Colonoscopy conversion after flexible sigmoidoscopy screening: results from the UK Bowel Scope Screening Programme.

AIM: In the UK Bowel Scope Screening Programme (BSSP), patients progress to colonoscopy based on high-risk features on flexible sigmoidoscopy (FS). We aim to assess the practice of colonoscopy conversion and predictors of detection of additional adenomas on colonoscopy. METHOD: The Bowel Cancer Screening database was interrogated and collated with endoscopic and histological findings from patients undergoing colonoscopy following FS between August 2013 and August 2016. Multivariate analysis was performed to identify predictors of new adenomas. RESULTS: FS was performed on 11 711 patients, with an adenoma detection rate (ADR) of 8.5% and conversion to colonoscopy in 421 (3.6%). The additional ADR at colonoscopy was 35.2%, with one additional malignant diagnosis (0.26%). The adenoma miss rate was 3.6%. On multivariate analysis, a polyp ≥ 10 mm was the only high-risk indication associated with additional ADR at colonoscopy (OR 3.68, 95% CI 1.51-3.65, P < 0.001), in addition to male gender (OR 2.36, 95% CI 1.46-3.83, P < 0.001). Predictors of detection of a new adenoma ≥ 10 mm included: villous adenoma (P = 0.002), polyp ≥ 10 mm (P = 0.007) and male gender (P = 0.039). The presence of any conversion criterion was associated with the detection of any proximal adenoma (P < 0.001) and adenoma ≥ 10 mm (P = 0.031). CONCLUSION: Male gender, polyps ≥ 10 mm and villous-preponderant histology at FS were predictors of adenomas < 10 mm and ≥ 10 mm at colonoscopy. Further data are required to assess the role for gender-based stratification of conversion criteria.

Activity patterns in a model for the subthalamopallidal network of the basal ganglia.

Based on recent experimental data, we have developed a conductance-based computational network model of the subthalamic nucleus and the external segment of the globus pallidus in the indirect pathway of the basal ganglia. Computer simulations and analysis of this model illuminate the roles of the coupling architecture of the network, and associated synaptic conductances, in modulating the activity patterns displayed by this network. Depending on the relationships of these coupling parameters, the network can support three general classes of sustained firing patterns: clustering, propagating waves, and repetitive spiking that may show little regularity or correlation. Each activity pattern can occur continuously or in discrete episodes. We characterize the mechanisms underlying these rhythms, as well as the influence of parameters on details such as spiking frequency and wave speed. These results suggest that the subthalamopallidal circuit is capable both of correlated rhythmic activity and of irregular autonomous patterns of activity that block rhythmicity. Increased striatal input to, and weakened intrapallidal inhibition within, the indirect pathway can switch the behavior of the circuit from irregular to rhythmic. This may be sufficient to explain the emergence of correlated oscillatory activity in the subthalamopallidal circuit after destruction of dopaminergic neurons in Parkinson's disease and in animal models of parkinsonism.