URINARY TRACT TRAUMA
Lillian Aronson VMD,† Diplomate ACVS
Department of Clinical Studies, Philadelphia
University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA
Trauma can involve the kidneys, ureters, bladder or urethra. Urinary tract trauma can be associated with automobile accidents or falls, penetrating wounds secondary to bites and penetrating foreign bodies, and forceful catheterizations.† The kidneys and ureters are considered retroperitoneal and the bladder and proximal urethra are considered intraperitoneal. Because of their retroperitoneal location, the kidneys and ureters are less commonly damaged when compared to the bladder and urethra.
The distinction between the retroperitoneal vs the intraperitoneal space is an important concept to understand when evaluating these patients since the site of trauma can often effect the animalís clinical presentation and, as a result, the ability to make a prompt and accurate diagnosis.†
A diagnosis of urinary tract trauma is based on history, physical examination, clinical pathological findings, evaluation of peritoneal fluid (if present), abdominal radiographs, abdominal ultrasound and contrast studies.† Not only is it important to make a diagnosis, but the aim is also to determine the location of urinary leakage.
Depending on the time delay until diagnosis, many patients will have electrolyte and acid base abnormalities which need to be corrected as much as possible prior to surgery since these changes can make them poor anesthetic candidates. Urinary leakage can result in dehydration, azotemia, hyperkalemia, acidosis and hypovolemic shock.† The rate of fluid administration as well as the type of fluid therapy should be based on a patientís specific needs. Although potassium free solutions such as 0.9% saline are recommended, a balanced electrolyte solution such as Normosol-R will correct hypovolemia and not contribute substantially to the serum potassium on an acute basis.†† Dogs are typically started at a rate of 60-90ml/kg/hr and cats at a rate of 40-60ml/kg/hr.† The patient is then reassessed halfway through their initial fluid bolus and the rate adjusted accordingly.
Additionally, these patients need to be evaluated very carefully for other systemic injuries. If enough force was present to cause trauma to the urinary tract, there is a reasonable chance that other organ systems may have been affected. Along with trauma to the urinary tract, these patients may present with a life threatening bleed associated with splenic or hepatic trauma as well as respiratory distress associated with thoracic trauma.† Thoracic radiographs should be performed on any trauma patient to rule out pulmonary contusions, rib fractures as well as a possible diaphragmatic hernia.
An ECG should be placed and if hyperkalemia is present, it should be treated accordingly.† Cardiac arrhythmias are first apparent at potassium levels of 8mmol/L when the P-R interval becomes prolonged.† As the hyperkalemia becomes more severe, the QRS complexes become wider, the T waves become taller and the P waves flatten and eventually disappear.† In addition to the intravenous fluid therapy, treatment for hyperkalemia often includes intravenous 10% calcium gluconate (50-100mg/kg given slowly over 5 minutes with continuous ECG evaluation) and/ or regular insulin (.1-0.25 U/kg) and dextrose (1-2 g/unit of insulin).† In patients that are severely acidotic, sodium bicarbonate can be administered.† The recommended dose of sodium bicarbonate administration is 0.3 X base deficit X body weight (kg).† One half of the dose is given slowly IV over 15 to 30 minutes and then the acid base status of the patient is reassessed.
In some patients temporary peritoneal dialysis or urinary diversion may be necessary. To perform peritoneal dialysis, the caudal abdomen is prepared for aseptic surgery and a local anesthetic is infused.† A small stab incision is made in the caudal abdomen and the peritoneal catheter introduced.† The catheter is advanced off of the stilette, sutured to the ventral abdomen and connected to a sterile closed urine collection system.
Isolated renal trauma is often difficult to diagnose.† Historical information in conjunction with the presence of gross or microscopic hematuria and pain on palpation in the sublumbar region may be suggestive of a primary renal injury, however are not pathognomonic for the condition.† Abdominal ultrasound may reveal some fluid accumulation surrounding the kidney in the retroperitoneal space.† Occasionally, renal injury can be confirmed by excretory urography, however often the diagnosis is made during exploratory surgery.† Treatment of renal trauma is dictated by the extent of injury.† Lacerations of the kidney can be sutured, however if severe injury has occurred a partial or complete nephrectomy may be necessary.
