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Biomedical subjects

S Willis

Publications and source records attributed to S Willis.

At least 37 records · Page 2Linked to original sources
PubMed2002

Childbirth and incontinence: a prospective study on anal sphincter morphology and function before and early after vaginal delivery.

PURPOSE: Disturbance of anal continence is a well-known problem after vaginal delivery. However, only few and incongruent data on the incidence and pathogenesis of postpartum incontinence are available. This study examined the effects of vaginal delivery on anal continence prospectively. METHODS: In 42 unselected women anal vector manometry and endoanal ultrasonography were performed, and pudendal nerve terminal motor latency (PNTML) and rectal sensibility were measured in the 32th week of pregnancy and 6 weeks after delivery. Continence was evaluated according to the Kelly-Holschneider score. Patients with occult sphincter defects were additionally followed-up 12 weeks after vaginal delivery. To exclude any effect of pregnancy alone ten patients with elective cesarian section served as controls. RESULTS: Overall continence after vaginal delivery did not differ significantly from that before delivery, there was a significant reduction in postpartum anal squeeze and resting pressures in all patients. Obstetric tears of grade III or IV occurred in 9% of the patients. Endosonography revealed occult lesions of the internal and external anal sphincter in an additional 19% of women who clinically seemed to have an intact sphincter. Manometric results and continence in these women did not differ significantly from those with intact sphincter and remained unchanged after 12 weeks. PNTML and rectal sensibility were not affected by vaginal delivery. After cesarian section there were no changes in continence, anal pressures, rectal sensibility, or PNTML. CONCLUSIONS: Vaginal delivery leads to direct mechanical trauma to the anal sphincters, while stretch and distension of the pudendal nerve seem to be of minor importance. Only endoanal ultrasonography is suitable for detection of occult sphincter lesions.

Adult↗
PubMed2002

Effective dose in paediatric computed tomography.

There is limited data currently available for making dose and risk assessments for paediatric patients undergoing computed tomographic examination. A method has been developed to correlate the risk-related quantity, effective dose, to the more simply derived quantity dose-length product. This involved scanning a series of paediatric anthropomorphic phantoms containing thermoluminescent dosimeters to measure effective dose for scans of various anatomic regions. The quantity effective dose per dose-length product was calculated and plotted as a function of patient size. This showed a simple exponential relationship, and equations of fit were derived to enable the calculation of effective dose for a patient of any size. Measurements carried out on a second scanner and for alternative scan volumes indicated that the method could be generally utilized.

Adolescent↗
PubMed2002

[Update on incisional hernia. Parastomal hernia].

Parastomal herniation is a frequent complication when an artificial anus is constructed. As a tunnel through the abdominal wall is nonphysiological, there is an inherent trend to enlargement of the aperture with any artificial stoma. However, none of the technical modifications tried has proved reliable in reducing the incidence of parastomal herniation. The only clear-cut indications for repair are ileus and incarceration or serious problems with the colostomy bags. There are three basic methods of repair: fascial closure, stoma relocation and augmentation of the abdominal wall by nonabsorbable meshes, and any of the three can be combined in many ways. The first two techniques each have a recurrence rate of 40%-80%, and neither can therefore any longer be recommended for use in isolation. Only with the last technique of abdominal wall reinforcement it is possible to achieve a recurrence rate of under 20%. The best type of mesh and the optimal implantation technique are still under discussion.

Colostomy↗
PubMed2002

A simple new method to calculate small intestine absorptive surface in the rat.

The rat is an established model for studying intestinal adaptations following abdominal surgery. In the study of functional and morphological adaptations of the small intestine, it is helpful to estimate the mucosal surface area. In order to simplify measurements and calculation we developed a new mathematical model for calculation of the mucosal surface area on histological sections. In contrast to other methods, it requires only cross-sections of small intestine and includes the measurement of only three histological parameters: length and width of villus and width of crypt. The new approach was compared with the most commonly used procedures, the Harris and the Fisher-Parsons methods, under experimental conditions. An animal study including single-pass perfusion, fixation, staining and subsequent histomorphometry of jejunum and ileum using these different methods was performed. The new method showed the least work and presented no significant differences compared with the precise Harris method. In conclusion, the method described is an adequate tool to estimate the mucosal surface area with less work and with comparable results to established methods. The less-complex method may be a valuable tool in experimental research of small intestine adaptations in rats.

