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 in small ruminants for survival and breeding [1223–25]. This method provides urinary diversion, allowing the relief of urethral spasm and swelling and allows the urothelium time to heal. A tube cystotomy can be performed in dorsal recumbency via a paramedian incision or standing (Figure 20.4) via a left flank laparotomy (Figure 20.5) [26].
Figure 20.4 Placement of a Foley catheter in the tube cystotomy procedure.
Source: Courtesy of Rachel Oman.
Figure 20.5 Placement of a Foley catheter in the flank tube cystotomy procedure.
For a paramedian tube cystostomy, general anesthesia is preferred, but a lumbosacral epidural and/or local anesthesia can also be utilized. The individual should be placed in dorsal recumbency and surgically prepped from sternum to pubis. If a uroabdomen exists, fluid stabilization and abdominal drainage should be performed prior to placement in dorsal recumbency. A 10‐ to 15‐cm paramedian skin incision is performed approximately 2 cm lateral to the sheath approximately midway between the preputial orifice and pubis. A left‐sided paramedian approach is preferred, so the rumen can assist with keeping abdominal viscera in the abdomen. If bladder rupture is suspected, the incision should be more caudal to assist with access to the smaller bladder often residing in the pelvis. Sharp and blunt dissection is used to access the linea alba and a routine celiotomy is performed. A paramedian celiotomy can be performed instead if preferred by the surgeon.
Once the urinary bladder is localized, stay sutures with 2–0 or 0 monofilament can be placed in the bladder to assist with the cystotomy (Figure 20.6). A routine cystotomy is performed with aspiration of urine. Removal of uroliths from the bladder trigone and proximal urethra can be assisted with the use of a surgical spoon (Figure 20.6), as well as copious lavage and aspiration of sterile saline. An 8‐ to 10‐French polypropylene catheter is then passed in a normograde fashion with hydropulsion to attempt resolution of the urethral obstruction. If the obstruction is not relieved or there is significant resistance, hydropulsion attempts should cease and the catheter should be removed. A stab incision is made 2 cm lateral to the paramedian skin through the skin and abdominal wall. A curved hemostat can be used intra‐abdominally and directed toward the skin and incised over while placing pressure on the hemostat. The hemostat is used to grab the balloon end of a 20‐ to 30‐French Foley catheter to assist with placement through the skin and abdominal wall. The balloon integrity of the Foley catheter should always be ensured prior to placement. Once the Foley catheter is in the abdomen, a separate stab incision is performed lateral to the primary cystotomy incision. A hemostat is placed through the stab incision of the bladder and the balloon end of the Foley is placed into the lumen of the bladder. The balloon is filled with the appropriate volume of saline.
Figure 20.6 Utilization of stay sutures to assist with bladder manipulation and cystotomy. Utilization of a surgical spoon to assist with urolith removal.
Once filled, the balloon is directed toward the trigone of the bladder while the cystotomy incision is made and is sutured. A single‐ or double‐layer continuous inverting pattern using absorbable monofilament 0 or 2–0 suture is used for the cystotomy and, if needed, cystorrhaphy. The balloon of the Foley catheter is pulled flush against the bladder and abdominal wall. Some surgeons choose to place a purse string suture around the Foley catheter [27]. The celiotomy, subcutaneous tissues, and skin are closed in a routine fashion. During closure, copious lavage with saline into the Foley catheter is important to prevent occlusion from any blood clots. A Chinese finger cuff ligature is used to secure the Foley to the ventral abdomen. After placement of the Chinese finger cuff ligature, saline should
