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Biomedical subjects

C K Yeung

Publications and source records attributed to C K Yeung.

At least 19 recordsLinked to original sources
PubMed1999

Potential utility of MRI in the evaluation of children at risk of renal scarring.

BACKGROUND: Gadolinium-enhanced MRI has recently been employed in the diagnosis of acute pyelonephritis. Its potential utility in the diagnosis of renal scars in children is unknown. Objective. To evaluate the potential utility of MRI using fat-saturated T1-weighted (T1-W) and post-gadolinium, short-tau inversion-recovery (STIR) sequences in detecting renal scarring by comparison with technetium dimercaptosuccinic acid ((99 m)Tc-DMSA) renal scintigraphy in children at risk of renal scarring. MATERIALS AND METHODS: A group of 24 children with spina bifida and neurogenic bladder or anorectal anomaly was studied. No patient had a history of acute pyelonephritis. Documented urinary tract infection (UTI) was present in 10 children (42 %). The remaining 14 (58 %) children had a history of asymptomatic bacteriuria. None had clinical signs or symptoms of acute UTI at the time of the study. (99 m)Tc-DMSA and MRI were performed to detect renal scarring. (99 m)Tc-DMSA scans were supplemented with pinhole imaging. MRI of the kidneys employed a fat-saturated T1-W sequence and a post-gadolinium STIR sequence employing a short echo time. RESULTS: Of the kidneys studied, 33 % (n = 16) had evidence of a renal parenchymal defect suggestive of scarring on (99 m)Tc-DMSA. The concordance in the detection of a scarred kidney by post-gadolinium STIR sequence and (99 m)Tc-DMSA is 94 %; that by fat-saturated T1-W sequence and (99 m)Tc-DMSA is 82 %; that by both sequences (positive result on either sequence) and (99 m)Tc-DMSA is 100 %. Using (99 m)Tc-DMSA as the gold standard, MRI had a sensitivity of 100 % and a specificity of 78 % in the diagnosis of a scarred kidney. The concordance in the detection of a scarred zone by post-gadolinium STIR sequence and (99 m)Tc-DMSA is 68 %; that by fat-saturated T1-W sequence and DMSA is 44 %; that by both sequences (positive result on either sequence) and (99 m)Tc-DMSA is 84 %. MRI had a sensitivity of 84 % and a specificity of 86 % in the diagnosis of a scarred zone, using (99 m)Tc-DMSA as the gold standard. CONCLUSION: The detection rate for renal scarring on MRI using the fat-saturated T1-W and post-gadolinium STIR sequences is comparable to planar (99 m)Tc-DMSA. MRI is of potential utility in the evaluation of children at risk of renal scarring.

Anal Canal↗
PubMed1999

Testicular catch-up growth after varicocele correction in adolescents.

We evaluated retrospectively the outcome of artery-sparing (AS) versus non-artery-sparing (NAS) laparoscopic varicocelectomy and measured any reversal of testicular growth. Twenty patients (13 left and 7 bilateral varicoceles) were evaluated after surgery. A total of 27 varicocelectomies (20 AS and 7 NAS) were performed. The indication for surgery was smaller testicular size on the affected side in all patients and discomfort/pain in 3. The mean age was 12.9 years (range 8-15 years) at surgery. The testicular volumes were determined clinically and by color Doppler sonography (US). The follow-up time was 6-48 months after surgery. There were 4 recurrences out of 27 varicocelectomies (15%), of which 1 has been reoperated. Testicular volumes were equal in both groups after surgery, indicating catch-up growth except in the cases with minor recurrences (2 AS and 2 NAS varicocelectomies). In 12 testes, dilated veins in the pampiniform plexus were revealed by US. No severe intraoperative complications occurred. Three patients had a hydrocele after surgery (11%). These data show that there is testicular catch-up growth after varicocelectomy, but some questions remain unanswered: (1) should the remaining dilated veins detected by Doppler US be tackled; and (2) is an AS operation worthwhile?

Adolescent↗
PubMed1999

A new management algorithm for impalpable undescended testis with gadolinium enhanced magnetic resonance angiography.

