical follow up of 16.7 months, menstrual bleeding was improved in 84% of women and menstrual pain was improved in 79%. Using ultrasound, the median uterine and dominant fibroid volumes before embolisation were 608 and 112 cc, respectively, and after embolisation 255 and 19 cc, respectively (P = .0001). Three (1%) infective complications requiring emergency hysterectomy occurred. Twenty-three (6%) patients had clinical failure or recurrence. Of these, nine (2%) had a hysterectomy. Twenty-six (7%) women had permanent amenorrhoea after embolisation including four patients under the age of 45 (2%). Of these, amenorrhea started between 4 and 18 months after embolisation, and only three had elevated follicle stimulating hormone levels when amenorrhea developed. Thirteen (4%) women had chronic vaginal discharge considered as a major irritant. Thirteen pregnancies occurred in 12 patients. Ninety-seven percent of women were pleased with the outcome and would recommend this treatment to others. CONCLUSIONS: Uterine artery embolisation is associated with a high clinical success rate and good fibroid volume reduction. Infective complications requiring hysterectomy, amenorrhoea under the age of 45 and chronic vaginal discharge may complicate the procedure.

Adult↗
PubMed2002

Fibroid embolization.

The most common surgical treatment for fibroids is hysterectomy and approximately 30,000 are carried out annually in the UK for this condition. The operation, however, carries a significant complication rate. Since the first case was carried out in 1989 there has been increasing interest in the interventional radiological procedure called fibroid embolization where angiographic techniques are used to occlude the vascular supply of fibroids. This article is a review of the world experience of fibroid embolization, its development, techniques, indications, results and complications. So far evidence indicates very promising mid-term results but more long-term comprehensive data is needed from large trials.

Adult↗
PubMed2002

Uterine artery embolisation for the treatment of symptomatic fibroids in 114 women: reduction in size of the fibroids and women's views of the success of the treatment.

OBJECTIVE: To assess the reduction in size of fibroids following uterine artery embolisation and to analyse women's views of the success of treatment. DESIGN: An uncontrolled case series of 114 consecutive women who underwent uterine artery embolisation for the treatment of fibroids over two years. SETTING: The Diagnostic and Interventional Radiology Department at The Royal Surrey County Hospital, Guildford, UK. METHODS: Bilateral uterine artery embolisation was performed for the treatment of symptomatic fibroids. Magnetic resonance imaging was carried out before and six months following embolisation. Women completed outcome questionnaires following their treatment. MAIN OUTCOME MEASURES: The sites. imaging signal characteristics and percentage reduction in the volume of three dominant fibroids were determined from the magnetic resonance scans. Outcome was measured by questionnaire. Women were asked whether their symptoms resolved completely, improved, remained unchanged or deteriorated. RESULTS: One hundred and sixty-five fibroids of 114 women (mean age 42) were analysed. Forty-five percent of women had complex fibroid masses and 50% had fibroids > or =8.5cm in diameter. The median reduction in the fibroid volume was 58%. The median reduction of the volume of complex fibroid masses, submucous fibroids, fibroids > or =8.5cm and fibroids with high and low signal on T2 weighted sequences were 58%, 63%, 50%, 62% and 51%, respectively. Ninety-one percent of the women's symptoms had resolved or improved following embolisation. DISCUSSION: The majority of women were satisfied with their outcome. We have shown that uterine artery embolisation is a successful treatment for symptomatic fibroids of all types, sizes and signal characteristics.

Adult↗
PubMed2000

Pathologic features of uterine leiomyomas following uterine artery embolization.

Bilateral uterine artery embolization has recently been employed as an alternative to operational treatment of uterine leiomyomas. The pathologic features induced by uterine artery embolization have not been previously described in detail. Usually patients experience symptomatic improvement with a reduction in size of the leiomyomas. This report describes the pathologic features in a series of 10 uterine leiomyomas where tissue was available for histologic examination following uterine artery embolization. Characteristic histologic features within the leiomyomas included massive necrosis, sometimes with dystrophic calcification, vascular thrombosis, and intravascular foreign material that elicited a histiocytic and foreign-body giant cell reaction. In some cases, intravascular foreign material was present elsewhere in the myometrium, the cervix, or paraovarian region. In occasional cases, there were foci of myometrial necrosis and microabscess formation beyond the confines of the leiomyomas. Foci of extrauterine inflammation were also occasionally identified. Histopathologists should be aware of these findings because the use of uterine artery embolization will possibly become more widespread in the future.

Adult↗
PubMed1999

The potential contribution of urban runoff to surface sediments of the Passaic River: sources and chemical characteristics.

Urban runoff has been reported as the second most frequent cause of surface water pollution in the United States. Due to the incidence of runoff in urban areas, it was of interest to estimate the impact runoff may have to recent sediment quality within the lower reaches of the Passaic River. Study objectives included i) review of recent urban runoff studies to determine the occurrence and pattern of distribution of chemicals in runoff; ii)comparison of the "fingerprints" from urban runoff studies to the contaminant distributions in surface sediments from the River; and iii) estimation of mass loadings to the surface sediments using surrogate data. The analyses showed that metals and PAH distributions in the sediments were similar to those observed in runoff from diverse locations, suggesting that urban runoff composition within the Passaic watershed is similar to other urban areas. Mass loading calculations demonstrated that urban runoff is a significant source of the metals observed in the sediments, and that PAH and DDT sediment loadings could, in some cases, be accounted for by urban runoff. Observed sediment loads for PCBs, however, were significantly higher than were estimated from urban runoff.

