Biomedical subjects
Publications and source records attributed to K L Chan.
The MRI and CT features of confluent hepatic fibrosis (CHF) are reported in two 6-year-old twins. This is the first case report in children of this little known entity, which may mimic mass lesions, and the first to describe an association of CHF with anti-tuberculous drugs.
PURPOSE: In view of the earlier reports that children below 1 year of age constitute a high-risk group for liver transplantation, the authors reviewed their experience in performing orthotopic liver transplantation in this age group. METHODS: The records of 9 children aged less than 1 year who underwent 6 living-related liver transplants and 3 reduced-size liver transplants between December 1993 and June 1997 were reviewed. RESULTS: Five reexplorations were required for 3 children who had 1 or more of the following early complications: bleeding from hepatic vein to inferior vena cava anastomosis (n = 1), right hepatic vein stump bleeding (n = 1), intraabdominal hematoma (n = 2), jejuno-jejunostomy leakage (n = 1), and colonic perforation (n = 1). Late complications include stricture at the biliary-enteric anastomosis requiring percutaneous balloon dilatation (n = 3) and hepatitis of undetermined etiology requiring retransplantation (n = 1). There was no hepatic artery thrombosis despite the small arteries available for anastomosis. Follow-up ranged from 19 to 61 months (mean, 40 months). Patient survival rate was 100%, and graft survival with good liver function was 89%. All living donors, 2 fathers and 4 mothers, are well. CONCLUSIONS: Liver transplantation in infants less than 1 year of age is technically demanding but feasible and still can be performed with a good outcome. Age alone (under 1 year) should not be considered as a contraindication for liver transplantation.
Early symptoms of nasopharyngeal carcinoma (NPC) can often be deceptive and confusing. Most patients with nasopharyngeal carcinoma present at an advanced stage with metastatic cervical nodes present at the time of diagnosis. A deep neck abscess as the presenting feature has not been reported. We report two cases of nasopharyngeal carcinoma which presented with retropharyngeal abscesses and persistent lymphadenopathy. These two patients illustrate that refractory lymphadenopathy, despite adequate treatment of the associated infection, should prompt a search for underlying disease. The relationship between nasopharyngeal carcinoma and retropharyngeal abscess is discussed.
We conducted a retrospective cohort study based on a case note review to determine whether there are differences in the treatment pathways followed for men and women admitted with acute myocardial ischemia and infarction after adjusting for differences in case mix. Women were as likely as men to receive thrombolysis, but were less likely subsequently to undergo exercise testing (adjusted odds ratio, 0.58; 95% CI, 0.40-0.84) or angiography (adjusted odds ratio, 0.62; 95% CI, 0.39-0.99). Coronary anatomy was the strongest predictor of revascularization regardless of sex. Women with diagnosed cardiac pain are less likely than men to be placed on the investigative pathways that lead to revascularization. Those women who are investigated are as likely as men to undergo revascularization. These findings are independent of the effects of age, angina grade, comorbidity, or cardiac risk factors. Clinicians' and patients' beliefs and preferences about treatment require investigation.
BACKGROUND: The role of nitric oxide in intestinal ischaemia-reperfusion (I/R) remains poorly defined, partly because of difficulty in detecting the nitric oxide free radical. In this study nitric oxide production was assessed during intestinal I/R by direct measurement using electron paramagnetic resonance (EPR), and the production of nitric oxide in jejunum and ileum was correlated with their different abilities to resist I/R injury. METHODS: Rats were given an electron spin trapper (diethyldithiocarbamate/ferrous citrate) by intraperitoneal injection. Thirty-six segments each of jejunum and ileum were subjected to 15-90 min of ischaemia and 25 min of reperfusion. Tissue samples were analysed for EPR signals using a spectrometer. RESULTS: Mean(s.d.) basal nitric oxide level was significantly higher in ileum (3.39(1.42) units) than jejunum (0. 65(0.05) units) (P = 0.0005). Increasing ischaemic times in the ileum resulted in decreasing nitric oxide levels (85, 32 and 13 per cent of basal level at 30, 60 and 90 min respectively); reperfusion resulted in further nitric oxide reduction (mean decrease 26 per cent). Severe (grade 3) histological damage was observed in low nitric oxide states (after 15 min of I/R in jejunum, 60 min of I/R in ileum). CONCLUSION: Nitric oxide can be measured in intestinal tissues directly by EPR. The findings support a protective role for nitric oxide in I/R, and offer an explanation for the greater resistance to I/R of ileum.
