Children born prematurely have a high incidence of visual disorders which cannot always be explained by focal retinal or brain lesions. The aim of this study was to test the hypothesis that visual function in preterm infants is related to the microstructural development of white matter in the optic radiations. We used diffusion tensor imaging (DTI) with probabilistic diffusion tractography to delineate the optic radiations at term equivalent age and compared the fractional anisotropy (FA) to a contemporaneous evaluation of visual function. Thirty-seven preterm infants (19 male) born at median (range) 28(+4) (24(+1)-32(+3)) weeks gestational age, were examined at a post-menstrual age of 42 (39(+6)-43) weeks. MRI and DTI were acquired on a 3 Tesla MR system with DTI obtained in 15 non-collinear directions with a b value of 750 s/mm(2). Tracts were generated from a seed mask placed in the white matter lateral to the lateral geniculate nucleus and mean FA values of these tracts were determined. Visual assessment was performed using a battery of nine items assessing different aspects of visual abilities. Ten infants had evidence of cerebral lesions on conventional MRI. Multiple regression analysis demonstrated that the visual assessment score was independently correlated with FA values, but not gestational age at birth, post-menstrual age at scan or the presence of lesions on conventional MRI. The occurrence of mild retinopathy of prematurity did not affect the FA measures or visual scores. We then performed a secondary analysis using tract-based spatial statistics to determine whether global brain white matter development was related to visual function and found that only FA in the optic radiations was correlated with visual assessment score. Our results suggest that in preterm infants at term equivalent age visual function is directly related to the development of white matter in the optic radiations.
Introduction To evaluate the outcomes of retrograde intrarenal surgery (RIRS) and ultra-mini percutaneous nephrolithotomy (umPCNL) in the management of renal calculi. Material and methods Between March 2015 and January 2018, a total of 44 patients were treated with umPCNL. The outcomes of these patients were compared with 75 patients who underwent RIRS for renal calculi during the same time period. Results Median stone size was 9 mm in the umPCNL group and 7 mm in the RIRS group. Stone-free rates after a single procedure were achieved in 85% of patients for the RIRS group and 98% for the umPCNL group. 16% of RIRS patients were left with a ureteric stent, whilst 7% of patients (n = 5) needed a second RIRS. One patient in the umPCNL group was left with a percutaneous nephrostomy; all other patients were left totally tubeless. The mean operative time was 66 minutes in the RIRS group and 55 minutes in the umPCNL group (p = 0.04). The minor complication rates for the RIRS and umPCNL groups were 17% and 15%, respectively. One patient in the RIRS group required postoperative nephrostomy insertion; there were no major complications in the umPCNL group. The median length of stay was 0 days in the RIRS group and 1 day in the umPCNL group. Conclusions The overall study showed that umPCNL has low complication rates and good stone-free rates, with a lower requirement for ancilliary procedures. UmPCNL is an acceptable alternative in selected patients with small- to moderate-sized renal calculi.
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