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Biomedical subjects

M Claudon

Publications and source records attributed to M Claudon.

At least 19 recordsLinked to original sources
PubMed2004

[Imaging of chronic and intermittent adult upper urinary tract obstruction].

State-of-the-art analysis of non invasive diagnostic imaging techniques to demonstrate upper urinary tract obstruction. Advances in imaging techniques are illustrated (sonography, CT scan, MRI). The imaging features of different presentations of chronic and intermittent obstruction are described with reference to current imaging modalities. New strategies for evaluation of chronic and intermittent upper urinary tract obstruction are proposed using ultrasonography as the first line examination. The role of MRI is illustrated. Causes of obstruction are classified based from the intraluminal, parietal or extrinsic location of the lesion.

Adult↗
PubMed2003

[Contrast-enhanced ultrasonography: renal applications].

Color Doppler US of the urinary tract is still facing a few limitations including, for B-mode imaging, the detection of small lesions, and, for color Doppler, the detection of low flow. Ultrasound contrast agents (USCA) improve these two limitations and allow the development of new functional applications for renal blood flow quantification. This improvement results from an increased acoustic response obtained from the microbubbles, as well as from the development of pulse sequencing and signal processing that led to the concept of specific ultrasound sequences. Most of the clinical indications of contrast-enhanced ultrasonography remain to be validated with the improved detection of the non linear response. USCA improve the detection of abnormal micro and macrovascular disorders of the kidney, particularly for the detection and the characterization of renal artery stenosis, as well as for the visualization of renal infarction. This technique showed potentials for the study of renal masses, especially atypical cystic lesions. Among the remaining indications, the detection of reflux and testicular torsion are the most promising.

Adult↗
PubMed2003

[Sonocystography: a new method for the diagnosis and follow-up of vesico-ureteric reflux in children].

Vesicoureteral reflux (VUR) is a common finding in children presenting with acute urinary infection, with a frequency ranging from 20 to 50%. If radiological retrograde cystography still remains the standard technique, sonocystography now appears as a valuable alternative method, due to the properties of recent ultrasound contrast agents and the wide use of harmonic imaging. The analysis of the literature and the experience acquired by the authors during a clinical trial allow summarizing the current data on this new technique. Because of its accuracy, it may replace radiological cystography in the detection of VUR in girls, the follow-up in both boys and kids, and the management of recurrent infection in children presenting with normal radiological cystography.

Child↗
PubMed2002

[Imaging of upper urinary tract tumors].

Urothelial tumors of the upper urinary tract are mainly represented by transitional cell carcinomas. They are usually multifocal, synchronous or metachronous. Patients most often present with hematuria. Histological staging is according to the degree of cellular anaplasia (grade) as well as to the degree of wall invasion (stage). Accurate and differential diagnosis are by excretory urography (EU) and/or by computed tomography (CT) associated with EU. EU and endoscopic investigations assess tumoral extension. The most appropriate treatment is radical nephroureterectomy with a cuff of bladder. Early and high recurrence is common; therefore a regular follow-up is required and depends on the initial treatment and the tumoral aggressiveness. This follow-up is performed by imaging, endoscopic and cytologic investigations.

Aftercare↗
PubMed2001

Dynamic MR imaging of bladder haemangioma.

Haemangioma is a rare benign mesenchymal tumour of the bladder. We report a case of bladder haemangioma and describe the enhancement kinetics observed on MR images after gadolinium bolus administration, which is similar to that reported in liver haemangioma.

Diagnosis, Differential↗
PubMed2001

Diffuse venous malformations of the upper limb: morphologic characterization by MRI and venography.

