Risk of peritoneal dialysis catheter-associated peritonitis following kidney transplant.

OBJECTIVE: Peritoneal dialysis (PD) patients have equivalent or slightly better kidney transplant outcomes when compared to hemodialysis (HD) patients. However, given the risk for postoperative infection, we sought to determine the risk factors for PD catheter-associated infections for patients who do not have the PD catheter removed at the time of engraftment. METHODS: Demographic and outcomes data were collected from 313 sequential PD patients who underwent kidney transplant from 2000 to 2015. Risk factors for postoperative peritonitis were analyzed using logistical regression. RESULTS: Of 329 patients with PD catheters at transplant, 16 PD catheters were removed at engraftment. Of the remaining 313 patients, 8.9% suffered post-transplant peritonitis. On univariate analysis, patients with peritonitis were significantly more likely to have used the PD catheter or HD within 6 weeks after transplant. Multivariate analysis had similar findings, with increased risk for those using the PD catheter after transplant, with a trend for those who underwent HD only within 6 weeks of transplant. CONCLUSION: These results suggest that delayed graft function requiring any type of dialysis is associated with increased post-transplant peritonitis risk.

Ureteroscopic High-Frequency Dusting Utilizing a 120-W Holmium Laser.

INTRODUCTION AND OBJECTIVE: Recently there has been interest in a dusting technique for lithotripsy during ureteroscopy (URS) utilizing high-frequency and low-pulse energy (HiFr-LoPE) settings. We assessed a 120-W holmium laser that permits high-frequency (>50 Hz) dusting. MATERIALS AND METHODS: Consecutive URS cases performed by a single surgeon using the P120H (Lumenis, San Jose, CA) were reviewed. Lithotripsy was performed using HiFr-LoPE settings (50-80 Hz/0.2-0.5 J [10-40 W]). Residual fragments (RFs) were determined on postoperative radiography, ultrasonography, or CT. Complications were classified using the Clavien-Dindo grade. RESULTS: URS was performed on 82 renal units (71 patients). Renal stones constituted the majority (73%), including four partial staghorn stones. Mean stone size and density (HU) were 12.5 mm (SD 8.7; range 5.0-50.0) and 993 (SD 353; range 230-1580), respectively. Ureteral access sheath was used in 15 (21%) patients. Mean total laser energy per case was 5.2 kJ (range 0.1-42.1). Dusting was exclusively performed in 84% of cases. Postoperative stents were placed in 91% (41% string). Zero-fragment and ≤2 mm RF rates were 62.1% and 74.2%, respectively. There were 11 complications (13%) (grade 1 = 5, grade 2 = 6). The emergency department visit rate was 5.6%. There were no hospitalizations or reinterventions. CONCLUSIONS: Refinements in laser technology have expanded methods to ablate urinary stones. Outcomes utilizing a dusting technique demonstrated acceptable RF and complication rates. However, not all stones are amenable to dusting, and further study is needed to define the optimal role of this technique during laser lithotripsy.

Color-detection thresholds in rhesus macaque monkeys and humans.

Macaque monkeys are a model of human color vision. To facilitate linking physiology in monkeys with psychophysics in humans, we directly compared color-detection thresholds in humans and rhesus monkeys. Colors were defined by an equiluminant plane of cone-opponent color space. All subjects were tested on an identical apparatus with a four-alternative forced-choice task. Targets were 2° square, centered 2° from fixation, embedded in luminance noise. Across all subjects, the change in detection thresholds from initial testing to plateau performance ("learning") was similar for +L − M (red) colors and +M − L (bluish-green) colors. But the extent of learning was higher for +S (lavender) than for −S (yellow-lime); moreover, at plateau performance, the cone contrast at the detection threshold was higher for +S than for −S. These asymmetries may reflect differences in retinal circuitry for S-ON and S-OFF. At plateau performance, the two species also had similar detection thresholds for all colors, although monkeys had shorter reaction times than humans and slightly lower thresholds for colors that modulated L/M cones. We discuss whether these observations, together with previous work showing that monkeys have lower spatial acuity than humans, could be accounted for by selective pressures driving higher chromatic sensitivity at the cost of spatial acuity amongst monkeys, specifically for the more recently evolved L − M mechanism.

Sensitivity to numerosity is not a unique visuospatial psychophysical predictor of mathematical ability.

Sensitivity to visual numerosity has previously been shown to predict human mathematical performance. However, it is not clear whether it is discrimination of numerosity per se that is predictive of mathematical ability, or whether the association is driven by more general task demands. To test this notion we had over 300 participants (ranging in age from 6 to 73 years) perform a symbolic mathematics test and 4 different visuospatial matching tasks. The visual tasks involved matching 2 clusters of Gabor elements for their numerosity, density, size or orientation by a method of adjustment. Partial correlation and regression analyses showed that sensitivity to visual numerosity, sensitivity to visual orientation and mathematical education level predict a significant proportion of shared as well as unique variance in mathematics scores. These findings suggest that sensitivity to visual numerosity is not a unique visual psychophysical predictor of mathematical ability. Instead, the data are consistent with mathematics representing a multi-factorial process that shares resources with a number of visuospatial tasks.

Psychophysical chromatic mechanisms in macaque monkey.

Chromatic mechanisms have been studied extensively with psychophysical techniques in humans, but the number and nature of the mechanisms are still controversial. Appeals to monkey neurophysiology are often used to sort out the competing claims and to test hypotheses arising from the experiments in humans, but psychophysical chromatic mechanisms have never been assessed in monkeys. Here we address this issue by measuring color-detection thresholds in monkeys before and after chromatic adaptation, employing a standard approach used to determine chromatic mechanisms in humans. We conducted separate experiments using adaptation configured as either flickering full-field colors or heterochromatic gratings. Full-field colors would favor activity within the visual system at or before the arrival of retinal signals to V1, before the spatial transformation of color signals by the cortex. Conversely, gratings would favor activity within the cortex where neurons are often sensitive to spatial chromatic structure. Detection thresholds were selectively elevated for the colors of full-field adaptation when it modulated along either of the two cardinal chromatic axes that define cone-opponent color space [L vs M or S vs (L + M)], providing evidence for two privileged cardinal chromatic mechanisms implemented early in the visual-processing hierarchy. Adaptation with gratings produced elevated thresholds for colors of the adaptation regardless of its chromatic makeup, suggesting a cortical representation comprised of multiple higher-order mechanisms each selective for a different direction in color space. The results suggest that color is represented by two cardinal channels early in the processing hierarchy and many chromatic channels in brain regions closer to perceptual readout.