Bladder, Urethra and Ureters

Ruminant urolithiasis

Urolithiasis podcast

Urolithiasis is a common problem in goats and feedlot cattle. It is not uncommon in pigs, camelids and horses. The type, number and location of stones varies by species. Pigs and camelids can also develop urethral polyps which present in very similar manner to stones but are much harder to treat (since we can’t readily remove them). Camelids tend to die due to related metabolic complications.

Horses present for hematuria. All the other species present for partial or complete urinary obstruction. Stones will often lodge in the vermiform appendage of goats and in the sigmoid flexure of all ruminants (and generally in both). Animals may be seen straining to urinate or defecate. Feedlot steers may be found dead (often with calculi on the preputial hairs). A vocalizing buck or wether should be assumed blocked by a urolith until proven otherwise.

Diagnostics

Passing a urinary catheter is generally not possible in ruminants or camelids due to the urethral diverticulum. Just because you can’t pass a urinary catheter does not mean the animal has stones. The most effective diagnostic test is a rectal exam (digital rectal exam in small ruminants). In an obstructed animal, the urethra is often pulsing.

Imaging can be used to confirm or assess the number and location of stones. Most (but not all) stones are radio-opaque. Ultrasound can be used to identify full bladders, urine leakage and occasionally urethral stones. The stifle is often right on top of the sigmoid flexure on radiographs so look carefully in that area.

. Caprine urolithiasis

Treatment

  • Enable urination (amputation of the vermiform appendage, tube cystotomy or other procedure) or relieve the bladder via cystocentesis
    • amputation of the vermiform appendage can help temporarily. The offending stone is removed but more come down the urethra later.
    • perineal urethrostomy is not a great choice in ruminants due to their propensity to stricture; it works fine in feedlot steers as their lifespan is limited
    • penile amputation is performed in feedlot steers (instead of perineal urethrostomy) as it is easier
    • most pet goats will do best with a tube cystotomy
  • Remove, dissolve and/or encourage passage of the stones
    • once the pressure to urinate is relieved (tube placed into bladder), the stones may pass on their own as the urethral relaxes
    • retrograde or anterograde (at surgery) flushing of the urethra tends to cause urethral rupture
  • Minimize the risk of recurrence
    • once a stone former, always a stone former
    • dietary adjustments are needed
    • soychlor or pasturechlor is the most effective dietary adjustment we have currently
    • many people incorrectly  believe ammonium chloride in the feed is effective
      • it works but goats don’t like it. For effective use, it needs to be given orally as a medication.
      • it should also be given in a pulsatile fashion – it stops working if given continuously
  • Manage any related complications (uremia, urinary tract infections, ruptured bladder, ruptured urethra)
  • Analgesics are needed, especially for goats
    • consider phenazopyridine (relieves bladder irritation), narcotics and NSAIDs
    • goats are pretty sensitive to pain and will tend to be in rough shape for a day or two post-operatively
  • Remove the tube once the goat can urinate on his own through the penis
    • this happens when the stone is passed, even with the tube still in place
    • antibiotic coverage is maintained while the tube is in place due to the risk of ascending infection
    • generally we leave the tube in for at least 8 days to create an adhesion to the body wall (this number is pulled out of thin air as far as I can tell)

Uremic animals are not edible. All uremia needs to resolve before an animal is shipped for meat. This can take several weeks.

 Tube cystotomy in a goat

Other options

Bladder marsupialization was developed to manage recurrent urolithiasis in goats. The bladder is tacked to the body wall and cystostomy performed, similar to a rumenostomy. However, many goats die of ascending pyelonephritis within two years so it is not an ideal fix. Additionally, goats dribble urine constantly and urine scald can be severe.  Bladder prolapse can occur.
Laser lithotripsy has been used to remove stubborn stones. The procedure requires specialized equipment and experienced operators. Postoperative swelling can also cause urinary obstruction.

Key Takeaways

  • If you have an animal with renal compromise, be very cautious with NSAIDs, steroids, tetracyclines and aminoglycosides. Penicillins are generally pretty safe. Consider drugs excreted by liver if no other restrictions apply (eg fluorquinolones).
  • Goats get stones because of diet issues. Urethral pulsation = obstruction. Tube cystotomies rule. Do not flush the urethra – goat urethras easily rupture.
  • Feedlot steers get stones due to diet issues. Penile amputation is recommended and the site will still stricture. Slaughter when no longer uremic. Uremic animals are not edible.
  • Camelids die
  • Pigs can have stones (removable) or polyps (not removable)
  • DCAD (cation-anion) diets are most effective. Do not give soychlor to the breeding does as it also pulls calcium from the goat and leads to jelly babies (no calcium).
    If clients use ammonium chloride (most goats won’t eat enough to help), they need to stop it intermittently or it stops working

Primary Resources

urolithiasis anes and tube cystotomy_ Sheep and Goat Medicine- works through all the diagnostics and options for treatment in more detail

Prevention of urolithiasis in livestock– CSU Van Metre- great practical hints for preventing stone formation

Secondary Resources

General anesthesia for patients with liver or renal disease,  DVM 360 2011 – SA perspective but nice review of what drugs are good or bad when your patient has other issues

1990 antibiotic associated complications with renal disease 1990 Reviews of Infectious Diseases- also for your files. hard to find this info.

Obstructive urolithiasis in ruminants – a review – 2013 VetWorld – starts at square 1 and covers physiology, lab changes etc

urolithiasis in small ruminants, ACVS – succinct general overview describing options; doesn’t give relative pros/cons

Urolithiasis in small ruminants, AASRP- more details than you ever wanted to know; good reference for future as he goes through more complex situations; please don’t do the hydropulsion though.

Surgery of obstructive urolithiasis in ruminants, VCNA 2008 -good overview with nice references; good for your files

Summer 2005 newsletter case of the month (page 3-4)- I use this for soychlor dosing; for your files. Also totally agree with filling the foley balloon with saline vs air. They last longer

Effects of castration on penile and urethral development in Awassi lambs, 2007 Bulgarian J of Vet Med -finally some EBM on this topic

penile amputation -for those of you struggling to visualize or just wanting more: youtube video

 

 

 

License

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Large Animal Surgery - Supplemental Notes by Erin Malone, DVM, PhD; Elaine Norton, DVM PhD; Erica Dobbs, DVM; and Ashley Ezzo, DVM is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.