CYSTIC RENAL MASSES

PRESENTOR : DR NAVNI GARG

OVERVIEW

OLD CLASSIFICATION OF CYSTIC RENAL MASSES

BOSNIAK CLASSIFICATIONROLE OF VARIOUS RADIOLOGICAL

MODALITIES IN EVALUATING CYSTIC RENAL MASSES

VARIOUS CYSTIC RENAL MASSES

CLASSIFICATION OF CYSTIC RENAL MASSES

ELKIN & BERNSTEIN, 1969

RENAL DYSPLASIA1. Multicystic kidney2. Focal and segmental cystic dysplasia3. Multiple cysts associated with lower urinary tract

obstruction

POLYCYSTIC DISEASE1. Childhood polycystic disease – AR2. Adult polycystic disease – AD

CORTICAL CYSTS1. Simple cyst2. Multilocular cystic nephroma3. Syndromes associated with cysts4. Haemodialysis associated cysts (acquired)

MEDULLARY CYSTS1. Calyceal cyst (diverticulum)2. Pyelogenic cyst3. Medullary sponge kidney4. Papillary necrosis5. Juvenile nephronophthisis (medullary cystic disease)

MISCELLANEOUS INTRARENAL CYSTS1. Inflammatory

(a) Tuberculosis (b) Calculus disease (c) Hydatid (d) Obliterative pyelonephritis

2. Neoplastic cystic degeneration of parenchymal carcinoma malignant changes in wall of simple cysts cystadenoma3. Traumatic – intrarenal haematoma

EXTRAPARENCHYMAL RENAL CYSTS1. Parapelvic cyst2. Peripelvic cyst

OTHER CLASSIFICATIONS

BOSNIAK CLASSIFICATION, 1986

DR MORTON A BOSNIAK

1986 : BOSNIAK CLASSIFICATION , 4 CATEGORIES

1993 : MODIFIED BOSNIAK CLASSIFICATION , ADDED ADDITIONAL CATEGORY II F

CATEGORY I

Benign lesions Thin wall Well defined interface with parenchyma No septations No calcification Density : 0 – 20 HU No enhancement

Example – Simple renal cyst

CATEGORY II

Cysts complicated by prior infection or haemorrhage

Benign cystic lesion with hairline thin septa

Fine calcification in walls/ septa

Atleast one fourth of the lesion’s circumference should extend outside the kidney so that the smoothness of the wall can be evaluated

Minimal perceived post contrast enhancement

Non enhancing high attenuation (40-100 HU) lesion < 3 cm in diameter

THIN SEPTA HEMORRAGIC CYST

CATEGORY II F

F = Follow up

More complex cyst

Increase in number of septa and calcifications

Non enhancing high attenuation lesions > 3 cm

May advance to category III with time and require 6 month follow up

CATEGORY III

Indeterminate cystic masses

Thick, irregular calcification in walls or septa

Irregular borders

Thickened or enhancing septa

Uniform wall thickening or that contain small non enhancing nodules

Examples – multilocular cystic nephroma lymphangioma hydatid cyst cystic renal cell carcinoma

CATEGORY IV

Malignant cystic masses

Shaggy thickened walls

Thick septations

Coarse calcifications

Density > 20 HU

Enhancing

Example – Renal cell carcinoma

SI II IIF III IV

DENSITY WATER Water density or 40-100 HU(<3 CM SIZE)

40-100 HU(>3CM)

WALL HAIRLINE THIN

THIN MAY BE THICKENED

THICKENED

SEPTA _ FEW HAIRLINETHIN

MULTIPLEHAIRLINE THIN,MAY BE THICKENED

THICKENED

CALCIFICATION _ THIN (<1MM) IN WALL/SEPTA

CAN BE THICK/NODULAR

NODULARTHICK

SOLID COMPONENT

_ _ _ +/- +

ENHANCEMENT _ _ _ WALL +SEPTA+SOLID -

ENHANCING SOFT TISSUE COMPONENT

RISK OF MAILGNANCY (%)

1.7 18.5 > 18.5 33 92.5

WORKING INTERPRETATION OF BOSNIAK CLASSIFICATION

CATEGORY I We know it’s a cyst

CATEGORY II We are still pretty certain it’s a cyst

CATEGORY III We don’t know what it is

CATEGORY IV Its probably a tumor

All the parameters should be assessed before classifying a lesion !

