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Biomedical subjects

K W Chan

Publications and source records attributed to K W Chan.

At least 37 records · Page 2Linked to original sources
PubMed2004

Dynamic gadolinium-enhanced magnetic resonance urography for assessing drainage in dilated pelvicalyceal systems with moderate renal function: preliminary results and comparison with diuresis renography.

OBJECTIVE: To evaluate the use of dynamic gadolinium diethylenetriaminepenta-acetic acid (DTPA)-enhanced magnetic resonance urography (Gd-MRU) for assessing kidneys with markedly dilated pelvicalyceal systems and impaired function. PATIENTS AND METHODS: Eight children (mean age 30 months, sd 25) were assessed, diagnosed as having gross unilateral hydronephrosis with a mean (sd) anteroposterior renal pelvic diameter of 36 (7) mm and reduced (30-40%) renal function. Dynamic Gd-MRU was performed after the patients were pre-loaded with intravenous fluid and diuretics, and comprised a dynamic T1-weighted sequence after Gd-DTPA (0.1 mmol/kg body weight) was administered, with a time-intensity curve of each kidney produced. Drainage was diagnosed by a clearly declining time-intensity curve and direct visualization of contrast medium within the ureter in several frames. High-grade or complete obstruction was diagnosed when drainage of contrast medium could not be detected. Gd-MRU results were compared with diuresis radionuclide (mercapto-acetyltriglycine, MAG3) renography within the same week. Unobstructive units detected by Gd-MRU were treated conservatively with a close follow-up by ultrasonography and radionuclide studies. RESULTS: Diuresis MAG3 renography showed drainage in three dilated units and poor washout in five; in contrast, Gd-MRU showed drainage in seven dilated systems (three showed poor washout by MAG3), and obstruction in the remaining case. The unobstructed units detected by MRU under conservative treatment thus showed no further deterioration of renal function or progressive hydronephrosis in the subsequent follow-up (mean 18 months, range 15-23). CONCLUSION: These preliminary results suggest that dynamic Gd-MRU is a useful noninvasive imaging method in distinguishing obstructive from unobstructive dilated systems, particularly in patients with hydronephrosis and reduced renal function.

Child↗
PubMed2003

Pathogenesis of neonatal necrotizing enterocolitis: a study of the role of intraluminal pressure, age and bacterial concentration.

The pathogenesis of neonatal necrotizing enterocolitis (NEC) is unknown. Intestinal dilatation and preferred occurrence of NEC at sites of bacterial overgrowth (colon and ileum) are common findings. The study attempted to produce NEC with increasing intraluminal pressures and bacterial concentrations in two different aged groups of rats. First, 10-cm terminal ileum segments were isolated with intact vascular pedicles in 1-and 3-month-old rats, and a dose of 10(11) E. coli in 1 ml was injected into each segment. Intraluminal pressure was sustained for 1 h at 150, 100, 50 and 0 cmH(2)0, respectively, in four experimental groups ( n=6). The isolated loop was then returned to the abdominal cavity and assessed grossly for NEC after 24 h. Histological examination was performed by a pathologist (KWC) who was blinded to the procedures. Second, the procedure was repeated with doses of 10(8), 10(5) and 0 bacteria/ml ( n=6) at intraluminal pressure of 100 cmH(2)0 in 1-month-old rats. Third, in another experimental group, oxygenation of the pedicled loop was assessed by oximetry as the intraluminal pressure increased and the findings were correlated with aortic blood pressure. The blood pressures (mean+/-SD) for 3- and 1-month-old rats were 110+/-6 and 72+/-4 mmHg, respectively. Hypoxia (<50% oxygen saturation) of the bowel was detected when the intraluminal pressure exceeded the mean blood pressure. The relative incidences of NEC in the bowel with intraluminal pressure above and below mean blood pressure were 100% (6/6) vs. 4% (1/24; P<0.05) in 3-month-old rats, and 100% (12/12) vs. 11% (2/18; P<0.05) in 1-month-old rats. There was no occurrence of NEC in bowel injected with 10(5) E. coli/ml and less at 100 cm intraluminal pressure. Increased intraluminal pressure results in bowel hypoxia and in the presence of adequate bacterial concentration predisposes to the development of NEC. Young age is associated with a lower threshold for increased intraluminal pressure leading to NEC.

Age Factors↗
PubMed2003

Isolation and characterization of viruses related to the SARS coronavirus from animals in southern China.

A novel coronavirus (SCoV) is the etiological agent of severe acute respiratory syndrome (SARS). SCoV-like viruses were isolated from Himalayan palm civets found in a live-animal market in Guangdong, China. Evidence of virus infection was also detected in other animals (including a raccoon dog, Nyctereutes procyonoides) and in humans working at the same market. All the animal isolates retain a 29-nucleotide sequence that is not found in most human isolates. The detection of SCoV-like viruses in small, live wild mammals in a retail market indicates a route of interspecies transmission, although the natural reservoir is not known.

Amino Acid Sequence↗
PubMed2003

Two-port versus four-port laparoscopic cholecystectomy.

