Introduction

Perineal hernias in dogs and cats are caused by the failure of the muscular pelvic diaphragm, which results in a loss of support to the colorectal junction and rectum. It is most commonly reported in intact male dogs and is rare in cats, first reported in 1976.¹ When reported in cats, it has most frequently occurred in neutered males and females,² with constipation and tenesmus as common clinical presentations.^1–8 Perineal swelling is only reported 22% of the time, in contrast to dogs, in whom this is reported in 90–95% of cases.⁹ In a study with 40 cats, perineal hernias most commonly presented with a median age of onset of clinical signs of 9 yr and a range of 1–15 yr.⁹ The rectum or distal colon are the most commonly herniated organs.² Other structures that have been reported to herniate include abdominal contents, peritoneal fat, and the urinary bladder.^4–6,9 Twelve of the 55 reported cases (22%) of feline perineal hernias occurred following perineal urethrostomy surgery for feline urologic syndrome, which has caused speculation that excessive blunt dissection to manipulate the intrapelvic urethra may contribute to the pathogenesis.^3,9 In a case study reporting bladder retroflexion in a perineal hernia in a neutered male cat, the patient was concurrently diagnosed with cutaneous asthenia and a diaphragmatic hernia.⁷ Cutaneous asthesia is theorized as another condition associated with perineal hernias, as several reports have described nontraumatic diaphragmatic, perineal, and inguinal hernias in patients with cutaneous asthesia.⁷ Other theorized causes of perineal herniation in cats include megacolon, perineal masses, chronic fibrosing colitis, and trauma.⁹ There also may be some association between the development of perineal hernias and rectal prolapse, anal sac impaction, and inflammatory bowel disease in cats.⁹

Positive-contrast retrograde vaginourethrocystogram is a noninvasive, cost-effective, accessible study to facilitate the diagnosis of several canine conditions but is reported in only one other literature study in cats.¹⁰ Vaginography, however, has extensively been reported in the literature for the diagnosis of atresia ani in cats.^11,12 To the authors’ knowledge, a positive-contrast vaginourethrocystogram had not been used to diagnose a perineal hernia in a cat at the time of presentation of the patient in this study.

Informed consent was obtained from the owners of the pet described in this study, which was clinically managed according to contemporary standards of care.

Case Report

A female intact domestic shorthair was initially seen at 6 mo of age for an ovariohysterectomy, and an asymptomatic, intrapelvic bladder was diagnosed intraoperatively. No surgical intervention of the malpositioned bladder was performed at the time.

At 3 yr of age, the cat presented to the Kansas State University College of Veterinary Medicine with stranguria and constipation. A rectal examination could not be performed owing to the temperament of the patient. Abdominal radiographs were obtained, and a soft tissue mass caudal to the pelvis and ventral to the caudal vertebrae was noted. The primary differential was a retroflexed bladder. Healed left hemipelvic fractures and spondylosis at the lumbosacral junction were also documented. The images of this radiographic study are not available at this time. According to the owner, there was no known history of trauma since or before the cat’s adoption at 6 mo of age. An exploratory laparotomy was performed confirming that the bladder was malpositioned in a right perineal hernia. On surgical examination, pelvic canal stenosis was reported, which necessitated resection of the cranioventral pubis, after bisection of the inguinal musculature, for improved surgical access to the retroflexed bladder. Due to adhesions and the pelvic canal stenosis, the bladder was only able to be manipulated to the cranial rim of the pelvis. The inguinal muscles were reattached by using a series of simple interrupted sutures using 2-0 Proline. The cystopexy was performed by attaching the bladder to the inguinal musculature and linea alba with a series of simple interrupted sutures using 3-0 Proline. The resected cranial pubic bone was not replaced owing to the new location of the bladder. The cat reportedly had no clinical signs related to the urinary tract system, with only occasional bouts of intermittent fecal incontinence over a 6 yr period.

At 9 yr of age, the cat presented to an emergency hospital for stranguria and tenesmus. Cystitis and constipation were suspected, and she was treated with dexamethasone sodium phosphate^a subcutaneously at 0.25 mg/kg and a 7-day course of amoxicillin trihydrate/clavulanate potassium^b at 13.5 mg/kg per os. Her owners also gave the cat Lax-Aire (cod liver oil) one to two times a day orally for 4 days. The cat returned to her normal urinating habits with no further straining noted. Eleven days later, she returned to her referral veterinarian because of continued tenesmus. Radiographs revealed a suspected bladder located in the right perineal region, containing a cluster of multiple round, well-marginated mineral opacities. At the time, blood work was unremarkable (WBC = 5.53 K/µL [reference interval [RI] = 5.50–19.50], hematocrit = 44.9% [RI = 30.0–45.0], blood urea nitrogen [BUN] = 26 mg/dL [RI = 16–36], creatinine [Creat] = 1.6 mg/dL [RI = 0.8–2.4]), and the cat was then referred to Kansas State University for further evaluation.