PURPOSE: We evaluated the diagnostic accuracy of preoperative localization of impalpable undescended testis using ultrasound and gadolinium (Gd) enhanced magnetic resonance angiography (MRA). MATERIALS AND METHODS: Ultrasound and Gd-MRA were performed prospectively in 21 boys (23 impalpable testes) with cryptorchidism before laparoscopy and surgical exploration. Gd-MRA was done using a 1.5 Tesla magnetic resonance scanner with a turbo field echo technique after bolus intravenous injection of 0.4 mmol./kg. body weight of Gd diethylenetriaminepentaacetic acid. A total of 10 dynamic scans were acquired during 15 minutes after Gd injection to cover the early arterial and delayed venous phases. All patients subsequently underwent diagnostic laparoscopy and definitive surgery. RESULTS: Ultrasound correctly localized 9 of 10 intracanalicular testes but failed to reveal any intra-abdominal or vanishing testes. In contrast, Gd-MRA correctly localized 4 intra-abdominal, all 10 intracanalicular and 8 canalicular vanishing testes. In 1 patient with an intra-abdominal vanishing testis ultrasound and Gd-MRA failed to make the diagnosis. When correlated with the findings of subsequent laparoscopy and surgical exploration, Gd-MRA had a diagnostic sensitivity of 96% and a specificity of 100% for localizing impalpable undescended testes. Based on Gd-MRA and ultrasound findings laparoscopy could have been avoided in 18 of 23 cases (78%). No adverse effect was associated with Gd use in this study. CONCLUSIONS: Gd-MRA accurately diagnoses vanishing testes and reliably differentiates intraabdominal from intracanalicular impalpable testes, allowing definite preoperative planning of the surgical approach and avoiding unnecessary laparoscopy. A new management algorithm for impalpable testis in patients with cryptorchidism is proposed based on ultrasound and Gd-MRA findings.

Algorithms↗
PubMed1999

Bladder dysfunction in children with refractory monosymptomatic primary nocturnal enuresis.

PURPOSE: We studied bladder dysfunction in children with significant primary nocturnal enuresis refractory to treatment. MATERIALS AND METHODS: We evaluated 33 Chinese boys and 8 girls with a mean age of 10.4 years, who had significant monosymptomatic primary nocturnal enuresis (3 or more wet nights weekly) after desmopressin treatment with or without an enuretic alarm failed. Daytime cystometry, continuous nighttime cystometry and electroencephalography monitoring during sleep, and detailed recording of daytime and nighttime urinary output were performed. RESULTS: We recognized 5 patterns of bladder dysfunction and its association with sleep-arousal status. Pattern 1 was normal daytime urodynamics with significant bladder instability at night with normal volume voiding precipitated by unstable detrusor contractions in 14 boys (34%). Pattern 2 was normal daytime urodynamics with frequent small volume voiding at night, probably representing latent bladder instability, in 4 boys (10%). Pattern 3 involved abnormal daytime urodynamics with small bladder capacity, a discoordinated daytime voiding pattern and marked nighttime bladder instability associated with poor sleep in 6 boys (15%). Pattern 4 was abnormal daytime urodynamics with an obstructive pattern, and marked daytime and nighttime detrusor hypercontractility (mean maximum detrusor pressure 178 cm. water) in 8 boys (20%). Pattern 5 was abnormal daytime urodynamics with a dysfunctional daytime voiding pattern and frequent small volume nighttime voiding in 8 girls and 1 boy (22%). In all patients functional bladder capacity was smaller than expected for age and the majority had no nocturnal polyuria. Despite underlying bladder dysfunction a 4-week course of 400 microg. desmopressin orally at bedtime still produced a significant response with a greater than 50% decrease in the number of wet nights during treatment in 47% of the patients, although enuretic symptoms immediately relapsed on cessation of therapy in all. Notably cystourethroscopy in 7 of the 8 boys with pattern 4 dysfunction revealed bladder trabeculations and abnormal urethral lesions, including congenital obstructive posterior urethral membranes in 4, Moormann's ring in 2 and irregular scarring at the bulbous urethra in 1. CONCLUSIONS: Abnormal bladder function, including small functional capacity, instability during sleep and marked detrusor hypercontractility, was common in our enuretic children in whom treatment failed. More importantly, nocturnal enuresis may be the only presenting symptom and there may be a response to desmopressin with a decreased number of wet nights even in cases of significant underlying bladder dysfunction. These findings may have important implications for our management strategy for monosymptomatic primary nocturnal enuresis.

