In Vivo Fluorescence Microscopy of Microcirculation in the Renal Cortex of Mice

In vivo fluorescence microscopy was used for experimental studies of the renal cortical microcirculation in normal mice and in mice pretreated with the nephrotoxic drug cyclosporin A. The cortical circulation was studied after i.v. infusions of a nonionic low osmolar contrast medium (iohexol) and after infusions of mannitol. All infusions produced marked effects on the distribution and velocity of cortical blood flow with no differences between iohexol and mannitol. The renal cortical blood flow was inhomogeneous regarding different capillaries and there was an initial rise in the number of capillaries with increased blood flow after infusions of both mannitol and iohexol. There was simultaneously an increased number of capillaries with decreased blood flow following all infusions. The decreased blood flow after infusion of iohexol was more pronounced when the animals had been pretreated with cyclosporin A. The difference was only significant (p < 0.05) during a short part of the observation period of 30 min, but it may indicate that kidneys previously exposed to cyclosporin A are more susceptible to infusions of iohexol.

Urinary enzyme changes in children undergoing cineangiographic evaluation using iopromid

Nephropathy due to radiocontrast media presents with a wide spectrum of changes from reversible renal dysfunction to oliguria requiring dialysis. Nineteen patients (mean age 4.5 +/- 3.7 years) were included. Mean +/- SD values of the variables obtained before and 48 hours after angiography were the following: plasma creatinine: 0.6 +/- 0.10 and 0.6 +/- 0.16 mg/dl; endogenous creatinine clearance: 76.1 +/- 17.0 and 80.9 +/- 19.3 ml/min/1.73 m2; plasma osmolality: 279 +/- 23 and 298 +/- 39 mOsm/kg H2O; urine osmolality: 429 +/- 225 and 459 +/- 196 mOsm/kg H2O; fractional sodium excretion: 2.1 +/- 1.3% and 2.4 +/- 1.3%; plasma uric acid: 3.9 +/- 1.3 and 3.4 +/- 1.0 mg/dl; urinary AST/creatinine: 5.2 +/- 4.8 and 4.2 +/- 2.6 mU/mg; ALT/creatinine: 16.8 +/- 12.4 and 15.3 +/- 12.6 mU/mg; LDH/creatinine: 52.0 +/- 39.6 and 42.3 +/- 31.5 mU/mg; NAG/creatinine: 20.1 +/- 2.8 and 16.8 +/- 2.3 mU/mg, respectively. The changes in renal function parameters and urinary enzyme levels were insignificant statistically (p > 0.05). In conclusion, iopromid injection at maximum doses of 5 ml/kg does not result in injury to the tubular epithelium leading to increased urinary enzyme levels.

Iodinated contrast media-induced nephropathy: pathophysiology, clinical aspects and prevention

Administration of iodinated contrast media (CM) for radiographic purposes is a preoccupying cause of acute renal failure. This review of the literature deals with what is known about physiopathology, clinical course, risk factors and prevention. Factors involved in the pathophysiology of CM-induced acute renal failure are vasoconstriction, direct tubular cell injury and tubular obstruction by casts. In the case of pre-existing renal hypoperfusion, CM may disturb the complex interaction between factors which modulate renal haemodynamics by increasing vasoconstrictor factors, notably endothelin peptides. The renal medulla, a zone characterized by a high metabolic activity and a low oxygen tension, may be a specific target for CM-induced effects. CM-induced nephropathy (CMN) is essentially observed in patients with one or more associated risk factors (chronic renal failure, dehydration, diabetes mellitus with impaired renal function, multiple myeloma, large CM volume, intra-arterial rather than intravenous route, etc). There is much debate as to whether newer low osmolar CM (LOCM) are better tolerated than conventional high osmolar CM (HOCM). Most of the animal studies clearly demonstrate the advantages of LOCM over HOCM. Clinical literature is far more confusing, although some recent studies and one meta-analysis demonstrate that LOCM are better tolerated in patients with impaired renal function. The low number of comparative clinical trials carried out in high risk patients, wide variability in CMN definitions, limited number of patients enrolled and inadequacy of various selected endpoints may explain difficulties experienced in demonstrating this advantage. Furthermore, while hydration is correctly maintained during clinical trials, this is not always true in clinical practice. Such a discrepancy could lead to underestimation of the potential advantage of LOCM over HOCM. Effective prevention should associate the correct hydration of patients, identification and, when possible, optimal correction of risk factors, avoidance of repeated CM injections within a short period of time and temporary disruption of treatment with other nephrotoxic drugs (non steroidal antiinflammatory drugs, aminoglycosides, etc).