Positive-contrast cystography in a dog with a hard-to-detect bladder rupture

Positive-contrast cystography in a dog with a hard-to-detect bladder rupture

Be sure to look a little deeper when using this technique during your search for a ruptured bladder to prevent missing the diagnosis.

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A 10-month-old 6.7-kg spayed female Cavalier King Charles spaniel was presented to the Kansas State University Veterinary Health Center (KSU VHC) for evaluation after a vehicular trauma.

Initial diagnostic tests and treatment
Physical examination findings indicated cardiovascular shock with a low diastolic blood pressure, tachycardia, pale mucous membranes, hypothermia (97.4 F), no central neurologic dysfunction, mild hindlimb paresis, and a longitudinal abdominal laceration that did not penetrate the abdomen. A serum chemistry profile revealed that the dog was azotemic with elevated blood urea nitrogen (45 mg/dl; reference range = 10 to 28 mg/dl) and creatinine (2.03 mg/dl; reference range = 0.3 to 1.5 mg/dl) concentrations and hypoproteinemic (3.4 g/dl; reference range = 5.4 to 7.4 g/dl) and had an elevated lactate dehydrogenase activity (194 IU/L; reference range < 175 IU/L).

The dog was resuscitated with a 150-ml bolus of lactated Ringer’s solution followed by intravenous infusion of lactated Ringer’s solution (50 ml/hr throughout the night). Additional treatment included oxygen supplementation and administration of prednisolone (10 mg orally) and hydromorphone (0.3 mg intravenously). The skin laceration was closed with skin staples.

The dog remained hypothermic throughout the night of presentation, and frank blood was noted on the thermometer at both presentation and at the two-hour recheck, but this resolved overnight. Orthogonal abdominal radiographs were obtained.

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Radiographic findings
Numerous pelvic fractures were present, including a long axis fracture of the right ilial body with cranial and abaxial displacement, fractures of the right ischium caudal to the acetabulum with lateral displacement, and a fracture of the right acetabular branch of the pubis (Figures 1A & 1B). The abdomen appeared pendulous, and there was a loss of abdominal detail (worse in the right caudal and caudoventral abdomen), an inability to visualize the bladder, and streaking in the dorsal retroperitoneal area. Additionally, the renal margins were indistinct. Differential diagnoses for the loss of abdominal and dorsal retroperitoneal detail were hemorrhage, urine leakage, or peritonitis.

Figure 1A. A right lateral radiograph of the 10-month-old spayed female Cavalier King Charles spaniel evaluated in this case report. The streaking in the dorsal retroperitoneal area is indicated by the arrow.

Figure 1B. A ventrodorsal radiograph of the patient. The skin staples were from the abdominal laceration repair.

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Positive-contrast cystography: First attempt
Positive-contrast retrograde cystography was performed to assess bladder integrity because the urinary bladder was not visualized on survey films and because there were pelvic fractures, a loss of peritoneal serosal detail with streaking especially in the caudal retroperitoneal space, and azotemia consistent with a bladder rupture. A balloon catheter was placed within the urinary bladder neck, and the urinary bladder was distended with 14 ml of a positive contrast agent (Figure 2A). Contrast leakage was not seen.

Figure 2A. A lateral abdominal radiograph of the dog in this case taken after the initial administration of contrast.

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Positive-contrast cystography: Second attempt
Because a urinary bladder rupture was highly suspected, the catheter balloon was deflated and 9 ml of the contrast agent was administered again (Figure 2B). Contrast was visualized superimposed over the retroperitoneal area and in the area of the pelvic canal consistent with a ruptured bladder neck or proximal urethra. There was also contrast leakage in the caudal abdomen. Surgical exploration confirmed a bladder neck rupture that was surgically repaired and the dog recovered uneventfully.

Figure 2B. A lateral abdominal radiograph of the dog taken after the deflation and cranial displacement of the balloon catheter and the reinfusion of contrast.

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Discussion
Bladder rupture can occur from a variety of causes, including acute trauma, traumatic catheterization, iatrogenic overdistention, urethral obstruction, and necrotizing cystitis.1,2 The urinary bladder’s anatomic position depends on distention as well as the patient’s age and species. In dogs, most of the bladder, when empty, sits within the pelvic cavity. A normal cat urinary bladder is always intrabdominal and 2 or 3 cm cranial to the pubis.3

In dogs and cats, the peritoneum covers the urinary bladder body cranial to the ureteral entry to the trigone. In the trigone, the ureters go from retroperitoneal to intraperitoneal as they travel through the two layers of peritoneum that form the lateral ligament of the bladder.4 At the rectovesical pouch, the dorsal peritoneal reflection at the neck of the bladder communicates with the adventitial surface of the proximal portion of the urethra. The urethra in male dogs and cats is completely enveloped by the prostate gland within the retroperitoneal space ventrally and enters the retroperitoneal cavity just distal to the trigone in bitches or queens.5 Because of the anatomy and communication with multiple body spaces, a rupture at the neck of the bladder could lead to numerous contrast leakage combinations.

