What to Do When It's Difficult to Determine Catheter Insertion Depth?
We know that catheter insertion depth is closely related to urethral length.
Female Urethra:
The female urethral opening is located below the clitoris and above the vaginal opening, and is thick and short. The urethral length in adult women is typically around 3-5 cm. During catheterization, gently insert the catheter 4-6 cm, and after urine begins to flow, advance it another 1 cm.
Male Urethra:
The adult male urethra is 17-20 cm long, with two curves: the prepubic curve and the subpubic curve; and three narrowings: the external opening, membranous portion, and internal opening. During catheterization, these anatomical features should be understood. When inserting the catheter, lift the penis to form a 60° angle with the abdominal wall to eliminate the prepubic curve, allowing the catheter to be inserted smoothly to a depth of approximately 20 cm. After urine flows out, advance it another 2 cm.
Pediatric Urinary Anatomy:
The anatomical feature of the pediatric urinary system is that the bladder is positioned higher. In newborns, the bladder is often pear-shaped and located above the pubic symphysis. In infants, the bladder is close to the anterior abdominal wall and gradually descends into the pelvic cavity with age. In boys at age 1, the urethra is 5-6 cm long, and by sexual maturity it is approximately 12 cm. The female urethra is short, only 1 cm at birth, and can later increase to 3-4 cm.
When catheterizing boys, it is recommended to insert the catheter gradually so that its tip passes beyond the internal urethral opening. When urine just begins to flow, advance it approximately 2-3 cm further from this depth. At this point, the catheter's side holes are positioned above the internal urethral opening inside the bladder, allowing smooth urine drainage. When catheterizing female infants and young children, the catheter should first be inserted approximately 1.5 cm into the patient's urethra, and after urine is seen flowing out, insert it another 0.5 cm.
Understanding the above data, we face a question: during catheterization procedures, how can we know the insertion depth relatively accurately? Relying solely on visual estimation may result in considerable deviation, easily leading to insufficient insertion or excessive depth, especially for those who are just beginning catheterization and whose technique is not yet proficient.
At this time, using catheters with depth markings is more convenient. Through the scale markings on the catheter body, you can precisely control the length of the catheter entering the body, making catheterization evidence-based rather than blind.
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