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Biomedical subjects

K L Chan

Publications and source records attributed to K L Chan.

At least 181 records · Page 10Linked to original sources
PubMed1993

Spontaneous rupture of renal tumours presenting as surgical emergency.

A study of renal tumours filed in the pathology department of a regional hospital in Hong Kong during 1971-1990 showed 6 cases of surgical emergency due to spontaneous rupture of the kidney by tumour. All occurred as a complication of renal angiomyolipoma, a rare tumour or hamartoma. A literature review showed that the renal tumour most frequently reported to cause spontaneous rupture was renal carcinoma. Chinese patients appear to have more renal ruptures due to angiomyolipoma than to renal carcinoma. It is proposed that intra-operative frozen section diagnosis should be sought, when this can be safely performed, in cases of rupture of the kidney by tumour. Surgery aiming at conserving functional renal parenchyma is appropriate for benign lesions such as angiomyolipoma.

Adult↗
PubMed1993

Progression of aortic valve dysfunction in 51 adult patients with congenital bicuspid aortic valve: assessment and follow up by Doppler echocardiography.

OBJECTIVE: To assess the pattern and progression of aortic valve dysfunction by serial Doppler echocardiographic examinations in ambulatory adult patients with congenital bicuspid aortic valve. DESIGN AND SETTING: Retrospective analysis of patients referred for Doppler echocardiography over a four year period. SUBJECTS: Fifty one adult patients with echocardiographic diagnosis of congenital bicuspid aortic valve had serial Doppler echocardiographic studies at least six months apart. There were 40 men and 11 women with a mean age of 36 years. MAIN OUTCOME MEASURE: Doppler echocardiographic values of aortic valve dysfunction. Cardiac events including endocarditis and aortic valve replacement were also evaluated. RESULT: Coarctation was present in five patients. 31 (61%) patients had a functionally normal bicuspid aortic valve defined as a mean gradient < 25 mm Hg and mild regurgitation. Significant aortic regurgitation was present in 15 patients (moderate in 12 and severe in three). Three patients had isolated aortic stenosis and two patients had combined aortic valve dysfunction. At a median follow up of 21 months (range six to 46 months), six patients had aortic valve surgery (one for aortic stenosis, three for aortic regurgitation, and two for endocarditis). Only 22 patients (43%) continued to have a functionally normal aortic valve. CONCLUSION: In this cohort of fairly young patients, aortic regurgitation is more common than aortic stenosis. Progression of aortic valve dysfunction occurs in patients with pre-existing valve dysfunction and even in those with normal aortic valve function at the initial echocardiographic examination.

Adult↗
PubMed1993

Complementary role of transoesophageal echocardiography to coronary angiography in the assessment of coronary artery anomalies.

OBJECTIVE: To examine the role of transoesophageal echocardiography in the assessment of patients with coronary artery anomalies. BACKGROUND: Coronary artery anomalies are difficult to detect clinically. Most are benign but some may produce symptoms that can be life threatening. Until recently the non-invasive assessment of coronary artery anomalies has been limited. METHODS: The data base of transoesophageal echocardiographic studies performed between September 1988 and April 1991 were reviewed to identify all cases of coronary artery anomalies. There were six patients with such anomalies who had also had coronary angiography. The findings of these two imaging techniques were analysed to determine whether transoesophageal echocardiography added useful data in these cases. RESULTS: Of the six patients, the coronary anomaly was discovered during angiography in four patients, during a transthoracic echocardiographic study in one patient, and as an incidental finding in the other patient. Aberrant origins of the left coronary artery were detected in two patients, and coronary artery fistulae were present in the other four. Transoesophageal echocardiography provided unique information on the course of an aberrant left coronary artery in one patient and the precise location of drainage sites of coronary artery fistulas in three patients. CONCLUSION: Transoesophageal echocardiography was complementary to angiography in the assessment of coronary artery anomalies. It can locate and delineate the course of an ectopic coronary artery and the drainage site of a coronary fistula. These anatomical data can be crucial to the management of these patients.

Adult↗
PubMed1993

Control of Mansonia mosquitos, vectors of brugian filariasis in Sarawak, Malaysia.

