Intracranial arteriovenous malformations. Observations after experience with computerised tomography.
Thirty-six patients with angiographically confirmed intracranial arteriovenous malformations have had computerised tomographic scans performed as part of their investigation. This study demonstrates the incidence of haematoma formation after haemorrhage, the frequency of calcification not visible on plain radiographs, and describes the possible causes for a complicating hydrocephalus. Further information has been gained from the intravenous injection of sodium iothalamate (Conray 420), with comparison of the scans taken before and after the injection. (+info)
Rapid and accurate assessment of glomerular filtration rate in patients with renal transplants using serum cystatin C.
BACKGROUND: Assessment of renal function in patients with renal transplants is of great importance. Various studies have reported cystatin C as an easily and rapidly assessable marker that can be used for accurate information on renal function impairment. To date, no study is available to define the role of cystatin C in patients with renal transplants. METHODS: Thirty steady-state patients (50% male/50% female) with status post-kidney transplantation were studied. To assess renal function, cystatin C, creatinine clearance, serum creatinine, beta2-microglobulin (beta2M), and [125I]iothalamate clearance were determined. Correlations and non-parametric ROC curves for accuracy, using a cut-off glomerular filtration rate (GFR) of 60 ml/min, were obtained for the different markers allowing for calculations of positive predictive values (PPV), positive likelihood ratios (PLR), specificity and sensitivity, respectively. Further, to evaluate the usefulness of these markers for monitoring, intraindividual coefficients of variation (CVs) for cystatin C and creatinine measurements were compared in 85 renal transplant patients. Measurements consisted of at least six pairs of results, which were obtained at different time points during routine follow-up. RESULTS: Cystatin C correlated best with GFR (r=0.83), whereas serum creatinine (r=0.67), creatinine clearance (r=0.57) and beta2M (r=0.58) all had lower correlation coefficients. The diagnostic accuracy of cystatin C was significantly better than serum creatinine (P=0.025), but did not differ significantly from creatinine clearance (P=0.76) and beta2M (P=0.43). At a cut-off of 1.64 mg/l, cystatin C has a PPV of 93%, PLR of 6.4, specificity 89% and sensitivity 70%, respectively. For beta2M, PPV 83%, PLR 1.7, specificity 67% and sensitivity 75% was seen at a cut-off of 3.57 mg/l. Accordingly, at a cut-off of 125 micromol/l for serum creatinine, a PPV 76%, PLR 1.4, specificity 44% and sensitivity 80% was revealed. Finally, at a cut-off of 66 ml/min/1.73 m2 for creatinine clearance, the following characteristics were found: PPV 94%, PLR 7.7, specificity 89% and sensitivity 85%. The intraindividual variation of creatinine was significantly lower than that of cystatin C (P<0.001). With increasing concentrations, their ratios of CV tended towards a value of 1, demonstrating identical variability at low GFR. CONCLUSION: Together, our data show that in patients with renal transplants, cystatin C, in terms of PPV and PLR, has a similar diagnostic value as creatinine clearance. However, it is superior to serum determinations of creatinine and beta2M. The intraindividual variation of cystatin C is greater than that of creatinine. This might be due to the better ability of cystatin C to reflect temporary changes especially in mildly impaired GFR, most critical for early detection of rejection and other function impairment. Thus, cystatin C allows for rapid and accurate assessment of renal function (GFR) in renal transplants and is clearly superior to the commonly used serum creatinine. (+info)
Effect of intracranial pressure of meglumine iothalamate ventriculography.
Intraventricular pressure was studied in 12 patients undergoing ventriculography with a water soluble positive contrast medium. Isovolumetric instillation of meglumine iothalamate into the lateral ventricles and the anterior part of the third ventricle caused only a small increase in ventricular fluid pressure (1.3 +/- 0.3 mmHg), but the pressure increased markedly (46.3 +/- 3.7 mmHg; P less than 0.001) when the contrast medium entered the posterior end of the third ventricle, aqueduct of Sylvius,, and fourth ventricle. This sharp increase in intracranial pressure could not be attributed solely to the postural changes or to alterations in arterial blood pressure. Possible mechanisms are discussed. (+info)
Scintigraphic imaging of a blind-ending ureteral duplication.
The scintigraphic image is compared with the urographic appearance of blind-ending ureteral duplication. (+info)
Changes in intrarenal oxygenation as evaluated by BOLD MRI in a rat kidney model for radiocontrast nephropathy.
The pathogenesis of radiocontrast nephropathy is poorly understood. In an animal model, inhibition of the synthesis of nitric oxide and prostaglandins appears to predispose rats to severe renal injury following the administration of radiocontrast. Here we have investigated whether administration of radiocontrast, as well as changes in renal medullary oxygenation following pharmacologic inhibition of nitric oxide and prostaglandin synthesis, might be evaluated by blood oxygenation level-dependent (BOLD) MRI. Nineteen anesthetized (Inactin 100 mg/kg) rats were studied. BOLD MRI measurements were performed following administration of L-NAME (N-nitro-L-arginine methyl ester, 10 mg/kg), Indomethacin (10 mg/kg), and a radiocontrast agent (sodium iothalamate 60%, 6 mL/kg). Marked sequential changes in medullary R(*)(2), presumably reflecting decline in medullary pO(2), were noted after each of the pharmacological interventions employed. These results, obtained by noninvasive MRI, are consistent with prior direct recordings of pO(2) and doppler flow in the rat renal medulla after administration of L-NAME, Indomethacin and iothalamate. Medullary oxygenation in rats was reduced by inhibition of the synthesis of prostaglandins and nitric oxide, as well as by intravenous injection of radiocontrast agents. BOLD MRI can noninvasively evaluate changes in medullary oxygenation in rats that appear to predispose acute renal failure. J. Magn. Reson. Imaging 2001;13:744-747. (+info)
A functional comparison of the cortical collecting tubule and the distal convoluted tubule.
