Filiform and Follower Urethral Catheterization 

Urologists are often called to the operating room or bedside to assist with the placement of urethral catheters when the primary team is unsuccessful. Many times, the urologist is able to place the catheter by using different kinds of catheters or by drawing on a broader understanding of urethral anatomy and increased tactile experience. In some cases, urethral catheterization can be complicated by false passage during recent or past catheter placement attempts, prior urethral trauma resulting in urethral stricture, enlargement of the prostate gland, or prior surgery on the urinary tract (eg, transurethral prostatectomy [TURP], hypospadias repair).

Before the advent of flexible cystoscopy, urologists used instruments called filiforms and followers to help negotiate the true path of the urethral lumen and access the bladder. Filiforms are smaller than urethral catheters and more likely to pass through narrowings of the urethra. The followers can then be used to dilate the narrowing to a size suitable for passage of a urethral catheter. Although this technique was once commonly employed, a recent survey noted that less than 10% of US urology residents would use filiforms and followers if they failed on their initial attempt to place a Foley catheter.^[1]

However, when this technique is successful, it eliminates the need to perform suprapubic tube placement. Furthermore, dilation can be therapeutic and may give the patient a better chance at being able to void spontaneously when the catheter is removed.

• Filiforms and followers are primarily indicated for nonroutine urethral catheterization when false passage or urethral stricture is suspected and prior attempts to pass a Foley catheter have failed. They can also be used in men with known stricture disease who present for periodic dilation. In these cases, placement of a catheter is not always required.
• They should also be considered an alternative to flexible or rigid cystoscopy with placement of a guidewire under direct vision. Blind insertion of filiforms and followers should be reserved for situations when cystoscopy is not available.^[2]

• Filiforms and followers should not be used in the trauma setting when urethral disruption is suspected.^[2]
• If a retrograde urethrogram shows extravasation of contrast, blind passage of filiforms should not be attempted.

• This procedure can be performed at the bedside without general anesthesia or sedation.
• The surgeon may elect to use 10-20 mL of lidocaine 2% jelly in the urethra for local anesthesia.
• Many facilities stock 10-mL ampules with a cone-topped applicator that can be placed just inside the meatus and injected into the urethra. If this special ampule is not available, the lidocaine jelly can be placed in a catheter-tipped syringe and then instilled into the urethra.^[2]

• Filiforms are offered in various sizes (2-6 French [F]) and tip shapes (straight, spiral, coude). They can be made from a pliable polyurethane or woven fiberglass. Softer materials are preferred so that the filiform easily curls in the bladder while the follower is being passed. Filiforms. Filiforms.
• Followers are offered in pliable plastic, woven material, or metal, in sizes from 10-24F. The wide assortment of sizes allows sequential dilation of the urethra. They can also come in 2 shapes (straight or coude). The follower tip often has a drainage hole that allows urine to drain when it reaches the bladder, thus confirming true passage.
• For convenience, some manufacturers offer urethral catheterization kits that package a set of filiforms and followers together with a catheter, skin cleansing, materials and lubricant.^{[3, 4]}

• The patient should be supine with the penis pointed cephalad. This position straightens the urethra as much as possible prior to passing the instruments.^[5]

• Prior to attempting this procedure, a thorough history and physical examination should be performed. If possible, obtain specific information related to prior catheterization attempts, specifically the type of catheter(s) used, depth of insertion before resistance was encountered, evidence of trauma (eg, blood on catheter or at the meatus), and whether the catheter balloon was inflated in a false passage. The patient should be asked if they are on blood-thinning medication (aspirin, warfarin, clopidogrel, ibuprofen) or if they have any history of coagulopathy (easy bleeding or bruising). The physical examination should concentrate on the penis, scrotum, perineum, and prostate.
• Scrub the suprapubic region, penis, and scrotum with an appropriate preparatory agent. Place large drapes to extend at least down the patient's legs so as to allow a sterile surgical field extensive enough to prevent contamination of the followers (and wires and scopes, if needed). This large field also allows for suprapubic tube placement, if required.
• Before passing any instruments, instill 10-20 mL of 2% Xylocaine jelly or water-based lubricant into the urethra. This dilates the urethra as well as decreases friction caused by passing the instruments.^[1]
• Gently insert the filiform into the urethra. If it has navigated the true urethral lumen, it should readily pass, without resistance, to the anticipated level of the bladder. Passage of filiforms.

