Uriniferous Perirenal Pseudocyst Urinoma

A unique type of perirenal collection is acutely extrav-asated urine secondary to ureteral obstruction or laceration165 (Figs. 8-142 and 8-143). It has been long established that chronic partial obstruction with repeated pyelosinus backflow may lead to uriniferous pseudocyst formation.166

The chronic extravasation of urine into the extra-peritoneal tissues around the kidney and upper part of the ureter, leading to an encapsulated collection, is a distinct clinical and radiologic entity. The condition has been given a variety of confusing names, including

Fig. 8—140. Massive perirenal abscess secondary to calculous pyonephrosis.

Plain film shows increased density, loss of kidney outline, and numerous renal calculi. The abscess has displaced the transverse and descending colon.

Plain Film Colon Retroperitoneal AbscessPlain Film Colon Retroperitoneal Abscess

Fig. 8—141. Perirenal abscess.

In this case, MRI demonstrates the perirenal abscess (A) has loculated medially in relation to the lower renal pole. Note how it is precisely confined inferiorly by the cone of renal fascia. The kidney (K) is displaced laterally, anteriorly, and upward.

(a) T1-weighted axial view.

(b) T2-weighted coronal view.

(Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fig. 8—141. Perirenal abscess.

In this case, MRI demonstrates the perirenal abscess (A) has loculated medially in relation to the lower renal pole. Note how it is precisely confined inferiorly by the cone of renal fascia. The kidney (K) is displaced laterally, anteriorly, and upward.

(a) T1-weighted axial view.

(b) T2-weighted coronal view.

(Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Mallinckrodt Institute Radiology

Fig. 8—142. Perirenal extrava-sated urine.

Enhanced CT scan shows opacified urine extravasating medially within the perirenal space.

Fig. 8—143. Early development of uriniferous perirenal pseudocyst.

CT scan at level of both kidneys shows right kidney (K) with mild hydronephrosis displaced anteriorly by perirenal urine collection (arrows). This occurred as a consequence of pyelosinus backflow secondary to partial distal ureteral obstruction from a retroperitoneal mass.

fined by the cone of renal fascia that comes to constitute its walls

Etiology and Pathogenesis. Most cases of chronic urinary extravasation are secondary to accidental or iatrogenic trauma. Early reports stress renal and ureteral trauma from automobile accidents, football injuries, blows, falls, etc. At the time of clinical presentation, the nature of the original injury may not be recognized or may be remote in nature. More recently, instances are being encountered after surgical operations on the kidney or ureter, diagnostic cystoscopic procedures with perforation of the ureter or renal pelvis, or inadvertent trauma to the lower ureter during pelvic operations.10 In infants and children, a congenital obstruction in the urinary tract may be an underlying factor.

Three factors are necessary to produce the lesion:

pseudohydronephrosis, hydrocele renalis, perirenal cyst, perinephric cyst, pararenal pseudocyst, and urinoma. Unfortunately, each of these terms is misleading, nonspecific, or inaccurate. To indicate its pathogenesis and characteristic morphology, I believe the most accurate designation for this condition should be uriniferous perirenal pseudocyst.10

Since the chronic urine extravasation occurs into the perirenal space, with aseptic inflammation and dissolution of its fat, the contents of the pseudocyst are con-

1. A transcapsular tear of the renal parenchyma must extend into the calyx or pelvis. Perforations of the pelvis or ureter alone are often sufficient.

2. The injury must fail to heal or fail to be sealed off with a blood clot before leakage of urine in any quantity can take place. Urinary extravasation into the perirenal fat results in rapid lipolysis, and a definite fibrous sac (false capsule or pseudocyst) is formed within 12 days.169 Pseudocysts of up to 2,500 mL of urine have been reported. There may also be fatty, fibrous, or oily debris, altered blood clot, or deposits of urinary salts.

3. Ureteral obstruction must be present. It may be caused by a previous pathologic condition, by a transient blood clot within the ureter or a periureteral hematoma, or from fibrosis secondary to the injury. Indeed, the tissue reaction itself results in a continuing element of obstruction establishing a vicious cycle. The ureter may be bound down by scar tissue as it lies embedded in the newly formed sac wall. The necessarily slow development of scar tissue readily explains the typically delayed formation of the mass. The hydrokinetic system then reaches stability only when autonephrectomy occurs.

