Retrograde Urohydropropulsion

In patients with urethroliths, retrograde urohydropropulsion should be performed to flush the stones back into the urinary bladder to allow for cystotomy.⁶ This procedure is more successful under general anesthesia due to the full relaxation of the urethral musculature that anesthesia provides compared to sedation. If the urinary bladder is distended prior to starting this procedure, it should be drained either by passing a smaller urethral catheter around the stones or by use of decompressive cystocentesis. Male dogs should be placed in lateral recumbency following induction of general anesthesia. The penis is extruded and prepped with dilute chlorhexidine or povidone–iodine solution. A sterile catheter is placed retrograde into the urethra until the obstruction is reached. This catheter should be as large as possible to assist in flushing the stones. In a sterile bowl, 1 L of saline is mixed with sterile lubricant. In large dogs, a full 5 oz tube of sterile lubricant can be used. Since this may clog a smaller diameter urethral catheter, this volume may need to be adjusted based on patient and catheter size. A 60 cc syringe (or 20–35 cc syringe in smaller patients) is filled with this saline/lubricant solution and is attached to the urethral catheter. A second assistant places a finger in the rectum and pushes down firmly onto the pubic bone to occlude the urethra. The urethral catheter is flushed with the saline/lubricant mixture (it helps to pinch the tip of the penis around the catheter with a gauze to prevent backflow of the saline/lubricant solution). The person with their finger in the rectum should feel the urethra distend caudal to their finger; when this is felt, they should release the digital pressure against the pubis to allow the fluid and stones to pass into the urinary bladder while the person injecting the saline/lubricant mixture continues to inject (Figure 28.2). The palpable distension indicates that the urethra has been dilated to allow the stone to pass back up the urethra into the urinary bladder. This process should be repeated a few times, ensuring to keep an eye on the volume of the urinary bladder and draining it as needed. If an assistant is not available to perform the rectal portion of this procedure, passing a urethral catheter until it abuts the stone and then flushing through the catheter may dislodge the stone, allowing it to flow back into the urinary bladder. If the stone does not dislodge after a few attempts, true retrograde urohydropropulsion should be performed as described above. Once the urethral catheter passes smoothly, radiographs should be taken to confirm all of the urethral stones have moved into the urinary bladder (Figure 28.3). Although this procedure is most commonly performed in male dogs, it can also be performed in female dogs and male cats. In all patients, this should be performed carefully to avoid inadvertent trauma to the urethra from the catheter.

Patient Preparation and Positioning for Surgery

The patient should be positioned in dorsal recumbency and aseptically prepared and draped for surgery. In male dogs, the prepuce should be flushed with diluted povidone–iodine solution and the prepuce draped into the sterile field to allow for urethral catheterization. Male cats can be positioned with the pelvic limbs pulled cranially to allow for access to the penis for urethral catheterization; a towel can be placed under the caudal pelvis to increase exposure to the prepuce (Figure 28.4). In female dogs and cats, retrograde urethral catheterization is rarely necessary, but the vulva can be prepped and draped into the field, if necessary. It is recommended to drape the entire abdomen, even if the planned incision site is in the caudal abdomen over the bladder.

Surgical Approach

If the planned procedure is a cystotomy only, the abdominal incision may be just large enough to exteriorize the urinary bladder. The incision should be made directly over the palpable urinary bladder. If the urinary bladder is not palpable, the incision should be made 3–4 cm cranial to the pubis. In male dogs, the incision should be made parapreputially through the skin and subcutaneous tissues (Figure 28.5a). The prepuce and penis should then be retracted laterally and the linea alba opened on ventral midline. In female dogs and all cats, the incision should be made through the skin and subcutaneous tissues on the ventral midline, allowing for entry into the abdomen through the linea alba (Figure 28.5b). Once the abdomen is opened, the urinary bladder should be exteriorized (Video 28.1). There is often a large amount of fat in the caudal abdomen, and a distended bladder can make exteriorization difficult. If the urinary bladder is unable to be exteriorized, urine can be drained via retrograde catheterization or cystocentesis, or the abdominal incision can be extended.

Cystotomy

Once the urinary bladder has been exteriorized, it should be packed off with moistened laparotomy sponges to reduce the amount of contact with the skin (Figure 28.6, Video 28.2). The urinary bladder has three attachments to the abdominal wall (Figure 28.7). The ventral median ligament attaches the bladder ventrally to the linea alba and pelvic symphysis. In some patients, this fragile ligament may not be visible or may have been disrupted during extension of the linea incision or exteriorization of the urinary bladder. There are also paired lateral ligaments that contain fat, the distal ureters, and the umbilical arteries. A stay suture should be placed into the apex to assist with maintaining exteriorization of the urinary bladder. If the bladder wall is friable, a cruciate suture can be placed instead of a simple interrupted suture to provide more holding power on the stay suture.

The cystotomy incision should be performed on the ventral (uppermost) surface of the urinary bladder near the apex in an area of low vascularity. If the ventral median ligament is not already disrupted, it can be transected near the urinary bladder serosa to allow for better identification of the ventral surface of the urinary bladder. Although proposed benefits of a dorsal cystotomy are reduced risk of urine leakage due to gravity, reduced formation of adhesions to the body wall, and reduced formation of cystoliths due to gravity‐dependent sedimentation separating the sediment from sutures, the need for these factors has been refuted in two studies.^7,8 Performing a cystotomy on the dorsal surface of the bladder increases the risk of damage to the ureters and neurovascular bundle (Figure 28.8). Cystotomies performed on the ventral surface are easier to perform, allow for a better view of the ureteral openings, and allow for easier access to the urethra.

Once the planned incision site is identified on the ventral surface of the urinary bladder, lateral stay sutures should be placed on either side, within 1 cm of the planned incision site (Figure 28.9, Video 28.3). Prior to incising the urinary bladder, ensure it is packed off with moistened laparotomy sponges, and have suction ready to evacuate expelled urine from the surgical site (Figure 28.10). A stab incision should be performed with a #11 or #15 blade between the stay sutures (Video 28.4). It helps to announce “you’re in (urine)” at this point (personal communication, Harry Boothe). The incision should be just long enough to allow for use of the bladder spoon or for removal of the calculi, whichever is larger. In cases with numerous small stones, the incision may only be 1 cm in length (Figure 28.11), whereas larger stones may require a larger cystotomy incision. Some surgeons prefer to make the cystotomy incision just large enough to allow for them to pass their index finger into the urinary bladder to palpate for stones. The cystotomy incision may need to be extended with the scalpel blade or Metzenbaum scissors in cases of significant urinary bladder debris (e.g., feline idiopathic cystitis), neoplasia, or a need to inspect the mucosal surface (Video 28.4). Care should be taken when nearing the trigone to ensure the ureters are identified and avoided, and this can be done by keeping the incision on ventral midline closer to the apex of the urinary bladder.

A human gallbladder spoon can be used to scoop stones out of the urinary bladder (Figure 28.12, Video 28.5). The spoon is inserted through the incision into the trigone, spun 360°, and then removed. Any retrieved stones should be collected into a sterile bowl or cup. The gallbladder spoon is used until no stones are retrieved after several attempts while attempting to insert the spoon as far as possible each time. The spoon can typically be inserted to the level of the finger grip between the two ends in most cases. If there was a countable number of stones on preoperative radiographs, removed stones are counted to determine if any stones remain, although in many cases, the stones are too numerous to count or superimposition on radiographs makes counting difficult. The urethra should be catheterized retrograde into the bladder in male dogs and also in male cats if the prepuce was draped into the surgical field (Figure 28.13). The catheter is then slowly withdrawn into the urethra, and sterile saline is flushed into the catheter to flush any stones in the urethra into the urinary bladder. The gallbladder spoon is then used to sweep the trigone area and remove any flushed stones. Some clinicians may also use digital palpation with an index finger to palpate within the lumen for any residual stones. Sweeping for stones should be repeated numerous times, until no more stones are retrieved, and retrograde passing of the catheter feels smooth. The catheter may also be passed normograde through the cystotomy incision to ensure smooth passage (Figure 28.14). The catheter should be withdrawn until it is in the proximal urethra and then should be flushed to ensure an adequate urine stream is appreciated from the tip of the penis. In general, having three retrograde and three normograde catheterizations in which the catheter passes smoothly and no stones or mineralized debris are identified with flushing is an indication that all stones/debris have been removed and the cystotomy incision can be closed. In female dogs and cats, these steps are rarely necessary. Female cats can be retrograde catheterized relatively easy, but female dogs are difficult to retrograde catheterize. Fortunately, the female canine urethra is large enough that stones rarely lodge here, and the gallbladder spoon can often be passed fairly far down the urethra to scoop any possible stones. The bladder can also be externally digitally palpated for stones as another method to ensure complete removal, although this may be less fruitful in cases with cystitis.

