Techniques of Local Anesthesia for Prostate Procedures and Biopsies

Transrectal ultrasound (TRUS)-guided prostate biopsy is one of the most common procedures performed by urologists. Since its introduction in 1989, there have been numerous efforts to optimize the patient experience by providing more effective local anesthesia. ^{[1, 2]}

Injection of a local anesthetic into the perineum was standard when transperineal prostate biopsy was routine, but this was abandoned when TRUS biopsy became the standard. Since the rectal mucosa was neither easily accessible for direct injection nor considered sensate above the dentate line, some urologists felt that procedural anesthesia was no longer imperative. ^[3]

Historically, biopsies involved taking a limited number of cores from an identified nodule. After the sextant approach was described in 1989 by Hodge et al, it soon became the standard. ^[4] Once patients had undergone extraction of their sixth needle-core biopsy, many of them reported pain.

Over time, the number of cores routinely collected increased to between 8 and 14, with many individuals noting significant discomfort. Although some providers continued to assert that prostate biopsy was a painless procedure, up to 96% of patients disagreed. In one study, 1 in 5 patients said that they would refuse to undergo the procedure again without anesthesia. ^[5]

Experienced providers may attest that less effort is required to obtain patient acceptance for an initial prostate biopsy than for a repeat procedure. Published data has suggested that nearly one-third of patients refuse to undergo a repeat biopsy because of the pain experienced previously.

In 1996, Nash et al described the use of a periprostatic nerve block (PPNB) at the time of biopsy. ^[6] However, until Soloway and Obek published a corroborating study in 2000, ^[7] few urologists opted to change their approach. Over 45 studies have now validated PPNB as an effective technique to improve patient comfort during biopsy.

Relevant Anatomy

A normal prostate volume for an adult male is approximately 25 cc, and continues to grow throughout a man’s lifetime secondary to benign prostatic hyperplasia. The gland is located posterior to the pubic symphysis, inferior to the bladder, and anterior to the rectum. The base of the prostate is in continuity with the bladder neck and contains the prostatic urethra. The gland continues inferiorly to its apex, just above the membranous urethra which is surrounded by the striated external urethral sphincter.

The anal canal is situated between the anal verge (anal orifice, anus) and the rectum. The transition between the rectum and the anal canal is observed at the dentate line. For surgeons, however, the demarcation between the rectum above and the anal canal below is the anorectal ring. The length of the (surgical) anal canal is about 3–5 cm, with two thirds located above the dentate line and one third below (anatomical anal canal).

For more information about the relevant anatomy, see Prostate Anatomy and Anal Canal Anatomy.

As with any procedure in which a patient may feel vulnerable, comfort measures during TRUS biopsy are essential. Patients should have a secure sense of privacy during the procedure. The following methods may be helpful in optimizing the experience:

• Placing a warm blanket over the patient's legs

• Using a curtain in the exam room

• Positioning the exam table so that the patient is not visible immediately upon opening the door to the examination room

• Maintaining a comfortable room temperature

• Speaking to the patient before and during the procedure to set expectations and to put them at ease

Patient positioning is influenced by the type of ultrasound probe used. The two types of probes include the end-fire probe (see the first 2 images below) and the side-fire probe (see the second 2 images below). The two probes provide entirely different views and require different techniques; if the technique for one probe is used for the other, confusion and disorientation will result when trying to identify specific areas via ultrasound.

The end-fire probe displays images in a field directly off the tip of the probe. Thus, visualization of lateral aspects of the prostate necessary for anesthetic injection are identified by moving the probe handle laterally away from the side of interest (handle is moved toward the floor to see the right side and moved toward the ceiling for a left-side view).

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Moving the end-fire probe handle up and down to point toward the left or right side of the prostate maintains orientation and allows visualization of the lateral aspects of the prostate.

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The side-fire probe displays images away from its axis, so that twisting the probe aims the field of view toward the lateral aspects of the prostate.

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Twisting the side-fire probe allows lateral visualization. Thus, the patient does not have to be at the edge of the bed, although this position may still be more convenient for the urologist.

