The document discusses guidelines for accurately evaluating renal masses using CT and MRI imaging. It emphasizes the importance of performing unenhanced scans prior to contrast administration to identify enhancement within masses. For CT, a difference of 15-20 HU between unenhanced and enhanced images is considered evidence of enhancement. For MRI, subtraction of unenhanced and enhanced images allows clear identification of enhancement. The document provides guidance on differentiating benign from malignant masses and determining if a mass requires surgical intervention. Pseudotumors and infiltrative lesions can mimic renal cell carcinoma and require careful evaluation.

1. RENAL MASSESRENAL MASSES
G.Naga SathishG.Naga Sathish

2. EVALUATING RENAL MASSESEVALUATING RENAL MASSES
TECHNIQUE AND QUALITYTECHNIQUE AND QUALITY
 The accurate diagnosis of a renal mass is
dependent on many factors, including the
clinical history, the nature of the imaging
findings, the experience of the radiologist, and
the quality of the examination

3. CT SCANNINGCT SCANNING
 When CT scanning is performed specifically to evaluate a known
renal mass, the study must include an unenhanced examination
prior to the administration of intravenous contrast material.
 By using a power injector, administer 150 mL of intravenous
contrast material (75 mL for patients with a single kidney) injected
at a minimum rate of 3 mL/sec to ensure that a high concentration
of contrast material is present within the renal parenchyma during
the postcontrast acquisition.
 By using a multi–detector row CT scanner, contrast material–
enhanced imaging is routinely performed during the
corticomedullary and nephrographic phases of enhancement by
using scanning delays of 40 and 100 seconds, respectively.
 The corticomedullary phase of enhancement is used to perform
three-dimensional (3D) reconstructions and to depict the renal
vasculature for urologists who perform laparoscopic nephrectomy.
 This phase is also useful to help differentiate a renal pseudotumor
from a renal neoplasm

4. Transverse contrast-enhanced CT scans in a 54-year-old woman with a renal cell
carcinoma.
(a) Corticomedullary phase scan shows focal thinning (arrow) of the renal cortex, but
a definite renal mass is not identified in this early phase of renal enhancement.
(b) Nephrographic phase scan shows a 1.5-cm intrarenal mass (arrow), which was
surgically proved to be renal cell carcinoma.

5.  MR IMAGINGMR IMAGING
 All sequences are performed during an end-expiratory breath hold,
and, for those patients who cannot hold their breath for a sufficient
period of time (approximately 20 seconds), 2 L/min oxygen is given
via a nasal cannula.
 By using cushions, the patients’ arms are elevated anterior to the
level of their kidneys to avoid a wraparound artifact in the coronal
acquisitions.

6.  In all patients referred for evaluation of a renal mass,
MR angiography, MR venography, and MR urography
are performed by using an oblique coronal breathhold
3D fat-suppressed T1-weighted spoiled gradient-echo
sequence before and at multiple time points
 after administration of 19 mL of a gadolinium-based
contrast material. The 3D slab should be kept as thin as
possible, without excluding any of the structures that
need to be evaluated, to maximize through-plane spatial
resolution

7.  To evaluate the renal parenchyma and a renal mass, a
separate 3D breath-hold fat-suppressed T1-weighted fat-
saturated spoiled gradient-echo sequence is performed in
the transverse plane before and after contrast material
administration.
 The postcontrast acquisition is performed between MR
venography and MR urography.
 For the characterization of renal masses and to determine
the presence or absence of enhancement, we recommend
an imaging delay of 3–5 minutes.

8. Transverse fat-suppressed T1-weighted MR images in a 68-year-old man with a complex
renal mass.
(a) Unenhanced image shows a hemorrhagic mass (arrows) at the upper pole of the left
kidney.
(b) (b) Gadolinium-enhanced image shows enhancement of a thickened wall (arrows), but it
is difficult to determine if there is any internal enhancement within the mass because of
its heterogeneous signal intensity a. A small portion of enhancing renal parenchyma
(arrowhead) is present anterior to the mass.
(c) (c) Subtracted image (gadolinium-enhanced image minus unenhanced image) shows
nodular enhancement (large arrow) along the wall of the mass and internal enhancement
(small arrows), confirming the diagnosis of a renal cancer.
A papillary renal cell carcinoma was diagnosed at surgical pathologic evaluation.

9.  When asked to specifically evaluate a known renal mass at
MR imaging, the imaging planes of the sequences may be
modified to best depict the mass.
 For masses at the poles of the kidney, the coronal and
sagittal planes are advantageous because the relationship
of the mass to the kidney is not optimally demonstrated in
the transverse plane.
 Similarly, the transverse and sagittal planes best depict a
mass in the anterior or posterior aspect of the kidney,
 and the transverse and coronal planes best depict a mass
in the medial or lateral aspect of the kidney.
 This approach is most important when evaluating a patient
with a solitary kidney that contains a renal neoplasm that is
amenable to partial nephrectomy

10. Differentiating enhancing from nonDifferentiating enhancing from non
enhancing renal massesenhancing renal masses
 Most important criteriaMost important criteria
 Renal mass enhancement is dependent on multiple factors,
including the amount and rate of the contrast material injection,
the imaging delay, and the nature of the tissue within the mass
 When there is a question of whether a mass enhances at CT,
Hounsfield unit measurements should be obtained and compared
on the unenhanced and contrast- enhanced images.
 conventional (nonhelical) CT scanners, a difference of 10 HU was
suggested as evidence of enhancement
 At present, there is no universally agreed upon specific number
that can be used as definitive and unequivocal evidence of
enhancement within a renal mass, and it has been proposed by
many authors that the previously used threshold of 10 HU should
be increased to 15–20 HU ,
 while others believe that a 10-HU threshold is still valid .
 A renal mass that enhances 10–20 HU is indeterminate and needs
further evaluation for definitive characterization.

