Reading Urology : Ureteric Stent Part 1

In patients who have, or might have, an obstruction (blockage) of the kidney, an internal drainage tube called a ‘stent’ is commonly placed in the ureter, the tube between the kidney and the bladder. This is placed there in order to prevent or temporarily relieve the obstruction. Your urologist is planning to use such a stent for you.

This information is divided into two parts.
Part 1 explains about the urinary system, obstruction of the kidneys and treatment of this obstruction using ureteric stents.
Part 2 describes what to expect while the stent is in place and any possible side effects.

Part 1: The Urinary System and Ureteric Stents

The Urinary System and the Ureter

The kidneys produce urine. Normally there are two kidneys situated in the upper part of the abdomen, towards the back. Urine formed in the kidney is carried to the bladder by a fine muscular tube called a ureter. The urinary bladder acts as a reservoir for the urine and when it is full it is emptied via the urethra (water passage).

Diagram here

How does a kidney become obstructed?

Common causes of obstruction of the kidneys and ureter are:

a kidney stone or its fragment moving into the ureter, either spontaneously, or occasionally following such treatment as shock wave therapy (lithotripsy)
narrowing (stricture) of the ureter anywhere along its path. This can be due to various causes e.g. scarring of wall of the ureter, narrowing of the area where ureter leaves the kidney (pelvi-ureteric junction)
temporarily, following an operation or after an instrument has been inserted into the ureter and kidneys

Occasionally obstruction can occur because of diseases of the prostate or tumours of the urinary system. Your urologist will provide further details applicable to you.

What are the effects of obstruction?

Whenever there is an obstruction, pressure builds up behind the kidney. Due to high pressure, the function of the kidneys starts to suffer over a period of weeks. The obstruction can also cause stagnation of the urine, which can lead to infection and further damage to the kidneys. It is, therefore, important to relieve or prevent obstruction of the kidneys.

Temporary relief of the obstruction

It is not always possible to identify what has caused an obstruction and to treat this immediately. It is therefore essential to relieve the obstruction on a temporary basis before treatment is carried out. Also, following an operation on the ureter, it takes time for it to heal and a temporary measure to prevent obstruction becomes essential. This is commonly achieved by inserting a ureteric stent to make a channel for the urine to pass and allow the kidneys to drain.

What is a Ureteric Stent?

A ureteric stent is a specially designed hollow tube, made of a flexible plastic material that is placed in the ureter. The length of the stents used in adult patients varies between 24 to 30 cm. Although there are different types of stents, all of them serve the same purpose (see diagram below).

One type of a ureteric stent

Diagram to go here

How does a stent stay in place?

Stents are designed to stay in the urinary system by having both the ends coiled. The top end coils in the kidney and the lower end coils inside the bladder to prevent its displacement. The stents are flexible enough to withstand various body movements.

How is a ureteric stent put in place?

Usually a stent is placed under a general anaesthetic using a special telescope (cystoscope) which is passed through the urethra into the bladder. The stents are then placed in the ureter and kidney via the opening of the ureter in the bladder. The stent may be inserted as an additional part of an operation on the ureter and kidney (e.g. ureteroscopy).

Occasionally they are placed from the kidney down to the bladder using special x-ray techniques. The correct position of a stent is checked by taking a x-ray.

Stent placed inside the urinary system

Diagram here

How long will the stent stay in the body?

There is no hard and fast rule about this. A stent has to be kept in place as long as necessary, i.e. until the obstruction is relieved. This depends on the cause of obstruction and the nature of its treatment.

In the majority of patients, a stent is required for a short duration, from a few weeks to a few months. However, a stent can stay in for up to three months without the need to replace it. When the underlying problem is not a kidney stone, the stent can stay even longer. Your urologist will tell you how long he expects your stent to remain in place.

How is a stent removed?

This is a short procedure and consists of removal of the stent using a flexible cystoscope, usually under local anaesthesia. Sometimes a stent can be left with a thread attached to its lower end that stays outside the body through the urethra. This type of stent can be removed by just pulling the thread.

Is there an alternative option to the use of a stent?

There is no simple alternative option. In some patients, a tube draining the urine to the outside called a ‘nephrostomy tube’, may be placed in the kidney. However, this involves carrying a urine collection bag attached to your back, which requires proper care. If you need this treatment your urologist will explain in detail what is involved.

Go to Part 2 Living with a ureteric stent for further information

Authors: Mr. H. B. Joshi (Clinical Research Fellow in Urology), N. Newns (Staff Nurse), Mr. F. X. Keeley Jr. (Consultant Urologist), Mr. A. G. Timoney (Consultant Urologist) – Southmead Hospital, Westbury-on-Trym, Bristol BS10 5NB. See also http://www.bui.ac.uk