showed an improvement over the preoperative split renal function in 19 patients (79%) and an improvement in drainage in 23 (96%). Conclusions The Anderson±Hynes pyeloplasty is an excellent procedure for treating pelvi-ureteric junction obstruction, and produces a lasting improvement in function and drainage in most patients. It is the`gold standard' against which newer techniques should be compared.

A new method for determining the glomerular filtration rate was analysed prospectively. The method uses an x ray fluorescence technique to measure disappearance from the plasma of injected non-ionic iodinated contrast media. Eighty seven patients were studied. Fifty four had an intravenous dose of 100 ml iohexol (Omnipaque) and 33 had 50 ml iohexol. Clearances of chromium-51 labelled edetic acid ("Cr-EDTA) were measured simultaneously. In the patients given 100 ml iohexol there was excellent correlation with 5"Cr-EDTA clearance (r=0-90). The correlation using 50 ml iohexol was also good (r=0-85). Correlation between creatinine clearance and clearance of 5Cr-EDTA in 33 patients was less satisfactory (r=0'69). There were no adverse reactions to the contrast media. The equipment used for measuring contrast clearance was robust and simple to operate. Freezing plasma samples in 10 studies and re-examining them weekly for six weeks showed no significant variation in results; hence reproducibility was good.This new and accurate method for determining the glomerular filtration rate merits further study and might find a useful place in routine clinical practice. IntroductionDetermination of the glomerular filtration rate to measure renal function is often required in urological, nephrological, and general medical practice. Currently available methods include inulin clearance, radionuclide studies using chromium-51 labelled edetic acid ("Cr-EDTA) or technetium-99m labelled diethylene triamine penta-acetic acid ('Tc-DTPA), and creatinine clearance. Because of the complexities ofthe first two methods clinicians often settle for creatinine clearance or even simple plasma creatinine and urea concentrations as less accurate but more convenient measures of renal function in everyday practice. We present our evaluation of a new method for determining the glomerular filtration rate. This is based on the use ofcompact, purpose designed equipment currently known as the ELX 84 (Elementanalys AB, Sweden), which measures the disappearance from plasma of injected, non-ionic iodinated contrast media by an x ray fluorescence technique.

The extent of laser light diffusion within prostatic tumor is of major importance in the treatment of localized prostatic cancer with photodynamic therapy (PDT). The penetration of 633 nm. wavelength red light was studied in eleven patients with suspected prostatic cancer using a novel method suitable for in situ measurements. Light delivery and detector fiber, placed interstitially within the gland, determined light attenuation at different interfiber separations. Of 11 patients, 10 had bilateral and 1 had single lobe studies. The mean +/- the standard error of the mean attenuation coefficients (sigma eff) for benign and malignant prostate tissue were 0.35 +/- 0.02 mm-1 and 0.36 +/- 0.02 mm-1, respectively, indicating similar optical densities (p = .58). Patients with bilateral lobe involvement showed little intraglandular variation in sigma eff (p = 0.23). However, there was interpatient variation (sigma eff = 0.28 to 0.48 mm-1) reflecting biological differences which, though therapeutically important, were not statistically significant (p = 0.057). This study showed that treatment requires individualization and predicted that 4 cylindrical diffusers are expected to destroy 25 ml. of prostatic tumor with PDT.