HOW USEFUL IS BOSNIAK CLASSIFICATION?

It accurately identifies Category I & Category IV lesions

There are inter observer variations in Category II & Category III lesions

Cannot efficiently characterize Category III lesions

INTERPRETATION PITFALLSA small lesion with the same number and type of septa

as a large lesion will appear more complex.Enhancement of hyperdense or heavily calcified lesions

is difficult to assess, especially when the lesion is smallPseudoenhancement occurs when a cyst (generally < 2

cm) is surrounded by enhancing parenchyma during peak enhancement and artifactually appears to enhance. It should be suspected when a lesion is homogeneous and measures less than 10 HU on an unenhanced scan.

Rarely lymphoma, myomatous hamartoma , RCC and metastasis measure greater than 20 HU on unenhanced scans.

ROLE OF VARIOUS RADIOLOGICAL MODALITIES IN CYSTIC RENAL MASSES

MODALITIES

UltrasoundColor DopplerComputed tomographyMagnetic resonance imagingUSG/CT guided cyst aspirationAngiographyTc-99m DMSA Scintigraphy

ULTRASOUNDDifferentiates between solid and

cystic lesions

Features of cyst are(a) Anechoic(b) Posterior acoustic enhancement(c) Sharply marginated smooth walls

Cyst septations yield strong back echoes and may create reverberation artifacts within the cyst.

Calcification within the cyst may cause shadowing.

COLOR DOPPLERTo assess the vascularityVascularity within a nodule or septum

greatly increases the likelihood of malignancy.

TISSUE HARMONIC IMAGINGHemorragic or proteinaceous cysts may

contain low level echoes or even layers of echoes.

THI helps in confirming this by eliminating dirty echoes within an otherwise pristine cyst.

USG CAN BE EMPLOYED TO DIRECT PERCUTANEOUS THERAPIES SUCH AS RFA AND CRYOTHERAPY OF COMPLEX RENAL LESIONS.

CONTRAST ENHANCED USG

CONTRAST ENHANCED USG MAY BE HELPFUL IN PATIENTS WHO

REQUIRE FOLLOW UP TO REDUCE THE RADIATION EXPOSURE

CEUSG IS APPROPRIATE IN THE BOSNIAK CLASSIFICATION OF RENAL CYSTS

PITFALLS OF USG

Can miss carcinoma within a cluster of cysts

Vascular malformations may mimic cysts

Artifactual echoesComplex cyst require further evaluation

COMPUTED TOMOGRAPHY

TECHNIQUEPre and post contrast images2.5 to 5 mm thick slides

Images acquired :

Unenhanced CTCorticomedullary phase ( 20-30 seconds)Nephrographic phase ( 80-100 seconds)Delayed ( 10 minutes )

CHANGE IN ATTENUATION

INTERPRETATION

< 10 HU TYPICAL OF BENIGN CYSTVERY RARELY RENAL CYSTIC TUMOR

10-15 HU SUSPICIOUS FOR MALIGNANCYCOULD BE DUE TO VOLUME AVERAGING, IMPERFECT PLACEMENT OF REGION OF INTEREST, MOTION ARTIFACT

>15 HU PATHOLOGICAL PROCESS : MALIGNANCY, CYSTIC ANGIOMYOLIPOMA , ONCOCYTOMA , INFECTIONS

ROLE OF DUAL ENERGY CT SCANDECT has ability to identify presence of iodine in

body tissues We can generate virtual noncontrast images to

reproduce the baseline unenhanced attenuation, this allows reduction in radiation doses.

It is also possible to produce an “iodine overlay,” in which the presence of iodine in the tissues is indicated by a superimposed color map

In this we do not rely on increase in attenuation to measure enhancement instead,we directly visualise the presence of iodine in lesion.