Two field trials in the control of subperiodic brugian filariasis vectors, mainly Mansonia bonneae and Mansonia dives were carried out in Sarawak, East Malaysia. In the first trial, malathion ultra-low volume (ULV) spray was used to control the Mansonia mosquitos in two filariasis endemic villages. Six spray rounds were applied at biweekly intervals at Kampung Rasau and two spray rounds were applied at monthly intervals in Kampung Triboh. ULV malathion spray reduced biting Ma. bonneae population for 3 days after spraying. The biting density decreased to 50% of the pre-treatment level by the 12th - 13th day and reached the pre-treatment level by the 24th - 25th day. Contact bioassay tests on caged Mansonia mosquitos revealed considerable penetration of the malathion aerosol indoors and relatively adequate coverage outdoors. The estimated number of bites per case per day was 1.09 to 4 times less in the sprayed kampung than in an unsprayed control kampung. The parous and daily survival rates of Mansonia mosquitos were not significantly affected by the spraying. In a second trial, chemotherapy with diethylcarbamazine citrate (DEC) was combined with vector control through indoor residual spraying in Kampung Ampungan. The results were compared with the use of only DEC mass treatment in Kampung Sebangkoi and Kampung Sebamban. The combined control measures in Kampung Ampungan reduced the MfD-50 to 44% of the pre-treatment level over a period of 4 years. In the other two kampungs where only mass DEC therapy was applied, the microfilarial rate and MfD-50 declined significantly in the second blood survey but increased gradually in two subsequent follow-up blood surveys. The total insecticidal impact for Ma. bonneae was 3.9 to 1 indoors and 2.7 to 1 outdoors. These results indicated that quarterly pirimiphos-methyl indoor spraying used in integrated control could reduce indoor transmission by 3.9 times. The infective rate from the Ma. bonneae dissected in all three kampungs after the interventions, irrespective of DEC treatment alone or in combination with pirimiphos-methyl residual spraying were reduced by two fold. However the infection rate of brugian filarial larvae in Kampung Ampungan was significantly reduced after the use of DEC and insecticide. Annual Transmission Potential (ATP) showed a high significant reduction in Kampung Ampungan (p > 0.001) compared with Kampungs Sebangkoi and Schambam. In Ampungan, the ATP was reduced by 8.5 times indoors after the MDA and insecticidal application and 3 times outdoors. The reduction rate for Sebangkoi and Sebamban both indoors and outdoors were less than 2 fold.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Ulcerative colitis and antineutrophil cytoplasmic antibodies in Hong Kong Chinese.

Inflammatory bowel diseases are known to be rare among the Chinese. The diagnosis of ulcerative colitis has been difficult in some of the Asian countries where infective colitis is more prevalent. Twenty-three Hong Kong Chinese patients diagnosed to have ulcerative colitis were reviewed. The symptoms were relatively mild and extraintestinal manifestation had been rare. Patients responded well to steroid therapy and sulfasalazine. Three patients in this series were found to have cyst and/or trophozoites of Entamoeba histolytica in stool. In this series, 19 patients were tested for antineutrophil cytoplasmic antibody (ANCA). Fourteen patients (73.5%) were positive, of which six (31.5%) showed a perinuclear staining pattern and eight (42%) demonstrated a cytoplasmic pattern. Five patients (26.5%) were negative for any ANCA, and none was positive for both. Sera of these patients were also tested for anti-alpha granules, anti-myeloperoxidase, and anti-lactoferrin activities. None was positive. Control sera collected from 16 patients with irritable bowel syndrome were all negative for the tests. In conclusion, testing of ANCAs may help in making the diagnosis of idiopathic inflammatory bowel disease in difficult situations.

Adult↗
PubMed1992

Transesophageal echocardiographic diagnosis of right-sided cardiac masses in patients with central lines.

Transesophageal echocardiography provides excellent images of intracardiac masses; however, its use among a series of patients with central venous lines has not been fully described. Nineteen patients (aged 52 +/- 16 years; 10 women) had masses detected by transesophageal echocardiography in the presence of a permanent (0.2 to 16 years) pacing wire (n = 8), and a current (n = 9) or recent (n = 2) (1 to 281 days) indwelling catheter. Transthoracic echocardiography suggested the presence of a mass in 5 patients (26%), although in only 2 cases were its findings consistent with transesophageal findings. Transesophageal echocardiography indicated the presence of a mass in or near the superior vena cava in 13 patients, in the right atrium in 6, and adjacent to the tricuspid valve in 3. Discrete masses measured 1.6 +/- 2.1 cm2 in area during transesophageal echocardiography. Eleven patients had positive blood cultures, 7 with staphylococcal species. Mass size was not significantly altered by the type of line or sepsis, but showed a weak correlation with line age (r = 0.56). Transesophageal echocardiography altered the management of 9 patients, prompting surgery (n = 3) and line removal (n = 3), and antibiotic (n = 2) or anticoagulation (n = 3) therapy.

