Functional evaluation by quantitative dimercaptosuccinic Acid scintigraphy after kidney trauma in children

Most pediatric surgical teams have adopted nonoperative treatment for a traumatic kidney lesion in children. In the emergency setting and at long-term followup dimercaptosuccinic acid (DMSA) scintigraphy enables us to identify the consequences on global renal function as well as on the function of each individual kidney.

Eight boys and 12 girls between 0.6 and 15.9 years old (average age 9.7) were evaluated after including renal trauma, minor and major injury in 10 each. Scintigraphy was performed 8 days and 6 months after injury. The tracer used was 2 MBq./kg. Tc-DMSA. Semiquantitative analysis of the images consisted of determining 2 parameters, namely relative renal function, corresponding to the fraction of activity of a single kidney compared to the activity of the 2 kidneys, and the calculated renal activity fraction, corresponding to the function of each kidney compared with the activity of a theoretical kidney in a child of the same age. The posttraumatic renal scintigraphy series was paired with a series of healthy children matched by age, weight, height, sex and affected side of function as a control group. Global renal function was also measured using a formula based on ethylenediaminetetraacetic acid scintigraphy with the height, weight and increased serum creatinine in each patient.

For minor injuries the quantitative functional evaluation revealed a significant average loss of renal function +/- SD on the side of the lesion (12.8% +/- 3.1% versus 18.3% +/- 2%, p = 0.001). For major injuries on relative renal function evaluation we noted an average 36-point difference in the damaged and contralateral kidneys 8 days after the accident. Six months after trauma we noted a definitive loss of 48% in the calculated renal activity fraction on the side of the lesion. There was no compensatory hypertrophy on the noninjured side when the calculated renal activity fraction was compared with that of a normal kidney in a control patient (mean 19.1% +/- 4.2% versus 19.5% +/- 3.7%, not significant). Creatinine clearance was normal in each patient. DISCUSSION A renal contusion always induces parenchymal loss. Major kidney trauma has significant consequences on the opposite side. At 6 months the presumably uninjured contralateral kidney may be limited in its ability to compensate through hypertrophy, which worsens the global renal functional prognosis of a traumatic but initially unilateral lesion.

Posttraumatic functional evaluation by DMSA scintigraphy, which measures the nephron capital of each kidney and the 2 together, seems essential to inform patients about the seriousness of the lesion and lead them to an eventual long-term nephrological followup with regular blood pressure assessment.