18. male ruminant urogenital surgery

general relevant anatomy of male ruminant urogenital system

• narrow urethra

• retrograde catheterization difficult / impossible due to:

  • urethral diverticulum located just caudal to entrance to the bladder

  • sigmoid flexure

• vascular and neural supply on dorsal aspect of the penis

• urethral process (vermiform appendage) present in small ruminants

  • absent in cattle & camelids

what areas of the urethra are predisposed to obstruction?

• distal sigmoid flexure (cattle & small ruminants)

• urethral process (small ruminants)

predisposing factors to urinary obstruction — diet

• high-grain diet → struvite & apatite calculi

• legumes → calcium carbonate calculi

• western USA & Canda → silicate calculi

predisposing factors to urinary obstruction — water & pH

• restricted water intake — winter months, illness

• higher urine SG → more minerals and organic matrix to form calculi

• alkaline pH favors struvite & calcium carbonate calculi

how does castration timing affect predisposition to urinary obstruction?

castrating at an early age reduces testosterone-mediated urethral growth → narrower urethral diameter

clinical signs of early / partial obstruction

• different urination pattern

  • dribbling urine, dysuria, stranguria

• calculi, crystals, or blood clots around preputial orifice

• discomfort shown as tail flagging, vocalization

• pulsation of urethra

  • visible in perineal area

  • digital rectal examination

late clinical signs of obstruction

• lethargy

• loss of appetite

• change in contour of abdomen

  • ruptured bladder

• swelling around prepuce

  • ruptured urethra

  • tissue necrosis

• metabolic derangements

  • seizures

  • death

urethral obstruction — lab findings

• bloodwork

  • stress leukogram

  • azotemia

    • increased BUN — increased mortality

  • hyperkalemia

• urinalysis

  • hematuria

  • crystalluria

  • proteinuria

urethral obstruction — medical treatment

• only ~50% successful

• amputation of urethral process

• supportive care

  • analgesia

  • correct fluid/electrolyte imbalance

    • 0.9% NaCl IV fluids (stabilizes hyperkalemia / azotemia)

  • dissolution of remaining uroliths

    • acidify urine (ammonium chloride) — do not decrease pH <5

  • change diet

tube cystostomy technique

• approach bladder

  • paramedian under GA / sedation

  • left flank position (cannot open bladder & remove stones)

• performed to remove uroliths or place catheter only

• routine closure

tube cystostomy complications

• dislodgement of catheter

• occlusion of catheter

• uroliths still present

  • re-obstruction

• major disadvantage is cost

bladder marsupialization technique

• approach bladder through paramedian or midline incision

• marsupialize apex of bladder to ventral body wall through 2nd (separate) incision, creating stoma allowing free urine to drain

bladder marsupialization complications

• urine scald

• prolapse of bladder mucosa

• ascending UTIs

• stricture formation

perineal urethrostomy technique & complications

• create permanent urethral opening

  • salvage to slaughter

  • not in breeding animal

• technique

  • “high perineal urethrostomy” — near ischium

  • “low perineal urethrostomy” — near scrotum

  • "alternative “modified perineal urethrostomy” — small ruminants & camelids

• complications

  • obstruction and stricture of stoma

urethrotomy

• urolith in location easy to access / palpate

  • incise urethra and remove urolith

  • incision heals by second intention or primary closure

• can be performed in breeding animals, but guarded prognosis

• complication = stricture formation (can place temporary catheter while lumen heals)

urolithiasis prevention

• dietary changes

  • Ca/Phos ratio 2:1

  • no or reduced grains containing high phosphorus

  • feeding of roughage-based diets

• increase water intake & urine volume

• change urine pH to 5.5-6.5

• delay castration 6 mo — 1 yr

surgical castration technique

• expose testicles by removal or opening scrotum

• removal of testicles

  • slow traction until spontaneous rupture of cord (≤ 150-200 kg; used only in very small calves)

  • emasculator & sharp transection

  • ligation in large bulls

non-surgical castration — burdizzo emasculatome

• bloodless castration by crushing spermatic cord through scrotal skin

  • check for inguinal hernias to prevent crushing intestines

• testicles left in place & atrophy

• do not crush across median raphe scrotum (do not cross midline) → cut off blood supply to scrotum; ischemic necrosis

  • stagger crush sites

non-surgical castration — elastrator bands

• popular in small ruminants

• ischemic necrosis of scrotum & testicles

  • make sure only testicles are in scrotum → check for inguinal hernias!

penile fibropapilloma — surgery technique

• animal on tilt table or standing

• extend penis

• surgical prep & infiltrate with lidocaine

• identify urethra with 10F catheter

  • prevent accidental transection

• excise lesion with scalpel, laser, or cryotherapy

• suture defect or heal by second intention

  • closing prevents adhesions

• examine 4 wks post-op before returning to breeding (4 wks of mandatory sexual rest)