Author

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.

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

Wednesday, October 1, 2014

Scrotal Urethrostomy in Dogs: Good surgical technique makes all the difference.

Urethrostomy is the surgical procedure that creates a permanent opening between the urethral lumen and the skin, and is indicated for several disease conditions such as recurrent urinary obstruction due to calculi, trauma or neoplasia.  Urethrostomy in the dog can also be performed when penile amputation is necessary for neoplasia or other conditions, such as hypospadias.

Several types of urethrostomy have been described for dogs, but scrotal urethrostomy is currently the procedure of choice.(1-3) After castration and scrotal ablation, the urethra is opened at the level of the scrotum and sutured to the adjacent skin.

Advantages of scrotal urethrostomy are:
  • the urethrostomy stoma is located ventrally on the dog, minimizing urine scald of surrounding skin
  • the urethra is relatively close to the skin at this location
  • the scrotal portion of urethra is large enough to allow formation of a large stoma that allows passage of calculi and rarely strictures
  • urinary continence is not compromised by developing a stoma at this location.

           
Surgical Technique for Scrotal Urethrostomy

Under general anesthesia place the dog in ventral recumbency. If possible, pass a urinary catheter to flush calculi retrograde into the urinary bladder (if applicable), and leave in to help with identification of the urethra during dissection. Prepare the scrotum, ventral abdomen, and ventral perineum for aseptic surgery. Make an elliptical incision around the base of the scrotum. Be sure to leave sufficient skin to allow for a tension-free closure of skin to urethral mucosa. Perform scrotal ablation and castration in a routine fashion. (Fig. 1)  
Fig. 1: Beginning of a scrotal ablation by performing castration and scrotal ablation.
Dissect through the subcutaneous tissue and identify the retractor penis muscle. (Fig. 2) Dissect the muscle away from the urethra and retract it laterally to the urethra using forceps or a stay suture. 
Fig. 2: Dissection through the subcutaneous tissue exposing
the retractor penis muscle (black arrow), and urethra(white arrow).
Incise the urethra on the midline with a scalpel (4-6 cm opening). (Fig. 3a,b) 
Fig. 3a: Incision is made on the urethral midline with a scalpel.
The incision can be started with a scalpel and extended with fine scissors.
Fig. 3b: Completed urethral incision. Note urinary catheter in the urethral lumen.

Suture the urethral mucosa and submucosa to the skin with fine suture material (4-0 PDS or Monocryl, swaged-on taper needle) in a simple continuous pattern. (Figs. 4-9) Start the suture line at the caudal aspect of the incision, and work cranially. 
Fig. 4: Surgical model of the penis and tissue layers important for urethrostomy.
(TA = tunica albuginea)
Fig. 5: Closure of the urethrostomy begins with 2 lines of sutures at the caudal aspect of the incision.
 Place the sutures in a “3-bite” manner: urethral mucosa first, then the tunica albuginea (fibrous covering of the corpus cavernous urethra), then a split-thickness bite of the skin. This helps to close and seal the cavernous layer of tissue, preventing excessive postoperative hemorrhage. The simple continuous pattern performed in this manner drastically reduces postoperative bleeding. (2)
Fig. 6: The first line of simple continuous suture is being placed.
Note the inside out direction of the suture bites (arrow). Include small bites of
the mucosa, tunica albuginea, and skin. ("3-bite" technique)
Fig. 7: Completion of one side of the closure.

Fig. 8: Completion of both sides of the urethrostomy
Avoid excessive manipulation of the urethral mucosa since it is friable and will bleed more with trauma.
Fig. 9: Appearance of a healed scrotal urethrostomy 2 weeks postoperatively.
Postoperative Care

Typical postoperative care after scrotal urethrostomy involves prevention of incisional trauma by using an Elizabethan collar on the dog, applying petroleum jelly around the incision to keep it moist and clean, close monitoring of the incision for swelling or bruising, and general supportive care (e.g., analgesics). Light sedation with acepromazine (0.05 mg/kg, SQ or IM) can be helpful to reduce hemorrhage from the incision site which is the most common postoperative complication. Suture removal is not necessary when absorbable suture is used to close the urethrostomy. If persistent hemorrhage occurs (i.e., for several days after surgery), carefully re-assess the incision for areas where the mucosa has not properly healed to the skin.  Additional sutures in these areas to close the defect should alleviate the problem.

Postoperative urethral stricture, although a possible complication of urethral surgery, is uncommon in a well-performed scrotal urethrostomy. Stricture may occur due to chronic licking of the incision or poor apposition of the urethral mucosa to skin during closure. Treatment of stricture is to revise the urethrostomy and insure meticulous mucosa to skin closure.

References

1. Bilbrey SA, Birchard SJ, Smeak DD. Scrotal urethrostomy: A retrospective review of 38 dogs (1973 through 1988). J Am An Hosp Assoc 1991; 27: 560-564.

2. Newton JD, Smeak DD. Simple continuous closure of canine scrotal urethrostomy: Results in 20 cases. J Am An Hosp Assoc 1996; 32:531-534.

3. Collins RL, Birchard SJ, Chew DJ, Heuter KJ. Surgical treatment of urate calculi in Dalmatians: 38 cases (1980-1995). J Am Vet Med Assoc 1998; 213:833-838.