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Biomedical subjects

G W Clark

Publications and source records attributed to G W Clark.

At least 19 recordsLinked to original sources
PubMed2004

Computer-assisted total knee replacement. A controlled cadaver study using a multi-parameter quantitative CT assessment of alignment (the Perth CT Protocol).

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject's legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiation dose was 2.7 mSV. The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation.

Arthroplasty, Replacement, Knee↗
PubMed2001

Combined laparoscopic/endoscopic anvil placement for the performance of the gastroenterostomy.

BACKGROUND: We developed the laparoscopic gastric bypass in 1993 and first reported the technique and results in 1994. The technique for the gastroenterostomy was derived from the method used in the percutaneous endoscopic gastrostomy tube placement. Some have questioned the safety of this technique, and alternatives have been proposed. METHOD: Prospectively, we have followed and recorded the results of our laparoscopic patients. To date we have performed over 1,400 laparoscopic gastric bypass operations using the same technique of anvil placement: pulling the anvil down from the mouth to the stomach pouch with a percutaneously placed wire. All patients underwent upper GI endoscopy following the anvil placement, and a water-soluble upper GI series was obtained on the first postoperative day. RESULTS: There have been no esophageal injuries in the first 1400 patients on whom this technique was done. CONCLUSION: The percutaneous pull-wire technique is a safe and effective method to place the 21-mm circular stapler anvil for the performance of a laparoscopic gastroenterostomy.

Gastroenterostomy↗
PubMed2000

Laparoscopic gastric bypass, Roux-en-Y- 500 patients: technique and results, with 3-60 month follow-up.

BACKGROUND: The authors have performed the laparoscopic gastric bypass since 1993 and perform about one-half of bariatric cases laparoscopically. Since our initial report, several groups throughout the world have preformed the gastric bypass laparoscopically, with various modifications. METHOD: Prospectively, we followed and recorded the results of our laparoscopic patients. A detailed pre- and post-operative analysis of the patient's co-morbidities is performed as well as complete weight and laboratory data evaluation. RESULTS: With > 80% follow-up, we found an excess weight loss of about 80% by the first year. This degree of loss is well sustained. Over 95% of the significant pre-operative co-morbidities are controlled. CONCLUSION: The laparoscopic gastric bypass has been refined over 5 years of use. Though we have not changed the basic operation as we originally described, others have modified the various anastomotic techniques. The weight loss results are very good to excellent, with patients now out to "long-term" follow-up. Resolution of the co-morbidities is documented. The operation has an adequate track record to show effectiveness, and training programs should be established to maximize safety.

Anastomosis, Roux-en-Y↗
PubMed1999

Peer-reviewed publication following presentation at a regional surgical meeting.

OBJECTIVES: The aim of the study was to investigate the proportion of publications arising from work presented at a regional surgical meeting. DESIGN: A list of all presentations to the Welsh Surgical Society 1983-95 was compiled and a detailed search made of the Medicine Database. The surgical topic of each presentation, the date of presentation, the date of publication and the journal of publication were recorded. SETTING: University Hospital of Wales. RESULTS: Four hundred and ninety-six papers were presented to the society, of which 402 (81%) were by trainees. The most frequent topics of presentation were colorectal (15%), vascular (15%) and hepato-pancreatico-biliary (11%). Two hundred and thirty-three papers (47%) have been published in peer-reviewed journals. The most popular journals for publication were Annals of the Royal College of Surgeons of England (19%), British Journal of Surgery (16%) and Journal of the Royal College of Surgeons of Edinburgh (8%). The median time from presentation to publication was 17.0 months (interquartile range 10.0-27.5 months). CONCLUSIONS: Regional surgical meetings have an important role in the annual surgical calendar and they are the ideal initial setting for presentation by trainees.

Education, Medical, Continuing↗
PubMed1999

Endosonographic staging of 100 consecutive patients with esophageal carcinoma: introduction of the 8-mm esophagoprobe.