Child↗
PubMed1999

Steroid-responsive pleuropericarditis and livedo reticularis in an unusual case of adult-onset primary hyperoxaluria.

We present a case of a 54-year-old woman with rapidly progressive renal failure of uncertain origin, who developed pleuropericarditis and livedo reticularis 6 weeks after initiation of hemodialysis (HD). The presentation with acute renal failure, the development of serositis, and the dramatic clinical response to empiric steroid therapy initially suggested the diagnosis of a systemic inflammatory disorder or vasculitis. Renal biopsy, performed 3 days after presentation, suggested crystal deposition disease, and subsequent investigations, using both dialysate oxalate concentrations and liver biopsy, led to the diagnosis of primary hyperoxaluria (PH). We discuss this atypical adult presentation of PH and propose a role for the use of steroids in the management of the acute inflammatory symptoms of oxalosis. We also briefly discuss the current medical management of patients with PH, including transplantation.

Age of Onset↗
PubMed1999

Laparoscopy as the investigation and treatment of choice for urinary incontinence caused by small 'invisible' dysplastic kidneys with infrasphincteric ureteric ectopia.

OBJECTIVE: To report our experience of using laparoscopy for the accurate location and simultaneous removal of small dysplastic kidneys with ectopic ureteric insertion causing urinary incontinence and that were not detected by conventional imaging modalities. PATIENTS AND METHODS: Seven girls (mean age 7.9 years, range 3.5-13) presented with urinary leakage occurring between normal voids. Imaging studies including ultrasonography, renal scintigraphy, intravenous urography, computed tomography and/or magnetic resonance imaging in six of the seven patients revealed a single normal functioning kidney, but failed to detect the contralateral nonfunctioning dysplastic kidney. All patients were examined under anaesthesia, followed by transperitoneal laparoscopy for the simultaneous localization and removal of the dysplastic kidneys under the same setting. RESULTS: Laparoscopy in all seven patients revealed a small dysplastic kidney that could always be easily located by first finding the draining ureter over the iliac vessels and then following it upwards. Four dysplastic kidneys were found in the renal fossa (two left, two right). One kidney was found at the left iliac fossa just above the pelvic brim, one at the left lumbar region, and the other at the right iliac fossa. Laparoscopic nephroureterectomy was successful in all seven girls and the patients were discharged 48 h after surgery. The follow-up (mean 2.7 years, range 3 months-5.4 years) showed excellent cosmetic results and all the patients have remained completely dry. CONCLUSIONS: In patients with a classical picture of urinary incontinence caused by infrasphincteric ureteric ectopia associated with a small nonfunctioning kidney, video-laparoscopy, with its magnifying effect, can reliably confirm the diagnosis, locate the dysplastic kidney and allow its removal in the same setting. We propose that laparoscopy should be considered the investigation and treatment of choice in such patients, and should be undertaken without delay even if the dysplastic kidney or the ectopic ureteric orifice cannot be identified with all other conventional means.

Adolescent↗
PubMed1999

Presence of donor- and recipient-derived DNA in cell-free urine samples of renal transplantation recipients: urinary DNA chimerism.

BACKGROUND: Previous studies have indicated that microchimerism is present in body tissues, peripheral blood, and plasma of recipients after organ transplantation. We hypothesize that donor-derived DNA may also be present in cell-free urine of renal transplant recipients and that the concentrations of urine DNA may be correlated with graft rejection. METHODS: Thirty-one female patients who had renal transplantation were enrolled in the study. In women with male organ donors, the SRY gene on the Y chromosome was used as a marker for donor-derived DNA. Real-time quantitative PCR for the SRY and beta-globin genes was carried out on cell-free urinary DNA from these patients. Serial urine samples from a female renal transplant recipient undergoing an acute rejection episode were also collected and analyzed with the beta-globin quantitative PCR system. RESULTS: SRY sequences were detected in the urine of 14 of 17 female patients with male organ donors. None of the 14 patients with female organ donors had detectable SRY sequences in urinary DNA. The median fractional concentration of donor-derived DNA was 8.7% (interquartile range, 1.9-26.4%). During the acute rejection episode, urinary concentrations of the beta-globin gene were markedly increased, with the concentrations returning rapidly to normal following antirejection treatment. CONCLUSIONS: Our results demonstrate that urinary DNA chimerism is present following renal transplantation. The measurement of urinary DNA using quantitative PCR may be useful for the diagnosis and monitoring of graft rejection.

