1. Robert D. Thomas MD Pediatric Radiology
Renal Masses
Robert D. Thomas MD
Pediatric Radiology

2. Renal Masses Balls Beans Cyst Hematoma Abscess Tumor Dromedary hump
Duplication/anomaly
Compensatory hypertrophy
Hydronephrosis
Pyelonephritis/edema
Hematoma
PCKD
Tumor
Vascular occlusion/trauma

3. Renal Masses by Age Newborn Childhood Hydronephrosis Cysts
MCDK
AR-PCKD
Anomalies
Tumors
Mesoblastic nephroma
Nephroblastomatosis
Childhood
Cysts
Hydronephrosis, MCDK
Anomalies
Hematoma
Tumors
Wilms
Lymphoma
Angiomyolipomas

4. Hydronephrosis (Bean)
Calyceal/Pelvic obstruction
Congenital (intrinsic/extrinsic) TB
Tumor
Ureter
Physiologic (full bladder)
Congenital (1 megaureter, ectopic ureter, retrocaval)
Inflammatory (TB, Crohn, PID, etc)
Intraluminal (stone, clot, tumor, stricture)

5. Congenital UPJ obstruction
#1 cause of renal mass in newborn
Associations
Ipsilateral reflux
Lower moiety of duplication
Most common cause of obstruction with horseshoe kidney
Causes
Stricture, disordered peristalsis, ischemia, redundant urothelium, crossing vessel, etc.

6. Congenital UPJ obstruction
Imaging:
Mass in plain films
US – dilated pelvo-calyceal system (communicating cysts): dilatation-fluid equal to cortical thickness
NM – obstructive pattern w/o lasix response
Pitfalls
US may underestimate hydro due to oliguria/dehydration in newborn
MCDK may look like UPJ if only a couple cysts present

11. Congenital UPJ obstruction
Work-up
VCUG: co-existant ipsilateral reflux*, urethral obstruction, contralateral reflux
Scintigraphy: site of obstruction & renal function
*obstruction to reflux at UPJ, dilution of contrast in dilated renal pelvis, delay in drainage from renal pelvis

15. Multicystic Dysplastic Kidney Bean or Ball
Not a true “cystic disease”
etiology is severe embryonic obstruction during metanephric stage of development
So…it’s an obstruction
Hallmark: non-function of the kidney
Bilaterality not compatible with life due to severe pulmonary hypoplasia

16. Multicystic Dysplastic Kidney
2nd most common renal mass in newborn
Types
Pelvoinfundibular – atresias at ureter, pelvis, infundibulae
Most common, grape-like collection of cysts and dysplastic glomeruli, atrophied tubules
Hydronephrotic-atresia of proximal ureter alone
Uncommon (5%)

17. Multicystic Dysplastic Kidney
Imaging
US - Isolated cysts without a definable pelvis and without normal renal tissue
IVP – lack of function
NM – absence of perfusion & lack of function (may have minimal activity 24-48hrs)

20. Multicystic Dysplastic Kidney
Work-up
US: frequent contralateral UPJ, reflux,
VCUG: opposite reflux/obstruction
MAG3, DTPA renogram
Management
Usually observation (natural history of involution)
Nephrectomy for GI obstruction/respiratory compromise, hypertension
?malignancy probably not increased over baseline

21. Solid Renal Masses Beans and Balls!
Hematoma
Abscess
Tumor

23. R/P mass in Neonate Renal Adrenal Hydronephrosis
Multicystic dysplastic kidney
Solid
Wilms tumor?
Perinephric hematoma?
Mesoblastic nephroma?
Lymphoma?
Adrenal
Hemorrhage
neuroblastoma

27. Mesoblastic Nephroma (Fetal renal hamartoma)
Most common neonatal renal neoplasm
Present as an asymptomatic mass
Not Wilms tumor
Characteristics
Benign appearing spindle cells with dysplastic nephrons
Large (8-30cm), arise in medulla
Blends with normal parenchyma
May penetrate capsule and invade locally
Rare hypercellular forms may metastasize

28. Mesoblastic Nephroma (Fetal renal hamartoma)
Imaging
Non-calcified abdominal mass
Look like uterine leiomyoma by US
CT vascular and entrapped collecting system excretes contrast

30. Mesoblastic Nephroma (Fetal renal hamartoma)
Management
Nephrectomy
No chemo or radiation (usually no mets)
Cellular form
Age >3months at surgery are more likely to need chemo/radiation

31. Childhood Renal Tumors
Wilms tumor & nephroblastomatosis
Renal lymphoma/leukemia
Renal cell carcinoma
Multilocular cystic nephroma
Clear cell sarcoma
Rhabdoid tumor
Angiomyolipoma (and tuberous sclerosis)

