Determination of the left to right dimercaptosuccinic acid (DMSA) uptake ratio is theoretically one of the easiest quantitative procedures in nuclear medicine. The quantification can be performed on the posterior view, with or without the lateral view for correction of kidney depth. The geometric mean can also be determined using both the anterior and the posterior views. The aim of this study was to evaluate the occurrence of remarkable differences in the results from quantification of the relative renal function using the geometric mean and those obtained using the posterior counts only. Moreover, we evaluated to what extent the patient age influenced these differences. We reviewed 328 99Tcm-DMSA scans. The difference between the relative renal function obtained using the posterior view and that obtained using the geometric mean was calculated and analysed statistically. For the purpose of evaluating the value of performing the geometric mean calculation in patients of different ages, patients were divided into four age groups (group I, < or =2 years; group II, 3-9 years; group III, 10-18 years; group IV, >18 years). Using the Student's t test, no statistical differences were found in the relative renal function obtained by the two methods (posterior projection and geometric mean) in groups I (t = 0.01, P = 0.992) and II (t = 1.43, P = 0.155), which consisted of patients younger than 10 years (77% of the patients). In groups III and IV statistical differences were found (t = 2.27, P = 0.028 and t = 2.170, P = 0.038), respectively. We conclude that for children under 10 years it is unnecessary to perform depth correction using the geometric mean except in rare cases of major malformations and position anomalies.

Fig. I. A photograph of the dorsum of both hands shows the skin to be smooth and shining. Thickened, horny plates and warty nodules are observed HistoryThis 16-year-old white male presented in the Dermatology Clinic because of erythroderma and hyperkeratosis. The condition had been present since birth, consisting of a dull erythema, generalized from the beginning and most intense in the flexures. The skin was smooth, shining, and thickened. Horny plates and warty nodules, both irregular and linear, were observed. These were particularly present at the sides and back of the neck, around the umbilicus, on the areola of the nipples and the limb flexures, including the hands and feet (Fig. 1). The nails exhibited progressive hour-glass deformity without associated clubbing.In the past history, generalized edema had been observed shortly after birth, subsiding spontaneously in a few days. At the age of 10 years, the patient started to develop bilateral ectropion and because of infection the left eye was enucleated at the age of 12 years.The remainder of the history was not contributory except for the information that the parents of the patient were first co usins.Roentgenograms of the hands ( Figs. 2A and B) and feet were obtained. Fig. 2A and B. Posteroanterior roentgenograms of both hands demonstrate resorption of the terminal tufts of most of the distal phalanges. The surrounding soft tissues are noted to be thickened and the normal fissures of the skin appear to be randomly dispersed (the changes in the feet were similar but less severe)