Filiform and Follower Urethral Catheterization

Updated: Dec 01, 2022
  • Author: Vernon M Pais, Jr, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Urethral catheterization can be difficult for various reasons, including false passage during recent or past catheter placement attempts, prior urethral trauma resulting in urethral stricture, enlargement of the prostate gland (eg, benign prostatic hyperplasia, prostate cancer), or prior surgery on the urinary tract (eg, transurethral prostatectomy [TURP], hypospadias repair). In these scenarios, urologists are often called to the operating room or bedside to assist with the placement of urethral catheters when the primary team is unsuccessful.

These difficult catheterizations often require additional equipment such as specialty wires, catheters, or bedside flexible cystoscopy. However, predating the advent of flexible cystoscopy, the urologist was able to place the catheter blindly by drawing on a broader understanding of urethral anatomy and increased tactile experience. Foremost in their armamentarium were filiforms and followers. These tools allow blind negotiation of the true path of the urethral lumen and ultimately 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. [1]

When this technique is successful, it eliminates the need for cystoscopy or suprapubic tube placement if a flexible cystoscope is not available. Furthermore, dilation can be therapeutic and may give the patient a better chance at being able to void spontaneously when the catheter is removed. In fact, filiforms and followers are still widely used for dilation in men with known urethral stricture disease. [2]  Zisman et al report that filiforms and followers have been used to dilate urethral strictures after metoidioplasty and phalloplasty in transgender men. [3]

Moreover, a study by Granieri et al found that nationally in the United States, in an emergency department setting, urethral dilation is more common than suprapubic tube (SPT) placement for the treatment of acute urinary retention due to urethral stricture; however, SPT placement has seen increased use. Data were culled from the 2006-2010 Nationwide Emergency Department Sample, with 85% of men with acute urinary retention undergoing urethral dilation and 15% being treated with SPT placement. [4]

Although the filiform/follower technique was once commonly employed in difficult catheterizations, a survey noted that less than 10% of urology residents in the United States would use filiforms and followers if they failed on their initial attempt to place a Foley catheter (with up to 74% instead opting to use flexible cystoscopy). This downward trend in the use of filiforms and followers is due in combination to the increased availability of flexible cystoscopy and the challenges senior urologists face in teaching residents to correctly use tactile sensation. [5]



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 should 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. [6]

Filiforms and followers are widely used as first-line treatment for men with known urethral stricture disease. In these cases, placement of a catheter is not always required. Chronic strictures can be safely managed with repeat dilations. [2]



Filiforms and followers should not be used in the trauma setting when urethral disruption is suspected. [6]

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. [6]



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. See the images below.

Filiforms. Filiforms.
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. [7, 8]



The patient should be supine with the penis pointed cephalad. This position straightens the urethra as much as possible prior to passing the instruments. [9]



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. Obtaining this history is an important step which, when neglected, may lead to an increased risk of complications. [10] The patient should be asked if they are on blood-thinning medication (aspirin, warfarin, clopidogrel) 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. [11]

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. See the image below.

Passage of filiforms. 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. See the image below.

A Phillips catheter (or follower). 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. [6, 11]

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 either the filiform or follower has been forced. 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. Keep in mind that urethral dilation in the awake patient may be painful.

Dilation to 16-18F should suffice to allow passage of a 14-16F urethral catheter. However, if the purpose of dilation is simply temporizing (ie, to drain the bladder until definitive surgical repair of stricture can be undertaken), it is recommended to simply dilate to allow passage of a 12F urethral catheter. [12]



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. [9] 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. [11]

Further urethral injury may lead to iatrogenic urethral stricture. Iatrogenic urethral stricture is the leading cause of urethral stricture requiring urethroplasty in the developed world in the 21st century. [13]

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.


Alternative Methods

In most centers, flexible cystoscopy is readily available and can be 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. However, flexible cystoscopy may be used more selectively, adopting an algorithm that uses passage of a glide wire after blind urethral catheter placement has failed. Only if this fails does one turn to flexible cystoscopy in this proposed algorithm. [5]

Others have expanded on the technique of blind passage of a glidewire. Correct placement is confirmed by passing an open-ended ureteral catheter over the wire and visualizing urine drainage from the bladder. In this series, this succeeded in many cases when filiforms had failed and was recommended in the event that flexible cystoscopy was unavailable. [14] 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 on a similar principle to filiforms and followers.

A variation begins with the initial insertion of an open-ended ureteric catheter to both relieve the obstruction and confirm placement. Aspiration of urine with a syringe confirms position in the bladder and a guidewire is then threaded through the catheter. At this stage, filiform dilators may be passed over the guidewire to dilate if necessary. Finally, a Foley catheter with its tip removed is passed over the guidewire and the guidewire may then be removed. [15]

Flexible cystoscopy may not always be available. The aforementioned alternative methods may prove useful but still have their roots established in the passage of filiforms and followers. These techniques are based on a knowledge of urethral anatomy, tactile sensation, and clinical observation. As such, the use of filiforms and followers should be recognized as a foundation of urethral catheterization and not be simply relegated to an historical curiosity or lost art.