Stephen J. Birchard DVM, MS, Diplomate ACVS

Saturday, October 11, 2014

Cystotomy for Removal of Cystic and Urethral Calculi in Dogs: Are you getting them ALL out?

The short answer is: maybe not! Cystotomy to remove urinary calculi is one of the most common surgeries performed in small animal private practice. It is a surgical procedure that is considered to be straightforward and easily performed. However, removal of all calculi can be challenging. One study found that in 20% of dogs cystotomy failed to remove all calculi.(1) 

Key Point: Recurrence of calculi after cystotomy may be due to calculi left behind rather than formation of new stones.

During cystotomy, small stones in the urinary bladder tend to gravitate into the neck of the bladder and the proximal urethra. These will need to be removed by flushing them into the bladder using a urethral catheter. This retrograde flushing is a critical part of the surgery to remove all calculi present and leave none behind.

Preoperative preparation

After inducing general anesthesia, place the dog on its back and pass a lubricated sterile catheter into the urethra. If possible, empty the urinary bladder using the catheter, or perform cystocentesis to empty the bladder to reduce intraluminal bladder and urethral pressure. Flush the urethra with sterile saline to flush stones retrograde into the bladder. Sterile KY jelly can be mixed with the saline to lubricate the calculi and facilitate retrograde flushing. If necessary, have an assistant compress the urethra with a finger in the rectum while initially injecting saline in the catheter to help generate pressure in the urethra causing it to dilate.  Release the urethral pressure during flushing to allow stones to pass through the urethral lumen and enter the bladder. Leave the catheter in while prepping the abdomen for surgery to prevent stones from migrating back into the urethra.

Surgical Technique

Place the dog in dorsal recumbency and drape the penis in the operative field. This will allow passage of a sterile catheter during surgery and retrograde flushing after the cystotomy has been performed.

The urinary bladder is approached through the ventral abdominal midline.  An alternative in the male dog is the paramedian abdominal approach. (See blog on surgical removal of cryptorchid testicles, 2/29/14.) The author frequently uses this approach, especially if exploratory of the entire abdomen is not necessary.  The paramedian approach avoids incising near the prepuce and preputial vessels and muscle.

After opening the abdomen, identify and exteriorize the urinary bladder and place stay sutures on the ventral aspect of the bladder. Isolate the bladder with moistened laparotomy sponges to prevent urine spillage into the abdominal cavity.  Make an incision in a relatively avascular area of the bladder between the stay sutures. (Fig. 1) 
Fig. 1: Technique for incision and closure of cystotomy. Traditional double inverting closure shown here;
simple continuous or interrupted preferred in thickened bladders.
(reprinted from: Fingland RB. Surgery of the urinary bladder. Saunders Manual of Small Animal Practice, 1st ed., Birchard and Sherding editors,  Figure 1, Elsevier, 1994, pg. 839)
The entire bladder lumen is examined.  Excise a small sample of bladder mucosa and submit for bacterial culture. Remove calculi using a bladder spoon. (Fig. 2)
Fig. 2: Remove calculi with a bladder spoon.
The urethra is repeatedly retrograde flushed using the urethral catheter. (Fig. 3) 
Fig. 3: A catheter in the penile urethra is used to retrograde flush calculi
into the open bladder during cystotomy. 
Continue to flush until no further stones are recovered. Although the traditional urinary bladder closure is a double inverting layer  (Fig. 1), a single layer, either simple interrupted or continuous, is preferred especially in bladders that are very thickened (Fig. 4a). 
Fig. 4a: Simple interrupted closure of a cystotomy incision
Take full thickness bites of the bladder wall but grab only a small amount of the mucosa.  Absorbable sutures are used (3-0 or 4-0 Monocryl). Leak test the bladder incision by injecting sterile saline into the bladder lumen.(Fig. 4b) Place additional sutures if leaks are found. 
Fig. 4b: Leak test of a cystotomy incision by injecting sterile saline into the bladder lumen
Lavage the bladder and surrounding area of the abdomen and perform routine abdominal closure.

Prior to recovery from anesthesia, obtain abdominal radiographs to confirm that all stones have been removed. (Figs. 5a,b)
Fig. 5a: Preoperative radiographs of a dog showing radiopaque calculi in the urinary bladder.
Fig. 5b: Immediate postoperative radiographs of same dog in Fig. 5a showing removal of all calculi.
If additional stones are seen, take the animal back to surgery to remove them.

Postoperative Care

Routine supportive care is administered postoperatively, such as intravenous fluids, analgesics, and antibiotics if necessary. Indwelling urethral catheters can be used if necessary because of urethral damage, bladder rupture, or if the bladder needs to remain decompressed for other reasons.

Long-term antibiotic therapy is prescribed if the urine or mucosal culture was positive. Always submit calculi for analysis. Further recommendations such as dietary therapy and other measures are made to prevent recurrence of stones.


1. David C. Grant; Tisha A. M. Harper; Stephen R. Were. Frequency of incomplete urolith removal, complications, and diagnostic imaging following cystotomy for removal of uroliths from the lower urinary tract in dogs: 128 cases (1994–2006) J Am Vet Med Assoc 2010;236:763–766


  1. I have both seen (once)and personally experienced (once) non-palpable calculi that seemed to be intramural. In both of these cases, the stones seemed to be incorporated into the bladder wall. Both cases were backflushed multiple times. I backflushed a male dog with a foley catheter and did not palpate additional calculi. Post operative radiographs showed the existence of two to three tiny stones. I chose to not pursue the remaining calculi.
    I was thinking about the additional risk of another anesthetic procedure in the same day with the same patient as opposed to letting the small calculi pass.
    The additional calculi were non-palpable in either case and there was no post-operative consequence. What is the correct way of thinking about this circumstance?

  2. Dr. Birchard,
    I have done many cystotomies over the course of a long career. I witnessed one case of retained cystic calculi post-op that were proven radiographically and that neither I, or my associates,could palpate. It was decided to let the dog recover from anesthetic after many hours of searching via palpation and backflushing. The dog recovered without complication though the stones were visible in the same spot in the bladder neck at both 1 month and 3 months post operatively. Could the three small stones have been intramural?

    I encountered a second similar case several years ago. The stones were not palpable in the neck of the bladder or the proximal urethra. We backflushed several times without result. The presence of the small calculi was discovered on post-operative radiographs. It was again decided to let the stones pass uneventfully as opposed to re-opening the bladder and taking the added risk of a much longer anesthesia. We wanted to retake the radiographs at one and three months and to treat the remaining uroliths medically. We would change the approach depending on the pending stone analysis, in addition to close monitoring of the patient via telephone/video and by examination. I was confident that the dog would recover uneventfully and that there would not be further issue as I felt that these calculi were also intramural. These cases are exceedingly rare though I had already witnessed one. I have only found one reference of intramural cystic calculi in a dog. Even though these two cases recovered without incident I have no histopathologic evidence to support my supposition that the calculi were intramural and not intraluminal. While the results were good in both cases was the reasoning sound?
    Thank-you for your time
    Mark Freiberg DVM, Dipl. ABVP

  3. Hello Dr. Freiberg, I haven't seen many cases where I thought the stones were intramural, although I have seen them be sort of stuck to the mucosa. I still think when we see retained calculi immediately after cystotomy we should go back in and try to remove them, especially in a male dog that is more prone to urethral obstruction. But, I like your thoughts about at least treating the remaining stones medically based on stone analysis, and serial radiographs to monitor the stones. The main point of this post was to alert people to the possibility that recurrence of cystic calculi in dogs may actually be due to incomplete removal of them at surgery. Thanks. SJB