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Biomedical subjects

J F Platt

Publications and source records attributed to J F Platt.

At least 37 records · Page 2Linked to original sources
PubMed1996

Suspected obstructive pyelocaliectasis: Doppler ultrasonography compared with diuretic renal scintigraphy in proven cases.

OBJECTIVE: To compare Doppler ultrasonography with diuretic renal scintigraphy in the differentiation of obstructive from nonobstructive pyelocaliectasis. PATIENTS AND METHOD: The authors reviewed the findings of Doppler ultrasonography and diuretic renal scintigraphy performed over a 3-year period for 27 pyelocaliectatic kidneys (17 obstructed and 10 unobstructed) in 20 individuals ranging in age from 19 to 88 years. The kidneys were classified as "obstructed" or "unobstructed" on the basis of the resistive index as calculated from Doppler ultrasonographic results and as "obstructed", "unobstructed" or "indeterminate" on the basis of the clearance half-time determined from scintigraphic findings. RESULTS: On the basis of scintigraphy, the obstruction status was indeterminate in 12 of the 27 kidneys. The data were analysed for sensitivity and specificity in two ways, first by classifying the kidneys with indeterminate obstruction status as "obstructed, " and then by excluding them from the analysis altogether. In both situations, the differences in sensitivity and specificity between Doppler ultrasonography and scintigraphy were not statistically significant (chi 2 test, p > 0.05). When the kidneys with indeterminate obstruction status were included in the obstructed category, the sensitivity and specificity of Doppler ultrasonography were 94% and 90% respectively and of scintigraphy 100% and 70% respectively; when the kidneys with indeterminate obstruction status were excluded, the sensitivity and specificity of Doppler ultrasonography were 83% and 89% respectively and of scintigraphy 100% and 78% respectively. CONCLUSIONS: These results suggest that Doppler ultrasonography is comparable to diuretic renal scintigraphy in the work-up of potential obstructive pyelocaliectasis. Because grey-scale ultrasonography is usually performed before scintigraphy, a Doppler examination could be added at this stage, which might reduce the time necessary to establish the diagnosis.

Adult↗
PubMed1996

Molecular strategies for clinical xenotransplantation in cardiothoracic surgery.

The current shortage of donors for allotransplantation has generated interest in the potential use of animal organs to meet increasing clinical transplant needs, ie, xenotransplantation. However, when phylogenetically distant species such as the pig are transplanted into unmodified primate hosts--discordant xenotransplantation--the grafts undergo a rapid rejection process characterized by edema, hemorrhage, and diffuse microvascular thrombosis. "Hyperacute rejection" as such is mediated by an IgM natural antibody directed against the galactose alpha(1,3) galactose epitope expressed on the endothelial cell surface of all mammals except old world monkeys, apes, and humans which collectively lack the galactosyltransferase enzyme necessary for antigen expression. Transplants between nonhuman primates and human recipients--concordant xenotransplantation--avoid hyperacute rejection, but nonetheless undergo "acute vascular rejection" and progressive microthrombotic injury. Acute vascular rejection is associated with endothelial cell "activation," loss of vascular integrity, and progressive thrombosis. Molecular strategies for avoiding xenograft rejection involve insertion of genes into the donor pig genome capable of modifying xenoreactive antigen expression and regulating antibody-mediated endothelial cell damage.

Animals↗
PubMed1996

Urinary obstruction.

Radiologic imaging is commonly used in the diagnosis, classification, and follow-up of renal obstruction. Precise definitions of the elements of urinary obstruction are critical. This article examines the physiology of renal obstruction and the use of such imaging tests as excretory urogram, retrograde pyelography, antegrade pyelography, Whitaker test, ultrasound, CT scan, MR imaging, and radionuclide renography.

Acute Disease↗
PubMed1995

Small echogenic renal masses: how often is computed tomography used to confirm the sonographic suspicion of angiomyolipoma?

