Step 5: Technique of retrograde urohydropropulsion (Figures 1 and 2).
To remove uroliths from male dogs by retrograde urohydropropulsion, we recommend this procedure :
1. Inject a liberal quantity of a mixture of sterilized saline solution and aqueous lubricant through a flexible catheter into
the urethral lumen adjacent to the uroliths.
2. Next, an assistant familiar with this procedure should gently insert a lubricated gloved index finger into the rectum. Firmly
occlude the lumen of the pelvic urethra by applying digital pressure against the ischium through the ventral wall of the rectum.
3. A flexible catheter with an attached 20-ml to 35-ml syringe filled with sterilized saline should then be inserted into the
lumen of the penile urethra via the external urethral orifice and advanced to the site of the urethroliths.
The penile urethra should be compressed around the shaft of the catheter by firm digital pressure. As a result of these steps,
a portion of the urethra from the external urethral orifice to the bony pelvis becomes a closed system. Failure to properly
occlude the pelvic and/or the distal-most portion urethral lumen will result in impaired ability to flush the urethroliths
into the urinary bladder (Table 1).
4. Saline should be injected into the urethra until a marked increase in the diameter of the pelvic urethra is perceived by
the assistant. Confirmation that the urethra has been markedly distended is important because distention of the urethra to
its maximum capacity must be achieved before a sufficient degree of pressure can be created within the urethral lumen to advance
Failure to create sufficient pressure in the urethral lumen often results in inability to flush the urethroliths back the
urinary bladder (Table 1). The likelihood of rupture of the urethral lumen as a result of intraluminal pressure generated
by this technique is remote because the path of least resistance for fluid is through the urethra into the bladder lumen and/or
out the external urethral orifice.
However, caution must be used not to rupture the urinary bladder by over-distending the lumen with the flushing solution.
Therefore, the size of the bladder should be monitored at appropriate intervals by abdominal palpation. If and when it becomes
full, decompressive cystocentesis should be repeated.
5. At this point, the lumen of all portions of the isolated urethra, except that located in the ventral groove of the os penis,
will be markedly dilated (Figure 1, p. 6S ). Dilation of the lumen of the segment of the urethra located in the ventral groove
of the os penis is limited to that caused by stretching of the ventral portion of the urethral wall.
6. Next, digital pressure applied to the pelvic urethra (but not the penile urethra) should be rapidly released. Pressure should
be maintained in the urethral lumen by continuing to inject saline by pushing the syringe barrel over the syringe plunger
after the assistant has released digital pressure applied through the rectal wall. This step requires coordination between
the two individuals performing the technique (Table 1). When properly coordinated, this step will propel the saline mixture
and the urethroliths toward (or into) the bladder lumen (Figure 2, p. 7S).
Often, especially in cases where the uroliths have recently passed into the urethra, the urethroliths are easily flushed into
the bladder lumen during the first attempt. However, in some situations, the uroliths do not move, or move only a short distance,
before the pressure in the urethral lumen has dissipated. If this occurs, it may be necessary to repeat the procedure several
times before all the uroliths reach the bladder lumen.
The position of the urolith(s) may be monitored either by means of: a) digital palpation of the perineal and pelvic urethra,
b) a catheter carefully advanced through the urethra, and/or c) by means of radiography. If it is necessary to repeat the
technique, accumulation of large amounts of saline and urine in the lumen of the bladder will necessitate repeating decompressive
Step 6: Minimize catheter-induced trauma to the urinary tract, and iatrogenic urinary-tract infection
Appropriate care must be used to minimize trauma and pain to various components of the urinary tract, and to minimize the
risk of iatrogenic urinary-tract infection. To minimize catheter-associated bacterial infection, catheters, lubricants, irrigating
solutions, specula and other instruments should be sterilized. However, because the distal portion of the urethra normally
contains a commensal population of bacteria, it is impossible to aseptically catheterize the patient.
The need for prophylactic antibacterial therapy after retrograde urohydropropulsion must be determined on the basis of the
status of the patient and retrospective evaluation of technique. If it is probable that the dog has ongoing UTI, or if restoration
of urethral patency is associated with substantial trauma to, and/ or contamination of, the lower genitourinary tract, appropriate
antimicrobial therapy should be initiated. Remember to obtain pretreatment urine samples for urinalysis and bacterial urine
If, following restoration of urethral patency, the decision to use an in-dwelling transurethral catheter is being considered,
the likelihood of inducing an iatrogenic bacterial infection must be considered.
Ascending migration of bacteria through the lumen of the catheter may be minimized by proper use of closed drainage systems
that prevent reflux of urine from the collection receptacle back into the urinary tract.
However, bacteria may gain access to the bladder lumen by migrating through the space between the outside surface of the in-dwelling
transurethral catheter and the surface of the urethral mucosa.
In this situation, the question is not whether a urinary-tract infection will occur, but rather when a urinary tract infection
Never forcefully advance a catheter through the lumen of the urethra. Trauma to the urethral wall is the usual consequence
of use of excessive force, and may result in acute inflammatory swelling followed by formation of irreversible strictures.
Over-insertion of excessive lengths of catheter also should be avoided to minimize trauma to the bladder and/or to prevent
the catheter from becoming knotted or entangled within the bladder and/or urethral lumens.
Step 7: Consider an appropriate technique to manage the urocystoliths
Once all of the stones are in the bladder, further treatment obviously should be considered.
Depending on the mineral composition of the urolith and a variety of other factors, some therapeutic options include medical
dissolution, lithotripsy or cystotomy.
Contact our Web site for additional details (
http://www.cvm.umn.edu/. Click on the icon for Departments and Centers and then on the icon for the Minnesota Urolith Center).
by Carl A. Osborne DVM, PhD, Dipl. ACVIM, a diplomate of the American College of Veterinary Internal Medicine, is professor of medicine in the Department of Small
Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota.