Stephen J. Birchard DVM, MS, Diplomate ACVS

Monday, February 23, 2015

Polypoid Cystitis in Dogs: Not all bladder masses are cancer!

Stephen J. Birchard, DVM, DACVS
Scott Owens, DVM, DACVIM

Polypoid cystitis is a disorder of the urinary bladder in dogs characterized by inflammation and development of one or more polypoid masses within the bladder lumen. (Fig. 1) 
Fig. 1: Pedunculated urinary bladder polyps in a dog
Most affected dogs are female and present with a history of hematuria or recurrent urinary tract infection (UTI).(1) Several different species of bacteria have been cultured from the urine of affected dogs with Proteus spp. being the most common.(1) Polyps tend to be located cranioventrally in the bladder as opposed to transitional cell carcinoma which tends to occur in the bladder neck or trigone area. (Fig. 2)
Fig. 2: Large polyp located in the cranial aspect of the urinary bladder
It is unknown whether persistent or recurrent UTI predisposes to polyp formation or if polyps predispose to UTI. In one study, 7 of 17 dogs with polypoid cystitis also has cystic calculi.(1) Effective treatment combines surgical resection of the polyps combined with medical management of the cystitis. Surgical removal of the polyps is straightforward if just one or a few polyps are found, especially if the polyps are pedunculated and not located near the trigone. Widespread polyps are more difficult to surgically resect, and may require subtotal submucosal resection of the bladder mucosa.(2) (Fig. 3)
Fig. 3: Diffuse small mucosal polyps in a dog.
Alternatively, use of a Holmium:YAG laser via cystoscopy may be an effective minimally invasive method of treatment for patients with low numbers of polyps.(3)

The diagnosis of polypoid cystitis is straightforward in most cases.  Clinical suspicion should be raised in patients with signs of lower urinary tract disease, including pollakiuria, hematuria, and stranguria non-responsive to initial therapy.  Urinalysis results are non-specific, with microscopic hematuria seen in most cases along with bacteriuria and pyuria, the former if an active infection is present.  Orthogonal view abdominal radiographs are helpful to rule out urolithiasis, while characteristic polypoid structures are most commonly seen via ultrasound of the urinary bladder.(Fig. 4)
Fig. 4: Ultrasound appearance of a pedunculated bladder polyp (arrow) in a dog with polypoid cystitis
In the absence of ultrasound availability, double-contrast cystography may be used.  Confirmation can be made via cystoscopy (Fig. 5) or cystotomy (see below).   
Fig. 5: Cystoscopic appearance of bladder polyps in same dog as in Fig. 4.

Surgical Technique

Perform a ventral midline abdominal approach. After routine exploratory, exteriorize the urinary bladder and isolate it from the peritoneal cavity with moistened abdominal sponges.  Carefully examine the bladder; if the polyp can be palpated and its point of attachment to the bladder wall determined, make an initial cystotomy adjacent to this area. (Fig. 6) 
Fig. 6: Large bladder polyp in a dog; cystotomy incision has been made
adjacent to the mass to facilitate resection and closure.
In this way the entire polyp can be removed by partial cystectomy without making an additional incision in the bladder. If the polyp cannot be palpated, or there are multiple polyps present, simply make a routine ventral cytstotomy incision to expose the polyps. Small pedunculated polyps can be removed by submucosal resection at their attachment to the bladder. Large polyps with wide mucosal attachment should be removed by partial cystectomy. (Fig. 7)
Fig. 7: Excised polyp (P) and full thickness section of urinary bladder (B)

Prior to bladder closure, obtain a sample of mucosa for culture. Also be sure to submit all resected tissues for histopathology. Close the bladder routinely (see Veterinary Key Points blog from 10/11/2014 entitled: Cystotomy for Removal of Cystic and Urethral Calculi in Dogs: Are you getting them ALL out?).

Postoperative Care
Routine care after cystotomy includes intravenous fluid therapy, analgesics such as opioids and/or NSAIDS (if renal function is normal), and antibiotics if indicated. Monitor urinations as well as vital signs. Most animals can be discharged from the hospital the day after surgery.  Post-operative hematuria should be expected, and if severe the pet owner should be made aware to monitor for urinary obstruction due to blood clot formation.

Long-term postoperative care depends on results of histopathology and culture. If polypoid cystitis is confirmed and cultures are positive, appropriate antibiotics are prescribed for at least 3 weeks, followed by repeat culture after being off of antibiotics for several days. NSAIDS, including piroxicam, may be beneficial to reduce inflammation and thereby prevent formation of more polyps.  While this condition is scarcely reported in the veterinary literature, surgical removal as described above has a very high long-term success rate.  Medical management alone is unlikely to be successful. Partial resolution of clinical signs may be achievable, but long-term success is unlikely without surgical intervention.

1. Martinez I, Mattoon JS, Eaton KA, Polypoid cystitis in 17 dogs (1978–2001). J Vet Intern Med 2003;17:499–509

2. Wolfe TM, Hostutler RA, Chew DJ, Surgical management of diffuse polypoid cystitis using submucosal resection in a dog. JAAHA: July/August 2010: 46(4):281-284.

3. Xu C, Zhang Z, Ye H et al.  Imaging diagnosis and endoscopic treatment for ureteral fibroepithelial polyp prolapsing into the bladder.  J XRay Sci Technol.  2013;21(3):393-9.