Clinical Signs and Symptoms. The usual clinical presentation of a uriniferous perirenal pseudocyst is a palpable flank mass associated with some degree of abdominal distress, often mild in nature. The mass is generally only slightly tender to palpation and there is little, if any, increase in temperature. Urinalysis is often completely negative. A typical sequence is general improvement after the original abdominal trauma, followed by the delayed appearance of a flank mass. The latent period between the traumatic episode and the appearance of symptoms and a mass is often 1 to 4 months.170 The mass has occasionally been noted to increase rapidly in

168171 172

size. , Sauls and Nesbit observed a latent period of

Fig. 8-144. Cone of renal fascia.

The two layers of renal fascia completely envelop the kidney and perirenal fat. They fuse in such a manner that the perirenal space bears an axis inferiorly (to the level of the iliac crest) and medially (overlying the lower segment of the psoas muscle). (Reproduced from Meyers.8)

Fig. 8-144. Cone of renal fascia.

The two layers of renal fascia completely envelop the kidney and perirenal fat. They fuse in such a manner that the perirenal space bears an axis inferiorly (to the level of the iliac crest) and medially (overlying the lower segment of the psoas muscle). (Reproduced from Meyers.8)

2 years, and Johnson and Smith reported an unusual case of a calcified pseudocyst diagnosed 37 years after the presumed trauma.173

Radiologic Findings. Since perirenal effusions localize according to the effect of gravity and planes of least resistance, extravasated urine seeks out the portion of the cone of renal fascia caudad to the kidney. Basic to an appreciation of the characteristic complex of radiographic abnormalities is the fact that the pseudocyst typically conforms to the axis and dimensions of the cone of renal fascia (Fig. 8—144), as encountered at surgery (Fig. 8—145). Slow, persistent effusion within the cone of renal fascia distends the perirenal space but allows it to retain its characteristic axis. This phenomenon accounts for the diagnostic changes10 (Fig. 8—146).

The characteristic complex of radiographic abnormalities involves features of the soft tissue mass of the

Fig. 8-145. Surgical specimen of uriniferous perirenal pseudocyst and nonfunctioning hydronephrotic kidney.

Operation was performed 3 months after a traumatic pelvilithotomy. Note that the findings show massive urine distention of the thickened cone of renal fascia, which nevertheless maintains its characteristic axis downward and medially.

(Reproduced from Pyrah and Smiddy. )

Fig. 8-145. Surgical specimen of uriniferous perirenal pseudocyst and nonfunctioning hydronephrotic kidney.

Operation was performed 3 months after a traumatic pelvilithotomy. Note that the findings show massive urine distention of the thickened cone of renal fascia, which nevertheless maintains its characteristic axis downward and medially.

(Reproduced from Pyrah and Smiddy. )

Obstructive Pseudocyst Right Kidney

Fig. 8-146. Major characteristic radiologic changes secondary to uriniferous perirenal pseudocyst.

Basic are the axis and relationships of the chronically distended cone of renal fascia. (Reproduced from Meyers.10)

Fig. 8-146. Major characteristic radiologic changes secondary to uriniferous perirenal pseudocyst.

Basic are the axis and relationships of the chronically distended cone of renal fascia. (Reproduced from Meyers.10)

Pelvilithotomy

Fig. 8-147. Uriniferous perirenal pseudocyst after pelvilithotomy.

Intravenous urogram shows the lower pole of the partially obstructed right kidney displaced upward and laterally by a large elliptical soft-tissue mass (small arrows). The axis of the mass is characteristically oriented inferomedially. Its contours are further highlighted by the contrast provided by posterior pararenal fat into which it bulges posteriorly. The proximal ureter is displaced medially and is dilated, associated with caliectasis and a mild obstructive nephrogram. Incision and drainage of 1,500 mL of urine, nephrostomy, and a splinted ureterostomy were followed by marked improvement. (Reproduced from Meyers.10)

pseudocyst and its effects on the kidney and ureter (Figs. 8-147 through 8-151). In addition, extravasation into the pseudocyst may confirm the actual point of leakage or indicate gross communication with the collecting system.

