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Biomedical subjects

G M Lennon

Publications and source records attributed to G M Lennon.

16 recordsLinked to original sources
PubMed1997

Double pigtail ureteric stent versus percutaneous nephrostomy: effects on stone transit and ureteric motility.

OBJECTIVES AND METHODS: The effects of double pigtail ureteric catheters (JJS) and percutaneous nephrostomies (PN) on ureteric motility and artificial stone transit was assessed in 12 dogs. Each animal underwent bilateral nephrostomies and an artificial stone insertion into each upper ureter (n = 20). A 4-Fr JJS was inserted on one side (group 1) while a PN was left on the contralateral side (group 2). In 4 stone-only 'control' ureters (group 3), the PN was sealed after 72 h. Stone passage was assessed by plain x-rays. Pelvic and ureteric motility was assessed prior to stone insertion and again at 2 weeks. RESULTS: In group 1, only 1 of 8 stones (12.5%) passed completely. Four reached the midureter, 3 remained static. Six of 8 stones (75%) in group 2 passed completely. Two stones remained in the distal ureter. All 4 stones (100%) in group 3 passed by day 3 postoperatively. At laparotomy the J-stented ureters were dilated and both pelvic and ureteric contractions were diminished. Ureteric diameter was normal on the PN side. The ureters contracted with normal amplitude, but diminished rate of contraction above the stones in the ureters with residual calculi (n = 2), and in the 6 ureters from which spontaneous stone passage had occurred. A similar pattern was found in the 4 group 3 ureters. CONCLUSIONS: Double J stents are associated with ureteric dilatation, diminished peristalsis and impaired stone passage. APN preserves ureteric peristalsis and facilitates stone passage. In the initial phase, raised hydrostatic pressure appears to the most important factor determining stone passage.

Animals↗
PubMed1995

'Firm' versus 'soft' double pigtail ureteric stents: a randomised blind comparative trial.

It is generally considered that 'firm' double pigtail ureteric catheters, while easier to insert and less prone to migration, may cause more patient discomfort than the 'softer' variety of stent. Objective support for these perceptions is however lacking. The aim of this study was to compare firm and soft stents regarding their ease of insertion, positional stability, biocompatibility and patient tolerance. 155 patients were randomised to receive 'firm' (polyurethane, n = 78) or 'soft' (Sof-Flex, n = 77) stents. Ease and mode of insertion was recorded at time of initial placement. Positional stability, degree of bladder inflammation, stent encrustation and patient tolerance were recorded at the time of removal. Patient tolerance was assessed by symptom score in double-blind fashion. Results showed no significant difference in ease of insertion, positional stability, degree of bladder inflammation or stent encrustation between the two groups. There was a significantly higher incidence of dysuria, renal and suprapubic pain in the firm stent group. There was no significant difference in the incidence of urgency, frequency, nocturia or haematuria. Normal activity and return to work were reported in 67 and 45% of patients with soft and firm stents, respectively. The data indicates that patient tolerance appears to be related to the softness of the stent material.

Biocompatible Materials↗
PubMed1994

The effects of acute and chronic JJ stent placement on upper urinary tract motility and calculus transit.

OBJECTIVE: To determine the pathophysiological changes in upper urinary tract motility and calculus transit which may occur following JJ stent insertion. MATERIALS AND METHODS: The acute and chronic effects of JJ stent placement were studied in 24 canine renal units. Intrarenal and intraureteric pressures and motility were measured, in addition to transit times for complete passage of synthetic calculi from the upper ureter into the bladder. RESULTS: Acute effects included raised renal intrapelvic pressure, reduced pelvic and ureteric motility and delayed calculus transit time. Prolonged JJ stent placement was associated with return of intrapelvic pressure to normal but persistent changes in both renal and ureteric motility and also calculus transit time. CONCLUSION: In situ JJ stents impair upper urinary tract motility and experimental calculus transit time and may delay passage of ureteric calculi or calculus fragments following extracorporeal shock wave lithotripsy.

Animals↗
PubMed1994

Effects of balloon dilatation on canine ureteric physiology.

The concept of adynamic ureteric obstruction following balloon dilatation was explored in 12 female mongrel dogs. Upper ureteric segments were dilated to 15 french at 10 atm for 3 min. Pressure and motility in the dilated segments were compared to that proximal and distal to the dilated segment prior to, immediately after, and at 2 and 6 weeks after dilatation. Immediately after dilatation the dilated segment and proximal pelvi-ureter showed a rise in baseline pressure from 2.5 +/- 0.3 and 1.9 +/- 0.3 to 32 +/- 4.6 and 37.2 +/- 5.7 mm Hg, with an associated decrease in the amplitude of contractions. Distal ureteric pressure/motility was unaffected at this point. At 2 weeks, the motility of the pelvis, dilated segment and distal ureter was diminished. Nephrostograms showed hydronephrosis and dilated upper ureteric segments with extravasation in 2 animals. At 6 weeks there was residual dilatation but motility of the dilated segment, and that of the proximal pelvi-ureter and distal ureter had returned to normal.

