Definition of Retrograde Urethrography (RGU)
Retrograde Urethrography (RGU) is a diagnostic radiological procedure used to visualize the male urethra. It involves the injection of a water-soluble opaque (radiocontrast) medium directly into the external urethral meatus, flowing backward (retrograde) against the normal flow of urine. As the contrast medium fills the urethral lumen, fluoroscopic imaging or static radiographs are obtained to evaluate its anatomy, patency, and identify potential abnormalities such as strictures, trauma, fistulas, diverticula, or tumors. RGU is a standard tool in urology and radiology departments for the assessment of various urethral pathologies.
Indications for Retrograde Urethrography
RGU is indicated for the investigation and diagnosis of suspected or known conditions affecting the male urethra. Common indications include:
- Urethral Strictures: The most frequent indication, used to identify the location, length, and severity of urethral narrowing.
- Urethral Trauma: Evaluation following pelvic fractures, straddle injuries, or penetrating trauma to assess for rupture or perforation.
- Fistulas: Identification and mapping of abnormal connections between the urethra and other organs (e.g., skin, rectum, vagina – although less common in males, urethrocutaneous or urethrorectal fistulas can occur).
- Diverticula: Visualization of abnormal pouches or sacs protruding from the urethral wall.
- Congenital Abnormalities: Assessment of urethral anomalies present from birth, such as hypospadias (after repair), epispadias, or urethral valves (though voiding cystourethrography is often primary for valves).
- Assessment Prior to Surgery: Mapping the urethra before reconstructive procedures like urethroplasty.
- Investigation of Urethral Masses or Tumors: Helping to define the extent and location of suspected neoplasms.
- Difficulty with Urethral Catheterization: Identifying anatomical blockages or strictures preventing catheter insertion.
- Evaluation of Chronic Urethritis or Inflammation: Assessing the long-term effects of infection or inflammation on urethral structure.
- Foreign Bodies: Localization of foreign objects within the urethra.
Contraindications for Retrograde Urethrography
While a generally safe procedure, RGU has certain contraindications:
- Active Urinary Tract Infection (UTI): There is a risk of introducing bacteria deeper into the urinary tract or bloodstream, potentially leading to epididymitis, prostatitis, or sepsis. The procedure should ideally be postponed until the infection is treated.
- Known Severe Allergy to Iodinated Contrast Medium: A history of severe anaphylactic reaction to contrast agents is a significant contraindication. Premedication protocols may be considered for lesser reactions or when the study is essential, but careful risk assessment is required.
- Acute Urethral Bleeding (Significant): While minor bleeding might not preclude the study, injecting contrast into an actively bleeding urethra can be painful, obscure findings, and potentially increase the risk of contrast extravasation. Evaluation for significant trauma should ideally precede the procedure if trauma is suspected.
- Recent Urethral Instrumentation or Surgery: Depending on the specific procedure and time elapsed, recent instrumentation might cause mucosal edema or potential for injury or infection. Clinical judgment is needed.
- Pregnancy: Due to the use of ionizing radiation (X-rays), RGU is generally contraindicated in pregnant women. The risks to the fetus must be weighed against the necessity of the examination.
Equipment Used
Performing an RGU requires specific equipment to ensure a sterile, effective, and safe procedure:
- Fluoroscopy Unit: Essential for real-time visualization of contrast flow and accurate timing of image acquisition. A C-arm or fixed fluoroscopy table can be used.
- Radiographic Table: With tilting and angulation capabilities to position the patient correctly for oblique views.
- Sterile Instrument Tray: Containing necessary sterile items.
- Sterile Gloves and Drapes: To maintain an aseptic field.
- Antiseptic Solution: Such as povidone-iodine or chlorhexidine solution, for cleaning the genitalia.
- Local Anesthetic Gel: Lignocaine (lidocaine) gel (typically 2% or 2.5%) applied intra-urethrally for pain relief.
- Syringe: A large syringe (e.g., 20 ml or 50 ml) for injecting contrast.
