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Biomedical subjects

M E Snell

Publications and source records attributed to M E Snell.

At least 37 records · Page 2Linked to original sources
PubMed1992

Endoscopic placement of CAPD catheters: a review of one hundred procedures.

One hundred consecutive endoscopically placed peritoneal dialysis catheters inserted in 95 patients over an 18-month period have been reviewed. All catheters were placed for chronic dialysis (CAPD). Following insertion there were five early catheter failures (4 failed to drain, 1 perforated viscus) and 13 early complications (7 leaks, 3 tunnel bleeds, 2 scrotal oedema, 1 wound infection). In the long term six patients required transfer to haemodialysis (2 recurrent peritonitis, 2 pain on outflow, 1 unable to cope, 1 persistent vomiting). Overall probability of catheter survival as predicted by Kaplan-Meier analysis was 0.85 at 18 months. These results confirm that endoscopic placement of CAPD catheters is safe and reliable. In addition there is a low early failure rate and the long-term catheter survival figure is comparable with the best series reported. This procedure allows direct visualization of the peritoneal cavity, thus minimizing the risk of visceral damage. Furthermore, the procedure is well tolerated under local anaesthesia and allows early institution of dialysis because of the extremely low leakage rate (11%). Endoscopic placement of CAPD catheters is now the procedure of choice in our centre. General anaesthetic and mini-laparotomy are thus avoided in most of this high-risk group.

Adolescent↗
PubMed1991

A study of the effects of trend, variability, frequency, and form of data on teachers' judgments about progress and their decisions about program change.

Past research has demonstrated the influence of various factors on teachers' judgments about their students' progress. When graphed data are viewed, teachers tend to make different decisions depending upon the amount of data viewed and its trend. Current surveys of teachers' practices in data collection and decision-making indicate that teachers primarily collect training data which are examined in both graphed and ungraphed (response by response) forms to make weekly decisions about progress. In this study, 56 teachers of students with moderate to profound disabilities viewed task analytic data in one of three forms: graphed, ungraphed, or both forms. Teachers were asked to describe the progress and make a program recommendation for each student whose data they examined. Three repeated factors (trend, variability, and frequency of data collection) also were examined for their effect on the dependent variables and their interactions with data form and with each other. Results were in agreement with earlier research and further indicated that the form of the data did not produce different judgments or decisions. However, the three factors, trend, variability, and the frequency of data collection, all had significant main effects with teachers' descriptions about student progress and their program recommendations; several significant interactions among the factors also were found.

Achievement↗
PubMed1991

Reproducibility of renal blood flow estimation in the miniature pig using 99Tcm-DTPA: introducing semiautomatic processing.

This study examines the reproducibility of renal blood flow measurement (RBF) in nine miniature pigs using 99Tcm-DTPA renography, and introduces a new algorithm useful in data processing. Renal blood flow can be estimated using three arterial regions of interest (ROI), the left ventricle (LV), the right lung (RL) and the aorta. Using the LV ROI, left kidney RBF was 9.08 (S.D. 1.69) and right RBF was 10.87 (S.D. 2.26). Reproducibility was assessed by performing renograms on successive days in nine pigs and was found to be best for LV [S.D. of change 0.32 for the left kidney (LK) and 0.74 for the right kidney (RK)] followed by RL (0.77 for LK and 0.75 for RK) and worst for aorta (1.47 for LK and 1.78 for RK).

Algorithms↗
PubMed1991

Estimation of glomerular filtration rate in the miniature pig by kidney uptake on the gamma camera.

Measurement of glomerular filtration rate (GFR) by the renal uptake of 99Tcm-diethylene triamine penta-acetic acid (99Tcm-DTPA) in the miniature pig was compared to that by plasma disappearance of 99Tcm-DTPA using multiple blood samples. Nineteen animals were examined under identical conditions. There was a highly significant relationship between the two tests, r = 0.88, P less than 0.001, although the uptake method gave consistently higher results than those obtained from plasma disappearance. Reproducibility of the uptake method was also assessed in this group of animals by performing two consecutive renograms. Confidence limits of 95% were +/- 7.5% or 0.7 ml min-1 kg-1. The test is useful for the serial examination of single kidney GFR on follow-up renography but is unlikely to replace disappearance techniques as a more accurate means of GFR estimation.