The recent recognition of a variety of pediatric renal tumors of different biologic behavior places an ever-increasing demand on the surgical pathologist for an accurate diagnosis. Although metanephric adenofibroma is one of the rarest benign renal tumors, the clinical importance of correctly diagnosing it cannot be overemphasized because it can potentially be mistaken as Wilms' tumor. We describe the clinical, radiologic, and pathologic features of a case of metanephric adenofibroma and discuss its differential diagnosis. The neoplasm was composed of two discrete components: a major fibroblastic element and a minor immature epithelial element. The latter formed a small nodule beneath the renal capsule, which could barely be detected by magnetic resonance imaging. This subcapsular nodule, however, was slightly soft and tan and was distinctly different from the white, whorled cut surface of the main tumor. It was formed by closely packed small immature epithelial cells in a slightly edematous background, which was histologically identical to metanephric adenoma and closely resembled epithelial Wilms' tumor. Unlike Wilms' tumor, however, the epithelial cells were very bland with no mitoses. The main bulk of the tumor was formed by spindle fibroblastic cells that were cytologically similar to the spindle cells in congenital mesoblastic nephroma. The tumor, however, was well demarcated without the irregular infiltrating edges of congenital mesoblastic nephroma. In contrast to the randomly distributed epithelial element throughout the stromal component in previous reported cases of metanephric adenofibroma, our finding of the exceedingly small and discrete epithelial component expands the known histologic spectrum of the disease. In addition, the presence of such minute epithelial nodule underscores the importance of diligent pathologic examination and careful sampling of tissue for histologic examination.
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OBJECTIVE: We report our experience using MR cholangiography and CT cholangiography in pediatric patients with choledochal cysts. SUBJECTS AND METHODS: Fourteen patients (two boys, 12 girls; mean age, 7.8 years) with either a preoperative diagnosis of choledochal cyst or a surgical finding of choledochal cyst underwent non-breath-hold MR cholangiography using T2-weighted fat-suppressed fast spin-echo sequences with a 1.5-T magnet, and CT cholangiography with IV infusion of meglumine iodoxamic acid. Radiologic findings were correlated with findings from surgery, operative cholangiography, or percutaneous transhepatic cholangiography. RESULTS: The biliary tree was visualized in all 14 patients with MR cholangiography and in 13 patients (92.9%) with CT cholangiography. In the 11 preoperative cases of choledochal cyst, MR cholangiography correctly showed all cysts and CT cholangiography showed 10 cysts (90.9%). The quality of images on CT cholangiography and MR cholangiography was comparable. The sensitivity of CT cholangiography and MR cholangiography in revealing intrahepatic stones was 83.3% and 66.7%, respectively; the specificity for both techniques was 100%. The rate of detecting the pancreatic duct and the common channel by CT cholangiography and MR cholangiography was 63.6% and 45.5% respectively. After surgery, CT cholangiography was superior to MR cholangiography in revealing the location of biliary-enteric anastomosis and the extent of anastomotic narrowing. CONCLUSION: Because non-breath-hold MR cholangiography is not invasive and does not use ionizing radiation and potentially toxic contrast agents, it is recommended as the imaging technique of choice in children with choledochal cysts. CT cholangiography can be considered as an adjunct after surgery and in patients in whom MR cholangiography is unsatisfactory.
