Urolithiasis remains an infrequently diagnosed condition in horses, constituting 0.11% of equine admissions to university veterinary teaching hospitals in the United States over a 19-year period.1 Of these reported cases of urolithiasis, 59.7% involved cystic calculi. Cystic calculi are more common in geldings and stallions than in female horses,1–3 and this difference is believed to be attributable to the longer, narrower urethra in males versus females.4
The most common clinical sign associated with cystic calculi in horses is hematuria, which is often exacerbated by exercise.3 Additional clinical signs include tenesmus, incontinence, dysuria, stranguria, pollakiuria, urine scald, and, less commonly, weight loss.1–3,5,6
Uroliths in horses are primarily composed of calcium carbonate crystals, with a smaller proportion of calculi containing magnesium ammonium phosphate, calcium oxalate, and calcium sulfate in addition to calcium carbonate.1,3,4,6,7 Uroliths can also be classified as either type 1 or type 2, with type 1 accounting for approximately 90% of uroliths in horses.3 Type 1 calculi are comprised of calcium carbonate, typically have a spiculated surface with a yellow to yellow-green color, and are relatively easily fragmented. In contrast, type 2 uroliths contain phosphate in addition to calcium carbonate, have a relatively smooth surface with a grayish-white color, and are more resistant to fragmentation.
A diagnosis of cystic calculi is typically made on the basis of clinical signs and results of palpation per rectum, transrectal ultrasonography, and transurethral endoscopic examination of the urinary bladder.1–6,8,9 Transurethral digital palpation and direct visualization of a cystic calculus in a mare have also been reported.9
Several methods have been described for the removal of cystic calculi from horses, including laparocystotomy,1–3,5,10 laparoscopic techniques,11–13 transurethral removal,1,4,14 pararectal cystotomy,5,15 and removal through a perineal urethrotomy (males only).1,5,6,8,9 Currently, laparocystotomy is considered the treatment of choice,1–3,5,6,10 given that it allows for complete removal of larger calculi, minimizes trauma to the urinary bladder and urethra, and avoids the difficulties often encountered during removal from standing horses.
Techniques reported to facilitate removal of cystic calculi from standing sedated horses, either by a transurethral approach or through a temporary perineal urethrotomy site, include manual crushing,1,2 fragmentation with a mallet and osteotome,5 pulsed-dye laser,16,17 holmium:yttrium-aluminum-garnet laser,9,18 electrohydraulic shockwave,4 or ballistic shockwave,19 followed by fragment removal. Because of the shorter length, larger diameter, and distensible nature of the urethra in mares, large calculi can be removed intact, in conjunction with urethral sphincterotomy when necessary.1,2,5,14
Intraoperative complications associated with removal of cystic calculi from standing horses include rectal tear,1 perforation of the urinary bladder or urethra,1,4 unsuccessful attempts to fragment calculi,16 and an inability to remove all fragments from the bladder.1,6,11 Reported postoperative complications include peritonitis, fever and urethritis,1 cystitis,1,4 retained fragments causing urethral obstruction,4 urethral stricture,2 and recurrence related to retained fragments serving as a nidus for future calculus formation.1,11 Up to 41% of cystic calculi reportedly recur following removal, regardless of the method used for removal, and 47% are reported to recur when retrieved through perineal urethrotomy.1
A recent case report8 described removal of small cystic calculi from 2 geldings through a perineal urethrotomy site, without fragmentation, with the aid of a laparoscopic retrieval device. The authors concluded that although the technique was successful for removal of smaller calculi from standing sedated horses, larger calculi that cannot be removed by this method should be treated by other previously described techniques. We hypothesized that a laparoscopic specimen retrieval pouch could be effectively used to contain and stabilize cystic calculi requiring fragmentation to facilitate removal from standing horses. We also hypothesized that the pouch would protect the urinary bladder and urethra from iatrogenic trauma during removal of intact calculi or following fragmentation of calculi that could not be removed intact.
Epidural catheterization kit with TheraCath catheter, Arrow International, Reading, Pa.
Stallion urinary catheter, Jorgensen Labs, Loveland, Colo.
Fujinon EVE 400 Series, Fujinon, Wayne, NJ.
Endo catch II specimen retrieval pouch, Covidien, New Haven, Conn.
Vet One OB lube, MWI Veterinary Supply, Boise, Idaho.
Duolith Vet, Storz Medical, Tägerwilen, Switzerland.
Sharp & Smith, Chicago, Ill.
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4. Rocken M, Furst A, Kummer M, et al. Endoscopic-assisted electrohydraulic shockwave lithotripsy in standing sedated horses. Vet Surg 2012; 41: 620–624.
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19. Koenig J, Hurtig M, Pearce S, et al. Ballistic shock wave lithotripsy in an 18-year-old Thoroughbred gelding. Can Vet J 1999; 40: 185–186.
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