A Foley catheter is a flexible tube inserted through the urethra into the bladder for continuous urine drainage. The catheter’s indwelling nature is maintained by a small, inflatable balloon located at the tip. The balloon anchors the catheter securely within the bladder’s neck, preventing it from slipping out. Inflation occurs only after the catheter tip is fully advanced into the bladder cavity.
Standard Foley Balloon Volumes
The volume of fluid used to inflate a Foley catheter balloon is measured in cubic centimeters (cc) or milliliters (mL). For most adult patients, the standard recommended inflation volumes are either 5 cc or 10 cc. The 5 cc balloon is the most common size, providing sufficient retention for routine, short-term catheterization.
A 10 cc balloon is often used when a clinician requires a slightly larger mechanism for retention or for specific clinical needs like managing minor bleeding. The volume listed on the catheter’s packaging should be injected into the inflation port using sterile water or saline. Manufacturers also produce smaller catheters for pediatric patients, which typically have a much smaller 3 cc balloon.
Using the recommended volume ensures the balloon forms the correct shape for retention without causing unnecessary pressure on the bladder wall. Using sterile water, rather than saline, is generally preferred for inflation because the salt in saline can sometimes crystallize, potentially obstructing the deflation channel and making catheter removal difficult.
Factors Determining Balloon Size
The size of the retention balloon is directly related to the overall intended use and the diameter of the catheter itself, which is measured on the Charrière (French) scale. One French unit (Fr) is equivalent to 0.33 millimeters, and this measurement reflects the external circumference of the catheter tube. While smaller French sizes often correlate with smaller balloon volumes, the choice of balloon size is fundamentally driven by the clinical application.
The most common adult catheter sizes range from 14 Fr to 18 Fr, and these are typically paired with the standard 5 cc or 10 cc balloons. Specialized catheters exist for specific procedures, such as those used for hemostasis after a transurethral prostatectomy or for continuous bladder irrigation. These specialized catheters, often referred to as hematuria catheters, frequently feature much larger balloons, sometimes up to 30 cc or even 75 cc, to apply pressure against the prostate bed to control bleeding.
Larger-volume balloons require greater fluid capacity to achieve the necessary size for tamponade, the mechanical compression of a bleeding site. This larger balloon size serves a therapeutic function beyond simple retention. The catheter’s French size must also accommodate the multiple internal channels needed for urine drainage, balloon inflation, and irrigation fluid inflow in three-way catheters.
Risks of Improper Inflation
Inflating the Foley balloon with an incorrect volume of fluid or in the wrong anatomical location can lead to significant complications. Under-inflation increases the risk of catheter migration and accidental displacement. A poorly anchored catheter can be pulled out of the bladder, causing trauma to the sensitive lining of the urethra as the partially inflated balloon scrapes the passage.
Conversely, over-inflation (injecting more fluid than specified) can lead to complications. Excessive pressure can cause the balloon material to rupture, potentially leaving fragments inside the bladder that require retrieval. More commonly, over-inflation creates an unnecessarily large, rigid structure that can exert high pressure on the bladder neck, leading to pain, tissue injury, and discomfort upon removal.
A major risk is the premature inflation of the balloon within the urethra if the catheter is not fully advanced into the bladder first. Inflating the balloon in this location causes immediate and severe pain, and the pressure can damage the delicate urethral lining. This damage can lead to bleeding, scarring, and the formation of urethral strictures over time. Always confirming the return of urine flow into the drainage bag is an important step to confirm correct placement before any fluid is injected into the balloon port.