Urethra Flashcards
In a study by Segal 2020 in JSAP, what was the rate of stricture following PU in cats? What was the probability of post-operative obstruction if the urethral orifice was <8Fr immediately following surgery?
There was a 20% rate of stricture.
Post-operative obstruction occurred in 44% of cases with a urethral orifice <8Fr immediately following surgery (compared to 6% with an orifice >8Fr). All cases of urethral orifice <6Fr eventually obstructed.
In a study by Healy 2024 in JSAP, was urethropexy, urethral resection and anastomosis, or a combined procedure associated with the lowest rate of urethral prolapse recurrence in dogs? What was the overall rate of recurrence?
Urethral resection and anastomosis (11%) and the combined technique (13%) were associated with a lower rate of recurrence than urethropexy alone (39%).
Overall recurrence rate was 27%.
In a study by Seneviratne 2021 in JFMS, what was the most common reasons for performing perineal urethrostomy and prepubic urethrosotomy in cats? What complications were associated with prepubic rather than perineal urethrostomy (2)? What was the combined long term mortality rate for cats undergoing PU, transpelvic or pre-pubic urethrostomy?
FIC was the most common reason for performing PU (56%), while urethral trauma was most common reason for pre-pubic (82%). All pre-pubic cats had urethral rupture on imaging, whereas the majority of PU cats had no lesion (40%).
Long term complications were more common amongst pre-pubic cats. Short term dermatitis and long term incontinence were significantly associated with pre-pubic urethrostomy.
Short and long term mortality were 6% and 13% respectively.
Quality of life for all procedures was good.
In a study by Dumartinet 2022 in JFMS, what were the two most commonly reported short term complications in cats undergoing transpelvic urethrostomy for obstructive lower urinary tract disease? What were the 3 most common long term complications?
Short term complications (18%): idiopathic lower urinary tract disease, stomal stenosis.
Long term complications (34%): ILUTD, stomal stenosis, urinary tract infection.
Mortality rate was 5%, but quality of life in surviving patients was considered good by 90% of owners.
In a study by Sampaio 2022 in JFMS, did intact or neutered cats have an earlier onset of urethral obstruction?
Intact cats (3 vs. 5 years). Timing of neuter did not affect likelihood of obstruction.
In a study by David 2023 in JFMS, what was the reduction in length of the feline urethra following PU, transpelvic, and sub-pubic urethrostomies? Did the urethral orifice diameter differ between groups?
24%, 36%, 56% reduction in urethral length for PU, TPU and SPU respectively.
The urethral orifice diameter did not differ between groups.
In a study by McKenna 2024 in JVIM, what was the MST for dogs undergoing either radiation and/or chemotherapy treatment for urothelial carcinoma? What was the most common reason for death?
MST 339 days.
Local progression was the most common cause of euthanasia (62%), generally due to urinary obstruction (77%).
Metastatic rate was 56%.
What is the difference in the pre-prostatic urethra in male dogs and cats?
Dogs do not have a preprostatic urethra.
What are the layers of the urethra?
The layers of the urethra are mucosa, submucosa and muscularis.
How does the muscularis layer of the urethra differ between gender and species?
Male dogs: smooth muscle fibers (continuous with the prostatic capsule) surround the urethra for the entire length. Striated muscle fibers surround the urethra in the distal two-thirds.
Male cats: three layers of smooth muscle that contribute to a long internal urethral sphincter. The striated muscle is relatively short and thick.
Female dogs: three smooth muscle layers, interdigitate with the striated muscles in the distal third of the urethra. Prominent sphincter of striated muscle at the external urethral orifice.
Female cats: significantly more smooth muscle and less striated urethral sphincter (may contribute to lower rates of incontinence in this species).
What is the diameter of the male feline urethra at the level of the bulbourethral glands and penile urethra?
Bulbourethral glands: 1.3mm
Penile urethra: 0.7mm
Does the urethra of female dogs contain more or less collagen than male dogs?
More collagen and less muscle.
What is the vascular supply to the urethra?
Branches of the internal pudendal vessels.
Label the following diagram.
Is hypothermia common in cats with urethral obstruction?
Yes - thought to be secondary to a reduction in the thermoregulatory set point in the hypothalamus secondary to uremia.
How long does death take to occur following urethral obstruction?
3-6 days (renal decompensation typically occurs within 24 hours).
What ECG abnormalities are seen with hyperkalemia?
Spiked T-waves to depressed R-waves, prolonged QRS and PR intervals and ST segment depression, smaller and wider P-waves with a prolonged QT interval, atrial standstill, and eventually wide QRS complexes and ventricular arrhythmias.
Why is lactated ringers appropriate for treatment of hyperkalemia despite containing potassium?
Alkalinizing effect may help to drive potassium intracellularly. More effective for correction of metabolic derangements than NaCl.
What are the MOA of calcium gluconate, dextrose and insulin, and bicarbonate in the treatment of hyperkalemia?
Calcium gluconate: cardioprotective, increasing the threshold for myocyte depolarization. Lasts for 30-60 minutes.
Dextrose and insulin: drives potassium intracellular by cotransportation.
Sodium bicarbonate: enables hydrogen ions to move extracellularly in exchange for potassium.
What is the most common site of urethral obstruction in the male dog?
Os penis.
How can the success of retrograde urohydropulsion be improved?
Coccygeal epidural.
What is the imaging modality of choice for assessment of urethral lesions?
Positive contrast retrograde urethrography. Voiding cystogram can be used to aid in complex cases. If the urethra cannot be catheterized normograde urethrocystogram can be performed.
Why are air contrast studies contraindicated for use in patients with suspected lower urinary tract trauma?
Can result in fatal air embolism.
Describe a treatment algorithm for urethral obstruction.
