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tvpjournal.com | September/October 2016 | T O day' S Ve T erinary Prac T ice i maging e SS en T ia LS Peer r eviewed 63 uterus (intact females), colon, and iliac lymph nodes dorsally (far field). Evaluation of Urine & Artifacts Urine in the urinary bladder is normally anechoic; however, echogenic urine is not specific for urinary tract disease. Other US artifacts of the urinary bladder include side-lobe or grating-lobe artifacts. Side-lobe artifacts, or pseudosludge, are caused by mismapped reflections of the secondary US beam into anechoic regions, resulting in echogenic areas within the urinary bladder lumen that can be mistaken easily for sedimentation (Figure 3). a ngling the transducer can sometimes decrease the severity of the artifact and, thus, rule out sedimentation in the urinary bladder. a lternatively, the patient can be imaged in a standing position to assess for gravity dependence, which would be characteristic of true sludge. Urethra The proximal urethra (prostatic urethra in male dogs) can be visualized as a tubular hypoechoic structure continuing caudal to the trigone region of the urinary bladder and extending to the level of the pubic bone. The membranous urethra cannot be visualized due to its location within the pelvis. a ssessment of the penile urethra within the ventrally located urethral groove of the os penis may be performed in male dogs but is typically not included in a normal abdominal US examination. i ndications for a penile urethral US examination include suspicion of a distal urethral obstruction. URINARY TRACT ABNORMALITIES Congenital Abnormalities: Urinary Bladder & Ureter Ureterocele Ureterocele is a rare congenital ureteral malformation that can be associated with ectopic ureters. a n intravesicular ureterocele is characterized by focal cystic dilation of the distal submucosal portion of the ureter that protrudes into the urinary bladder lumen. a thin-walled, round structure containing anechoic fluid can be seen within the neck of the urinary bladder (Figure 4). 4 Urachal Remnants i n the fetus, the urachus connects the apex of the urinary bladder with the allantoic sac through the umbilical cord. Before birth, this structure normally atrophies. i ncomplete closure of the urachus may result in patent urachus, urachal diverticulum, or urachal cyst. Patent urachus is uncommon in dogs and cats. Ultrasonographically, it is seen as a tubular structure extending from the apex of the urinary bladder to the umbilicus. Urachal diverticulum results when the caudal segment of the urachus fails to close. i t appears as a fluid-filled, rounded, thin-walled, well-defined structure extending from the urinary bladder lumen at any location (Figure 5, page 64). 5 The urachal diverticulum disappears in an empty urinary bladder. Urachal cysts form when secretions continue in an isolated section of urachal epithelium while the remainder of the urachus undergoes fibrosis. Ultrasonographically, a urachal cyst appears as a thin-walled, anechoic structure cranial to the urinary bladder. 5 Figure 4. Long-axis sagittal image of the trigone region of the urinary bladder in a Tibetan terrier. Note the minimally to moder- ately distended urinary bladder with a hypere- choic, thin-walled structure (arrowheads) with anechoic fluid centrally located in the trigone and urinary bladder neck. This is consistent with a ureterocele. Figure 3. Long-axis sagittal image of the trigone region of the urinary bladder showing a side-lobe artifact (arrowheads).