OBJECTIVES: Although renal angiomyolipoma (AML) has a typical ultrasound appearance, many authorities suggest that a computed tomography (CT) scan be obtained to confirm the diagnosis because small echogenic renal cell carcinomas can simulate AML. Our study evaluates the actual follow-up in such patients and factors that may affect whether CT confirmation is recommended or obtained. METHODS: From 1986 through 1992, 36 patients had an ultrasound diagnosis of probable renal AML (well-circumscribed, homogenously echogenic mass). In each case the patient's age, symptoms, ultrasound results and recommendations, and imaging follow-up were recorded. RESULTS: CT confirmation of the sonographic diagnosis was recommended in only 11 of 36 (31%) patients. Only 7 of these 11 patients actually underwent CT, 5 of whom had the diagnosis confirmed by CT detection of intratumoral fat. Ten of 23 patients (43%) over 50 years of age had CT recommended, whereas only 1 of 13 (8%) patients under age 50 years did (P < 0.05). CT confirmation was recommended for 5 of 13 (38%) lesions greater than 10 mm and for 6 of 23 (26%) smaller masses. None of the 9 patients under age 50 years with small masses (less than 10 mm) had CT recommended. CONCLUSIONS: Although many authorities recommend CT to confirm the sonographic diagnosis of renal AML, this algorithm is rarely followed in everyday clinical practice, especially in patients under age 50 years with masses less than 10 mm.

Adult↗
PubMed1995

Hepatic artery resistance changes in portal vein thrombosis.

PURPOSE: To determine if portal vein thrombosis (PVT) is associated with changes in the hepatic artery resistive index (RI) at Doppler ultrasonography (US). MATERIALS AND METHODS: In 35 patients with findings suspicious for PVT, prospective hepatic artery RIs were obtained before angiographic proof of portal vein status. RIs were also obtained from 27 age-matched patients with liver disease (without PVT) and from eight patients with PVT (without occlusion). RESULTS: Twenty-seven of the 35 patients had proved PVT and a significantly lower (P < .01) mean hepatic artery RI than did patients in any other group studied. Twelve of these 27 patients had RI values of .50 or less, while none of the patients in any other group studied had an RI value this low (specificity, 100%). CONCLUSION: A reduction in hepatic artery RI accompanies PVT and may be a helpful secondary sign to determine this venous abnormality.

Adolescent↗
PubMed1995

Hepatic artery resistance before and after standard meal in subjects with diseased and healthy livers.

PURPOSE: To assess fasting and postprandial resistive index (RI) in subjects with healthy and diseased livers. MATERIALS AND METHODS: Subjects with healthy (n = 10) and diseased (n = 33) livers underwent fasting and postprandial Doppler ultrasonography of the hepatic artery. Findings were compared with parameters for liver disease and Child class A-C and Child score of 5-15. RESULTS: The mean postprandial RI increase in healthy subjects was 42% (all, > or = 20%) and in patients with liver disease was 7% (six, > or = 20%). Patients with class A disease (n = 12) had a significantly greater increase in post-prandial RI (13%) than those with class B or C disease (3%) (P < .05). All patients with class C disease (n = 9) had an increased postprandial RI of less than 10%. The 13 patients with at least 10% increase in postprandial RI had less severe liver disease (Child score, 6.1 +/- 1.3 [standard deviation]) than the 20 patients with less than 10% increase (Child score, 8.4 +/- 1.7) (P < .01). CONCLUSION: A normal marked increase in postprandial RI is generally not seen in patients with severe liver disease.

Adult↗
PubMed1995

Positional variation in the Whitaker test.

