Biomedical subjects

K van Leeuwen

Publications and source records attributed to K van Leeuwen.

At least 19 recordsLinked to original sources

PubMed2001

Environmental quality standards: endpoints or triggers for a tiered ecological effect assessment approach?

The recently derived Dutch Environmental Quality Standards (EQS) for water, soil, and sediment for approximately 170 substances have been evaluated. Three methods have been used to derive the Dutch EQS. Independent of how the EQS were derived, they are given equal weight in Dutch environmental policy. Scientifically, the three methods may deserve different weights. For example, for soil and sediment, the least reliable method had to be applied to derive most of the EQS. Ecological effects in these compartments may be either overestimated or underestimated. A multitiered approach is proposed, which is relevant for all parties involved, including other countries, and which may help improve ecological effect assessment.

Conservation of Natural Resources↗

PubMed2000

[Good medical care at the borderline of mental incompetence].

A 73-year-old woman with minor intellectual skills had complaints which suggested a vulvar carcinoma. Despite her refusal she was examined and admitted to hospital, on the basis of good professional care. The psychiatrist examined her and judged her incompetent. For the operation of the diagnosed vulvar carcinoma a court ordered representative was obtained. Two months later she underwent radiotherapy to prevent local complications and pain and a few weeks thereafter she died. Because medical decision-making in a doctor-patient relationship is not always possible decision-making power should be assigned to a third party. That forms the basis of proper medical care.

Aged↗

PubMed2000

Long-term follow-up of redo pull-through procedures for Hirschsprung's disease: efficacy of the endorectal pull-through.

BACKGROUND/PURPOSE: The purpose of this study was to review the authors' 25-year experience with redo pull-through procedures for Hirschsprung's disease including surgical technique and long-term outcome. METHODS: From 1974 to now, over 325 patients with Hirschsprung's disease have been treated at C.S. Mott Children's Hospital. This includes 30 patients referred after an unsuccessful pull-through at another hospital and 2 patients with an unsuccessful pull-through from C.S. Mott. All redo pull-throughs (n = 19) were performed in these patients, and their clinical courses are reviewed. RESULTS: Twelve patients required reoperation secondary to a mechanical problem with their first pull-through. The other 7 patients had evidence of residual segments of dilated colon leading to functional failure of their initial operation including 5 patients with documented aganglionic bowel present at the second pull-through. Ten of the patients requiring reoperation initially had an endorectal pull-through (ERPT), 5 had a Duhamel procedure, 3 had a Swenson procedure, and 1 had a Rehbein procedure. Choice of revision was an ERPT in 8 patients in whom an adequate rectal cuff could be developed. Additional redo procedures included a Duhamel in 8 patients and a Swenson in 3 patients. Follow-up ranges from 3 months to 23 years (mean, 13.8 years). There were no deaths in the series, and 1 patient required a third pull-through. All patients who are not neurologically impaired and are over age 3 are continent except one (94%). Stools per day range from 1 to 10 (mean, 3.2). CONCLUSIONS: Redo pull-through operations for Hirschsprung's disease appear to be as effective as primary procedures in terms of continence and stooling frequency. Distinct from other series, we found an ERPT to be the procedure of choice if an adequate rectal cuff was present.

Adolescent↗

PubMed2000

Congenital cystic adenomatoid malformation: impact of prenatal diagnosis and changing strategies in the treatment of the asymptomatic patient.

OBJECTIVE: This study was designed to assess the effect of prenatal sonographic diagnosis on the treatment of congenital cystic adenomatoid malformation of the lung. MATERIALS AND METHODS: The medical records of 27 patients with pathologically proven congenital cystic adenomatoid malformations were retrospectively reviewed. Patients were divided into four groups based on mode of presentation: with or without abnormal findings on prenatal sonography and with or without symptoms at birth. Age at diagnosis, age at surgical intervention, complications, and length of hospital stay were recorded for each group. RESULTS: Twenty-seven patients with 31 proven congenital cystic adenomatoid malformations were included. Eleven patients underwent prenatal sonography establishing the diagnosis (6 asymptomatic at birth, 5 symptomatic), and 16 did not have a prenatal diagnosis (10 asymptomatic at birth, 6 symptomatic). In the symptomatic populations, prenatal diagnosis had no impact on age at surgery, length of stay, or surgical complication rate (p = 0.78-0.83). In the asymptomatic population, prenatal diagnosis allowed early diagnosis (p < 0.001) and resection in the asymptomatic period. It was also associated with a shorter length of stay at the time of surgical resection (mean time, 4.2 days for patients with prenatal diagnosis versus 12.9 days for those without it;p < 0.001) and with a trend toward lower serious complication rate (3 patients without prenatal diagnosis versus 1 patient with it). CONCLUSION: Prenatal sonography provides the radiologist a means to identify congenital cystic adenomatoid malformations in a population of infants who are asymptomatic at birth. Surgical intervention in the asymptomatic infant is associated with a shorter length of stay, a trend toward fewer complications, and decreased medical cost compared with intervening after symptoms develop.

