The bladder and urethra

image of The bladder and urethra
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Radiographic examination remains a critical tool for diagnosis of diseases of the canine and feline lower urinary tract. Although ultrasonographic investigation is also very valuable, especially for examination of the baldder, the urethra is largely inaccessible using this modality. Radiographic examination of the urethra is a key diagnostic method, notably in male dogs and cats because of the technical difficulties of examining the urethra endoscopically in this sex. Normal radiographic anatomy; Plain radiography; Contrast radiography; Ultrasonography; Overview of additional imaging modalities; Urinary bladder diseases; Urethral diseases are all included.

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17.1 Plain lateral radiograph of a male cat showing normal bladder size, shape and position. A urethral stone (black arrow) is also present. Retrograde vaginourethrogram and cystogram of a bitch with an intrapelvic bladder neck (*). The white arrow depicts the external urethral orifice. V = Vagina.
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17.2 Retrograde vaginourethrogram of a normal Staffordshire Bull Terrier bitch. BN = Bladder neck; EUO = External urethral orifice; F = Bulb of the Foley catheter; V = Vagina; Ve = Vestibule.
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17.3 Retrograde urethrogram of a normal male dog. BN = Bladder neck; 1 = Pelvic urethra; 2 = Perineal urethra; 3 = Penile urethra.
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17.4 Retrograde vaginourethrogram of a normal female cat. The white arrow depicts the external urethral orifice. BN = Bladder neck.
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17.5 Retrograde urethrogram of a male cat. Note that this cat is a congenitally tailless Manx. Note the Allis forceps on the prepuce (arrowed). 1 = Membranous urethra; 2 = Penile urethra.
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17.6 VD view of the bladder in a normal bitch. Superimposition of the pelvis and vertebrae limit the value of this view.
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17.7 Lateral view of a pneumocystogram in a normal bitch. A metal Tiemans urethral catheter is in place but should have been withdrawn before exposure.
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17.8 Subserosal air (arrowed) following pneumocystography in a male Newfoundland puppy. This is a consequence of over-distension of the bladder during insufflation and/or traumatic catheterization, resulting in perforation of the layers of the bladder wall.
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17.9 A double-contrast cystogram of a normal male cat.
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17.10 Placement of a Foley catheter in the distal penile urethra of a male dog in preparation for retrograde urethrography.
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17.11 Plain radiographic study of the penile urethra in a dog, demonstrating the ‘legs forward’ positioning used to remove overlying structures from the penile and perineal urethra. Note the radiopaque stone close to the tuber ischium (arrowed). Retrograde urethrogram taken after retrograde flushing. The animal is positioned to allow evaluation of the perineal urethra in particular. There is some smooth narrowing at the ischial arch (arrowed), which may represent periurethral swelling or muscle spasm during injection.
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17.12 Retrograde urethrogram of a male dog with positioning, centring and exposure technique to evaluate the pelvic urethra. Note that the urethra at the level of the femoral heads is still difficult to distinguish; performing the study with a full bladder may improve contrast medium filling in this area.
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17.13 Placement of Foley catheter for retrograde vaginourethrography in a Labrador Retriever. The bulb of the catheter is inflated just inside the vulval lips, which are closed around it with two Allis tissue forceps. Ventral is to the left and the tail is to the right, with the animal in right lateral recumbency.
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17.14 Transverse ultrasonogram of a normal canine bladder. The layering is apparent. Note the relatively hypoechoic outer muscular layer. The urine itself is anechoic due to the absence of macroscopic particles.
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17.15 Longitudinal ultrasonogram of a canine bladder showing settled sediment, with a distinct border between the anechoic urine and the moderately echogenic debris of the small particles.
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17.16 Ultrasonogram of a canine bladder containing a group of calculi. The calculi are clustered due to gravitational effects, producing bright echogenic reflections and acoustic shadowing behind.