Electrical and permeability features of the distal convoluted tubule (DCT) and the cortical collecting tubule (CCT) were examined using the technique in which isolated segments of rabbit tubules were perfused in vitro. When rabbits were given a regular diet and tubules were perfused and bathed in artificial solutions simulating plasma ultrafiltrate, the potential difference (PD) was +3.7 plus or minus 1.9 mV in the CCT and -40.4 plus or minus 2.8 mV in the DCT. When rabbits were given a low sodium, high potassium diet plus i.m. deoxycorticosterone acetate (DOCA) (1 mg/kg per day), the PD in both the CCT (-30.8 plus or minus 3.9 mV) and the DCT (-33.8 plus or minus 5.5 mV) was negative. The PD in the CCT was quantitatively similar to that of diet plus DOCA when animals were given DOCA alone. The PD in both segments was inhibited by ouabain (10-minus 5 M) in the bath or by amiloride (10-minus 5 M) in the perfusate. Addition of vasopressin (200 muU/ml) to the bath caused a gradual decline of PD to zero in the CCT but failed to produce a potential response in the DCT. Osmotic water permeability was essentially zero in both segments in the absence of vasopressin. After addition of the vasopressin to the bath, osmotic water permeability in the DCT remained zero but increased to 71.9 plus or minus 25.5 X 10-minus 7 cm/s per atm in the CCT. We conclude that both segments are similar in that each possesses an electrogenic transport process but that these segments differ in that: (a) the CCT requires either exogenous or endogenous mineralocorticoid to maintain a maximal negative PD, whereas the PD in the DCT appears to be independent of mineralocorticoid effect; and (b) the CCT responds to vasopressin with a marked rise in water permeability, whereas the DCT is impermeable to water before and after addition of vasopressin. (+info)
A natriuretic principle derived from kidney tissue of volume-expanded rats;.
Homogenates of kidneys from hydropenic and volume-expanded rats were subjected to gel filtration with Sephadex G-25. A fraction of the eluate coincident with the fourth UV peak was injected into the aorta of rats with one kidney excluded. A fraction eluting before the albumin peak was utilized as a control. Significant natriuresis and diuresis were observed after infusion of the fraction obtained from volume-expanded kidneys but not after infusion of the fraction from hydropenic kidneys or the control fraction. The natriuresis occurred in in the absence of changes in mean blood pressure, hematocrit, plasma sodium and potassium, glomerular filtration rate, and potassium excretion. The response was apparent immediately after infusion and persisted for up to 150 min. These results verify the existence of a low molecular weight natriuretic substance which may be preferentially bound to the kidney after its volume-stimulated release into the circulation. (+info)
Functional effects of renal artery stent placement on treated and contralateral kidneys.
BACKGROUND: This study examined the effects of stent placement for renal artery stenosis on the function of treated and contralateral kidneys. METHODS: Eighteen patients who underwent stent placement for unilateral renal artery stenosis presenting with hypertension and/or renal failure were studied before angiography and stent placement and at their one-year follow-up. Renal vein blood samples were taken at both sides, at each side simultaneously with a sample from the aorta, to measure the plasma renin concentration and the concentrations of 131I-hippuran and 125I-thalamate during constant systemic infusion of these radiochemicals. This allowed an assessment of the single-kidney contributions to the total renin secretion, effective renal plasma flow (131I-hippuran clearance) and glomerular filtration rate (125I-thalamate clearance). RESULTS: At the one-year follow-up, the vein-to-artery renin ratio at the treated side had decreased to normal, from 1.65 +/- 0.131 to 1.23 +/- 0.076 (mean +/- SEM; P = 0.011), indicating an improved renal blood flow. Contralaterally it rose from 1.09 +/- 0.042 to 1.17 +/- 0.029 (P = 0.055) at follow-up. The extraction ratio of 131I-hippuran improved at the treated side (0.48 +/- 0.049 to 0.62 +/- 0.034; P = 0.003) and contralaterally (0.67 +/- 0.033 to 0.73 +/- 0.026; P = 0.043). The extraction ratio of 125I-thalamate, which equals filtration fraction, improved at both sides (0.12 +/- 0.014 to 0.17 +/- 0.012 at the treated side, P = 0.001; 0.18 +/- 0.013 to 0.22 +/- 0.011 contralaterally, P = 0.002). Two-kidney effective renal blood flow and glomerular filtration rate remained unchanged. CONCLUSION: Renal artery stenting was capable of causing improvement of glomerular filtration rate of the treated kidney, although the overall glomerular filtration rate did not change. (+info)