Animals↗
PubMed1991

Sequential renography in acute urinary tract obstruction due to stone disease.

A group of 76 patients with urographically proven acute calculus obstruction was studied prospectively using 99mTc-DTPA renography to see if kidneys at risk of irreversible renal damage could be identified. There was a statistically significant relationship between the presence of obstruction on renography and the subsequent requirement for intervention, but not with the degree of obstruction (partial or severe). Stones over 5 mm in size are highly likely to cause obstruction, a drop in relative renal function and require intervention. In all, 14 patients sustained a drop in relative renal function of greater than 7% on renography and 12 of these returned to normal limits when their calculi had been passed or removed. The 2 kidneys whose function remained impaired had fallen below 25% of overall renal function and both patients had received prior treatment for their calculi. No patient who presented de novo suffered any permanent loss of ipsilateral renal function. The results confirm that the criteria for intervention were well founded and emphasise the importance of achieving a stone-free state after primary treatment. Renography is recommended for stones over 5 mm in size, those in the middle and upper ureter and for those patients discharged with a stone in situ.

Adult↗
PubMed1990

Studies of circulating parathyroid hormone following parathyroidectomy in renal osteodystrophy.

A study has been undertaken to document in detail some of the changes that occur following parathyroidectomy in chronic renal failure patients. In an attempt to predict more precisely the timing of the post-operative hypocalcaemia, serum parathyroid hormone (PTH) concentrations were measured in six patients with renal osteodystrophy undergoing subtotal parathyroidectomy [5] and total parathyroidectomy [1]. The values obtained were related to post-operative changes in serum calcium and albumin concentrations. The intact-PTH concentration in serum was shown to decline rapidly post-operatively while the C-terminal PTH followed a more gradual course. Neither total nor ionised serum calcium concentrations exhibited a correspondingly dramatic fall after parathyroidectomy and the serum albumin concentration remained unaltered.

Adult↗
PubMed1990

Three new primary pelvic carcinomas in a patient following radiotherapy for carcinoma of the cervix. Case report.

A 67-year-old woman developed three separate pelvic malignancies forty years after undergoing radiotherapy for a squamous cell carcinoma of the cervix. Although previous exposure to ionising radiation is associated with certain malignancies, review of the literature indicates that there is no strong evidence to support such an association with urothelial or colorectal malignancy.

Adenocarcinoma↗
PubMed1989

A study of the effects of frequency of probe data collection and graph characteristics on teachers' visual analysis.

Teachers often rely on visual analysis of graphed student performance data to evaluate progress and make program decisions. However, because collecting data can be time consuming and interfere with instruction, teachers would like to know how much data is necessary to make reliable judgments. To investigate the effect of frequency of data collection on teachers' judgments and decisions, this study addressed the question of whether teachers' judgments differ according to frequency of data collection, whether teachers' judgments differ according to type of trend, and whether teachers' judgments based on different types of graphs vary with frequency of data collection. A set of 16 graphs of actual student performance data was analyzed by 59 teachers of students with moderate to profound handicaps. The data were analyzed by a two-factor repeated measures design, and results indicated that when asked to evaluate student performance, teachers' judgments tended to be consistent and accurate when the graphed data represented continuous and systematic improvement in performance. However, when the data represented a decrease in performance, no change, or highly variable performance, judgments tended to differ by frequency. When asked to make program recommendations, teachers' judgments tended to differ by frequency for all types of trends.

Data Collection↗
PubMed1988

Traumatic renal artery dissection.

Hypertension consequent upon traumatic subintimal dissection of the renal artery is described in 2 cases. The pathogenesis and treatment of this uncommon condition are presented.

Adult↗
PubMed1987

Use of hybridot assay to screen for BK and JC polyomaviruses in non-immunosuppressed patients.