The most typical and consistent feature of the pseu-docyst is that its axis conforms to the distended cone of renal fascia. Thus, it is elliptical in outline and obliquely oriented inferomedially. Its upper border is lateral in the flank as it comes into relationship to the lower pole of the kidney and its lower border is more medial as it overlaps the psoas muscle near the level of the iliac crest. Its contours may be further outlined on plain films by the contrast of other extraperitoneal fat (specifically within the posterior pararenal compartment) into which the pressure of the pseudocyst bulges. With huge collections, the cone of renal fascia may become so distended that its axis appears more vertical.

The pseudocyst can be identified as a soft-tissue density or as a lucent defect during the phase of total body opacification. Needle opacification of the pseudocyst may outline precisely its contour, size, and characteristic axis.

The kidney is usually displaced upward and its lower pole characteristically deviated laterally. The fat immediately around the kidney and upper third of the psoas muscle can be visualized intact, but the lower margin of

Fig. 8-147. Uriniferous perirenal pseudocyst after pelvilithotomy.

Intravenous urogram shows the lower pole of the partially obstructed right kidney displaced upward and laterally by a large elliptical soft-tissue mass (small arrows). The axis of the mass is characteristically oriented inferomedially. Its contours are further highlighted by the contrast provided by posterior pararenal fat into which it bulges posteriorly. The proximal ureter is displaced medially and is dilated, associated with caliectasis and a mild obstructive nephrogram. Incision and drainage of 1,500 mL of urine, nephrostomy, and a splinted ureterostomy were followed by marked improvement. (Reproduced from Meyers.10)

the psoas muscle is obscured by the pseudocyst. The involved kidney shows poor and delayed function or absent excretion on intravenous urography. Hydrone-phrosis is apparent on delayed films or on retrograde pyelography. The upper ureter is usually deviated medially, occasionally across the midline, but this may require retrograde studies for demonstration. The catheter is often arrested in the upper third of the ureter.

Extravasation into the area of the pseudocyst may be seen on excretory urography or on retrograde pyelog-raphy. Opacification of the mass may be noted at the same time as the nephrogram during intravenous urography or as the patient's position is changed from supine to prone.

Perirenal Cysts

Fig. 8—148. Uriniferous perirenal pseudocyst postpelvilithotomy.

(a) Total body opacification during intravenous urography outlines a lucent mass (arrows). The right kidney is partially obstructed and is displaced upward and laterally.

(b) Contrast opacification of pseudocyst through drainage needle confirms its inferomedial axis. Residual contrast from retrograde pyelography shows obstructive uropathy proximal to the strictured and displaced ureter.

(Reproduced from Meyers.10)

Fig. 8—148. Uriniferous perirenal pseudocyst postpelvilithotomy.

(a) Total body opacification during intravenous urography outlines a lucent mass (arrows). The right kidney is partially obstructed and is displaced upward and laterally.

(b) Contrast opacification of pseudocyst through drainage needle confirms its inferomedial axis. Residual contrast from retrograde pyelography shows obstructive uropathy proximal to the strictured and displaced ureter.

(Reproduced from Meyers.10)

Arteriography demonstrates no inflammatory or neoplastic hypervascularity associated with the mass and may be helpful in further evaluating the position and state of function of the kidney.

Ultrasonography may demonstrate the cystic nature of the mass, its size and position, and the presence of hydronephrosis and the level of obstruction.175,176 Iso-topic studies may also reveal the characteristic find-ings176,177 (Fig. 8-152).

Computed tomography clearly demonstrates the size, position, and relationships of the pseudocyst and may document continuing extravasation by virtue of its opa-cification178 (Figs. 8-153 through 8-157).

Unusual sites of development of uriniferous pseu-docyst may be a consequence of surgery, instrumenta tion, or penetrating injury with interruption of anatomic planes.178

Treatment. It is important to diagnose the condition early so that it can be corrected surgically before inoperable damage to the kidney occurs. The best results have been obtained when surgical intervention occurred within 2-3 weeks after injury. Later, marked fibrosis of the tissues and cicatrization of the ureter make it difficult or impossible to repair or bridge the defect. Nephrostomy drainage with intubation of the repaired ureter is the procedure of choice.179 If renal function has been lost and the contralateral kidney is normal, nephrectomy is advisable.

