Introduction
Cystotomy is most commonly performed for retrieval of cystic calculi, with other indications including ureteral evaluation and biopsy/removal of masses. Several key principles should be followed when performing cystotomy in dogs and cats. For example, the urethra should be included in diagnostic imaging prior to surgery and should urethral calculi be present, they should be hydropulsed back into the urinary bladder. There is no reason to perform a dorsal cystotomy despite concerns for urine leakage and/or adhesion formation to a ventral cystotomy incision. A cystotomy incision should be closed using a simple continuous, appositional pattern with a monofilament short-acting suture with full-thickness bites of the bladder wall which will ensure the submucosa is captured. Inversion of the urinary bladder as a second layer is not required and contraindicated in cases where there is a thick bladder wall. Post-operative diagnostic imaging is a requirement of the procedure to ensure all calculi have been retrieved. Minimally-invasive surgical (MIS) techniques have recently been described for cystic calculi removal.
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Preoperative Preparation
A thorough pre-operative evaluation and patient stabilization is performed prior to undertaking surgery of the urogenital tract, especially in cases of urethral obstruction secondary to calculi. The vast majority of animals undergoing cystotomy are healthy and standard protocols for anesthesia will suffice. Caution should be exercised in patients with hyperkalemia and this should be addressed prior to induction of anesthesia If pre-operative radiographs (performed under general anesthesia) reveal urethral calculi, retropulsion into the urinary bladder must be performed and urethrotomy avoided. It is the authors’ experience that urethrotomy can be avoided in the vast majority of cases with urethral calculi by retropulsing them back into the urinary bladder. It is of paramount importance to perform retropulsion with the patient under general anesthesia (+/- epidural anesthesia) to allow for urethral relaxation. Briefly, an assistant should place a gloved finger per rectum and occlude the urethra. An appropriately sized urinary catheter is inserted and flushing commenced. As the assistant feels urethral dilation, the finger is removed from the urethra and the sudden jet of fluid allows for urethral calculi to eventually move into the bladder after several flushing cycles.
It is important to realize that, as stated previously, the vast majority of urethral calculi can be retropulsed into the urinary bladder avoiding the need for urethral surgery.
Once all calculi have been retropulsed into the urinary bladder (confirmed radiographically), the ventral abdomen is aseptically prepared for surgery. In female dogs and cats, it is ideal to place a urinary catheter (Foley) prior to surgery. In male dogs, the author recommends preparing the prepuce routinely and keeping the prepuce in the surgical field so that the surgeon is able to place the urinary catheter at the time of surgery in the operating room. This allows the surgeon the ability to perform retrohydropulsion several times at their discretion. If the prepuce is draped outside of the surgical field, a non-sterile assistant is required to perform retrohydropulsion and replacing the urinary catheter is challenging.
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Operative Procedure
A caudal laparotomy is performed; in male dogs the skin incision is created only to the lateral aspect of the prepuce (parapreputial – right hand side for a right-handed surgeon). As stated previously, the author routinely leaves the prepuce in the surgical field to facilitate retrograde lavage of the urethra and urinary bladder. Following preputial incision, subcutaneous dissection is performed to the body wall and the linea alba is visualized. Preputial blood vessels will be encountered during the preputial approach and these can be ligated or cauterized. Once the bladder is visualized, a stay suture is placed in the apex of the bladder using a monofilament suture. This is readily apparent as a small, circular, fibrous scar at the cranial aspect of the bladder. The bladder is then exteriorized from the abdomen and then packed off with laparotomy sponges. If operating as a solo surgeon, the stay suture can be attached to the surgical drapes to maintain cranial tension on the urinary bladder.
A ventral cystotomy is recommended as this location provides the best visualization of the trigonal region where calculi are often found and avoids iatrogenic damage to the ureteral openings and neurovascular supply which are located in the dorsal aspect of the urinary bladder. Previous research has shown that ventral cystotomy is not associated with an increased incidence of complications such as body wall adhesions and incisional failure resulting in uroabdomen.
Suction is extremely helpful and valuable in this procedure. The ventral ligament of the bladder attaches on the midline and is sharply detached from the body wall. This attachment can be used as a proposed location for cystotomy.