- Urethral Catheter or Clamp:
- Brodney Clamp: A specialized clamp designed for RGU in males, fitting over the glans penis to create a watertight seal around the meatus, allowing hands-free injection.
- Small Foley Catheter (e.g., 8-10 Fr): Can be inserted just into the meatus, with the balloon inflated minimaly to create a seal.
- Cone-shaped tip or adaptor: May be used with a syringe.
- Connecting Tubing: Optional, between the syringe and catheter/clamp.
- Contrast Media: (See section 5).
- Gauze Swabs: For cleaning and handling.
- Receiver Dish or Basin: To catch any overflow or leakage of contrast.
- Lead Aprons and Thyroid Shields: For radiation protection of staff.
- Emergency Equipment: Including medications and equipment to manage contrast reactions or other emergencies.
Contrast Media
The contrast medium used for RGU must be:
- Water-Soluble: This is crucial. Oil-based contrast media should never be used in the urethra due to the risk of granuloma formation if extravasation occurs.
- Iodinated: Contains iodine atoms that absorb X-rays, making the urethra visible.
- Typically Low Concentration (Dilute): Often diluted to 30-60% concentration (e.g., Iohexol 300/350 diluted with sterile water or saline). Dilution makes the contrast less viscous, easier to inject, reduces potential for irritation or pain, and allows for better visualization of subtle mucosal details compared to dense, undiluted contrast which can “white out” small lesions.
- Volume: The amount required varies but is typically between 10 ml and 30 ml, depending on the patient’s anatomy and the extent of filling needed to reach the bladder neck. It’s important to inject enough volume to distend the urethra adequately but not so much that it refluxes into the bladder immediately, obscuring the posterior urethra.
Procedure/Technique for Retrograde Urethrography with Filming
The RGU procedure is performed under strict aseptic conditions, typically in a fluoroscopy suite.
- Patient Preparation and Positioning:
- Explain the procedure to the patient, addressing any concerns.
- Obtain informed consent if institutional policy requires it.
- Confirm no contraindications are present (e.g., active UTI, severe allergies).
- Instruct the patient to empty their bladder completely before the procedure. A full bladder can impede visualization of the proximal urethra and prostate.
- Position the patient supine on the fluoroscopy table.
- For optimal visualization of the entire urethra, especially the bulbous and membranous portions, the patient is typically positioned in an oblique view. This involves rotating the patient approximately 30-45 degrees towards the side being examined (usually the side away from the image receptor or towards the radiographer). This projects the mobile anterior urethra (penile and bulbous) away from the bony pelvis, stretching and straightening it.
- Aseptic Preparation:
- The radiographer or clinician cleans the external genitalia thoroughly with an antiseptic solution.
- Sterile drapes are applied to isolate the area, creating a sterile field.
- Anesthesia:
- Lignocaine (lidocaine) gel is instilled slowly into the urethra using a sterile syringe or a special applicator tip.
- The external meatus is often held closed for a few minutes to retain the gel and allow it to spread and provide adequate local anesthesia. This significantly improves patient comfort during contrast injection.
- Catheter/Clamp Placement and Seal:
- Once the anesthetic has taken effect, the chosen method for creating a seal is applied.
- If using a Brodney clamp, it is carefully placed over the glans penis, securing the meatus and allowing attachment of the contrast-filled syringe or tubing.
- If using a small catheter, the tip is inserted just into the meatus, and the balloon is inflated minimally (usually <1 ml) just enough to create a seal without causing significant distension or trauma.
- A syringe tip alone can sometimes be used, but requires continuous pressure from the operator to maintain the seal.
- Contrast Injection and Fluoroscopic Monitoring:
- The syringe containing the prepared contrast medium is attached to the clamp or catheter.
- Contrast is injected slowly and steadily. Slow injection (e.g., 5-10 ml over 30-60 seconds) allows the urethra to fill completely and distend naturally, highlighting subtle irregularities. Rapid injection can cause spasm, pain, and premature reflux into the bladder.
- The injection is monitored continuously under fluoroscopy. This allows the operator to see the flow of contrast, identify filling defects, strictures, or extravasation in real-time, and adjust the injection rate or volume as needed.