Since renal cysts do not have blood flow,an iodine-overlay image should show a cyst as devoid of iodine signal

This method may prove beneficial beyond the current practice of determining enhancement in a renal mass because it has potential to reduce the effect of renal cyst pseudoenhancement.

EVALUATION OF RENAL CYST

True unenhanced

Contrast enhanced

Virtual unenhanced

Iodine overlay

MAGNETIC RESONANCE IMAGING

TECHNIQUET1W Gradient echo : high signal

protein ,hemorrage , fatT2W HASTE : septa or nodules within the cystic

fluidPOST CONTRAST T1W Serial images at 5,10,20

minutes

MAGNETIC RESONANCE IMAGINGADVANTAGES :Demonstrates

additional septa wall/septal thickening Enhancement

Superior contrast resolutionEnhancement within a calcified cystic lesion : calcification

is usually less apparent on MRI thus making enhancement more apparent.

Substraction imaging : hemorragic cysts appear hyperintense on both T1 and T2 and don’t enhance after contrast administration. Substraction imaging can help in identifying presence of enhancement in these high signal lesions.

DISADVANTAGESPoor in demonstrating calcifications

RENAL CYST PUNCTURE AND ASPIRATION

Ultrasound or CT guidedOf doubtful utility

INDICATIONSInfected cyst – diagnostic or

therapeuticIndeterminate cyst on USG/CTDecompression

DISADVANTAGESThough if positive confirms

malignancy but a negative aspirate doesn’t rule out malignancy

Multiloculated cystRisk of needle track seeding

NUCLEAR MEDICINETc 99m scintigram

Cyst and solid tumor appear as cold defect

CYSTIC RENAL MASSES

SIMPLE RENAL CYSTSMC renal masses

ETIOLOGYProbably secondary to

tubular obstruction

IVURadiolucent massPencil thin wallClaw or beak sign

USGAnechoic with posterior

acoustic enhancement

CT CRITERIA MRI CRITERIASharp margination

and demarcation from surrounding renal parenchyma

Smooth thin wallHomogenous water

density content (0-20 HU)

No contrast enhancement

Sharp margination and demarcation from surrounding renal parenchyma

Smooth thin wallHomogeneous contents

with signal characteristics of water

No contrast enhancement

OCCASIONALLY A, SOLID RENAL TUMORS MAY OBSTRUCT THE TUBULES OF ADJACENT NORMAL RENAL PARENCHYMA RESULTING IN TUBULAR DILATATION AND SECONDARY CYST FORMATION

( SENTINEL CYST ). THEREFORE WHENEVER A SIMPLE CYST IS DETECTED, THE ADJACENT PARENCHYMA SHOULD BE CAREFULLY EVALUATED FOR THE PRESENCE OF AN ADJACENT SOLID MASS.

COMPLEX CYSTS Anything which is not a simple cyst

RADIOLOGICAL FINDINGS

Thick wall

Irregularity at the base of the cyst

Septations

Calcifications

High attenuation values

Contrast enhancement

HEMORRHAGIC CYSTCyst containing bloodCommon in

polycystic renal disease malignant cysts trauma

Presentation - acute or insidiousMost hemorrhagic cysts < 3 cm are benignRADIOLOGICAL FINDINGS 1. Hyperdense cyst 2. Settling debris 3. MRI – most commonly hyperintense on T1 and

T2 weighted sequences. They may show fluid-iron levels because of dependant settling of methemoglobin containing sediments.

POLYCYSTIC KIDNEYSIf you can count the number of cysts, they are simple

cysts ; if you can’t, it’s polycystic CHILDHOOD POLYCYSTIC DISEASE AR Ectasia of renal collecting ducts Subtypes : Perinatal Neonatal Infantile Juvenile Associations –

Oligohydramnios Potter’s syndrome Respiratory failure Periportal fibrosis (sequelae) causing PHTN

Tubular ectasia is confined mainly to the renal medulla with only occasional macrocysts

Renal cortex is less severely affectedSeverity of disease is inversely related to

age of the patient Hepatic and renal involvement are

inversely proportional to each other.

