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: https://drstephenbirchard.blogspot.com/2014/07/cryptorchidism-in-dogs-5-ways-to-make.html) The author frequently uses this approach, especially if exploratory of the entire abdomen is not necessary.  The paramedian approach avoids incising around the prepuce and preserves 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 ventral bladder between the stay sutures. 

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. 1)

Fig. 1: Remove calculi with a bladder spoon.

 

Fig. 2: A catheter in the penile urethra is used to retrograde flush calculi
into the open bladder during cystotomy. 

Flush with sterile saline through the urethral catheter until no further stones are recovered.(Fig. 2) Multiple flushes are usually required to remove all stones, especially small ones. Be patient and thorough to be sure all calculi are removed. Also flush the bladder lumen to remove stones adhered to the mucosa.

Bladder Closure

Although the traditional urinary bladder closure is a double inverting layer  (Fig. 3), a single layer, either simple interrupted or continuous, is preferred especially in bladders that are very thickened (Fig. 4a). 

Fig. 3: Traditional 2 layer closure of the cystotomy incision. (Cushing and Lembert pattern)

 

Fig. 4a: Simple interrupted closure of a cystotomy incision. Simple continuous pattern can also be used.

With single layer bladder closure, 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.

References

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