Urinary bladder herniation through a caudoventral abdominal wall defect in a mature cat

Abstract

A 16-year-old spayed female domestic shorthair cat with no history of trauma was presented to the Western College of Veterinary Medicine for assessment of urinary incontinence. Diagnostic investigation revealed herniation of the urinary bladder through a caudoventral abdominal wall defect. Clinical signs resolved after surgical reduction of the bladder.

Introduction

Perineal and inguinal herniation of the urinary bladder both occur in the cat (1,2). Rupture of an umbilical hernia and subsequent bladder herniation have also been reported in humans (3). Umbilical rupture with bladder herniation is not a reported phenomenon in the veterinary literature. Rupture of the prepubic tendon is also commonly associated with herniation of the urinary bladder from the caudal abdominal cavity in cats (4). This report describes herniation of the urinary bladder through a caudal ventral abdominal wall defect of unknown etiology.

Case description

A 16-year-old spayed female domestic shorthair cat was presented to the Veterinary Medical Centre (VMC) at the Western College of Veterinary Medicine for assessment because of a 1-month history of urinary incontinence. The cat had reportedly been displaying episodes of urinary incontinence throughout this period but was also actively using her litterbox. She had a longer history of intermittent inappropriate defecation for the past 2 to 3 years as well as a 2-year history of progressive weight loss. The owner did not report any perceived stranguria, tenesmus or any swelling associated with the ventral abdominal wall. There was no evidence of hematuria or pyuria and the cat had no history of urinary incontinence prior to the previous month. She was treated by a veterinarian with a 14-day course of amoxicillin-clavulanic acid, PO, q12h at an unknown dose. There was no resolution in her clinical signs.

The cat had an ovariohysterectomy performed at 6 mo of age by a senior veterinary student and there were no reported complications at the time of surgery. A ventral midline approach was used but the length of the incision was not recorded. The cat had not undergone any other surgical procedures. Her vaccinations were performed yearly. The cat was presented 13 mo prior to the described visit for urinary incontinence. No abdominal wall defect or hernia was palpated and a serum biochemistry, complete blood (cell) count (CBC), urinalysis, and total thyroxine were performed. Her urine specific gravity was 1.022 but she was not azotemic. The results were otherwise unremarkable. The cat was allowed outdoors intermittently and was observed at all times during these periods. She was otherwise housed indoors.

Our physical examination revealed that the cat had a large soft mass associated with the caudoventral abdominal wall. She had a body condition score of 3/9, and weighed 3.3 kg. She had grade I/IV dental disease, a grade II/VI left parasternal systolic heart murmur, mild bilateral wheezes on pulmonary auscultation, and slightly small kidneys bilaterally on abdominal palpation. Her examination was otherwise unremarkable.

Given the physical examination findings, a focused preliminary abdominal ultrasound was performed. This revealed an extra-abdominal fluid-filled cavity with a thin wall occupying the entire area of swelling and deep within this there was a smaller, intra-abdominal fluid-filled structure. No communication could be visualized between the structures. An aspirate of each of the extra-abdominal and intra-abdominal fluid-filled structures revealed a light yellow, serous fluid. The specific gravity of each of these fluids was 1.017. On suspicion that both structures contained urine, a creatinine measurement was performed on each of the fluids. The extra-abdominal fluid had a creatinine reading of 11 402 μmol/L and the intra-abdominal fluid had a reading of 11 335 μmol/L, confirming the diagnosis that these fluids were both urine. Results of a CBC, serum biochemistry and urinalysis were largely unremarkable apart from the poor concentration of the urine, which was a persistent finding from a urinalysis performed 13 mo prior to this presentation. No bacteria were seen in the urinary sediment and urine culture was not done, which would have been ideal to rule out a urinary tract infection.

The cat was sedated and a pre-contrast radiograph was performed (Figure 1). The urethra was catheterized and another pre-contrast lateral abdominal radiograph showed placement of the catheter into the intra-abdominal component of the urinary bladder. Iohexol (15 mL Omnipaque 240 mg/mL; GE Healthcare, Mississauga, Ontario) was then instilled into the urinary bladder and a post-contrast radiograph showed that a small amount of contrast material had diffused into the extra-abdominal component of the urinary bladder. A circular gas opacity was also visualized in the extra-abdominal component which was likely secondary to the contrast material and a small amount of air being instilled when the cat was in dorsal recumbency, with gas rising into the herniated portion of the bladder (Figure 2).

Figure 1.

Plain right lateral abdominal radiograph. Notice the absence of intra-abdominal bladder and circular soft tissue opacity caudoventrally.

Figure 2.

Contrast cystogram prior to complete reduction into the abdominal cavity. Note the air opacity in the herniated portion of the bladder (arrow), suggesting communication between the intra-abdominal and extra-abdominal components of the bladder.

The bladder was drained of both urine and contrast material. It refilled immediately with contrast. An additional lateral abdominal radiograph was taken and revealed that the bladder was now completely reduced into the abdominal cavity (Figure 3).

