Department of Clinical Veterinary Medicine, Division of Small Animal Surgery, Vet Suisse University Bern-CH
Urinary tract rupture is one of the most common problems associated with trauma to the pelvis and the hind legs.
The presence of increased concentration of potassium in the abdominal cavity will lead to a mild chemical peritonitis. Dehydration and fluid shifts into the peritoneal cavity are present due to accumulation of hyperosmolar urine in the abdomen. Hyperkalemia, azotemia and dehydration lead to a metabolically unstable patient. However an uroabdomen should not be considered a surgical emergency. Concurrent injuries like pulmonary contusion/ pneumothorax or head trauma are important risk factors if immediate surgical intervention is planned. Uremic patients are especially sensitive to anaesthetics, analgesics and sedative drugs. Hyperkalemia can lead to bradycardia and ECG changes like small or absent P waves, prolongation of P-R intervals, widened QRS complexes and spiked T waves.
Initial resuscitation includes correction of cardiovascular abnormalities and correction of electrolyte disturbances with aggressive fluid therapy and urinary drainage to decrease third space fluid loss and danger of peritonitis. Urinary drainage is the optimal possibility to gain time and to stabilize a polytrauma patient prior to surgery. Urinary drainage without surgery for 48 h and longer can be done. The drainage procedures consist in placement of a urinary catheter and a peritoneal catheter. In spite of a tear in the bladder wall, urine frequently continues to accumulate within the bladder. A urinary catheter will reduce the pressure on the traumatized bladder wall and may aid in the drainage. The abdominal catheter however will drain the majority of urine. It is best to insert a multi luminal catheter.
Blood urea nitrogen, creatinine and potassium are elevated in cases of uro-abdomen. Serum chemistry values become a more important tool for diagnosis if they are evaluated in the context of biochemical values from abdominal fluid.
With increased cavitary fluid, radiographs will display a loss of contrast. Loss of retroperitoneal detail would indicate retroperitoneal bleeding or kidney/ureteral rupture. Sometimes free abdominal air can be seen. Gas forming bacteria, penetrating trauma and gastrointestinal perforations are reasons for free abdominal air. Abdominocentesis prior to the radiological examination has to be excluded in the case of signs of free peritoneal air.
Ultrasound examination has an important role in the diagnosis of urinary tract trauma. Structures of organs, masses and fluid accumulation can be identified readily with ultrasound, especially in the retroperitoneal space. Since it is possible to do ultrasound guided local fluid aspiration, ultrasound has replaced diagnostic peritoneal lavage (DPL) procedures in our hospital. It has been reported that 5-6 ml/kg of fluid was necessary to obtain a fluid sample by blinded abdominocentesis and that a negative result should be followed by a DPL. Local fluid pockets can be easily identified with ultrasound and aspirated under controlled circumstances, decreasing the necessary fluid amount for a positive result.
Abdominocentesis is a very useful diagnostic step for patients with peritoneal trauma. Fluid is retrieved with a single tap in the umbilical region or by ultrasound guided aspiration. Local anesthesia is only necessary if a large peritoneal catheter is introduced for temporary fluid drainage. Usual 20G catheter taps do not need anesthetic pretreatment. A needle is slowly advanced into the peritoneal cavity. This will allow intestinal structures to be pushed away and diminish the risk of intestinal perforation. The risk of perforation is higher with increased intraabdominal pressure and with organomegaly. Splenic puncture is the most common iatrogenic problem but is usually not followed by serious consequences. Splenic or vascular perforation can be diagnosed by observing clotting of the retrieved sample. Free blood from the abdomen does not tend to form clots due to protective fibrinolytic properties of the peritoneal surface.
Bloody fluid is tested for PCV/TS and BUN/ Creatinine. In cases of uroabdomen, the fluid potassium and creatinine concentrations are higher than concurrent serum concentrations, indicating the need for contrast studies to localize the urinary tract rupture.
Positive contrast studies should be performed in the following order. A retrograde cystourethrogram should be done first to evaluate the integrity of the urethra and the urinary bladder. Extravasation of contrast medium in the surrounding tissues identifies a urinary tract rupture. It is necessary to distend the urinary bladder with contrast material to ensure that also small tears in the bladder wall are detected. If an uroabdomen or a distension of the retroperitoneal space is present and a cystogram turns out to be normal an excretory urography should be performed to evaluate the integrity of the kidneys and ureters. Detailed information regarding the location, size and the morphology of the kidneys and the ureters can be obtained with this technique.
In cases of distal urethral rupture it is possible to have laboratory values within normal limits. These animals will often have urinary leakage into the inguinal region and into the fascial planes of the hind legs. The dominant clinical sign will be severe pain and edematous swelling in this area. Especially traumatized cats presented with pelvic trauma and these clinical signs should be carefully evaluated with positive contrast studies.
Aggressive medical stabilization together with urinary and abdominal catheter treatment should allow definitive surgical treatment under general anesthesia within 24-48h.
Urethral tears can often be managed with catheters over a prolonged time and do not need surgical intervention. Complete avulsions should however be treated surgically.
Urinary bladder rupture should routinely lead to a surgical exploration. The author however has seen small tears to become sealed with urinary catheter placement and without surgical treatment. Surgical treatment of the ruptured bladder wall is usually a routine procedure. The bladder is elevated with small stay sutures to facilitate handling of the tissues. The injured area and the bladder lumen is very gently inspected to remove large blood clots. The traumatized area is debrided making sure that the ureters and the trigone are not damaged. A water tight closure with small monofilament suture is performed. The author prefers to use a single continuous pattern trying to penetrate the mucosa as little as possible.
Injuries to the kidney, ureters, the trigone or total avulsions of the bladder neck are surgical problems that should be evaluated by an experienced surgeon.
Assessment of contralateral renal function before surgical treatment of ureters and kidneys is critical. Although microsurgical techniques are available with the goal to preserve a functional kidney following trauma, it is not unusual that ureteral or renal injuries lead to a unilateral nephrectomy. Partial nephrectomy is technically possible but in the author's hand rarely appropriate.