Urine samples from 50 patients attending a genitourinary outpatient clinic and from 13 renal allograft recipients were investigated for evidence of infection with human BK and JC polyomaviruses using cytology and a new DNA hybridot assay. Forty four per cent of samples from the renal allograft recipients were positive by cytology and 75% by DNA hybridisation, indicating that hybridot assay is more sensitive than cytological screening. BK and JC viral DNA was found in 20% of the patients attending the genitourinary clinic, showing infection with BK virus and JC virus in a group of patients with clinical conditions not normally associated with immunological deficiency-a finding that has not been reported before.

Adult↗
PubMed1986

Detection and investigation of renal artery stenosis.

A retrospective analysis was done on 235 hypertensive patients undergoing renal arteriography. Of the 85 patients with renal artery stenosis 50 underwent 56 operations or angioplasties and have been followed up for at least a year. 41 (73%) of these procedures were curative or led to improved blood-pressure control. These results make it worthwhile identifying hypertensive patients with renal artery stenosis who may benefit from surgery or angioplasty. Vascular disease, epigastric bruit, and impaired renal function were commoner in the renal artery stenosis patients than in the 81 with normal arteriograms, but there were no features pathognomonic of stenosis. Intravenous urography had a sensitivity of 83% and a specificity of 69.5% in identifying renal artery stenosis; those for isotope renography were 90.5% and 38.5%, respectively. Divided renal vein renins did not predict the outcome of intervention. Arteriography should, if there are no contraindications to intervention, be the first and definitive investigation when renal artery stenosis is suspected--for instance, in hypertensive patients with accelerated or malignant hypertension, those whose blood pressure is poorly controlled by multiple therapy, and those who have had recent deterioration in blood-pressure control or renal function.

Adult↗
PubMed1983

Advances in the techniques of localisation of adrenal tumours and their influence on the surgical approach to the tumour.

The results of attempts to localise adrenal tumours in 65 patients are presented. In the first series (1966-1978) adrenal phlebography and adrenal vein sampling located 18 of 20 (90%) of adrenocortical tumours and 18 of 19 (94%) phaeochromocytomas were defined by angiography and venous sampling. In the second series CT located 7 of 8 adrenocortical and all 6 intra-abdominal phaeochromocytomas. Scintigraphy located all 9 adrenocortical tumours and both of the phaeochromocytomas examined. Confidence in the ability of newer techniques allows the use of a flank incision in most cases, thus reducing the operative morbidity.

Adrenal Cortex Neoplasms↗
PubMed1983

Clonidine lowers blood pressure independently of renin suppression in patients with unilateral renal artery stenosis.

The effects of 300 micrograms of oral clonidine were studied in nine patients with unilateral renal artery stenosis proved by selective renal arteriography. Blood pressure, heart rate, plasma renin activity (PRA) levels, plasma noradrenaline levels, and sedation were measured before and for eight hours after dosage. After clonidine administration, both systolic and diastolic blood pressure fell within the first hour, was maximum in the fourth hour, and remained lower than predosage levels even in the eighth hour. There was a fall in heart rate, maximum in the fourth hour. There were minimal changes in PRA levels after giving the clonidine. Plasma noradrenaline levels fell, with the maximum fall in the sixth hour. Sedation occurred within one hour of dosage and was maximum in the second hour. We conclude that in patients with unilateral renal artery stenosis clonidine causes a substantial and prolonged fall in blood pressure not accompanied by suppression of PRA levels but by a reduction in plasma noradrenaline levels. This suggests a role for central pressor mechanisms, probably linked to angiotensin II and central sympathetic activation, in the maintenance of hypertension in patients with renal artery stenosis.

Adult↗
PubMed1981

Idiopathic pelvic fibrosis: a variant of retroperitoneal fibrosis?

The management of 2 cases of a rare condition previously labelled idiopathic pelvic fibrosis is described. Two cases reported previously are reviewed. The unusual histologic and radiologic features are emphasized, and the differences between this condition and idiopathic retroperitoneal fibrosis are summarized. Etiologic features, including the possible role of previous pelvic infection, drug-induced hypersensitivity and autoimmunity, are discussed. We believe that disease originating in the vas may be the source of this unusual fibrotic process.

Adult↗