Endoscopic Removal of Urinary Calculi
By: Jacqueline Carver, DVM, Dip. ACVS Staff surgeon
Public interest in less invasive procedures, especially for pets who have recurrent urinary calculi, has increased dramatically over the last ten years. Fortunately, endoscopic techniques are continually updated and improved to give pet owners the option of a least invasive procedure for removal of calculi. Most cystic calculi can be removed by either transurethral or laparoscopic assisted cystoscopy. Of course, there are exceptions, but overall these techniques decrease trauma to the urinary bladder as well as dramatically improve the visualization of even the smallest calculi as well as concurrent disease conditions such as strictures, polyps, neoplasia, and persistent suture from prior cystotomy closure.Transurethral cystoscopy for stone removal can be attempted in female cats and dogs if the calculi are small enough to be pulled through the urethra. In general, stones that are twice the diameter of the largest cystoscope appropriate for the patient can be removed by this method. In male dogs, the size limitation is much smaller due to the narrowing of the urethra at the os penis. Most male dogs, as well as male cats, are best treated with laparoscopic assisted cystoscopy. After transurethral cystoscopic evaluation of the lower urinary tract, a basket retrieval instrument is introduced through the operating channel of the cystoscope. The basket is opened in the area of the stone and gradually closed, trapping the stone. The stone is then gently removed. This procedure is repeated until all stones are removed. Flushing and applying gentle external pressure to the bladder will allow tiny stones to be flushed from the bladder through the cystoscope sheath as well. Because the urethral length and diameter are dependent on the size and breed of dogs, a variety of cystoscope sizes should be available. For most small dogs and cats, a 1.9 mm scope will suffice. For midsize dogs, a 2.7 mm scope is used. For large dogs, we have a 5.0 mm scope available.
Laparoscopic assisted cystoscopy involves the use of a rigid cystoscope and either retrograde flushing or use of a basket retrieval instrument to remove urinary calculi. In the originally reported technique, two trocars are placed via 1.0-2.0 cm abdominal incisions and the abdominal cavity is insufflated with carbon dioxide to maximize visualization. The first trocar is placed on the midline just caudal to the umbilicus. The laparoscope is placed through this trocar to enable visualization of the bladder apex. A second trocar is placed caudal to the first, in the approximate area of the bladder apex. While visualizing the bladder, a forcep is inserted through the second trocar and the bladder grasped and pulled toward the body wall. The bladder is not exteriorized, but rather secured to the abdominal wall with four interrupted stay sutures to prevent urine contamination of the peritoneum. Once the bladder is secure, a small cystotomy is created(6-10mm) and a rigid cystoscope is introduced into the bladder. The bladder and urethra are evaluated and the stones subsequently removed by the technique preferred by the surgeon. Use of surgical suction on the trocar sheath while retrograde flushing through a previously placed foley catheter expedites the removal of small calculi. After the procedure is complete, the bladder is closed with a single layer appositional pattern. The trocar sites are closed routinely. More recently, a transvesicular percutaneous cystolithotomy procedure was described by Dr. Runge et. al. A transurethral catheter is placed and the urinary bladder is distended with saline. A single 1-2 cm incision is made in the body wall over the anticipated area of the bladder apex. The bladder is grasped and secured to the body wall. A threaded cannula is placed into the bladder lumen, through which an cystoscope is placed. Stones are retrieved by the same previously described methods. This procedure has the advantage of requiring only one trocar site and does not require insufflation of the abdomen. Laparoscopic cystoscopy can also be performed during an open abdominal procedure. For example, during surgical correction of a portosystemic anomaly, a cystoscopic evaluation for concurrent bladder stones can be done.
The high recurrence rate of uroliths in our veterinary patients is probably multifactorial in cause. Certainly many dogs have a metabolic predisposition to stone formation. Altered urine pH and urinary tract infections account for some recurrent stone formation. But we must also consider the possibility that some stones are left behind after surgery. In some reports, as many as 20% of dogs and cats had immediate postoperative radiographic evidence of residual uroliths. That statistic is likely higher, as many residual stones may not even be visible on radiographs. This likely contributes to many of our cases of “repeat offenders”. We have all dealt with those frustrating cases of sometimes yearly recurrence of bladder stones. As a surgeon, I was always 100% confident that all stones were removed after performing a routine open cystotomy. Since routinely using a cystoscopic approach, I am now 100% confident that I was unable to visualize the smallest stones. Endoscopic evaluation of the urinary tract is superior to visual inspection, and makes the chance of leaving stones less likely. In addition,owners report far fewer post operative complications such as continuous hematuria, stranguria, and discomfort. Now I’m a believer!
Laparoscopic view of the urinary bladder
Bladder calculi visualized through laparoscope. The small stones were not seen without the scope.
Tiny stone in the jaws of a laparoscopic forcep. This stone was not seen without the scope.
Basket retrieval instrument used for transurethral and laparoscopic assisted procedures.