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Types of probes:

• The side-fire probe: Side-fire probes project laterally. For this reason, twisting the probe while keeping its axis neutral with respect to the sagittal plane laterally enables lateral visualization. Thus, a side-fire probe should remain essentially in the midline, twisting to reach the lateral aspects. This makes patient positioning relatively unimportant, as long as the anus is accessible.
• The end-fire probe: The end-fire probe projects an imaging plane either directly or at a slight angle from the end of the probe. The probe handle must therefore be directed away from the side of interest to visualize the lateral areas, using the anus as a fulcrum to gain accurate placement (i.e., the handle is moved downward, toward the patient's dependent left side, to visualize the right side of the prostate, and vice versa). The patient must be positioned with the buttocks on the edge of the examination table to allow the probe handle to be dropped far enough to reach beneath the plane of the examination table when the right lateral border of the prostate is visualized. This is most readily accomplished if the buttocks are positioned directly over the edge of the table.

Either type of probe allows optimal imaging if the patient's legs are flexed toward his chest and held up by the table extension; this can be facilitated by placing a pillow under one or both legs.

Lateral visualization is more readily achieved with the end-fire probe.

With the end-fire probe, the needle exits its guide in a trajectory more directly toward the prostate instead of tangentially. This allows easier biopsy of the apex and anterior horn of the peripheral zone, further minimizing the possibility of a false-negative biopsy result.

The pain of intrarectal probe placement has traditionally been overlooked. Most modern ultrasound probes are reasonably sized—some no larger than an examining finger—so size alone does not fully account for the associated discomfort. However, biopsy guides and irregularly shaped probes may be relevant factors.

Lubrication during probe placement is essential as there is an obvious value in minimizing friction against the rectal mucosa.

Probe placement should be controlled, with real-time assessment of patient comfort.

• Apply light but slowly increasing pressure against the probe as its tapered end dilates the sphincter during entry. The probe should point in the direction of the rectal course during probe placement. The anal canal may be oriented slightly in varying anatomic directions; this technique allows the probe to find the path of least resistance, thereby minimizing pain.

• Hold the end of the probe between the thumb and forefinger. This allows greater range of motion than does a tight-fisted ("tennis racquet") grip and facilitates the biopsy procedure for the surgeon.

• Ask the patient to breathe in and out slowly or to bear down in a manner similar to having a bowel movement.

• Gentle finger dilation followed by a change of examination glove can also facilitate sphincter relaxation.

Before PPNB was described, the only reliable method for making a patient comfortable for a prostate biopsy was general or regional anesthesia. Some centers, particularly in Europe, continue to use this approach to a reasonable degree. However, this is not cost-effective for the healthcare system, and may actually present patients with unnecessary risks and inconvenience.

Discomfort can occur at multiple points of the procedure including probe placement, periprostatic administration of local anesthesia, and during the actual biopsy. While PPNB may mitigate against the discomfort during needle biopsy, it does nothing for that experienced secondary to initial probe placement.

Various local agents have been described for intrarectal administration to decrease the discomfort associated with probe placement. These include lidocaine gel, lidocaine-prilocaine cream, glyceryl trinitrate, and diclofenac suppositories. A systematic review and meta-analysis was performed in order to evaluate improvement in pain with the addition of intrarectal local analgesia in combination with PPNB. ^[8]  Of the 18 studies included, 16 of which were randomized controlled trials, a statistically significant difference in pain was seen with the addition of intrarectal local anesthesia in terms of pain related to probe manipulation, PPNB, and needle biopsy (p< 0.001 for all). When evaluating the different types of intrarectal local anesthetics, lidocaine-prilocaine cream was the most effective in pain control.

Topical anesthesia with prilocaine-lidocaine cream can be applied to the anal ring, anal canal, and anterior rectal wall. This agent potentially decreases pain sensation from rectal fibers, but these fibers do not exist above the dentate line in most patients, so they are uninvolved in sensation at most biopsy sites. We do not recommend topical anesthesia without PPNB for this reason. This was also noted in a systematic review and meta-analysis that sought to assess pain scores during TRUS biopsy with intrarectal local anesthesia alone, PPNB alone, or the combination of both. ^[9] While intrarectal local anesthesia significantly reduced pain with probe insertion compared to placebo or control (p = 0.01), it did not decrease the mean overall pain after prostate biopsy to the same extent as compared to PPNB (p< 0.00001). The combination of the two was significantly better at decreasing pain during biopsy than intrarectal local anesthesia alone (p = 0.01).