- Filming (Image Acquisition):
- Images are acquired during the contrast injection under fluoroscopic guidance.
- The primary view is the oblique projection (ipsilateral side down). This view is critical for visualizing the entire urethra, especially the bulbous and membranous urethra, which are often obscured by the symphysis pubis on AP views. The oblique view ‘straightens’ the urethra and projects it away from bone. Multiple oblique images may be taken as contrast fills different segments.
- Lateral views may occasionally be obtained to further assess the membranous urethra and sphincter region or to confirm findings seen on oblique views.
- AP views are generally less informative for the anterior and bulbous urethra but may be helpful for evaluating the prostatic urethra and bladder neck, especially if reflux into the bladder occurs or if a subsequent voiding image (VCUG) is planned.
- Dynamic imaging (cine or video clips) is often recorded during the injection to assess the dynamic flow of contrast, urethral peristalsis (if present), and the rigidity or elasticity of strictures.
- Images should capture the contrast filling the urethra from the meatus proximally to at least the level of the external sphincter, and ideally into the prostatic urethra. If the study is combined with a VCUG, images are taken as the bladder fills and during voiding.
- Ensure adequate penetration and positioning on the images to visualize the entire urethra clearly against the surrounding bony structures.
- Completion:
- Once sufficient images are obtained and the radiologist is satisfied, the contrast injection is stopped.
- The clamp or catheter is carefully removed.
- Any spilled contrast is cleaned from the patient.
- The patient is informed that the procedure is complete. The patient may be asked to attempt voiding if a VCUG is planned or if contrast has entered the bladder.
Complications
While RGU is generally safe, potential complications can occur:
- Pain or Discomfort: Common during contrast injection or catheter/gel insertion, usually mild and transient, often managed by anesthetic gel.
- Urinary Tract Infection (UTI): Risk of introducing bacteria into the urethra or bladder, especially if aseptic technique is compromised or if there is pre-existing infection. Can progress to epididymitis or prostatitis in males.
- Contrast Extravasation: Leakage of contrast outside the urethral lumen. Usually benign with water-soluble contrast unless due to significant urethral rupture, but can cause local swelling and discomfort.
- Urethral Injury or Perforation: Rare, particularly with gentle technique, slow injection, and appropriate catheter/clamp use. Risk is higher in inflamed or strictly stenotic urethras. Can lead to pain, bleeding, infection, and the need for further intervention.
- Allergic Reaction to Contrast: Ranges from mild (hives, itching) to moderate (bronchospasm, angioedema) to severe (anaphylaxis). Experienced staff and emergency equipment must be available.
- Vasovagal Reaction: Fainting or lightheadedness due to anxiety or pain.
- Transient Hematuria: Mild, short-lived bleeding after the procedure.
Aftercare
Following an RGU, patients should receive clear instructions:
- Fluid Intake: Encourage increased fluid intake for the next 24 hours. This helps to flush the contrast medium out of the urinary tract and can reduce the risk of post-procedure discomfort or infection.
- Potential Symptoms: Inform the patient that they may experience some mild burning or stinging sensation during urination for the first few voids after the procedure. The urine may also appear slightly pink or discolored due to residual contrast or minor irritation. These symptoms should subside quickly.
- Warning Signs: Advise the patient to contact their healthcare provider if they experience persistent or severe pain, significant bleeding (more than just a few drops), difficulty urinating (retention), fever, chills, or signs of infection.
- Antibiotic Prophylaxis: In certain cases, such as patients with a history of recurrent UTIs, prosthetic implants, or significant strictures, the physician may prescribe a single dose or short course of antibiotics to minimize the risk of infection.
- Results: Explain how and when the patient will receive the results of the examination and discuss any necessary follow-up appointments.
In conclusion, Retrograde Urethrography is a valuable diagnostic tool for evaluating the male urethra. Understanding the indications, contraindications, necessary equipment, proper technique, potential complications, and appropriate aftercare is essential for performing the procedure safely and effectively, ensuring optimal diagnostic outcomes for the patient.
