Imaging Pearls ❯ Kidney ❯ Benign Renal Masses
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- Polycystic Kidney Disease: Facts
- Autosomal dominant with nearly a 100% penetrance
- Defect on short arm of chromosome 16
- Cysts also occur in liver (up to 80% of cases), and pancreas (up to 9% of cases)
- Patients may also have an increased incidence of cerebral aneurysms - Polycystic Kidney Disease: Clinical Presentation
- Hypertension
- Azotemia
- Hematuria
- Proteinuria
- Abdominal or back pain - Polycystic Kidney Disease: Differential Dx (in theory)
- Multiple simple cysts
- Von Hippel-Lindau disease
- Acquired uremic cystic disease
- Infantile PCKD
- Polycystic Kidney Disease: Facts
- Autosomal dominant with nearly a 100% penetrance
- Defect on short arm of chromosome 16
- Cysts also occur in liver (up to 80% of cases), and pancreas (up to 9% of cases)
- Patients may also have an increased incidence of cerebral aneurysms - Polycystic Kidney Disease: Clinical Presentation
- Hypertension
- Azotemia
- Hematuria
- Proteinuria
- Abdominal or back pain - Polycystic Kidney Disease: Differential Dx (in theory)
- Multiple simple cysts
- Von Hippel-Lindau disease
- Acquired uremic cystic disease
- Infantile PCKD
- “Homogeneous simple renal cysts can have mean attenuation values of up to 30 HU, as determined by contrast-enhanced CT, whereas homogeneous RCCs have mean attenuation values as low as 42 HU, with no overlap occurring between the two groups. These data suggest that further evaluation of a homogeneous renal mass with a mean attenua- tion value of 30 HU or less on a contrast-enhanced CT scan likely is unwarranted.”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804 - “A total of 116 heterogeneous renal cell carcinomas (RCCs) (99 clear cell, four papillary, four oncocytic, seven chromophobe, and two unclassi ed RCCs), 13 homogeneous RCCs (10 papillary, two oncocytic, and one chromophobe RCC), and 24 cysts (all of which were homogeneous) were evaluated. All homogeneous RCCs had mean attenuation values of more than 42 HU, whereas renal cysts had mean attenuation values of up to 30 HU (p < 0.001). Two readers qualitatively and identically categorized all RCCs as homogeneous or heterogeneous (κ = 1.0; p < 0.001).”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804 - “In most cases, simple renal cysts can be easily diagnosed and dismissed as benign. In general, simple renal cysts have simple uid attenuation (0– 20 HU), are homogeneous, have a hairline thin smooth wall or an imperceptible wall, and do not enhance after administration of a contrast agent.”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804 - “A study of more than 11,000 simple renal cysts evaluated with unenhanced CT sup- ported the use of unenhanced CT as long as the mass is homogeneous in attenuation, has an attenuation value between –10 and 20 HU,
has a hairline thin wall, and does not contain septa, nodules, or calcification.”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804 - “The present study shows that homoge- neous simple renal cysts can have a mean attenuation value of up to 30 HU on contrast- enhanced CT, whereas homogeneous RCCs have a mean attenuation value as low as 42 HU, and there was no overlap noted between these two groups.”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804 - “In conclusion, the present study shows that homogeneous simple renal cysts can have a mean attenuation value of up to 30 HU on contrast-enhanced CT, whereas homogeneous RCCs can have a mean attenuation value as low as 42 HU, with no overlap occurring between these two groups. Simple renal cysts may have a mean attenuation value of greater than 20 HU on contrast-enhanced CT and are currently considered to be incompletely characterized, and the data in the present study suggest that if a homogeneous renal mass has a mean attenuation value of 30 HU or less, further evaluation likely is not warranted.”
Differentiating Renal Neoplasms From Simple Cysts on Contrast- Enhanced CT on the Basis of Attenuation and Homogeneity Agochukwu N et al AJR 2017; 208:801–804
- “Renal Angiomyolipoma (AML) is the most common benign tumor of the kidney with a prevalence of about 0.3 to 3% worldwide, with a significant higher prevalence in females than males. It is a neoplasm composed of dysmorphic tortuous vascular tissue, smooth muscle and fat. AML may be associated with Tuberous sclerosis complex (TSC) or pulmonary lymphangioleiomyomatosis (LAM) or may occur sporadically. There is no histologic difference between sporadic AML and TSC-associated AML. The vascular tissues are prone to aneurysm formation and rupture. Most cases of AML are incidentally found on imaging. Approximately 10% of patients diagnosed with renal AML have tuberous sclerosis. When symptomatic, AML typically presents as palpable flank mass, hematuria and flank pain.”
