Urinary Tract Trauma and Uroperitoneum

Chapter 12 Urinary Tract Trauma and Uroperitoneum



Introduction




A. Types of trauma to the urinary tract (Figure 12-1)
1. Kidney: Renal trauma is not commonly recognized in dogs or cats, possibly because the kidneys are protected by a fibrous capsule and embedded in perirenal fat. Absorption of shock also is facilitated by the fact that both kidneys are relatively mobile in the dog and cat. Further protection of the kidneys is provided by the ribs, epaxial musculature, and spine.
a. Contusion: Subcapsular bruising and ecchymosis.
(1) Hemorrhage stops spontaneously.

(2) Microscopic hematuria can be observed.

b. Hematoma: Blood accumulates in the perinephric region between the renal capsule and fascia.
(1) Hemorrhage may stop spontaneously.

(2) Perinephric cyst or abscess may form as hematoma is liquefied.

(3) Microscopic hematuria can be observed.

c. Fissure: Renal parenchymal tear that extends through the renal capsule resulting in a perinephric hematoma (Figure 12-2).

d. Rupture: Tear that is extensive enough to allow blood to accumulate in the retroperitoneal space or peritoneal cavity.
(1) Laceration: Sharp line of demarcation.

(2) Fracture or pulpifaction (Figure 12-3).

(3) Tear through renal pelvis: Extravasation of blood and urine.

e. Pedicle injury.
(1) Vascular avulsion: Severe and rapid loss of blood.

(2) Ureteral avulsion: Extravasation of urine.

2. Ureter.
a. Avulsion from kidney or bladder.

b. Rupture along its length.

3. Urinary bladder.
a. Rupture: More likely in males due to anatomy of urethra.

b. Contusion.

4. Urethra.
a. Avulsion from the bladder.

b. Rupture.

5. Periurethral: Swelling and compression may result in obstruction.


image

FIGURE 12-1 Types of renal trauma. A, Contusion. B, Contusion with some bleeding into subcapsular space. C, Bleeding into retroperitoneal space and into renal pelvis. D, Laceration of renal parenchyma. E, Pulpifaction of renal parenchyma.


(Drawn by Tim Vojt.)


image

FIGURE 12-2 Perinephric hematoma. Note the degree of retroperitoneal hemorrhage surrounding this kidney.


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FIGURE 12-3 Pulpifaction of renal tissue following severe renal trauma.


(Courtesy of Dr. William DeHoff, Med Vet, Worthington, Ohio.)



Pathogenesis and Pathophysiology



Causes of Urinary Tract Trauma





1. Blunt abdominal trauma (e.g., hit by a car, fall from height, kicked) is most common.

2. Penetrating injury (e.g., knife, bullet wound).

3. Iatrogenic.
a. Improper urinary catheterization technique.

b. Accidental tear of urinary tissues during surgery.

c. Improper cystotomy closure or breakdown of closure.

d. Overzealous attempts to manually express urine from the bladder.

e. Cystocentesis performed on a severely distended and devitalized bladder associated with urethral obstruction.

f. Cystostomy tube leakage (very uncommon).

g. Cystoscopy technique errors.

4. Rupture of bladder, urethra, or ureter secondary to obstruction or erosion by a calculus.

5. Urethral obstruction with secondary bladder rupture (rare).

6. Breakdown of friable neoplastic or infected tissue anywhere along the urinary tract.

7. Spontaneous rupture of large intrarenal cysts (i.e., pre-existing cystic renal disease).


Syndromes Caused by Urinary Tract Trauma or Rupture





1. Direct tissue injury (hemorrhage, swelling, inflammation, necrosis).

2. Blood loss.

3. Urine extravasation into body cavity.
a. Uroperitoneum is the accumulation of urine in the peritoneal or retroperitoneal spaces due to a rupture of the urinary tract anywhere along its course (i.e., kidney, renal pelvis, ureter, urinary bladder, urethra).

b. Urinary bladder rupture is the most common traumatic disruption of the urinary tract and source of urine leakage.