Biomarkers↗
PubMed1998

Isoform specificity of trimethylamine N-oxygenation by human flavin-containing monooxygenase (FMO) and P450 enzymes: selective catalysis by FMO3.

In the present study, we expressed human flavin-containing monooxygenase 1 (FMO1), FMO3, FMO4t (truncated), and FMO5 in the baculovirus expression vector system at levels of 0.6 to 2.4 nmol FMO/mg of membrane protein. These four isoforms, as well as purified rabbit FMO2, and eleven heterologously expressed human P450 isoforms were examined for their capacity to metabolize trimethylamine (TMA) to its N-oxide (TMAO), using a new, specific HPLC method with radiochemical detection. Human FMO3 was by far the most active isoform, exhibiting a turnover number of 30 nmol TMAO/nmol FMO3/min at pH 7.4 and 0.5 mM TMA. None of the other monooxygenases formed TMAO at rates greater than 1 nmol/nmol FMO/min under these conditions. Human fetal liver, adult liver, kidney and intestine microsomes were screened for TMA oxidation, and only human adult liver microsomes provided substantial TMAO-formation (range 2.9 to 9.1 nmol TMAO/mg protein/min, N = 5). Kinetic studies of TMAO formation by recombinant human FMO3, employing three different analytical methods, resulted in a Km of 28 +/- 1 microM and a Vmax of 36.3 +/- 5.7 nmol TMAO/nmol FMO3/min. The Km determined in human liver microsomes ranged from 13.0 to 54.8 microM. Therefore, at physiological pH, human FMO3 is a very specific and efficient TMA N-oxygenase, and is likely responsible for the metabolic clearance of TMA in vivo in humans. In addition, this specificity provides a good in vitro probe for the determination of FMO3-mediated activity in human tissues, by analyzing TMAO formation at pH 7.4 with TMA concentrations not higher than 0.5 mM.

Chromatography, High Pressure Liquid↗
PubMed1998

Magnetic resonance cholangiography--feasibility and application in the paediatric population.

OBJECTIVE: To assess the feasibility of magnetic resonance cholangiography (MRC) in paediatrics. MATERIALS AND METHODS: MRC was attempted in 41 children from 1 week to 14-years. There were three groups: (1) children studied with MRI for non-biliary problems as controls; (2) infants with jaundice; and (3) older children suspected of biliary disease. The examination was successfully performed in 35 children, which included 12 children studied for non-biliary problems, 12 infants with jaundice, and 11 older children with suspected biliary disease. RESULTS: In group 1, the entire common duct was visualised in all 12 children. In group 2, successful demonstration of the common duct was achieved in two of the ten infants with subsequent confirmation of normal bile duct patency. In the last group of patients with suspected biliary disease, MRC gave good anatomical display of six choledochal cysts but failed to demonstrate the anomalous choledochopancreatic channel. It helped to confirm the diagnosis of two cases of pancreatic head cysts, and one case of Caroli's disease. CONCLUSION: MRC can be applied to the paediatric population, but its value depends on the type of problem to be evaluated. With current spatial resolution, its value in the diagnosis of biliary atresia is probably limited because it cannot reliably demonstrate the bile ducts in young infants with non-obstructive jaundice. In older children, it could provide a non-invasive anatomical display of the biliary tree and its disease. It has a potential role in addressing problematic cases encountered during ultrasonography.

Biliary Tract Diseases↗
PubMed1998

The role of ultrasound and oesophagography in the management of acute suppurative thyroiditis in children associated with congenital pyriform fossa sinus.

