Cystocentesis in Dogs

Cystocentesis in dogs is a sterile procedure used to collect a urine sample directly from the urinary bladder by inserting a needle through the abdominal wall. It is considered the gold standard for obtaining a urine sample for bacterial culture and sensitivity testing because it minimizes contamination from the urethra, genital tract, and skin.

1. Purpose & Indications

Sterile Urine Sample: Primarily for bacterial culture and sensitivity (C&S) to diagnose urinary tract infections (UTIs) and determine appropriate antibiotic treatment.
Urinalysis (U/A): While a free-catch sample can be used for routine urinalysis, a cystocentesis sample provides the most accurate reflection of the bladder environment, free from external contaminants that can alter results (e.g., skin cells, bacteria from urethra, debris).
When Voiding is Difficult: If a dog cannot urinate on command or is difficult to catheterize.
To Relieve Distension (in some cases): In rare cases of severe urethral obstruction where a catheter cannot be passed, a small amount of urine may be aspirated to relieve painful bladder distension temporarily, although this is not its primary purpose and carries a higher risk.

2. Contraindications

Empty or Very Small Bladder: Difficult to locate and higher risk of missing the bladder or damaging surrounding organs.
Uncooperative/Struggling Patient: Increased risk of lacerating the bladder or other organs if the animal moves suddenly during the procedure. Sedation or chemical restraint may be necessary.
Coagulopathy (Bleeding Disorder): Increased risk of hemorrhage into the bladder (hematuria) or abdomen.
Bladder Tumors: Although sometimes still performed if essential for diagnosis, there’s a theoretical risk of seeding tumor cells into the abdomen.
Recent Abdominal Surgery: Adhesions may make the bladder less mobile and increase the risk of injury.
Pyometra or Other Abdominal Masses: Risk of accidentally puncturing these structures instead of the bladder.
Extreme Bladder Wall Thickening: Can make piercing the bladder difficult.

3. Necessary Equipment

Needles:
22 gauge (G), 1 to 1.5 inches in length for most dogs (smaller dogs, larger dogs, etc.).
20 gauge (G), 1 to 1.5 inches for very large or obese dogs.
A longer needle might be needed for very obese patients.

Syringes:
3 mL (for small bladders or minimal sample needed).
6 mL or 12 mL for larger bladders or when more sample is required.
Alcohol: Isopropyl alcohol (70%) for skin preparation.
Sterile Sample Tubes: For urine storage and transport (e.g., red top, sterile urine culture tube).
Gloves: Non-sterile examination gloves are usually sufficient for the operator; sterile gloves can be used if preferred for culture samples.
Clippers (optional): For very long-haired dogs to ensure good skin contact, though often not necessary.
Ultrasound Machine (Highly Recommended): For precise bladder localization and guidance, significantly increasing safety and success rates.

4. Procedure (Step-by-Step)

Patient Preparation:
Explain the procedure to the owner and obtain consent.
Ensure the dog has a reasonbly full bladder (it helps to palpate or visualize it first).
If the dog is extremely anxious or fractious, mild sedation may be considered to ensure safety and success.

Positioning:
Dorsal Recumbency (on their back): This is often preferred as it allows the bladder to fall cranially into the abdominal cavity, making it easier to access.
Lateral Recumbency (on their side): Can be used, particularly if the bladder is very large and palpable.
Standing: Possible for very large bladders, but generally less ideal.

Locate the Bladder:
Palpation: Gently palpate the caudal-ventral abdomen to locate the firm, round bladder.
Ultrasound Guidance: This is the safest and most accurate method. Visualize the bladder, identify an area free of major vessels or bowel loops, and ensure the bladder is adequately distended.

Aseptic Preparation:
Apply liberal amounts of isopropyl alcohol to the skin over the anticipated puncture site (midline or slightly lateral to midline, cranial to the pubis). Alcohol helps spread hair, allows better visualization of the skin, and provides some antiseptic action.

Stabilize the Bladder:
Gently stabilize the bladder between the fingers, if palpable, to prevent it from rolling away. Avoid excessive pressure, especially with ultrasound.

Needle Insertion:
Attach the needle to the syringe.
Angle: Insert the needle at approximately a 45-degree angle in a caudocranial (towards the dog’s head) direction. This oblique angle helps create a “flap valve” effect in the bladder wall, reducing leakage after withdrawal.
Manner: Use a quick, decisive stab motion through the skin and abdominal wall directly into the bladder. A slow approach can cause more pain and allow the bladder to move.
Do NOT redirect the needle once it has penetrated the skin. If you miss or need to adjust, withdraw the needle completely and start a new puncture at a slightly different location. Redirecting can lacerate organs and cause internal bleeding/leakage.

Aspiration:
Once the needle is in the bladder (you might feel a slight “pop” as it enters), gently apply negative pressure to the syringe plunger.
Urine should flow into the syringe.
Collect the desired amount of urine. If urine stops flowing, gently reposition the needle slightly, but do not redirect aggressively.
Do not aspirate the bladder completely dry, especially if it’s distended, as this increases the risk of the bladder collapsing onto the needle, causing a laceration.

Withdrawal:
Crucially, release the negative pressure on the syringe BEFORE withdrawing the needle. This prevents suctioning urine or blood into the needle track as it exits, reducing the risk of leakage into the abdomen.
Withdraw the needle quickly and smoothly.

Post-Procedure Care:
Apply gentle pressure to the puncture site for a few seconds.
Monitor the patient for any signs of discomfort, abdominal pain, or distension (though complications are rare).

Sample Handling:
Transfer the urine into appropriate sterile sample containers immediately.
Label the samples clearly with the patient’s name, ID, date, time, and collection method (cystocentesis).
Refrigerate samples if they cannot be processed or sent to the lab within 30 minutes (for urinalysis) or a few hours (for culture).

5. Potential Complications

Hematuria (Blood in Urine): The most common complication, usually mild and transient, resolving within a few hours to a day.
Abdominal Hemorrhage: Rare, but can occur if a major vessel is hit.
Peritonitis: Extremely rare but serious, caused by leakage of urine or, more severely, intestinal contents into the abdominal cavity (if bowel is accidentally punctured).
Bowel Puncture: Accidental penetration of the intestine, leading to potential peritonitis. This risk is greatly reduced with ultrasound guidance.
Bladder Laceration: Can occur if the bladder is very small or the patient moves suddenly, especially if the needle is redirected.
Failure to Obtain a Sample: Can happen if the bladder is missed or inadequate negative pressure is applied.
Vasovagal Response: Very rare, leading to temporary collapse due to a nerve-mediated drop in heart rate and blood pressure.

Important Note: Cystocentesis is a sterile medical procedure that should only be performed by a qualified veterinary professional.

#Cystocentesis, #CanineCystocentesis, #DogCystocentesis, #VeterinaryMedicine, #VetMed, #DogHealth, #PetHealth, #UrinaryHealth, #DogUrinaryHealth, #UrineSample, #SterileUrineSample, #BladderTap, #VeterinaryDiagnostics, #VetTech, #VetLife, #PetsOfInstagram, #DogsOfInstagram, #UTIinDogs, #CanineHealth, #VeterinaryProcedure, #PetCare, #AnimalHealth