Chapter 117 Urethra Flashcards
How is the male urethra ‘divided’ anatomically speaking>
- Pelvic
- Pre-prostatic (basically absent in dogs)
- Prostatic
- Penile
Where do the ductus deferens enter the urethra?
Dorsal prostatic urethra, either side of dorsally located colliculus seminalis
What type of ‘penile’ tissue surrounds the urethra for the entirety of its length?
Corpus spongiosum
What are the histogical layers of urethra?
Muscularis
Submucosa
Mucosa
What type of epithelium lines the urethra?
Proximally: transitional epithelium, distally stratified squamous
What are the muscular layers of the male canine urethra?
How does this differ from females (and pre-prostatic urethra of male cats)?
2 layers in male dog:
- Inner longitunidal smooth
- Outer circular striated in dostal 2/3rds (urethralis m)
3 layers in the rest:
- Inner longitudinal
- Middle circular
- Outer logitudinal
i.e. female urethra is histologically speaking the same as pre-prostatic male urethra
What is the sympathetic, parasympathetic and somatic innervation to the urethra?
- Sympathetic = hypogastric n
- Parasympathetic = pelvic n
- Somatic = pudendal n.
What is the principal artery supplying the urethra?
Urethral artery (branch of prostatic/vaginal artery, branch of internal pudendal) and penile artery
Label the diagram
Label the diagram
What is the diameter in male femine pre-prostatic, prostatic and penile urethra?
Pre-prostatic 2mm
Prostatic 1.3mm
Penile urethra 0.7mm
What is width of female canine urethra?
5mm
Where is the exit of urethra in biches?
External urethral tubercle on ventral floor of vestibule
Histologically speaking, how does female dog urethra differ from male dog
Female:
- 3 layers of muscle (vs 2 in male dog)
- More collagen
- Less muscle
Same changes seen in neutered vs entire bitches (i.e. more collagen and less muscle in neutered bitches)
How do ECG abnormalities progress with worsening hyperkalaemia
- Tall, 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
- Eventually wide QRS complexes and ventricular arrhythmias
(not been found to closely correlate with those seen in the clinical scenario, likely due to the presence of concurrent biochemical abnormalities)
At what point should calcium gluconate be adminstered for hyperkalaemia?
How is it given?
How long does effect last?
If bradycardia, significant ECG changes or K > 8 mmol/L
1 ml/kg 10% calcium gluconate over 10-20 minutes. ECG on.
Lasts 30-60 minutes
How does calcium gluconate work in tx of hyperkalaemia
Increses threshold for cardiac myocyte depolarization i.e. solely cardioprotective
In additonal to calcium gluconate, what other meds can be given inmanagement of hyper-K
- Dextrose (reduces K by K-Glu co-transporter)
- Regular insulin (lasts 2-4 hours)
- Bicarb (only if severe acidaemia)
- IVFT, CSL
List 5 methods to increase success of retrohydropulsion of urethral stones
- GA
- Topical anesthetic or epidural
- Lubricant
- Various sized catheters
- Counter pressure on urethra PR to allow distension
List 3 methdos for temporary management of urethral obstruction if retrograde u cath failed
- Cystocentesis (drain fully to reduce risk of uroabdomen)
- Tube cystostomy
- Antegrade transcystic catheterisation
- (Urethrotomy…)
When is negative (air) cytography contraindicated and why?
If lower urinary tract trauma suspected as can –> fatal air embolism
Comment on the image
Retrograde positive-contrast cystourethrogram of a 4-year-old male cat with rupture of the intrapelvic urethra.
- The catheter is coiled back after passing through the urethral defect.
- Extravasated contrast medium is present at the intrapelvic urethral defect, in the retroperitoneal space, and surrounding the trigone of the bladder.
Whatare the TWO critical factors in urethral healing?
- Mucosal continuity
- Urine extravasation
In urethral ‘discontinuity’ how fast can mucsa regenerate IF there is mucosal continuity and urinary diversion?
7 days!