On presentation to Kansas State University, the cat was quiet, alert, and euhydrated; temperature was 38.2°C (100.8°F), heart rate was 180 beats/min, and respiratory rate was 36 breaths/min. She had a small, soft, fluctuant bulge to the right of her anus. Abdominal palpation was within normal limits. No other significant findings on physical examination were noted. According to the owner, she was urinating normally at the time. She was monitored overnight in the intensive care unit for evidence of urinary obstruction. No IV fluids were initiated owing to clinical euhydration. She urinated normally overnight with no concerns.

The following day, ventrodorsal and lateral radiographs of the pelvis were acquired using a Philips Bucky Diagnostic TH X-ray machine (Figure 1). The radiographs revealed multiple similarly sized, well-marginated mineral opacities within the right perineal area. The left pubic bone was not present; however, smooth solid bone extending from the pubic symphysis along the cranial and ventral margin of the ischial arch was noted. The colon was moderately filled with formed fecal material, and a bladder silhouette was not noted in the typical location in the caudoventral abdominal cavity. The appearance of the pelvis was consistent with the previous history of pubic ostectomy and suspected pelvic fractures. The location of the mineral opacities, as well as the lack of visualized bladder in the abdomen, was consistent with a right-sided perineal hernia containing a retroflexed bladder and cystic calculi.

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Following survey radiographs, the patient underwent general anesthesia for a positive-contrast vaginourethrocystogram using 0.02 mg/kg acepromazine maleate^c IV and 0.01 mg/kg buprenorphine^d IV for premedication and 10 mg/kg thiopental sodium^e IV for induction. The study was performed by instilling 15 mL of 50% Iohexol solution, diluted with saline, through a Foley catheter positioned in the vulvar opening. This procedure is performed by inserting a Foley catheter into the vestibule, where contrast medium is injected slowly. The contrast fills the vagina, and due to increased pressure with continued injection, there is retrograde filling of the urethra.¹³ In this patient, contrast was noted in the retroflexed bladder residing in the right perineal region, urethra, vagina, and vestibule. Luminal filling defects, consistent with previously noted cystoliths, were seen to freely move within the lumen during contrast instillation (Supplementary Video I).

The cat was taken to surgery the same day for a cystopexy and cystolithotomy. She was maintained on IV lactated Ringer’s solution fluids at 4 mL/kg/hr during the procedure. Multiple adhesions connected the omentum to the body wall and continued caudally into the pelvic canal including adhesions of the urinary bladder, consistent with a previous cystopexy. Adhesions were broken down and the bladder was retracted into the cranial portion of the pelvic canal. Fifteen calculi were recovered from the bladder, later identified as calcium oxalate calculi. A 5-French red rubber catheter was placed normograde through the bladder and into the urethra, which was flushed with sterile saline. A 6-French Foley catheter was placed retrograde through the urethra and the balloon filled with 2.5 mL of saline to facilitate placement in the bladder. The apex and portions of the dorsal and ventral aspects of the bladder were resected owing to questionable viability. A bacterial culture of the bladder mucosa was obtained, and the results later returned with no bacterial growth. The bladder incision was closed in a single layer using 4-0 Monocryl with a simple interrupted pattern. The bladder was leak tested with sterile saline. A repeat cystopexy was performed by scarifying the bladder serosa and suturing it to the transverse abdominus muscle of the right body wall at the level of the cranial pelvic canal. Four simple interrupted sutures using 3-0 Proline were used for the cystopexy. Anesthetic complications included moderate hypotension that improved with the addition of a dopamine constant rate infusion (CRI).

Postoperatively, pain management, IV fluids, and perioperative antibiotic therapy were initiated. The urinary catheter had been flowing well until the patient had expelled it ∼3 hr after placement during surgery. Afterward, she was seen to urinate a moderate amount in her litterbox with no evidence of straining; therefore, a new urinary catheter was not replaced. Approximately 28 hr following surgery, she was seen to excessively posture in her litterbox and seemed uncomfortable, prompting an increase in the fentanyl citrate^f CRI. Additionally, lactulose^g (0.25 mL/kg per os q 12 hr) was started because of concern for tenesmus, as she had continued to urinate normal amounts in her litterbox.