Animals↗
PubMed2001

[Orthopedic/visceral surgery cooperation in pelvic tumors].

Co-operation between orthopaedic surgeons and visceral surgeons is required in the treatment of malignant tumours of the pelvis when the rectum or the iliac vessels are infiltrated. Such infiltration can be expected in malignancies which originate in the sacrum. Most frequently, chordomas are found in this area, that should be resected with wide surgical margins even in advanced tumours to reduce the risk of local recurrence. When resecting the sacrum, the stability of the vertebral column and the pelvis is compromised only at levels above S2. After unilateral resection of the sacral nerve roots S2-S5, there are only minor impairments of the anal and bladder sphincter control. In the case of tumour infiltration of the rectum and simultaneous resection of the sacral nerve roots, abdominoperineal extirpation of the rectum is required even when a safe margin is left between the tumour and the anal sphincter. In different studies, the 5-year survival in patients with a malignancy of the sacrum varies between 52% and 84%. In view of the rarity of these tumours, treatment should be performed only at specialized centers where co-operation is ensured.

Bone Neoplasms↗
PubMed2001

Does loperamide affect motor activity after proctocolectomy and ileal pouch-anal anastomosis? An experimental study in dogs.

This study investigated the effect of loperamide on the motor function of small intestine and J-pouch. Proctocolectomy and ileal pouch-anal anastomosis were performed in four dogs. Motility was recorded by serosal electrodes and strain gauge transducers. The intestinal transit time was determined radiologically. Multiple measurements were performed before and during chronic administration of loperamide. This treatment led to a significant decrease in median stool frequency from 11 (10-13) to 9 stools/day (8-12) and a tendential increase in intestinal transit time from 60 (50-105) to 70 min (60-90). This was not accompanied by significant changes in fasted or postprandial motility. There were no significant differences in the characteristics of the migrating myoelectric complex or in the fed pattern, either in the small intestine or in the pouch. Loperamide thus does not significantly affect intestinal motility after ileal pouch-anal anastomosis. The reduction in stool frequency seems to be due to antisecretory effects in the first line.

Animals↗
PubMed2001

Comparison of colonic J-pouch reconstruction and straight coloanal anastomosis after intersphincteric rectal resection.

The tendency towards sphincter-preserving resection for distal rectal cancers has led to the technique of straight coloanal anastomosis (CAA) and colonic J-pouch anal anastomosis (CPA) after low anterior resection. The aim of the present study was to compare complication rate, anorectal physiology and functional results after both types of reconstruction after ultra-low intersphincteric resection. A total of 31 patients who had undergone CPA were followed up prospectively using anorectal manometry and a standardised questionnaire and were compared with 63 patients who had undergone CAA and were followed up in the same way. The complication rate after CPA did not differ significantly from that after CAA. One year postoperatively, the median stool frequency and urgency were reduced after CPA (1.7+/-2.2/day; 7% vs. 2.4+/-3.6/day; 14%; P<0.05). Three months after colostomy/ileostomy closure, the maximum tolerable volume, threshold volume and compliance were decreased after CAA when compared with CPA (55+/-12, 34+/-12, and 3.9+/-0.3 ml/mmHg vs. 85+/-21, 53+/-11 and 6.2 ml/mmHg, respectively; P<0.05). Anal manometry revealed no significant differences in the anal resting and squeeze pressure. One year postoperatively, continence also did not differ significantly between CPA and CAA. Colonic J-pouch reconstruction seems to be superior to the straight coloanal anastomosis, especially during the first postoperative year. In view of the often poor prognosis of the patients, it is the reconstruction of choice after ultra-low resections of the rectum.

Anal Canal↗
PubMed2001

[Evidence-based surgery of rectal carcinoma].