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17.17 Transverse ultrasonogram of a canine bladder containing soft tissue debris floating within the lumen. Note the absence of acoustic shadowing.
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17.18 Transverse ultrasonogram of a normal canine bladder neck with superimposed colour flow Doppler highlighting a ureteral jet (red).
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17.19 Gross distension of the bladder demonstrated on a plain lateral radiograph of a dog with a neurological cause of urinary retention.
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17.20 Double-contrast cystogram of an over-distended bladder in a male cat following drainage. Although the bladder has been filled to an appropriate size, the wall remains folded.
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17.21 Lateral positive-contrast cystogram of a bitch following abdominal trauma. Note the positive-contrast agent outside the bladder lumen and between the serosal surfaces of other abdominal organs.
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17.22 Positive-contrast cystogram of a cat with chronic urinary obstruction, illustrating a bladder diverticulum or urachal remnant (arrowed).
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17.24 Plain lateral radiograph of a bitch with a single large radiopaque calculus, which proved to be struvite on analysis. Plain lateral radiograph of a bitch with a cluster of oxalate calculi.
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17.25 Double-contrast cystogram of a male dog with radiopaque calculi, which appear as filling defects in the small pool of contrast medium.
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17.26 Double-contrast cystogram showing a bubble artefact. The bubble is circular and lies at the edge of the contrast medium pool.
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17.27 Plain lateral radiograph of a female cat with ‘bladder sand’ (multiple small calculi). A double-contrast study makes the diagnosis more apparent.
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17.28 Transverse ultrasonogram of the bladder showing multiple mural masses.
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17.29 Double-contrast cystogram of a young Dobermann with an extensive rhabdomyosarcoma of the dorsal bladder wall and neck.
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17.30 Pneumocystogram and concurrent intravenous urography of an elderly male dog with a bladder neoplasm at the trigone. Note the involvement of the trigone and the tortuosity of the left ureter; these findings are consistent with an obstruction of the ureteral orifice.
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17.31 Double-contrast cystogram of a middleaged bitch with a mass at the bladder apex, seen as a multi-lobulated soft tissue mass with some contrast medium adherence (the urethral catheter is seen within the bladder in a dorsal location). This proved to be a rhabdomyosarcoma. Intraoperative view during cystotomy.
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17.32 Double-contrast cystography of a dog with polypoid cystitis. A polyp is clearly visible arising from the ventral bladder wall, causing a ‘cauliflower’-shaped filling defect in the contrast medium pool. More contrast medium adherence to the abnormal tissue would be apparent if less positive contrast medium was present in the bladder.
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17.33 Double-contrast study of a dog with multiple blood clots in the bladder. These were due to renal haemorrhage and can be seen as multiple irregular filling defects in the contrast medium pool. A retrograde urethrogram is being carried out concurrently.
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17.34 Double-contrast cystogram of a male cat with sloughing of the bladder epithelium following prolonged urethral obstruction. Contrast medium is adherent and outlines the epithelium. Note also the presence of a bubble (arrowed).
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17.35 Double-contrast cystogram showing emphysematous cystitis in an English Setter bitch, associated with chronic urinary retention due to neurological disease. Note the gas streaks within the bladder wall, especially around the bladder neck.
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17.36 Urethrogram of perineal rupture and retroflexed bladder. The urethra is markedly kinked and partially obscured by contrast medium within the bladder. Several small air bubbles are present proximal to the tip of the urethral catheter. (Courtesy of P Holt)
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17.37 Urethrogram of a male Old English Sheepdog with an inguinal hernia and displaced bladder. (Reproduced from ) with permission from the publisher)
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17.38 Plain lateral radiograph of a male dog with multiple radiopaque calculi in the bladder and perineal urethra. Plain lateral radiograph (legs forward position) showing multiple radiopaque calculi in the pre-penile urethra of a male dog. Plain lateral radiograph of the penis of a Cavalier King Charles Spaniel with chronic urolithiasis. Multiple radiopaque calculi are visible, some of which have resulted in localized resorption of the os penis due to their longstanding nature.