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Retroperitoneal Nephrectomy

Fig. 8-149. Uriniferous perirenal pseudocyst.

(a) Following accidental partial interruption of the right ureter at the time of retroperitoneal lymph node dissection, intravenous urography demonstrates extravasation of urine.

(b) Three weeks later, there is evidence of a large encapsulated mass (arrows) extending to the level of the iliac crest, with obstruction of the proximal right ureter and hydronephrosis. The lower pole of the kidney is displaced superiorly and laterally.

(c) Later radiograph shows localized extravasation into the pseudocyst. (Reproduced from Meyers.10)

Fig. 8-149. Uriniferous perirenal pseudocyst.

(a) Following accidental partial interruption of the right ureter at the time of retroperitoneal lymph node dissection, intravenous urography demonstrates extravasation of urine.

(b) Three weeks later, there is evidence of a large encapsulated mass (arrows) extending to the level of the iliac crest, with obstruction of the proximal right ureter and hydronephrosis. The lower pole of the kidney is displaced superiorly and laterally.

(c) Later radiograph shows localized extravasation into the pseudocyst. (Reproduced from Meyers.10)

Perinephric Pseudocyst

Fig. 8-150. Uriniferous perirenal pseudocyst.

(a) Following abdominal trauma from an automobile accident, intravenous urography demonstrates extravasation from a poorly functioning right kidney.

(b) Ten days later, after emergency gastrectomy and splenectomy, there is evidence of a large soft-tissue mass (arrows) displacing the obstructed kidney upward and laterally and the colon medially. The mass is oriented somewhat inferomedially, extends to the level of the iliac crest, and is outlined as relatively lucent by the effect of total-body opacification.

(Reproduced from Meyers.10)

Fig. 8-150. Uriniferous perirenal pseudocyst.

(a) Following abdominal trauma from an automobile accident, intravenous urography demonstrates extravasation from a poorly functioning right kidney.

(b) Ten days later, after emergency gastrectomy and splenectomy, there is evidence of a large soft-tissue mass (arrows) displacing the obstructed kidney upward and laterally and the colon medially. The mass is oriented somewhat inferomedially, extends to the level of the iliac crest, and is outlined as relatively lucent by the effect of total-body opacification.

(Reproduced from Meyers.10)

Perinephric Pseudocyst

Fig. 8—151. Uriniferous perirenal pseudocyst 5 weeks after a hysterectomy.

(a) Plain film. Large soft-tissue mass extends to the level of the iliac crest. Ureteral displacement is shown by the opaque catheter, which could not be passed beyond the UP junction.

(b) Abdominal aortogram. The mass shows no hypervascularity and displaces the lower pole of the left kidney upward and laterally.

(c) By the time the left renal artery is selectively catheterized, extravasation into the pseudocyst becomes evident.

(Reproduced from Meyers.10)

Perirenal Cysts

Fig. 8—152. Uriniferous perirenal pseudocyst, secondary to obstruction from recurrent invasive carcinoma of the rectum. Posterior radionuclide image demonstrates the left kidney elevated and its lower pole deviated laterally by an elliptical extrarenal urine collection of lesser activity. The axis of this is obliquely oriented inferomedially. (Reproduced from Suzuki et al.177)

Fig. 8—153. Uriniferous perirenal pseudocyst.

(a) CT scan after intravenous injection of contrast medium shows encapsulated pseudocystic collection of extravasated urine (Ps) displacing the left kidney (LK) laterally.

(b) At a lower level, it distends the cone of renal fascia medial to the descending colon (DC). The anterior and posterior pararenal fat and the lateroconal fascia (arrow) remain intact. At this stage in the study, there is no opacification of the extravasated urine.

(c) Delayed radiograph demonstrates opacification of the pseudocyst, which bears a typical axis and renal displacement.

Fig. 8—153. Uriniferous perirenal pseudocyst.

(a) CT scan after intravenous injection of contrast medium shows encapsulated pseudocystic collection of extravasated urine (Ps) displacing the left kidney (LK) laterally.