The surgery of rectal cancer has seen significant development in recent years. When there is a multitude of therapeutic options available, it is essential to identify what can be considered a proven standard or, at least, what has to be included in planning a surgical treatment. Therefore, at this point of time a distal resection margin of 2 cm, total mesorectal excision, en-bloc resection of adherent structures, colonic pouch reconstruction after very deep resections and limitation of local excision to T1/G1 tumors have to be regarded as standards of the surgical strategy.

Adult↗
PubMed2001

Referrals and relationships: in-practice referrals meetings in a general practice.

BACKGROUND: GP referrals to secondary care are an important factor in the cost of running the NHS. The known variation in referral rates between doctors has the potential to cause tension within primary care which will be exacerbated by the latest reorganization of primary care and the trend towards capitation-based budgets. The importance of postgraduate learning for GPs has been recognized; continuing professional development is moving towards self-directed practice-based learning programmes. Educational interventions have been shown to alter doctors' prescribing behaviour. This, together with the pressure on accounting for referral activity, makes the prospect of improving, and possibly reducing, referral activity through educational interventions very attractive. OBJECTIVES: This study complemented a randomized controlled trial (RCT) which investigated whether an intervention of the type which had reduced prescribing costs would have a similar effect on referral activity. METHODS: The context of the study, description of the characteristics of the practice and the issues seen as important by the doctors and practice manager were identified through preliminary semi-structured interviews. The practice then held a series of educational in-practice meetings to discuss referrals and issues arising from referrals. The audio- and videotaped transcripts were interpreted using content and group dynamic analysis. Participants commented upon our preliminary findings. In addition, we used dimensional analysis to induce a preliminary theory describing the effect of the intervention on this general practice which enabled us to review the findings of the parallel RCT. The educational value of the meetings and the learning needs of the participants were also assessed. RESULTS: Our complementary study showed no alteration of practice referral rates following the educational intervention. The qualitative study, unencumbered by the assumptions inherent in the development of the hypothesis tested in the RCT, highlighted the complexity of decision making in general practice and the likely impact of historical background and a variety of internal and external pressures on this self-directive educational intervention. The practice members described the individual and group learning needs identified as a result of the meetings. CONCLUSION: The findings of this study raise important questions for developing practice-based learning. The outcomes of self-directive interventions in practices will be influenced by internal and external events both past and present. Such outcomes may be qualitative and difficult to measure. They are likely to differ from outcomes seen when interventions are applied to groups of doctors who are not all members of the same practice.

Family Practice↗
PubMed2001

Students' conceptual model of a good community attachment.

BACKGROUND: In 1994, Manchester University Medical School introduced a new integrated curriculum using problem-based learning and which places an increased emphasis on community-based education. AIMS: Students commonly use a particular label ("a good GP" (general practitioner)) to describe a positive experience in the community. The purpose of the study was to explore what students mean by "a good GP" and how this relates to their perceptions of the value of the community aspect of the course. METHOD: Three single-year focus groups were run with year 3, 4 and 5 students. A model was then derived which was explored and checked against the views of a cross-year focus group. RESULTS: A theoretical model based on student conceptualization of "a good GP" was developed. "A good GP" was found to consist of the GP as a teacher, as a role model and as an indicator of a positive learning environment. With regard to "good teacher", students felt that the GP's enthusiasm about teaching and involving the student in an active learning process was important. For "good role model", students emphasized communication skills and non-judgmental attitudes. With regard to "good learning environment", a friendly atmosphere, variety of activities, and flexibility shown by the staff of the health centre were important. CONCLUSIONS: Students hold a complex conceptual model of "a good GP" which the label does not convey. We suggest that for evaluations of student experiences it is important to explore in depth what students mean by particular terms or labels.

Attitude of Health Personnel↗
PubMed2001

Mollusks of Manuel Antonio National Park, Pacific Costa Rica.

