6. Simple Cyst
CT and MRI
near water density (< 10 HU)
Check HU’s of other water
thin, smooth wall
homogeneous
No enhancement
MRI>CT
Veritas tip – test yourself
before ROI
Pitfall – beware of Papillary
RCC
7. Simple Cyst
Too small to characterize (subcentimeter) renal
hypodensity
2 points:
OK to say very likely cyst and BIB it
Although cant get water HU’s
A 5 mm cyst is more hypodense to your eye than 5 mm solid
lesion
9. Complicated Renal Cyst
Simple cysts may become infected or
hemorrhage/trauma
US/CT/MRI
Thick walls; calcifications, septations, debris or increased
attenuation
And so, overlaps the appearance of cystic RCC
And therefore Bosniak Classification
10. 56 y/o with renal mass
Hemorrhagic cyst
at surgery
12. Hyperdense Cyst
Benign cyst containing blood products (clotted, old not just acute)
50 -90 HU (hyperdense to water or kidney)
if no NCCT, can be isodense or hypodense to kidney on CCT
50% appear cystic( a few echoes), but may not
US
CT Criteria
< 3cm
smooth wall (must extend beyond margin to evaluate)
rounded; sharp margins
**** NO SIGNIFICANT ENHANCEMENT ****
15. Hyperdense Cyst
Must distinguish from RCC
if strict CT criteria or US, then
some stop (II) or some follow
(IIF)
if comes very close (intrarenal,
3.5 cm, elderly) could follow
(IIF)
if doesnt meet criteria, “cannot
RO RCC”
New Data helpful Too
>70HU noncontrast
16. Bosniak Classification
Most problematic renal masses are cystic
Bosniak created a classification scheme to guide
proper management
Classification
I - simple cyst
II - minimally complicated (1 or 2 thin,
“nonenhancing”septi, delicate Ca++ in septi or wall;
hyperdense)
III - thick walls or Ca++, thick septi, nodules
IV - definitely malignant (necrotic masses, etc.)
22. Bosniak Classification
Management
I - stop
II - stop or follow Up (IIf)
III & IV - surgery
Although most III will be benign, 30% will be cancer
Problems
Category II lesions (at least one study showed 4/5
malignant)
Interobserver variability between II and III
23. Cysts and Cancer
3 main areas
Acquired cystic kidney disease (ACKD)
Tuberous Sclerosis (TS)
Von-Hipple Lindau (VHL)
24. Acquired Cystic Renal Disease
Development of cysts and occasional neoplasms in
patients with CRF
Can occur without dialysis (10%) but very common in
patients with dialysis (either hemo or peritoneal)
? prolongs lifespan so cysts develop
50% at 5 yrs, 90% at 10 years
Impact of transplant
controversial
cysts - some regress, some dont
neoplasms - again controversial
25. Acquired Cystic Renal Disease
Findings
Cysts
Neoplasms
small early; enlarge
and multiply in time;
can mimic ADPCKD
commonly Ca++,
hemorrhage
definite increased risk
with CRF, again esp.
dialysis
often indolent in
nature (papillary RCC)
kidneys small;
atrophic; hyperechoic;
no other cysts
26. Tuberous Sclerosis
Renal manifestations
occur in majority
Cysts – 15-50%
AML’s – 80%
Neoplasm (RCC)
When occur tend to be in
young children
Controversial whether
increased incidence
predisposition suggested by
younger age and bilateral
nature
No extrarenal cysts
Renal cysts in a 10-month-old with TS.
28. Multicystic Dysplastic Kidney
Congenital, non-hereditary dysplasia
characterized by renal parenchyma replaced by
multiple cysts
due to dysplastic ureteral bud
Clinical
May present as abdominal mass in child or incidental in
adult
** 10-30% incidence of contralateral anomaly, esp UPJ
and reflux**
29. Multicystic Dysplastic Kidney
Types
pelvoinfundibular atresia
(most common) - atretic
renal pelvis and ureter;
cystic renal mass
Hydronephrotic type
(rare) - ureteral atresia
but dilated pelvis
segmental (rare) - in
duplicated system
30. Multicystic Dysplastic Kidney
Findings
No function
multiple noncommunicating cysts replacing kidney
Usually no large central cystic area (UPJ)
large in child
Small to large, often Ca++ in adult (fails to grow)
MUST evaluate contra-lateral side
40. Autosomal Recessive Polycystic
Kidney Disease
Clinically
Classically classified as perinatal, neonatal, infantile and
juvenile; now felt to be too rigid
Spectrum of expression with predominately renal and
minimal hepatic disease when presentation in perinatal
period; and predominately hepatic and milder renal
disease when presenting in the older child
An individual can present anywhere along the spectrum
41. Autosomal Recessive Polycystic
Kidney Disease
Imaging
Perinatal form (most common)
massive nephromegaly usually
without discrete cysts dominates
the imaging
Prenatal US - enlarged
hyperechoic kidneys; decreased
or absent bladder;
oligohydramnios
PF - flank masses; pulm.
hypoplasia with ptx
US - enlarged echogenic kidneys
with loss of CMJ
CT - nehpromegaly; striated
prolonged nephrogram
Liver US - usually normal or
slightly hyperechoic
44. Autosomal Recessive Polycystic
Kidney Disease
Imaging
Older child
The kidneys appear
normal or similar to
perinatal findings, only
milder; occ. discrete cysts
Liver US - hyperechoic;
may see cystic dilatation
of the biliary tree; changes
of portal HTN (HSM;
varices)
45. Medullary Sponge Kidney
Pathology
saccular 1-8mm dilatation of
the distal collecting ducts
with sluggish flow and
predisposition to stone
formation
Clinical
Young adults
usually asymptomatic except
stones
non-hereditary; nonprogressive
assoc. with Caroli’s,
ARPCKD; hemihypertrophy
46. Medullary Sponge Kidney
Imaging (PF, US and CT)
Medullary nephrocalcinosis
bilateral, unilateral or focal
“growing calculus sign”
Urolithiasis
Discrete linear collections in papilla on IVP
should be distinguished papillary blush - a nondiscrete blush
of contrast within the papillary which can be normal
53. Localized Cystic Disease
DDX
Abscess
MCDK
MLCN and CysticRCC
Kidney functions
normally
Normal interneving tissue
and lack of capsule
Should Follow
Can Grow
Multilocular cystic RCC – capsule
with enhancing tumorous septa
AJR 2001; 176:843-849
54. Renal Sinus Cysts
2 types
parapelvic cyst
peripelvic cyst
simple parenchymal cyst which projects into the sinus
extraparenchymal cyst arising in sinus (?origin; ?
congenital and lymphatic etiology)
Imaging (peripelvic)
May be multiple and bilateral, unilocular or
multilocular; usually small and insinuating
smooth splaying of collecting system
rarely results in obstruction and hydronephrosis
Go to school - a common vexer in radiology - probably cyst on US.
Take advantage of opportunities to look at US of known cysts to get better
ie Seek veritas
Figure 9. Multicystic dysplastic kidney. (b) US scan shows a different pattern with larger cysts and more echogenic, dysplastic parenchyma.
Multicystic dysplastic kidney in a 23-week-old fetus. (a) Sagittal MR image shows a large, multicystic structure in the left renal fossa (arrowhead). The cysts vary in size and are not connected, findings that are consistent with multicystic dysplastic kidney. The stomach is seen just inferior to the diaphragm (arrow). (b) Sagittal MR image shows a normal right kidney (arrowhead).
Hi-res us now shows cystic areas
Prenatal us on left with echogenic enlarged kidneys, ct on right in newborn