OBJECTIVES: To define the morphologic abnormalities in patients presenting with diffuse pure venous malformations (VM) of the upper extremity. SUBJECTS AND METHODS: A retrospective review of MRI and venography was performed on five patients, aged 6 months to 20 years, with extensive VM of the upper limbs. Abnormalities of major conducting veins were categorized as varicosities, stenoses, and asymmetrical pouches; anomalous venous spaces were classified into confluent lakes, interconnecting channels and spongelike plexiform networks. MRI and venographic data were reviewed separately and then simultaneously in order to establish correlation between types, location, and extent of lesions. RESULTS: In all patients, the percentage of replacement of normal tissues by VM was shown by MRI to be significantly higher in the distal limb than in the proximal limb. Involvement of multiple tissue layers was seen in all cases, including, with a decreasing rate, muscles, tendons, interosseous membrane of the forearm, and bone. Venography showed superficial varicosities, frequently associated with stenoses and assymetric pouches in all patients. Interconnecting channels and venous lakes were noted in half of the segments, typically in muscle and other deep locations, and subcutaneous spongelike lesions were seen in two patients. MRI provided a more accurate evaluation of tissue extent. Venograms better demonstrated morphological details and provided more information about the venous drainage. Direct comparison of MR images with venograms helped to identify and characterize venous lesions on cross-sectional MR data. CONCLUSION: Diffuse VM of the upper extremity are most extensive distally, and all tissues layers can be involved, each with a characteristic morphologic appearance. The morphology of different components of the VM is related to the nature of the surrounding tissue.

Adolescent↗
PubMed2001

Ultrasound contrast agents: properties, principles of action, tolerance, and artifacts.

The concept of contrast imaging was introduced to ultrasound almost 30 years ago. The development of ultrasound contrast agents (USCAs), initially slowed by technical limitations, has become more dynamic during the past decade. The ideal USCA should be non-toxic, injectable intravenously, capable of crossing the pulmonary capillary bed after a peripheral injection, and stable enough to achieve enhancement for the duration of the examination. While satisfying cost-benefit requirements, it should provide not only Doppler but also gray-scale enhancement. Already, Doppler examinations are improved by using USCAs when studying deep and small vessels, vessels with low or slow flow, or vessels with a non-optimal insonation angle. Ultrasound contrast agents also enhance detection of flow within abnormal vessels, including tumor vascularization and stenotic vessels, and provide better delineation of ischemic areas. Research is focusing on the development of specific contrast imaging sequences that allow detection of tissue enhancement similar to that obtained with CT or MRI. These sequences take advantage of the nonlinear behavior of the microbubbles within the ultrasound field, bringing real-time perfusion imaging for liver, kidney, and the myocardium into reach. New objectives include targeted agents that could further widen USCA applications to specific delivery of active drugs such as anticoagulants or cytotoxic compounds. The combination of new generations of USCAs and new ultrasound image sequences appears to be very promising and currently represents a significant part of ultrasound research.

Albumins↗
PubMed2001

Power Doppler US: evaluation of the morphology of stenoses with a flow phantom.

PURPOSE: To determine the importance of technical settings at power Doppler ultrasonography (US) for the evaluation of stenoses. MATERIALS AND METHODS: A computer-controlled phantom was used to induce a reproducible flow across a calibrated 71% stenosis in an 8.4-mm-diameter tube. Two transducers, 2-4 and 5-10 MHz, working at depths of 3.0 and 11.5 cm, respectively, with different beam angles (40 degrees, 60 degrees, and 90 degrees ), were used to simulate evaluation of pulsatile flow across normal and stenotic vessels in various conditions. For each condition, gain, pulse repetition frequency, and wall filter were progressively turned from low to high values. Two observers measured in a blinded fashion the apparent lumen of the stenotic and normal vessels on longitudinal and transverse images with the use of power Doppler US. RESULTS: When the high-frequency transducer was used, gain significantly affected both stenotic and feeding vessel measurement, whereas pulse repetition frequency and filter only affected feeding vessel evaluation. When the low-frequency transducer was used, all factors, including flow velocity and beam angle, played a significant role (P <.001). In most conditions, overestimation of the lumen and underestimation of the lumen of the feeding vessel led to severe underestimation of the degree of stenosis. CONCLUSION: Power Doppler US cannot be used to measure stenoses accurately. Underestimation of the degree of the stenosis was significantly higher with the low-frequency probe than with the high-frequency probe.

