Obstructive urolithiasis is a recognized problem of small ruminants (goats and sheep) and pigs.1–4 Common surgical methods for managing the condition include percutaneous tube cystotomy5,6 and surgical tube cystostomy.6,7 Although tube cystostomy has been recommended as the most satisfactory surgical method for this purpose in small ruminants,7,8 many factors can affect the choice of surgical method, including urolith type6 and clinician preference. Whereas struvite and apatite are the most common type of urolith in ruminants fed grain-based diets,9 the type most commonly identified in small ruminants at the University of California-Davis Veterinary Medical Teaching Hospital is calcium carbonate.10 Chemical dissolution with Walpole solution (sodium acetate, glacial acetic acid, and distilled water; pH 4.5) administered percutaneously into the urinary bladder can be successful for treating small ruminants with struvite uroliths11; however, chemical dissolution of calcium carbonate uroliths is uniformly unsuccessful because of their chemical structure and larger diameter.12 Therefore, most small ruminants admitted to the teaching hospital for obstructive urolithiasis require surgical intervention as part of patient management.
In a study4 of urinary calculi from potbellied pigs in California, Georgia, North Carolina, Ohio, and Texas, the most common urolith type identified was amorphous magnesium calcium phosphate.4 In the authors’ experience, this type of urolith is resistant to dissolution with Walpole solution or buffered citric acid. Consequently, most potbellied pigs evaluated for obstructive urolithiasis at our teaching hospital also require surgical intervention for obstructive urolithiasis.
Obstructive urolithiasis is considered a medical emergency, surgical emergency, or both. Small ruminants and potbellied pigs with obstructive urolithiasis consistently have secondary acid-base and electrolyte abnormalities such as azotemia, hyperkalemia, hypophosphatemia, and hypochloremic metabolic alkalosis13 that can increase the risk of anesthetic complications and possibly reduce the chance for a successful surgical outcome. One method that can allow for bladder emptying during acid-base and electrolyte correction prior to surgery is placement of a PTC. The objective of the study reported here was to evaluate the use of a commercially available PTC for urinary bladder drainage prior to surgical management or during medical management of goats, sheep, and potbellied pigs with obstructive urolithiasis by determining complications associated with PTC placement and duration of PTC placement prior to removal.
Materials and Methods
Case selection
A convenient, nonprobability sampling method was used to select animals for inclusion in the study. Computerized medical records of goats, sheep, and potbellied pigs with obstructive urolithiasis evaluated at the University of California-Davis Veterinary Medical Teaching Hospital from January 1, 2000, through December 31, 2014, were reviewed to identify animals in which a PTC had been placed into the urinary bladder. A diagnosis of obstructive urolithiasis was made by consideration of results of physical examination, serum biochemical analysis, and radiographic and ultrasonographic examination of the renal system. Patients with evidence of uroperitoneum as detected via ultrasonography and peritoneal fluid analysis were excluded.
Medical records review
Information obtained from the medical records included signalment (sex, age, breed, and use). On the basis of signalment, goats were categorized by breed type and use as dairy-meat (Nubian, Alpine, Boer), dwarf African (Pygmy and Nigerian Dwarf), and other (Tennessee fainting) breeds. All sheep breeds were categorized as meat type with regard to use, whereas all potbellied pigs were considered companion animals. Only the record of the initial visit for patients with obstructive urolithiasis in which a PTC was placed was reviewed. For all animals, information regarding any procedures (surgery, resolution of obstructive urolithiasis, or euthanasia) performed following PTC placement was recorded. Complications associated with and duration of PTC placement prior to removal were also noted.
Procedure for PTC placement
All animals had undergone a similar procedure. In preparation for the procedure, each was heavily sedated with benzodiazepine (diazepam or midazolam) or sedated with benzodiazepine and anesthetized with isoflurane delivered via face mask. The right mid to ventral caudal portion of the abdomen was clipped of hair and prepared aseptically. Then, a PTCa designed for human use14 was inserted into the urinary bladder in accordance with the manufacturer's recommendations. Briefly, the urinary bladder was identified ultrasonographically in the right caudal ventral portion of the abdomen. The entry point for the catheter on the skin was most commonly a caudal ventral position at a location where the distended urinary bladder and skin were in proximity. The skin at the entry point was infiltrated with 20 mg of 2% lidocaine solution to achieve local anesthesia.
A 3-mm stab skin incision was made with a No. 15 scalpel blade to aid in placement of the PTC. The PTC was then advanced slowly through the skin incision into the urinary bladder with ultrasonographic guidance. Once urine flow through the PTC was detected, the catheter stylet was removed while the rest of the PTC was simultaneously advanced into the urinary bladder. The PTC used creates a memory curve once placed. Placement was considered successful if urine flowed out of the catheter. The PTC was secured to the skin by use of nonabsorbable or absorbable suture material. Each animal was then allowed to recover from sedation or anesthesia. Medical management of patients after PTC placement included administration of analgesics, antimicrobials, and relevant crystalloid fluid to address existing serum analyte abnormalities.
