Age, kidney function, and risk factors associate differently with cortical and medullary volumes of the kidney.

The kidney atrophies in patients with advanced chronic kidney disease (CKD) but factors influencing kidney size in normal adults are less clear. To help define this, we measured kidney volumes on contrast-enhanced computed tomographic images from 1344 potential kidney donors (aged 18-75 years). Cortical volume per body surface area progressively declined in both genders with increased age. Statistically, this was primarily dependent on the age-related decline in glomerular filtration rate (GFR). Independent predictors of increased cortical volume per body surface area were male gender, increased GFR, increased 24-h urine albumin, current smoker, and decreased high-density lipid cholesterol. Medullary volume per body surface area increased with age in men, while it increased with age in women until the age of 50 years followed by a subsequent decline. Independent predictors of increased medullary volume per body surface area were older age, male gender, increased GFR, increased 24-h urine albumin, increased serum glucose, and decreased serum uric acid. Thus, while cortical volume declines with age along the same biological pathway as the age-related decline in GFR, albuminuria and some risk factors are actually associated with increased cortical or medullary volume among relatively healthy adults. Underlying hypertrophy or atrophy of different nephron regions may explain these findings.

Stability evaluation of (18)F-FDG at high radioactive concentrations.

UNLABELLED: The objective of our study was to determine the concentration of ethanol, a known radiolytic stabilizer, needed to maintain stability for 12 h at an (18)F-FDG concentration of 19.7-22.6 GBq/mL (533-610 mCi/mL) at the end of synthesis (EOS). METHODS: (18)F(-) was formed by the (18)O(p, n)(18)F reaction using 16.5-MeV protons on a cyclotron. (18)F-FDG was synthesized using a synthesis platform. The final product was formulated in 15 mL of phosphate buffer. The synthesis took 22 min, delivering up to 336.7 GBq (9.1 Ci) of (18)F-FDG at the EOS. A series of 9 runs, 19.7-22.6 GBq/mL (533-610 mCi/mL), was completed. Three runs were doped with 0.1% ethanol, 3 with 0.2% ethanol, and 3 with no ethanol added. The radiochemical purity (RCP) was tested at about 1-h increments over a 12-h period. RCP was found by radio-thin-layer chromatography using aluminum-backed silica gel plates, acetonitrile, and water 90:10. An (18)F-FDG standard of 1 mg/mL was used to confirm radiochemical identity. The chromatography plates were analyzed on a radio-thin-layer chromatograph using a ß-detector. Residual solvents were also tested using gas chromatography with flame ionization detection and a capillary column. Other quality control measurements performed were pH and appearance. RESULTS: The 3 runs doped with 0.1% ethanol failed RCP after 5 h. The 3 runs using an ethanol concentration of 0.2% maintained stability through 12 h beyond the EOS. For these 3 runs, the radiolytic impurities were relatively constant at 6.1% ± 0.7% after 3 h. The runs using no ethanol failed RCP at 1 h. The pH varied between 5.3 and 6.1. Visual inspection was always clear and particulate-free. For the runs with 0.2% and 0.1% ethanol, the residual solvents were 0.21% ± 0.02% and 0.10% ± 0.02%, respectively. Regardless of ethanol concentration, chemical purity and identity passed quality control measurements. CONCLUSION: With the addition of 0.2% ethanol, (18)F-FDG (19.7-22.6 GBq/mL [533-610 mCi/mL]) kept stability through 12 h beyond the EOS. Each run passed stability parameters related to radiolysis-that is, radiochemical identity and RCP, chemical purity and identity, appearance, pH, and residual solvents.