Presentation
Abdominal distension
Patient Data
FINDINGS
Left kidney is enlarged and measures 13.7 cm. It contains multiple cysts with parenchyma surrounding a distended renal pelvis. Renal pelvic APD measures 5.6mm.
Mass effect on the left renal vein, the left renal artery and aorta and IVC by the large cystic mass.
Right kidney is of normal size and location. Right renal length measures 7 cm, no evidence of hydronephrosis.
Conclusion:
Large left-sided cystic renal based mass with claw sign of compression of the left renal vein, left renal artery and IVC and aorta
No evidence of lymphadenopathy.
HISTORY
Large left cystic renal mass for definition
TECHNIQUE
Helical acquisition postcontrast CT chest/abdomen/pelvis with multiplanar reformats.
DLP: 15 mGycm
FINDINGS
Large, multicystic fluid density mass originating from the left kidney, measuring 118 x 106 x 136mm (AP x TR x CC). Renal claw sign with anteromedial displacement of the renal parenchyma. Thin septations are present throughout the lesion, but there is no appreciable enhancement, calcification or soft tissue component. There appears to be herniation of pedunculated cysts into the renal pelvis (See Stack Key Image). No hemorrhage.
Left renal artery and vein are patent, and pass anteriorly along the medial mass curvature to enter the left renal hilum in the expected anatomic location.
The mass does not encase any adjacent vessels, nor is there any adjacent soft tissue or organ invasion. Surrounding organs, including spleen, liver, pancreas, adrenal glands and bowel are displaced by the mass. Solid organs and abdominal viscera are otherwise normal. Gallbladder is partially decompressed and thin walled. No intra or extrahepatic duct dilatation.
Aorta and IVA are patent, as are their distal branches.
Right kidney measures 6.7cm in bipolar dimension (~86th centile) with normal corticomedullary differentiation and no focal lesion. Right renal vein and artery are patent. No hydronephrosis or hydroureter.
Bladder is normal.
Both adrenal glands are normal.
No small or large bowel obstruction or perforation.
No abdominal or pelvic free fluid.
IMPRESSION
1) Large multicystic lesion arising from the left kidney with no visible enhancing soft tissue components, which correlates with the recent ultrasound. There is local mass effect, but no vascular invasion / thrombus. The imaging appearance is most consistent with a multilocular cystic nephroma (which may be associated with a DICER 1 mutation).
Histopathology:
Left radical nephrectomy for cystic renal mass.
Almost the entire kidney has been replaced by a cystic tumor, with a small amount of residual normal appearing kidney 55x25x25 mm evident at the inferomedial aspect).
The cut surface of the tumor is multiloculated and cystic with cystic spaces measuring between 2 and 40 mm in maximum extent. The cyst walls are thin and smooth with a maximum septal thickness of 3 mm. No solid areas are seen. The tumor appears to bulge into and expand the renal sinus spaces and also involves the proximal ureter over a length of approximately 10 mm (remainder of ureter appears clear). The tumor does not breach the renal capsule. No involvement of renal vein or artery is macroscopically apparent.
CONCLUSION:
Pediatric cystic nephroma
Case Discussion
Pediatric cystic nephromas (previously multilocular cystic nephromas) are a type of cystic renal lesion in children occurring most frequently in patients between the ages of 3 months and 4 years old.
The above case represents a typical lesion. Particularly, herniation into the renal pelvis is a common finding which can be seen in this case (in the Axial cross sections, Key Image has been set to an image reflecting cyst herniation into the renal pelvis), and confirmed at histology.