IVU : striated nephrogram due to accumulation of contrast in dilated tubules

USG: Diffusely echogenic kidneys

NCCT – smooth, enlarged kidneys, low in attenuation due to large fluid volume in dilated ducts

CECT – Striated nephrogram, hepatic fibrosis and features of portal hypertension

ADULT POLYCYSTIC KIDNEYSADPathology : cysts of varying size gradually

replace renal parenchyma C/F :

Presents between 20 and 39 years Hypertension Renal insufficiency Hematuria Renal stones Complications of multiple cysts

Associated with cysts in liver > pancreas > brain> spleen > ovaries > testes

Associated with cardiac valvular disorders , abdominal and inguinal hernias, aneurysm of cerebral and coronary arteries

Colonic diverticula : 80%

SPIDERY COLLECTING SYSTEM WITH STRETCHED CALYCES

NUMEROUS SMOOTHLY MARGINATED RADIOLUCENCIES THROUGHOUT THE CORTEX AND MEDULLA (SWISS CHEESE APPEARNCE).

ADULT POLYCYSTIC KIDNEYS

CT/ MRI : multiple renal cysts of varying size There may be features of complex

cyst

The risk of renal cancer in patients with ADPKD who are not undergoing dialysis is not increased.However patients undergoing dialysis are at greater risk for development of renal malignancy relative to general population.

3 MAIN CRITERIA : FAMILY HISTORY, AGE, TYPE/NUMBER OF CYSTS

D/D Multiple simple cysts (less diffuse, no

family history) Von Hippel-Lindau disease (cerebellar

hemangioblastoma, retinal hemangiomas, occasionally pheochromocytomas)

  Acquired uremic cystic disease (kidneys small, no renal function, transplant)

Infantile PCKD (usually microscopic cysts) 

MULTICYSTIC DYSPLASTIC KIDNEYS

MC cystic disease in infantsM > FFemales have higher chances of

bilateral diseaseMay be associated with

contralateral abnormalities like obstruction of the ureteropelvic junction,renal agenesis,renal hypoplasia, VUR

May be associated with cleft palate, ductal plate malformation of the liver,cardiac abnormalities

MECHANISM :In utero failure of ureteric

bud to connect with the nephrons in the metanephric blastaema

PATHOLOGY : Kidney – non functioning

and converted into a multicystic

dysplastic massUreter – atreticRenal artery – hypoplastic/

atretic

TYPESPelvoinfundibular atresia : no discernible renal

pelvis is seen. Kidney may be small/normal or enlarged. Contains multiple non communicating cysts.No exretion of contrast by kidneys. No perfusion on renal scintigraphy.

Hydronephrotic type : Dilatation of renal pelvis and calyces with parenchymal cysts that donot communicate with the collecting system

Newborn shows no normal renal parenchyma and the right renal fossa filled with multiple simple appearing cystic structures c/w MCDK. The cysts did NOT communicate thereby excluding hydronephrosis

MECKEL GRUBER SYNDROME : occipital encephalocele, polydactyly, cystic dysplastic kidneys

MULTILOCULAR CYSTIC NEPHROMATumor of primitive renal

tissue originating from metanephric blastaema

Pathology – cyst with septa that contain renal tissue of variable maturity

Bimodal age distribution. Under the age of 5 years,

cystic nephroma occurs most frequently in males, whereas the adult group has a female predominance (91%) and mean age of 55 years

Septate cystic mass with multiple loculations, hairlike septa,peripheral and curvilinear calcifications,irregular borders, and minimal contrast enhancement.

Extension into the central sinus and into the renal pelvis can also be found

IVU – Multiple non enhancing areas bulging into renal pelvis

USG/CT/MRI – Well defined multiloculated mass with an

apparent capsuleLittle or no enhancementCalcification is usually not a feature

D/D : OTHER MULTILOCULAR CYSTIC LESIONS

DIFFERENTIALS

Septated renal cystInflammatory – renal abscess focal xanthogranulomatous

pyelonephritis hydatid diseaseSegmental multicystic kidneysTumors – cystic renal cell carcinoma Wilm’s tumor

UNILATERAL/LOCALISED RENAL CYSTIC DISEASEOne kidney is replaced by renal cysts and

other kidney is normal.Represents dilated ducts and tubulesNo liver cysts, No renal failure, normal

excretion of contrast

Cysts are seen to be separated by enhancing bands of normal renal parenchyma.