BACKGROUND: Two-port laparoscopic cholecystectomy has been reported to be safe and feasible. However, whether it offers any additional advantages remains controversial. This study reports a randomized trial that compared the clinical outcomes of two-port laparoscopic cholecystectomy versus conventional four-port laparoscopic cholecystectomy. METHODS: One hundred and twenty consecutive patients who underwent elective laparoscopic cholecystectomy were randomized to receive either the two-port or the four-port technique. All patients were blinded to the type of operation they underwent. Four surgical tapes were applied to standard four-port sites in both groups at the end of the operation. All dressings were kept intact until the first follow-up 1 week after surgery. Postoperative pain at the four sites was assessed on the first day after surgery using a 10-cm unscaled visual analog scale (VAS). Other outcome measures included analgesia requirements, length and difficulty of the operation, postoperative stay, and patient satisfaction score on surgery and scars. RESULTS: Demographic data were comparable for both groups. Patients in the two-port group had shorter mean operative time (54.6 +/- 24.7 min vs 66.9 +/- 33.1 min for the four-post group; p = 0.03) and less pain at individual subcostal port sites [mean score using 10-cm unscaled VAS: 1.5 vs 2.8 ( p = 0.01) at the midsubcostal port site and 1.3 vs 2.3 ( p = 0.02) at the lateral subcostal port site]. Overall pain score, analgesia requirements, hospital stay, and patient satisfaction score on surgery and scars were similar between the two groups. CONCLUSION: Two-port laparoscopic cholecystectomy resulted in less individual port-site pain and similar clinical outcomes but fewer surgical scars compared to four-port laparoscopic cholecystectomy. Thus, it can be recommended as a routine procedure in elective laparoscopic cholecystectomy.

Adult↗
PubMed2003

Control of entanglement and the high-entanglement limit.

We examine two-particle entanglement and ways in which it might be coherently controlled. Control is desirable for successful implementation of quantum computing. As one result, we find that reaching very high entanglement may be feasible experimentally.

Journal Article↗
PubMed2003

Intracranial chloroma in hypereosinophilic myelofibrosis.

BACKGROUND: Chloroma, also called granulocytic sarcoma, is a localized extramedullary tumor composed of leukemic myeloid cells. It is a rare tumor that can occur in various locations. The association of chloroma with leukemic disease or myeloproliferative disorders is limited to isolated case reports. CASE DESCRIPTION: We report a case of intracranial chloroma in an elderly man with myelofibrosis and progressive hypereosinophilia. The presence of leukemic cells within his pleural aspirate suggested an incipient acute leukemic state. CONCLUSION: We report the first case of intracranial chloroma associated with hypereosinophilia developing in the course of myelofibrosis. The significance of hypereosinophilia in predicting the likelihood of development of central nervous system chloroma and acute leukemia in a patient with myelofibrosis needs further evaluation.

Acute Disease↗
PubMed2003

The use of a distal occlusion balloon protection device in acute coronary syndrome.

We report our early experience in using the PercuSurge GuardWire Plus system as a distal protection device in patients with acute coronary syndrome and acute myocardial infarction. Forty-three patients received percutaneous coronary intervention with the GuardWire Plus system. Thirteen had unstable angina, five had non-Q myocardial infarction and 25 had ST segment elevation myocardial infarction. Forty-one target lesions were in native coronary vessels and two were in saphenous vein grafts. Total occlusion occurred in 18 patients. The mean occlusion time by the distal protective balloon was 262.8 +/- 114.1 s. Preoperatively, TIMI 0 flow was present in 18, TIMI II flow in two and TIMI III flow in 23 patients. Post-operatively, TIMI II and TIMI III flow were established in two and 41 patients, respectively. All procedures were successful and the GuardWire Plus system was successfully deployed in all but two patients. There was no procedure-related major adverse clinical event. There was no major adverse clinical event at 30 days. There was no device-related complication. We believe that the GuardWire Plus system is safe and feasible in patients with acute coronary syndrome and acute myocardial infarction.

Angina, Unstable↗
PubMed2003

Renal parenchymal malacoplakia: a rare cause of ARF with a review of recent literature.

Renal parenchymal malacoplakia is a rare cause of acute renal failure. Traditionally, it was associated with a high mortality rate and commonly resulted in renal failure requiring renal replacement therapy. The authors report on a 70-year-old woman who presented with acute renal failure caused by renal parenchymal malacoplakia. Her renal function recovered after levofloxacin treatment. All cases reported in the English-language literature since 1990, when fluoroquinolone was first used to treat malacoplakia, were reviewed. Although some patients still had renal failure, with renal biopsy and fluoroquinolone treatment, the patient mortality rate from renal parenchymal malacoplakia is remarkably low.

Acute Kidney Injury↗
PubMed2003

Burkholderia urinary tract infection after renal transplantation.

