Effect of Ureteric Stents on Urine Flow
نویسندگان
چکیده
The urinary tract is a conduit, storage and modification system for urine excreted by ultrafiltration from the kidney’s parenchyma. It is a dynamic and flexible system, able to handle widely differing flows of fluid through it with comparative ease. The urine is conveyed from the kidney to the bladder via a long thin tube called the ureter. Urine produced is supersaturated, but in normal individuals, inhibitors of crystallisation keep it in a liquid state. Urine entering the bladder is stored at low pressure until voiding is achieved. Rhythmic coordinated contractions of the ureter (peristalsis) push urine down the ureter, and anatomical considerations stop urine returning from the bladder to the kidney. Unfortunately blockage of the system may occur. This may be from the inside, causes for which include stones, cancers and fibrous bands (strictures) or from the outside, for example overlying fibrosis, bowel tumours, and accidental damage during surgery. The result of this obstruction is increased back pressure on the kidney which, if left untreated, will eventually cause it to fail. A blocked system may get infected, and this can very quickly become life-threatening. Obstruction is treated, if possible, by removing the obstruction, or repairing around it, but if this is not possible, the obstruction must be relieved. This may be done by direct drainage of the kidney (a nephrostomy) or via the insertion of a plastic tube called a stent. For some obstructions stents have to be left in situ permanently, but over time they can crust up with crystalline deposits of salts in solution in the urine, a process known as encrustation. This can be painful, cause further blockage, and may necessitate an open operation to remove the crusted stents. Encrustation occurs mainly in areas of urine stasis, i.e. the renal pelvis and the bladder.
منابع مشابه
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تاریخ انتشار 2015