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Biomedical subjects

A J Dwyer

Publications and source records attributed to A J Dwyer.

At least 19 recordsLinked to original sources
PubMed2006

Complications after posterior dislocation of the hip.

Thirty-five consecutive patients with unilateral posterior dislocation of the hip were studied for complications at an average follow-up of 4.6 years (range 2-10 years). Thompson-Epstein type IV dislocation was most frequent (10/35), reflecting an increase in high-speed motor vehicles in the developing countries. It is also a severe injury that leads to a maximum number of complications, which include avascular necrosis, osteoarthosis, sciatic nerve injury and heterotrophic ossification. Avascular necrosis and osteoarthritis of the hip were observed maximally in type IV patients, even when reduction was achieved in less than twelve hours and may reflect the severity of initial injury. Heterotrophic ossification was observed in five of the ten patients with type IV dislocation and was associated with multiple attempts at reduction. Sciatic nerve injury did not recover completely in all cases, especially when reduction was delayed over twelve hours. Observing that the greatest numbers of complications were seen among patients with type IV dislocations, it may be prudent to warn such individuals about the likely prognosis at the outset, especially in today's world when the demands and expectations are high.

Adolescent↗
PubMed2005

Floating knee injuries: long-term results of four treatment methods.

One hundred twenty-four consecutive patients with true floating knee injury presented between 1987 and 2001. They were treated with non-operative, operative (external fixation and intramedullary nailing) and combined modalities. Sixty patients were followed up, at an average of 7.2 years, for age, gender, type of trauma and fracture; time to fracture union and time to mobilisation. Complications that were encountered and return to normal activities were recorded. Better and comparable union rates of fractures, earlier return to activities and higher excellent and good long-term functional results were observed among combined and operative (intramedullary nail) groups. Using combined modalities of treatment is an affordable, practicable and effective approach, especially for a resource-poor environment. External fixation of the fractured femur resulted in a decreased range of movement at the knee due to quadriceps muscle fixation. Fractured tibia, treated by any of the method, did not interfere with patient's joint mobilisation whereas associated injuries did.

Adolescent↗
PubMed2005

Nutritional status and wound healing in open fractures of the lower limb.

Forty-three patients averaging 28.2 (range 16--74) years with open fractures of the lower limbs were studied prospectively for 40 weeks using anthropometrical, biochemical and haematological parameters to ascertain their relationship to wound healing following injury. Nearly half (21/43) of the patients were malnourished at admission and the number increased to 22 a week after injury. Dietary advice and better food intake improved nutritional status with only 13 patients remaining malnourished at the 40th week. Wound healing was earlier when creatinine-height index was normal throughout the course of treatment and was delayed when serum albumin level was low.

Adolescent↗
PubMed2003

Femoral shaft fractures in children--a comparison of treatment.

Between April 1986 and March 1997, 83 femoral-shaft fractures in children 4-8 years old were treated at Christian Medical College and Hospital, Ludhiana, India. Among 35 patients with a minimum of 12 months follow-up, 14 were treated with Hamilton-Russell (HR) skin traction and 14 with proximal tibial skeletal traction. The group treated with HR traction had a shorter duration of (a) hospital stay (average 16.8 days versus 29.7 days for skeletal traction, p=0.02), (b) time to fracture consolidation (average 8.8 weeks versus 10.8 weeks for skeletal traction, p=0.04), and (c) return to normal activities (average 12.2 weeks versus 17.2 weeks for skeletal traction, p=0.03). At final follow-up (minimum 1 year), there were no significant differences in functional outcomes. Conservative management is still a gold standard for treatment of closed femoral shaft fractures in children 4-8 years of age. There appears to be no advantage to skeletal traction over skin traction in this age group.

Age Factors↗
PubMed2001

Lymphangioleiomyomatosis: CT of diurnal variation of lymphangioleiomyomas.