4. Urine extravasation into subcutaneous tissues from a tear in the urethra causes swelling, bruising, and sloughing of tissues.

5. Postrenal azotemia and failure. Azotemia develops as nitrogenous waste products accumulate in the peritoneal cavity and are absorbed across the semipermeable peritoneal membranes. Absorption of waste products also can occur from the subcutaneous tissues when urine accumulates there.

6. Peritonitis.
a. Chemical peritonitis can occur from urine irritation in dogs and cats.

b. Bacterial peritonitis can occur from urinary tract infection or contamination of ischemic tissue or blood.


History




A. Known trauma (e.g., observed as hit by a car).

B. Recent abdominal surgical procedure, especially cystotomy.

C. Recent attempts at manual bladder expression.


Clinical Signs




A. Increasing abdominal girth may be noted if enough time has elapsed since the rupture.

B. Lack of observed urinations or decreased volume of urine produced if rupture is in the lower urinary tract.
1. Urine volume is variable in animals with ruptured bladder.

2. Observation of voiding does not rule out ruptured bladder.


image Some animals continue to urinate despite the accumulation of urine in the abdomen due to ruptured bladder.



C. Dysuria, stranguria, and pollakiuria may occur with rupture of the bladder or urethra.

D. Hematuria may be observed, but is not specific or sensitive for rupture of the urinary tract.

E. Increased thirst sometimes is noted as a consequence of fluid shifts that occur as urine accumulates in the peritoneal cavity.

F. Reluctance to walk.

G. As uroperitoneum persists, the signs of uremia including vomiting, lethargy, and dehydration become more apparent.

H. Because uroperitoneum frequently is associated with trauma, additional signs often will be present due to other systemic injuries (e.g., musculoskeletal injuries).

I. Trauma associated with a fractured pelvis or femur increases the likelihood of bladder or urethral rupture, especially in dogs.


Physical Examination




A. Pain near the site of rupture may be noted during palpation.

B. Abdominal fluid may be detected, especially after fluids are administered.

C. Evidence of extensive abdominal injury (e.g., bruising) or fractures (e.g., pelvis, femur) in small animals (Figures 12-4 and 12-5).

D. A small urinary bladder may be palpable in dogs and cats with ruptured bladder.
1. Bladder fails to fill during fluid therapy because fluid continues to leak into the abdomen.

2. If the tear is in one kidney or ureter, the bladder still may fill adequately from urine formed by the intact kidney.

3. If a bladder tear is small, a substantial volume of urine can distend the bladder and render it palpable despite ongoing leakage of urine into the peritoneum.

E. Distal urethral rupture can result in urine accumulation in the soft tissues of the perineum, caudal thighs, and inguinal region (Figure 12-6). Bruising, cellulitis, and sloughing of tissues may be detected after 12 to 36 hours.

F. Rectal examination.
1. May reveal pain as a ruptured urethra or bladder neck is palpated.

2. May reveal fragments of fractured pelvis that can be associated with or have caused the ruptured bladder.

image

FIGURE 12-4 Deep bruising of caudal abdomen. This type of bruising should raise suspicion for the possibility for severe damage to underlying organs, especially for rupture of the bladder or urethra.


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FIGURE 12-5 Radiogram showing severe trauma to the boney pelvis. This type of trauma is often associated with rupture of the urethra or bladder. A, Lateral view of pelvis. Note multiple fractures. B, Ventrodorsal (VD) view of pelvis. Note multiple fractures.


(Courtesy of The Ohio State University Veterinary Medical Center Orthopedics Program and Dr. Jon Dyce.)


image

FIGURE 12-6 A, Sloughing of perineal skin in two areas due to urethral rupture in a cat and urine accumulation in the subcutaneous tissues. B, Urethrogram showing communication of lateral urethra with lateral thigh.



image Retrieval of a substantial volume of urine after passage of a urinary catheter does not exclude the possibility of a ruptured bladder or urethra.



