99mTc-DMSA late static planar imaging or SPECT is being used for the investigation of focal acute pyelonephritis (APN), especially in children with urinary tract infection (UTI). Diuretic ...99mTc-mercaptoacetyltriglycine (MAG3) dynamic scintirenography has been applied in the evaluation of kidney function and structure, frequently to exclude obstruction. However, in children and adults with a clinical picture of APN, diuretic MAG3 scintigraphy with zero time injection of furosemide (MAG3-F0) was observed to display focal parenchymal abnormalities; regional dysfunction (focal parenchymal decrease in early uptake; slow filling in and prolonged late retention of activity); or, less frequently, fixed defects. This observation was further studied both retrospectively and prospectively, and its sensitivity and specificity for APN were compared with those of dimercaptosuccinic acid (DMSA).
In the retrospective study, for 36 children with UTI and regional parenchymal findings on MAG3-F(0), data were reviewed, analyzed, and compared with the results of concurrent DMSA studies. In the prospective study, for 57 children with clinical and laboratory findings suggestive of APN, the 2 radiopharmaceuticals were used for imaging sequentially and the results of the 2 studies were compared. The criteria for abnormal findings compatible with the diagnosis of APN were, for MAG3-F(0), regional parenchymal dysfunction and fixed focal defects and, for DMSA, focal defects without parenchymal loss.
In all groups of patients, most abnormal MAG3-F(0) studies (80%) showed regional parenchymal dysfunction, but in some (20%) a fixed defect was found. Compared with DMSA and when both regional dysfunction and focal defects were considered, MAG3-F(0) was as sensitive as DMSA. Some patients had only MAG3-F(0) abnormalities, suggesting a slightly lower specificity for MAG3-F(0) compared with DMSA (86%); this finding needs further study, because it also raises questions about the sensitivity of DMSA, considering that only a small percentage of patients with clinically suggestive findings had abnormal study findings. In most patients with fixed defects on both DMSA and MAG3-F(0), follow-up studies showed no resolution, suggesting that a fixed defect on MAG3-F(0) may indicate either more severe APN or preexistent scars and that regional dysfunction may be a sign more specific for APN and prognostic of potential recovery. In addition, a pattern more specific for a scar--a fixed defect with a dilated regional calyx--was seen on follow-up MAG3-F(0).
A fast (25-min) planar dynamic MAG3-F(0) study was found to be as sensitive at depicting focal parenchymal abnormalities in APN as was the 3- to 4-h DMSA routine procedure. The sensitivity and specificity of both studies need further evaluation.
Accurate assessment of proteinuria in pediatric patients infected with the human immunodeficiency virus (HIV) is limited by constraints imposed by timed urine collections and low creatinine excretion ...in very ill patients with low muscle mass. We therefore sought to validate the use of random urine specimens to quantitate total protein and creatinine excretion in a population of 236 HIV-positive children. A mathematical derivation for estimating urine volume (V) was constructed. The accuracy of the final calculation V = 832 (kL/Ucr)BSA (where k = constant, L body length, UCr urine creatinine and BSA body surface area) was tested by regression analysis comparing the calculated and measured volume of 31 urines from ambulatory HIV-negative patients. The correlation coefficient was highly significant (r = 0.77, P < or = 0.0001). The relationship was also applied to 23 timed urine specimens from HIV-positive patients with similar significance (r = 0.87, P < 0.0001). A regression analysis of measured proteinuria against the urine protein: creatinine ratio (Upr/Ucr) in these same urines from the HIV-positive patients yielded a significant relationship both in the linear (r = 0.95, y = 0.4x) and the logarithmic regression (r = 0.97, y = x + 0.4). These data support the use of random Upr/Ucr ratios to estimate daily proteinuria in HIV-infected pediatric patients despite low creatinine excretion rates. The previously accepted values continue to apply, with Upr/Ucr < or = 2.0 considered normal and > 2.0 representative of nephrotic proteinuria.
We studied the fractional excretion of bicarbonate (FE HCO-3) in 10 low birth weight infants aged 1-6 days during metabolic acidosis (base excess greater than or equal to -5 mEq/l) and during ...subsequent sodium HCO-3 infusion. The mean birth weight was 1,095 g; the mean gestational age was 29 weeks. The ability to decrease urine pH to less than 5.5 and FE HCO-3 to less than 1% during metabolic acidosis was not limited by low gestational age or birth weight. After HCO-3 therapy, all infants corrected their negative base excess, and plasma HCO-3 increased significantly. All infants with blood pH less than or equal to 7.22 or PaCO2 greater than or equal to 50 mm Hg had minimal or absent FE HCO-3. Infants with elevated PaCO2 and mild or absent acidosis also had complete HCO-3 tubular reabsorption. These results suggest that the HCO-3 tubular reabsorption is adequate during metabolic and/or respiratory acidosis in low birth weight infants.
PDF