What degree of urethral narrowing –> clinical signs
60%
What should be performed after u cath placememtn with urethral disruption
Positive contrast radiography to ensure catherer is actually within urethra/bladder for entire length
What is recommended treatment in complete urthral disruption?
Primary repair or permanent diversion
How long following urethra repair shoudl urinary diversion be continued?
3-5d
3 reasons canine urethrotomy is usually performed pre-scrotally
- Usualy place for stones to lodge
- Superficial location of urethra
- Minimal surrounding cavernous tissue
How is cystoscopy performed in male dogs?
Descibe technique
Minimally invasive perineal urethrotomy
- Needle from perineum ito proximal penile urethra
- Guidewire inserted via needle
- Guide-wire gradualy increased in size until hole can accomodate 14-16 Fr catheter (to allow passage 2.7 mm cystoscope
Briefly describe procedure for prescrotal urethrotomy in male dog
- Appropriate positioning + draping (inc access for scrotal urethrostomy as salvage and cystotomy for stone removal)
- U cath to level of obstruction
- Midline pre-scrotal inscision
- (consider some occlusion of more proximal penis for haemostasis)
- Retract paied retractor penis muscles laterally
- Midline longitudinal inscision through corpus spongiosum
- Retrieve stones etc. Flush and pass cath all which ways
How did recovery differ for dogs undergoing prescrotal urethrotomy left open vs closed primrilty
If left open:
- Haemorrhage 5-7d (i.e. more haemorrhage if left open)
- Pass urine via urethrotomy for 10-14d (apply petroleum jelly around wound)
When closing canine prescrotal urethrotomy, what factor –> less post-op haemorrhage?
Closure with simple continuous suture (vs simple nterrupted)
Name a modification of classic canine prescrotal urethrotomy
What was outcome?
Urethrotomy through glans penis following retraction of prepuce. Left open
- Haemorrhage stopped after 6 hours.
- Complete urethral healing within a month.
What suture material lost tensile strenght rapidly when immersed in urine
Poliglecaperone 25 (Monocryl)
List 3 other potential sites for canine urethrostomy, aside from scrotal
- Prescrotal
- Perineal
- Pre-pubic
(guess transpelvic and sub pubic not reported in dogs…)
List 3 reasons scrotal urethrostomy (vs perineal) is preferred in dogs
- Superficial urethral location
- Wide urethra
- Less haemorhage
List 4 urethrostomy loctions in cats
- Perineal
- Transpelvic
- Subpubic
- Prepubic
What urethrostomy location sare available in bitches?
Subpubic
Prepubic
HOw much does PU stoma contract durng healing
By 1/3rd to 1/2 of original length.
Briefly outline scrotal urethrostomy procudure
Scrotal urethrostomy in a male dog.
A, An elliptical incision is made at the base of the scrotum, retaining enough skin to allow for a tension-free closure of the urethrostomy.
B, Castration is performed routinely if the animal is intact.
C, A urinary catheter is placed retrograde from the penile orifice to help identify the urethra. The retractor penis muscle is dissected off the urethra and retracted laterally.
D, A sharp incision is made on the ventral midline of the urethra using a scalpel blade; the incision is enlarged with scissors for approximately 2.5 to 4 cm (inset).
E, The urethral mucosa is sutured to the skin using a simple interrupted or continuous pattern. Suture includes the entire thickness of urethra and split-thickness skin.
What is most common complication afetr scrotal urethrostomy?
Haemoarrhage
Then intermittent UTI/urine scald/recurrent obstruction from stones in 10% each
In scrotal urethrostomy cases, what factor reduced post op haemorrhage and what was the difference?
Simple continuous mucocutaneous apposiiton
Reduced haemorrhage from 4.2d to 0.2d.
Breifly outline procedure for PU.
Perineal urethrostomy in a male cat.
A, The patient is placed in sternal recumbency with a purse-string suture in the anus. An incision is made encircling the scrotum and prepuce. Castration is performed routinely if the animal is intact. The penis is retracted from the incision to allow dissection of the subcutaneous tissues to the level of the pelvis.
