of insulin to drive potassium intracellularly. Exogenous insulin can also be administered; however, this should be used with caution to avoid iatrogenic hypoglycemia. A bolus of hypertonic bicarbonate (8.4%) can also be administered to drive potassium intracellularly in individuals without metabolic alkalosis. For individuals with bradycardia caused by severe hyperkalemia, calcium borogluconate and atropine can be administered.
Saline (0.9%) is a good empirical choice for fluid therapy in treatment of urolithiasis. Saline will help correct the hyponatremia and hypochloremia often present in individuals with urolithiasis and will not exacerbate the hyperkalemia. However, if metabolic acidosis is present, saline should be avoided. For individuals greater than 8% dehydrated, intravenous fluid therapy is ideal. However, in field circumstances or economic constraints, hypertonic saline and oral fluids provide a reasonable alternative. In severe hypovolemia, fluid therapy should be instituted prior to sedation or tranquilization. Due to the diuretic effect, alpha 2‐adrenergic agonists should never be used for tranquilization in cattle with urethral obstruction unless administered for sedation immediately prior to surgical relief.
Urethral rupture is diagnosed during physical examination. If present, this often will dictate the outcome and treatment plan for the individual. Generally, once a urethra has reached the point of rupture, severe urethral necrosis has occurred and attempting primary closure is futile. Typically, a perineal urethrostomy and salvage is the treatment recommendation with urethral rupture due to the high occurrence of urethral stricture at the site of rupture. If breeding soundness is desired, a urinary diversion technique such as a tube cystostomy or ischial urethrostomy should be performed to allow the site of urethral rupture to heal by second intention. However, prognosis for natural breeding soundness is poor due to the likelihood of peripenile adhesions from subcutaneous urine accumulation, as well as the possibility of urethral stricture and fistula formation. In cases with severe subcutaneous urine accumulation, skin incisions should be performed as needed to facilitate drainage to help reduce the degree of tissue necrosis, infection, and abscessation that occurs caused by the caustic nature of urine.
For cases with bladder rupture and uroabdomen, stabilization is required prior to pursuing surgical intervention. Ideally, intravenous fluids should be administered to correct severe dehydration and electrolyte disturbances prior to general anesthesia. For feedlot steers, hypertonic saline and oral fluids are a more economical choice. Drainage of urine from the abdomen should be performed with all cases of uroabdomen, but it is especially important to perform prior to placing any individual in dorsal recumbency. The drainage site should be surgically prepped and infiltrated with 2% lidocaine. A rumen trocar and cannula or thoracic catheter can be used to tap the abdominal cavity just medial to the caudal superficial epigastric vein [4]. The fluid should be drained slowly over 30 minutes or more preferably with intravenous fluid support to prevent circulatory shock. Rapid removal of uroabdomen at surgery should also be avoided because hypotensive crisis and death can occur. Ideally, the abdomen should be lavaged during surgery. However, cattle with uroabdomens do not develop peritonitis in experimentally created uroadodomen, so removal of urine is typically sufficient [11]. For valuable breeding animals, a cystorrhaphy is ideally performed via a standing laparotomy or ventral paramedian incision. However, access to the bladder can be difficult with a standing approach and often uroabdomen is the result of multiple small holes secondary to chronic overdistension and necrosis rather than a single rent. Often a ruptured bladder will heal without primary surgical repair. As long as the urinary bladder remains decompressed via a tube cystotomy, ischial urethrostomy, or indwelling urinary catheter, the rent in the bladder will form a fibrin seal and heal. A ruptured bladder can also heal with a perineal urethrostomy if urethral patency is established. Ventral tears are less likely to heal without primary surgical repair. Spontaneous healing of the bladder occurs in approximately 50% of animals following urethrotomy and drainage of the abdomen [17]. Cases of experimentally induced uroabdomen survived an average of 14 days until death [11]. The survival rate in steers with urinary bladder rupture is reportedly 90% in animals treated with tube cystostomy [18] compared with 55% [19] and 86% [20] in animals treated with cystorrhaphy, with or without urethrotomy and transurethral catheterization, respectively.