PURPOSE: To evaluate the imaging and clinical features of lymphangioleiomyomas and to describe the phenomenon of diurnal variation in the size of lymphangioleiomyomas in patients with lymphangioleiomyomatosis. MATERIALS AND METHODS: One hundred twenty-eight patients with lymphangioleiomyomatosis underwent chest and abdominopelvic computed tomography (CT). Thirteen patients underwent CT in the morning and afternoon of the same day to assess diurnal variation in lymphangioleiomyoma size. RESULTS: Twenty-seven of 128 patients (21%) had 54 lymphangioleiomyomas. The vast majority (96%) of these masses contained material of low attenuation at CT. Associated CT findings included enlarged abdominal lymph nodes, pleural effusions, ascites, and dilatation of the thoracic duct. The prevalence of lymphangioleiomyomas was 15% in patients who had mild pulmonary disease, 19% in patients who had moderate disease, and 26% in patients who had severe disease. Diurnal variation in size of masses was demonstrated in 12 of 13 patients. Seven of the 27 patients who had masses underwent biopsy; all seven were confirmed to have lymphangioleiomyomas. The most common symptoms associated with lymphangioleiomyomas were bloating, abdominal pain, and edema of the lower extremities. The majority of the patients reported worsening of symptoms as the day progressed. CONCLUSION: Lymphangioleiomyomas are common in patients with lymphangioleiomyomatosis. Diurnal variation in size may explain worsening of symptoms during the day.

Abdominal Neoplasms↗
PubMed2000

Utilization of oriented peptide libraries to identify substrate motifs selected by ATM.

The ataxia telangiectasia mutated (ATM) gene encodes a serine/threonine protein kinase that plays a critical role in genomic surveillance and development. Here, we use a peptide library approach to define the in vitro substrate specificity of ATM kinase activity. The peptide library analysis identified an optimal sequence with a central core motif of LSQE that is preferentially phosphorylated by ATM. The contributions of the amino acids surrounding serine in the LSQE motif were assessed by utilizing specific peptide libraries or individual peptide substrates. All amino acids comprising the LSQE sequence were critical for maximum peptide substrate suitability for ATM. The DNA-dependent protein kinase (DNA-PK), a Ser/Thr kinase related to ATM and important in DNA repair, was compared with ATM in terms of peptide substrate selectivity. DNA-PK was found to be unique in its preference of neighboring amino acids to the phosphorylated serine. Peptide library analyses defined a preferred amino acid motif for ATM that permits clear distinctions between ATM and DNA-PK kinase activity. Data base searches using the library-derived ATM sequence identified previously characterized substrates of ATM, as well as novel candidate substrate targets that may function downstream in ATM-directed signaling pathways.

Amino Acid Motifs↗
PubMed2000

Lymphangioleiomyomatosis: abdominopelvic CT and US findings.

PURPOSE: To describe the abdominal computed tomographic (CT) and ultrasonographic (US) findings in patients with thoracic lymphangioleiomyomatosis (LAM) and to relate the prevalence of the findings to the severity of pulmonary disease. MATERIALS AND METHODS: Eighty patients with LAM underwent chest and abdominopelvic CT and abdominopelvic US. The images were reviewed prospectively by one radiologist, and the abdominal findings were recorded and correlated with the severity of pulmonary disease at thin-section CT. RESULTS: Sixty-one (76%) of 80 patients had positive abdominal findings. The most common abdominal findings included renal angiomyolipoma (AML) in 43 patients (54%), enlarged abdominal lymph nodes in 31 (39%), and lymphangiomyoma in 13 (16%). Less common findings included ascites in eight (10%), dilatation of the thoracic duct in seven (9%), and hepatic AML in three (4%). A significant correlation (P =.02) was observed between enlarged abdominal lymph nodes and increased severity of lung disease. CONCLUSION: There are characteristic abdominal findings in patients with LAM that, in conjunction with the classic thin-section CT finding of pulmonary cysts, are useful in establishing this diagnosis.

Abdomen↗
PubMed1999

Autoimmune lymphoproliferative syndrome: a syndrome associated with inherited genetic defects that impair lymphocytic apoptosis--CT and US features.

PURPOSE: To describe the imaging findings in patients with autoimmune lymphoproliferative syndrome (ALPS) and to relate the findings to the clinical and genetic features of this recently recognized syndrome. MATERIALS AND METHODS: Retrospective or prospective reviews of the computed tomographic (CT) and ultrasonographic (US) studies and the clinical features in 19 consecutive patients with ALPS were performed. RESULTS: Most patients presented in the 1st year of life with symptoms of adenopathy and hepatosplenomegaly. At the time of presentation to the institution, 12 patients had already undergone splenectomy, and 14 patients had developed autoimmune disorders. All patients had multifocal adenopathy, which was massive in some patients; 14 of 15 patients who underwent CT of the chest had an enlarged thymus, and all six patients who retained their spleens and who underwent imaging had splenomegaly. Ten of 18 patients who underwent liver imaging had hepatomegaly. The adenopathy at US was hyper- and/or isoechoic relative to the liver and thyroid and was enhanced at CT in some patients. All patients had defective lymphocytic apoptosis, or programmed cell death, which was due to specific Fas (APT1 [TNFRSF6]) mutations in 15 patients. CONCLUSION: Patients with ALPS demonstrate nonspecific but often dramatic imaging findings of lymphoproliferative disorders, such as adenopathy, splenomegaly, thymic enlargement, and hepatomegaly. The stability of the clinical findings over months to years and the pattern of lymph node echogenicity may suggest the diagnosis of ALPS.

