By: Nour-Eldin A Nour-Eldin

SIMPLE CYSTS Simple cysts (in > 50% of

population > 50 years) probably arise from obstructed tubules or ducts.

They do not, however, communicate with collecting system.

Most commonly asymptomatic; rare: hematuria (from cyst rupture), HTN,cyst infection. Mass effect from large cysts may cause dull ache or discomfort.

Radiographic features , IVP:

Lucent defect

Cortical bulge

Round indentations on collecting system

"Beak sign" can be seen with large cysts.

Radiographic features , US:

Anechoic

Enhanced through-transmission

Sharply marginated,smooth walls

Radiographic features , CT:

Smooth cyst wall

Sharp demarcation

Homogenous Water density (< 10-15 HU)

No significant enhancement after IV contrast (<5HU)

Cyst wall too thin to be seen by CT

Be Careful:

Cysts that contain calcium, septations, and irregular margins (complicated cysts)need further workup

True renal cysts should always be differentiated from hydronephrosis, calycealdiverticulum, and peripelvic cysts.Differentiate renal cyst from hypoechoic renal artery aneurysm using color Doppler US and Angiography

Hydronephrosis:

Calyceal Diverticulum

Parapelvic Cyst

Renal Artery Aneurysm

Complicated CYSTS

Complicated cysts are cysts that do not meet the criteria of simple cysts and thus require further workup.

Bosniak Classification:

Category (Bosniak) US Features Workup

Type 1: Simple cyst Round, anechoic, thin wall enhanced through transmission

None

Type 2: Mildly complicated cyst

Thin septation, calcium in wall

CT or US follow-up

Type 3: Indeterminate lesion

Multiple septae, internal echos mural nodules

Thick septae

Partial nephrectomy, biopsy

CT follow-up if surgery ishigh risk

Type 4: Clearly malignant

Solid mass component Nephrectomy

Increased CT density (> 15 HU) of cyst contentVast majority of these lesions are benign.High density is usually due to hemorrhage, high protein content, and/or calcium.

Radiographic Features of Complicated CystsSeptationsThin septa within cysts are usually benign.Thick or irregular septa require workup.CalcificationsThin calcifications in cyst walls are usually benign.Milk of calcium: collection of small calcific granules in cyst fluid: usually benign

Thick wallThese lesions usually require surgical exploration.

Simple renal cyst, Bosniak Category I.

Bosniak Category II cyst

Curvilinear calcification within a thin septum

Bosniak Category II cyst

Homogeneously hyperdense mass No increase in Density after IV contrast

Bosniak Category II cyst

Cyst with several internal septations and a minimally thickened wall

Bosniak Category II cyst.

Cyst with uniform, mild wall thickening and short, interrupted calcifications

Bosniak Category II hyperdense cyst.

Bosniak Category II cyst

Bosniak Category II cyst.

Nearly completely calcified mass with no obviousenhancing elements

Bosniak Category II.

subcentimeter rim calcified renal cyst

Bosniak Category III.

cystic mass with irregular wall thickening andassociated heterogeneous nonenhancing elements

Bosniak Category III complex cyst.

multilocular, encapsulated mass

Bosniak Category III complex cyst.

Thick-walled, encapsulated, multilocular cystic mass with enhancing septa

Bosniak Category IV cystic neoplasm.

Bosniak Category IV cystic neoplasm

A 42-year-old female with back pain, hematuria, and a renal mass discovered by lumbar spine MR. hyperdense (55 HU) 3 cm mass.

enhance to 88 HU after IV contrast

Renal cell carcinoma

Thank you

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