Animals↗
PubMed1993

Ischaemia-reperfusion injury in the rat kidney: effect of a single dose of sodium bicarbonate.

The protective effect of intravenous 8.4 per cent sodium bicarbonate on renal function after ischaemia was evaluated in rats subjected to 45 or 90 min warm unilateral renal ischaemia. Two groups of control animals received normal or 3 per cent saline. All solutions were given by bolus injection 3 h before ischaemia. Renal function was significantly protected in animals receiving bicarbonate. Vascular congestion of the inner stripe of the renal medulla was prevented. The survival rate in the group undergoing 90-min ischaemia was 70 per cent for animals receiving bicarbonate and nil in those given saline. Preoperative alkalinization confers significant functional and morphological protection in the ischaemic kidney.

Animals↗
PubMed1993

The effect of stones on renal and ureteric physiology.

The effect of calculi on renal and ureteric function is the result of a complex sequence of pathophysiological events triggered by obstruction. The degree of impairment of renal function resulting depends on whether the obstruction is partial or complete, is unilateral or bilateral, is complicated by infection or not and how and when it is relieved. This review will look at these interacting factors and particularly on the effects of various treatment modalities ranging from open techniques to minimally and non-invasive interventions.

Animals↗
PubMed1993

The ureter in vitro: normal motility and response to urinary pathogens.

The effects of bacteria on in vitro ureteric contractility were studied, using a model which allowed selective exposure of organisms to the ureteric mucosa and smooth muscle, respectively. A cannula attached to a pressure transducer was ligated into the proximal lumen of 2.5-cm segments of canine ureter. The distal ureter was ligated to form a closed pressure monitored system, and the segment suspended in a 20-ml organ bath containing Krebs Henseleit buffer at physiological pH and temperature. Following onset of spontaneous activity, broths of Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus were added to either the buffer solution or ureteric lumen in doses of > 10(6) organisms/ml. Experiments were repeated using heat-killed organisms, bacterial filtrates and E. coli endotoxin. Ureteric contractility was stimulated by organisms added to the buffer medium, but reversibly inhibited by bacteria placed in the ureteric lumen. Heat-killed organisms, endotoxin and live filtrates had no effect on normal motility when exposed to either the ureteric mucosa or muscularis respectively. These findings reflect the conflicting changes in ureteric motility seen in vivo when bacteria are administered systemically or directly into the ureteric lumen.

Animals↗
PubMed1993

Pharmacological options for the treatment of acute ureteric colic. An in vitro experimental study.

The effects of opiate and non-steroidal anti-inflammatory agents on the in vitro canine ureter were compared using a new model for the assessment of ureteric pharmacology. A pressure measuring catheter attached to a pressure transducer and pre-calibrated pen recorder was ligated into the lumen of 2.5 cm segments of normal canine ureter. The segments were immersed in an organ bath at physiological pH and temperature and spontaneous contractility was observed in 90% of them. Morphine had a spasmogenic effect on ureteric activity which was unaffected by naloxone. This effect was similar to that of histamine and prostaglandin F2 alpha and was abolished by chlorpheniramine but not by cimetidine. Pethidine produced a transient stimulation followed by inhibition of ureteric activity which was unaffected by naloxone. Both indomethacin and diclofenac produced an abrupt inhibition which was reversible with prostaglandin F2 alpha. These data suggest that pethidine or a non-steroidal anti-inflammatory agent may by virtue of their spasmolytic effects be a superior choice of therapy for the acutely obstructed ureter.

Acute Disease↗
PubMed1993

Recovery of ureteric motility following complete and partial ureteric obstruction.

