The Relationship between Thymic Size and Vesicoureteral Reflux in Infants with Febrile Urinary Tract Infection

ABSTRACT

PURPOSE: Thymus is a lymphoproliferative organ that changes size in various physiological states in addition to some pathological conditions. Thymus is susceptible to involution, and shows a dramatic response to severe stress. Thymic measurements may be helpful in various diseases. UTI (urinary tract infection) is most common bacterial infection in infants and VUR (vesicoureteral reflux) is a common abnormality associated with UTI. In our study, the size of thymus was compared on the premise that a greater stress is exerted on the body when UTI is accompanied by VUR, than when occurs on its own. METHODS: Thymic size was measured on standard chest anteroposterior radiographs and expressed as the ratio between the transverse diameter of the cardiothymic image at the level of the carina and that of the thorax (CT/T). The medical records of 99 febrile urinary tract infection infants without other genitourinary anomalies except VUR were reviewed retrospectively. RESULTS: Among 99 patients with febrile UTIs, 25 were febrile UTI without VUR and 74 with VUR. For the UTI with VUR group, there was a significant decrease in the thymic size compared to the those without VUR group (0.382+/-0.048 vs 0.439+/-0.079, P<0.05). However, there were no differences in the duration of fever and WBC, CRP between the UTI with VUR and UTI without VUR. In addition, there were no differences in the cardiothymic/thoracic ratios between renal defects and renal scars in febrile UTI patients. CONCLUSION: The results of this study show that the shirinkage of thymus was more frequently found in the UTI patients with VUR. Therefore, awareness of the risks associated with thymic size is important for the appropriate work up and management of UTI patients.