Individual smaller cysts are often present in the renal parenchyma adjacent to main loculated mass.

LOCALIZED CYSTIC DISEASE CYSTIC NEOPLASM

Unencapsulated : no capsule between cluster of cysts and renal parenchyma

Several small parenchymal cysts not contained within the main cluster of cysts

No mural irregularities

EncapsulatedMural irregularities

may be present

Localized cystic disease of kidney with multiple simple cysts separated by attenuated enhancing renal tissue (arrow).

Well-encapsulated mass in middle portion of left kidney with multiple enhancing septae (solid arrow). Mass of cystic locules is encompassed in single large encapsulated mass (open arrow). Enhancing tissue seen in lesion represents tumor tissue.

ACQUIRED CYSTIC DISEASE OF KIDNEY

INCIDENCE :Upto 80% of patients on chronic hemodialysis

or peritoneal dialysis develop renal cystsUsually after 5-10 years of HD8-16% develop neoplasm

CT is modality of choice

Multiple small or moderate size cysts

Affected kidneys are small

Atleast 3 cysts in each kidney who has CRF not due to hereditary renal cystic disease

Cysts both in cortex and medulla

There is increased incidence of RCC in patients undergoing dialysis.

Small RCC is more common than large masses

More in males as compared to females

CYSTS SECONDARY TO NON MALIGNANT RENAL PATHOLOGY

OBLITERATIVE PYELONEPHRITIS

Constriction of major or minor calyx produces cyst like structures

Similar appearance seen in tuberculosis

HYDATID CYST

ETIOLOGY :Echinococcus granulosisE multilocularis

Three types :

Closed cystPseudoclosed cystOpen cyst

CLOSED CYSTHave an intact cyst lining

and adventitia and do not communicate with the renal collecting system

Rounded mass (with or without calcification) causing elongation and splaying of the infundibula and calyces and, occasionally, obliteration of one or more calyces from pressure.

PSEUDOCLOSED CYST Exposed cyst with

absence of pericyst; the cyst is in close contact with urine.

Contrast media can interpose itself in crescent-like fashion in the space between the laminated ectocyst and the pericyst, producing the "goblet" or "wine-glass" sign (Surraco's sign)

OPEN TYPE Resulting from

rupture and discharge of daughter cysts

Communicating with the renal collecting system, contrast medium from either an intravenous or retrograde urogram can spread around the cyst or fill it 

In this open type of hydatid cyst, an intermittent or permanent communication exists between the hydatid and the pyelocalyceal system so that contrast medium flows directly into the cyst. Usually there is a typical mottled appearance of contrast, insinuating itself among a mass of daughter cysts but, occasionally, if the cyst contents are tightly packed, the contrast will be compressed between the contents and cyst wall to produce an extensive false crescent sign.

MILK OF CALCIUM RENAL CYSTNot a true cystCommunicating or closed off calyceal diverticulum Lined with trasitional epitheliumContains particulate colloidal suspension of various

calcium saltsPlain X ray

Supine position – full moon signHorizontal beam – half moon

US/CT/MRIHalf moon shift

Echogenic debris layering at the dependent part of a small cyst. There is change in the fluid-debris interphase with change in position. There is minimal acoustic shadowing due to a relatively large amount of calcium debris.