B, The penis is freed of its attachments to the pelvis. The origin of the ischiocavernosus muscle is identified, severed, and elevated from the ischium.
C, The ligament of the penis located ventral to the penis is severed.
D, Dissection is continued laterally and dorsally to expose the retractor penis muscle, bulbourethral glands, and bulbocavernosus muscle.
E, The retractor penis muscle, or its remnant in castrated males, is removed from the dorsal aspect of the penile urethra.
F, The urethra is incised on the dorsal midline beginning distally and continuing to the level of the bulbourethral glands.
G, The urethral mucosa is sutured to the skin beginning at the most dorsal aspect of the urethral incision. The dorsal-most sutures (at the 10, 12, and 2 o’clock positions) are preplaced in an interrupted pattern to adequately spatulate the opening.
H, The urethra is sutured for a distance of 1 to 1.5 cm, in a simple interrupted or continuous pattern, alternating sides. If necessary, the skin dorsal to the urethrostomy is closed separately.
I, A mattress suture or ligature is placed distally around the cavernous tissue to control hemorrhage.
J, The remaining distal penis is amputated.
K, Sutures are placed through the corners of the termination of the urethrostomy, and the remaining skin wound ventral to the urethrostomy is closed routinely.
L, Completed perineal urethrostomy. A figure of eight suture pattern (inset) may be used for urethrostomy closure to position knots away from the incision but maintain accurate urethrocutaneous apposition.
What is the benefit of performing PU in dorsal recumbency?
- Access to bladder + cystotomy if necessary
- Able to convert to more proximal urethrostomy if necessary
What are the muscles that are sharply severed during PU?
Bilateral ischiocavernosus
Retractor penis
How can you check that urethra freed up enough during PU
Bulbourthral glands should remain at level of skin without retracting into pelvic canal
How is adequate PU size checked
Insertion of 5-8 Fr u cath or box of Halsted mosquito forceps
List post-op management of PU (4 points)
- BC for 3-4 weeks
- Newspaper litter
- Petroleum around stoma
- No stoma cleaning (ulness blood clot – obstruction)
What is complication rate after PU?
What are two most common complications?
What is long term PU complication rate and 2 most common complications?
13%
Stricture + urine extravasation
Long term 28%
UTI and FLUTD
Breifly desctibe TPU procedure
Transpelvic urethrostomy in a male cat.
A, The ventral aspect of the penis and the caudal pubic symphysis are exposed. The gracilis and external obturator muscles are elevated from the symphysis to expose the underlying ischium.
B, A catheter may be advanced antegrade into the proximal urethra.
C, Bone rongeurs are used to remove 12mm length x 10mm width of the caudal ischium to expose the urethra for urethrostomy.
Urethra opened 15 - 18mm cranial to bulbourethral glands
What muscles ave to be elevated during TPU?
What is size of pelvic ostectomy
Gracilis + extrenal obturator
Ostectomy: 12mm length x 10mm width
What are the 4 external muscles of the penis?
- Ischiourethralis
- Ischiocavernosis
- Bulbospongiosus
- Retractor penis
Briefly describe sub-pubic urethrostomy technique
Pubic osteotomy and subpubic urethrostomy in a male cat.
A, The pubis is osteotomized at three sites (15mm lateral to symphysis and 3cm caudal to pubic brim). Holes may be predrilled before osteotomy for potential subsequent stabilization, and muscle attachments should be left intact caudal to the osteotomy.
B, The bone is rotated along its muscular attachment to expose the underlying urethra.
C, The pubic flap is replaced and the adductor and gracilis muscles are reapposed. A 1-cm stab incision is made through the skin in the subpubic region. The urethra is tunneled through the subcutaneous tissue, exteriorized, and spatulated before urethrocutaneous apposition.
`Where are oesteotomy cuts made for feline subpubic urethrostomy
15mm lateral to symphysis
3cm caudal to pubic brim
What number of cats (/16) had incontinence after subpubic urethrostomy?