Endoscopic ultrasound of esophageal carcinoma is conventionally performed using the 13-mm fiberoptic/ultrasound echoendoscope. However, the large diameter results in an inability to negotiate the primary tumor in 25% of patients. The aim of this study was first to determine whether use of the 8-mm esophagoprobe would overcome this problem and second to evaluate the accuracy of the smaller diameter instrument. One hundred consecutive patients with esophageal cancer underwent initial gastroscopy. Based upon the degree of luminal stenosis, patients were staged with either the conventional echoendoscope (luminal diameter > or = 15 mm) or the esophagoprobe (luminal diameter < 15 mm). The primary tumor was successfully negotiated in all subjects (echoendoscope 30, esophagoprobe 70) so that T- and N-staging was accomplished in every patient. Esophageal dilatation was performed in 12 patients (12%). The procedure was well tolerated and there were no complications, in particular no patient suffered esophageal perforation. The accuracy of the esophagoprobe for T-staging was 90% (19 out of 20) and that for N-staging was 75% (15 out of 20). This was similar to the accuracy of staging with the conventional echoendoscope, 90% (9 out of 10) for T-stage and 90% (9 out of 10) for N-stage. The esophagoprobe can safely and accurately stage patients with esophageal carcinoma, including those with high-grade stenoses.

Adult↗
PubMed1999

The antioxidant profiles of patients with recurrent acute and chronic pancreatitis.

OBJECTIVE: It has been suggested that patients with chronic pancreatitis have antioxidant deficiencies. It is unclear whether these antioxidant deficiencies also occur in patients with recurrent acute pancreatitis and whether this condition represents an intermediate state between normality and chronic pancreatitis. The aim of this study was to determine the antioxidant profiles of patients with pancreatitis (recurrent acute and chronic) and to compare their profiles with a control population. METHODS: The antioxidant profiles of patients with chronic pancreatitis (n = 27) and recurrent acute pancreatitis (n = 11) were determined and compared with the antioxidant profiles of control subjects (n = 19). The following parameters were measured in blood: trace elements (selenium, copper, zinc), vitamins A and E, and carotenoids (alpha-carotene, beta-carotene, xanthine, beta-cryptoxanthine, lycopene). RESULTS: Patients with chronic pancreatitis had significantly lower plasma concentrations of selenium, vitamin A, vitamin E, beta-carotene, xanthine, beta-cryptoxanthine, and lycopene compared with both control subjects and patients with recurrent acute pancreatitis (p < 0.05). There were no significant differences between the antioxidant profiles of patients with chronic pancreatitis due to alcohol excess and patients with idiopathic chronic pancreatitis, or between the antioxidant profiles of patients with recurrent acute pancreatitis and control subjects. CONCLUSIONS: Patients with chronic pancreatitis had evidence of multiple antioxidant deficiencies. The antioxidant profiles of patients with recurrent acute pancreatitis did not differ from those of control subjects, discounting the hypothesis that recurrent acute pancreatitis represents an intermediate state between normality and chronic pancreatitis.

Acute Disease↗
PubMed1999

Patterns of gastritis in patients with gastro-oesophageal reflux disease.

BACKGROUND: The cause of inflammation in cardiac mucosa at the gastro-oesophageal junction (GOJ) is unclear, both gastro-oesophageal reflux disease (GORD) and Helicobacter pylori having been implicated. AIMS: To describe patterns of gastritis in patients with symptomatic GORD. METHODS: In 150 patients (126 normally located Z-line, 24 Barrett's oesophagus) with symptoms of GORD, biopsies were taken of the GOJ, corpus, and antrum. Inflammation was assessed using the updated Sydney System. RESULTS: For the 126 patients with a normally located Z-line, biopsies of the GOJ revealed cardiac mucosa in 96, fundic mucosa in 29, and squamous mucosa in one. Inflammation in glandular mucosa at the GOJ was present in 99/125 specimens (79%), including 87/96 (91%) with cardiac mucosa and 12/29 (41%) with fundic mucosa. Inflammation in fundic mucosa was closely related to H pylori and active inflammation was only seen in its presence. Inflammation in cardiac mucosa was less closely linked to H pylori. When H pylori was present in cardiac mucosa (28/96, 29%) active inflammation was usually present (25/28, 89%). However, active inflammation was also found in 34/68 (50%) cardiac mucosa specimens without H pylori. Overall, 28/87 (32%) biopsies with carditis were colonised with H pylori and 59/87 (68%) were not. In H pylori colonised patients, inflammation was seen throughout the stomach, while in non-colonised patients, it was confined to cardiac mucosa. CONCLUSIONS: Patients with symptomatic GORD had a high prevalence of carditis. This was of two types, H pylori associated and unassociated. Except on Giemsa staining, the two were morphologically identical, suggesting mediation by a similar immunological mechanism.

