What are the other Names for this Condition? (Also known as/Synonyms)

• Renal Oncocytomatosis
• Renal Oncocytosis

What is Oncocytosis of Kidney? (Definition/Background Information)

• Oncocytosis of Kidney is a rare, benign condition of the kidney that is characterized by the presence of many oncocytic lesions/proliferations without necrosis in the kidney. It is generally diagnosed in adults
• The tumor is known to be associated with certain genetic disorders, such as Birt-Hogg-Dubé syndrome, certain renal cell carcinoma types, and chronic kidney disease. But, the cause of formation of Oncocytosis of Kidney is typically unknown
• The signs and symptoms of Oncocytosis of Kidney depend upon the size of the dominant tumors and may include abdominal pain and blood in urine. Some tumors can grow to large sizes leading to symptoms due to mass effect of the tumor
• In many cases, the tumors are found incidentally while examining the individual for other medical conditions. The healthcare provider may recommend treatment options (such as wait and watch approach or surgery) based on the assessment of the condition. Treatment of the underlying condition/kidney cancer may be performed (if necessary)
• The prognosis of Oncocytosis of Kidney is excellent with adequate treatment, since it is a benign tumor. However, the prognosis may depend on the presence of any underlying condition(s)

Who gets Oncocytosis of Kidney? (Age and Sex Distribution)

• Oncocytosis of Kidney is usually observed in adults
• Both males and females are affected
• No specific ethnic or racial preference has been recorded

What are the Risk Factors for Oncocytosis of Kidney? (Predisposing Factors)

The following risk factors have been identified for Oncocytosis of Kidney:

• Chronic kidney disease and end-stage kidney disease (ESKD)
• Renal Oncocytosis can also be associated with renal cell carcinoma (RCC, a form of kidney cancer), such as chromophobe RCC and papillary RCC, even though it is benign
• Birt-Hogg-Dubé syndrome (BHD syndrome): It is a hereditary disorder that is characterized by numerous tiny follicles on the skin. This rare condition also affects the kidneys and lungs

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Oncocytosis of Kidney? (Etiology)

The cause of Oncocytosis of Kidney formation is mostly unknown.

• The tumor is sometimes seen against a background of certain genetic syndromes, kidney cancer, and severe illnesses affecting kidney function
• However, Renal Oncocytosis can also occur in a sporadic manner, without the presence of an underlying renal condition/disease

What are the Signs and Symptoms of Oncocytosis of Kidney?

The signs and symptoms of Oncocytosis of Kidney vary from one individual to another. In general, small tumors are asymptomatic and large tumors can cause signs and symptoms. The kidney symptoms may be caused due to mass effect (presence of bulky tumors).

The signs and symptoms of Renal Oncocytosis may include the following:

• Multiple nodules are seen with one dominant nodule/tumor, which is usually an oncocytoma 
• The size of the dominant nodule may vary from 2-10 cm
• An oncocytoma is typically a solid, well-defined, and demarcated tumor
• In most cases, only a single kidney is involved. Although, in as many as 40% of the cases, the condition may be bilateral (involving both kidneys)
• Renal Oncocytosis may be present as an abdominal mass
• Tumors associated with genetic disorders may affect both kidneys (and are known to be multiple in numbers)
• It may be associated with urinary tract infections, blood in urine, increased blood pressure, and flank pain
• In general, large tumors can severely affect the functioning of the kidney that is involved. Tumors growing to larger sizes can cause compression of adjoining organs and structures, which can result in abdominal pain

Additionally, the signs and symptoms of any associated condition (such as kidney disease) may be observed.

How is Oncocytosis of Kidney Diagnosed?

The diagnosis of Oncocytosis of Kidney may involve the following tests and procedures:

• Complete physical exam with evaluation of medical history
• Urine analysis to check for the presence of blood cells
• Kidney function test
• Plain X-ray of the abdomen
• Ultrasound scan of the abdomen
• CT or CAT scan with contrast of the abdomen: This radiological procedure creates detailed 3-dimensional images of structures inside the body
• MRI scans of the abdomen: Magnetic resonance imaging (MRI) uses a magnetic field to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor
• Intravenous pyelogram (IVP): A dye is injected into the blood vessels and the image of kidney structure is obtained
• Vascular angiographic studies of the tumor may be performed

Invasive diagnostic procedures such as:

• Laparoscopy: A special device is inserted through a small hole into the abdomen, to visually examine it. If necessary, a tissue sample is obtained for further analysis. Exploration of the abdomen using a laparoscope is called ‘exploratory laparoscopy’
• Laparotomy: The abdomen is opened through an incision for examination, and if required, a biopsy sample obtained. Exploration of the abdomen using laparotomy procedure is called ‘exploratory laparotomy’

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include:

• Fine needle aspiration (FNA) biopsy of the kidney tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
• Core biopsy of the kidney tumor
• Open biopsy of the kidney tumor

Tissue biopsy:

• A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
• Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
• Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Oncocytosis of Kidney?

The complications of Oncocytosis of Kidney may include:

• Stress and anxiety due to a concern of kidney cancer
• Chronic renal failure affecting kidney function, if tumors are large; especially, when the condition is bilateral (affecting both kidneys)
• Damage to the muscles, vital nerves, and blood vessels, during surgery
• Post-surgical infection at the wound site is a potential complication
• Complications from an underlying disorder (if any)

How is Oncocytosis of Kidney Treated?

The treatment options vary from one individual to another. The treatment measures for Oncocytosis of Kidney may include the following:

• Undertaking treatment of the underlying condition, such as kidney disease or any renal carcinoma
• Genetic testing for BHD syndrome should be performed in individuals with Renal Oncocytosis
• Small and asymptomatic tumors: The healthcare provider may recommend a ‘wait and watch’ approach for small-sized tumors presenting mild signs and symptoms, after a diagnosis is made
• Surgical intervention with complete excision can result in a cure. It can also help reduce the chances of tumor recurrence

The surgical treatment methods may include:

• Endoscopic surgery
• Nephron-sparing surgery
• Partial or complete nephrectomy

A partial or complete nephrectomy may be considered, when large-sized tumors are noted in the kidneys.

• A kidney dialysis may be required, if the kidney function is severely compromised due to renal failure
• Postoperative care is important: A minimum activity level is ensured, until the surgical wound heals
• Follow-up care with regular screening may be recommended by the healthcare provider

How can Oncocytosis of Kidney be Prevented?

• Current medical research has not established a method of preventing Oncocytosis of Kidney
• Regular medical screening at periodic intervals with tests and physical examinations are recommended

What is the Prognosis of Oncocytosis of Kidney? (Outcomes/Resolutions)

• The prognosis of Oncocytosis of Kidney depends upon the severity of the signs and symptoms. It also depends upon the overall health of the individual. However, since these tumors are benign, the prognosis is generally good
• If the tumor is associated with an underlying condition, such as end-stage renal disease, renal cell carcinoma, or the genetic disorder Birt-Hogg-Dubé syndrome, then the overall prognosis is based upon the severity of the signs and symptoms of the associated condition

Additional and Relevant Useful Information for Oncocytosis of Kidney:

Please visit our Cancer & Benign Tumors Health Center for more physician-approved health information:

http://www.dovemed.com/diseases-conditions/cancer/