Contributors: Alison Dickie
Species: Feline | Classification: Miscellaneous
- Investigation of:
- Confirm position of:
- bladder neck.
- Low cost.
- Short time requirement.
- No known biological risk.
- Allows ultrasound guided:
- Fine needle aspirate.
- Cystocentesis Cystocentesis .
Time requirement will reduce with operator experience.
- Will require patient's coat to be clipped.
- Normal sonographic appearance does not exclude disease.
- Abnormal sonographic appearance does not always indicate significant disease.
- Similar sonographic appearance with different diseases.
- Poor transducer-skin contact:
- Inadequate clipping.
- Insufficient coupling medium.
- Inadequate patient restraint (may require sedation).
- Operator inexperience.
- Patient has urinated prior to examination so bladder is empty.
- Enter patient identification, date and other relevant information on the screen.
- Alter time-gain, depth and focal point settings throughout the examination to optimize the images obtained.
- Keep power setting low to reduce noise.
- High frequency (7.5 MHz).
- Linear, curvilinear or sector.
- Small scan face most convenient for cats.
Image production and storage
- Any of the following are acceptable:
- Thermal printer.
- video recorder.
- Multiformat camera.
- Disk drive.
- Coupling medium:
- Ultrasound gel.
- Alcohol or spirit.
- Quiet room with reduced lighting.
- Table, preferably with comfortable surface, eg blanket or foam pad.
A relaxed patient will avoid the need for sedation.
- Assistant to restrain patient.
- Sedation may be required depending on the nature of the patient.
- Sedation or GA necessary if aspirate or biopsy to be performed.
- Ensure patient has a full urinary bladder.
Where to clip
- Caudal ventral midline of abdomen.
- Position depends on operator preference.
- Right then left lateral recumbency or dorsal recumbency suitable.
- Alteration of patient position during examination is beneficial in identifying some conditions.
- Swab clipped area of skin with alcohol.
- Apply ultrasound gel to the skin surface and the transducer before commencing with the examination.
- Place the transducer on the ventral midline of the caudal abdomen using a longitudinal imaging plane.
- Angle the ultrasound beam caudo-dorsally until the bladder is identified.
- Angling further caudodorsally towards the pelvic brim will allow the bladder neck to be imaged.
- Move the transducer cranially along the abdominal surface until the cranial wall of the bladder is imaged.
- Rotate the transducer through 90° to image the bladder in short axis.
- Alter the angle of the ultrasound beam relative to the skin surface and move the transducer up the abdominal wall to examine the bladder from a series of different positions.
- Urinary bladder is pear shaped, tapering to the bladder neck caudally.
- Location of the cranial bladder wall will depend on the distention of the bladder.
- The wall appears as a smooth, hyperechoic line 1-2 mm thick when the bladder is distended .
- 3 layers may be seen with high resolution transducer.
- The wall appears thick and corrugated after urination.
- Bladder contents should be anechoic.
- The ureteral papillae may be imaged as small echogenic mounds at the trigone.
- Ureteral jets are occasionally visualized as short-lived streams of echogenic material arising at intervals from the papillae.
- Normal ureters not visible.
- Proximal urethra may be followed from bladder neck until it enters pelvic cavity.
Common problems or artifacts
- More than one condition may be present concurrently.
- The bladder must be distended before wall thickness can be accurately assessed. If the bladder is empty, then rescan the patient a few hours later once it has refilled.
- Increased frequency of urination associated with many bladder diseases may make it difficult to perform examination in presence of full bladder.
Can introduce sterile saline via a urinary catheter to distend bladder.
- Bladder wall in near field often does not image well due to close aposition to transducer.
Alteration of transducer position will ensure entire wall imaged well - alternatively, a sonolucent stand-off pad may be used.
- Slice thickness and reverberation artifacts produce appearance of echogenic material within lumen and should not be mistaken for intraluminal or mural abnormalities.
- Distal acoustic enhancement commonly observed in region beyond bladder.
- Pressure on transducer may cause colon to become indented into bladder wall producing appearance similar to that of a urinary calculus.