II. Epidemiology

  1. Incidental Renal Mass on Autopsy (over age 50): 50%
  2. Incidental Renal Mass on CT Scan (over age 50): 33%

III. Differential Diagnosis

  1. Renal Cyst (Simple, Complex or Multiple)
  2. Malignant Masses
    1. Renal Cell Carcinoma
    2. Lymphoma
    3. Sarcoma
    4. Metastatic cancer
  3. Benign Masses
    1. Renal adenoma
    2. Angiomyolipoma
    3. Oncocytoma
  4. Inflammatory Lesions
    1. Renal infection
    2. Renal infarction
    3. Renal Trauma (renal hematoma)

IV. Imaging: Management of Mass on Renal Ultrasound

  1. Efficacy
    1. Test Sensitivity: 79% of renal parenchymal masses
    2. Does not detect Renal Masses less than 5 mm diameter
  2. Simple Renal Cyst Criteria
    1. Spherical or ovoid shaped cysts
    2. No internal echoes
    3. Thin smooth cyst wall separated from renal parenchyma
    4. Posterior cyst wall enhancement
      1. Suggests water-filled cyst
  3. Management
    1. Simple cysts require no further evaluation
    2. Abdominal CT or MRI indicated for other masses

V. Imaging: Management of Mass on Renal CT

  1. Efficacy
    1. Test Sensitivity: 94% of renal parenchymal masses
    2. MRI better distinguishes benign Renal Masses
  2. Absolute Surgery Consultation Indications
    1. Symptomatic Renal Mass
    2. Solid Renal Mass
    3. Bosniak Class III-IV Cystic Mass (see below)

VI. Imaging: Incidental Renal Mass on Abdominal CT

  1. Cystic Mass
    1. See below for Bosniak classification
  2. Fat containing Renal Mass
    1. No calcifications: Angiomyolipoma
      1. Consider urology evaluation
      2. Consider genetic Consultation
    2. Calcifications
      1. Reassess and CT or MRI Abdomen with and without contrast in 12 months
  3. Renal lesion too small to characterize
    1. Enhancement similar to parenchyma
      1. Reassess and CT or MRI Abdomen with and without contrast in 12 months
    2. Non-enhancing
      1. Benign lesion requiring no further workup
  4. Solid Renal Mass
    1. Solid lesion >1 cm
      1. Refer to urology for renal neoplasm
    2. Solid lesion <1 cm
      1. CT or MRI Abdomen with and without contrast every year for 5 years
      2. Refer to urology if growth >3mm per year

VII. Imaging: Cystic Renal Mass Incidental on Abdominal CT (Bosniak Classification)

  1. Bosniak's Class I: Simple Renal Cyst
    1. Criteria
      1. See Renal Ultrasound Criteria above
      2. Hairline thin wall without septa (unilocular), calcification or solid component
      3. Round or oval shape
      4. Uniform water attenuation density within cyst (-10 to 20 HU)
      5. No contrast enhancement
    2. Management
      1. Typically benign, requiring no further workup
  2. Bosniak's Class II Benign, Minimally Complicated Renal Cyst
    1. Criteria
      1. May contain a few hairline thin septa
      2. No measurable enhancement (but may appear subjectively to enhance)
      3. Wall or septa may have fine calcification
      4. May appear as <3 cm, well marginated, hyperdense cyst (density above simple fluid)
    2. Management
      1. Typically benign, requiring no further workup
  3. Bosniak's Class IIF Usually Benign, Complicated Renal Cyst
    1. Criteria
      1. Multiple hairline thin septa
      2. Wall or septa may contain thick or nodular calcifications
      3. No measurable enhancement (but may appear subjectively to enhance)
      4. May appear as >3 cm, well marginated, hyperdense cyst (density above simple fluid)
    2. Management
      1. CT or MRI Abdomen with and without contrast every year for 5 years
      2. Refer to urology if growth >3mm per year
  4. Bosniak's Class III Indeterminate Cystic Renal Mass
    1. Criteria
      1. Thick irregular wall or septa with calcifications
      2. Measurable contrast enhancement
      3. Multilocular
    2. Management
      1. Urology Consultation
  5. Bosniak's Class IV Malignant Cystic Renal Mass (Cystic Renal Cell Carcinoma)
    1. Criteria
      1. Heterogeneous lesions with shaggy appearance
      2. Thickened cyst walls
      3. Contrast enhancing Nodules
    2. Management
      1. Urology Consultation

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Ontology: Kidney Neoplasm (C0022665)