Review of renal artery embolization for treatment of renal angiomyolipoma Melvin Omodon et al. Clinical Nephrology and Urology Science 2016 3: 1 (2 February 2016) - “Approximately 17 to 20 percent of patients presenting with spontaneous perinephric hemorrhage have AML . 90% of AML cases are unilateral, solitary lesions usually seen in the sporadic AML. Multiple bilateral AML is seen in about 10% of the cases which are usually associated with TSC or LAM. TSC-associated AML is associated with loss of heterozygosity mutations of both TSC1 and TSC2 genes compared to mutations of the TSC2 gene seen in the sporadic AML . It is hypothesized that dysregulated mammalian target or rapamycin (mTOR) signaling increases tumor cell growth, proliferation, and metabolism thus promoting progression of TSC lesions.”
Review of renal artery embolization for treatment of renal angiomyolipoma Melvin Omodon et al. Clinical Nephrology and Urology Science 2016 3: 1 (2 February 2016) - “Angiomyolipomas associated with TSC grows more rapidly, bleeds more frequently, and more likely involve bilateral kidneys compared to sporadic form. TSC-associated AML typically present in younger patients, within the third decade of life compared to the sporadic form seen at about the fifth decade of life.”
Review of renal artery embolization for treatment of renal angiomyolipoma Melvin Omodon et al. Clinical Nephrology and Urology Science 2016 3: 1 (2 February 2016) - “An Renal AML greater than 4 cm in diameter have a significant risk of hemorrhage. Size greater than 4 cm approaches 100% sensitivity and 40% specificity to predict rupture. Threshold size for treatment of TSC-associated AML is 3cm, and for sporadic form is 4cm. Aneurysms greater than 5mm in size are more predictive for rupture than tumor size. Other factors associated with increased risk of bleeding include pregnancy and use of estrogen containing contraceptive medication.”
Review of renal artery embolization for treatment of renal angiomyolipoma Melvin Omodon et al. Clinical Nephrology and Urology Science 2016 3: 1 (2 February 2016) - “RAE is the treatment of choice for acute hemorrhage from angiomyolipoma, and also first-line prophylactic treatmentfor angiomyolipomas at risk of bleeding. Up to 5% of initial embolization may require a repeat embolization, and in a few cases post RAE nephrectomy may be necessary. Post embolization syndrome comprised of abdominal pain, cramping, fever, nausea and vomiting, is a relatively common complication especially in large tumors. Treatment is with symptom relief.”
Review of renal artery embolization for treatment of renal angiomyolipoma Melvin Omodon et al. Clinical Nephrology and Urology Science 2016 3: 1 (2 February 2016)
- “Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior.”
Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management.
Jinzaki M et al.
Abdom Imaging. 2014 Jun;39(3):588-604. - “The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component.”
Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management.
Jinzaki M et al.
Abdom Imaging. 2014 Jun;39(3):588-604. - “Angiomyolipoma is a solid tumor that is encountered commonly in the kidney in clinical practice . Angiomyolipoma is typically a solid ‘‘triphasic’’ tumor composed of varying amounts of three elements: dysmorphic blood vessels, smooth muscle components, and mature adipose tissue. Because most angiomyolipomas contain substantial amounts of adipose tissue, it is usually diagnosed using CT or MRI by identifying imaging features of fat cells in the mass.”
Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management.
Jinzaki M et al.
Abdom Imaging. 2014 Jun;39(3):588-604. - “While 80% of angiomyolipomas are sporadic and most of them inconsequential, approxi- mately 20% are associated with tuberous sclerosis complex (TSC) . Angiomyolipomas may be found also in patients with lymphangioleiomyomatosis (LAM) .”
Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management.
Jinzaki M et al.
Abdom Imaging. 2014 Jun;39(3):588-604. - “The image-based detection of fat often begins with CT. On unenhanced CT, the presence of regions of interest (ROI)-containing attenuations less than -10 HU allows the confident identification of fat. The CT appearance of a classic angiomyolipoma varies due to variable amounts of fat, blood vessels, and smooth muscle components of the neoplasm.”
Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management.
Jinzaki M et al.
Abdom Imaging. 2014 Jun;39(3):588-604. - “Excellent classification results (error of 0.00%-9.30%) were obtained with nonlinear discriminant analysis for all the three groups, no matter which phase was used. On comparison of the three scanning phases, we observed a trend toward better lesion classification with PCP for minimal fat AML versus ccRCC, CMP, and NP images for ccRCC versus pRCC and found similar discriminative power for minimal fat AML versus pRCC.”
Angiomyolipoma with Minimal Fat: Differentiation From Clear Cell Renal Cell Carcinoma and Papillary
Renal Cell Carcinoma by Texture Analysis on CT Images.
Yan L et al.
Acad Radiol. 2015 May 29. pii: S1076-6332(15)00188-9
- Extramedullary Hematopoesis: Facts
- Compensatory mechanisms to form blood cells within organs or tissues outside the bone marrow
- Usually occurs in spleen, liver, lymph nodes, paraspinal soft tissues
- Can mimic adenopathy or a primary tumor especially a neurogenic tumor
- The masses often are vascular on contrast enhanced CT - Perinephric Masses on CT: Differential Diagnosis
- Lymphoma
- Metastases (especially melanoma)
- Myeloma
- Urinomas
- Hemmorrhage
- Infection
- Extramedullary hematopoiesis
- Retroperitoneal fibrosis
- Erdheim Chester disease - Benign Lesions of the Upper Urinary Tract: Mimics
- Malacoplakia
- Urolithiasis
- Infection
- TB
- Fibroepithelial polyps
- Sloughed papilla
- Hematoma
- Extramedullary Hematopoesis: Facts
- Compensatory mechanisms to form blood cells within organs or tissues outside the bone marrow
- Usually occurs in spleen, liver, lymph nodes, paraspinal soft tissues
- Can mimic adenopathy or a primary tumor especially a neurogenic tumor
- The masses often are vascular on contrast enhanced CT - Perinephric Masses on CT: Differential Diagnosis
- Lymphoma
- Metastases (especially melanoma)
- Myeloma
- Urinomas
- Hemmorrhage
- Infection
- Extramedullary hematopoiesis
- Retroperitoneal fibrosis
- Erdheim Chester disease - Benign Lesions of the Upper Urinary Tract: Mimics
- Malacoplakia
- Urolithiasis
- Infection
- TB
- Fibroepithelial polyps
- Sloughed papilla
- Hematoma - Mesenchymal Renal Neoplasms: Benign
- Angiomyolipoma
- Leiomyoma
- Hemangioma
- Lymphangioma
- Juxtaglomerular cell tumor
- Medullary fibroma
- Solitry fibrous tumor
- Schwannoma - Mesenchymal Tumors
- Angiomyolipoma
- Leiomyoma
- Hemangioma
- Lymphangioma
- Reninoma
- Fibroma
- Schwannoma
- Mixed Epithelial and Mesenchymal Tumors
- Cystic nephroma
- Mixed epithelial and stromal tumor
- A Pattern-Based Imaging Approach to Benign Renal Tumors
- Soft tissue mass
- Fatty mass
- Cystic mass
- Cortical mass
- Medullary mass
Benign Renal Neoplasms in Adults:
Cross-Sectional Imaging Findings
Prasad SR et al. AJR 2008; 190:158-164
- Mixed Epithelial and Mesenchymal Neoplasms: Facts
- Consists of mixed epithelial and stromal tumors (MEST) and cystic nephromas
- MEST was previously called
–Leiomyomatous renal hamartoma
–Multilocular cyst with ovarian stroma
–Cystic hamartoma of the renal pelvis
–Adult mesoblastic nephroma
- Mixed Epithelial and Stromal Tumors (MEST)
- Usually in perimenopausal woman by 6:1 ratio
- Most patients are on estrogen therapy
- 25% of cases are detected incidentally
- CT findings are expansile, complex, cystic and solid masses with heterogeneous and delayed enhancement
- Cystic Nephroma: Facts
- Benign tumor in middle aged females
- CT findings are a well demarcated solitary multilocular cystic lesions with thin septations. These tumors may protrude into the renal pelvis and cause hemorrhage or urinary obstruction
- Proportion of Solid Renal Masses That are Benign:
Size (cm) Proportion All sizes 12.8% 0 to < 1 46.3% 1 to < 2 22.4% 2 to < 3 22.0% 3 to < 4 19.9% 4 to < 5 9.9% 5 to < 6 13.0% 6 to < 7 4.5% > 7 6.3%
- Fact: small renal masses removed at surgery are often benign
Solid Renal Tumors: An Analysis of Pathological Features Related to Tumor Size
Frank I et al.