Case-Control Studies↗

PubMed1999

Prenatal diagnosis of congenital cystic adenomatoid malformation and its postnatal presentation, surgical indications, and natural history.

BACKGROUND/PURPOSE: Regression of a cystic adenomatoid malformation (CAM) in a fetus is well described. Little, however, is known about the postnatal course of these infants. This study attempts to correlate the prenatal course of CAMs with postnatal symptoms, radiological manifestations, and need for surgery. METHODS: The clinical course of patients with a CAM diagnosed prenatally were retrospectively reviewed. Inclusion in the study required a prenatal ultrasound scan documenting a CAM. RESULTS: Over 10 years, 14 patients with a CAM were diagnosed prenatally. Six (43%) showed a partial in utero regression. Four patients were symptomatic at birth and underwent a resection as newborns. Ten patients were asymptomatic at birth, and eight of these had normal chest x-rays. Elective resection has been performed in 3 of these 10, and two additional children are scheduled to undergo an excision near 1 year of age. The remaining five patients have undergone follow-up nonoperatively for a mean of 36 +/- 15 months. Of the seven asymptomatic patients not undergoing immediate surgery, only one has shown a slight postnatal regression, despite five of these showing regression in utero. None have become symptomatic. CONCLUSIONS: The results suggest that regression of a CAM on prenatal ultrasound scan is common, but this process does not continue after birth. A normal chest x-ray does not indicate complete regression of a CAM; a computed tomography (CT) scan is required to evaluate such patients, and will generally demonstrate a CAM. Asymptomatic patients with a CAM may be followed up nonoperatively with no apparent adverse effects. The decision and timing of an excision in an asymptomatic patient remains controversial among pediatric surgeons.

Cystic Adenomatoid Malformation of Lung, Congenita↗

PubMed1997

A multivariable risk factor analysis of the portoenterostomy (Kasai) procedure for biliary atresia: twenty-five years of experience from two centers.

OBJECTIVE: The authors investigated risk factors for failure after portoenterostomy for biliary atresia using univariate and multivariable methods. SUMMARY BACKGROUND DATA: Kasai's portoenterostomy has gained worldwide acceptance as the initial surgical therapy for infants with biliary atresia. Although extended survival has been achieved for many patients, factors influencing outcome have not been defined clearly. METHODS: The authors analyzed risks for failure in 266 patients treated from 1972 to 1996 by the Kaplan-Meier product limit estimate and Cox proportional hazards model. Failure was defined as death or transplant. RESULTS: Age at surgery, surgical decade, and anatomy of atretic bile ducts were identified as independent risk factors. Five-year survival was 49% and median survival was 15 years when bile drainage was achieved. Sixty-five patients had liver transplants. Mean age at transplant was 5.4 years. CONCLUSIONS: The outcome after portoenterostomy for biliary atresia is determined by age at surgery and anatomy of the atretic extrahepatic bile ducts. Liver transplant will salvage patients with failed Kasai with 10-year posttransplant survival of 71%.

Adolescent↗

PubMed1991

Concept of maximal flow ratio for immediate evaluation of percutaneous transluminal coronary angioplasty result by videodensitometry.