33. Wilms Tumor Most common solid abdominal mass in childhood
Most common renal malignancy in child
8% of all childhood cancer

34. Wilms Tumor Demographics Presentation Male=female 1% familial
7.8 per 1,000,000 children
Peaks between 2.5 to 3 years
80% occur between 1-5 years
Presentation
Asymptomatic mass most common
Other: pain, hematuria, hypertension, fever

35. Wilms Tumor Associated conditions
8% have overgrowth disorders, genital anomalies, aniridia
Drash, Beckwith-Wiedemann, Soto, NF, KTW, Bloom, WAGR, 45X, etc
5% bilateral & higher incidence of above
These children’s siblings have a 30% chance of development of Wilms
Nephroblastomatosis (Wilms precursor)

36. Wilms Tumor Nephroblastoma (Wilms “in situ”)
Rests of metanephric blastema persisting after weeks gestational age
Present in most cases of bilateral Wilms, 15% unilateral disease
Intralobular NR
Younger age
Drash & sporadic aniridia
Metachronous Wilms
Perilobular NR
BWS, Tr18, hemihypertrophy
Synchronous Wilms

37. Wilms Tumor Nephroblastomatosis ImagingAppearance
Nodules
Subcapsular hypodense plaques
US – iso, hypo, hyperechoic (relatively insensitive)
CT w contrast better for surveillance
MRI ? Able to distinguish Wilms from nephroblastomatosis

40. NR versus Wilms at MRI NR Wilms Plaque-like Ovoid Lenticular
Homogeneous on all sequences
Hypotense post gad
Wilms
Round/spherical
Heterogeneous pre gad
Heterogeneous post contrast

43. Nephroblastomatosis Treatment
Confluent disease treated with chemotherapy

45. Wilms Tumor Pathology Solid, necrosis, hemorrhage, 15% calcifications
Capsule usually intact
Invades nodes, veins, rarely urothelium
Decreasing 10’s
10% renal vein invasion
10% IVC extension
10% right atrial extension

46. Wilms Tumor Pathology 5% bilateral 7% unilateral and multicentric
Metachronous cases may occur up to 10 years later
10% unfavorable histology

47. Wilms Tumor Pathology Lung mets up to 20% at diagnosis
Liver mets 10% of patients
Bone mets rare (lytic)
Bilateral tumors may have different grades of histology (favorable vs unfavorable)

48. Wilms Tumor Staging I – limited to kidney, completely resected
II- outside kidney, completely resected
III – confined to abdomen
IV – hematogenous mets
V – bilateral initial/during treatment

50. Wilms Tumor - Radiology
Nitwits (NWTS) don’t agree on optimal imaging – nonsense like IVP’s persist
IVP – distortion of collecting system, non-function (vascular compression)
US –
CDS excellent for venous tumor thrombi in IVC
Echotexture similar to liver
Sharply marginated

54. Wilms Tumor - RadiologyCT
15% contain calcifications
Round, hetergeneous, low density
Displaces vessels, does NOT encase (DDX from neuroblastoma)
Best for opposite kidney evaluation, nodes, lungs

56. Wilms Tumor-Radiology
MRI
Becoming preferred over CT
Prolonged T1 and T2, heterogeneous post gad
Excellent for NR of 4 mm size
Angio
Plays a role for partial nephrectomy

58. Wilms Tumor - Surveillance
Patients with syndromes associated with Wilms
US easiest, MRI may be best
Arbitrary 3-6 month scans
Continue until about 10 years old (<1% incidence after 10)

59. Wilms Tumor - Treatment
Overall survival now 90%
>90% 2 yrs with favorable histology, surgery, chemo and radiation
High mortality with unfavorable histology

61. Renal Lymphoma Usually late in NHL
Nodules, masses, diffuse infiltration
Unilateral/bilateral
US – hypoechoic
CT – hypodense
Leukemia usually diffuse/bilateral

65. Multilocular Cystic Nephroma
Indistinguishable from cystic partially differentiated nephroblastoma/cystic Wilms
Young boys and adult women
Anechoic cysts with regular septa
Rx - nephrectomy

67. Clear Cell Sarcoma Identical age group to Wilms Very aggressive
Not distinguishable from Wilms by imaging
Bone mets common

69. Other lesions to ponder
“Simple” cyst
Were considered rare prior to ultrasound
But, the differential diagnosis is:
Prior trauma or infection
Obstructed upper pole moiety of duplication
Early presentation of familial cystic disease

75. Other lesions to ponder
Duplication
Hematoma/renal trauma
Pyelonephritis
Focal bacterial
Xanthogranulomatous
Autosomal recessive polycystic kidney dz
Infantile form