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Background Baseline serum creatinine (bSCr) is required for diagnosing acute kidney injury (AKI). In children, bSCr is commonly defined as the lowest measurement within 3 months of admission. Measured values are often missing and estimating bSCr using height-based glomerular filtration rate (GFR) equations is problematic when height is unavailable. Methods This is a retrospective cohort study including 538 children admitted to the intensive care unit (ICU) between 2003 and 2005 at two centers in Canada, with measured bSCr, height, and ICU-SCr values. We evaluated the bias, accuracy, and precision of back-calculating bSCr from height-dependent and height-independent GFR equations. Agreement of AKI defined using measured and estimated bSCr was calculated. Multivariate analyses were performed to assess the impact of bSCr estimation methods on the association between AKI and ICU mortality, length of stay, and duration of mechanical ventilation. Results Both methods underestimated bSCr by 1-3%, showed good accuracy (~30% of patients with estimated bSCr within 10% of measured bSCr), but poor precision (wide 95% limits of agreement). The agreement between AKI defined by estimated versus measured bSCr was >80% ([kappa] >0.5). The height-independent method performed best in children >13 years old; however, overall, both methods performed similarly across age subgroups. AKI was associated with longer stay, prolonged mechanical ventilation, and ICU mortality using measured and estimated bSCr. Conclusions Height-dependent and height-independent bSCr estimation methods were comparable. This may have significant implications for performing pediatric AKI research using large databases, and in clinical care to define AKI when height is unknown., Author(s): Erin Hessey [sup.1] , Rami Ali [sup.2] [sup.3] , Marc Dorais [sup.4] , Geneviève Morissette [sup.5] , Michael Pizzi [sup.1] , Nikki Rink [sup.7] , Philippe Jouvet [sup.6] , [...]

Background The current glomerular filtration rate (GFR) equation (CKiD) may be less accurate in adolescents and children with higher GFR. Methods This was a retrospective study (n = 161, 247 .sup.99mTc DTPA-GFRs). Six equations were evaluated for bias, accuracy, and low GFR diagnosis: (1) CKiD; (2) historic center; (3) Hoste(age); (4) Hoste(height); (5) modified Pottel; (6) Gao. Children with [greater than or equal to] vs. Results Most equations underestimated GFR by 1-14 % in the higher GFR group, least so for Hoste(age). In the low GFR group, Hoste(age) and historic center overestimated GFR significantly more than CKiD (p < 0.05). Accuracy (within 30 % GFR) was similar across equations and GFR subgroups (66-86 %). In the [greater than or equal to]16 years group, CKiD underestimated GFR by ~10 %, vs. ~3 % for Hoste(height). Accuracy was 5-10 % lower in the older group and most equations were more sensitive than specific for detecting low GFR; this discrepancy was less for the Hoste equations. Adult equations were highly inaccurate. Conclusions GFR estimation in older children and with higher GFR is suboptimal. The Hoste(height) may be an alternative GFR estimation method; Hoste(age) may allow for height-independent GFR estimation in patients with normal GFR., Author(s): Nikki Rink[sup.1] , Michael Zappitelli[sup.1] Author Affiliations: (1) Department of Pediatrics, McGill University Health Centre, Montreal Children's Hospital, 2300 Tupper, Room E-213, H3H 1P3, Montreal, QC, Canada Introduction Glomerular [...]

Hereditary distal renal tubular acidosis (dRTA) is caused by mutations of genes encoding subunits of the H+-ATPase (ATP6V0A4 and ATP6V1B1) expressed in α-intercalated cells of the distal renal tubule and in the cochlea. We report on a 2-year-old girl with distal RTA and profound speech delay which was initially misdiagnosed as autism. Genetic analysis showed compound heterozygous mutations with one known and one novel mutation of the ATP6V1B1 gene; cerebral magnetic resonance imaging (MRI) revealed bilateral enlargement of the endolymphatic sacs of the inner ear. With improved cooperation, audiometric testing showed that hearing loss was most profound on the right, where endolymphatic sac enlargement was greatest, demonstrating a clear link between the degree of deafness and the degree of inner ear abnormality. This case indicates the value of MRI for diagnosis of inner ear involvement in very young children with distal RTA. Although citrate therapy quickly corrects the acidosis and restores growth, early diagnosis of deafness is crucial so that hearing aids can be used to assist acquisition of speech and to provide enough auditory nerve stimulation to assure the affected infants remain candidates for cochlear implantation.