The thyroid is remarkably resistant to infection. Hence, when an infection does occur, the presence of a pyriform fossa sinus must be considered, particularly if it is recurrent and left sided. The aim of this paper is to alert radiologists to the existence, clinical presentation, and ultrasonographic and oesophagographic appearances of a pyriform fossa sinus. We present the role of ultrasound and oesophagography in five children with pyriform fossa sinus associated with suppurative thyroiditis. In four children the abnormality was on the left and on the right in one.

Abscess↗
PubMed1998

Community acquired fulminant Pseudomonas infection of the gastrointestinal tract in previously healthy infants.

Three previously healthy infants presented with diarrhoea and pyrexia and deteriorated rapidly. Two patients had necrotizing bowel disease requiring aggressive surgical intervention. All survived. P. aeruginosa gastrointestinal infection in previously healthy children is an extremely rare condition with a high mortality. Ecthyma gangrenosum was present in over 60% of reported cases although often not recognized initially. A high index of clinical suspicion, including prompt recognition of ecthyma gangrenosum, is mandatory for an early diagnosis of P. aeruginosa gastrointestinal infection. Early diagnosis and treatment may improve the prognosis.

Communicable Diseases↗
PubMed1998

Continuous real-time ambulatory urodynamic monitoring in infants and young children using infrared telemetry.

OBJECTIVE: To assess the feasibility of continuous real-time ambulatory bladder monitoring in infants and young children using a specially developed ambulatory urodynamic data logger with built-in infrared telemetric on-line facilities. PATIENTS AND METHODS: Twenty-nine infants and young children (mean age 3.9 years, range 7 weeks to 9.5 years) with various types of bladder dysfunction underwent urodynamic studies performed using an ambulatory urodynamic recorder with a specially developed integral transmitter that converts digital pressure signals to modulated infrared waves (935 nm). A receiver mounted on the ceiling of the room receives the signals emitted from the recorder. During the investigation, the infant can conduct normal activities, be totally mobile and be accompanied by the mother undisturbed in a private cubicle. The urodynamicist in the next room can observe all the patient's activities through a one-way mirror while continuous real-time on-line pressure signal displays are recorded and monitored using a computer, with event markers placed as necessary. For security, the data recorded during ambulatory investigation are stored in the internal memory of the ambulatory recorder. RESULTS: All 29 infants and young children completed the urodynamic studies using the new system; the results were satisfactory and reliable, with no data lost during ambulatory recording. The results obtained using infrared telemetry were not significantly different from conventional natural-filling urodynamic studies performed with a cabled on-line urodynamic recorder. CONCLUSION: The infrared telemetry system provides a reliable and effective way of performing continuous real-time ambulatory urodynamic monitoring in infants and young children. With the development of more powerful telemetric data transmission technologies, such a method could be extended in the near future to a truly ambulatory urodynamic recording with real-time on-line facilities, either at home or in the clinic, both for adults and for children.

Ambulatory Care↗
PubMed1998

The structure and autonomic innervation of the vesico-ureteric junction in cases of primary ureteric reflux.

OBJECTIVE: To determine the histological structure and autonomic innervation of the vesico-ureteric junction (VUJ) in cases of primary ureteric reflux, to compare the results with those reported previously for non-refluxing VUJs and thus determine possible structural anomalies which could be responsible for vesico-ureteric reflux (VUR). MATERIALS AND METHODS: Nineteen specimens of VUJs with reflux were obtained from four males and 10 females undergoing ureteric reimplantation. Serial frozen sections were cut and stained either with Masson's trichrome or immunostained for protein gene product (PGP 9.5), a general nerve marker, dopamine beta hydroxylase (D beta H), a marker for noradrenergic nerves, or neuropeptide Y (NPY). RESULTS: Longitudinally orientated muscle bundles of narrow diameter accompanied the ureter to its termination at the ureteric orifice. Where they merged with those of the superficial trigone. In some specimens, an additional muscle component was identified, situated on the outer aspect of the ureteric muscle coat, consisting of an incomplete layer of distinctive muscle whose constituent cells formed an interlacing mesh-work. Occasionally, specimens included detrusor muscle which consisted of relatively large diameter compact bundles separated from the ureter by a connective tissue sheath. D beta H- and NPY-immunoreactive (-IR) nerves were numerous among the ureteric muscle bundles. Many NPY-IR nerves occurred within the detrusor muscle while D beta H-IR nerves were mainly perivascular. When present, the outer muscle component was richly innervated by both D beta H- and NPY-IR nerves. PGP immunoreactivity varied among regions in the same section, PGP-IR nerves frequently being less numerous than those containing D beta H or NPY. CONCLUSION: These results indicate that the morphology of the VUJ in cases of VUR is indistinguishable from the normal VUJ described previously. Furthermore, the density and distribution of D beta H- and NPY-IR nerves is identical to that in controls. However, the antigenicity of PGP in the reflux specimens appears to be masked in some regions by an unknown factor.