Adult↗
PubMed1992

Impact of transesophageal echocardiography on the treatment of patients with aortic dissection.

To determine the impact of transesophageal echocardiography (TE) on the treatment of patients with aortic dissection, the clinical course and outcome of 18 patients with TE diagnosis of dissection were analyzed. Ascending aortic dissection was present in nine patients, of whom six had surgery with confirmation of TE findings. Angiography was performed in only two of these patients and was falsely negative in one patient. Angiography was not performed in the three patients who were not surgical candidates. In the nine patients who had descending aortic dissection, angiography was performed in seven patients, of whom two underwent surgery. Information provided by angiography did not change the treatment of these patients. Thus, TE provides a prompt and accurate diagnosis in aortic dissection obviating the need for angiography in most patients.

Adult↗
PubMed1991

Comparison of accuracy of transesophageal versus transthoracic echocardiography for the detection of mitral valve prolapse with ruptured chordae tendineae (flail mitral leaflet).

The accuracy of transesophageal echocardiography was compared with that of transthoracic echocardiography in the detection of ruptured chordae tendineae (flail mitral leaflet) in 27 patients with mitral valve prolapse (MVP) who underwent valve repair or replacement for mitral regurgitation. Confirmation of the presence of ruptured chordae resulting in a flail leaflet was available at surgery in all cases. The echocardiographic studies were read blindly by 2 independent observers with any differences resolved by a third. Mean (+/- standard deviation) age was 63 +/- 13 years. Men (n = 20) outnumbered women (n = 7) (p less than 0.02), and tended to be younger (p = 0.06). Flail leaflets were identified in 20 of 27 patients. In 1 patient, both leaflets were involved and in the remaining 19 patients posterior leaflets (15 patients) were more frequently affected than anterior leaflets (4 patients). Transesophageal echocardiography correctly identified all 20 patients with flail leaflets, but 1 false positive study occurred among the 7 patients without a flail leaflet. In contrast, transthoracic echocardiography identified only 12 of 20 patients with flail leaflets, with no false positive studies. Transesophageal echocardiography was more accurate, correctly classifying 26 of 27 (96%) cases versus 19 of 27 (70%) by the transthoracic approach (p less than 0.01). This study suggests a higher incidence of chordal rupture to the posterior leaflet in patients with MVP and demonstrates improved accuracy of transesophageal over transthoracic echocardiography in the detection of flail leaflets.

Aged↗
PubMed1991

Genetics and polymorphism of a duplicated malate dehydrogenase (MDH) locus in the grasshopper Oxya japonica japonica (Orthoptera:Acrididae:Oxyinae).

A biochemical genetic study of the enzyme malate dehydrogenase (MDH) was conducted in the grasshopper Oxya j. japonica. Analysis of MDH electrophoretic variation in this species of grasshopper shows that one of the two autosomal loci for MDH in grasshoppers, the Mdh-2 locus, controlling the anodal set of MDH isozymes, is duplicated. Results of breeding studies confirm this and the observed polymorphism at the Mdh-2 locus in the two populations of Oxya j. japonica studied can be attributed to three forms of linked alleles at the duplicated locus in equilibrium in both populations. In this respect, all individuals of this species possess heterozygous allelic combinations at the duplicated Mdh-2 locus, which may account for the spread of the duplicated locus in the populations of this species of grasshopper.

Alleles↗
PubMed1991

Usefulness of transesophageal echocardiography in the diagnosis of conditions mimicking aortic dissection.

