Urinary surgery (Proceedings)

Cystotomy is a common surgical procedure in small animal surgery, most often performed for removal of uroliths. Surgery is indicated for stones that are not amenable to medical dissolution or those that are causing urinary obstruction.

Prior to cystotomy, stone retropulsion is sometimes required to move urethral stones into the urinary bladder. Under general anesthesia, the largest urinary catheter that can be placed is inserted until it abuts a urethral stone. Saline flush mixed with sterile lubricant is then flushed through the catheter with a fair degree of force. If the obstruction is not relieved, the proximal urethra can be occluded by a finger inserted in the rectum of the animal. The catheter is flushed, dilating the urethra. Pressure on the proximal urethra is then released letting the stone be flushed into the urinary bladder. A lateral abdominal radiograph should be performed prior to surgery to confirm that all stones have been dislodged from the urethra. The catheter is left in place as the animal goes to surgery to prevent stones from falling back into the urethra.

Following a routine caudal abdominal midline approach, the bladder is located and isolated from the rest of the abdomen with damp laparotomy sponges. Stay sutures are placed in the apex and neck of the bladder to facilitate cystotomy. A ventral incision in a relatively avascular area is typically performed to allow good visualization of the trigone and ureteral openings. A full-thickness sample of the bladder wall is taken for culture and histopathology. Calculi are removed from the bladder using forceps, spoon, or other smooth and blunt instruments. Don't forget to submit the stones for quantitative analysis in order to determine the need for postoperative medical management to prevent stone recurrence. A urethral catheter is passed several times both normograde and retrograde to make sure that no stones remain in the bladder neck or urethra. It has been reported that stones are left behind in 10-20% of cases following cystotomy.

The urinary bladder is unique in that it regains nearly 100% of its original tensile strength by 14 days. Therefore, synthetic absorbable suture material is most suitable for cystotomy closure. Monofilament suture is preferred as there is some concern that contact between urine and multifilament suture may lead to an increased rate of absorption or may promote urolith formation. Nonabsorbable suture and staples are contraindicated in urinary bladder closure as they are associated with the formation of urinary calculi.

There are a number of suture patterns that can be used to close the urinary bladder. The surgical goals are to minimize tissue trauma, create a watertight seal, and avoid promotion of calculi formation. Options for cystotomy closure include:

• Three-layer inverting continuous pattern

o Simple continuous pattern in mucosa only, followed by,

o Partial-thickness Cushing pattern followed by,

o Partial-thickness Lembert pattern

• Two-layer appositional continuous pattern

o Partial thickness simple continuous pattern followed by,

o Partial thickness Lembert pattern

• Two-layer inverting continuous pattern

o Partial-thickness Cushing pattern followed by,

o Partial-thickness Lembert pattern

• Single-layer simple interrupted pattern

• Single-layer simple continuous pattern

There is no difference in circular bursting wall tension of urinary bladders closed with single-layer simple interrupted appositional pattern versus a two-layer continuous inverting closure. Luminal compromise may occur if two-layer inverting patterns are used in urinary bladders with severely thickened walls. A three-layer closure can be used if there is excessive hemorrhage from the bladder mucosa. In this technique, the mucosa is closed as a separate layer in a simple continuous appositional pattern (which attenuates the bleeding), followed by a two-layer inverting pattern in the seromuscular layers.

The author typically performs a single-layer full-thickness simple continuous closure with 3-0 or 4-0 rapidly absorbable monofilament suture. Most surgical texts state that the lumen of the bladder should not be entered with suture material. Urinary calculi formation has been associated with multifilament absorbable suture, nonabsorbable suture, and metal staples, however there have been no studies assessing the lithogenic potential of the newer monofilament absorbable sutures. Full-thickness purchase of the bladder wall guarantees incorporation of the submucosal holding layer. Single layer partial-thickness closures of the urinary bladder that miss the submucosa may be inadequate for preventing urine leakage.

There is no special postoperative care required following cystotomy. Routine postoperative abdominal radiographs can be taken to confirm that all urethral and bladder stones have been removed. Owners should be warned to expect mild hematuria for 3 to 5 days postoperatively. Follow-up medical management should be based on results of stone analysis.

Suggested reading

Jens B, Bjorling DE. Suture selection for lower urinary tract surgery in small animals. Comp Contin Educ Pract Vet 2001;23:524-530.

Radasch RM, Merkeley DF, Wilson JW, et al. Cystotomy closure: A comparison of the strength of appositional and inverting suture patterns. Vet Surg 1990;19:283-238