We are not advocating an "always or never" approach to decompressive cystocentesis. Clinical judgment is required regarding
its use in each patient. However, it is preferable to decompress the urinary bladder by cystocentesis (saving an aliquot for
appropriate diag-nostic tests) prior to performing retrograde urohydropulsion in patients likely to have adequate integrity
of the bladder wall, and in which immediate over-distension of the bladder lumen, which predisposes to loss of urine into
the bladder wall and peritoneal cavity, is prevented by serially performed decompressive cystocentesis.
Technique of decompressive cystocentesis : We recommend that a 22-gauge needle be attached to a flexible intravenous extension
set which in turn is attached to a large-capacity syringe. After the needle is inserted into the bladder lumen, one individual
should digitally immobilize the urinary bladder containing the tip of the 22-gauge needle, while another aspirates urine from
the bladder lumen through flexible intravenous tubing into a large-capacity syringe. Gentle agitation of the distended bladder
in an up-and-down motion prior to cystocentesis may disperse particulate matter or crystals throughout the urine, and thus
facilitate their aspiration into the collection system.
The bladder should be emptied as completely as is consistent with atraumatic technique. Attempts to completely evacuate all
urine from the bladder lumen are contra-indicated because this mistake predisposes the patient to iatrogenic trauma of the
bladder mucosa and underlying tissues with the sharp point of the needle. Depending on the size of the dog, we typically allow
about 15 to 20 ml of urine to remain in the bladder lumen.
In the event patency of the urethra is not established before the bladder fills with urine and fluid used to back-flush the
urethra, decompressive cysto-centesis should be repeated before over-distension of the bladder lumen recurs. On occasion,
we have used serial decompressive cystocentesis over a span of several days because of problems in restoring urethral patency.
Step 3: Lubrication of urethroliths
Failure to properly lubricate the urethroliths prior to retrograde urohydropulsion may result in inability to flush them
into the urinary bladder (Table 1).
A liberal quantity of a mixture of one part of sterilized physiologic saline solution (or a comparable parenteral isotonic
fluid such as lactated Ringer's solution) to one part of aqueous lubricant should be injected through a catheter into the
urethral lumen adjacent to the uroliths. This maneuver helps lubricate the surface of the urolith(s) and the urethral mucosa,
which is often inflamed and swollen.
There may be some risk associated with injecting aqueous lubricants into the urinary tract of patients known to have tears
in the wall of the urethra or urinary bladder. Aqueous lubricants have been implicated in the formation of periurethral granulomas
in humans and rabbits. However, to date we have not recognized this problem following use of this technique in hundreds of
dogs with obstructive urethroliths.
Step 4: Restraint and anesthesia
Some form of sedation or general anesthesia is required for most patients. Pharmacologic agents dependent on renal metabolism
or excretion for inactivation and elimination from the body should be avoided.
If a patient is an anesthetic risk because of a uremic crisis, topical application of lidocaine gel to the urethral mucosa
in combination with parenteral administration of a low dose of analgesic may provide adequate patient restraint.
General anesthesia should be used if uroliths cannot be removed from the urethra of non-anesthetized patients by urohydropropulsion.
Inadequate pharmacologic control of patient discomfort may result in failure to flush the urethroliths into the bladder lumen
Appropriate precautions should be used for patients in renal failure because their sensitivity to general anesthesia may be
In our experience, a combination of intramuscularly administered oxymorphone (0.1 to 0.2 mg/kg) followed by slow intravenous
administration of propofol (an ultra-short-acting anesthetic) with dose titration to effect has been an excellent choice.
Propofol is highly protein-bound; it is rapidly conjugated in the liver to inactive metabolites. However, neither sedation
nor anesthesia produced by propofol is associated with complete relief of pain. Therefore propofol should be combined with
oxymorphone. To avoid apnea, propofol should by be slowly administered by the intravenous route.
In addition, because propofol administration may be associated with depressant cardiovascular and respiratory effects (especially
arterial hypotension), appropriate steps to correct dehydration of the patient should be initiated prior to anesthesia. If
necessary, propofol anesthesia may be prolonged by frequent incremental intravenous injections, or by constant iv infusion
of low doses.
Once urethral patency has been restored, the effects of oxymorphone can be antagonized with nalbuphine HCl ( 0.03 to 0.1 mg/kg
IV) if continued analgesia is desired, or naloxone (0.002 to 0.02 mg/kg IV) if respiratory depression is of greater concern.
Inhalant anesthetics also may be considered to anesthetize the patient if the drugs are not dependent on the kidneys for
inactivation and excretion from the body