J Urol 2003; 170:2217-2220
- Extramedullary Hematopoiesis: Facts
- Hematopoietic tissue develops outside primary medullary sites
- Associated with hemolytic anemias, henoglobinopathies, myelofibrosis, leukemia, lymphoma
- Most common sites are liver, spleen and parespinal regions of the thorax
- Benign Renal Neoplasms in Adults: WHO Classification
- Renal cell tumors (Oncocytoma)
- Metanephric neoplasms
- Mesenchymal neoplasms
- Mixed epithelial and mesenchymal neoplams
- Renal Cell Tumors
- Oncocytoma - Papillary adenoma
- Metanephric Tumors - Metanephric adenoma - Metanephric adenofibroma - Metanephric stromal tumor
- Mesenchymal Tumors
- Angiomyolipoma - Leiomyoma - Hemangioma - Lymphangioma - Reninoma - Fibroma - Schwannoma
- Mixed Epithelial and Mesenchymal tumors
- Cystic nephroma
- Mixed epithelial and stromal tumor
- "The 2004 World Health Organization (WHO) classification schemata categorizes benign renal neoplasms on the basis of histiogenesis (cell of origin) and histopathology."
Benign Renal Neoplasms in Adults: Cross-Sectional Imaging Findings
Prasad S et al.
AJR 2008; 190:158-164
- "The 2004 World Health Organization (WHO) classification schemata categorizes benign renal neoplasms on the basis of histiogenesis (cell of origin) and histopathology. Renal neoplasms are thus classified into renal cell, metanephric, mesenchymal, and mixed epithelial and mesenchymal tumors."
Benign Renal Neoplasms in Adults: Cross-Sectional Imaging Findings
Prasad S et al.
AJR 2008; 190:158-164
- Oncocytoma: facts
- Benign renal cell neoplasm
- Patient usually in 6th or 7th decade of life
- Male more commonly involved
- Central scar seen in 1/3 of cases on CT
- May be indistinguishable from renal cell carcinoma
- Oncocytoma: facts
- Up to 40% of patients over age 70 will have these tumors at autopsy
- Commonly found in patients with acquired cystic renal disease and patient on long term hemodialysis
- Usually measure 5 mm or less
- Metanephric Adenoma: facts
- Benign tumor
- 2:1 female predominance
- Average age is 5th or 6th decade
- Polycythemia occurs in 10% of patients
- Juxtaglomerular cell Neoplasm (Reninoma): facts
- Benign tumor of myoendocrine origin
- Peak age is2nd or 3rd decade of life
- 2:1 female predominance
- Clinical triad of poorly controlled hypertension, hypokalemia and high plasma renin level
- Usually under 3 cm vascular tumor
- Juxtaglomerular cell Neoplasm (Reninoma): facts
- Occur in perimenopausal woman often receiving estrogen
- 6:1 female predominance
- On CT usually large cystic and solid tumors which heterogeneous and delayed enhancement
- Juxtaglomerular cell Neoplasm (Reninoma): facts
"In an anthropomorphic phantom model, dual energy CT can accurately discriminate uric acid stones from other stone types."
Noninvasive Differentiation of Uric Acid versus Non-uric Acid Kidney Stones Using Dual Energy CT
Primak AN et al
Acad Radiol 2007; 14:1441-1447
- Juxtaglomerular cell Neoplasm (Reninoma): facts
"An mA as low as 70 (35 mAs) is acceptable for evaluation of nephrolithiasis. However, the evaluation of ureterolithiasis is comprimised with an mA of 70."
Conventional and Reduced radiation Dose of 16-MDCT for Detection of Nephrolithiasis and Ureterolthiasis
Paulson EK et al.
AJR 2008; 190;151-157