Dr David McCreary
Emergency Fellow

 

Pelvic fractures are pretty common, particularly if you work in a trauma centre. From a trauma resuscitation perspective, we’re usually most concerned with whether a pelvic injury is unstable with disruption of the pelvic ring, and if there is active arterial bleeding. When our patients are haemodynamically behaving themselves, and don’t have active bleeding we can take a breath and relax and think about, amongst other things, getting a urinary catheter in the patient…and that’s when we should be thinking about a retrograde urethrogram (RUG). This came up in a few discussions in our Grand Rounds sessions last year, so I thought it would be useful to do a quick refresher on the technique.

Why is it important?
  • Urethral injury is a common complication, up to 24%, of pelvic fractures
  • Bad if missed (just ask a urologist – they hate managing urethral strictures)
  • Can be made worse with insertion of a urinary catheter (partial tear = bad. Poking at it can cause it to become a complete transection = very bad)
Who should get it?

Firstly, men. 97% of urethral injuries occur in male patients(1) due to the shorter female urethra being less prone to shearing stresses. If you think there are signs of urethral injury in a female patient (approx. 80% are associated with vaginal laceration or blood at the introitus(2)) – skip the RUG and get the urologists involved.

Back to the blokes, if you remember back to your ATLS/EMST course they quote:

  • Gross haematuria
  • Inability to void
  • Unstable pelvic fractures (particularly with symphysis diastasis(1), straddle fractures and Malgaigne fractures)
  • Blood at urethral meatus
  • Scrotal haematoma
  • Perineal ecchymoses
  • High riding prostate

Any of the above and you should be checking out that urethra.

Now, I remember quoting the above list in my first ATLS course (In 2009? Oh my.), but as fresh-faced PGY-2 I’ll admit thinking of it as some difficult, fancy imaging technique that I would need to beg some clever radiologist to perform, I had no idea that it was actually pretty easy and could be done in a trauma bay using the overhead X-Ray.

Anatomy

Before looking at the technique, it’s worth having a refresh on the anatomy, just so we know what we’re looking for.

The male urethra has 4 Parts:

Anteriorly:

  • Penile
  • Bulbous

Posteriorly: (Most common injury – up to 25% of pelvic fractures)

  • Membranous
  • Prostatic
OK, so how do I do it?

Technique:

  • Get some (water soluble) contrast media from radiology
  • Place patient in 25–30-degree oblique position
    • Having a pelvic fracture patient in an oblique position is a challenge – the fluoroscopy / X-Ray can be aimed from an oblique position, with the penis positioned appropriately to allow visualisation of the entire urethra
  • Insert Foley catheter 2-3cm into meatus and inflate balloon with 2-3ml of water, stretch the penis to straighten the urethra, hold catheter in place.
  • Inject 20-30ml of undiluted, sterile, water soluble contrast
    • Take X-ray image every 10 mls
    • Be careful not to spill – it’ll mess up your images and give false positives or unequivocal tests
  • If images show intact urethra:
    • Deflate balloon
    • Advance Foley into bladder and inflate balloon with 10ml water
      • If images show injury, or equivocal or if advancement of foley causes pain or resistance is met – stop advancing and chat to your friendly neighbourhood pee-pee surgeon
What would abnormal findings look like?
  • Intravasation of contrast
  • Urethral occlusion (failure of dye to enter the bladder)

But what does that actually look like?

First, a normal test to get your sights in

Normal Retrograde Urethrogram

(Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 61843)

Now an abnormal test
  • Note the venous intravasation of contrast that has escaped through a urethral defect.

Abormal Retrograde Urethrogram

(Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 61843)

Injury Classification

Now for sprinkles on top of our required knowledge, urethral injuries can be classified by a couple of systems: the AAST and the Goldman Classification. For our purposes the AAST is more straightforward, but Goldman as apparently more widely accepted, so I’ll include them both.

AAST System
The Goldman System

(My super-mature way to remember the name is that urine is, or at least should be, golden and we’re doing this test in men):

Why does classification matter?
  • Grade I: May be conservatively managed.
  • Grades II-V: usually result in severe stricture and so urology may take for immediate surgery
    Take homes?
    • Consider urethral injury with pelvic fracture, particularly if you have symphysis diastasis
    • Have a really low threshold to do RUG
    • It’s really a lot easier than you think
    • If in doubt on results, or if your patient is female, get a urology opinion

    References / Further Reading:

    1. Lückhoff C, Mitra B, Cameron PA, Fitzgerald M, Royce P. The diagnosis of acute urethral trauma. Injury. 2011 Sep;42(9):913–6. DOI: 10.1016/j.injury.2010.08.007 PMID:  20739022
    2. The Royal Melbourne Hospital guideline is great, with some useful flow charts.
    3. This review is where I got a lot of this from and has some great learning points (Ingram MD, Watson SG, Skippage PL, Patel U. Urethral Injuries after Pelvic Trauma: Evaluation with Urethrography. RadioGraphics. 2008 Oct;28(6):1631–43.)
    4. Radiopaedia, as always have a nice summary with some more pictures
    5. A comprehensive, if a little dull, video summary on youtube
    David McCreary

    David McCreary

    Emergency Fellow, Alfred Health

    Dave is an Emergency Physician who completed training between the UK and Australia and completed an MSc in Trauma Science with QMUL. His clinical interests include trauma, critical care, evidence based medicine and human factors. Dave is a regular contributor the RCEMLearning podcast and is a FOAMed editor for RCEMLearning. He dislikes coriander, decaff coffee and dermatology.