Urolithiasis in Small Ruminants
Obstructive Urolithiasis in Small Ruminants and Prevention
Urolithiasis in small ruminants, including cattle, sheep, and goats, leads to the formation of urinary calculi, resulting in obstructions that cause bladder distention, abdominal pain, and potential urethral complications. This condition, prevalent during winter, affects young feeder and mature breeding animals, often leading to severe outcomes like uremia or septicemia.
Winter conditions and high-grain diets worsen the issue, particularly impacting male goats. Urolithiasis, a major cause of urinary tract problems in small ruminants, significantly affects livestock, show animals, and pets globally. Urethral obstructions primarily target intact and castrated males at the urethral process and sigmoid flexure due to diverse factors like diet, age, sex, and genetics.
Factors such as water mineral composition and dietary imbalances contribute to urolithogenesis. Struvite, calcium carbonate, and calcium oxalate calculi exhibit distinct appearances, often affecting the distal sigmoid flexure of cattle and the sigmoid flexure and urethral process of sheep and goats.
Urolithiasis manifests in varying clinical signs influenced by obstruction severity, calculus composition, and location. While often calcium or phosphatic-based, diverse calculi types exist. Surgical intervention becomes essential when conservative measures fail, intensifying the complexity of management. Clinical signs range from blood-tinged dribbling urine in partial obstruction to severe manifestations like tenesmus, colic symptoms, and rectal prolapse in complete obstruction. Severe consequences encompass bladder rupture, urethral perforation, and hydronephrosis.
Ruminant urolithiasis, rooted in nutritional imbalances, primarily manifests as urethral obstruction. Notably, calves, lambs, and early-castrated kids subjected to high-grain diets with an imbalanced calcium:phosphorus ratio or excessive magnesium intake are prone to struvite and ammonium urate calculi. Grazing on silica-rich soil heightens the risk of silica urolith formation, while high-calcium plants like subterranean clover foster calcium carbonate uroliths.
Diagnosis often employs ultrasound and radiographs to visualize bladder distention and stone presence, aiding in tailored intervention.
Treatment strategies encompass dietary adjustments, promoting urinary chloride excretion, urine pH reduction, and maintaining a balanced calcium:phosphorus ratio. Sodium chloride supplementation enhances urine solubility, and ammonium chloride acts as an acidifying agent. In cases of significant urolith issues, ration evaluation is pivotal, and specialized dietary supplements are available.
Advanced Surgical Approaches for Urolithiasis Management
Urethral Process Amputation: This procedure involves the removal of the short, constricted urethral process at the tip of the penis. While enabling uroliths within this area to pass, recurrence is possible if higher obstructions exist in the urethra.
Perineal Urethrostomy: Creating a novel urinary opening near the perineum allows urination akin to females. This intricate procedure may involve heavy sedation or general anesthesia, particularly for valuable animals, and aims to restore urinary flow following urolith-induced blockage or rupture.
Tube Cystostomy: In cases of urethral blockage or rupture, this approach diverts urine away from the compromised area, aiding tissue healing. A rubber tube is surgically placed in the bladder, often accompanied by urethral process amputation and urolith removal.
Prepubic Cystostomy: For recurrent obstructions, a permanent opening is created between the bladder and belly wall near the prepuce, enhancing urinary flow.
Urethral Translocation: A complex technique involving attachment of the urethra to the lower penis or prepuce section, often utilized to circumvent a ruptured or failed urethrostomy.
Given potential complexities, advanced urological procedures necessitate specialized training, especially for valuable or beloved animals. Veterinary referrals to skilled surgeons experienced in these intricate techniques, ideally those board-certified by the ACVS, offer the best chance for successful outcomes.
Prevention and Management of Urolithiasis in Small Ruminants
PREVENTION:
To thwart the onset of urolithiasis, several crucial measures have been identified:
Diet Management: Refrain from feeding horse grain to small ruminants due to inadequate diet balance, which escalates the risk of urolith formation.
High Grain Diets: Show animals on relatively high grain diets should incorporate salt (sodium chloride) at a rate of 2 to 5%, or alternatively, ammonium chloride at 0.5 to 1%, to boost urine production or acidify urine.
Calcium and Phosphorus Balance: High calcium diets might impede phosphorus absorption. Consult veterinarians before introducing supplements to the feed.
Urinary Chloride Excretion: For preventing struvite calculi, increasing urinary chloride excretion is crucial.
Urine pH Reduction: Lowering urine pH plays a significant role in struvite calculus prevention.
Calcium: Phosphorus Ratio: Maintaining a 2:1 calcium to phosphorus ratio in the complete ration is pivotal.
Concentrate Feeding: Intensive concentrate feeding, common in finishing programs, necessitates adequate calcium supplementation to deter urolith development and urethral obstruction.
Sodium Chloride Addition: Supplementary sodium chloride up to 4% of the total ration boosts sodium and chloride concentration in urine, encouraging water intake and mineral solubility.
MANAGEMENT:
In cases where prevention falls short, comprehensive management strategies include surgical and medical interventions:
Surgery: Surgical removal of uroliths and relief of obstruction are standard practices.
Medical Treatment: Initial management might encompass urine acidifiers, dietary modifications, and amputation of the urethral process. Surgical options are explored if medical approaches prove insufficient.
By diligently adhering to prevention measures and pursuing appropriate management strategies, the impact of urolithiasis on small ruminants can be significantly mitigated.
REFERENCES:
UROLITHIASIS IN SMALL RUMINANTS. American College of Veterinary Surgeons
Mejía, S. Small Ruminant Urinary Obstruction: decision trees for treatment. Journal of the American Veterinary Medical Association. Vol 260, Issue S2. 2022.
Aiello SE. The Merck Veterinary Manual. 11th ed. Merck & Co. 2016.
RECOMMENDED LINKS:
American College of Veterinary Surgeons: UROLITHIASIS IN RUMINANTS.
JAVMA: Small Ruminant Urinary Obstruction.