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OBJECTIVE: To examine patient characteristics affecting the utility of transthoracic echocardiography in determining aortic valve morphology, particularly for the diagnosis of congenital bicuspid aortic valve (BAV). DESIGN: A retrospective comparison of preoperative echocardiographic determination of aortic valve morphology with pathological findings of the explanted valves. SETTING: A tertiary referral centre. PATIENTS: Consecutive patients who had aortic valve replacement between July 1994 and April 1996, and had preoperative echocardiograms. RESULTS: Of 313 patients, 181 (58%) had preoperative echocardiography. Three of the valves were excluded because they were too fragmented for pathological determination of valvular morphology. In the remaining 178 patients, aortic valvular morphology was determined by echocardiography in 104 (58%). Multivariate analysis showed that echocardiography was successful less often in women (odds ratio 0.44, P = 0.03) and in patients with densely calcified valves (odds ratio 0.69, P = 0.02), whereas age had no effect (odd ratio 0.99, P = 0.42). In those with adequate echocardiographic images, echocardiography had both a high sensitivity (0.92) and a high specificity (0.96) for the diagnosis of BAV. CONCLUSIONS: Echocardiography is a useful tool for the diagnosis of BAV, although suboptimal images may pose a problem in many patients, particularly women and patients with heavily calcified valves. When adequate images are obtained, transthoracic echocardiography can reliably identify aortic valvular morphology in most patients.
BACKGROUND: When to perform surgery for aortic regurgitation is a difficult clinical decision. Occult left ventricular (LV) dysfunction may be present in patients with minimal or no symptoms, and in some patients LV dysfunction may persist after valvular replacement. OBJECTIVES: To examine the role of preoperative low dose dobutamine echocardiography (LDDE) in predicting postoperative outcome in patients who had aortic valve replacement for aortic regurgitation. PATIENTS AND METHODS: The study group comprised 16 patients (15 men, aged 48 +/- 15 years) undergoing elective surgery for aortic regurgitation. Preoperative echocardiograms were obtained in the resting state and during dobutamine infusion at 7.5 micrograms/kg/min. Complete recovery was defined by normalization of LV size and function, and the absence of symptoms at the six-month follow-up visit. Patients with complete recovery (group 1) and without complete recovery (group 2) were compared in relation to their echocardiographic parameters at rest and during LDDE. RESULTS: Of 16 patients in the study, nine were in group 1 and seven were in group 2. Age, functional class and LV end-diastolic dimensions were similar between the two groups. Group 1 patients had a smaller preoperative LV end-systolic dimension index (22.4 +/- 3.3 versus 29.9 +/- 5.9 mm/m2, P < 0.05) and a higher preoperative ejection fraction (53 +/- 8% versus 37 +/- 13%, P < 0.01). Dobutamine infusion augmented the difference in ventricular size and function between patients in group 1 and those in group 2 (LV end-systolic dimension index 18.9 +/- 3.9 mm/m2 versus 28.8 +/- 7.1 mm/m2, P < 0.01; ejection fraction 61 +/- 7% versus 41 +/- 12%, P < 0.01). CONCLUSIONS: Dobutamine accentuates differences in ventricular size and function between those with and without subsequent complete recovery following valve surgery. Because preoperative ejection fraction during LDDE is highly predictive of postoperative ejection fraction, LDDE may have a role in predicting the clinical outcome of patients following aortic valve replacement for aortic regurgitation.
OBJECTIVE: To determine whether abnormalities in pulmonary venous flow (PVF) patterns detected by transesophageal echocardiography (TEE) correlate with the severity of mitral regurgitation (MR) or the presence of left ventricular (LV) abnormalities, and to demonstrate whether a normal PVF pattern predicts the absence of structural heart disease. DESIGN: Review of all TEEs performed at a tertiary care cardiac hospital over a four-month period. PATIENTS: Among 195 studies, 100 fulfilled the inclusion criteria. RESULTS: PVF was categorized into three patterns, which have been described previously. A normal PVF pattern predicted the absence of clinically significant MR with a high degree of certainty (positive predictive value [PPV] 98%). However, it did not predict the absence of structural cardiac disease (PPV 64%). A PVF pattern that showed systolic flow reversal was strongly predictive of the presence of significant MR (sensitivity 86%, specificity 100%, PPV 100%). The frequency of significant MR in this group was much higher than in patients with normal PVF (12 of 12 versus one of 66, P<0.0001). Patients with a blunted PVF pattern were more likely than patients with a normal PVF to have LV abnormalities (18 of 22 versus 23 of 66, P=0.0005). However, a blunted PVF was not associated with clinically significant MR. CONCLUSIONS: A normal PVF does not rule out the absence of LV abnormalities but confirms the absence of significant MR. Systolic flow reversal is highly predictive of the presence of significant MR. A blunted PVF is more likely to be associated with LV abnormalities than with MR and has limited usefulness in the diagnosis of significant MR.