PPNB via injection of local anesthetic has been the standard of care during TRUS biopsy for many years. Short-acting lidocaine is featured in most of the studies germane to this practice. Lidocaine inhibits voltage-activated sodium channels in pain neurons and therefore prevents depolarization and transmission of pain signals. ^[10]  Prior transrectal local anesthetic administration may decrease the discomfort related to initial administration of this medication. In addition, timing between administration of the PPNB and biopsy may further improve patient pain and discomfort, as seen in a study by Pathak et al. ^[11] In the study, 80 patients underwent standard 12 core prostate biopsy and had either a 2- or 10-minute delay between administration of the PPNB and the biopsy. Pain, as measured by the visual analog scale, was significantly higher for the 2-minute group (p = 0.025). It does not seem that the addition of MRI-guided fusion biopsies to the standard TRUS-guided prostate biopsy causes increased discomfort in the setting of a lidocaine PPNB. ^[12]

All current PPNB techniques are based on the technique originally reported in 1996 by Nash et al. ^[6] Previous authors of this article have described a minimally modified technique, called the Mount Everest technique, which is as follows:

The probe is adjusted to the sagittal plane, with the on-screen biopsy guide operational before placement.

A 22-gauge, 7-inch spinal needle is placed through the biopsy guide channel under ultrasound guidance into the area where the prostatic innervation enters the gland (see below).

The site of a typical injection demonstrating prostatic innervation.

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The probe is angled laterally until the notch between the prostate and the seminal vesicle is visualized. The fat in this notch is present in all patients and creates what the authors call the "Mount Everest sign," (shown below) because it has a white pyramidal appearance. Lidocaine (5 mL) is injected on each side.

White pyramidal site between the prostate and the seminal vesicle laterally is seen on this sagittal ultrasound view. This site is called the "Mount Everest sign" because of its white, peaked appearance created by the fat in this location.

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Successful placement of the needle is confirmed when the injectate causes a separation of the seminal vesicles and prostate from the rectal wall (the ultrasonic wheal, as shown below).

The ultrasonic wheal as described by Soloway and Obek (2000) is seen as a hypoechoic filling of the Mount Everest site dissecting along the nerve to bathe the entire ipsilateral prostatic innervation.

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Directing the anesthetic to the proper plane is facilitated by injecting the anesthetic as the needle enters the space, so as to expand its distance, and then pulling back slightly to open the potential space until anesthetic is seen dissecting caudally, as depicted in the images below. The space between the rectal wall and the prostate widens when the anesthetic dissects this plane. This can be accomplished by an injection at the base, the midgland, or the apex of the prostate.

As the needle enters the Mount Everest space, it closes the space temporarily. Injection during placement of the needle helps prevent the space from closing.

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Continuing to inject as the needle is pulled back into the proper plane causes the space to open up.

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The proper plane is identified by pulling back on the needle when the anesthetic is seen dissecting along the length of the prostate. This approach ensures that the entire periprostatic nerve is bathed in lidocaine, as well as guarantees prostatic anesthesia. The needle helps open the space as it is pulled back, so that the tip of the needle reaches the correct plane, as confirmed by the ultrasonic wheal.

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Ultrasound examination and volume calculation are then performed per routine.

Difficulty finding the Mount Everest notch immediately upon probe placement may be due to inadequate depth of probe placement (easily remediable) or inadequate ultrasound visualization laterally, often because an inexperienced user is twisting the end-fire probe (the technique for the side-fire probe) or angling the side-fire probe (the technique for the end-fire probe), leading to loss of bearing and perspective. In addition, failure to maintain direct contact of the probe against the rectal wall limits visualization and sacrifices the benefits of improved hemostasis through probe tamponade.

Complications

No significant difference was seen on systematic review and meta-analysis regarding the addition of intrarectal local anesthesia administration to PPNB as compared to PPNB alone. ^[8]

The two additional injections through the rectal mucosa during PPNB could increase the risk of infection or bleeding. A single report showed that PPNB was associated with an increase in bacteriuria (including clinical infection in 2 patients), but was also associated with less rectal bleeding. The report attributed the increased bacteriuria to the additional 2 punctures through the rectal mucosa and related the decreased rectal bleeding to lower biopsy-associated discomfort. ^[13]

A prospective study of 200 patients in Turkey reported no major complications and only minor complications with PPNB. The most common finding was pain due to puncture with the needle used for local anesthesia (27%). Other complications recorded included the need for repeated injections during biopsy (4.5%), symptoms associated with systemic lidocaine toxicity (2%), urinary incontinence (1.5%), and degradation of the image resolution due to anesthetic injection (1%). Increased vascularization within the periprostatic region was uncommon (2%) at 2-week follow-up examination. ^[14]

Injection into the area of the periprostatic nerves could complicate nerve sparing during radical retropubic prostatectomy. Though the literature is sparse for this specific area, this type of difficulty has not been noted. ^[15]

Soloway and Obek (2000) described the ultrasonic wheal as the visualization of anesthetic into the area of the periprostatic nerve bundle and suggested that 3 separate injections on each side ensured adequate anesthesia. The ultrasonic wheal should provide nerve blockade whenever the entire nerve bundle adjacent to the prostate is bathed in local anesthesia, regardless of where the injection is performed, as long as the injectate dissects along the course of the nerve.

