Compliments of Washington State University School of Veterinary Medicine
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.
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.
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.
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.
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.
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.
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.