Statistical analysis
Normality of data distribution was evaluated with the Shapiro-Wilk test. Because distributions were nonnormal, data are reported as median (range).
Results
Forty-three goats, 10 sheep, and 16 potbellied pigs met the selection criteria and were included in the study. All animals were male. Forty-two goats were castrated and 1 was sexually intact, whereas 5 sheep were castrated and 5 were sexually intact. All potbellied pigs were castrated. Twenty-six goats were of dairy-meat breeds, and breeds for the others included dwarf African (n = 16) and Tennessee fainting (1). Sheep breeds included Suffolk (n = 6), Hampshire down (2), American merino (1), and Barbados (1).
Median (range) age at evaluation for obstructive urolithiasis was 2 (0.33 to 12) years for goats, 3 (0.25 to 10) years for sheep, and 4 (3 to 12) years for potbellied pigs. Median (range) duration of PTC placement in the urinary bladder prior to removal was 2 (1 to 4) days for goats, 1 (1 to 4) day for sheep, and 1 (1 to 3) day for potbellied pigs. Urolithiasis resolved in 10 goats, 1 sheep, and 1 potbellied pig following PTC placement. Complications associated with PTC placement, in decreasing order of frequency, included blockage of the catheter by urine sediment, migration of the catheter out of the bladder, and full-thickness perforation of the cecum (Table 1). Procedures performed after PTC placement included IV crystalloid fluid administration in combination with surgery (amputation of the urethral process, tube cystostomy, perineal urethrostomy, or urinary bladder marsupialization), medical management (acepromazine maleate administration with or without infusion of buffered citric acidb into the urinary bladder with resolution of the obstructive urolithiasis), or euthanasia while the PTC was still in place (when medical management was unsuccessful).
Number of goats (n = 43), sheep (10), and potbellied pigs (16) with obstructive urolithiasis that had complications or underwent other procedures following PTC placement into the urinary bladder.
| Complication after placement | Procedure after placement | |||||
|---|---|---|---|---|---|---|
| Species | Blockage of PTC | Migration of PTC | Perforation of cecum | Surgery | Medical* | Euthanasia† |
| Goat | 7 | 3 | 2 | 24 | 10 | 9 |
| Sheep | 1 | 0 | 0 | 7 | 1 | 2 |
| Potbellied pig | 1 | 0 | 0 | 14 | 1 | 1 |
Medical management included amputation of the urethral process or acepromazine administration with or without infusion of buffered citric acid into the urinary bladder with resolution of the urolithiasis.
Patients were euthanized while the PTC was still in place when subsequent medical management was unsuccessful.
Buffered citric acid had been infused into the urinary bladder when struvite urolithiasis was suspected or identified. Acepromazine (0.02 to 0.06 mg/kg [0.009 to 0.027 mg/lb]) had been administered to provide relaxation of the retractor penis muscle and reduce urethral spasms associated with obstructive urolithiasis in 9 goats and 2 sheep.
Discussion
The main finding of the study reported here was that use of a PTC was effective for establishing drainage of the urinary bladder prior to surgical intervention or during medical management of variously sized goats and sheep and potbellied pigs with obstructive urolithiasis. The proportion of patients with complications as a result of the procedure was low. For patients for which surgical intervention was not performed, PTC placement also allowed infusion of agents such as buffered citric into the urinary bladder to achieve dissolution of struvite uroliths. Median duration of PTC placement prior to removal was at least 1 day for all 3 species, and this period was anticipated to be sufficient for stabilizing patients prior to surgical intervention or during medical management. The median duration was influenced by whether surgical or nonsurgical procedures were performed after PTC placement and therefore should be interpreted with caution. It should also be considered that obstructive urolithiasis is a medical or surgical emergency, and both medical and surgical management procedures can be expensive. Consequently, placement of a PTC can also provide additional time for clients to gather financial resources while their animal is being stabilized.
The most common complication associated with PTC placement in the present study was catheter blockage by urine sediment. This complication was not unexpected because obstructive urolithiasis is associated with hemorrhagic cystitis, resulting in urine sediment that consists of blood clots, uroliths, and protein. Additionally, the diameter of the catheter was narrow (similar to that of a 16-gauge IV catheter), so it was likely to become blocked. The types of complication associated with PTC placement should not be directly compared among the 3 species included in the study because of the small numbers of sheep (10) and potbellied pigs (16), compared with the larger number of goats (43). Indeed, the higher proportion of complications in goats may have purely reflected the overrepresentation of goats in the study. However, migration of the PTC and full-thickness perforation of the cecum occurred only in goats. Although the reasons for PTC migration were difficult to ascertain, the authors’ experience with PTC placement suggested they could have included repeated flushing to relieve blockage, repeated infusion of buffered citric acid, kinking of the catheter, attempts by the patients to remove the catheter, or interference by the hind limbs.