Two days after the cystopexy, she was taken back to surgery for a bilateral perineal hernia repair using the internal obturator muscle transposition flap technique.¹⁴ For premedication, she was given diazepam^h 0.2 mg/kg IV and continued on her fentanyl CRI at 2 mcg/kg/hr, and she was induced with the same 10 mg/kg IV dose of thiopental IV as her previous surgery. Throughout the surgical procedure, she was maintained on IV LRS fluids at 4 mL/kg/hr. Preoperative blood work was not obtained, as the patient had been continued on IV fluid administration and had been urinating normally. Postoperative blood work, however, revealed an azotemia (BUN = 80 mg/dL [RI = 16–35], Creat = 4.8 mg/dL [RI = 0.8–2.1]), hypoalbuminemia (albumin = 2.4 g/dL [RI = 3.2–4.7]), and elevated creatine kinase (creatine kinase = 15,147 U/L [RI = 153–572]). A postoperative abdominal ultrasound was performed and demonstrated bilateral proximal ureteroectasia (<0.36 cm), pyelectasia (<0.3 cm), and pelvic recess dilatation (<0.25 cm), consistent with diuresis, inflammation, or mild obstruction. There was mild peritoneal effusion consistent with recent surgery. No obstruction was noted, and after further hydration therapy, the cat was discharged 4 days postoperatively with an improved azotemia (BUN = 41 mg/dL [RI = 16–35], Creat = 1.6 mg/dL [RI = 0.8–2.1]).

The cat presented again 11 days postoperatively for tenesmus and constipation. On physical examination, the patient was painful on abdominal palpation. Mild, purulent discharge was noted at the surgical incision site; thus, two cutaneous staples were removed and the area was cleaned with diluted chlorhexidine. Abdominal radiographs were repeated, which revealed a small, subcutaneous, soft tissue opaque mass involving the caudoventral abdominal or inguinal soft tissues, visualized only on the lateral images, consistent with differentials of seroma, abscess, or cyst formation. The colon contained a moderate to severe amount of feces. No overt mineral opacities were visualized superimposed with the region of the urinary bladder, which was otherwise within normal limits. On ultrasound imaging at the time, mild ureterectasia and pyelectasis were noted but were improved from prior. The urinary bladder was partially identified dorsal to the pubic bone, being small in size. The subcutaneous tissues of the caudoventral abdominal wall were thickened, irregular, and heterogeneously mixed-echogenic, consistent with cellulitis. A well-defined, 1 cm in diameter, anechoic cyst-like structure was identified. The subcutaneous cyst-like structure was aspirated, which returned as possible reactive lymphoid hyperplasia, with the limitation of low cellularity samples. A bacterial culture swab of the purulent discharge from the incision site confirmed a bacterial infection. At this time, an additional urine culture was also performed, which returned negative for bacterial growth once again. The cat was discharged 5 days later, after being deobstipated, and was continued on oral antibiotics and lactulose. The owner was given instructions on how to properly monitor the infected incision site at home. The cat presented on recheck 20 days postoperatively, with the complaint of diarrhea. At that time, she had a regenerative anemia (hematocrit = 22%) and a normal leukogram. Her chemistry analysis was within normal limits with no evidence of azotemia (BUN = 10 mg/dL [RI = 16–35], Creat = 1.1 mg/dL [RI = 0.8–2.1]). Her incisional infection was documented as improving. The diarrhea resolved 2 days after antibiotics were discontinued, 6 wk after surgery. She was reported to have complete bowel movements with occasional stranguria. She was lost to further follow-up.

Discussion

Medical management of perineal hernias in cats has limited value as a sole method of treatment owing to a low success rate.² As a result, surgical management has been preferentially recommended over medical management.² The success rate for surgical correction is ∼73% in cats.⁹ The internal obturator muscle transposition flap has been found to be superior to traditional primary herniorrhaphy with a significantly lower recurrence rate in dogs.¹⁵ This method of repair has also been reported to be successful in cats⁹ and was chosen as the repair method for the cat in this report for this reason.

The female urethra in dogs and cats is shorter, wider, and entirely pelvic in position compared with males. In cats, the bladder is typically intra-abdominal and more cranial in position compared with dogs and thus may have a relatively long prepelvic urethra connecting the neck of the bladder to the pelvic urethra.¹³ In female cats, the urethra runs from the neck of the bladder to the external urethral orifice, which opens on the floor of the cranial vestibule in a urethral groove. In a normal dog, the urethra is not visible on radiographs because of surrounding soft tissue structures. Due to the more cranial position of the urinary bladder, the prepelvic urethra may be visible in normal cats, provided there is adequate surrounding fat.¹³ In male dogs and cats, retrograde urethrography is performed by inserting a catheter into the distal penile urethra, and a contrast medium is injected. However, this procedure can be challenging in female dogs and cats because of the relatively shorter urethra as well as difficulty facilitating a catheter into the urethral groove. Vaginourethrocystography is an alternate technique for evaluation of the lower urinary tract in both dogs and cats.