PSEUDOCYSTURINOMA (Uriniferous Perirenal Pseudocyst)

Any obstructive process may cause extravasation into perirenal spaces

Wall is formed by the fibrous capsuleMay cause secondary ureteral obstrction

CALYCEAL CYST (DIVERTICULUM)An intraparenchymal cavity lined

by transitional epithelium which communicates with a minor calyx, either centrally or at fornix

Do not receive any drainage from nephrons

IVU – well defined opaque rounded area adjacent but peripheral to a minor calyx

D/D – small cyst & hydrocalyx RISK – calculus, infection &

hematuria

PYEL0GENIC CYST

Similar to calyceal diverticulum but connect to pelvis proper

D/D - Hydropelvis

RENAL SINUS CYSTS/ EXTRAPARENCHYMAL

PARAPELVIC CYST – simple renal cyst originating from the renal parenchyma, which are primarily expanding within the renal sinus

PERIPELVIC CYST – cysts originating from the sinus structures. Most likely lymphatic in origin

PARAPELVIC CYSTUsually single or fewResemble simple renal cortical cyst in

morphologyMay cause compression of the pelvicalyceal

system resulting in hydronephrosis

PERIPELVIC CYSTUsually bilateralLymphatic in originMultilocular or unilocularWater attenuation cysts closely abutting

pelvis and infundibuliDon’t communicate with renal collecting

system

Differentiation from hydronephrosis/dilated renal pelvis is made on CECT scan ( surrounding halo of renal sinus fat) and delayed images.

D/D

Renal sinus lipomatosis (fat attenuation )Lymphoma or invasive transitional cell

carcinoma (soft tissue attenuation)

CYSTS ASSOCIATED WITH MALIGNANCY

3 MAIN AREAS

ACQUIRED CYSTIC RENAL DISEASEVHLTUBEROUS SCLEROSIS

CYSTIC RENAL CELL CARCINOMAAbout 10% of RCC mainfest as fluid filled

cystic mass

FOUR PATTERNS

Intrinsic unilocular cystic growth Intrinsic multilocular cystic growth Origin in the epithelium of a simple cystCystic necrotic tumor

Cystic RCC is seen on MRI and CT as a water-attenuation mass with an enhancing thick wall or septa sometimes with

associated soft-tissue nodules Nodular and septal enhancement is the

most sensitive finding to discriminate cystic RCC from complex benign lesions .

MULTILOCULAR CYSTIC RCC20-76 years of ageLow grade tumorCharacterized by septate variably sized

cysts separated from the kidney by a fibrous capsule. The cyst

fluid may be serous or hemorrhagic and thus can be of water attenuation or higher.

Asymmetric septal thickening may be seen May show septal or wall calcification

Cystic clear cell carcinoma is distinguished from multilocular cystic RCC by the presence of fewer loculations,thicker and more nodular septa, and expansile

enhancing mural nodules.

MIXED EPITHELIAL AND STROMAL TUMORBenign neoplasmCharacterized by a biphasic proliferation of

epithelium and stroma and admixed solid and cystic regions that have variable cellularity and growth patterns.

Tumor nearly always occurs in women (≈ 7:33 male-to-female ratio), especially in perimenopausal women (median age, 52 years

Bosniak III or IV lesion with septa, curvilinear calcifications, and a delayed enhancing solid component. Areas of T2 hypointensity suggesting fibrotic component may be seen.

SYNDROMES ASSOCIATED WITH RENAL CYSTS

LAURENCE MOON BIEDL SYNDROME Obesity MR Retinitis pigmentosa Hypogonadism

TUBEROUS SCLEROSIS MR Renal AML Renal cysts Hamartomas

VON HIPPEL LINDAU DISEASE Cerebellar hemangioblastomas Retinal angiomas Pancreatic cysts Islet cell tumors Phaeochromocytoma Endolymphatic sac tumors Cystadenomas of epididymis Multifocal renal carcinomas and renal cysts

A CHECK LIST FOR CYSTS Age Chief symptom

Size Shape Number Location Margins Contents Walls Septa Calcification Solid areas Vascularity Enhancement Relation to Pelvis, Renal artery

and vein

USG Hyper/Iso/HypoechoicComplexThrough transmission

CTHyper/Iso/HypodenseComplexHU

MRIHyper/Iso/HypointenseComplexApperances on T1, T2,

VIBE

APPROACH TO AN INCIDENTAL RENAL MASS

THANK YOU ALL