Adolescent↗
PubMed1998

Polypoid lesions of airways: early experience with computer-assisted detection by using virtual bronchoscopy and surface curvature.

PURPOSE: To test the application of a technique developed by the authors for the computer-assisted diagnosis of polypoid airway lesions from surface rendered virtual bronchoscopic reconstructions. MATERIALS AND METHODS: A computer algorithm was developed to detect polypoid airway lesions by means of segmentation of the bronchial surface with curvature classification. This method was tested with a bronchial phantom, five cadaveric lung specimens, and virtual bronchoscopic studies in 16 patients. RESULTS: For the patient studies, the sensitivity and specificity of the method were 47%-88% and 58%-89%, respectively, depending on the value of an adjustable parameter (the mean curvature threshold). The sensitivity increased (by 20% to 34%) when only lesions larger than 5 mm in diameter were considered. CONCLUSION: With this method, polypoid airway lesions can be detected automatically, although false-positive diagnoses present an important limitation.

Adult↗
PubMed1997

Advantages of polytetrafluoroethylene arteriovenous loops in the thigh for hemodialysis access.

BACKGROUND: The upper thigh is an alternative but infrequently used site to the forearm for placement of subcutaneous polytetrafluoroethylene (PTFE) arteriovenous conduits in patients requiring hemodialysis for end stage renal failure. This site has the great advantage of easier accessibility for self-cannulation. METHODS: The outcome was reviewed for 74 PTFE loops placed in 61 patients between 1985 and 1991. RESULTS: Mean loop survival time was 99.8 weeks (SD 78.0) when patients with early failure (<1 week), and those patients whose loops functioned adequately until transplantation or death were excluded. Infection occurred in 12 of 74 loops. CONCLUSIONS: Thigh PTFE loops provide satisfactory medium- to long-term vascular access for hemodialysis although, like all other forms of access currently available, they fall short of the ideal for prolonged dialysis.

Arteriovenous Anastomosis↗
PubMed1995

Decreased cerebral glucose metabolism in patients with brain tumors: an effect of corticosteroids.

The authors measured cerebral glucose metabolism (CMRglu) using [18F]fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in patients with brain tumors to evaluate the effect of exogenous corticosteroids (in this instance, dexamethasone) on glucose metabolism. Fifty-six FDG-PET studies obtained in 45 patients with unilateral supratentorial brain tumors were analyzed. Patients with brain tumors were divided into three groups: 1) patients with cushingoid symptoms, who had been treated with combinations of radiotherapy and chemotherapy taking oral dexamethasone; 2) patients not taking dexamethasone but treated with radiotherapy; and 3) patients not taking dexamethasone who had not been treated with radiotherapy. Serial FDG-PET scans were obtained in eight of the cushingoid patients. Glucose metabolism was measured in the contralateral cerebral and ipsilateral cerebellar hemispheres in patients and compared to measurements taken from 19 normal volunteers. The authors found that in the cushingoid brain tumor patients there was a marked reduction in CMRglu compared to normal volunteers and other brain tumor patients (Kruskal-Wallis test; p 0.001). In the majority of patients who had serial FDG-PET scans, there was a decline in glucose metabolism over time and in one patient, in whom dexamethasone was reduced in dosage, there was a subsequent increase in CMRglu. The authors conclude that there is a generalized reduction in CMRglu in brain tumor patients taking dexamethasone compared to other brain tumor patients and normal volunteers, and that this effect is independent of radiotherapy, concurrent anticonvulsant medication, and transhemispheric functional disconnection (transhemispheric diaschisis).

Adult↗
PubMed1993

Neuroimaging of juvenile pilocytic astrocytomas: an enigma.