  • If the filiform stops short of this or meets significant resistance, it has probably struck a false passage or strictured portion of the urethra. Leave the filiform in place to fill this diseased portion of the urethra and prevent subsequent filiforms from traveling to the same dead end.
  • Take care not to use excessive force. Forcing the instrument through the urethral mucosa can cause greater injury.
• With the preceding filiform in place, another filiform is passed into the urethra, repeating the procedure. Many filiforms of different shapes may need to be passed until the true lumen is encountered. A successfully placed filiform passes with little resistance.
• Once the true lumen has been crossed with reasonable certainty, the previously placed filiforms can be removed.
• Attach the smallest follower of the set to the tail end of the filiform. The follower normally has a threaded “male” tip that corresponds with the “female” insertion point on the tail of the filiform.
• With these 2 pieces firmly attached, pass the follower through the urethra by following the filiform through the true passage and into the bladder. A Phillips catheter (or follower).
• After the follower is passed all the way to the bladder, withdraw and remove the follower from the filiform. Take care to leave the filiform in the urethra so access is not lost.
• Select the next larger size follower, attach it to the filiform, and repeat the procedure. In this fashion, the urethra is sequentially dilated with the passage of successively larger followers.
• Make several passes, until the urethra is dilated to 2F greater than desired catheter size. To reduce further urethral injury, 16-18F is the recommended maximum dilatation.^{[2, 1]}
• With the urethra dilated to an appropriate size, select a council tip catheter or fashion one using a catheter punch. If the dilation is uncomplicated, some circumstances exist in which a standard or Coude tipped catheter may be used. The catheter should be passed alongside the filiform to prevent losing access.
• When using a Council tip catheter, place the catheter over a catheter guide with a threaded screw tip. It will protrude from the hole in the tip of the catheter and can be attached to the filiform.
• Place some water-based lubricant inside the catheter to facilitate removal of the follower and filiform when the catheter is in place. Then screw the follower and catheter onto the filiform and pass them through the urethra and into the bladder, similar to the passes made for dilation.
• While holding the catheter in place, remove the follower and filiform.
• Drainage of urine or gentle irrigation of the catheter confirms correct placement. Ideally, the hub of the catheter should be at the meatus to ensure that the catheter balloon is fully in the bladder.
• Inflate the balloon to secure it in place.

• Apply only gentle pressure. The surgeon should never feel that he or she is forcing a filiform or follower. If it is in the right place, minimal pressure should suffice.
• Use generous lubrication, which facilitates the passage of the instruments and minimizes patient discomfort.
• Dilation should not proceed until one is reasonably certain that the filiform has found the true passage. Only gentle pressure is needed to pass the filiform through the true passage. If more excessive force is needed, it may be a sign that the filiform is in another false passage or that the filiform has curled back on itself. Do not dilate if either of these situations are suspected.
• Dilation to 16-18F should suffice to allow passage of a 14-16F urethral catheter.

• The primary risk of blind insertion of filiforms and followers is false passage. The filiform can create a new false passage if too much force is used, especially if the filiform is too rigid.^[5] A prior false passage can also be dilated if a follower is mistakenly assumed to be in the bladder.
• Perforation of the urethra into the rectum and perforation of the bladder are additional risks of blind placement of filiforms and followers.^[1]
• Infection is a concern anytime instruments are introduced into the urethra and bladder. Patients who require this procedure are likely at increased risk for urinary tract infection due to multiple instrumentations in an attempt to catheterize the bladder.
• Bleeding can be an issue, especially for patients who have very tight strictures or who are taking antithrombotic medications such as aspirin, warfarin, or clopidogrel.
• While most patients can tolerate this procedure without general anesthesia, some do not; the procedure may need to be suspended until proper sedation can be administered.

Freid and Smith describe an alternative to the use of filiforms and followers. Their method involves the blind passage of a Glidewire, with correct placement confirmed by passing an open-ended ureteral catheter over the wire to visualize urine drainage from the bladder. In their series, this was accomplished on many cases when filiforms failed. They recommended this method in the event that flexible cystoscopy was not available.^[6] Once a wire is established through the true passage, then an Amplatz dilator may be passed over the wire using successively larger dilators. This is based upon a similar principle to filiforms and followers.

In most centers, flexible cystoscopy is readily available and can be very quickly set up in the operating room or at the bedside. This method allows direct visualization of urethral pathology and placement of a guidewire under direct visualization. The use of flexible cystoscopy has rapidly emerged as a first-line modality when standard catheter insertion fails. Nevertheless, when flexible cystoscopy is unavailable, the passage of filiforms and followers is an important technique of which to be aware and should not be simply relegated to a historical curiosity or lost art.