Urethrogram 

Overview

A retrograde urethrogram (RUG) is a diagnostic procedure performed most commonly in male patients to diagnose urethral pathology such as trauma to the urethra or urethral stricture.[1, 2]

Introduction

Urethrography is most commonly performed via the retrograde injection of radiopaque contrast into the urethra to elucidate urethral pathology such as rupture of the urethra from trauma or urethral stricture. It is a commonly used procedure in reconstructive urology for operative planning as well as a follow-up procedure after urethral reconstruction. The procedure is less invasive than other diagnostic techniques to examine the urethra, such as urethroscopy.

Indications

Trauma

The most common indication for a RUG in the setting of trauma is the presence of blood at the urethral meatus after blunt or penetrating trauma. Penile fracture with gross hematuria is also an indication for a RUG to elucidate the presence of a urethral injury. Another relative indication for a RUG is the finding of a “floating prostate” on digital rectal examination, which may indicate urethral disruption. (The prostate normally feels fixed on digital rectal examination, and if the prostate is mobile or “floating,” a urethral disruption may have occurred.) A RUG would diagnose the nature of the injury.

Lower urinary tract symptoms

Male patients with a previous history of urethral stricture who have symptoms of urinary urgency, urinary frequency, and poor bladder emptying are at risk for a urethral stricture.

Postoperative evaluation

A RUG is often performed for the imaging and evaluation of the urethral after a surgical procedure such a urethroplasty.[3]

Contraindications

Relative contraindications to RUG is a patient allergic to radiopaque contrast. However, because a properly performed RUG does not inject contrast into the vascular system, some practitioners may proceed carefully with RUG in these patients. Premedication with steroids, histamine-1 receptor blockers (such as cimetidine) and histamine-2 receptor blockers (such as Benadryl) may be given preoperatively to decrease the chance of allergic reaction. The procedure should not be performed with patients who have an active urinary tract infection.

Anesthesia

In most cases a retrograde urethrogram (RUG) can be performed without anesthesia. The instillation of lidocaine gel into the urethra is one possible local anesthetic option but is usually not used. In cases of urethral disruption, this would cause extravasation of the anesthetic jelly into the surrounding tissue. In cases of urethral stricture, energetic installation of jelly can dissect the urethral stricture in a way that makes subsequent instrumentation more difficult, so it is generally avoided.

Equipment

See the list below:

• Radiopaque contrast such as iothalamate meglumine 17.2% (Cysto-Conray II, Mallinckrodt Inc, St Louis, MO)

• Fluoroscopic x-ray machine

• 16-F or 18-F Foley catheter

• Catheter tip syringe

• 5 mL syringe to fill the Foley catheter balloon

Optional equipment: The Brodney or Knudsen clamps are specially made devices designed to perform RUG. They are generally unnecessary.

Positioning

The patient should be positioned obliquely at 45 º with the bottom leg flexed 90 º at the knee and the top leg kept straight. Alternatively, the patient can be supine and, if using a fluoroscopic C-arm, the C-arm can be rotated in the vertical plane 45 º degrees (see image below).

This is the setup for a retrograde urethrogram for a suspected urethral stricture. Note the C-arm fluoroscopy centered over the urethra of a patient in a supine position.

Complication prevention

Contrast extravasation is a preventable complication when excessive pressure is applied when instilling contrast into the urethra, causing extravasation of radio opaque contrast into the surrounding tissue. This complication can be easily prevented by applying only enough pressure to fill the urethral lumen with contrast.

A study by Malhotra et al that included 42 patients who underwent 47 retrograde urethrograms reported that the risk of post-procedural urinary tract infection after retrograde urethrogram was low and that in this study, antibiotic prophylaxis was unrelated pre-retrograde urethrogram UTI.[4]

Overview

The patient is placed in the position stated above (see the Preparation section). The fluoroscopic C-arm is positioned over the patients pelvis with the center focused just below the pubic bone. A 16-F or 18-F Foley catheter is flushed with radiopaque contrast to remove any air bubbles. The penile glans and urethral meatus should be cleaned with antiseptic. The Foley catheter is then placed just inside the urethral meatus so that the Foley catheter balloon rests in the fossa navicularis.

With the Foley in position, the catheter balloon is filled with 1-2 mL of radiopaque contrast or saline solution. Overfilling must be avoided, or it will rupture the distal urethra. (A conscious patient can be asked to alert the operator if pain accompanies balloon filling). The operator then pulls the penis laterally to straighten the urethra, grasping the penis as distally as possible, and distal to the inflated balloon. The catheter-tipped syringe is then filled with approximately 50 mL of radiopaque contrast, and 20-30 mL of contrast is injected in a retrograde fashion. Taking a preinjection “scout” film of the urethra to compare the RUG images is important. Static images of the urethra are taken during retrograde injection of radiopaque contrast (see the videos and image below).

X-ray viewing setup for a retrograde urethrogram with a scout image on the screen.

Image interpretation

Normal retrograde urethrogram (RUG): If the radiopaque contrast is injected properly, the entire anterior and posterior urethra should be filled with contrast and seen to jet into the bladder neck. The verumontanum is seen as an ovoid filling defect in the posterior urethra (see the image below). The distal end of the verumontanum marks the proximal boundary of the membranous urethra and constitutes the 1 cm of urethra that passes through the urogenital diaphragm.[5]

Normal retrograde urethrogram. Image used with permission from Kawashima A, Sandler C M, Wasserman N F, et al. Imaging of urethral disease: a pictorial review. Radiographics 2004;24:S195-S216.

Urethral trauma: If blunt or penetrating trauma has injured the urethra and a RUG is performed, leakage of urine often occurs (see the image below). Injuries are often described as involving the anterior urethra (consisting of the penile and bulbar urethra) or the posterior urethra (consisting of the membranous and prostatic urethra).

Retrograde urethrogram with extravasation of contrast at site of posterior urethral injury.

Urethral stricture: When a RUG is used to evaluate for urethral stricture, the image often illustrates a narrowed lumen in the anterior urethra (see the image below).

Anterior urethral stricture. Retrograde urethrogram reveals a segment of narrowing in the distal bulbous urethra with opacification of the left Cowper duct (arrow). Image used with permission from Kawashima A, Sandler C M, Wasserman N F, et al. Imaging of urethral disease: a pictorial review. Radiographics 2004;24:S195-S216.

A study by Bach et al compared the accuracy of retrograde urethrogram (RUG) interpretation between the primary physician performing the procedure and the independent physician interpreting the films to evaluate the suitability of relying on independent physician interpretations for the purposes of preoperative urethral stricture surgery planning. The study reported that independently reported RUGs are not as accurate as primary physician-reported RUGs.[6]

Complications

Contrast extravasation is an uncommon complication of a RUG. It generally occurs when excessive force is applied when injecting contrast into the urethra, or when too much fluid is placed in the balloon—rupturing the urethra. This results in extravasation of contrast into the surrounding tissue of the urethra.[7]

Patient Education

Ohio State University Health for Life: Retrograde urethrogram.

Medication summary

See the list below:

• Radiopaque contrast such as iothalamate meglumine 17.2% (Cysto-Conray II, Mallinckrodt Inc, St Louis, MO)

Medical devices

See the list below:

• As stated above, a Brodney or Knudsen clamp can be used to provide a better seal at the urethral meatus for a retrograde urethrogram (RUG), but it is often cumbersome and not necessary for adequate imaging.