Positive-contrast cystography is the gold standard for confirming rupture of the bladder or the pelvic urethra after survey radiography displays a loss of abdominal serosal detail or retroperitoneal streaking.6 Other indications include clinical signs that indicate bladder rupture such as anuria, hematuria, or dysuria or patients in which the urinary bladder is not radiographically visible with or without an indistinct appearance of other abdominal structures.7 Urine accumulates in the posterior ventral abdomen immediately after a urinary bladder rupture and becomes more generalized throughout the abdomen within a few hours.3

It is recommended that a patient fast for 24 hours before performing positive-contrast cystography and that the patient be given an enema just before radiography, but this is neither feasible nor recommended in an acute trauma or unstable patient.8

Before catheter placement, the external genitalia should be cleaned. Sedation or light general anesthesia is suggested—but is often unnecessary—to facilitate catheter placement and reduce the likelihood of damage to the urinary tract mucosa.9 When placing the catheter, use a sterile lubricant and a radiopaque catheter. Many have an inflatable balloon end, although this can cause diagnostic complications, as noted below. To reduce nociceptive input, 2 to 5 ml of 2% lidocaine may be infused before the contrast medium, with lower doses being used for cats and smaller dogs and higher doses for larger-breed dogs.10 Only water-soluble, organic iodides should be used for retrograde cystography.6,11

Depending on the size and location of the laceration, there can be variations in the rate of contrast extravasation. Large or ventrally located lacerations are more likely to leak shortly after contrast administration than are dorsally located or small defects in a standing patient, so dorsally located or small defects may require more contrast agent volume, increased time between administration and imaging, or changes in positioning such as lateralization if patient stability and comorbidities (i.e. pelvic fractures) allow because leakage is passive and gravity dependent.

As was noted in this case, the balloon catheter must be deflated before an intact bladder can be confirmed because an inflated balloon at any position within the bladder can essentially seal off the defect and, thus, prevent leakage of contrast agent into the peritoneal or retroperitoneal spaces. Additionally, it is important to note that because of the anatomic positioning of the proximal urethra in the pelvic inlet, the catheter should be moved to prevent any sealing of a urethral tear and, subsequently, a misdiagnosis.

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In another case diagnosed and treated at the KSU VHC, a dog with a similar history of being hit by a car had positive-contrast cystography performed for a suspected ruptured bladder. After the contrast agent was administered, the balloon catheter was incompletely deflated and extended cranially to avoid sealing a potential defect at the bladder neck, which would have falsely indicated an intact bladder (Figure 3). This technique is advantageous not only because it moves the catheter away from the bladder neck to allow leakage from any rupture located in this area but also because it allows you to maintain a patent catheter if needed for additional diagnostic tests or therapies. Additionally, extravasation of contrast material from the urethra into pelvic, perineal, and upper pelvic limb tissues can be seen with urethral ruptures, as noted in this patient.9

Figure 3. The positive-contrast cystography technique performed in a dog evaluated at the KSU VHC.

(A) Dilate the balloon at the neck of the bladder and administer contrast.

(B) Deflate the balloon incompletely (dashed arrow).

(C) Cranially displace the balloon away from the neck of the bladder (solid arrow).

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Conclusion
When the loss of bladder integrity is suspected, especially in a patient with a history of trauma with or without clinical signs of anuria, hematuria, or a distended abdomen, positive-contrast cystography is the gold standard for a bladder rupture diagnosis. While a balloon catheter is recommended to ensure a patent passage of contrast agent, it can occlude any defect, especially lacerations of the bladder wall, resulting in a false negative reading.12 Lacerations at the more delicate pelvic urethra and bladder neck are particularly susceptible to blockage because of the way the balloon catheter rests circumferentially around the communication between these two structures.

In a complete study, the balloon should be deflated and moved cranially after the initial contrast infusion to allow for assessment of the trigone and proximal urethra. Before an intact bladder is diagnosed, another set of radiographs should be obtained once the balloon has been deflated and moved cranially and additional contrast has been infused and given time to leave the bladder through any defect.

References
1. Meynard JA. Traumatic rupture of the bladder in the dog—a clinical study of nine cases. J Small Anim Pract 1961;2:131-134.
2. Slatter DH. Urinary bladder. In: Textbook of small animal surgery. 3rd ed. Philadelphia, Pa: Saunders, 2003;1632.
3. Park RD. Radiographic contrast studies of the lower urinary tract. Vet Clin North Am Small Anim Pract 1974;4:863-887.
4. Selcer BA. Urinary tract trauma associated with pelvic trauma. J Am Anim Hosp Assoc 1982;18:785.
5. Miller ME, Evans HE, Christensen GC. Miller's anatomy of the dog. 4th ed. Philadelphia, Pa: Saunders, 2012; 367-385.
6. Dixon RT. Contrast techniques—the retrograde cystogram. Aust Vet Pract 1974;4:213-219.
7. Lascelles AK. X-ray confirmation of a suspected ruptured bladder in a dog. Aust Vet J 1956;32:147-148.
8. Thrall DE. The urinary bladder. In: Textbook of veterinary diagnostic radiology. 5th ed. St. Louis, Mo: Saunders Elsevier, 2007;708-724.
9. Wallack ST. The handbook of veterinary contrast radiography. Solana Beach, Calif: San Diego Veterinary Imaging, 2003;123-134.
10. Morgan JP. Techniques of veterinary radiography. Ames: Iowa State University Press, 1993.
11. Essman S. Contrast cystography. Clin Tech Small Anim Pract 2005;20:46-51.
12. Ticer JW, Spencer CP, Ackerman N. Positive contrast retrograde urethrography: a useful procedure for evaluating urethral disorders in the dog. Vet Radiol Ultrasound 1980;21:2-11.