College of Veterinary Medicine

Small Animal DX & Therapeutic Techniques

Urinary Catheterization of the Dog

ur_catheters.jpg (18785 bytes) There are several types of urinary catheters available. The top catheter is a stainless steel catheter used only in female dogs. It is sometimes called a "bitch" catheter. The second catheter from the top of the screen is a Foley catheter.
Foley catheters have an inflatable bulb at the end that can be filled with air or fluid (~3-5 ml) to retain the tip of the catheter within the bladder. Foley catheters are too short to reach the bladder of male dogs. The third catheter is a semi-rigid plastic (polypropylene) urinary catheter. This catheter type can be used in either sex. The bottom catheter is a red rubber feeding tube that can be used as a urinary catheter in either sex dog. The smaller diameter red rubber catheters (<10 Fr)may not be long enough to reach the bladder of large male dogs.
ur_foley2.jpg (36694 bytes) Foley Catheter:

The syringe is attached to an adapter which is attached to a thin tube within the catheter. Fluid or air is injected into this tube which terminates in a thin walled balloon. The balloon capacity is printed on the white plastic adapter (a) (usually 3 to 5 ml). The balloon is inflated when the catheter is in the lumen of the bladder (b). The intent is to retain the catheter in the bladder. The balloon is deflated prior to catheter removal by aspirating back the fluid or air. The adaptor contains a valve which prevents loss of fluid or air.

Urinary catheters are sized using French (fr) units. The French number divided by 3 is the outer diameter of the catheter in milimeters.

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The rounded tip of the catheter reduces urethral trauma as the catheter is passed. Urine enters the lumen of the catheter through two "eye" holes.

ur_cut.jpg (25597 bytes) Polypropylene and rubber catheters can be gas sterilized. The autoclave packaging can be used to maintain sterility of the catheter while it is being passed into the urethra. A finger tab about 1 inch wide is cut or torn from the end of the package closest to the rounded tip of the catheter, ~2 inches from the end of the package.
ur_cut_tab.jpg (24565 bytes) The finger tab is cut free of the reminder of the package. The end of the package closest to the rounded end of the catheter is removed, taking care not to contaminate the exposed end of the catheter. The finger tab is used to guide the catheter into the urethra.
ur_ky.jpg (27920 bytes) The tip of the catheter should be lubricated with a water soluble lubricant to minimize urethral trauma. The individual packages of lubricant are prefered over multiple use tubes. The multiple use tubes may become contaminated and be a source of contamination of the urinary tract during catheterization.
ur_frompackage.jpg (27447 bytes) The penis is extruded from the prepuce and is cleansed with an antiseptic solution such as BetadineTM or NovalsanTM. The finger tab is used to hold the catheter as it is being introduced into the urethra.
ur_resistance.jpg (23999 bytes) The urethra is limited in distensibility by the os penis surrounding it's dorsal surface. The catheter tends toward taking a straight course at the ischial arch . The catheter can be palpated in the perineal region. You can gently push on the catheter through the skin in the perineal region to guide the catheter around the arch.
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A sterile hemostat can be used to feed the catheter out of the sterile package.

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Female dogs can be catheterized by digitally palpating the urethral orifice, then passing the catheter under your finger...


or a speculum can be used to visualize the urethral orifice. These are human nasal specula but work well as canine vaginal specula. The one on the bottom has blades approximately 3/4 of an inch long. The blades are too short to aid in visualization of the urethral orifice in most bitches. The blades of the top speculum are approximately 2 inches long.

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When using a vaginal speculum, the blades are initially directed vertically until the clitoral fossa is passed and then they are redirected horizontally. The handles of the speculum should be pointed towards the tail so they are not in the operator's way as they are passing the urethral catheter.

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This is an anal scope that works well to visualize the urethral orifice. The speculum (a) and rounded tip insertion guide (b) are lubricated and inserted into the vagina. The insertion guide is removed by pulling on the metal ring (c) attached to the guide. The light source (d) is turned on. The speculum is slowly retracted until the urethral orifice is visualized. The urinary catheter is passed into the bladder and then the speculum is removed. If the urethral orifice is not visualized, reinsert the insertion guide into the speculum before advancing the speculum into the vagina. Note the edge of the speculum is sharp.

ur_orifice.jpg (16738 bytes) This is what the view looks like through the scope. The arrow points to the urethral orifice. The other two lines in the vaginal mucosa are folds in the tissue. Some bitches have a prominant mound of raised tissue around the urethral orifice. Gently probe the urethral orifice with the urinary catheter to confirm that it is the urethral orifice and not a fold of tissue.
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An otoscope with a large (wide but short) cone works well as a vaginal speculum to visualize the urethral orifice in the bitch. This is a Foley catheter being placed throughthe otoscope. Unfortunately, the flare end of the Foley will not fit through the otoscope cone and you need to disconnect the cone (a) from the light source (b) and leave the cone with the catheter until the catheter is removed from the patient. The letter (c) points to a magnifying lens attached to the light source. Magnification makes it easier to see the urethral orifice.

ur_foley_sty.jpg (17992 bytes) A 3 1/2 French polypropylene catheter will fit through the lumen of the Foley catheter to increase its rigidity and make it easier to pass.
ur_foley_sty2.jpg (17391 bytes)

You can use a stainless steel catheter as a stylet for a Foley catheter. The steel catheter is fitted into the eye of the Foley and the two are passed together into the bladder. This technique can only be used with "larger" (~12 French or larger) Foley catheters as the steel catheter will not fit in the eyehole of smaller Foleys. Lubrication of the metal catheter before it is inserted into the eyehole makes both insertion and removal of the metal catheter easier. The Foley bulb is inflated and the metal catheter is removed. If you fail to inflate the bulb of the Foley catheter before pulling out the metal catheter, both catheters will be removed.

A rigid metal catheter should never be over-inserted into the bladder as it may penetrate through the apex of the bladder.

Gentle technique is always called for when passing urinary catheters but this is especially true when using rigid catheters.

Last Edited: Feb 02, 2009 2:01 PM   

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