Complete and partial ureteric obstruction was created in 2 groups of 10 mongrel dogs by placing a ligature around, or inserting a fine bore plastic stent into, the lower end of the left ureter (Groups 1 and 2). After 4 weeks the ligature or stent was removed, a 2.5-cm segment of ureter was harvested for in vitro analysis and the ureter reimplanted into the bladder. Pelvic and ureteric pressures and motility were recorded before, during and after the period of obstruction via a subcutaneously placed nephrostomy tube. Pre-obstruction resting intra-ureteric pressure was 2.1 +/- 0.3 mm Hg (mean +/- SEM), with regular contractions 8.9 +/- 0.7/min of 36.2 +/- 1.2 mm Hg amplitude. After 4 weeks of obstruction, contractility was abolished in Group 1 but increased in Group 2, 71.5 +/- 3.3 mm Hg, with irregular multiphasic contractions seen following diuresis. Intra-ureteric pressure was 16.3 + 1.2 mm Hg in Group 1 and 9.3 + 1.2 mm Hg in Group 2. In vitro experiments confirmed the patterns of contractility seen in vivo. Eight weeks after reimplantation the ureter returned to normal rhythm and rate in Group 1, but increased contractility persisted both in vivo and in vitro in Group 2.

Animals↗
PubMed1991

Changes in regional renal perfusion following ischemia/reperfusion injury to the rat kidney.

Post-ischemic renal failure is associated with a zone of vascular hyperaemia in the outer medulla of the kidney. The effect of this lesion on regional renal perfusion is, however, unclear. Acute unilateral renal ischemia was applied to four groups of ten adult male Wistar rats for a period of 60 min, followed by revascularisation for 0, 15, 30 or 60 min. The aorta was then clamped and Microfil was injected at a standard pressure to fill the renal vasculature. Gross and histological examinations of the renal parenchyma and vasculature were then performed. Regional renal Microfil perfusion was quantified by examination of unstained histological sections, giving rise to a vascular perfusion index (VPI) for each vascular region of the kidney. The VPIs were similar in control and ischemic kidneys that were not subjected to reflow (group 1). In contrast, the VPI was markedly decreased in the inner stripe and inner medulla in animals in which revascularisation had occurred (groups 2-4), and the vasculature in these regions was histologically shown to be packed with red blood cells. Post-ischemic renal failure is associated with hyperperfusion of the medulla resulting from blockage of the vasculature that occurs during revascularisation.

Acute Kidney Injury↗
PubMed1991

Broncho-oesophageal fistula of infectious origin.

A case of end stage pulmonary destruction secondary to adult onset broncho-oesophageal fistula of infectious aetiology is presented. Advanced bronchiectatic damage to the pulmonary parenchyma may be avoided by the maintenance of a high index of suspicion and a systematic approach to the diagnosis of recurrent lower respiratory tract infections.

Adult↗
PubMed1990

Knowledge, attitudes, technical competence, and blood glucose control of Type 1 diabetic patients during and after an education programme.

Thirty-one Type 1 diabetic patients entered a 12-month education programme in which attitudes to diabetes, knowledge of diabetes, and technical competence were assessed using questionnaires and practical tests. A closely matched group of 25 control patients continued to receive routine clinic care. Patients completing the education programme showed improved blood glucose control (HbA1 decreased from 11.8 +/- 0.4% to 10.5 +/- 0.3%, mean +/- SE, p less than 0.01), whereas blood glucose control was not altered in the control group (HbA1 11.8 +/- 0.5% before and 11.6 +/- 0.4% after 12 months). Patients completing the education programme also showed greater knowledge (p less than 0.001), more favourable attitudes (p less than 0.03), and increased competence in technical skills (p less than 0.02) compared with the control group. Six months after completing the programme blood glucose control deteriorated (HbA1 11.0 +/- 0.4%, p less than 0.05), although knowledge, attitudes, and technical competence were unchanged. This might reflect the withdrawal of extrinsic motivation and attention provided during the programme. Thus consideration should be given to development of the patient's intrinsic motivation to prolong the benefits of diabetes education programmes.

Adult↗
PubMed1989

Malignant melanoma lately diagnosed.

To assess the clinical impression that patients in Dublin were presenting with late, deep, poor prognosis lesions, a 10 year retrospective review of patients with malignant melanoma was performed. The pathological data on 186 patients was examined and clinical follow-up obtained on 151 of these (80%). The mean period of follow-up was 35 months. Females predominated in a ratio of 3:1. Incidence figures for the two five year periods (1976-80) and (1981-85) indicated a rise in the latter period of over 100%. There was a marked delay in presentation after the onset of symptoms i.e. new pigmented lesions or changes in pre-existing lesions (mean = 21 months). Only 45% of lesions were less than 1.5mm in depth. Females presented with a higher percentage of good prognosis lesions reflected in a superior five year survival figure of 70% compared with 43% for males. The results of this study suggest an increase in incidence and mortality from malignant melanoma in this country. Patients appear to be unaware of the significance of pigmented lesions, presenting late with deep poor prognosis tumours.

Adolescent↗