Definition (NCI) A benign or malignant neoplasm affecting the kidney. Representative examples of benign renal neoplasms include fibroma, lipoma, oncocytoma, and juxtaglomerular cell tumor. Representative examples of malignant renal neoplasms include renal cell carcinoma, renal pelvis carcinoma, Wilms tumor, rhabdoid tumor, sarcoma, and lymphoma.
Definition (MSH) Tumors or cancers of the KIDNEY.
Definition (CSP) new abnormal tissue of the kidney that grows by excessive cellular division and proliferation more rapidly than normal and continues to grow after the stimuli that initiated the new growth cease.
Concepts Neoplastic Process (T191)
MSH D007680
SnomedCT 126880001
English Kidney Neoplasms, Neoplasm, Kidney, Neoplasms, Kidney, kidney neoplasm, KIDNEY NEOPL, RENAL NEOPL, NEOPL KIDNEY, neoplasm of kidney, neoplasm of kidney (diagnosis), Kidney Neoplasm, Neoplasia renal, Renal neoplasia, Renal neoplasm NOS, Renal neoplasms, Neoplasm, Renal, Neoplasms, Renal, Renal Neoplasms, Kidney Neoplasms [Disease/Finding], renal neoplasm, renal neoplasms, renal tumor, renal tumour, renal tumors, kidney tumors, renal tumours, kidney neoplasms, kidney tumour, kidney tumours, Renal neoplasm, Kidneys--Tumors, Tumor of kidney, Tumour of kidney, Renal tumor, Renal tumour, Neoplasm of kidney (disorder), Neoplasm of kidney, kidney tumor, Renal Neoplasm, Kidney Tumor, Neoplasm of Kidney, Neoplasm of the Kidney, Renal Tumors, Renal Tumor, Tumor of Kidney, Tumor of the Kidney
Italian Tumore renale, Tumori renali, Tumore renale NAS, Neoplasia renale, Neoplasia del rene, Neoplasie renali, Neoplasie del rene
Dutch neoplasma nier, nierneoplasie, nierneoplasma NAO, nierneoplasmata, nierneoplasma, Gezwel, nier-, Gezwellen, nier-, Niergezwel, Niergezwellen
French Néoplasie rénale, Tumeur rénale SAI, Tumeur rénale, Tumeurs du rein, Tumeurs rénales
German Neoplasie der Niere, Neubildung der Nieren NNB, Nierenneoplasie, Neubildung der Niere, Neubildungen der Niere, Nierentumoren, Tumoren, Nieren-
Portuguese Neoplasia renal NE, Neoplasias renais, Neoplasia renal, Neoplasias Renais
Spanish Tumor renal, Neoplasia renal NEOM, neoplasia del riñón (trastorno), neoplasia del riñón, Neoplasias renales, Neoplasia renal, Neoplasias Renales
Japanese 腎新生物NOS, ジンシンセイブツNOS, ジンゾウシンセイブツ, ジンシンセイブツ, 腎新生物, 腎臓新生物, 腎臓腫瘍, 腎腫瘍
Swedish Njurtumörer
Finnish Munuaiskasvaimet
Russian POCHEK NOVOOBRAZOVANIIA, ПОЧЕК НОВООБРАЗОВАНИЯ
Czech Neoplazie ledviny, Novotvar ledviny NOS, Novotvar ledviny, Renální neoplazie, Novotvary ledvin, renální nádory, nádory ledvin, ledviny - nádory, renální nádor
Croatian BUBREŽNI TUMORI
Polish Nowotwory nerek
Hungarian Vesedaganat, Renális neoplasmák, Renalis neoplasia, Renalis neoplasia k.m.n.
Norwegian Svulster i nyre, Neoplasmer i nyre, Tumorer i nyre, Nyresvulster

Ontology: Renal mass (C0262613)

Concepts Finding (T033)
SnomedCT 309088003
Italian Massa renale, Massa renale NAS
Dutch niergezwel NAO, massa; nier, nier; massa, niergezwel
French Masse rénale SAI, Masse rénale
German Raumforderung Niere NNB, Raumforderung Niere
Portuguese Massa renal NE, Massa renal
Spanish Masa renal NEOM, masa renal (hallazgo), masa renal, Masa renal
Japanese 腎腫瘤, 腎腫瘤NOS, ジンシュリュウ, ジンシュリュウNOS
Czech Renální rezistence NOS, Renální rezistence
English kidney masses, kidney mass, kidneys mass, mass kidney, mass renal, masses renal, renal mass, Renal mass NOS, Kidney mass, Renal mass, Renal mass (finding), kidney; mass, mass; kidney, Kidney Mass, Renal Mass
Hungarian vese térfoglaló folyamata, vese térfoglaló folyamata k.m.n.

Ontology: lesion; kidney (C1402288)

Concepts Disease or Syndrome (T047)
English kidney; lesion, lesion; kidney
Dutch lesie; nier, nier; lesie