Diagnosis of Uroperitoneum



Passage of Urethral Catheter





1. Retrieval of a substantial volume of fluid after urethral catheterization does not rule out ruptured bladder.
a. The catheter may pass through the ruptured bladder and collect abdominal fluid.

b. The bladder still can contain substantial residual urine depending on the size and location of the leak.

2. It may be difficult to pass a catheter if the urethra is ruptured.


Abdominocentesis





1. The ratio of the abdominal fluid creatinine concentration to the serum creatinine concentration (both in mg/dL) provides evidence that the suspect abdominal fluid is urine.

2. The concentrations of creatinine and urea in urine entering the peritoneal cavity from a ruptured bladder are very high. Having a higher molecular weight than urea, creatinine does not move across the peritoneal membranes into blood as rapidly as urea, and thus accumulates to a greater degree in the abdominal fluid.

3. The concentration of creatinine in a sample of the abdominal fluid can be compared with the serum creatinine concentration. For example, the concentration of creatinine in the abdominal fluid may be 16.0 mg/dL and serum creatinine concentration may be 4.0 mg/dL. This ratio of 4:1 is definitive evidence that the fluid is urine (a ratio of >2:1 is expected in most cases of ruptured bladder).

4. Simultaneous determination of the abdominal fluid urea nitrogen concentration as compared to blood urea nitrogen (BUN) concentration also can be performed but is not as helpful. Urea has a lower molecular weight than creatinine and equilibrates across the peritoneal membranes more rapidly, resulting in a lower ratio of abdominal fluid urea concentration to BUN concentration. For example, the fluid urea nitrogen concentration may be 90 mg/dL as compared with a BUN concentration of 80 mg/dL (ratio of 1.1).


image The ratio of peritoneal fluid creatinine concentration to serum creatinine concentration decreases over time as equilibration with blood occurs across the peritoneum.




5. Also due to molecular size differences, phosphate will be retained in the abdominal fluid longer than potassium.

6. In a study of 13 dogs with ruptured bladder, abdominal fluid creatinine concentration was at least four times greater than the upper limit of normal serum creatinine concentration in all cases.
a. The median abdominal fluid creatinine concentration to serum creatinine concentration ratio was 4.0 (range, 1.4 to 19.2). A ratio of >2.1 identified 86% of dogs with uroperitoneum. The median abdominal fluid creatinine concentration was 16 mg/dL (range, 7.5 to 22.5 mg/dL) and median serum creatinine concentration was 4.4 mg/dL (range, 0.6 to 11.4 mg/dL).

b. As expected, the largest gradients were seen in animals that had minimal azotemia and the smallest gradients were seen in animals with overt azotemia.

c. The median abdominal fluid potassium concentration to serum potassium concentration ratio was 2.7 (range, 1.4 to 3.3). A ratio of >1.4 predicted uroperitoneum accurately in all of the dogs.

d. Dogs with ascites of other cause had a median abdominal fluid creatinine concentration to serum creatinine concentration ratio of 1.1 and an abdominal fluid potassium concentration to serum potassium concentration ratio of 1.0.

e. Specificity and sensitivity were 100% for the diagnosis of uroperitoneum in dogs when the abdominal fluid creatinine concentration was at least 4 times the upper limit of the laboratory reference range for normal serum creatinine concentration, the abdominal fluid potassium concentration to serum potassium concentration ratio was >1.4, and the abdominal fluid creatinine concentration to serum creatinine concentration ratio was >2.1.

f. Serum potassium concentration was >6.0 mEq/L in 31% of dogs with ruptured bladder.
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Related posts:

  1. Familial Renal Diseases of Dogs and Cats
  2. Diseases of the Glomerulus
  3. Disorders of Micturition and Urinary Incontinence
  4. Urinalysis

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Jul 10, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Urinary Tract Trauma and Uroperitoneum

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