and/or hydroureter should be investigated. The right kidney extends from the 13th rib to the third lumbar vertebrae with the cranial pole in the renal impression of the liver in the 12tth intercostal space [15]. The left kidney can be imaged from the right paralumbar fossa caudal and is found slightly ventral to the right kidney from the 2nd to 5th lumbar vertebrae [15]. The left kidney can also be evaluated with transrectal ultrasound. If severe hydronephrosis is present, humane euthanasia is recommended (Figure 20.3). Presence of peripenile subcutaneous edema is suggestive of a urethral rupture and poor prognosis for returning to breeding soundness. Significant diffuse hypoechoic free fluid in the abdominal area is generally suggestive of uroabdomen. However, definitive diagnosis of uroabdomen is done by performing an abdominocentesis in either the flank fold of the abdomen or at the location of the fluid found ultrasonographically with an 18‐gauge, 3.8‐cm (1.5‐inch) needle after surgical prep. An abdominal fluid creatinine to serum creatinine ratio of 2 : 1 or greater confirms the diagnosis of uroabdomen [11, 16].
Figure 20.3 Severe hydronephrosis in a mature bull.
A baseline urinalysis can be performed. Common abnormalities include hematuria, proteinuria, and alkalinuria. Diagnosis of bacteriuria is beneficial to ensure a primary urinary tract infection is not the etiology of the urolithiasis. Baseline pH knowledge is important if urinary acidification is implemented. Ideally, if uroliths are obtained during surgery, the uroliths should analyzed to determine type. This information will help determine the best prevention strategy for the individual and herd. If urolith analysis is not feasible or delayed, a urolith can be placed in an acidifying solution to determine if urinary acidification would be a useful adjunct therapy. If available, urethroscopy can be utilized to assess location of the obstruction, extent of urothelial damage, and presence of strictures, or provide possible avenues for utilization of a laser or basket retrieval method.
Treatment
Immediate Care
Prior to initiating treatment for urolithiasis, the intended use of the animal, economics, site of obstruction, and integrity of the urinary tract should be considered. For acute cases, medical management can be attempted or immediate slaughter if uremia is not present. Most cases of urolithiasis will require surgical intervention. For breeding bulls, maintaining a patent urethra is paramount for successful outcome and breeding career. Surgical procedures utilized in breeding individuals include tube cystostomy, cystotomy, ischial urethrostomy, and urethrotomy. Surgical procedures utilized in salvage bulls and steers include ischial urethrostomy, perineal urethrostomy, and urethrotomy.
Before sedation or anesthesia, any severe electrolyte derangement should be corrected. For severe hyperkalemia, a bolus of 50% dextrose can be administered for an endogenous release 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