Urinary tract infection is a common complication after renal transplantation. The etiologies are diverse and the bacterial agents may sometimes be acquired during the hospital stay. We report a patient who developed Burkholderia cepacia urinary tract infection after renal transplantation. The bacteria showed in vivo resistance to all of the available antibiotics. A graft nephrectomy was eventually required to clear the infection. The consequence of some fastidious infection may be catastrophic and early recognition and treatment is necessary to optimize the treatment.

Burkholderia Infections↗
PubMed2003

Communication skill of general practitioners: any room for improvement? How much can it be improved?

OBJECTIVE: To measure any changes in the communication skills of primary care physicians before and after a part-time Diploma course in Family Medicine. SUBJECTS: 79 Hong Kong Chinese doctors (46 of whom were local graduates, with an average of 7 years in general practice). METHODS: Over the 10-month course in 2000-01, participants had 11 2.5-hour lecture/demonstrations in communication skills, 2 sessions of role play practice in groups of 20, self-analysis of a videotaped interview and skills evaluation. A before-after design measured scores in videotaped simulated patient interviews (rated by a research assistant using a structured observation guide, after standardisation by a psychologist) and scores in Objective Structured Clinical Examinations (OSCE) (rated by experienced family physician examiners with standardised checklists). RESULTS: There were wide variations in baseline skills, with scores ranging between 24-78 (out of 100) for video and 18-68 for OSCE, which were related to prior training and inversely associated with years after graduation. Significant improvements occurred in both video (from 53 to 61) and OSCE (from 46 to 56) post-course (P < 0.001). The group in the lowest quartile improved from 36 to 54 for video and from 29 to 48 for OSCE, while those in the second lowest quartile improved from 50 to 61 for video and from 44 to 56 for OSCE (F = 12.2, P < 0.001). Doctors who graduated more than 20 years ago made as much improvement as more recent graduates. CONCLUSIONS: Communication skills can be effectively taught to, and improved among experienced Chinese doctors by a combination of large-class teaching and medium-sized group practice with feedback, and without intensive individual supervision.

Clinical Competence↗
PubMed2003

Consensus statement on iodine deficiency disorders in Hong Kong.

This article reviews the available data on the study of iodine deficiency disorders in Hong Kong and to discuss the approach towards preventing such disorders in Hong Kong. The importance of iodine and iodine deficiency disorders is described, and the available data on the dietary iodine intake and urinary iodine concentration in different populations of Hong Kong are summarised and discussed. Dietary iodine insufficiency among pregnant women in Hong Kong is associated with maternal goitrogenesis and hypothyroxinaemia as well as neonatal hypothyroidism. Borderline iodine deficiency exists in the expectant mothers in Hong Kong. Women of reproductive age, and pregnant and lactating women should be made aware and educated to have an adequate iodine intake, such as iodised salt, as an interim measure. A steering group involving all stakeholders should be formed to advise on the strategy of ensuring adequate iodine intake, including universal iodisation of salt in Hong Kong. Continuous surveillance of iodine status in the Hong Kong population is necessary.

Deficiency Diseases↗
PubMed2002

Endotoxemia associated with intussusception and its diagnostic and surgical interventions.

To determine if and when intussusception results in endotoxemia and to evaluate whether diagnostic and surgical interventions of intussusception aggravate endotoxemia, intussusception was created in seven pigs during general anesthesia (ileocolic n = 3, ileo-ileocolic n = 2, ileocolic with silicone ring as leadpoint n = 1, ileoileal with silicone ring n = 1). After a period of observation and before progression to bowel gangrene, a diagnostic ultrasound study with a saline enema was undertaken, followed by a laparotomy and resection of the intussusception with a primary bowel anastomosis. Serial blood samples were obtained before and at regular intervals after: (1) formation of the intussusception; (2) the enema; and (3) resection for endotoxin measurement by limulus amebocyte lysate assay. The mean level of endotoxin increased from a pre-intussusception value of 0.750 EU/ml (range: 0.215-1.281) to a post-intussusception maximum of 1.482 EU/ml (0.997-2.882, P = 0.009), peaking mostly at 2 h after the intussusception. The mean pre-saline-enema level was 1.547 EU/ml (0.869-2.677) while the post-enema level was 1.41 EU/ml (0.84-2.468, P = 0.655). The mean pre-resection level was 1.470 EU/ml (0.784-2.468) while the post-resection maximum was (2.130 EU/ml) (0.850-4.381, P = 0.09). It is concluded that: (1) even in the absence of bowel gangrene intussusception results in significant endotoxemia within 2 h of its formation; (2) gentle saline enemas are not associated with endotoxemia; and (3) surgical resection results in a further upward surge of endotoxemia. These findings provide a scientific basis for improved understanding and management of intussusception.

Animals↗
PubMed2002

Localized single-photon wave functions in free space.

We solve the joint open problems of photon localization and single-photon wave functions in the context of spontaneous emission from an excited atom in free space. Our wave functions are well-defined members of a discrete orthonormal function set. Both the degree and shape of the localization are controlled by entanglement mapping onto the atom wave function, even though the atom is remote from the photon.

Journal Article↗