Renal Mass

See Also

Renal Cell Carcinoma

Epidemiology

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

Differential Diagnosis

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

Imaging
Management of Mass on Renal Ultrasound

Efficacy
1. Test Sensitivity: 79% of renal parenchymal masses
2. Does not detect Renal Masses less than 5 mm diameter
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
Management
1. Simple cysts require no further evaluation
2. Abdominal CT or MRI indicated for other masses

Imaging
Management of Mass on Renal CT

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

Imaging
Incidental Renal Mass on Abdominal CT

Cystic Mass
1. See below for Bosniak classification
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
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
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

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

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
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
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
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
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

References