11.  In some cases, use of the gallbladder or an obvious simple
renal cyst as an internal reference standard and
comparison of the Hounsfield unit measurements of that
reference standard (on the unenhanced and contrast-
enhanced images) is no unanimously accepted way of
determining renal mass enhancement.
 MR imaging.
 image subtraction(gadolinium-enhanced fat-suppressed
T1-weighted image minus unenhanced fat-suppressed T1-
weighted image) an easy, reliable, and reproducible
method of demonstrating the presence or absence of
enhancement within a renal mass

12. Pit falls of enhancementPit falls of enhancement
 Larger ROI (region of interest) measurements can be
used in homogeneous solid masses
 However, cystic, complex, or necrotic masses require
multiple small ROI measurements to be obtained from
all portions of the mass, similarly placed on both the
unenhanced and contrast-enhanced images

13.  renal cysts on occasion may show artificial apparent
enhancement of 10 HU or more (pseudoenhancement) at
contrast-enhanced CT, and this may potentially lead to the
mischaracterization of a renal cyst as a renal neoplasm.
 The phenomenon of pseudoenhancement at CT is
secondary to the image reconstruction algorithm used in
helical scanners to adjust for beam-hardening effects
 Pseudoenhancement most often occurs when the cyst is
surrounded by renal tissue during the peak level of renal
parenchymal enhancement.
 Many of these cysts are small (2 cm) and completely
intrarenal.
 Pseudoenhancement is relatively easy to suspect when a
mass appears as a simple cyst and measures 10 HU or less
on the unenhanced CT scan.

14. Images in a 28-year-old man with a right
renal mass.
(a) Transverse unenhanced CT
scan shows 1.4-cm low-attenuating mass
(arrow) that measures 15 HU in the upper
pole of the right kidney.
(b) On the transverse contrast-enhanced
CT scan, renal mass measures 32 HU.
Although it could represent a hypovascular
neoplasm, this intrarenal mass is small and
associated with a dense nephrogram, and
pseudoenhancement of a renal cyst was
suspected.
(c) Coronal T2-weighted MR image shows
the mass to be uniformly hyperintense,
suggesting a simple cyst.
(d) Transverse subtracted MR image
(gadolinium-enhanced fat-suppressed
T1-weighted image minus unenhanced fat-
suppressed T1-weighted image) shows no
enhancement within the mass, confirming
the diagnosis of a simple cyst

19. Differentiating surgical from nonDifferentiating surgical from non
surgical renal massessurgical renal masses
 In most cases, it is possible to preoperatively differentiate those
renal masses that require surgery (renal cell carcinoma, invasive
transitional cell carcinoma, and oncocytoma) from those that do not.
 Renal cell carcinoma and oncocytoma are indistinguishable from
each other at imaging.
 However, angiomyolipoma, lymphoma, metastatic disease, renal
anomalies, and other pseudotumors can all mimic renal cell
carcinoma.
 Frequently it is possible to make this differentiation by using the
imaging findings alone, but often the clinical history can be very
important in making the correct diagnosis.
 In fact, before making a diagnosis of renal cell carcinoma, one
should be satisfied that none of these possible mimickers of renal
cell carcinoma are potentially present

20.  The differentiation of an angiomyolipoma from
a renal cell carcinoma is important because, in
most cases (excluding very large lesions or those
that are bleeding), angiomyolipomas do not need
to be surgically removed.
 The diagnosis of an angiomyolipoma is made by
demonstrating fat within a solid renal mass

21. Transverse CT scans in a 45-year-old woman with a renal mass incidentally found on
an abdominal CT scan.
(a) Contrast-enhanced scan shows a 1.8-cm enhancing mass in the right
kidney. The lesion was thought to represent a renal cell carcinoma. However, because of a
relatively low-attenuating region (arrow) in the central portion of the mass
(b) Unenhanced scan shows a minimal amount of fat (arrow) (30 HU),
diagnostic of an angiomyolipoma.
The small amount of fat within this mass is obscured on a.
Also, the mass is slightly higher in attenuation than the adjacent renal parenchyma, a
finding typical of the myomatous component of the angiomyolipoma

22.  A small number of angiomyolipomas (hamartomas) do
not contain macroscopic fat (angiomyomas), and the
imaging differentiation from a renal neoplasm is
impossible.
 These lesions often have a higher attenuation than that
of renal tissue (on the unenhanced CT scan) or may
demonstrate homogeneous and prolonged enhancement
,
 but these findings are not specific enough to make a
confident diagnosis of a non–fat-containing hamartoma.
 The term “minimal fat” angiomyolipoma has been used in
the literature to describe angiomyolipomas with
microscopic fat and without demonstrable macroscopic
fat