Unless an individual is to be immediately slaughtered, antibiotic therapy should be administered in preparation for any surgical intervention. Additionally, antimicrobials should be considered in cases managed with retrograde catheterization or where a urinary tract infection is suspected. Generally, beta‐lactams are appropriate due to their renal excretion. Antibiotics should be administered five to seven days postoperatively. For cases treated with an indwelling urinary tube or catheter, antibiotics should be administered for the duration of catheter or tube placement and continued for three to five days after removal.
Pain management should be administered to individuals treated medically and surgically. For postoperative pain, inflammation, and urethral swelling, non‐steroidal anti‐inflammatory drugs (NSAIDs) are recommended. Flunixin meglumine (1.1 mg/kg intravenous [IV]) is administered perioperatively for pain and inflammation. Caution should be used when administering flunixin meglumine to extremely dehydrated patients if immediate rehydration is not performed. Meloxicam (0.5–1 mg/kg per os [PO]) can be administered as needed postoperatively for pain. In cases where NSAIDs are insufficient for pain management, butorphanol (0.025–0.05 mg/kg intramuscularly [IM] or subcutaneously [(SC]) can be administered every six to eight hours in conjunction with NSAID therapy. Typically, the addition of opioids is only required for the first 24–48 hours postoperatively.
For cases with phosphatic calculi, urinary acidification is usually essential for treatment success. Ammonium chloride is recommended at 200 mg/kg orally every 24 hours for urine acidification. Due to the risk of causing metabolic acidosis, it is acceptable to start at 50 mg/kg orally every 24 hours and increase by 50 mg/kg until desired urinary pH is achieved. Phosphatic calculi will dissolve at a urinary pH range of 6–6.5, so the dose of ammonium chloride should be increased until this is achieved. Daily urinary pH should be monitored until a pH of 6–6.5 is reached. Feeding a dietary cation–anion difference (DCAD) ration is also an option to cause urinary acidification, but this is often difficult to implement for a single individual. In our clinic, we will often feed Soychlor®. Soychlor is utilized for DCAD rations in dairy cattle to aid in the prevention of hypocalcemia. For the cases in our clinics, we often feed 0.1–0.2 kg (0.25–0.5 lb) mixed with grain to create acidified urine. Soychlor eliminates the need for forced PO administration of ammonium chloride utilizing a balling gun to a patient and is easier than DCAD ration formulation. Urine acidification only needs to be performed until the clinician feels the stones dissolve due to the ruminant’s ability for renal compensation and realkalization of urine. Further, long‐term use of ammonium chloride can result in osteopenia.
Medical Management
Medical management is often unrewarding in the treatment of urolithiasis unless instituted early in the disease course. If the obstruction is recognized early, conservative therapy can be attempted with spasmolytic drugs and tranquilizers [2, 21, 22]. Phenothiazine tranquilizers are typically utilized which decrease urethral spasm and induce relaxation of the retractor penis muscles and straightening of the sigmoid flexure [2, 22]. In early cases, straightening of the sigmoid flexure and decreased urethral spasms may help urethral calculi to pass. However, if unsuccessful, retrograde urethral catheterization with hydropulsion can be attempted.
Retrograde catheterization is most easily performed in mature bulls versus castrated or prepubertal males due to the presence of persistent frenulum. Once exteriorization of the glans penis is accomplished, retrograde catheterization can be attempted with 8‐ to 10‐French polypropylene tubing. Infusion of lidocaine may assist with urethral spasm prior to attempting hydropulsion with saline. If significant resistance occurs, further attempts should be abandoned to prevent further urothelial trauma, and surgical intervention is necessary. Catheterization and hydropulsion are typically unsuccessful in cattle due to the presence of the urethral diverticulum and the chronicity in which most individuals present.
Surgical Management
Tube Cystostomy
A tube cystostomy is associated with the best long‐term prognosis