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Urethral Injury-Ascending Urethrogram

posted Jul 31, 2010, 3:17 AM by Amila Ratnayake   [ updated Jul 31, 2010, 5:09 AM ]



This is a combined RUG & voiding study in a middle age man who presented after fallen astride and retention of urine . Examination reveled blood at the meatus and perineal heamatoma. The study confirmed injury to the bulbar urethra with contrast extravasation.
Anatomy- The male urethra is divided into four anatomical regions

Anatomy of the male urethra


For treatment purposes male urethral injuries are classified into two groups.
  1. Posterior urethra- Prostate & Membranous
  2. Anterior urethra- Bulbar & Penile 
Injury Mechanism (posterior urethra)- Strong shearing forces in high speed blunt or crush injuries or high velocity penetrating trauma tear the attachments of the prostate and pubo-prostatic ligament from the pelvic floor. This mobilizes the prostate and bladder , a haematoma develops inferior to the prostate is then driven cephalad by the collecting haematoma but the posterior urethra is firmly fixed to pubic arch by the perineal membrane. This results in rupture of the urethra at varying locations.
pelvic fracture is present in greater than 90% of patients.
Urethral injury is a common complication after pelvic trauma. It occurs in as many as 24% adults with pelvic fracture.
Anterior urethra- Injury to anterior urethra seen in minority of patients, more commonly it is the result of straddle incidents, in which the patient falls on the cross-bar of a bike or top of a fence. This compresses the corpora spongiosum and bulbous urethra against the pubic symphysis disrupting the urethra.

Investigations- If clinically suspected presence of urethral trauma should be investigated by retrograde urethrogram. ( RUG ).RUG provides information on the presence , location and severity of urethral extravasation.
Initial anterior posterior ( AP ) film of the pelvic serves to identify pelvic fractures, bony displacement of the symphysis or the presence of foreign objects.
Cross sectional imaging modalities, including ultrasonography , magnetic resonance imaging and computer tomography are useful for evaluating periurethral structures.
Limitations of RUG.- It provides limited information about the details of surrounding soft tissue injury. Imaging of the proximal urethra can be inadequate.
In delayed setting a retrograde study is the most appropriate way to evaluate the anterior part of the urethra and voiding study is the most appropriate way to evaluate the posterior part of the urethra. Therefore dynamic urethrography represent a synergy of these two imaging techniques.

Technique- This utilizes a foley catheter and patient is positioned 45 degrees oblique angle with the penis stretched so that the meatus point cephalad. This provides a C configuration from the bladder level to meatus tip. If the penile shaft points caudal the femur may obscure the opacified urethra. If this position unobtainable patient should be supine with the penis stretched perpendicular to the leg. In this technique the urethra can appear foreshortened allowing for possible error in interpretation of extravasation.
The foley catheter is placed inside the urethra with the baloon inflated with 1 to 2 ml of water in the fossae navicularis. Approximately 20 to 30 ml of 30% contrast material are injected into the urethra. In the most ideal condition, the entire procedure should be performed under fluoroscopic control.
The bulbo-membranous junction can be arbitrarily localized where imaginary line connecting the inferior margin of the obturator foramina intersects the urethra.

Grading of the blunt urethral trauma- The most accepted ,unified classification of the RUG findings for urethralminjury is the Goldman classification . This is modified extended version of the previous Colapinto- McCallum system. It is based on the anatomical findings of the injury, not on its mechanism.  

 Type Injury description Picture
 1 Intact but stretched posterior urethra. Pic 1
 11 tear of the membranous urethra above the urogenital diaphragamPic 2 
 111 Combined anterior & posterior urethral injury with disruption of urogenital diaphragam Pic 3
 1V Bladder neck injury extending to urethra. Injury of the base of the bladder with periurethral extrvasation may simulate a type 1V injury and classified as type 1V-A Pic 4
 V Partial or complete pure anterior urethral injury Pic 5
 

Pictorial veiw-Goldman classification


Type 11,111 and V urethral injuries further classified as a partial or complete urethral tear with RUG. Partial tear are diagnosed when extravasation of contrast material occurs with the presence of contrast material in the bladder. Complete tears are diagnosed by extravasation without contrast agent in the bladder or in the proximal torn end of the urethra.

References-
  1. Akira Kawashima, Carl M Sandler, neil F Wasserman, AndrewJ Leroy, Bernard F King Jr, Stanford M Goldman. Imaging of the urethral disease. A pictorial review. Radiographics.Oct 2004; 24: S 195- S 216
  2. Colapinto V, McCallum R W. Injury to the male urethra in fractured pelvis. A new classification. J Urol. 1977 Oct ; 118(4) : 575-80.
  3. Goldman S M, Sandler C M , Corriere J N , Mc Guire E J. Blunt urethral trauma. A unified anatomical mechanical classification. J Urol 1997 jan ; 157(1): 85-9
  4. Mark D Ingram, Sarah G Watson, Philip L Skippage, Uday Patel. Urethral injuries after pelvic trauma. Evaluation with urethrography. Radiographycs ; Oct 2008 . 28: 1631-1643

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