Attempts to inject at the level of the lateral apex or directly into the apex have been based on the observation that apical biopsy is more painful than biopsy of the other areas of the gland. When the authors query attendees at continuing medical education (CME) courses, this observation is confirmed by essentially all urologists. However, the reason for this increased pain in the apex was not understood until 2003, when Jones and Zippe reported that this pain appeared to be related to stimulation of anal pain fibers, not the apex itself. ^[16] By performing the rectal sensation test (see below), the apical pain fibers may be bypassed to achieve a painless apical biopsy.

Apical biopsy is crucial because of the notable incidence of cancers in this location, especially in the anterior portion. This area is named the anterior horn because of its beaked appearance as it wraps around the transition zone. Studies by Meng et al and others indicate that the anterior horn is the most likely site of cancer that has been missed during a previous biopsy with a false-negative result. ^[17] This missed diagnosis may be a result of two factors: (1) the anterior horn is difficult to reach, especially with side-fire probes because of their tangential needle tract, and (2) the general perception by urologists is that biopsy of the apex is more painful than biopsy of other areas of the prostate, so some urologists may avoid the area in exchange for improved patient tolerance.

The dentate line is identified with the rectal sensation test (see the image below). During this test, the needle is lightly applied against mucosa. It is immediately and strikingly obvious, upon even light touch, if anal pain fibers are present at this level. If the patient answers affirmatively that he feels sharpness, the needle is repositioned 1-2 mm higher until an insensate area is reached (see the second image below). In most cases, the patient does not need to state such perception, as the pain is enough to elicit movement with even a light touch of the needle.

Increased pain during apical biopsy is caused by piercing of anal pain fibers below the dentate line.

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The patient feels the sharp tip of the needle when it touches the intensely sensitive anal pain fibers. Marching 1-2 mm cephalad allows the needle to reach an insensate area above the dentate line. However, this approach often results in the needle being pointed at the mid gland instead of the apex.

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When the needle is advanced cranially above the dentate line, the trajectory is often toward the mid gland, precluding adequate apical biopsy. This needle trajectory is especially problematic because of the need to collect biopsy samples from the anterior horn or peripheral zone tissue.

Angling the probe handle craniodorsally, as shown below, allows the needle to pull rectal mucosa caudally. Painless apical biopsy may then be performed, bypassing the sensory fibers below the dentate line. This action must be performed carefully to avoid dragging the needle against hemorrhoidal vessels in the rectum, which could lead to excessive bleeding. Using the needle tip as the fulcrum, instead of dragging, allows for safe and painless apical biopsy.

Once above the sensate limit of the dentate line, the needle may be advanced through mucosa painlessly. The probe can be rotated as shown, taking care not to drag the needle against the mucosa, so as to obtain a painless apical biopsy sample.

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VAS pain scores for apical biopsy in patients who have already undergone PPNB show improvement over those without, from a score of 2.28 to a score of 1.25. ^[16] The implications of these anatomic observations are obvious for PPNB at the level of the apex (see the image below).

The apex is entirely composed of peripheral zone tissue, where cancer is most likely to occur. The importance of obtaining a properly placed biopsy sample at this location is demonstrated.

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One randomized study demonstrated equivalent level of pain control with apical lidocaine block using only 5 mL of injectable lidocaine when compared to two injections of 5 mL lidocaine injected at either base. ^[18] This same group also randomized patients to receive an additional intraprostatic dose of injectable lidocaine, and they showed a statistically significant improvement in visual analog pain scales. ^[19] At this time, the authors recommend either of these techniques as an adjunct to injection at the prostate base as described.

PPNB for TRUS biopsy is the current standard of care based on a considerable body of evidence. The addition of intrarectal topical anesthesia can be considered, primarily to lessen the discomfort related to initial probe placement. As with all procedures in which the patient is fully conscious, making the environment and procedure as comfortable as possible is of paramount importance.