Based on current risk models computerized tomography urography for asymptomatic microscopic hematuria may be associated with a small but significant risk of secondary malignancy relative to the additional diagnostic benefit offered.
Nonobstructive urinary retention (NOUR) is a medical condition without an effective drug treatment, but few basic science studies have focused on this condition. In α-chloralose-anesthetized cats, the bladder was cannulated via the dome and infused with saline to induce voiding that could occur without urethral outlet obstruction. A nerve cuff electrode was implanted for tibial nerve stimulation (TNS). The threshold (T) intensity for TNS to induce toe twitch was determined initially. Repeated (6 times) application of 30-min TNS (5 Hz, 0.2 ms, 4–6T) significantly ( P < 0.05) increased bladder capacity to 180% of control and reduced the duration of the micturition contraction to 30% of control with a small decrease in contraction amplitude (80% of control), which resulted in urinary retention with a low-voiding efficiency of 30% and a large amount of residual volume equivalent to 130% of control bladder capacity. This NOUR condition persisted for >2 h after the end of repeated TNS. However, lower frequency TNS (1 Hz, 0.2 ms, 4T) applied during voiding partially reversed the NOUR by significantly ( P < 0.05) increasing voiding efficiency to 60% and reducing residual volume to 70% of control bladder capacity without changing bladder capacity. These results revealed that tibial nerve afferent input can activate either an excitatory or an inhibitory central nervous system mechanism depending on afferent firing frequencies (1 vs. 5 Hz). This study established the first NOUR animal model that will be useful for basic science research aimed at developing new treatments for NOUR.
This study examined the mechanisms underlying pudendal and tibial neuromodulation of bladder function at the single neuron level in the spinal cord. A microelectrode was inserted into the S2 spinal cord of anesthetized cats to record single neuron activity induced by bladder distention over a range of constant intravesical pressures (10-40 cmHO). Pudendal nerve stimulation (PNS) or tibial nerve stimulation (TNS) was applied at 5 Hz frequency and 0.2 ms pulse width and at multiples of the threshold (T) intensities for inducing anal or toe twitches. A total of 14 spinal neurons from 11 cats were investigated. Both PNS and TNS at 2 T intensity significantly (p < .05) reduced by 40-50% the frequency of firing induced by bladder distention at 20-40 cmHO in the same spinal neurons. This reduction was not changed by blocking opioid receptors with naloxone (1 mg/kg, i.v.). Activation of pudendal afferents by repeatedly stroking (3-5 times per second) the genital skin using a cotton swab also inhibited the neuron activity induced by bladder distention. Prolonged (30 min) TNS at 4 T intensity produced a short lasting (10-18 min) post-stimulation inhibition that reduced by 40-50% bladder-related neuron activity at different bladder pressures. These results indicate that PNS and TNS inhibition of reflex bladder activity may be mediated in part by convergence of inhibitory inputs onto the same population of bladder-related interneurons in laminae V-VII of the S2 spinal cord and that an opioid receptor mechanism is not involved in the inhibition.
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