Patterns of damage observed on dimercaptosuccinic acid kidney scans and future risk of urinary tract infections or reduced kidney function

Background: ^99mTc-Dimercaptosuccinic acid (DMSA) scan is highly accurate for assessing functional imaging of the kidney parenchyma. Kidney damage observed on DMSA scan is associated with future development of chronic kidney disease. This study aims to differentiate between different patterns of damage observed on DMSA scan and determine their predictive clinical value. Methods: We reviewed first-in-life DMSA scans performed ≥ 4 months post febrile urinary tract infection (UTI) or for suspected congenital kidney abnormalities, in a single referral center, from November 2007 to February 2011. DMSA uptake patterns were classified as normal; peripheral focal defects; diffuse inhomogeneity in tracer distribution within kidney parenchyma; and the combination of both patterns. Subsequent UTIs and estimated glomerular filtration rate (eGFR) were recorded at last follow-up. Results: One hundred five patients met inclusion criteria, and 57 (54%) were females. Median (IQR) age at scan was 2 (1.3, 5.1) years. Fourteen patients (13.3%) had focal defects, 29 (27.6%) had diffuse inhomogeneity and 9 (8.6%) had diffuse inhomogeneity with focal defects. After a mean follow-up period of 9.6 ± 3.3 years (available for 99 children), 29 (29%) patients experienced recurrent UTIs [median (IQR) episodes: 2 (1, 5)]. UTI tendency differed between groups (focal defects: 71.4%; diffuse inhomogeneity with focal defect: 44.4%; diffuse inhomogeneity only: 22.2%; normal scan: 18.3% p < 0.001). On multivariate analysis only the presence of focal defects predicted recurrent UTIs [OR (95%CI): 3.89 (1.2, 12.6), p = 0.024]. The percentage of patients with an eGFR < 75 ml/min/1.73 m², was highest in patients with diffuse inhomogeneity with focal defects compared to patients with normal scans, focal defects only or diffuse inhomogeneity only (22% vs. 2%, 0% and 3.7% respectively, p = 0.032). Conclusions: Focal defects on DMSA scan, likely representing post pyelonephritis scars, are a strong predictor of recurrent UTIs. Patients with diffuse inhomogeneity with focal defects on scan have the highest risk of reduced eGFR during follow-up.