PURPOSE: To describe positional variation in the outcome of the Whitaker test. MATERIALS AND METHODS: The authors retrospectively reviewed the cases of six patients in whom the pressure gradient during Whitaker testing varied by at least 10 cm of water and changed from normal ( < or = 13 cm of water) to abnormal ( > 13 cm of water) when patients were placed in different positions. RESULTS: Four patients had obstruction only in nonstandard positions. All had intermittent symptoms, and three had ureteral kinks at fluoroscopy. Two patients with ileal conduits had abnormal results in the standard position but normal results at repositioning related to compression of the conduits (seen as conduit distention at fluoroscopy). All six had undergone urinary tract surgery. Gradient differences with positional change ranged from 10 to > 38 cm of water. CONCLUSIONS: Whitaker testing in different positions may help identify intermittent obstructions that might otherwise go undetected or prevent inappropriate diagnosis of obstruction. Intermittent or unexplained symptoms, tortuous ureters, malpositioned kidneys, or previous surgery are indications for provocative positional testing.

Adult↗
PubMed1994

Effect of furosemide and intravenous normal saline fluid load upon the renal resistive index in nonobstructed kidneys in children.

Recent literature has shown that relative to baseline the renal resistive index remains unchanged in nonobstructed kidneys and increases in obstructed kidneys after administration of furosemide. To our knowledge the effect upon the renal resistive index of furosemide administered in conjunction with intravenous normal saline fluid load has not been reported. We evaluated the renal resistive index in 13 nonobstructed kidneys in 8 children 6 to 18 years old before and after furosemide and intravenous normal saline fluid load. The mean resistive index decreased from baseline (mean decrease was 0.06 +/- 0.06 standard deviation), with the observation of a resistive index decrease significant to p < 0.005). It appears likely that the combination of an intravenous normal saline fluid load and furosemide caused the resistive index decrease, since a decrease was not observed with furosemide alone; however, these results cannot exclude the possibility that the resistive index decrease was due to the intravenous normal saline fluid load alone. Nonetheless, these data are important since they may provide the foundation for the development of a pharmacologically challenged Doppler sonographic examination using furosemide and intravenous normal saline fluid load to evaluate better potentially obstructed kidneys.

Adolescent↗
PubMed1994

Diabetic nephropathy: evaluation with renal duplex Doppler US.

PURPOSE: To compare Doppler ultrasonography (US) with conventional clinical and laboratory tests in evaluation of diabetic renal disease. METHODS: Ninety-eight patients with diabetes mellitus underwent renal Doppler (resistive index [RI] measurement) US examination. US data were compared with clinical variables and follow-up data. RESULTS: Thirty-four diabetic patients without nephropathy had a mean RI of 0.62 +/- 0.09, which was not significantly different from the mean RI of 0.64 +/- 0.09 in 23 patients with early diabetic nephropathy. Patients with established nephropathy had a mean RI of 0.83 +/- 0.11, which was significantly (P < .001) higher than in the other two groups. Renal RI correlated highly with serum creatinine concentration (r = .64) and creatinine clearance rate (r = .80). An elevated RI (> or = 0.70) was associated with impaired renal function, increased proteinuria at 24 hours, and poor outcome. Absent diastole (RI = 1.0), observed in 7% of patients, was an ominous sign: Five of seven patients underwent dialysis or transplantation shortly after US. CONCLUSION: RI is typically elevated in established nephropathy but is often normal in the early clinical stages of disease. Renal Doppler US provides an accurate indication of renal function in diabetic nephropathy but does not offer a great advantage over conventional tests.

Adolescent↗
PubMed1994

Pulsus tardus: its cause and potential limitations in detection of arterial stenosis.

PURPOSE: To determine, with hydrodynamic experiments, the true cause of pulsus tardus, a Doppler waveform alteration that often occurs distal to an arterial stenosis. MATERIALS AND METHODS: A flow phantom was constructed with a pulsatile pump, interchangeable stenoses of varying degree, and interchangeable poststenotic segments of tubing with various degrees of compliance. With the transstenotic pressure drop held constant for each stenosis, Doppler waveforms were obtained before and after stenosis, while the degree of poststenotic vessel compliance was varied. RESULTS: The degree of pulsus tardus increased as the compliance of the poststenotic segment of vessel increased, independent of the transstenotic pressure drop. CONCLUSION: Poststenotic pulsus tardus is caused by the compliance of the poststenotic vessel wall in conjunction with the stenosis, which produces the tardus effect by damping the high-frequency components of the arterial waveform. This information will allow prediction of conditions that may produce false-positive or false-negative results when the tardus phenomenon is used to predict substantial upstream stenosis.