To the authors’ knowledge, this is the second reported case of retroflexion of the urinary bladder and perineal herniation subsequent to pelvic canal stenosis in a female cat.⁴ In both cases, the female cats had a pubic ostectomy performed to widen the functional canal and prevent further straining during elimination. The urethra lies on the pelvic floor and may be damaged during a pubic osteotomy. The pubis is part of the ventral support of the pelvic canal; thus, a pubic osteotomy may be a predisposing factor in the development of a perineal hernia. In literature, pelvic osteotomy has been previously described as treatment for obstipation for pelvic canal stenosis.¹⁶ Both cats were young adult animals at the time of presentation, and either congenital or acquired causes of pelvic canal stenosis should be considered when the patients present at such a young age. Retroflexion of the urinary bladder should be treated as an emergency, requiring stabilization of the patient and ultimately repositioning and fixation of the bladder. In this patient, the use of positive-contrast vaginourethrocystogram confirmed the survey radiographic suspicions of retroflexion of the urinary bladder despite a prior cystopexy, as well as the presence of cystic calculi. In recurrent cases with urinary signs and constipation or tenesmus such as in this case, the additional information provided by a positive contrast study should be considered.

It is speculative why the first cystopexy in this animal failed. However, the narrow pelvic canal and abundant adhesions prohibited the ability to secure the bladder into a more appropriate anatomical position initially. Cystopexies typically aim at positioning the bladder cranially into the abdomen without excessive tension. Unfortunately, the bladder in this cat could only be manipulated into the cranial rim of the pelvis at the time of surgery. This likely contributed to the insufficient securement of the bladder into normal positioning. Moreover, by appropriately fixating the bladder within the abdominal cavity, the trigone and proximal urethra are exposed to the intra-abdominal pressure, which equalizes the pressure between the bladder and its outflow tract.¹⁷ However, in dogs, if the bladder is in a caudally displaced or intrapelvic position, the abdominal pressure only acts on the cranial portion of the bladder and forces urine out of the short urethra, resulting in urine leakage, discomfort, or other abnormal urinary behavior.¹⁷ It is possible this may have contributed to the patient’s clinical symptoms of dysuria when she returned to Kansas State University several years after her cystopexy.

Lastly, it is unknown why the patient developed postoperative azotemia after the herniorrhaphy. Before expulsion, her urinary catheter placed during her cystotomy/cystopexy procedure had been flowing well. She continued to urinate normally without a urinary catheter. Thus, preoperative blood work was not performed before her herniorrhaphy, although it may have proved to be useful in retrospect. As the patient had little evidence for postrenal azotemia from obstruction, other differentials for the azotemia must be considered. This includes pyelonephritis, inflammation, or an acute kidney injury secondary to hypotension from anesthesia or from the use of a nonsteroidal anti-inflammatory medication. For example, acepromazine, which was used for premedication in the initial cystotomy/cystopexy procedure, is a phenothiazine derivative that causes arterial hypotension via vasodilation. Subsequently, this hypotension may cause systemic blood pressure to decrease below the range of renal autoregulation, which can result in high intraglomerular capillary pressure and ongoing renal injury. Anesthetic complications for the patient during her first surgical procedure in which acepromazine was used included mild to moderate hypotension, which improved with the addition of vasopressor agents. Additionally, the patient had two bacterial urine cultures performed, one intraoperatively and the other 11 days postoperatively. Both cultures were negative for bacterial growth; however, it has been documented that bacterial urine cultures, although more sensitive than urinalysis, can be negative in up to 21% of cases of pyelonephritis.¹⁸ Possible theories for the lack of bacteriuria in dogs with pyelonephritis include previous or concurrent administration of antimicrobial drugs, host of defense mechanisms with bacteria being walled off in the kidney, and bacterial adherence to the urothelium without shedding.¹⁸ Fortunately, her azotemia had resolved before discharge, and her renal values had continued to improve at her most recent laboratory work recheck.

Conclusion

Perineal hernias are uncommon in cats, and even more rare in female cats, with the vast majority of reported cases presenting with constipation and tenesmus in either sex. A perineal soft tissue swelling is an uncommon presentation, in contrast to dogs. Pelvic canal stenosis should be excluded as a possible perpetuating factor in the development of a perineal hernia. In feline patients, herniated structures often include the terminal colon and rectum. Retroflexion of the bladder into the perineal hernia is reported episodically in cats and should be considered in cats that have both stranguria and constipation or tenesmus. A positive-contrast retrograde vaginourethrocystogram is a noninvasive, cost-effective, readily available procedure that can be performed at the same time as survey radiographs and should be considered in the diagnosis of feline perineal hernias to exclude bladder retroflexion and to facilitate surgical planning. Medical management of perineal hernias in cats has proved to be less useful than previously expected, indicating that corrective surgery should be considered the standard of treatment.