Renal Masses

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Renal Masses

• Robert D. Thomas MD
• Pediatric Radiology

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Renal Masses

• Balls
• Cyst
• Hematoma
• Abscess
• Tumor
• Dromedary hump

• Beans
• Duplication/anomaly
• Compensatory hypertrophy
• Hydronephrosis
• Pyelonephritis/edema
• Hematoma
• PCKD
• Tumor
• Vascular occlusion/trauma

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Renal Masses by Age

• Newborn
• Hydronephrosis
• MCDK
• AR-PCKD
• Anomalies
• Tumors
• Mesoblastic nephroma
• Nephroblastomatosis

• Childhood
• Cysts
• Hydronephrosis, MCDK
• Anomalies
• Hematoma
• Tumors
• Wilms
• Lymphoma
• Angiomyolipomas

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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)

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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.

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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

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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

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Multicystic Dysplastic KidneyBean or Ball

• Not a true cystic disease
• etiology is severe embryonic obstruction during
  metanephric stage of development
• Soits an obstruction
• Hallmark non-function of the kidney
• Bilaterality not compatible with life due to
  severe pulmonary hypoplasia

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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)

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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)

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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

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Solid Renal MassesBeans and Balls!

• Hematoma
• Abscess
• Tumor

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R/P mass in Neonate

• Renal
• Hydronephrosis
• Multicystic dysplastic kidney
• Solid
• Wilms tumor?
• Perinephric hematoma?
• Mesoblastic nephroma?
• Lymphoma?
• Adrenal
• Hemorrhage
• neuroblastoma

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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

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Mesoblastic Nephroma(Fetal renal hamartoma)

• Imaging
• Non-calcified abdominal mass
• Look like uterine leiomyoma by US
• CT vascular and entrapped collecting system
  excretes contrast

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Mesoblastic Nephroma(Fetal renal hamartoma)

• Management
• Nephrectomy
• No chemo or radiation (usually no mets)
• Cellular form
• Age gt3months at surgery are more likely to need
  chemo/radiation

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Childhood Renal Tumors

• Wilms tumor nephroblastomatosis
• Renal lymphoma/leukemia
• Renal cell carcinoma
• Multilocular cystic nephroma
• Clear cell sarcoma
• Rhabdoid tumor
• Angiomyolipoma (and tuberous sclerosis)

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Wilms Tumor

• Most common solid abdominal mass in childhood
• Most common renal malignancy in child
• 8 of all childhood cancer

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Wilms Tumor

• Demographics
• Malefemale
• 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

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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 childrens siblings have a 30 chance of
  development of Wilms
• Nephroblastomatosis (Wilms precursor)

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Wilms Tumor

• Nephroblastoma (Wilms in situ)
• Rests of metanephric blastema persisting after
  34-36 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

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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

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NR versus Wilms at MRI

• NR
• Plaque-like
• Ovoid
• Lenticular
• Homogeneous on all sequences
• Hypotense post gad

• Wilms
• Round/spherical
• Heterogeneous pre gad
• Heterogeneous post contrast

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Nephroblastomatosis

• Treatment
• Confluent disease treated with chemotherapy

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Wilms Tumor

• Pathology
• Solid, necrosis, hemorrhage, 15 calcifications
• Capsule usually intact
• Invades nodes, veins, rarely urothelium
• Decreasing 10s
• 10 renal vein invasion
• 10 IVC extension
• 10 right atrial extension

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Wilms Tumor

• Pathology
• 5 bilateral
• 7 unilateral and multicentric
• Metachronous cases may occur up to 10 years later
• 10 unfavorable histology

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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)

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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

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Wilms Tumor - Radiology

• Nitwits (NWTS) dont agree on optimal imaging
  nonsense like IVPs 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

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Wilms Tumor - Radiology

• CT
• 15 contain calcifications
• Round, hetergeneous, low density
• Displaces vessels, does NOT encase (DDX from
  neuroblastoma)
• Best for opposite kidney evaluation, nodes, lungs

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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

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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 (lt1 incidence
  after 10)

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Wilms Tumor - Treatment

• Overall survival now 90
• gt90 survival _at_ 2 yrs with favorable histology,
  surgery, chemo and radiation
• High mortality with unfavorable histology

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Renal Lymphoma

• Usually late in NHL
• Nodules, masses, diffuse infiltration
• Unilateral/bilateral
• US hypoechoic
• CT hypodense
• Leukemia usually diffuse/bilateral

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Multilocular Cystic Nephroma

• Indistinguishable from cystic partially
  differentiated nephroblastoma/cystic Wilms
• Young boys and adult women
• Anechoic cysts with regular septa
• Rx - nephrectomy

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Clear Cell Sarcoma

• Identical age group to Wilms
• Very aggressive
• Not distinguishable from Wilms by imaging
• Bone mets common

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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

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Other lesions to ponder

• Duplication
• Hematoma/renal trauma
• Pyelonephritis
• Focal bacterial
• Xanthogranulomatous
• Autosomal recessive polycystic kidney dz
• Infantile form

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