Between September 1987 and April 1989, forty patients suspected to have aortic dissection were evaluated by transesophageal echocardiography. Aortic dissection was identified in 18 patients. This study evaluated the ability of transesophageal echocardiography in the assessment of the 22 patients in whom aortic dissection was not found. A range of pathologic conditions was diagnosed in these patients. Five patients had ischemic heart disease when they were initially seen. Among the remaining 17 only one patient had a normal aorta. Aortic disease was present in the other 16 patients with aortic dilatation in 10. Atheromas were detected in seven patients with concomitant aortic dilatation in five of them. An extrinsic aortic mass was present in two patients. Transesophageal echocardiography correctly identified an anastomotic leak at the site of left coronary artery implantation in a patient with a recent Bentall procedure, and a large mobile clot within the proximal descending aorta in a patient with blunt chest trauma. These findings obviated the need for other tests in 15 patients and led to surgery in four with no ancillary tests performed in three of them. Thus transesophageal echocardiography has an important role in assessing patients with suspected dissection. Aortic disease is common even in patients in whom aortic dissection is excluded, and some of the conditions can be just as life-threatening as dissection. Transesophageal echocardiography not only reliably identifies dissection but can also detect luminal and extraluminal diseases not adequately visualized by other modalities.

Adult↗
PubMed1991

Incidence of bacteremia in transesophageal echocardiography: a prospective study of 140 consecutive patients.

The incidence of bacteremia related to transesophageal echocardiography was studied in 140 consecutive patients (71 women and 69 men with a mean age of 53.7 +/- 15 years). Thirty-four patients had one or more prosthetic heart valves. Blood cultures were obtained from each patient through separate venipuncture sites immediately before and after transesophageal echocardiography. An additional late blood culture was obtained in 114 patients 1 h later. The skin was cleaned with povidone-iodine and venipunctures were performed with separate butterfly needles with use of sterile gloves and drapes. Blood samples were drawn into separate syringes, transferred to aerobic and anaerobic culture bottles and processed with use of a semiautomated system. The overall incidence of blood cultures positive for bacteremia was 2% (8 of 394 bottles) and all positive cultures grew in a single blood culture bottle. Positive cultures occurred in 4 (1.4%) of 280 bottles before the procedure, in 2 (0.7%) of 280 bottles immediately after the procedure and in 2 (0.9%) of 228 late (1-h) blood culture bottles. Bacterial isolates were coagulase-negative staphylococci (n = 5), Propionibacterium (n = 2) and Moraxella (n = 1). All were considered contaminants. Mean endoscopic time in these patients was not significantly different from that in the other patients. Follow-up of patients with a blood culture positive for bacteremia revealed no clinical evidence of systemic infection. It is concluded that 1) the incidence of bacteremia related to transesophageal echocardiography is very low, and 2) the incidence of blood cultures positive for bacteremia after transesophageal echocardiography is indistinguishable from the anticipated contamination rate.

Adult↗
PubMed1991

Role of transesophageal echocardiography in the diagnosis and management of prosthetic valve thrombosis.

Thrombosis is a serious complication of heart valve replacement. Diagnosis is often difficult with previously reported techniques, including precordial two-dimensional echocardiography, suffering from low sensitivity and specificity. Management is similarly difficult, with a 40% to 50% reported mortality rate in early surgical series. Three cases are presented in which thrombosis of a left-sided prosthetic valve (one aortic, three mitral) was diagnosed by means of transesophageal echocardiography. All three patients were treated with streptokinase and had clinical and echocardiographic resolution. In one patient, who had recurrent thrombosis and received a second course of streptokinase, the course was complicated by a massive embolic stroke and death. Another patient with a recurrence underwent successful valve replacement. Transesophageal echocardiography is ideal for the diagnosis and follow-up of patients with prosthetic valve thrombosis. Although effective, thrombolysis in this setting is associated with a high risk of thromboembolic phenomena and significant risk of death. Thrombolytic therapy may be considered in highly selected patients who have an unacceptable risk for reoperation.

Adult↗
PubMed1991

Paradoxic air embolism in the absence of an intracardiac defect.

A 58-year-old man experienced paradoxic air embolism with passage of air from the systemic venous to the systemic arterial circulation with subsequent stroke and death. No intracardiac shunt was present. Pulmonary fibrosis concomitant with severe pulmonary arterial hypertension appears to have been responsible for the air traversing the pulmonary capillary bed. This unusual outcome of a complicated central venous catheterization must be borne in mind and guarded against in similar patients.

Catheterization, Swan-Ganz↗