Autonomic Nervous System↗
PubMed1998

Urodynamic patterns in infants with normal lower urinary tracts or primary vesico-ureteric reflux.

OBJECTIVE: To compare bladder function in infants with primary vesico-ureteric reflux (VUR) and those with normal lower urinary tracts. PATIENTS AND METHODS: The study comprised 42 patients (36 males) with VUR (grades III to V) and 21 (16 males) without VUR (mean age in both groups, 6 months). Intravesical catheters were placed suprapubically under general anaesthesia and, after at least 24 h, natural-tilling urodynamics were monitored for three or more filling and voiding cycles. RESULTS: Various urodynamics patterns were defined: for infants without VUR these were either normal or normal-immature (discoordinated micturition) and none showed features indicating abnormal bladder function. By comparison, 24 of 42 infants with VUR showed abnormal urodynamic patterns (57%, 95% confidence interval 41% to 72%, P < 0.001). Seven (17%) were defined as unstable with small voided volumes, five (12%) had inadequate voiding dynamics, 10 (24%) showed a markedly dyssynergic pattern and two (5%) had obstructive patterns. The unstable, inadequate and obstructive patterns occurred only in boys. Detrusor activity during the filling phase occurred in 14 infants (13 boys) with VUR and in only one without VUR, when it was trivial. Post-void residual volumes of > 30% capacity were seen only in the VUR group (in 24 patients). There were 18 infants with VUR that showed the normal or immature urodynamics patterns, but for the 14 males the voiding pressures were higher than for those without VUR (mean maximum detrusor pressure, 161 and 117 cmH2O, respectively: P < 0.02). CONCLUSIONS: There is an association between abnormal urodynamic variables and a diagnosis of primary VUR in young infants (notably males) that may have important implications for concepts about the genesis and persistence of VUR.

Female↗
PubMed1998

The vesico-ureteric junction in three cases of primary obstructive megaureter associated with ectopic ureteric insertion.

OBJECTIVE: To examine the histological structure and autonomic innervation of the vesico-ureteric junction (VUJ) in three cases of primary obstructive megaureter occurring in association with ectopic ureteric insertion. PATIENTS AND METHODS: Specimens of VUJ were obtained from one male and two females with primary obstructive megaureter and ectopic ureteric insertions. Serial frozen sections were cut and stained with either Masson's trichrome or immunostained for protein gene product (PGP 9.5; a general nerve marker) or dopamine beta-hydroxylase (DbetaH), a marker for noradrenergic nerves. RESULTS: In each case examined the terminal ureter was encircled by a thick collar of smooth muscle on the inside of which lay normal narrow-diameter longitudinally orientated ureteric muscle bundles. Loose connective tissue separated the surrounding detrusor muscle from this abnormal muscle collar, which was formed of distinctive smooth muscle cells arranged in a meshwork. The autonomic innervation of the ureteric and detrusor muscle bundles was similar to that previously reported for the normal VUJ while the thick muscle collar was richly innervated by DbetaH-immunoreactive noradrenergic nerves. CONCLUSION: The presence of an additional smooth muscle collar surrounding the terminal ureter may impede the normal flow of urine from ureter to bladder and be the cause of megaureter in these patients. We propose that the presence of this muscular collar arises from the developmental anomaly and suggest that these cases represent a subgroup that requires early surgical treatment.

Child↗