Unilateral ureteral tears secondary to trauma are difficult to diagnose if urine accumulation is confined to the retroperitoneal space.† Clinical signs in these patients are often vague and may include lethargy, dehydration, sublumbar pain, vomiting, anorexia and pyrexia. Clinicopathological findings in these patients are typically normal. Abdominal radiographs often reveal a loss of retroperitoneal detail and an increased size of the retroperitoneal space. Abdominal ultrasound may identify fluid accumulation in the retroperitoneal space.† If both ureters are disrupted, signs of acute azotemia will occur.† If urine leakage enters the peritoneal cavity, a uroperitoneum will develop.† Excretory urography is beneficial in cases of both unilateral and bilateral ureteral abnormalities.
Treatment options for ureteral abnormalities is often dictated by patient stability, function of the remaining kidney and location of the injury. Options include primary repair, ureteral reimplantation and ureteronephrectomy.† In some cases a percutaneous nephrostomy tube may be beneficial in diverting urine away from the surgery site.
Traumatic bladder rupture is the most common cause of a uroperitoneum.† Traumatic bladder rupture can also occur secondary to aggressive palpation or poor catheterization technique. Urine leakage into the peritoneal cavity results in uremia, dehydration, hypovolemia and death if untreated.†† It is important to remember that patients may urinate normally if a small leak is present and the ability to retrieve fluid on bladder catheterization does not preclude the diagnosis of a ruptured bladder. Additionally, the inability to palpate a urinary bladder as well as the presence of a fluid wave is supportive of a diagnosis of uroperitoneum.
To diagnose a uroperitoneum, the concentration of the creatinine and urea in the fluid retrieved on abdominocentesis should be compared with that of the peripheral blood.† The urea molecule is small and rapidly equilibrates across the peritoneal membrane.† The creatinine molecule is a larger molecule and diffuses more slowly.† As a result, in a patient with a uroperitoneum, the creatinine level in the abdominal fluid is higher than that of the serum. Abdominal radiographs in these patients may reveal a loss of abdominal detail as well as the absence of the urinary bladder.† Positive contrast cystography, with leakage of contrast material out of the bladder, provides a diagnosis of a ruptured bladder as the cause of the uroperitoneum.
Treatment of a patient with a bladder rupture include stabilization of the cardiovascular system, treatment of any life threatening metabolic abnormalities and then definitive surgical repair of the bladder. An exploratory laparotomy is performed and the damaged area of the bladder is debrided and sutured in either a single interrupted appositional pattern or a two layer closure.† Because of the chemical peritonitis that can occur with urine leakage, copious lavage of the abdominal cavity is recommended prior to closure.
Both partial and complete urethral tears can also occur secondary to trauma.† Urethral lacerations and ruptures are associated with pubic fractures, fractures of the os penis, penetrating wounds and iatrogenic injury secondary to urethral examination, catheterization and surgery on or adjacent to the urethra.† Clinical signs will vary depending upon the location of the rupture.† A proximal urethral rupture can result in a uroperitoneum and clinical signs similar to a patient with a ruptured bladder.† A distal urethral tear will result in urine leakage into the surrounding soft tissues.† This is manifested as swelling, pain and cellulites in those areas.† A diagnosis of urethral rupture is confirmed by retrograde urethrography.† To accurately determine the site of rupture, positive contrast material is injected slowly into the urethra using fluoroscopy.
Surgery for urethral trauma often includes primary repair and urinary diversion.† Urinary diversion can be accomplished by a cystostomy tube or by an intraurethral catheter. In some cases, urinary diversion +/- a urethral stent may be performed without primary repair.†† Primary suture repair is the best treatment for complete urethral rupture or avulsion of the urethra from the bladder.