Blood Flow Velocity↗
PubMed1994

The effect of poststenotic vessel wall compliance upon the pulsus tardus phenomenon.

Recent studies have investigated the detection of significant arterial stenoses through identification of the "pulsus tardus" phenomenon in Doppler waveforms obtained distal to the stenosis. The etiology of this phenomenon, however, has not yet been determined. Using an in vitro model based upon an electrical circuit analogy, the authors had as their objective to determine whether the compliance of the vessel wall immediately distal to a stenosis, in conjunction with the stenosis, is the cause of pulsus tardus. For a constant stenosis, it was found that the degree of pulsus tardus, as quantitated by the acceleration index, increased as the compliance of the poststenotic segment increased. It is concluded that pulsus tardus distal to an arterial stenosis is likely due to the compliance of the normally distensible artery, in conjunction with the stenosis. Pathological conditions that alter the compliance of the poststenotic segment may affect the degree of pulsus tardus, perhaps limiting its usefulness for upstream stenosis detection.

Arterial Occlusive Diseases↗
PubMed1994

Intrarenal arterial Doppler sonography in the detection of renal vein thrombosis of the native kidney.

OBJECTIVE: Previous studies of transplant kidneys and recent reports on native kidneys have suggested intrarenal arterial Doppler findings can be helpful in the noninvasive workup of renal vein thrombosis. We used arterial Doppler sonography to evaluate cases of possible acute renal vein thrombosis in native kidneys that had equivocal results on standard Doppler analysis of the renal vein. MATERIALS AND METHODS: Twenty native kidneys in 12 patients with clinical findings suggestive of acute renal vein thrombosis had Doppler studies of the main renal vein that failed to show normal flow. In all 20 kidneys, duplex Doppler study of arcuate/interlobar intrarenal arteries was done and the resistive index was determined. The Doppler findings were compared with subsequent findings on either renal venograms (n = 11) or MR images (n = 9), which served as the reference "gold" standards. RESULTS: The prevalence of renal vein thrombosis was 25% (5/20). Ten kidneys had very abnormal findings on arterial Doppler studies (absent or reversed end-diastolic flow), but only two of these were proved to have renal vein thrombosis. In six other kidneys, end-diastolic flow was identified but the resistive index was still elevated (> or = 0.70), and only one of these kidneys was proved to have renal vein thrombosis. Four kidneys had normal arterial Doppler studies, and 50% (two) of these were proved to have renal vein thrombosis. When absent or reversed end-diastolic flow was used as a sign of renal vein thrombosis, intrarenal arterial Doppler analysis had a sensitivity of 40% (2/5) and a specificity of 47% (7/15). CONCLUSION: Unlike the reported experience in transplanted kidneys, intrarenal arterial Doppler analysis is neither sensitive nor specific for renal vein thrombosis in native kidneys. An intrarenal arterial Doppler study with normal findings should not prevent further workup if Doppler findings in the renal vein are equivocal, nor should absent or reversed end-diastolic arterial signals be considered highly suggestive of renal vein thrombosis.

Female↗
PubMed1994

Ultrasound of the abdomen.

In summary, ultrasonography and its recent advances appear ideally suited to a number of conditions common in the critically ill patient and the ICU setting. Depending on the clinical situation, and, providing appropriate technical expertise is available, ultrasonography can both gather diagnostic information and, where indicated, guide therapeutic intervention.

Abdominal Pain↗
PubMed1994

Renal duplex Doppler ultrasonography: a noninvasive predictor of kidney dysfunction and hepatorenal failure in liver disease.