23.  Angiomyolipomas rarely contain calcification and,
therefore, a diagnosis of angiomyolipoma should not be
made if a lesion contains fat and calcium.
 In such cases, a renal cell carcinoma must be
considered likely
 it is also possible that a large renal cell carcinoma may
engulf a small portion of fat in the renal sinus or
perinephric fat, or even a small adjacent
angiomyolipoma, giving the appearance of a larger
angiomyolipoma containing a small amount of fat.
 It may not be possible to distinguish these types of
masses from each other.

24. Infiltrating renal massesInfiltrating renal masses
 Infiltrating neoplasms lymphoma, inva-sive
transitional cell carcinoma, metastatic disease
(particularly from lung cancer), and renal cell
carcinoma (especially the sarcomatoid subtype) .
 These malignancies infiltrate into the renal
parenchyma, which results in a region of
diminished nephrogram with indistinct margins.

25.  Lymphoma can have a variable appearance and
may on occasion resemble renal cell carcinoma.
 Most frequently, it manifests as bilateral solid
renal masses, and in a patient with systemic
lymphoma the proper diagnosis is not difficult.
 a renal mass that does not have the imaging
characteristics of lymphoma, biopsy of the mass
is indicated prior to systemic therapy

26. Transverse gadolinium-enhanced fat-suppressed T1-weighted MR image in an
84-year-old woman with a renal mass shows a solid enhancing mass (long
arrows) in the left renal sinus, infiltrating into the kidney.
Large left periaortic lymph nodes (short arrow) are also present.
Results at biopsy of the lymphadenopathy confirmed lymphoma

27.  Transitional cell carcinoma of the kidney is usually diagnosed
by detecting a filling defect in the collecting system that
enhances on a CT or MR image.
 However, a small percentage of transitional cell carcinomas
are anaplastic and infiltrate into the renal sinus and kidney
parenchyma).
 These masses are very aggressive and have a poor
prognosis, often manifesting with lymph node metastases.
 The differentiation from other infiltrative lesions (which may
also involve the renal sinus) is critical because
transitional cell carcinoma- nephroureterectomy,
lymphoma systemic -chemotherapy
infiltrative renal cell carcinoma -nephrectomy.

 Biopsy of infiltrative transitional cell carcinoma should be
avoided if possible because of the propensity for seeding

28. Transverse contrast-enhanced CT scan in a 73-year-old man with transitional
cell carcinoma in the right kidney shows a tumor that arises from the right
renal collecting system and infiltrates into the renal sinus and kidney
parenchyma.
Findings are consistent with invasive transitional cell carcinoma.
Note large lymph node metastases (arrow) posterior to the inferior vena cava.

29.  Metastatic disease to the kidney typically
manifests as multiple bilateral renal masses,
often associated with metastatic disease to other
organs

30. Pseudo tumors and renal massPseudo tumors and renal mass
mimikersmimikers
 This group includes congenital anomalies and
inflammatory masses
 A renal pseudo tumor represents normal renal tissue that
may mimic a renal neoplasm.
 Congenital pseudotumors are normal variants which
include prominent renal columns of Bertin, renal
dysmorphism, and dromedary humps,
 while acquired pseudotumors represent hypertrophied
normal renal parenchyma assuming a tumorlike
appearance adjacent to parenchymal scarring

31.  it is advantage of the corticomedullary phase to demonstrate the
normal corticomedullary differentiation in the suspected “mass.”
 Inflammatory masses, including focal pyelonephritis and renal abscess,
may also mimic the appearance of a renal neoplasm.
 However, with the appropriate clinical history the correct diagnosis
usually becomes apparent.
 the differentiation of a cystic renal neoplasm from a subacute or
chronic renal abscess can be difficult when the typical clinical findings
of infection are not present.
 If a remote history of fever, leukocytosis, or urinary tract infection is
obtained, needle aspiration should be performed, and if pus is
recovered, percutaneous drainage can be instituted.
 However, if blood or necrotic debris is recovered, surgical removal is
indicated

32. Transverse contrast-enhanced CT scans in a 63-year-old man with a left renal
pseudotumor.
(a) Nephrographic phase scan shows a focal “mass” (large arrow) adjacent to a scar (small
arrow) in the left kidney. The left kidney is smaller than the right kidney, and the mass
enhances identically to the renal parenchyma.
(b) Corticomedullary phase scan shows corticomedullary differentiation in the renal
“mass,” diagnostic of localized hypertrophy of normal renal parenchyma

33. Cystic renal massesCystic renal masses
 complex cystic renal masses may be initially detected
with US
 they cannot be accurately characterized by using US
alone.
 Therefore, we do not use US in the evaluation of cystic
renal masses, with the exception of proving that a renal
mass is a simple cyst (such as in a case of suspected CT
pseudoenhancement).
 On the other hand, MR imaging does have a role in
evaluating cystic renal masses