Prior to closure, a small portion of urinary bladder mucosa should be excised with Metzenbaum scissors for aerobic culture and susceptibility. Submission of a stone for culture analysis can also be performed;⁹ however, some clinicians feel this may not reflect an active infection as compared to urinary bladder mucosa. Use of perioperative antimicrobials does not affect culture results from samples obtained intraoperatively.¹⁰

Cystotomy closure is performed with monofilament absorbable suture, such as poliglecaprone 25 or polydioxanone, on a taper needle. The urinary bladder heals quickly with 100% strength in 14–21 days;¹¹ thus, long‐lasting suture is not required. Suture size is dependent upon the patient. Recommended suture sizes are 3‐0 or 4‐0 suture in small dogs and cats and 3‐0 suture in larger dogs. In patients with cystitis, one suture size larger than normal may be chosen. The cystotomy incision may be closed with a single‐layer appositional pattern. In cases in which a short cystotomy incision was performed, a simple interrupted pattern should be used (Figure 28.15). If a longer cystotomy incision is performed, a simple continuous pattern is preferred. There is no difference in the major or minor complication rate between cystotomies closed with a single‐layer appositional pattern or a double‐layer inverting pattern.¹² If a double‐layer closure is performed, two layers of simple continuous sutures may be preferred due to the risk of focal cystitis with an inverting pattern.¹³ Suture bites should be placed evenly every 3 mm, with bites taken 3 mm back from the cut tissue edge. Sutures should be pulled snug but not strangulating or hard enough to pull through the tissues, and with a simple continuous suture pattern, tension should remain consistent along the suture line. The holding layer of the urinary bladder is the submucosa; thus, full‐thickness bites through the urinary bladder wall are preferred to ensure capture of this layer. Although there is a concern for suture exposure within the lumen increasing the risk of stone formation, poliglecaprone 25 is completely absorbed in 90–120 days, and with snug apposition, little suture is exposed to the lumen.

A leak test of the cystotomy closure may be performed in male patients by retrograde urethral catheterization and distension with saline (Video 28.6). A leak test is not required, but if desired, may be performed in female patients via cystocentesis and distention with saline. If leakage is noted, simple interrupted sutures should be added to reinforce a simple interrupted suture line. Simple interrupted sutures can also be added on top of a leaking simple continuous line but should not be tied tight enough to make the simple continuous line even looser around the tight simple interrupted suture. Clinicians should be aware that looseness in one region of the simple continuous line may eventually move to a different area or settle out across the entire suture line, leading to leakage. The urinary bladder should be evacuated of urine/saline prior to closure, and any urethral catheters should be removed. Local lavage should be performed (Video 28.7), and the urinary bladder should be returned to the abdomen (Video 28.8). If omentum is visible through the body wall incision, it may be placed over the cystotomy incision; if it is not visible, this is not a concern as the omentum will adhere itself even if not directly placed in the area. The abdominal wall incision is then closed in three layers (external rectus sheath, subcutaneous tissues, skin).

Immediately postoperatively, radiographs should be taken for patients with radiopaque stones to ensure complete removal. In one study, 20% (9 of 44) of dogs had incomplete urolith removal following cystotomy, emphasizing the importance of performing postoperative imaging to confirm complete removal of all stones.¹⁴ If a residual stone(s) is/are noted, the patient should be returned to surgery and the incision reopened to complete stone removal. In patients with radiolucent stones, ultrasound may be used to determine if stone removal is complete. Excised stones should be submitted for stone analysis to assist with diet alterations or other therapies to reduce the recurrence of stone formation.

Partial Cystectomy

Partial cystectomy is performed for masses or other urinary bladder wall defects. Most urinary bladder masses are nonresectable due to their preference for the trigonal region where the ureters enter and the urethra exits. However, lesions located at the apex, ventral wall, or dorsal wall away from the ureters and urethra may be excised with partial cystectomy. Urothelial carcinoma is known to seed easily, meaning that exposure of the abdomen or abdominal incision to cells from this tumor increases the likelihood of additional tumors growing in those locations. For this reason, if a mass is known to be at the apex of the urinary bladder, excision without opening the urinary bladder may be considered.¹⁵ In other cases, the presence of a mass or lesion that requires excision may not be known until the urinary bladder is opened. In these cases, a larger cystotomy incision may be made on the ventral surface of the bladder to allow for inspection of the mucosa. In some cases, the urinary bladder can be everted to allow for increased visibility of the dorsal mucosal surface (Figure 28.16). Once a lesion has been identified that requires excision, a stab incision should be made with a #11 or #15 scalpel blade full thickness through the urinary bladder wall. This incision may be continued with the scalpel blade or with Metzenbaum or Mayo scissors, depending on the thickness of the urinary bladder wall. For tumors, gross margins of 1 cm are excised, but the available margin may be smaller depending on the proximity of the lesion to the ureteral papillae, which should be assessed via catheterization of the ureters at the ureterovesicular junctions to identify their location. In some lesions with wall necrosis, a line of demarcation may be seen (Figure 28.16), but if not immediately visible, it is important to resect back to healthy, bleeding tissue. Once the resection has been performed, the incision is sutured as described for cystotomy above. Placing small catheters into the ureteral papillae, if not already in place, helps with identifying these structures to avoid accidentally suturing them or impinging upon them during closure.