The mollusks in Manuel Antonio National Park on the central section of the Pacific coast of Costa Rica were studied along thirty-six transects done perpendicular to the shore, and by random sampling of subtidal environments, beaches and mangrove forest. Seventy-four species of mollusks belonging to three classes and 40 families were found: 63 gastropods, 9 bivalves and 2 chitons, during this study in 1995. Of these, 16 species were found only as empty shells (11) or inhabited by hermit crabs (5). Forty-eight species were found at only one locality. Half the species were found at one site, Puerto Escondido. The most diverse habitat was the low rocky intertidal zone. Nodilittorina modesta was present in 34 transects and Nerita scabricosta in 30. Nodilittorina aspera had the highest density of mollusks in the transects. Only four transects did not clustered into the four main groups. The species composition of one cluster of transects is associated with a boulder substrate, while another cluster of transects associates with site. Two clusters were not associated to any of the factors recorded. Some species were present in previous studies but absent in 1995, while others were absent in the previous studies but found in 1995. For example, Siphonaria gigas was present in 1995 in many transects with a relatively high density, but absent in 1962, probably due to human predation before the establishment of the park. Including this study, a total of 97 species of mollusks in three classes and 45 families have been reported from Manuel Antonio National Park. Sixty-nine species are new reports for the area: 53 gastropods, 14 bivalves and 2 chitons. There are probably more species of mollusks at Manuel Antonio National Park, than the 97 reported here, because some areas have not been adequately sampled (e.g., deep environments) and many micro-mollusks could not be identified.

Animals↗
PubMed2000

[Surgical treatment of high anorectal and rectovaginal fistulas with the use of transanal endorectal advancement flaps].

INTRODUCTION: Sphincterotomy can be avoided in the repair of high anorectal or rectovaginal fistulas by use of rectal advancement flaps. METHODS: Between 1986 and 1998, 22 patients with high anorectal and 15 patients with rectovaginal fistulas underwent fistulectomy without sphincterotomy and consecutive transanal rectal advancement flap repair. RESULTS: Primary healing was achieved in 81% (30/37 patients). There was no disturbance of continence though anal resting pressures decreased postoperatively. Recurrences occurred in 4 of 12 patients with Crohn's disease (2 anorectal, 2 rectovaginal) and in 1 patient with traumatic anorectal fistula. There were no recurrences in patients with cryptoglandular disease, while the operation failed in 2 patients with ergotamine-induced fistulas. CONCLUSIONS: This operative approach achieves a high primary healing rate with optimal functional outcome. Despite good results the indication should be set carefully in patients with Crohn's disease.

Adult↗
PubMed2000

[Risk factors for anastomosis dehiscence after very deep colorectal and coloanal anastomosis].

INTRODUCTION: Very low colorectal anastomoses are considered to be more prone to complications than other anastomoses. We aimed to analyze possible risk factors for the surgically most relevant complication, anastomotic leakage. METHODS: Uni- and multivariate analysis of the relation between leakage and 18 patient- and procedure-dependent variables were performed in 98 patients after very low colorectal or coloanal anastomosis. RESULTS: In all, 18 patients developed a dehiscence. Two patients, both without a protective stoma, died because of the leakage (overall mortality 2%). From all analyzed variables, only smoking remained as an independent risk factor for anastomotic dehiscence. For all other parameters, such as protective stoma, experience of the surgeon, stage of tumor, radiation therapy, or the need for blood transfusions there was no significant correlation. CONCLUSIONS: From our study, a typical risk pattern for anastomotic dehiscence, with the exception of being a smoker, cannot be defined. Presumably, anastomotic leakage is being caused by a multitude of factors, such as a preexisting or intra-/postoperatively developing reduction of microperfusion, which have a strong influence but cannot be as readily evaluated as other parameters. Until this situation improves, protective stomata, which do not prevent leakage but attenuate the consequences, should be used regularly.

Adult↗
PubMed2000

Endoscopic ultrasonography in the preoperative staging of gastric cancer: accuracy and impact on surgical therapy.