OBJECTIVE: The purpose of this study was to obtain normal values of nasal geometry in Asian children with no nasal problems using the acoustic rhinometry method. METHOD: Acoustic rhinometric measurement of the nasal fossae was performed in pediatric patients coming for general surgical operations with no nasal problem. RESULTS: A cohort study of 183 children in an acute care hospital with full elective and emergency surgical services was undertaken. The mean minimal cross-sectional area (MCA), which was functionally important for nasal breathing, was found to be 0.32 cm2 (SD = 0.13) and situated at 1.40 cm (SD = 0.26) from the anterior nare. Normal values for area, length, and volume of the nose in these children as a group and at different ages from 1 to 11 years old were obtained. CONCLUSIONS: Acoustic rhinometry was found to be well tolerated by the children. The MCA was confirmed to be situated at the anterior part of the nose and had a positive correlation with an increase in age.
BACKGROUND: Recent observations suggest that a spontaneous echocardiographic contrast with fast motion (FEC) mimicking intravenous contrast can be seen in the left atrium in the absence of intravenous contrast injection. OBJECTIVE: To assess the incidence of FEC and to evaluate the differentiating features between FEC and injected saline contrast. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral centre. PATIENTS AND METHODS: Transesophageal echocardiography was performed in 91 consecutive patients with a mean age of 58+/-15 years. Patients with mechanical valves and congenital heart disease were excluded. Images of the right atrium, left atrium and pulmonary veins were obtained in the absence of an intravenous catheter during quiet respiration, cough and the Valsalva manoeuvre. The same procedure was repeated during injection with agitated saline after venous cannulation. RESULTS: In the absence of intravenous cannulation, FEC was detected in eight patients (9%) during quiet respiration, 36 patients (40%) during cough and 55 patients (60%) during the Valsalva manoeuvre. During the Valsalva manoeuvre, FEC was detected in the right atrium in 41 patients (45%) and in the left atrium in 33 patients (36%) (P=0.15). FEC was not related to a history of embolic event, left atrial smoke or patent foramen ovale. Intra- and interobserver agreements in the detection of FEC were 96% and 90%, respectively. CONCLUSIONS: FEC can be observed frequently in the left atrium during cough or the Valsalva manoeuvre, and awareness of FEC is important to avoid the erroneous diagnosis of patent foramen ovale.
Spontaneous regression of some tumours is known to occur. We report here on a patient who developed lung and scalp metastases from renal cell carcinoma approximately 1 year after undergoing a radical nephrectomy. The lung metastasis was documented by computed tomography and histological examination. A spontaneous complete regression of the lung and scalp metastases occurred. Shortly after, however, a brain metastasis developed in the absence of any radiographic evidence of recurrence in the primary site or the lung.
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BACKGROUND: The management of mild aortic stenosis during coronary artery bypass grafting remains controversial. METHODS: We reviewed the medical records of consecutive patients between January 1, 1977, and December 31, 1994, to identify 51 patients with mild aortic stenosis who underwent isolated coronary artery bypass grafting (group A), and 19 patients with mild aortic stenosis who underwent combined coronary artery bypass grafting and aortic valve replacement (group B). Patients with more than moderate aortic regurgitation were excluded. Preoperative angiograms were reviewed to assess the severity of calcification and restricted mobility of the aortic cusps. RESULTS: In group A there were 11 deaths and 8 subsequent aortic valve replacements; in group B there were 5 deaths and 3 prosthetic valve-related complications. There was no difference in event-free survival between the two groups after adjusting for the difference in age. Among group A patients, the initial transvalvular gradient (p = 0.0005) and aortic valvular calcification (p = 0.06) identified patients who demonstrated progression to severe aortic stenosis during follow-up. CONCLUSIONS: Our data suggest that routine aortic valve replacement during coronary artery bypass grafting in patients with mild aortic stenosis is not indicated, but concomitant aortic valve replacement may be appropriate in patients with higher transvalvular gradients and calcified valves.