Perforation of the cecum (2 goats) was an unusual complication considering that review of the records revealed that the first attempt at catheter placement had been successful (as it had been for all other included animals). Perforation of the cecum can predispose animals to peritonitis. Therefore, we recommend evaluating patients for evidence of peritonitis secondary to perforation of the cecum at the time of surgical intervention or monitoring patients that are medically managed for signs of peritonitis. For humans with obstructive urolithiasis in whom a similar catheter was placed in another study,14 complications associated with catheter placement included kinking of the catheter, accidental removal of the catheter by the patient, and secondary hemorrhagic cystitis.
Procedures performed following PTC placement varied among species in the present study, and surgery was the most common type. This was most likely attributable to calcium carbonate being historically the most predominant type of urolith identified in goats, sheep, and potbellied pigs with obstructive urolithiasis admitted to our teaching hospital. Calcium carbonate is resistant to dissolution with citric acid12; therefore, surgery is considered the most effective management option. The decision to perform surgery or continue with medical management was made in part by consideration of the type of urolith involved as well as availability of client financial resources. A considerable proportion of patients (goats, 9/43; sheep, 2/10; and potbellied pigs, 1/16) were euthanized following unsuccessful medical management while the PTC was still in place. It is important for owners of small ruminants or potbellied pigs with urolithiasis to be aware that PTC placement followed by medical management may be unsuccessful, depending on the type of urolith. This is because less than one-quarter of animals in the present study had resolution of the obstructive urolithiasis by medical management alone (Table 1). Greater proportions of potbellied pigs and sheep than goats underwent surgery following PTC placement; however, this finding was most likely attributable to the purpose of the animals in that the potbellied pigs were companion animals whereas the goats were companion or production animals. Furthermore, one-half (5) of the sheep in the present study were sexually intact, indicating that they had some breeding value, likely prompting owners to consider breeding value when considering whether to pursue medical or surgical management.
Additional limitations of the present study included the presence of selection bias, given that only patients from 1 geographic area were considered. The specific type of urolith (calcium carbonate) most commonly identified in the teaching hospital's livestock population also influenced the types of procedures performed following PTC placement. Nevertheless, the data showed that use of a PTC was an acceptable method for draining the urinary bladder of goats, sheep, and potbellied pigs with obstructive urolithiasis prior to surgical or during medical management, while acid-base and electrolyte imbalances were corrected.
ABBREVIATIONS
| PTC | Percutaneous transabdominal catheter |
Footnotes
Bonnano, Becton, Dickinson & Co, Franklin Lakes, NJ.
Renacidin, Guardian Laboratories, Hauppauge, NY.
References
1. Van Metre DCHouse JKSmith BP, et al. Obstructive urolithiasis in ruminants: medical treatment and urethral surgery. Compend Contin Educ Pract Vet 1996;18:317–327.
2. Van Metre DCFecteau GHouse JK, et al. Obstructive urolithiasis in ruminants: surgical management and prevention. Compend Contin Educ Pract Vet 1996;19:275–289.
3. Robinson MRNorris RDSur RL, et al. Urolithiasis: not just a 2-legged animal disease. J Urol 2008;179:46–52.
4. Chigerwe MShiraki ROlstad EC, et al. Mineral composition of urinary calculi from potbellied pigs with urolithiasis: 50 cases (1982–2012). J Am Vet Med Assoc 2013;243:389–393.
5. Streeter RNWashburn KEMcCauley CT. Percutaneous tube cystostomy and vesicular irrigation for treatment of obstructive urolithiasis in a goat. J Am Vet Med Assoc 2002;221:546–549.
6. Fortier LAGregg AJErb HN, et al. Caprine obstructive urolithiasis: requirement for 2nd surgical intervention and mortality after percutaneous tube cystostomy, surgical tube cystostomy, or urinary bladder marsupialization. Vet Surg 2004;33:661–667.
7. Rakestraw PCFubini SLGilbert RO, et al. Tube cystostomy for treatment of obstructive urolithiasis in small ruminants. Vet Surg 1995;24:498–505.
8. Van Metre DCFubini SL. Ovine and caprine urolithiasis: another piece of the puzzle. Vet Surg 2006;35:413–416.
9. MacLeay JM. Urolithiasis. In: Smith BP, ed. Large animal internal medicine. 4th ed. St Louis: Mosby, 2008;950–958.
10. Mavangira VCornish JMAngelos JA. Effect of ammonium chloride supplementation on urinary pH and urinary fractional excretion of electrolytes in goats. J Am Vet Med Assoc 2010;237:1299–1304.
11. Janke JJOsterstock JBWashburn KE, et al. Use of Walpole's solution for treatment of goats with urolithiasis: 25 cases (2001–2006). J Am Vet Med Assoc 2009;234:249–252.
12. Halland SKHouse JKGeorge LW. Urethroscopy and laser lithotripsy for the diagnosis and treatment of obstructive urolithiasis in goats and pot-bellied pigs. J Am Vet Med Assoc 2002;220:1831–1834.
13. George JWHird DWGeorge LW. Serum biochemical abnormalities in goats with uroliths: 107 cases (1992–2003). J Am Vet Med Assoc 2007;230:101–106.
14. Bonanno PJLanders DERock DE. Bladder drainage with the suprapubic catheter needle. Obstet Gynecol 1970;35:807–812.