BACKGROUND: Endoscopic ultrasonography (EUS) is a standard procedure in the preoperative staging of patients with gastric carcinomas. Herein we present our experience with EUS and discuss the results and their implications for surgical therapy. METHODS: A total of 116 patients with histologically confirmed gastric adenocarcinoma were referred to EUS and classified prospectively by the TNM system. The results of the preoperative endosonographic staging were compared with the definitive histopathological results after the operation. RESULTS: The overall accuracy of EUS for determination of the T stage was 78%. The accuracy for the T1 and T2 stages was 80% and 63%, respectively. With 20% and 30%, there was a relatively high rate of overstaging in these cases. The accuracy for T3 and T4 tumors was 95% and 83%, respectively. The accuracy of EUS for determination of the N stage was 77%, with a sensitivity of 91% and a specificity of 84%. Resectability was predicted correctly with a sensitivity of 94% and a specificity of 83%. CONCLUSIONS: Generally accepted standards for the therapy of advanced gastric carcinomas do not exist. In cases where the therapeutic strategy is surgical exploration, no preoperative staging is necessary. In cases with differentiated treatment strategies, the accuracy of EUS is not sufficient for the selection of patients for endoscopic resection. Its accuracy for submucosal cancer invasion and for the detection of lymph node metastases needs to be further enhanced. If only multimodal therapy is considered, EUS staging seems to be absolutely mandatory. Patients classified preoperatively as T1 to T3 can be operated on primarily with sufficient security. In patients where radical resection of the tumor seems doubtful, we recommend that a diagnostic laparoscopy be performed to confirm the diagnosis.

Adult↗
PubMed2000

Myoelectric and motor activity after proctocolectomy and ileal pouch-anal anastomosis in dogs.

BACKGROUND: The aim of this study was to investigate the motor function of the ileoanal pouch and to evaluate its coordination with proximal small-intestine motility. METHODS: Proctocolectomy and ileal J pouch-anal anastomosis were performed in 12 dogs. Motility was recorded by serosal electrodes and strain gauge transducers. RESULTS: Transmission of the migrating motor complex (MMC) on the pouch appeared in only 37 of 109 measurements. On the ascending limb there was a constant irregular activity with no MMC detectable. Motility pattern of the pouch did not change postprandially. Spontaneous defecation always appeared independently from MMC transmission without an increase of electrical or mechanical activity or endoluminal pouch pressure. CONCLUSIONS: Ileal pouch motility is independent from motility patterns of the proximal intestine. Its random contractile activity might provide storage function and make the pouch act as a functional reservoir. Intrinsic pouch motility is not responsible for pouch evacuation under physiologic conditions.

Animals↗
PubMed2000

Effect of artificial valves on intestinal adaptation in the short-bowel syndrome: an integrated study of morphological and functional changes in rats.

Two-third-resections of the proximal or distal small bowel with and without artificial valves were performed in rats. Intestinal adaptation led to a significant increase in bowel diameter, villus height and villus diameter and consequently in absorptive mucosal surface area per unit of serosal area. Additional artificial valve construction did not affect the calculated mucosal surface area after proximal resection, while it significantly decreased the absorptive area by the occurrence of large, plump villi after distal resection. There was no change in small-intestinal absorption of water, glucose and electrolytes per unit mucosa with valve construction. DNA cytometry showed that artificial valves led to mucosal hyperplasia without hypertrophy. These morphological changes coincided with a significant increase in basal and stimulated gastrin release. The body weight was unchanged or even worse in the valve groups than after resection alone, despite a significantly prolonged transit time. Therefore, in our study, artificial valves did not result in functional improvements after small intestinal resections.

Adaptation, Physiological↗
PubMed2000

Prediction accuracy and financial savings of four screening tests for a sequential test of clinical performance.

BACKGROUND: Sequential testing of clinical performance is an effective strategy to reduce cost of testing. PURPOSE: To evaluate prediction accuracy and financial savings of 4 screening tests of clinical performance. METHODS: Screening tests were created from a 13-case examination taken by 434 medical students at 4 schools. Regression analysis determined prediction accuracy for 2 test outcomes. Financial savings were computed from published estimates. RESULTS: Zero false passes were obtained with the "Total Number of Cases Passed" screening test, but it saved only 27%. Sixty-two percent savings with 5% false passes occurred with the "Classification" screening test. The "Scale" and "Mini Test" screening tests would have excused 79% and 67% examinees with 5% and 1% false passes, respectively. CONCLUSIONS: Prediction accuracy varies with screening test and outcome measure. Sequential testing of clinical performance can save 40% to 60% with low false pass rates. However, programs need to consider loss of information for curriculum and individual feedback relative to financial savings.

Clinical Competence↗