(b) At a lower level, it distends the cone of renal fascia medial to the descending colon (DC). The anterior and posterior pararenal fat and the lateroconal fascia (arrow) remain intact. At this stage in the study, there is no opacification of the extravasated urine.

(c) Delayed radiograph demonstrates opacification of the pseudocyst, which bears a typical axis and renal displacement.

Perirenal Fascia Radiographics

Fig. 8—154. Uriniferous perirenal pseudocyst presenting 2 months after a fall.

(a) CT shows large uriniferous pseudocyst within the left perirenal space (PS), anterior displacement of the kidney (K), and a severely hydronephrotic renal pelvis (H).

(b) Sagittal reconstruction demonstrates anterior and superior displacement of the kidney (K) by the large uriniferous pseudo-cyst (Ps) confined within the cone of thickened renal fascia (arrows).

(Reproduced from Healey et al.178)

Perirenal Pseudocyst

Fig. 8—155. Uriniferous perirenal pseudocyst.

CT in a patient with recurrent carcinoma of the cervix and paraaortic adenopathy demonstrates the left kidney (K) with hydronephrosis (H) displaced anteriorly and laterally by a uriniferous perirenal pseudocyst (Ps). There is extravasation of contrast medium (arrow) into the encapsulated urine collection, decompressing the hydronephrosis.

Fig. 8—155. Uriniferous perirenal pseudocyst.

CT in a patient with recurrent carcinoma of the cervix and paraaortic adenopathy demonstrates the left kidney (K) with hydronephrosis (H) displaced anteriorly and laterally by a uriniferous perirenal pseudocyst (Ps). There is extravasation of contrast medium (arrow) into the encapsulated urine collection, decompressing the hydronephrosis.

Fig. 8—156. Uriniferous perirenal pseudocyst.

CT in a 60-year-old woman 10 weeks after a "fall" demonstrates a large uriniferous pseudocyst within the perirenal space (Ps), with contrast medium in its dependent portion (arrows). Anterior displacement of the left kidney (K) and a severely hydronephrotic renal pelvis (H) are also present.

(Reproduced from Healy et al.178)

Pyelosinus Extravasation Radiology

Fig. 8-157. Uriniferous perirenal pseudocyst, secondary to obstruction from metastatic carcinoma of the urinary bladder. (a and b) CT scans after intravenous injection of contrast medium show large pseudocystic collection of extravasated urine (Ps) extending from the right kidney (RK), which it displaces laterally and anteriorly from the medial border of the psoas muscle. As it extends inferiorly, it remains confined within the cone of renal fascia medial to the ascending colon (AC), Adhesions or bridging renal septa within the pseudocyst contribute to mild septation. Metastatic tumor in lymph nodes around the calcified abdominal aorta (Ao) and inferior vena cava is seen as soft-tissue masses.

(c and d) Six-hour delayed scans demonstrate a significantly higher CT number within the pseudocyst, reflecting active extravasation. It is because of this decompression that although the right ureter is dilated (curved arrow), the collecting system does not appear obstructed.

(Courtesy of Michael Oliphant, M.D., Crouse Hospital, Syracuse, NY.)

Fig. 8-157. Uriniferous perirenal pseudocyst, secondary to obstruction from metastatic carcinoma of the urinary bladder. (a and b) CT scans after intravenous injection of contrast medium show large pseudocystic collection of extravasated urine (Ps) extending from the right kidney (RK), which it displaces laterally and anteriorly from the medial border of the psoas muscle. As it extends inferiorly, it remains confined within the cone of renal fascia medial to the ascending colon (AC), Adhesions or bridging renal septa within the pseudocyst contribute to mild septation. Metastatic tumor in lymph nodes around the calcified abdominal aorta (Ao) and inferior vena cava is seen as soft-tissue masses.

(c and d) Six-hour delayed scans demonstrate a significantly higher CT number within the pseudocyst, reflecting active extravasation. It is because of this decompression that although the right ureter is dilated (curved arrow), the collecting system does not appear obstructed.

(Courtesy of Michael Oliphant, M.D., Crouse Hospital, Syracuse, NY.)

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