6/16
Largely refractory to medical management
How can urethral anastomosis be reinforced (3 points)
Omentum
Rectus abdominis pedicle flap
Internal obturator flap
What are two approach options for access to entire intrapelvic urethra?
Pelvic symphysiotomy
Bilateral pubic + ischial osteotomies
What approach has been performed?
Intrapelvic urethral transection in a cat. The cat’s head is toward the top of the photograph. A pelvic symphysiectomy was performed to expose the ends of the transected urethra. The proximal urethral end was identified by antegrade catheterization via the bladder and was sutured to the perineum as described for perineal urethrostomy. The pelvic defect was closed by apposition of adductor muscles on the midline. The cat was ambulating normally within 3 days.
In dogs undergoign urethral anastomisis, what improved rate of strictures?
Urinary diversion with indwelling u-cath
What is hypospadia?
What embryonically leads to hypospadia
What is epispadia? What condition is it seen with?
Developmental anomaly leading to incomplete formation of the penile urethra (–> ventral opening)
Anomaly that results from failure of fusion of the urogenital folds
Epispadia = failure of fusion of dorsal penile urethra
Seen with bladder exstrophy
What breed is predispsosed to hypospadias
Boston terrier
what is the clasification of hypospadias?
- Glandular
- Penile
- Scrotal
- Perineal
- Anal
What conditions have been associated with hypospadia?
Cryptorchidism
(Also underdevelopment of testes, scrotum, prepuce, penis)
What are tx options for hypospadia?
- Primary closure
- Urethrostomy proximal to hypospadia (because often insufficient mucosa for primary closure)
- (Concurrent penile shortening/amputation ofetn improves clinical signs)
- Invese tubed bipedicle flap also described for anal hypospadia to increase distance between anus and urethral opening
What embryonic abnormailty most commonly –> urethral fistula
Failure of fusion of urorectal fold –> urethrorectal fistula
What condiiton can be seen with urethrorectal fistula?
Antresia ani
What is main clinical signs of urethral duplication?
How is urethral duplication treated? 3 points
C/s urinary incontinence and UTI
- Open surgical removal
- Cyanoacrylate embolization
- Coil embolization
HOw long does it take for complete urethral obstruction to –> uraemia?
And death
Uraemia 2-3d
Death 3-6d
Where do urethroliths usually lodge in male dogs (2 places)
And in male cats?
Dogs: Ischial arch or immediately caudal to os penis
Cats: Distal 1/3rd
What % of bladder and urethral tumours are maligannt/
97%
What is most common urethral tumour in dogs?
And cats?
TCC in both
What criteria have to be met for en blco resection of bladder neck + proximal urethra for management of neoplasia?
Superficial tumours that dont extend deeper than superfivial muscle layer
nor >2cm along urethra
What are options for management of bladder neck TCC
- Excision of neck + proximal urethra (tumour must be limited to superficial muscle layer and <2cm urethra)
- Total cystectomy + creation of common ureter that is anastomosed to urethra (MST 6 months)
- Laser ablation
- Stereotactic radiosurgery
- Cystoscopic electrosurgical transurethral resection (fine for invasive prostatic tumours but not just urethral as high rate of perf in those cases)
- Stent (self-expanding metallic stent (SEMS) preferred)
- Urinary diversion i.e. cystostomy tube
What was MST of dogs with obstructive TCC treated with stent?
What –> improved MST?
78d MST
250d MST with NSAID pre-treatment + adjunctive chemo
What was most significant complication of urethral stent placement for TCC management
How did this differ in cats
Incontinence 26% (no difference male vs female)
More incontinence (50%) incontinence in cats but better MST (460d)
Comment of image
Retrograde positive-contrast urethrogram of a 6-month-old male dog with a congenital urethrocutaneous fistula. The catheter tip is placed at the level of the urethra-fistula junction. Contrast medium opacifies the urethra and the fistula, which exits in the perineum 1 cm ventral to the anus.