Adult↗
PubMed1999

Outcome of oesophagogastric carcinoma in young patients.

The survival of young patients (< or = 50 years of age) with carcinoma of the oesophagus or stomach has been reported to be poorer than that of their older counterparts. The aim of the current study was to review the outcome of such young patients with oesophagogastric cancer and to compare the outcome in patients with carcinoma of the oesophagus/cardia with patients with carcinoma of the more distal stomach. The study population was 50 patients. Tumour location was oesophagus/cardia (n = 33) and gastric body/antrum (n = 17). The most common presenting symptoms were weight loss (66%), epigastric pain (54%), dysphagia (50%), and heartburn (40%). Seventeen patients had experienced foregut symptoms for a period of > or = 6 months. These patients were more likely to have symptoms of gastro-oesophageal reflux disease and to have received acid suppression therapy than patients with shorter symptom durations. Only 20 patients underwent a potentially curative resection, while 10 underwent open and close laparotomy. The overall median survival was 7 months and the 5-year survival was 8%. Multivariate analysis revealed that surgical resection and UICC stage were the only factors that significantly influenced survival. There was no difference in the survival of patients with proximally situated tumours compared to those with distally located tumours. Wide variations in clinical practice were seen between different surgeons. Consequently, a multidisciplinary team designed to manage all patients with oesophagogastric cancer according to nationally agreed protocols has been established in our hospital. Earlier diagnosis of these tumours is to be encouraged, even if this necessitates the more liberal use of endoscopy in the evaluation of young patients with persistent foregut symptoms.

Adult↗
PubMed1998

Laparoscopic gastric bypass for morbid obesity in a patient with situs inversus.

The purpose of this article is to discuss the operative challenges posed by the advanced laparoscopic approach to a patient with situs inversus. The patient is a morbidly obese woman who has multiple co-morbidities related to her weight and who presented for bariatric surgery. A laparoscopic gastric by-pass was successfully performed. Situs inversus totalis is not a contraindication for laparoscopic surgery.

Adult↗
PubMed1998

Pregnancy following gastric bypass for morbid obesity.

BACKGROUND: Women who suffer from morbid obesity are often infertile. If these women are able to become pregnant, they are considered high risk because of the hypertension, diabetes and other associated risk factors. Following the pregnancy is difficult due to limitations of the physical examinations. More costly ultrasound examinations are needed at a higher frequency. Bariatric surgery reduces the woman's weight and the incidence of obesity related co-morbidities. The number of pregnancies and rate of complications during those pregnancies in our post-bariatirc surgical patients were evaluated. METHOD: Our group has been doing bariatric surgery since the early 1980s. We have over 2000 active patients on our current newsletter mailing list. The patients also have a series of networks through support groups. The patients are informed to contact us when they become pregnant so we may assist the obstetrician with their care. Through these various means, we have been able to identify 41 women in our patient population who have become pregnant. Using personal interview, questionnaire, and review of perinatal records, pregnancy-related risks and complications were studied. RESULTS: With over a 95% follow-up rate on the patients identified as having been pregnant following surgery, we found less risk of gestational diabetes, macrosomia, and cesarean section than associated with obesity. There were no patients with clinically significant anemia. CONCLUSION: Since the patients had an operation that restricts their food intake, some basic precautions should be taken when they become pregnant. With this in mind, our patients have done well with their pregnancies. The post-surgical group had fewer pregnancy-related complications than did an internally controlled group that were morbidly obese during their previous pregnancies.

Female↗
PubMed1997

Barrett's esophagus. The significance of p53 in clinical practice.

OBJECTIVE: The authors provide an updated review the molecular biology of the p53 tumor suppressor gene with reference to its role in the malignant degeneration of Barrett's esophagus. SUMMARY BACKGROUND DATA: Appreciation of the function of the tumor suppressor gene p53 has given new insight into regulation of the cell cycle, and the gene appears to play an important role in many solid tumors. Esophageal adenocarcinoma is increasing in frequency in the western world at an alarming rate and is unique because there is a clear metaplasia (Barrett's mucosa)/ dysplasia/carcinoma sequence. p53 malfunction arises as an early event in this carcinogenic process and has been demonstrated in patients with nondysplastic Barrett's metaplasia. The possible causes of p53 malfunction in this setting are discussed. The most reliable method for the detection of p53 mutations is DNA sequencing. p53 immunohistochemistry appears too insensitive to act as a reliable marker for the presence of a mutation and cannot be used as a reliable marker for the future development of cancer. CONCLUSIONS: High-grade dysplasia within Barrett's mucosa remains the best clinical predictor of adenocarcinoma. The mutational spectrum observed in these tumors should provide clues to their etiology.