A stab incision is then made into the ventral aspect of the urinary bladder. Immediately following stab incision, the suction tip is inserted to empty the bladder of urine and prevent spillage into the abdomen. The cystotomy is then extended to the desired length using Metzenbaum scissors. Readily apparent calculi are retrieved using an atraumatic instrument (e.g., bladder spoon). In some cases, calculi are not readily apparent upon performing cystotomy. This can be a result of calculi falling into the proximal urethra when positioned for laparotomy and as the bladder is exteriorized. At this point the bladder is emptied of visible calculi.
In male dogs a urinary catheter is passed by the surgeon or assistant surgeon in a retrograde manner and flushing with sterile lavage fluid initiated. Additional stay sutures can be placed in the lateral and caudal aspects of the cystotomy incision to improve visualization especially if operating solo. These stay sutures can be connected to the surgical drapes to free the surgeon’s hands for performing lavage and retrieval of calculi. The suction tip is placed in the urinary bladder as suction is being performed to improve visualization by removing lavage fluid. Suction also helps prevent spillage of fluid into the abdomen. The urinary catheter is gradually advanced while flushing with saline and then withdrawn once its visible in the urinary bladder and the procedure repeated several times until the surgeon is confident calculi are not present within the lower urinary tract. The author will routinely perform retrograde flushing several times to be confident calculi are not present in the lower urinary tract.
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In female dogs and cats a urinary catheter is placed pre-operatively and gradually withdrawn (with concurrent lavage) by a non-sterile assistant. *This strategy can also be performed for male dogs, however, repeated lavage cannot be performed to ensure a calculi-free urinary tract if the prepuce is draped outside of the surgical field. In female dogs and cats, following retrograde lavage by a non-sterile assistant, normograde lavage can be performed by the surgeon. Normograde lavage should be performed cautiously in male dogs since if calculi are present, they can become lodged at the level of the os penis.
Prior to closure a crushed calculi or a mucosal biopsy should be obtained and submitted for bacterial culture and sensitivity. It is has previously been shown that antibiotics do not need to be withheld until after the bladder mucosal biopsy is obtained and, therefore, standard protocols for administration of perioperative antibiotic prophylaxis should be performed (within 60 minutes of surgical incision and re-dosed every 90 minutes for cefazolin).
Cystotomy Closure
Several strategies exist for cystotomy closure. The author usually performs a single layer, appositional closure with a monofilament, rapidly absorbable suture material (e.g., polyglecaprone 3-0). A clear advantage of a double layer inverting pattern has not been demonstrated in recent studies. In fact, a double layer inverting closure may be challenging to perform in bladders where marked thickening of the wall exists. In fact, in animals with a thickened bladder wall secondary to cystic calculi, the author believes a second inverting layer is contraindicated as this may result in additional trauma to the urinary bladder wall, compromising closure integrity. Full thickness bites of the urinary bladder wall should be taken in order to capture the submucosal layer (holding layer). Ideally, the mucosa is not captured so as to prevent suture exposure within the urinary bladder as this could be a potential for suture-associated calculi. However, it is very likely that exposed suture becomes epithelialized and it is more important to ensure the submucosa is captured during cystotomy closure. The urinary bladder is unique compared to other tissues in that 100% of bursting strength following cystotomy is achieved after 3 weeks. Post-operative radiographs should be performed in all cases to ensure complete calculi removal. Three-view radiographs should be performed including two lateral views with the limbs extended and flexed to ensure a complete view of the urethra. Should calculi be present on post-operative imaging it is much easier to return to surgery to remove retained calculi than to continue some type of medical management.
Post-Operative Management
In the authors’ institution patients are recovered on intravenous fluids overnight. Non-steroidal anti-inflammatory therapy (pending contraindications) is highly recommended for urogenital surgery. A urinary catheter is not maintained in most cases. Discharge of the patient is performed 24 h postoperatively. At that time the animal should be urinating normally and may or may not have hematuria present which the owner should be cautioned about. If the animal has not urinated or is straining to urinate this warrants diagnostic investigation as to the cause (e.g., uroabdomen, incomplete calculi removal).
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