Summary. To derive a formula for determination of 99mTc‐DTPA clearance (Cl) from the radioactivity in a single plasma sample, the relation Cl=ECV/ was used, where ECV is the extracellular volume and I is the mean transit time of the tracer in the organism. By studying 99mTc‐DTPA time activity curves of 45 consecutive patients we found that ECV could be estimated from the body surface area, and that I could be calculated from the radioactivity in a single plasma sample. Cl calculated by the single sample method was almost identical to Cl calculated by a standard multiple sample method (r=0·987). It is concluded that the single sample method is accurate and that it may prove useful as a routine method provided that (a) the method is not used in patients with 99mTc‐DTPA clearance less than 30 ml min‐1, since this investigation includes only patients with Cl>30 ml min‐1; (b) the method is not used for children, since the test material did not contain any children; (c) the method is only used for plasma samples drawn at 180≤t≤300 min.

To detect whether the nephrotoxicity of cis-diamminedichloroplatinum (DDP) is acute and can be demonstrated at an early stage in man, a method for estimating the function of the kidneys during intensive hydration was devised. The method includes a calculation of the clearance of 125I-orthoiodohippurate and an estimation of the glomerular filtration rate (GFR) from fast changes of the extracellular volume (ECV) and the mean transit time of 99mTc-DTPA in this volume. We examined nine patients with testicular cancer on 2 consecutive days for acute nephrotoxicity while they were undergoing treatment with cis-platinum. Placebo was given on day 1, cis-platinum on day 2. On both days the patients were hydrated with 4 l saline, glucose, and mannitol (0.51) over a period of 4 h, which resulted in an increase of 125I-orthoiodohippurate clearance on both days (P less than 0.01). The increase was, however, lower on the day of treatment with cis-platinum than on the day with placebo (P less than 0.05). There were no acute changes in the GFR. This indicates that treatment with DDP inhibits the active transport of 125I-orthoiodohippurate in the tubules; that is to say there is an acute effect on the kidney function. There were no acute changes in the GFR, but in the long-term followup study we found that the GFR had decreased significantly (P less than 0.05) after 2 months of treatment. During the first year after the initiation of treatment the GFR changes were found to progress. A significant increase in se-creatinine was not observed until 6 months after the initiation of treatment (P less than 0.05). The degree of chronic nephrotoxicity did not correlate in individual patients with the acute changes in kidney function.

Since the most essential function of the kidneys is to regulate the composition and volume of the extracellular fluids the ratio of the extracellular volume (ECV) to the glomerular filtration rate (GFR) seems to be a relevant index of kidney function. This ratio is equal to the mean transit time (t) of an injected ECV-distributed tracer that is exclusively eliminated from the body by glomerular filtration. In 26 patients t was estimated by means of standard methods after an intravenous injection of 99mTc-DTPA and was found to be correlated (r = 0.98) to the reciprocal final slope of the time-activity curve obtained by means of small CdTe-detectors pasted laterally on the crus, 10-12 cm below the knee joint. It is concluded that this external measurement of kidney function, without blood sampling, may shorten the usual procedure from 4 to 1 h. Furthermore, due to the constant detection geometry throughout the investigation it may provide the means for prolonged continuous monitoring of the kidney function at steady state and when rapid changes are expected.

A retrospective cohort of 163 male patients having either uni- (UI) or bilateral incision (BI) of the bladder neck to relieve infravesical obstruction was reviewed. Short-term results were excellent with significant improvement of flow rates. 82% (UI) and 87% (BI) of the incised patients were satisfied. Long-term results were assessed by a life-table analysis. 17% (UI) and 12% (BI) of the patients needed a reoperation during the observation period of 6 years. It is concluded that bladder neck incision is a method with few complications and favourable long-term results.