What is interstitial fluid? Biochemical and physiological analysis of fluid obtained from tissue cages.

Multiperforated polypropylene balls implanted in soft-tissue and renal parenchyma deliver fluid which represents interstitial fluid, which was characterized biochemically and physiologically. In a time-concentration study, the serum antibiotic level was compared to levels in interstitial fluid of the kidney (RIF), interstitial fluid of soft-tissues of the abdominal wall (STIF) and urine, measured simultaneously after intravenous injection of six different antibiotics. A direct time-concentration relationship between the concentration of antibiotics in the serum and in the renal interstitial fluid was found. This study helps delineate the basic pharmacokinetics in renal interstitial tissue and suggests guidelines for optimal therapy in renal parenchymal infections.