Anterior urethra mucosal dissection and contrast medium urethro-venous intravasation

An 87-year-old man with a history of benign prostatic hyperplasia (BPH), nephrolithiasis and bladder lithiasis was diagnosed with lower limb acute ischaemia.  After several failed attempts of pre-operative catheterisation, a suprapubic cystostomy was performed. The urethral obstruction was evaluated with retrograde urethrography (RUG). The patient complained chronic weak stream micturition and urinary sediment.

During retrograde urethrography - using diluted iodinated contrast medium and penile clamp device - the anterior urethra was regularly opacified, without opacification of posterior tract (Fig. 1).  Trying to delineate the obstruction, some tortuous periurethral and pelvic structures were transiently opacified (Fig. 2).  In consideration of the patient’s history and to rule out a urethral injury, a CT evaluation was also performed. In basal scans, opacified urine was present in the renal pelvis on both sides (Fig. 3) and, in a small amount, in the bladder.
The presence of bladder stones was confirmed, with some of them apparently incuneated in the bladder neck and prostatic urethra, with a markedly enlarged prostate.  Dynamic CT was performed during and immediately after urethral opacification and contrast medium extravasation was confirmed between the dissected mucosal and submucosal planes (Fig. 4). Its drainage in the local venous system caused opacification of the tortuous periurethral submucosal veins and the inferior hypogastric plexus bilaterally (Fig. 5).

Urethro-venous intravasation (UVI) or urethro-vascular reflux (UVR) consists of the outflow of contrast medium from the urethra into the highly vascular, elastic-rich, submucosal stroma and its drainage into local vascular structures, thus delineating a “venogram” of the penile plexus and pelvic-ascending venous-vascular pathways. The phenomenon is probably due to inflammatory micro-lesions or macroscopic iatrogenic breaches of the mucosal integrity.  UVI rarely occurs while performing retrograde urethrography (its incidence is reported approximately around 1% [1,2,3]) and may lead to some complications, which should be considered [1,2].

In our case, the pathophysiology of the radiological findings is probably due to prior urethral instrumentation with mucosal damage. Obstruction of the posterior urethra, caused by combined BPH and presence of incuneated urinary stones, led to a rise in the pressure of the injected contrast medium, which could then infiltrate the pre-existing mucosal lesions. The contrast would, therefore, gather under the dissected mucosa, with no extravasation into the corpus spongiosum (Fig. 4). Being drained by the local venous plexus, the contrast medium would then be rapidly cleared from the local extravasation site and enter the systemic circle, delineating an ascending venous pathway (Fig. 5). This could explain the only rapidly transient presence of extravasation in the radiographic images acquired. As shown by our basal CT scans, however, the contrast medium was filtered and excreted by the kidneys, leading to opacification of the urinary tract, with a descending gradient (Fig. 3) which could not be explained by vescico-ureteral reflux (VUR).  These findings were clearly demonstrated at the dynamic CT scans, showing the dissection of the mucosal and submucosal layer.

The unlikely event of UVI should be, therefore, kept in mind as it may even result in possible relevant complications, the major one being allergic contrast  medium reactions (both minor or systemic, from urticarial rash to respiratory difficulty and hypotension) [1,2,4,5]. Other hazards could be pulmonary embolism [4], septicaemia or sepsis [1,2] and renal failure or acute kidney injury (AKI) in nephropathic patients [1,2]. While performing the exam, it is therefore mandatory to enquire for a history of allergic reactions, to check the patient’s renal function, to avoid use of oily contrast  medium [9] and to rule out recent ongoing urinary tract infections (the usage of prophylactic antibiotic coverage is debated and not always employed, even if generally advised [7,8]). In addition, a 72-hours gap between urethral instrumentation or trauma and retrograde urethrography is advisable [2], even if it may be insufficient for complete mucosal healing and UVR avoidance (as in our case).

Written informed patient consent for publication has been obtained.