WURTSBORO VETERINARY CLINIC


CYSTOCENTESIS


Rhea V.Morgan
Diagnostic and Therapeutic Procedures -  Nephrology & Urology

Cystocentesis is the collection or drainage of urine via a needle passed across the abdominal wall and into the caudal abdomen. It is an effective method of collecting urine for both urinalysis and culture because bacteria, cells and other material from the urethra and external genitalia do not contaminate the urine.

CLINICAL USES

Cystocentesis is the preferred method of collecting most urine samples for analysis and culture. It is indicated in almost any medical situation where analysis of the urine is advisable, from suspected lower urinary tract infections to assessing crystalluria and renal concentrating ability. It may also be helpful in differentiating the origin of hematuria. It is indicated in all animals in which catheterization of the bladder might predispose them to infection, such as in those with diabetes mellitus and immunosuppression. Cystocentesis is also used to empty the bladder when voluntary urination and catheterization cannot be performed. Such instances include urethral obstruction in the cat and herniation of the bladder into a perineal hernia in dogs.

TECHNIQUE

  • Sedation -- Cystocentesis can be performed in most animals without sedation or tranquilization. No local anesthetic is needed.
  • Positioning - Cats and small dogs are usually placed in lateral recumbency, with the hind legs extended caudally. For larger dogs and obese cats, the animal is most often positioned in dorsal recumbency with the hind legs extended straight back from the body. Cystocentesis may also be performed with the animal standing.
  • Materials - For collection of a sample of urine, a 3 to12 cc syringe attached to a 1.5-inch, 22-gauge needle is used. In large or obese animals a 2.5-inch needle may be required. For drainage of urine, the needle can be attached to extension tubing, which is then connected to a 20 to 35 cc syringe, or to a 3-way stopcock and syringe.
  • Procedure - Initially the bladder is located by palpation. If the bladder is empty or small, then cystocentesis should be delayed until the bladder contains more urine. Alternatively, ultrasonography may be used to guide cystocentesis of small bladders, or of bladders that cannot be manually located (e.g. obese or tense animals).
    • Hair may be clipped from the proposed entry site of the needle or simply spread apart by wetting with alcohol. If the hair is clipped, then the skin may be prepared using sterile technique.
    • Needle penetration in the laterally recumbent animal is usually through the paralumbar fossa, with the bladder trapped against the body wall or fixed between the thumb and forefingers.
    • Needle penetration is through the ventral, caudal abdominal midline when the animal is in dorsal recumbency. Needle penetration through either location can be used when the is animal standing.
    • When the animal is in dorsal recumbency, the point of needle entry through midline varies, depending upon the location of the bladder. If the bladder can be localized by palpation, then the needle is directed into the most bulbous part of the bladder. If the bladder cannot be palpated, then a small amount of alcohol is poured onto the caudal abdomen, just cranial to the pubis. Note where the alcohol pools in the midline and direct the needle ventrally into the abdomen through that site.
    • If possible, the needle is directed into the ventral or ventro-lateral aspect of the bladder, at a 45 to 90 degree angle.
    • Aspiration on the syringe should yield urine. If no urine is retrieved, the needle is withdrawn almost to the body wall and carefully redirected.
    • If the bladder is herniated into a perineal hernia, the bladder is located by rectal palpation or palpation of the perineal fossa lateral to the anus. The needle is directed into the bladder from a position lateral to the anus and dorsal to the ischium, so that it enters the most bulbous part of the bladder.
  • Potential complications - With proper technique, serious complications are rare with cystocentesis.
    • Hematuria may occur following cystocentesis, and red blood cells may be noted microscopically in the urine sediment.
    • Leakage of infected urine into the abdomen may cause peritonitis, although this is rare. Leakage of urine is most likely when the bladder wall is compromised from prolonged urinary obstruction or in the presence of extensive bladder neoplasia. Leakage of urine may also occur if forceful palpation of the bladder is continued after the needle is withdrawn.
    • Inadvertent centesis of a paraprostatic cyst, prostatic abscess, or an enlarged uterus may result in focal leakage of infected material with subsequent peritonitis. If the fluid removed is similar in appearance to urine (e.g. paraprostatic cyst), then results of analysis of the fluid can be misleading or confusing.
    • Penetration of the needle too deeply into the abdomen may allow penetration of the aorta or vena cave with serious intrabdominal hemorrhage.
    • Imprecise placement of the needle may result in penetration of other abdominal organs or masses. However, these fine needle track injuries to other organs do not often cause serious organ damage or sequelae.

INTERPRETATION

  • Urinalysis - Urine collected via cystocentesis is analyzed in similar fashion to urine collected by other means. Microscopically it is not unusual for red blood cells to be found in the urine if the bladder mucosa hemorrhages as the needle penetrates the bladder wall.
  • Bacterial culture and sensitivity - Collected urine is placed in proper storage or shipping media for bacterial isolation. Most often aerobic cultures are performed