BACKGROUND: In the setting of percutaneous transluminal coronary angioplasty (PTCA), immediate information about the result of the intervention is important, whereas morphological parameters are often less reliable than in diagnostic coronary arteriography. Recently, a new videodensitometric method was introduced and validated in animal experiments, which allows accurate comparison of maximal myocardial perfusion between situations with different degrees of stenosis. This method uses mean transit time (Tmn) of the contrast agent at maximal hyperemia as a parameter for maximal flow and is strictly in accordance with indicated dilation theory. METHODS AND RESULTS: In 40 patients with angina pectoris, single-vessel disease, and a positive exercise test at the time of acceptance for PTCA, this approach was applied for evaluation of the improvement of maximal flow achieved by the PTCA. Maximal vasodilation was induced immediately before and 15 minutes after PTCA by intracoronary administration of papaverine, and digital angiographic studies were performed. By special breath-holding instruction, almost motionless, triggered image acquisition was possible during 15-20 heartbeats. Excellent subtraction images could be obtained, and reliable determination of Tmn at maximal hyperemia was possible in 33 patients both before and after PTCA. The ratio between maximal flow after and before PTCA, called maximal flow ratio (MFR), was represented by the ratio between Tmn before and after the intervention and compared with the results of exercise testing 24-48 hours before and 7-10 days after the procedure. After correction for pressure changes, MFR was 2.2 +/- 1.5 for the 33 dilated vessels and 1.0 +/- 0.2 for 25 normal vessels serving as a control. In 94% of all patients, an MFR value of more than 1.6 or less than 1.6 discriminated between presence or absence of reversal of exercise test result from positive to negative. If on-line judgment of success was based upon angiographic parameters or measurement of trans-stenotic pressure gradient, the relation with noninvasive functional improvement was present only in 66% and 74% of all patients, respectively. A definite range of what can be called normal Tmn at maximal hyperemia could be distinguished, and post-PTCA values for successfully dilated arteries returned completely to this normal range. CONCLUSIONS: Accurate comparison of maximal myocardial perfusion before and after PTCA is possible in man, improvement of maximal flow is highly related to functional improvement as indicated by exercise test results, and, therefore, this method provides a straightforward way for on-line evaluation of the result of the intervention.

Absorptiometry, Photon↗

PubMed1990

[Extracardial manifestations in constrictive pericarditis].

Constrictive pericarditis is a slowly progressive disabling disease. The diagnosis is easily overlooked because of the striking extracardial signs and symptoms such as abdominal discomfort, general fatigue, cachexia, ascites and oedema. We describe 7 patients with these symptoms in whom the diagnosis was missed during 0.5-17 years. The decisive clue for correct diagnosis appeared to be the raised central venous pressure. This proves the importance of an accurate physical examination. Other findings were: ascites (7/7), hepatomegaly (7/7), oedema (6/7), narrow pulse pressure (less than or equal to 35 mmHg) (5/7), ECG abnormalities (7/7) and pericardial calcifications on the chest X-ray (5/7). In addition we found slightly raised liver enzymes and a protein-losing enteropathy leading to low serum protein levels. These abnormalities are all explained by the alterations in haemodynamics and lymph flow. The only curative therapy is surgical decortication of the heart.

Adult↗

PubMed1989

Kissing balloon angioplasty of a circumflex artery bifurcation lesion. A new approach utilizing two balloon-on-wire probes and a single guiding catheter.

A new approach to angioplasty of a coronary artery bifurcation lesion is described. Via a single guiding catheter, two ultra low-profile balloon-on-wire probes were advanced into the AV sulcus branch and a large obtuse marginal branch of the circumflex artery. The balloons were inflated simultaneously. The technique was easy to perform and remarkably effective.

Angioplasty, Balloon↗

PubMed1988

Determination of cardiac output by single gated pulsed Doppler echocardiography.

The aim of the study was to evaluate the use of single gated pulsed Doppler cross-sectional echocardiography for measurement of the cardiac output. Pulsed Doppler echocardiography was used to assess both area and blood velocity at the aortic orifice. Stroke volume estimates were determined by multiplying area by systolic time velocity integral as measured from the parasternal and apical approach, respectively. We investigated a group of 17 healthy individuals and a group of 20 patients with coronary artery disease. In the first group no change was found in aortic area during systole (P less than 0.01). During a follow-up of two weeks no change in aortic area was observed either (P less than 0.01). Intraobserver, interobserver and day-to-day variability of the aortic area, expressed as the coefficient of variation was 3.6 +- 5.2%, 4.6 +- 5.7% and 7.8 +- 3.8% (mean +- 1 SD), respectively. The interobserver variability of the time velocity integrals was 6.0 +- 6.2%. In the second group the cardiac output as measured with the thermodilution method ranged from 3.8 to 8.0 l/min. Comparison of the Doppler and thermodilution technique for measurement of cardiac output showed a correlation coefficient of r = 0.76 (P less than 0.001) and the following regression equation: CO (Doppler) = 1.0 x CO (thermodilution)-700 ml. The Doppler method underestimated cardiac output relative to the thermodilution method.

Adolescent↗

PubMed1987