Blood Flow Velocity↗
PubMed2001

Comparison of alcohol-dependent patients with and without physiological dependence.

Sociodemographic and clinical characteristics of alcohol-dependent patients with or without physiological dependence (e.g. tolerance to alcohol or withdrawal) were compared. 186 consecutive alcohol-dependent patients hospitalized for alcohol detoxification were assessed. Diagnosis of alcohol dependence, tolerance and withdrawal was determined according to DSM-IV criteria. Assessment also included modalities of alcohol consumption and the Michigan Alcohol Screening Test (MAST). All patients presented alcohol dependence, 124 presented tolerance, 116 alcohol withdrawal and 146 (78.5%) tolerance and/or withdrawal. Patients with physiological dependence were older (51.4 vs. 46.9 years), drank more alcohol each day (20.3 vs. 11.3 drinks/day) and began alcohol consumption more often in the morning (67 vs. 37.5%). MAST scores were significantly higher in patients with physiological dependence (28.8 vs. 24.5), as was the mean corpuscular volume of erythrocytes (108 vs. 83 fl). No difference was found in terms of age, marital status, rate of unemployment, level of education and psychiatric comorbidity between the patients with and without physiological dependence.

Adult↗
PubMed2000

[Severe chronic renal failure subsequent to acute pyelonephritis in alcoholic patients].

BACKGROUND: Chronic alcoholism and malnutrition are uncommon causes of complicated acute pyelonephritis (APN). CASE REPORTS: Since 1997, we have seen 5 patients with chronic alcoholism (3 women and 2 men, mean age 53.4 +/- 13 years) without cirrhosis, diabetes or renal failure who developed severe APN in a state of malnutrition (albumin 22 +/- 3 g/l, total cholesterol 0.86 +/- 0.2 g/l). Diagnosis was made 14.6 +/- 9 days after onset of atypical symptoms which the patients neglected. There was a major bacterial inoculum: Escherichia coli 10(6.2 +/- 2) (3 multisusceptible and 2 amoxicillin-resistant strains); positive blood cultures in 3 cases. The imaging study showed bilateral diffuse lesions with focal swelling and kidney enlargement, without obstacle, abscess, or papillary necrosis. All patients had severe acute renal failure (maximum serum creatinine: 582 +/- 210 mumol/l; 3 patients underwent dialysis). Mean duration of antibiotic therapy was 40 +/- 7 days (i.v.: 22 +/- 3 d). Renal scarring occurred since creatinine clearance was 33 +/- 22 ml/min 2 months after the initial episode. One patient progressed to end-stage renal failure. CONCLUSION: In malnourished alcoholic patients, APN may be unusually severe due to late diagnosis leading to the risk of irreversible renal damage and severe chronic renal failure.

Acute Disease↗
PubMed2000

[Case report: the spontaneous course of a giant myelolipoma].

Adrenal myelolipomas are rare benign, non functioning tumors, mostly small and asymptomatic. We report the natural history of a giant adrenal myelolipoma. We could follow with CT the natural progression of the tumor during a 5-year interval.

Adrenal Gland Neoplasms↗
PubMed2000

Successful surgical thrombectomy of renal allograft vein thrombosis in the early postoperative period.

We report the successful surgical treatment of two cases of renal vein thrombosis, each occurring early after kidney transplantation. Prompt intervention was a result of accurate diagnosis by color Doppler ultrasonography. Invasive radiological procedures were not useful. Although recent advances in thrombolytic therapy have created several alternatives to open surgery, the rationale for surgical exploration in these cases was to remove the thrombus quickly, to avoid the postoperative bleeding complications of thrombolytic therapy, and to correct any technical or anatomic problems.

Adult↗