Ruminant 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 there are often dozens of stones in the bladder and urethra. It is just a matter of hours before more come down the urethra and can become lodged. This procedure may allow you to schedule the surgery in daylight hours rather than at 2am.
  • 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
    • avoid alfalfa hay, oreo cookies, dog chow
    • encourage dilute urine by salting the food
  • soychlor or pasturechlor is the most effective dietary adjustment we have currently for herd level management
  • 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. This means it works better in individual animal management rather than herd management
    • it should also be given in a pulsatile fashion – it stops working if given continuously;  titrate the dose to a level that acidifies the urine (pH <6.5) in the affected animal, then treat three days on, four days off
    • if owners can check urine pH, this may be a useful feed additive for phosphatic urolithiasis; check pH 5-7 hours after giving the acidifier
  • oral D, L-Methionine at a dosage of 200 mg/kg can also decrease pH
  • measures to acidify urine may actually increase the risk of calcium carbonate stones – don’t overdo it!
• 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.

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.

Penile amputation is used in feedlot steers. In these animals, the goal is to get the animal out of the uremic stage so they can be shipped for slaugther. An incision is made in the perineal region above the sigmoid flexure and the penis identified. This location is almost always proximal to any obstructive stones. Traction is placed on the penis to exteriorize more of it (basically pulling the distal end up and potentially out). Once enough penis is freed up, it is transected and the penile artery ligated. At the end of surgery, enough of a penile stump should be projected out the back of the animal so that the steer can urinate. This will stricture so the steer should be sent to salvage within about 30 days.

This surgery is easier to perform than a penile urethrotomy; both do accomplish the same goal and both stricture readily.

Modified tube cystotomy is possible using percutaneous catheter placement or placement through a small incision in the flank. These tend to be less effective because of the location and size of the tube but may be options in select cases. Complications are higher due to the limited visualization, surgical access and urine control.