Fresh Water↗
PubMed1998

Uterine artery embolization for the treatment of uterine fibroids.

The first reported cases of uterine artery embolization in obstetric and gynaecological practice were carried out in the late 1970s. Recently, bilateral uterine artery embolization was used as a primary treatment for fibroids. Meticulous preoperative assessment is essential. The technique of uterine artery embolization involves the catheterization of both uterine arteries and the installation of tiny micro particles of polyvinyl alcohol. Following the procedure, post-procedural pain occurs within the first 24 h and most patients are advised to rest for 1 week. In the UCLA and RSCH series, three infective complications occurred leading to hysterectomy and some patients developed amenorrhoea. Average shrinkage of fibroids in the UCLA, RSCH and French series were 40%, 64% and 70%, respectively, with most patients losing their symptoms and being satisfied with the procedure. Meticulous pre-operative assessment is essential. At UCLA, 140 patients, and at RSCH, 96 patients have been embolized. To date in the UK, US and French series, fibroid growth has been arrested and new fibroids have not formed. However, long-term follow-up on a larger number of cases will be required before the role of uterine artery embolization in the gynaecologic therapeutic armamentarium can be fully defined.

Arteries↗
PubMed1996

Measles epidemics 1949-91: the impact of mass immunisation in New Zealand.

AIMS: Mass immunisation of children against measles was introduced in New Zealand in 1969. Although measles is not a notifiable illness in this country accurate hospital discharge data stratified by age and diagnosis are available. These were used to examine the impact of mass vaccination on measles epidemics. METHODS: Official public hospital discharge tables for the period 1949-92 were analysed. RESULTS: There were seven epidemics in the 20 year period from 1949-69 yielding an average interepidemic period of 2.86 years. Since 1969 epidemics have been separated by 3, 5, 3, 5 and 6 years. There has been no significant change in the number of patients discharged from hospitals in epidemic years since 1969. However, there has been a significant shift in their age distribution. Prior to 1969, in epidemic years, the proportion of patients with a discharge diagnosis of measles aged under 10 was 0.823, and aged 10-19 was 0.084. In 1991, the year of the last epidemic the corresponding figures were 0.643 and 0.28. CONCLUSION: These results are predictable from standard compartment models. From these models a simple equilibrium relationship is derived between the interepidemic period (Ti) and a change in the vaccination rate (Pi). This is T2 = T1 (1-p1)/(1-p2) and it is consistent with the New Zealand data. It is noted that measles epidemics could be prevented by periodic boosters or population based revaccination campaigns that prevented the number of susceptibles ever attaining the epidemic threshold.

Adolescent↗
PubMed1993

Long-term results of a single protocol for thrombolysis in acute lower-limb ischaemia.

In a prospective study, 78 of 157 patients with acute lower-limb ischaemia were considered suitable for thrombolysis. The immediate and 4-year results of 52 patients managed by a single protocol are reported. Of 34 patients alive at 4 years, 23 had limb salvage. Initial treatment produced effective lysis in 38 patients (73 per cent) with significant benefit in 35 (67 per cent); that benefit was sustained for a minimum of 4 years in 30 patients (58 per cent). Seven of the 18 deaths by 4 years occurred within 30 days. Amputation was carried out in six patients within 30 days and in five during the next 4 years. Delayed amputation followed persistent distal occlusion or progression of distal disease. No death or amputation was caused by complication of treatment. In selected patients the risks of thrombolysis can be reduced to an acceptable level by personal supervision and a strict protocol. In survivors, limb salvage is generally sustained for at least 4 years.

Acute Disease↗
PubMed1992

Complications attributable to the formation of the track in patients undergoing percutaneous nephrolithotomy.

Reported complication rates of percutaneous nephrolithotomy vary considerably. In our own experience of 110 percutaneous nephrolithotomies performed by an experienced interventional radiologist, the complication rate for the entire procedure was 3.6%, and for the formation of the nephrostomy track 0.9%. This compares favourably with the reports from the major centres. Radiation dose to the operator was monitored and our results confirm that with meticulous attention to technique, dosages may be kept very low. We conclude that prior training in interventional techniques is a major factor in reducing both the morbidity associated with percutaneous nephrolithotomy and the radiation dose to the operator.

Adolescent↗
PubMed1990

Conservative management of asymptomatic popliteal aneurysm.

Historical review shows that the treatment of popliteal aneurysm has developed by trial and error and there is disagreement about the proper management of the symptomless patient. In 1981 a policy of conservative management for asymptomatic popliteal aneurysm was adopted in this unit. Since that time we have also managed nine patients with thrombosed popliteal aneurysms by arteriography and low-dose intra-arterial streptokinase. Six patients treated within 72 h of occlusion achieved significant (70-100 per cent) lysis, but streptokinase was ineffective in those treated 10 or more days after the thrombosis. Of the six patients with significant lysis, three were treated by elective reconstruction and two by anticoagulation. One patient who had significant lysis died. Vascular patency of all five successfully treated limbs was maintained and no limb loss occurred in those who presented late and failed to achieve significant lysis. These results reinforce the view that thrombolysis is the treatment of choice for thrombosed popliteal aneurysms. The low complication rate for asymptomatic popliteal aneurysms and the advent of safe, effective thrombolysis indicate that operation for symptomless popliteal aneurysm is no longer required.

Adult↗