The management options for ureteral obstruction are diverse, including retrograde ureteral stent insertion or antegrade nephrostomy placement, with or without eventual antegrade stent insertion. There is currently no consensus on the ideal treatment or treatment pathway for ureteral obstruction owing, in part, to the varied etiologies of obstruction and diversity of institutional practices. Additionally, different clinicians such as internists, urologists, oncologists and radiologists are often involved in the care of patients with ureteral obstruction and may have differing opinions concerning the best management strategy. The purpose of this manuscript was to review available literature that compares percutaneous nephrostomy placement vs ureteral stenting in the management of ureteral obstruction from both benign and malignant etiologies.
The electronmicroscopic examination of sections taken from the hamster's optic nerve 5 mm behind the globe indicated that the nerve contains 110,165 +/- 4,177 (p less than 0.05) fibres of which 96.4% are myelinated. The fibre diameter distribution is unimodal with a peak at 1.2 micrometer and axon diameters ranging from 0.20 micrometer to 3.93 micrometer. Fibres of all sizes are distributed uniformly throughout the cross section of the nerve. The thickness of the myelin sheath surrounding a given axon is highly (0.80) correlated with axonal diameter and the degree of myelination for a fibre of a given size is nearly constant throughout the nerve's cross section. In nerve sections taken just posterior to the globe most (64%) of the fibres counted are unmyelinated and the percentage of unmyelinated axons is highest near the peripheral boundary of the nerve. The process of myelination is essentially complete in sections taken 3.5 mm behind the eye. These differences in the myelination of the proximal and distal nerve most probably account for the discrepancy between the results reported here and those provided by a previous study (Tiao and Blakemore, '76) concerned with the structure of the optic nerve in this species.
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