34. Bosniak ClassificationBosniak Classification

37. Management of renal cysticManagement of renal cystic
disease according to Bosniakdisease according to Bosniak
ClassificationClassification
category Management
I , II Ignore & No need for follow up
II F Follow up
III , IV Surgical excision

38.  Autosomal dominant polycystic kidney disease:Autosomal dominant polycystic kidney disease:
 HeridiatryHeridiatry
 Htn commonHtn common
 Aortic aneurysm, dissection, and valvular heart diseaseAortic aneurysm, dissection, and valvular heart disease
more commonmore common
 Average age of onset of renal failure 6Average age of onset of renal failure 6thth
to 7to 7thth
decadedecade
 Flank pain, hematuria uti , nephrolithiasisFlank pain, hematuria uti , nephrolithiasis
 Detection of cysts in other organs are useful clue inDetection of cysts in other organs are useful clue in
diagnosis.diagnosis.
 Bilateral involvement commonBilateral involvement common
 Calcf commonCalcf common

41.  Aquired cystic disease of kidneyAquired cystic disease of kidney
 Common in pts with hemo or peritoneal dialysisCommon in pts with hemo or peritoneal dialysis
 80 %reported after 380 %reported after 3rdrd
year of dialysisyear of dialysis
 Hyperplasia of tubular epithelium resulting inHyperplasia of tubular epithelium resulting in
blokade and dilatation of nephrons leading toblokade and dilatation of nephrons leading to
cyst formationcyst formation
 RCC 40 times more common in pts on dialysisRCC 40 times more common in pts on dialysis

44. benign renal massesbenign renal masses
 The 2004 World Health Organization (WHO)
classification schemata categorizes benign renal
neoplasms on the basis of histogenesis (cell of
origin) and histopathology .
 Renal neoplasms are thus classified into renal
cell, metanephric, mesenchymal, and mixed
epithelial and mesenchymal tumors.

45. Renal cell neoplasmRenal cell neoplasm
 Oncocytoma:Oncocytoma:
 Peak age of incidence 70 yrsPeak age of incidence 70 yrs
 Males > femalesMales > females
 Oncocytomas typically appear as solitary, well-demarcated,
unencapsulated, fairly homogeneous renal cortical tumors.
 Bilateral, multicentric oncocytomas are seen in hereditary
syndromes of renal oncocytosis and Birt-Hogg-Dubé
syndrome (in association with the chromophobe subtype
and other RCC subtypes.

46.  A characteristic central stellate fibrotic scar (more often
seen with large tumors) is seen in up to 33% of tumors
 Hemorrhage may be found in up to 20% of cases.
 A spoke-wheel pattern of feeding arteries associated
with a homogeneous nephrogram is a characteristic
finding on catheter angiography .
 However, oncocytomas are indistinguishable from
renal cell carcinomas on the basis of imaging findings
alone.

47. 64-year-old man with histologically proven oncocytoma. K = kidney.
A, Axial fat-saturated, T2-weighted gradient-refocused echo image shows expansile,
solid right renal mas (arrow) with hyperintense central scar (S).
B, Axial fat-saturated, gadolinium-enhanced T1-weighted 3D gradient-refocused
echo image shows right kidney mass (arrow) with hypointense central scar (S)

49.  Papillary adenoma:Papillary adenoma:
 Most common epithelial neoplasmsMost common epithelial neoplasms
 Commonly found in pts with aquired renal cysticCommonly found in pts with aquired renal cystic
disease & pts undergoing long term hemodialysisdisease & pts undergoing long term hemodialysis
 papillary adenomas measure 5 mm or less .
 They are usually subcapsular and solitary.
 Adenomas are histologically characterized by papillary
or tubular cytoarchitecture and frequent psammoma
bodies

50. Mesenchymal neoplasmMesenchymal neoplasm
 Angiomyolipoma:Angiomyolipoma:
 Most common benign mesenchymal neoplasmMost common benign mesenchymal neoplasm
 Composed of variable proportions of blood vessels,
smooth muscle, and adipose tissue .
 Renal AMLs consist of two distinct histologic subtypes,
classic and monotypic epithelioid.

51.  Epithelioid AMLs typically do not show
macroscopic fat and appear as soft-tissue masses
and are thus indistinguishable from other solid
renal masses.
 This rare subtype of AML is potentially
malignant and may exhibit aggressive biology,
including recurrence, metastasis, and death

52.  Classic AML may occur either sporadically or in
association with tuberous sclerosis complex (TSC).
 Sporadic renal AMLs show a 4:1 female preponderance and
are more likely to be solitary and symptomatic
 Large tumor size (> 4 cm) and diameter of the intralesional
aneurysms (> 5 mm) correlate directly with tumor-related
hemorrhage in AMLs
 On sonography, small AMLs appear uniformly hyperechoic
without a hypoechoic rim or intralesional cysts .
 Large AMLs appear as variegated masses with macroscopic
fat, hemorrhage, and hypervascular soft-tissue components

53.  The presence of macroscopic fat on CT or MRI is
characteristic of AMLs.
 Loss of signal intensity on frequency-selective fat-
suppressed MRI definitively identifies macroscopic fat .
 However, a multitude of renal neoplasms, including
RCC, oncocytoma, lipoma, and liposarcoma, may show
either intratumoral fat or engulfed perirenal fat
 Recent studies indicate that in contradistinction to
RCCs, AMLs with minimal fat show uniform,
prolonged contrast enhancement and a higher signal
intensity index on double-echo, chemical shift FLASH
MRI

55. 43-year-old woman with
hematuria. Transvers sonogram
shows uniformly echogenic mass
(arrows)
in upper pole of left kidney (K)
that was proven to be
angiomyolipoma
58-year-old woman with
angiomyolipoma of kidney. Sagittal
contrast-enhanced CT scan shows
exophytic renal mass (arrows) with foci
of macroscopic fat (arrowhead).

