Retrospective study of children with acute pyelonephritis. Evaluation of bacterial etiology, antimicrobial susceptibility, drug management and imaging studies.

The purpose of the study was to investigate the management of pyelonephritis in a large Italian pediatric population. A total of 1,333 patients (36% male) were considered. Escherichia coli was the most frequently isolated agent (89.9%), followed by Proteus mirabilis (3.6%) and Klebsiella oxytoca (2.1%). 27% of microorganisms were resistant to amoxicillin, 4% to amoxicillin/clavulanic acid, 11% to trimethoprim-sulfamethoxazole, 2.4% to gentamicin and less than 2% to ceftazidime. Despite this resistance pattern showing that oral antibiotics, such as amoxicillin/clavulanic acid, are effective in vitro as well as parenteral antimicrobials, a parenteral antibiotic was given initially to 756 (57.2%) children. A prophylactic regimen was started in 922 patients with a rate of reinfection during prophylaxis of 9.5%; a higher rate of reinfection was observed in patients with reflux (25%) compared to children without reflux (3%) (p < 0.0001). Vesicoureteral reflux was demonstrated in 30% of patients. The number of renal abnormalities detected by DMSA in patients with and without reflux was significantly different (p < 0.001). CRP was higher in patients with scars (p < 0.02). In conclusion, pyelonephritis represents a common disease with about 2,500 days of hospitalization per year in the Veneto Region where there is a pediatric population of about 800,000 under 15 years of age. The results of antimicrobial in vitro tests indicate that amoxillicin/clavulanic acid could represent the antibiotic of choice. The high frequency of malformations, observed even in children between 6 and 12 years of age, may suggest the need of an imaging study including DMSA scan and VCUG in all age groups.

Determination of inulin in plasma and urine by reversed-phase high-performance liquid chromatography.

We report a new HPLC procedure for measuring inulin in plasma and urine. Samples after dilution are boiled in mild acidic conditions and then analyzed on a C18 column. Solvent system A is 3.2 mM HCl, pH 2.5, and B is acetonitrile-3.2 mM HCl (60:40, v/v), pH 2.5. The separation is carried out in 8 min with a flow-rate of 1.0 ml/min and the absorbance monitored at 280 nm. The relationship between inulin and the recorded peak area is linear from 0.2 to 3.2 mg/ml with a correlation coefficient of 0.999 for plasma and 0.999 for urine. Within-run precision, measured at three inulin concentrations, ranged from 0.9 to 1.7% in plasma and from 0.8 to 1.2% in urine. Between-run precision varied in plasma from 2.7 to 3.2% and in urine from 3.0 to 3.3%. Analytical recovery ranged from 102 to 107% in plasma and from 101 to 105% in urine, respectively. The method is sensitive, selective and only 30-microliters samples are required. Therefore, it could be used to evaluate the glomerular filtration rate even in small babies and to perform studies in animals.

Determination of 8-methoxypsoralen in plasma by gas chromatography-mass spectrometry using selected-ion monitoring.

A sensitive and accurate assay was developed for the measurement of 8-methoxypsoralen in plasma using electron-impact positive-ion mass fragmentography. 4,5,8-Trimethylpsoralen was used as an internal standard. Sample preparation consisted of a two-step liquid phase extraction using acetonitrile and methylene chloride. The calibration curve showed a linear relationship between the peak areas of 8-methoxypsoralen and 4,5,8-trimethylpsoralen over a wide range of 8-methoxypsoralen concentrations (1-500 ng/ml). With-in- and between-run precisions, measured at five different drug concentrations, varied from 0.82 to 1.41% and from 0.82 to 1.86%, respectively.

Determination of urinary orotate excretion by high-performance liquid chromatography.

A new reversed-phase high-performance liquid chromatographic procedure for the determination of urinary orotate excretion is described. It is a selective, sensitive and rapid method, suitable for the differentiation of inherited metabolic diseases with abnormal orotate metabolism.