Last month, in the first of two articles, retrograde urohydropropulsion was discussed as a technique for restoring urethral
patency in dogs, usually with less chance of iatrogenic trauma. This second article describes seven steps for performing retrograde
Step 1: Verification and localization of urethroliths
Perform appropriate diagnostic procedures to localize the sites of urethrolith(s). Evaluate their number, size, radiodensity
and surface characteristics. Since uroliths rarely form in the urethra but migrate from the bladder lumen into the urethra,
be sure to include the urinary bladder in the evaluation. Palpation of the posterior urethra (including palpation of the urethra
per rectum) followed by appropriate survey or contrast radio-graphy should be performed to establish the site(s) and cause(s)
of outflow obstruction.
Ultrasonography may be of value in evaluation of the urinary bladder. If the urethroliths become lodged in an unusual or unexpected
location in context of the caudal aspect of the os penis, use contrast urethrography to rule out mural and/or extramural urethral
lesions that are contributing to outflow obstruction. If the patient has signs of systemic illness, or if the history suggests
prolonged outflow obstruction, pretreatment urine and blood samples should be obtained to assess renal function, systemic
fluid, electrolyte and acid-base status.
Figure 1: Removal of urethrolith in a male dog by urohydropulsion. Dilation of the urethral lumen is achieved by injecting
fluid with considerable pressure. Digital pressure applied to the external urethral orifice and the pelvic urethra has created
a closed system.
Step 2: Decompressive cystocentesis
If obstruction to urine outflow already has resulted in over-distension of the bladder lumen, it should be decompressed by
cystocentesis. To prevent iatrogenic over-distension of the bladder, decompressive cystocentesis generally should be performed
prior to urohydropropulsion.
Figure 2: Sudden release of digital pressure at the pelvic urethra and subsequent movement of fluid propelling the urethrolith
toward the bladder lumen.
Some benefits of this are:
1) An uncontaminated representative urine sample suitable for analysis and culture is obtained.
2) Temporarily correcting the problem by decompressive cystocentesis provides a mechanism to ameliorate discomfort and adverse
effects associated with post-renal azotemia.
3) Decompression of an over-distended urinary bladder and proximal urethra may decrease resistance to retrograde hydropropulsion
of urethroliths back into the bladder lumen. Failure to decompress before the procedure can result in impaired ability to
flush urethroliths into the urinary bladder (Table 1, p. 8S).
If excessive pressure is created in the over-distended bladder lumen, it will rupture. The potential risks of performing decompressive
cystocentesis are that (a) it may result in extravasation of urine into the bladder wall and/or peritoneal cavity, and (b)
it may injure the bladder wall or surrounding structures.
Although these complications could be severe in patients with a devitalized bladder wall, in our experience this has been
a very uncommon exception rather than the rule, provided that the majority, but not all, of the urine is removed from the
bladder before initiating urohydopropulsion.
Intra-peritoneal escape of a small quantity of urine through the pathway created by a 22-gauge hypodermic needle usually is
of little consequence. The potential of trauma to the bladder and adjacent structures can be minimized by proper technique.