56. 38-year-old woman with documented tuberous sclerosis complex and renal
angiomyolipomas.
A, Axial in-phase T1-weighted 2D gradient-refocused echo MR image shows
bilateral multicentric renal masse that have increased signal intensity (arrows).
B, Axial fat-saturated T2-weighted 2D gradient-refocused echo MR image
shows marked drop in signal intensity of masses (arrows)

57.  Hemangioma:Hemangioma:
 rare benign mesenchymal neoplasm that consists of
multiple endothelium-lined, blood-filled vascular spaces .
 It commonly affects young adults with no specific sex
predilection.
 Recurrent episodes of hematuria and renal colic are typical
presenting symptoms;
 may be associated with systemic syndromes such as Sturge-
Weber and Klippel-Trénaunay and with systemic
angiomatosis .
 Cavernous hemangiomas are more common than the
capillary variants

58.  Hemangioma frequently arises from the renal pyramids
or the pelvis.
 Hemangiomas show variable echogenicity on
sonography
 hyperintensity on T2-weighted MRI
 Contrast-enhanced CT and MRI of renal hemangiomas
may show early, intense enhancement .
 Persistent contrast enhancement on delayed images is
fairly characteristic of renal hemangiomas

59. 60-year-old man with hematuria and histologically proven hemangioma.
A, Axial fat-saturated T2-weighted 2D gradient-refocused echo MR image shows
hyperintense left kidney mass in renal sinus (arrow).
B, Axial fat-saturated gadolinium-enhanced T1-weighted 3D gradient-refocused
echo MR image shows contrast enhancement of left renal sinus mass (arrows).

60.  Lymphangioma:Lymphangioma:
 Rare benign cystic tumorRare benign cystic tumor
 Often arises fromOften arises from peri pelvic regionperi pelvic region or renal sinus.or renal sinus.
 Renal lymphangioma may occur either as an isolated
finding or in association with perinephric or systemic
lymphangiomatosis.
 It may appear as a localized process or a diffusely cystic
lesion.
 typically appears as a well-demarcated, uni- or
multilocular cystic neoplasm that most commonly arises
from the renal sinus region or in the perinephric space

61. 47-year-old man with bilateral multiple renal sinuses and perinephric
lymphangiomatosis.
Unenhanced axial CT scan shows multicentric cystic masses in renal sinus
and perinephric spaces (arrows).

62.  LEIOMYOMA:LEIOMYOMA:
 Renal leiomyomas are rare benign smooth muscle neoplasms that mostly occur
in adults as incidental findings .
 Renal capsule is the most common target site of leiomyomas;
 rarely, leiomyomas originate from the renal pelvis or cortex.
 Leiomyomas of the kidney commonly appear as well-circumscribed,
homogeneous, exophytic solid masses that show uniform enhancement on
contrast-enhanced CT
 Larger tumors are heterogeneous because of hemorrhage and cystic or myxoid
degeneration
 Calcification is uncommon.
 However, the CT findings of leiomyomas of the kidney may be variable and
may include cystic, complex cystic–solid, or purely solid morphology [44].
 Renal leiomyomas may show hypervascularity on catheter angiography because
they are predominantly supplied by capsular vessels

63. 43-year-old woman with renal leiomyoma of capsular origin.
Axial contrast-enhanced CT scan shows large, fairly homogeneous
exophytic mass(arrows) arising from left kidney (K).

64.  JUXTAGLOMERULAR CELL NEOPLASM (RENINOMA)
 Juxtaglomerular cell (JGC) neoplasm is an extremely rare, benign renal neoplasm
of myoendocrine cell origin .
 The peak age of incidence is in the second and third decades and a 2:1 female
preponderance is seen.
 JGC neoplasm is clinically characterized by a triad of findings: poorly controlled
hypertension, hypokalemia, and high plasma renin activity
 JGC neoplasm typically appears as a unilateral, well-circumscribed, cortical tumor
that usually measures less than 3 cm.
 Despite profuse vascularity, JGC neoplasms appear hypovascular on
contrastenhanced CT and MRI, possibly because of renin-induced
vasoconstriction.
 JGC neoplasms may show delayed contrast enhancement.
 Imaging findings of JGC neoplasms are nonspecific and indistinguishable from
other solid renal neoplasms

65. 23-year-old woman with hypertensio refractory to standard treatment. Axial
unenhanced CT scan shows large, expansile right renal mass (arrow) that
was histologically proven to be juxtaglomerular cell neoplasm (reninoma).
K = kidney, M = mass

66. Mixed epithelial & mesenchymalMixed epithelial & mesenchymal
neoplasmneoplasm
 comprise two histologically distinct entities: mixed epithelial and stromal
tumors and cystic nephromas.
 Mixed Epithelial and Stromal Tumor
 Mixed epithelial and stromal tumors occur almost exclusively in
perimenopausal women (6:1 female preponderance);
 most patients are receiving estrogen therapy .
 Twenty five percent of the tumors present as incidental findings;
 most patients manifest nonspecific symptoms of flank pain and
hematuria.

