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CLINICAL TECHNIQUES
Cyndi Brown, DVM, Column Editor
Diagnostic cystocentesis: technique and considerations
Cystocentesis, the aspiration of urine from the urinary bladder, has both diagnostic and therapeutic uses. This month, we discuss the diagnostic reasons for using this technique and summarize the steps necessary to safely perform the procedure in laboratory animals.
Evaluation of urine provides useful information that helps diagnosis, treatment, and prevention of many urinary and nonurinary disorders. The method of collecting urine samples depends on the diagnostic tests to be carried out and the size and temperament of the animal patient. Four methods of urine collection are available: natural micturition, manual compression, catheterization, and cystocentesis.
Cystocentesis is a procedure in which a needle is inserted through the abdominal wall into the urinary bladder to withdraw urine. The procedure can be performed percutaneously or if the abdomen is open (surgically), directly through the bladder wall.
WHY USE CYSTOCENTESIS?
Urine analysis may be necessary for a variety of reasons such as hormonal assays, drug clearance tests, viral isolation, determination of urine pH, and detection of crystaluria or bacteriuria14.
Diagnostic cystocentesis avoids many of the potential problems associated with the collection of urine specimens by natural micturition, manual compression of the urinary bladder, or by catheterization of the urethra. Cystocentesis is the preferred method to obtain a urine specimen that is not contaminated with the normal bacteria of the lower urinary tract57. The urine in the kidneys, ureters, and urinary bladder of healthy animals is sterile. Contamination of urine with resident bacteria from the urethra, genital tract, and integument may complicate interpretation of urinalysis and urine culture results. Catheterization of the lower urinary tract is always associated with the potential hazard of trauma and iatrogenic urinary tract infection8.
PERFORMING CYSTOCENTESIS
Cystocentesis is typically performed in the awake animal. For very small animals (e.g., rats, mice, gerbils, degus) that are difficult to keep still with manual restraint it may be necessary to perform the procedure under sedation. The recommended technique to perform cystocentesis without risk to the animal involves palpation and immobilization of the urinary bladder as well as planning the site and direction of the needle puncture.
Positioning of the animal
The animal may be in lateral or dorsal recumbency (Fig. 1); this is a...