Extravasation of Urine : Causes, Cases

Urine Extravasation 

Extravasation of urine is a pathological condition in which the urethra is interrupted, leading to urine collection in cavities other than the urinary bladder. 

Extravasation of urine can be in the form of ASCITES. Ascites is urine inside the peritoneal cavity. 

Causes of Extravasation of Urine

• Fundal rupture of the urinary bladder with the rupture of the peritoneum. Thus, the urine enters the peritoneal cavity, causing ascites.

• Rupture of the membranous urethra (above the perineal membrane), the urine comes into the retropubic space of retzius (Paravesical space - Paravesical around the urinary bladder). It may be due to a Fractured pelvis.
• It is an extraperitoneal extravasation of urine; thus, the urine cannot enter the peritoneal cavity as it is intact. The reason is that the peritoneum covers the anterior abdominal wall, fundus of the bladder, upper part of the rectum, and posterior abdominal wall.
• Straddle injury and rupture of bulbous spongy urethra below the perineal membrane. The urine may drain at 4 places;
  • Superficial perineal pouch below the perineal membrane,
  • Intrascrotal area,
  • Penis,
  • Anterior abdominal wall under the Scarpa's fascia and in front of the pubis bone.

Cases related to Extravasation of Urine

Case 01:

• It is intraperitoneal extravasation of urine. 
• Fundal rupture may also rupture the peritoneum.
• The urine enters the peritoneal cavity, causing ascites.

Case 02:

• Rupture of the membranous urethra is commonly seen in pelvic fractures in the deep perineal pouch.

Case 03: 

• In the straddle injury, the rupture of the bulbous spongy urethra.
• Most of the urethral ruptures are at the junction of the posterior (Membranous urethra) and anterior (Spongy urethra) urethra.
• These are the most commonly seen ruptures.
• Urine is extraperitoneal (Around the urinary bladder).

Structure of Penis

At the penis, the Corpus cavernosum is for the blood supply. Urine can be extravasated from the urethra (Penile spongy urethra). The Fascia present in the penis are:

• Scarpa's fascia
  • It is a part of the superficial fascia.
  • Present at the anterior abdominal wall.
  • It will continue with the penile fascia.
• Penile fascia
  • It is the dartos fascia, which is the superficial area.
  • It is continuous with the scrotal fascia.  
• Scrotal fascia
  • It is the dartos fascia, which is the superficial area.
  • It is continuous with colles fascia.
• Colles fascia
  • It is continuous with the perineal membrane.
• Deep fascia - Buck's fascia

Penile fracture

If the penis is intact, then the blood and urine is restricted to within the shaft of the penis. If it is ruptured, then the blood and urine comes out at 4 places.

• Penile shaft 
• Scrotum
• Superficial Perineal pouch
• Anterior abdominal wall under the scarpa's fascia and anterior to pubis bone.

Buck's Fascia 

The superficial fascia is known as the Dartos fascia, and the deep fascia is known as Buck's fascia. If Buck's fascia is intact, blood and urine come from the penile shaft during a penile fracture. Corpora cavernosum with blood, which can be filled with blood during vasodilation, during erection of penis. Corpus spongiosum is the Spongy urethra.

In rupture of the membranous urethra due to the pelvic fracture, the urine may enter at 3 places;

• The paravesical space around the urinary bladder (External extravasation of urine) doesn't go to the peritoneum as it is intact, but it is located at the retropubic space of the retzius, behind the pubic bone.
• The urine may enter the deep and superficial pouch.
  • In case of associated rupture of the perineal membrane due to the pelvic fracture, the urine may enter the superficial pouch (In some cases).

In the rupture of bulbous spongy urethra below the perineal membrane, the urine may drain at 4 places:-

• Superficial perineal pouch below the perineal membrane,
• scrotum,
• Penis,
• Anterior abdominal wall under the Scarpa's fascia and anterior to the pubis bone.

The urine cannot go to three places;

• Above the perineal membrane, deep perineal pouch. 
• Ischiorectal fossa prevented by colles fascia. 
• Fascia lata, the deep fascia of the thigh, is prevented by urine entering the thigh.

Sagittal Section of the Male Pelvis

• In the anterior abdominal wall, there is superficial fascia having 2 layers :-
  • Anterior 
    • It is fatty and called a camper's fascia. 
  • Posterior
    • Deeper to the camper's fascia is called scarpa's fascia or membranous fascia.
• The membranous fascia of the superficial fascia enter into the penile fascia (Dartos fascia) → Dartos fascia of the scrotum → Colles fascia and it merges with the perineal membrane of the perineal body at the floor of the deep perineal pouch.

Sagittal section of the male pelvis shows

• Perineal body is attached to the perineal membrane  (Floor of the deep perineal pouch) posteriorly.
• Penile spongy urethra opens outside, inside the penis (Penile Shaft).
• External oblique muscle on the anterior abdominal wall is attached to the pubis. 
• In front of the external oblique muscle, scarpa's fascia (Membranous layer of superficial fascia) is present.
• The Scarpa's fascia is continuous with the Penile fascia, which is continuous with the Scrotal fascia, Colles fascia ,Perineal membrane at the perineal body creating a closed space.
• There is a fibrous tissue between the deep pouch and pubis bone.
• If the urine is extravasating, it will enter:-
  • Superficial perineal pouch below the perineal membrane,
  • scrotum
  • Penis,
  • Anterior abdominal wall.
• Penile fascia or dartos fascia - Superficial fascia of the penis continues with the dartos fascia of the scrotum and continues with colles fascia and it merges with the perineal membrane and perineal body.

Peritoneal cavity;

• The urine cannot enter the peritoneal cavity as it covers;
  • Anterior abdominal wall,
  • Fundus of the urinary bladder,
  • Posterior abdominal wall. 
• It is intact.
• If rupture membranous urethra of urine extravasation is extraperitoneal.

Special case:

In patient who have been exposed to bomb explosion;

• It causes the associated rupture of the peritoneum. 
• The urine enters the peritoneum cavity due to the fundal rupture of the urinary bladder with the associated rupture of the peritoneum.
• It causes ascites.

• No rupture of Buck's fascia;
  • The urine and blood is confined to the penile shaft.
• Rupture of urethra at bulb (Rupture of Buck's fascia), just like rupture of bulbous spongy urethra below the perineal membrane.
  • The urine enters the 4 places;
    • Penis,
    • Scrotum,
    • Superficial perineal pouch,
    • Anterior abdominal wall.

Frequently Asked Questions:

Q: A patient exposed to bomb explosion injury presents with rupture of the fundus of the urinary bladder. The extravasated urine reaches

1. Space of Retzius
2. Deep perineal pouch
3. Superficial perineal pouch
4. Peritoneal cavity

Ans. Peritoneal cavity

Q: Injury to the male urethra above the perineal membrane due to a pelvic fracture causes urine to accumulate in all of the following EXCEPT

1. Space of Retzius
2. Deep perineal pouch
3. Superficial perineal pouch
4. Peritoneal cavity

Ans. D. Peritoneal cavity

Q: A 16-year-old boy presents to the emergency department with straddle injury and rupture of the bulbous urethra. Extravasated urine from this injury can spread into which of the following structures

1. Scrotum
2. Ischiorectal fossa
3. Deep perineal space
4. Thigh

Ans. Scrotum

Q. After fracture of the penis (injury to the tunica albuginea) with intact Buck's fascia, there occurs hematoma at

1. The penis and scrotum
2. At the perineum in a butterfly shape
3. Penis, scrotum, perineum and lower part of anterior abdominal wall
4. Shaft of the penis only

Ans. Shaft of the penis only

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