67.  On imaging, mixed epithelial and stromal tumors typically
appear as expansile, complex, cystic–solid masses with
heterogeneous and delayed enhancement.
 The proportion of cystic and solid constituents varies in
any given case.
 The stromal component of the tumor is thought to be
responsible for the hypointense signal on T2-weighted MRI
with delayed contrast enhancement
 Large mixed epithelial and stromal tumors may herniate
into the renal pelvis.
 The tumors typically show benign biologic behavior without
recurrence or metastasis;
 however, aggressive mixed epithelial and stromal tumors
with sarcomatous transformation of the stromal component
have been described

68. 40-year-old woman with histologically proven mixed epithelial and
stromal tumor of kidney.
Axial contrast-enhanced CT scan shows large complex cystic left
kidney (K) mass (arrows) with septations and solid components.

69.  Cystic Nephroma
 Cystic nephroma is a benign cystic neoplasm that affects
predominantly middle-aged, perimenopausal women.
 Adult-onset cystic nephroma is histogenetically and morphologically
different from pediatric cystic nephroma
 Morphologically, cystic nephromas are composed of encapsulated,
noncommunicating cysts with thin septations.
 Septa show no enhancement. Calcft of septa may be seen
 cystic nephromas are characterized by the absence of a solid
component or necrosis.
 Cystic nephroma appears as a well-demarcated, solitary, multilocular
cystic lesion with thin septations.
 The cystic mass may protrude into the renal pelvis and cause
hemorrhage or urinary obstruction

71. 14—50-year-old woman with cystic nephroma.
A, Coronal contrast-enhanced CT scan shows lobulated, expansile, cystic
mass (M) in left kidney (arrow) that compresses calyces (C).

72. conclusionconclusion
 leiomyomas originate from the renalcapsule,
hemangiomas typically arise from the renal sinus.
 Approximately one third of large oncocytomas typically
show a central stellate scar.
 Cystic nephromas show septated cysts,
 macroscopic fat predominates in most
angiomyolipomas.
 metanephric adenomas are commonly solid.
 Mixed epithelial and stromal tumors consist of solid
areas and cysts that may herniate into the renal pelvis

73. Malignant lesionsMalignant lesions
 Renal cell carcinoma:Renal cell carcinoma:
 Pathologically adenocarcinomaPathologically adenocarcinoma
 Common in adultsCommon in adults
 MalesMales
 Associated with cigarrette smokingAssociated with cigarrette smoking
 Symptoms: pain hematuria, wt loss and abdominal distension.Symptoms: pain hematuria, wt loss and abdominal distension.
 Imaging: focal renal mass centered in renal cortex.Imaging: focal renal mass centered in renal cortex.
 Mass distorts the marginsMass distorts the margins
 Calcifications 25%. Common in larger lesions than smallCalcifications 25%. Common in larger lesions than small
 Calcftns: punctate, amorphous, linear or peripheralCalcftns: punctate, amorphous, linear or peripheral
 Often renal vein invasion. Thrombus may extend into ivc.Often renal vein invasion. Thrombus may extend into ivc.
 Thrombus may show arterial enhancement.Thrombus may show arterial enhancement.

75.  Do not usually metastasize when less than 3 cms.Do not usually metastasize when less than 3 cms.
 Mets: to liver, lung bone and nodes.Mets: to liver, lung bone and nodes.
 Liver mets often hypervascular.Liver mets often hypervascular.
 Mets to retro peritoneal space has poor prognosisMets to retro peritoneal space has poor prognosis
 MRI: typically mild hypointense to renal cortex on T1MRI: typically mild hypointense to renal cortex on T1
and mildly high T2 signal.and mildly high T2 signal.
 Lesion show enhancement.Lesion show enhancement.
 Most RCC’S haveMost RCC’S have a hypointense pseudo capsulea hypointense pseudo capsule at theat the
periphery of tumor.periphery of tumor.
 Mri sensitive for IVC thrombosis.Mri sensitive for IVC thrombosis.