PURPOSE: To present the imaging, metabolic, and clinical data obtained in five patients with juvenile pilocytic astrocytomas (JPAs) and discuss the paradoxical neuroimaging findings. MATERIALS AND METHODS: Five patients with JPAs who had undergone structural imaging and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were studied. Normalized glucose utilization rates (GURs) in the tumor were compared with GURs in histopathologically verified low-grade astrocytomas and high-grade tumors. RESULTS: All JPAs enhanced markedly after administration of contrast medium. Their glucose metabolism was significantly (P < .001) higher than that of low-grade astrocytomas and was similar to that of anaplastic astrocytomas. All patients with JPAs were in stable condition and showed no evidence of disease progression despite contrast enhancement and high tumoral glucose metabolism. CONCLUSION: The paradoxical FDG PET findings and enhancement at structural imaging might reflect the unusual vascularity of pilocytic tumors, and the increased GUR might be related to expression of the glucose transporter.

Adolescent↗
PubMed1992

Hydrated clearance of gadolinium-DTPA as a measurement of glomerular filtration rate.

Technetium (99mTc)-diethylene triamine pentaacetic acid (DTPA) hydrated clearance studies are accurate for determining GFR but require special facilities for handling and measuring samples. We investigated the potential of a non-radioactive paramagnetic analog, Gadolinium (Gd)-diethylene triamine pentaacetic acid (DTPA), an approved NMR contrast agent, as a glomerular filtration marker. Instead of relying on the radioactivity of technetium, this test is based on the fact that gadolinium induces alterations in the NMR T1 relaxation times in blood and urine samples. Ninety patients underwent simultaneous determinations of GFR using 1 mCi of Tc-DTPA and 0.05 mmol/kg Gd-DTPA (Berlex Labs) IV. The patients were hydrated with oral and intravenous fluid. Following a one hour equilibrium period, three or four consecutive urine collections were obtained; plasma samples were acquired at the beginning and end of each approximately 20-minute interval. 99mTc-DTPA radioactivity was determined with a scintillation counter. T1 relaxation times were measured on a 10 MHz NMR spectrometer. These were converted to Gd-DTPA concentration by comparison with standard solutions. The Gd-DTPA derived GFR closely approximated the 99mTc-DTPA derived GFR which ranged from 15 to 147 ml/min. The equation and correlation coefficient of the regression line is y = 1.04 x -2.2, r = 0.94. Thus, Gd-DTPA is a safe, non-radioactive indicator of GFR that may provide an alternative renal clearance method for clinical studies of progressive renal disease and nephrotoxicity.

Contrast Media↗
PubMed1992

Pulmonary metastases: MR imaging with surgical correlation--a prospective study.

The sensitivity of magnetic resonance (MR) imaging for detection of pulmonary metastases in 11 patients scheduled for thoracotomy and curative resection of metastases was evaluated with a prospective, controlled study. MR imaging performed at 0.5 T was compared with chest radiography, computed tomography (CT), and thoracotomy in 12 cases. (One patient had two separate occurrences of pulmonary metastases.) All images were interpreted in blinded fashion. When all MR sequences were interpreted together, MR imaging enabled correct identification of all patients with pulmonary nodules (100%). CT enabled detection of at least one nodule in all 12 cases (100%) by design; the sensitivity of chest radiography was only 64%. For individual nodules, MR imaging was at least as sensitive as CT (P2 less than .25 [two-sided value]) and significantly more sensitive than chest radiography (P2 less than .01). Among all MR sequences, short inversion time inversion-recovery sequences had the highest sensitivity for detection of individual nodules (82%).

Adult↗
PubMed1992

Distinction between hyperaldosteronism due to bilateral hyperplasia and unilateral aldosteronoma: reliability of CT.

Hyperaldosteronism due to a unilateral adenoma must be distinguished from hyperaldosteronism due to bilateral hyperplasia to enable the proper choice between surgical treatment (for adenoma) or medical treatment (for hyperplasia). To compare the efficacy of computed tomography (CT) and adrenal venous sampling, both examinations were performed in 24 patients with primary aldosteronism. All patients with a diagnosis of adenoma based on findings at venous sampling underwent adrenalectomy. The CT-based diagnosis was unilateral aldosteronoma in 17 patients and hyperplasia in seven patients. On the basis of venous sampling, unilateral adenoma was diagnosed in 22 patients; this diagnosis was confirmed by means of unilateral adrenalectomy in 21 patients. The most common error was diagnosis of hyperplasia based on the presence of bilateral nodules on CT scans: In six of seven patients with such a diagnosis, venous sampling and subsequent surgery revealed a unilateral adenoma. In hyperaldosteronism with multiple bilateral nodules, CT cannot reliably permit distinction between hyperplasia and adenoma.

Adenoma↗