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17.39 Plain lateral pelvic view of a male cat with urethral obstruction due to a radiopaque stone in the membranous urethra. Following successful retrograde flushing, the stone is now present in the bladder (arrowed).
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17.40 Plain lateral radiograph of the caudal abdomen and pelvis of a male Staffordshire Bull Terrier with dysuria. No urethral stones are visible. Positive-contrast urethrogram. Note the filling defects at the pelvic brim, which are calculi that were not visible on the plain radiograph, probably due to limited radiopacity and overlying pelvic structures.
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17.41 Plain lateral radiograph of the penis of a male dog, showing radiopaque ‘pseudocalculi’. These are in fact separate centres of ossification caudal to the os penis.
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17.42 Lateral pelvic radiograph of a spaniel after a road traffic accident. In addition to multiple pelvic fractures (and prior partial orthopaedic repair) there is disruption of the soft tissue planes of the perineum, suggestive of an urethral rupture.
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17.43 Retrograde urethrogram of a traumatized Springer Spaniel confirming the presence of two ruptures of the urethra: one at the ischial arch and one within the pelvis.
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17.44 Retrograde urethrogram of a male cat with iatrogenic urethral rupture following unsuccessful attempts at catheterization. The study shows extravasation of contrast agent from the penile urethra both into the soft tissues of the perineum and into the penile vasculature. Peritoneal effusion is also present.
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17.45 Retrograde urethrogram of a male cat 10 days after rupture of the intrapelvic urethra. The rupture has sealed but a stricture is present at the site. Additionally, a mushroom-tipped radiopaque cystotomy tube is in place.
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17.46 Typical retrograde vaginourethrogram of a bitch with a urethral carcinoma. Note the distortion and irregularity of the majority of the urethral length, presenting an ‘apple core’ appearance. Urethritis is an important differential diagnosis but carcinoma was confirmed by suction catheter biopsy in this case.
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17.47 Retrograde urethrogram of a male Dachshund with diffuse urethritis. The perineal urethra is most clearly affected, with variable narrowing and urothelial irregularity.
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17.48 Retrograde vaginourethrogram of a young Labrador Retriever bitch with an intramural ectopic ureter. Retrograde filling of the ureter shows that it joins the urethra in the mid-pelvis. Further cranially, the ureter is seen dorsal and parallel to the urethra. The intra-abdominal ureter is seen to be less distinct (because of the lower concentration of iodine in the lumen from intravenous urography, rather than retrograde filling) and is dilated.
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17.49 Retrograde urethrogram showing an ectopic ureter in a cat.
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17.50 Retrograde vaginourethrogram of a Golden Retriever bitch with an ectopic ureter. In this patient the ureter joins at the urethral papilla and may be described as a vaginal ectopic ureter. At the bladder neck, a filling defect may represent a ureterocele. An intravenous urogram has already been carried out. The ectopic ureter is seen to be moderately dilated. The contralateral ureter is normal in diameter. It is not possible to distinguish which ureter is affected (left or right) and bilateral ectopia cannot be excluded.
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17.51 Retrograde urethrogram of a male dog with unilateral ureteral ectopia. The ureter is seen to communicate with the prostatic urethra. Regrettably, several air bubbles are present, causing artefactual filling defects.
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17.52 Retrograde vaginourethrogram of a Cocker Spaniel bitch with a ureterocele. Note the cystic structure at the bladder neck filled with contrast agent from the retrograde study and separated from the bladder lumen by a septum of urothelium. This is represented by a linear filling defect.
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17.53 Surgical view of a ureterocele. Following a ventral midline cystotomy, the abnormal structure is seen as a distinct balloon-like fluid-filled swelling at the bladder neck.
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17.54 Retrograde urethrogram of a young male Cocker Spaniel with urinary incontinence. A urethral diverticulum is present in the caudal pelvic urethra.
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