AN UNUSUAL PRESENTATION OF HUGE PARAPELVIC CYSTcase report

 MUHAMMAD SHAFIQ UL AZAM, FARHINA IKRAM, SIBTAIN RAZA, SHAFQAT UL ISLAM, SYED MEHMOOD, HAJI HAROON

 Karachi X-rays & CT Scan / Ultrasound centre Karachi

INTRODUCTION 

Parapelvic cysts are spherical fluid filled masses that originate from renal

parenchyma or renal sinus and may cause compression of the collecting system.

Incidence is 1.5% at autopsy and 4-6% of all renal cysts. Its etiology may be

obstructive lymphatic channel, posttraumatic extravasation of urine/blood,

mesonephric/wolffian body remnant, duplication anomaly or outpouchings of

renal pelvis. These are most common in 5th-6th decade. Parapelvic cysts are

almost always asymptomatic but may cause pain from obstructive caliectasis or

may cause renal vascular hypertension from renal artery compression.

Incidentally diagnosed on IVP or ultrasound examination, however CT scan can

be done to see its extension and effect on surrounding structures. 

CASE HISTORY 

A 62 years old male, presented with complains at right lumbar pain associated

with vomiting and fever for last 15 days. Laboratory reports including complete

blood count and liver function tests showed normal values. The only abnormal

investigations were raised ESR, 45, while Serum creatinine was 1.4 mg/dl.

Ultrasound done out side our institute showed large hypoechoic area at right

side of the abdomen and was diagnosed as Liver abscess and referred to us for

ultrasound guided aspiration of the abscess. On ultrasound performed at our

institute, no liver abscess was found instead a large extra hepatic cystic

structure was noted in right side of abdomen lying inferior to the liver with

gross displacement of the right kidney. The origin of this huge cystic lesion could

not be defined on the ultrasound.

We performed his Contrast enhanced CT Abdomen on 16 detector row CT which

revealed a huge right parapelvic cyst with significant superior displacement of

right kidney. The parapelvic cyst also causing significant compression on the

right pelviureteric junction and upper ureter resulting in moderate

hydronephrosis. Another small cortical cyst was seen at the upper pole of right

kidney. The large parapelvic cyst measured 15x17x15 cm in maximum

craniocaudal, anteroposterior and transverse dimensions respectively extending

from right hypochondric region to iliac crest level. The unusual aspect of this

parapelvic cyst is the effect on IVC, which is showing significant lateral and

inferior displacement, these changes were better demonstrated on

reconstructed coronal and sagittal images. A cortical cyst was found at upper

pole of left kidney, measuring about 5x6 cms causing no displacement or

pressure on adjacent structures. Rest of the abdominal viscerae and vessels

were normal.

The patient underwent surgery because of the patient’s symptoms. Per-operative

findings confirmed the diagnosis given on CT. Excision of the cyst was performed

followed by marsupialization. The post operative course was uneventful and the

patient had no complaints on a subsequent short term follow up visit at the

physician’s clinic.

 DISCUSSION:A parapelvic cyst is a well encapsulated collection of fluid outside of the renal

parenchyma. It may give rise to urinary tract obstruction. Such a cyst at the

renal pelvis may cause localized hydronephrosis, cortical thinning from

intrarenal compression, and secondary hypertension remediable by surgical

correction (1).

Parapelvic cyst is not true cyst and may be lymphatic in origin or developed from

embryonic rest (2-4). Parapelvic cyst does not communicate with urinary

collecting system. Therefore, do not fill during excretory urography and contrast

enhanced CT scan examination which differentiates it from perinephric cyst

which may be the result of extravasation of urine (5).

CT scans must not be taken too quickly after injection of contrast material

before it can enter the dilated, and often obstructed, renal pelvis. When contrast

agent does enter the collecting system, in the supine position it is possible for

only the dependent part of the collecting system to be opacified and thus the

unopacified part can be confused with a parapelvic cyst. However, in such cases

a horizontal urine-contrast level would identify this unopacified part as

belonging to the collecting system. This problem is not encountered, however, on

the multidetector row CT scanner because of the capability of multiplanar

reformation.

Although surgical proof was not obtained in most of the studies, the CT criteria

which used were identical to those shown to be virtually pathognomonic for

cysts of the renal parenchyma (3).

CT and sonography provide rapid, accurate, non invasive evaluation of renal

masses identified on excretory urography. To accurately characterize a mass as a

simple benign cyst by CT, the lesion must meet strict criteria (3).In addition to

the well known causes of hemorrhage or infection within a cyst, other cause for

high-density renal cysts, (i.e., that of contrast material artifactually raising the

attenuation value temporarily). When this is suspected, a repeat CT examination

after a short delay can be diagnostic, and it may not be necessary to resort to

more invasive procedures for further clarification. However, the presence of

calcification, particularly if diffuse in distribution, or fresh hemorrhage can lead

to CT numbers higher than those of normal renal parenchyma. The rapid change

from high to relatively low attenuation values in the mass in some of the cases

reported would be highly unusual for a lesion with a malignant etiology (6).

Although it is conceivable that this appearance could have been secondary to

simultaneous hemorrhage or infection in bilateral parapelvic cysts, the lack of a

history of puncture, trauma, bleeding disturbance, or fever combined with the

known extravasation noted after retrograde pyelography makes these much less

likely as explanations for the transient increase in attenuation of the cysts.

Parapelvic cysts may be single or multiple and while they are usually less than 5

cm in diameter, an occasional one may attain larger dimensions (7, 8, 9). A

lymphatic tissue or embryologic rest origin is believed by some to be the source

for parapelvic cysts (7, 8).

 In summary, parapelvic cysts can be diagnosed on both ultrasonography and CT

scan which are both accurate and non invasive examinations. But CT scan is

more valuable as it differentiates renal sinus lipomatosis and hydronephrosis. In

addition to this, it gives more information about complications like infection,

hemorrhage, thrombus formation and extension of the cyst that causes

displacement of adjacent viscera specially vessels which help in surgical

planning. 

REFERENCES 

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8. Ney C, Friedenberg RM. Cysts of the kidney. In: Ney C, Friedenberg RM, eds. Radiographic

atlas of the genitourinary system. Philadelphia: Lippincott, 1981:515-582.

9. Hidalgo H, Dunnick NA, Rosenberg ER, Ram PC, Korobkin M. Parapelvic cysts: appearance on

CT and sonography. AJR1982;1 38:667-671.

a) Coronal reformatted CT images showing huge parapelvic cyst displacing right kidney superiorly and inferior vena cava inferiorly and laterally (curved arrow)

b) Axial contrast enhanced CT images showing huge parapelvic cyst on right side with another left renal cortical cyst