Hepatorenal failure, a well-recognized complication of established liver disease, is characterized by early renal hemodynamic changes (vasoconstriction) before clinically recognized kidney disease. This renal vasoconstriction (increased renal vascular resistance) should be detectable noninvasively by Doppler ultrasonography. We studied whether renal Doppler ultrasonography detects abnormalities in patients with nonazotemic liver disease and its prognostic value for subsequent kidney status. We observed by renal Doppler ultrasonography 180 patients who had liver disease without azotemia. A simple parameter, resistive index, was derived for each subject on the basis of Doppler waveform analysis. Traditional parameters used to assess patients with liver disease were also recorded at the time of Doppler ultrasonography. Subsequent kidney outcomes were kidney dysfunction (doubling of initial creatinine level to 1.5 mg/dl [133 mumol/L]) or more and the presence or absence of the hepatorenal syndrome. Abnormal results of Doppler examinations (elevated resistive index) were seen in 76 (42%) of the 180 patients. Kidney dysfunction developed in 55% (42/76) of the patients with an elevated resistive index and 6% (6/104) of those with normal results of Doppler study (p < 0.00005). Hepatorenal syndrome developed in 26% (20/76) of subjects with an elevated resistive index and 1% (1/104) of those with a normal resistive index (p < 0.00005). Cox regression analysis identified resistive index as a significant independent predictor of subsequent hepatorenal syndrome (p < 0.00005) and kidney dysfunction (p < 0.00005). Renal duplex Doppler ultrasonography can noninvasively identify a subgroup of nonazotemic patients with liver disease that is at significantly higher risk for subsequent development of kidney dysfunction and the hepatorenal syndrome.

Adolescent↗
PubMed1993

Cutaneous T-cell lymphoma: CT in evaluation and staging.

Among 63 patients with cutaneous T-cell lymphoma (CTCL), 29% (n = 18) had positive computed tomographic (CT) findings, with frequencies of 65% (n = 13) among patients thought to have stages II-IV disease at clinical examination and 12% (n = 5) among patients thought to have stage I. Among eight patients with atypical CTCL variants such as cutaneous large-cell lymphoma, only one had negative findings at CT; extracutaneous disease was not suspected in five before they underwent CT. In contrast, CT findings were positive in only 5% (n = 2) of patients with classic early mycosis fungoides-type CTCL (scaling patches, small epidermotropic CD4+ cells), and CT is unlikely to provide substantial information in this patient subgroup. Contrary to earlier reports, the authors' data suggest that body CT is extremely useful in staging and evaluating patients with CTCL. CT should be included in the evaluation of atypical CTCL variants, Sézary syndrome, advanced-stage mycosis fungoides, and cases in which the CTCL subtype is unclear.

Aged↗
PubMed1993

Acute renal obstruction: evaluation with intrarenal duplex Doppler and conventional US.

To evaluate duplex Doppler ultrasound (US) in acute renal obstruction, bilateral intrarenal Doppler US was performed in 23 patients with unilateral renal obstruction (proved by means of intravenous urography) of 36 hours duration or less. A mean renal resistive index (RI) was calculated for each obstructed and normal contralateral kidney and compared with findings on conventional US scans. The mean RI in the obstructed kidneys was elevated (.77 +/- .07 [standard deviation]) and was higher than the mean RI in the normal contralateral kidney (.60 +/- .04) (P < .001). RIs in the obstructed kidneys were as follows: .75 or greater in 15 kidneys, .70-.74 (mild RI elevation) in five kidneys (but > or = .10 higher than the RI in the normal contralateral kidney), and less than .70 in three kidneys (two of these three patients had pyelosinus extravasation and one patient had clinical obstruction for only 4-5 hours). RI elevation occurred before collecting-system dilatation in four patients (17%). RI elevation occurs by 6 hours of clinical acute renal obstruction and may precede pyelocaliectasis. Renal duplex Doppler US contributes useful clinical information, especially when US is the first modality used to evaluate acute renal colic.

Acute Disease↗