80.  Staging:Staging: robsons classf:robsons classf:
 Involvement of gerotas fascia is a negitive clinicalInvolvement of gerotas fascia is a negitive clinical
indicator.indicator.
 Stage 1 : limited to renal capsuleStage 1 : limited to renal capsule
 Stage 2: gerotas fasciaStage 2: gerotas fascia
 Stage3: thickening of structures in peri nephric space.Stage3: thickening of structures in peri nephric space.
Renal vein invasions,ivc, adrenal mets or regionalRenal vein invasions,ivc, adrenal mets or regional
adenopathyadenopathy
 4:distant mets or spread to adjacent organs other than4:distant mets or spread to adjacent organs other than
adrenalsadrenals

81. Drawing of the anatomy of the retroperitoneal spaces at the level of the kidneys.
The anterior pararenal space (APRS) is located between the parietal peritoneum
(PP) and the anterior renal fascia (ARF) and contains the pancreas (Pan), the
ascending colon (AC), and the descending colon (DC). The posterior pararenal
space (PPRS) is located between the posterior renal fascia (PRF) and the
transversalis fascia (TF). The perirenal space (PRS) is located between the anterior
renal fascia and the posterior renal fascia.

82. Transitional cell carcinomaTransitional cell carcinoma
 Urothelial tumors are less common in upper urinaryUrothelial tumors are less common in upper urinary
tract.than RCCtract.than RCC
 Second most renal neoplasm in adultsSecond most renal neoplasm in adults
 Risk factors: nsaids, tobacco etc.Risk factors: nsaids, tobacco etc.
 Common in malesCommon in males
 Increased in horse shoe kidneyIncreased in horse shoe kidney
 Present with hematuriaPresent with hematuria
 Initial detection done on IVPInitial detection done on IVP
 Ocasionally usg may detect a collecting system lesion inOcasionally usg may detect a collecting system lesion in
calyces or renal pelvis.calyces or renal pelvis.

83.  3 general ct imaging appearance:3 general ct imaging appearance:
 Smal hypodense lesion in collecting systemSmal hypodense lesion in collecting system
 Soft attenuation value HU<40 less than calculi and clot.Soft attenuation value HU<40 less than calculi and clot.
 Enhance 10-50 huEnhance 10-50 hu
 Enhancemnt less than surrounding renal parenchymaEnhancemnt less than surrounding renal parenchyma
 Stippled calcificationsStippled calcifications
 Necrosis in large lesion uncommonNecrosis in large lesion uncommon
 Do not involve renal veinDo not involve renal vein
 May present as infiltrative renal massMay present as infiltrative renal mass
 Mass originates from centre of kidneyMass originates from centre of kidney
 Renal contour usually not disrupted unlike RCC (BEAN VSRenal contour usually not disrupted unlike RCC (BEAN VS
BALL)BALL)

84.  Thickening of collecting system urothelium or uretreralThickening of collecting system urothelium or uretreral
wall.wall.
 Thickening may be symmetric or eccentric.Thickening may be symmetric or eccentric.
 Expansion of collecting system above the areaExpansion of collecting system above the area
 Tumor insitu and limited to sub mucosa have bestTumor insitu and limited to sub mucosa have best
prognosis.prognosis.
 Stage2: invasion beyond subepithelial tissueStage2: invasion beyond subepithelial tissue
 Stage 3: muscularis, invasion of renal parenchyma,orStage 3: muscularis, invasion of renal parenchyma,or
peri pelvic/periureteral fat.peri pelvic/periureteral fat.
 Stage4: nodal involvement., organs bone and lungs.Stage4: nodal involvement., organs bone and lungs.

88. lymphomalymphoma
 Usually part of systemic diseaseUsually part of systemic disease
 Renal involvement is usually a symptamaticRenal involvement is usually a symptamatic
 Non hodgkins more common than hodgkinsNon hodgkins more common than hodgkins
 CT more sensitive than USGCT more sensitive than USG
 4 common presentations4 common presentations
 1: Multifocal renal lesions usually bilateral1: Multifocal renal lesions usually bilateral
 Enhancement less than surrounding renal parenchymaEnhancement less than surrounding renal parenchyma
 Calcifications rare unless there is therapyCalcifications rare unless there is therapy

89.  2:2: invasion of kidney by renal massinvasion of kidney by renal mass
 Does not involve renal vein / IVCDoes not involve renal vein / IVC
 33: perinephric rind of soft tissue around kidney without: perinephric rind of soft tissue around kidney without
a focal parenchymal lesion.a focal parenchymal lesion.
4:diffuse infiltrative involvement of kidney4:diffuse infiltrative involvement of kidney
 Less common.Less common.
 Predominant involvement of medulla with relativePredominant involvement of medulla with relative
sparing of cortical margins.sparing of cortical margins.
 Usually involves renal hilum may encase renal vesselsUsually involves renal hilum may encase renal vessels
resulting in decreased renal enhancement.resulting in decreased renal enhancement.