Figure 3.

Contrast right lateral cystogram post bladder drainage and subsequent contrast infusion. Notice now the complete reduction of the urinary bladder into the abdominal cavity.

Given that the bladder was now reduced, the owner elected to have the cat discharged for monitoring until such time that the cat’s clinical signs recurred. The cat remained continent in terms of both urination and defecation for 16 d before it again developed urinary incontinence and was returned for surgical intervention.

Prior to surgery, a urogenital ultrasound performed by a board-certified veterinary radiologist revealed that the intra-abdominal urinary bladder was moderately distended and herniated from the abdominal cavity ventrally. Although no specific defect in the abdominal wall could be found, the intra-abdominal and extra-abdominal components of the bladder appeared to be converging caudally. There was moderate thickening of the abdominal wall immediately cranial to the suspected defect area. The kidneys were normal in length and appearance (30.9 mm left and 32.1 mm right in a sagittal plane). The liver also had multiple anechoic structures within the parenchyma (5 to 7 mm in diameter). These were most consistent with hepatic cystadenoma although cystadenocarcinoma was considered as a differential diagnosis.

To help determine the location of the abdominal wall defect, 1 mL/kg Iohexol (Omnipaque 240 mg/mL, GE Healthcare) was instilled via ultrasonographic guidance into the peritoneal cavity. A series of abdominal peritoneographs were obtained but the specific origin of the defect was not determined with these projections (Figure 4).

Figure 4.

Right lateral peritoneogram.

Reduction of the bladder into the abdominal cavity was achieved through a caudal ventral midline incision. The defect was palpated in the caudal abdominal fascia. The caudal margin was demarcated by the cranial margin of the left ischium. The defect’s long axis was in a sagittal plane and was approximately 3 cm long. The defect was just to the left of the midline but the left inguinal ring was palpably separate. The defect was continuous with the linea alba axially. As such, the cranial margin of the defect was extended cranially to allow visualization of the caudal abdominal anatomy. The bladder was assessed to be viable and was reduced without complication. Four bone tunnels were drilled in the cranial pubis for passage of 3-0 Prolene that was used to appose the external rectus sheath to the cranial pubis in simple interrupted sutures. The remainder of the extended linea alba defect was closed with 3-0 PDS in a simple continuous pattern. The subcutaneous tissue and skin were closed routinely.

The cat recovered uneventfully and regained urinary continence immediately. She has retained her continence for 142 d from the time of submission and continues to have no lower urinary tract signs.

Discussion

This report describes herniation of the urinary bladder through a caudoventral abdominal wall defect. Whilst reports of urinary bladder herniation through various abdominal wall defects have previously been described in the cat (5), to our knowledge the location of this defect in a cat with no known history of trauma, is a novel presentation. The location of the abdominal wall defect in this cat was associated with the linea alba axially, and was elliptical in shape with the long axis located in a craniocaudal orientation. The defect was just to the left of the midline and associated caudally with the cranial border of the left pecten of the pubic bone. The left and right inguinal canals were visualized and distinct from the defect.

The location of this defect was not consistent with any previously described congenital ventral defects, nor was it consistent with a complete rupture of the prepubic tendon. As such, there were several differentials to be considered for the etiology of the defect.

Given that there was no history of trauma, an incisional hernia, as described commonly in both the veterinary and human literature, was also considered a possible cause for the defect in this case. Incisional hernias occur when an inherent weakness is created in tissue following a prior incision. A classification system for abdominal wall hernias has been developed in the human literature to help differentiate primary (congenital) hernias from incisional hernias (6). Primary midline hernias by this system are classified as umbilical, or epigastric. There is no commonly described primary hernia of the caudal ventral midline and as such, a hernia in this region would be classified as an incisional hernia. Hernias of traumatic origin are also possible in this region (5).

In the veterinary literature, an acute incisional hernia is commonly referred to as dehiscence, but there are cases of late incisional hernias that have been described in the human literature; in 1 report occurring up to 12 y after surgery (7). There are no previous reports of incisional hernias occurring up to 15 y after surgery in veterinary or human patients, as would be true in this patient if this had resulted from her ovariohysterectomy incision. A chronic, incisional hernia which previously caused no clinical signs is also possible (8).

Whilst the defect was concluded to be idiopathic rather than a complete rupture of the prepubic tendon, the proximity of the caudal aspect of the defect to the pubic pecten meant that closure using the described technique, commonly used for pre-pubic tendon repair (8), would be most beneficial. Regardless of etiology, the location of the defect was the main determinant for the most appropriate repair method.

Herniation of the urinary bladder should be considered as a differential diagnosis in cats that display lower urinary tract signs and, whilst most commonly associated with trauma (5), cases with no history of trauma should be considered for less common defects such as chronic or late incisional hernias or inguinal hernias. Surgical correction can provide a rapid and effective solution if the problem is recognized. CVJ