Fluoroscopy-guided balloon dilation of a proximal urethral stricture caused by a urethral membrane in a female cat

Rincon Alvarez, Javier; Smith, Victoria; Broome, Cameron

Urethral obstruction is a common condition in cats. 12 It can occur as a result of the presence of urethral plugs, urolithiasis, neoplasia, granuloma formation, bladder displacement or herniation, urethral stricture or idiopathic causes. 1, 13, 14 Strictures are defined as a reduction in the diameter of the lumen of a hollow structure. This occurs owing to the presence of cicatricial tissue as a result of inflammation and has been reported in hollow organs, such as the oesophagus, the rectum, the trachea, ureters and the urethra. 15, 16 In the present case, the lesion was considered a stricture, as its location did not correlate with a natural narrowing point of the urethra. Furthermore, it was located proximally at it widest point. To our knowledge, the proximal nature of the stricture is thought to be a novel clinical finding, as previous literature only describes the presence of distal or mid urethral strictures in cats. 1 Urethral strictures are usually sequelae of malignancy, pelvic trauma, severe inflammation or surgical intervention. 9, 11, 14 From the case history, stricture formation was considered congenital in origin based on signalment and the lack of trauma, urethral catheterisation or surgical intervention prior to presentation. In addition, the presence of the membranous structure separating both cavities suggests a congenital origin. Despite the lack of histopathology, it was considered to be a membrane based on the correlation of its clinical appearance and the definition of a membrane as a 'thin layer of Six-week post-balloon dilation retrograde urethrogram. Marked improvement of the previously reported urethral stricture. Although some degree of reduction of the urethral diameter can be appreciated, good contrast flow into the bladder is noted tissue separating two cavities'. 15 It was hypothesised that the membrane originated from the urethral mucosa. A similar finding has been reported in a dog with partial urethral obstruction, which was also suspected to be congenital in origin. 7 Urethral strictures typically present with clinical signs of dysuria and pollakiuria owing to partial or complete lower urinary tract obstruction. [17] [18] [19] In this case, the cat presented with similar dysuria, stranguria and incontinence. The mild uraemia noted on biochemistry analysis was considered either postprandial in nature or subclinical dehydration. The cat's hydration status appeared clinically correct; however, subclinical dehydration can present with a marginal elevation of urea. 20 Abdominal ultrasound and contrast radiography are common diagnostic tools when investigating urinary tract disorders. 21, 22 In the present case, the abdominal ultrasound showed focal thickening of the dorsal bladder wall. This was suspected to represent the area previously biopsied by the referring veterinarian. The presence and location of the stricture was confirmed via retrograde positive contrast radiography, an imaging modality commonly used to diagnose urethral strictures. 2, 9, 12, 18, 19 Cystourethroscopy can also be used when investigating persistent lower urinary tract signs, providing a magnified internal image of the urinary tract. In this case, it identified the nature of the urethral obstruction, precluding placement of a urinary catheter. Cystourethroscopy also aids in performing interventional treatments. 23, 24 Although considered a minimally invasive procedure, complications associated with cystoscopy include trauma to the