92.  MRI features similar to CTMRI features similar to CT
 Hypo to renal parencyma on T1 and slightly hyper onHypo to renal parencyma on T1 and slightly hyper on
T2T2
 Mild heterogenous enhancement less than renalMild heterogenous enhancement less than renal
parenchyma on T1 gadoparenchyma on T1 gado
 Primary renal lymphoma is a form of NHL arisngPrimary renal lymphoma is a form of NHL arisng
directly from renal parenchymadirectly from renal parenchyma
 Extremely rare as normal kidney is free of lymphaticExtremely rare as normal kidney is free of lymphatic
tissuetissue

95. metastasesmetastases
 Excluding lymphoma & leukemiaExcluding lymphoma & leukemia most commonmost common
primary sites: lung , colon, breast,melanoma, testicularprimary sites: lung , colon, breast,melanoma, testicular
& ovarian malignancy.& ovarian malignancy.
 Usually asyptamatic rarely hematuriaUsually asyptamatic rarely hematuria
 Ct very sensitiveCt very sensitive
 Multi focal renal masses, usually bilateralMulti focal renal masses, usually bilateral
 Hypodense 20-40 huHypodense 20-40 hu
 Do not demonstrate hyper enhancement 5-15 huDo not demonstrate hyper enhancement 5-15 hu
 Large mets may be from lung , colon or breastLarge mets may be from lung , colon or breast
 Colon mets disrupts renal cortical marginColon mets disrupts renal cortical margin

96.  Peri nephric space involvemnt by mets seen inPeri nephric space involvemnt by mets seen in
melanoma and lung metsmelanoma and lung mets
 Hemorrhagic mets: melanomaHemorrhagic mets: melanoma
 May also be seen in pheocromocytomaMay also be seen in pheocromocytoma
leiomyosarcoma.leiomyosarcoma.
Difference from RCC:Difference from RCC:
Usually bilateral, less necrosis, no renal vienUsually bilateral, less necrosis, no renal vien
involvemnt/ thrombosisinvolvemnt/ thrombosis

98. sarcomasarcoma
 Common in pts > 40yrsCommon in pts > 40yrs
 Hematuria, abd distension , pain wt lossHematuria, abd distension , pain wt loss
 Leomyosarcoma most commonLeomyosarcoma most common
 May be seen in perinephric spaceMay be seen in perinephric space
 Rx: surgical resection…poor prognosisRx: surgical resection…poor prognosis
 Ct: heterogenous lesions… fibrous component delayedCt: heterogenous lesions… fibrous component delayed
enhancement spindle cell component earlyenhancement spindle cell component early
enhancement.enhancement.
 MR: low on T1 and mixed on T2MR: low on T1 and mixed on T2

100.  Liposarcoma:Liposarcoma:
 Usually from capsuleUsually from capsule
 Present with mass , pain , wt loss without hematuriaPresent with mass , pain , wt loss without hematuria
 Ct: retroperitoneal mass with macroscopic fat.Ct: retroperitoneal mass with macroscopic fat.
 Tumour capsule may be present, may displace kidney.Tumour capsule may be present, may displace kidney.
 Hypovascular massHypovascular mass
 Parenchymal invasion not typical.Parenchymal invasion not typical.
 Unlike AML this lesion is relatively avascular andUnlike AML this lesion is relatively avascular and
without enlarged vessels.without enlarged vessels.

101. Wilms tumorWilms tumor
 Children 3-4 yrsChildren 3-4 yrs
 Pesents as palpable abd massPesents as palpable abd mass
 May be associated with WAGR (wilms,aniridia, guMay be associated with WAGR (wilms,aniridia, gu
abnormality and retardation)abnormality and retardation)
 Drash(wilms, congenital nephropathy,pseudoDrash(wilms, congenital nephropathy,pseudo
hermaproditism)hermaproditism)
 Ct: focal solid mass with appearance similar to rccCt: focal solid mass with appearance similar to rcc
 Enhances heterogenouslyEnhances heterogenously
 Cystic changes and necrosis may be seenCystic changes and necrosis may be seen
 Perinephric extension and adenopathy may be seenPerinephric extension and adenopathy may be seen
 Vascular invasion commonVascular invasion common
 Calcfnts are rareCalcfnts are rare

103. Wilms' tumor vs NeuroblastomaWilms' tumor vs Neuroblastoma
 Wilms'Wilms'
 <10% are calcified; more often<10% are calcified; more often
a curvilinear patterna curvilinear pattern
 Occasional local para-aorticOccasional local para-aortic
adenopathy (less common thanadenopathy (less common than
with neuroblastoma)with neuroblastoma)
 IVC invasion has high positiveIVC invasion has high positive
predictive valuepredictive value
 Mets to lungs commonMets to lungs common
 NeuroblastomaNeuroblastoma
 Often calcified; scatteredOften calcified; scattered
pattern throughout masspattern throughout mass
 Large regional adenopathyLarge regional adenopathy
 High predictive value:High predictive value:
encasement of great vessels,encasement of great vessels,
spinal canal invasion,spinal canal invasion,
paravertebral massparavertebral mass
 Moderate predictive value:Moderate predictive value:
extension across midline,extension across midline,
displacement of great vesselsdisplacement of great vessels
 Mets to liver, bone commonMets to liver, bone common
 Elevated urine catecholaminesElevated urine catecholamines

104.  Wilms vs NeuroblastomaWilms vs Neuroblastoma
 Vascular invasion common, does not encaseVascular invasion common, does not encase
aorta, calcfts rare, mets common to lungs inaorta, calcfts rare, mets common to lungs in
wilmswilms
 MR: mild hypo on T1 high T2MR: mild hypo on T1 high T2
 Heterogenous enhancementHeterogenous enhancement
 Vein and IVC well seen on MR than CTVein and IVC well seen on MR than CT