Animal Health Solutions

23 Q3 2020 | Animal Health Solutions The presence of urinary crystals in a greater or lesser degree depends on metabolic particularities typical of the species. In cats, the oversaturation of urine with phosphate and ammonium is normal because they are strict carnivores; therefore, struvite crystals are considered a normal component of urine and can commonly form part of the urethral plug (Figure 2). Some authors suggest that the secretion of mucoproteins and their degradation products can lead to alkaline urine, favoring precipitation of more proteins and struvite crystals, making it very common to find these types of crystals as part of the urethral plug. 1 So, a matrix plug, an inflammatory process that creates pain and causes urethral spasm, and/or the presence of sand or small uroliths, can block the urethra, especially the penile urethra, which is the longest and narrowest area in the case of males, and therefore predisposed to UO 5,6 (Figure 3). However, UO may also be present in females, with lower frequency. A UO for more than 48 hours can lead to azotemia, hyperkalemia, hyperphosphatemia, metabolic acidosis, and acute kidney injury, so it should be considered a medical emergency, 1 as the patient may die in 3 to 6 days if not attended to. 7 Despite this, it is a treatable emergency with a rate of survival greater than 90%. 2 In addition to the serious alterations described, UO can cause the urinary bladder to be distended severely increasing the internal pressure and causing mucosal injury and urinary bladder wall necrosis. 6 The goal of the medical management of UO in the cat is to achieve stabilization of the patient, to seek to reverse the hydroelectrolytic disorders, maintain an appropriate tissue infusion, minimize visceral pain, and provide rapid obstruction relief without traumatizing the urethra when placing the urethral catheter. 7 Figure 1 Male cat with blocked urethra. Left: On the inspection of the penis the presence of the urethral plug is observed at the external urethral orifice. Right: Appearance of a part of the urethral plug that was removed with the help of penile massage. Figure 2 Microscopic image of the urethral plug. Note the large number of struvite crystals. Figure 3 Male cat with UO by urolithiasis. Left: X-ray where multiple uroliths are observed in the penile urethra. Right: Endoscopic images: by transvesical access, the urinary bladder trigone with uroliths of different shapes and sizes, and the urinary catheter that emerges from the urethral lumen; note inflammation and ulcers in the urinary mucosa due to the trauma generated by the uroliths.

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