Adenocarcinoma↗
PubMed1996

Carcinoma of the oesophagus: the time for a multidiciplinary approach?

Oesophageal cancer is one of the most lethal carcinomas, with 5-year survival rates of less than 5%. This is due to a combination of factors including late presentation, associated cardiac and respiratory disease, and the technical difficulties of resectional surgery. The outcome for patients with oesophageal cancer has changed little in recent years, perpetuating a pervading attitude of pessimism in the surgical community. The epidemiology of oesophageal cancer is changing with the increasing incidence of adenocarcinoma. Most of these tumours arise in the setting of Barrett's oesophagus and chronic gastro-oesophageal reflux disease. Survival following surgery for oesophageal cancer is determined by several independent factors, most notably the pathological stage of the disease and the patients physiological status. However, in patients with limited disease, in particular patients with less than five lymph node metastases, the extent of the nodal dissection positively impacts survival. This article reviews the changing epidemiology of oesophageal cancer, focusing on the need for early diagnosis and the selection of patients for surgery. It places emphasis on the importance of integrating surgical therapy in a multidisciplinary team approach to the management of such patients.

Adenocarcinoma↗
PubMed1996

Gastric juice protects against the development of esophageal adenocarcinoma in the rat.

OBJECTIVE: The authors investigate the effects of gastric juice on tumorigenesis in a rat model of esophageal adenocarcinoma. SUMMARY BACKGROUND DATA: In rats treated with the carcinogen methyl-n-amyl nitrosamine, squamous cancer of the esophagus develops in a time- and dose-dependent manner. When methyl-n-amyl nitrosamine treatment is preceded by an operation to induce reflux of duodenal and gastric juice into the esophagus, there is an increased yield of esophageal tumors, many of which are adenocarcinomas. When only gastric juice refluxes into the esophagus, the tumor yield is less and adenocarcinomas are not found. METHODS: Two hundred seventy 8-week old Sprague-Dawley rats were studied. Twenty unoperated rats served as controls. The remaining rats underwent the following operations: esophagoduodenostomy with gastric and vagal preservation to induce duodenogastroesophageal reflux (n = 48); esophagoduodenostomy with antrectomy and Billroth 1 reconstruction to produce reflux of duodenogastric juice with the exclusion of the antrum (n = 53); esophagoduodenostomy with proximal gastrectomy to induce hypergastrinemia and reflux of duodenogastric juice with exclusion of the body and forestomach (n = 51); esophagoduodenostomy plus total gastrectomy to produce reflux of duodenal juice alone (n = 50); and esophagoduodenostomy with vagal and gastric preservation but with division of the duodenum just beyond the pylorus and reimplantation into the jejunum, 13 cm distal to the esophagoduodenostomy. This produced reflux of duodenal juice with gastric juice diverted downstream, (n = 48). At 10 weeks of age, all rats were given 4 weekly doses of carcinogen (methyl-n-amyl nitrosamine, 25 mg/kg intraperitoneally), and survivors were killed at 36 weeks of age. RESULTS: The prevalence rate of esophageal adenocarcinoma was 30% in rats with duodenogastroesophageal reflux and 87% in rats with reflux of duodenal juice alone. Fifty-six percent of rats with reflux of duodenogastric juice with exclusion of the antrum and 72% of rats with reflux of duodenogastric juice with the exclusion of the body and forestomach developed adenocarcinoma, showing a progression increase in the prevalence of adenocarcinoma as less gastric juice was permitted to reflux with duodenal juice into the esophagus. CONCLUSION: In this rat model, the presence of gastric juice in refluxed duodenal juice against the development of esophageal adenocarcinoma. The protective effect appears to be due to acid secretion from the stomach. Continuous profound acid suppression therapy may be detrimental by encouraging esophageal metaplasia and tumorigenesis in patients with duodenogastroesophageal reflux.

Adenocarcinoma↗