Little Tumors in the Kidney: Challenges and Solutions

Andrew Siegel MD    6/2/18

Years ago–prior to the advent of advanced means of imaging the abdomen–malignant growths of the kidney would manifest with symptoms.  The “classic triad” of symptoms and signs were pain, blood in the urine and a mass that could be felt on examination.  Nowadays, the vast majority of renal masses are asymptomatic, incidental (unexpected) findings picked up on imaging studies done for other issues. The widespread and liberal use of ultrasound, computerized tomography (CT) and magnetic resonance imaging (MRI) done for a variety of reasons not uncommonly result in the incidental finding of a small mass in the kidney, known as a small renal mass (SRM).  Urologists are the go-to doctors who manage renal masses, including SRMs, which can present challenges in term of how best to manage it.


SRM of right kidney on CT


So, what to do when one is found to have a small mass in the kidney, often less than one inch (2.5 cm) in diameter?

A CT or MRI imaging study without and with contrast is recommended for the assessment of renal masses. The premise is that when a mass takes up contrast, it has a blood supply and is usually not a simple benign cyst containing fluid, but a solid mass that is considered malignant until proven otherwise.  Although these studies are capable of diagnosing and evaluating solid renal masses and distinguishing them from fluid-filled cysts, neither study is capable of distinguishing benign from malignant.

One possibility to address the shortcomings of CT and MRI is a CT-guided kidney biopsy.  It is an outpatient procedure performed by an interventional radiologist who obtains a tiny biopsy of the area of concern using CT guidance.  The biopsy is microscopically studied by a pathologist.  This can distinguish benign from malignant as well as provide tumor type and grade.  Such a biopsy can reduce unnecessary surgery for benign lesions and guide the selection of patients appropriate for monitoring and those who need to be treated.

Fact: About 20% of SRMs are potentially aggressive kidney cancers, 50% exhibit slow growth and are unlikely to ever be a problem, and 30% are benign.

Prognostic factors

Size is of significance, as larger masses have a higher risk of being malignant.  Mass size also predicts the possibility of spread, with a 2.4% risk in tumors under 3 cm versus 8.4% for tumors 3 – 4 cm. Another important factor is tumor growth rate, the average being 0.1 – 0.4 cm/year. Rapidly growing masses are at higher risk for progression and spread.

To treat or not

Active surveillance—careful interval imaging and follow-up with consideration for intervention if the situation merits a change—is a prudent means of management of the SRM in elderly patients, in those with significant medical problems who have a limited life expectancy, and those at high risk for surgery and surgical complications. Active surveillance is also an excellent option in patients who have a solitary kidney or significant kidney disease. Clinical studies have shown that management of SRMs with initial surveillance and delayed intervention does not compromise the success of the surgery or increase the risk of local spread or metastases.

On the other hand, a young, healthy patient with a long life expectancy merits definitive treatment. Typical treatment options are partial nephrectomy versus tumor ablation.  Partial nephrectomy is most often done via laparoscopy with robotic assistance and removes the mass with a margin of normal tissue, sparing the bulk of the kidney. An ultrasound probe is used to help the surgeon precisely image the tumor and its margins.

An alternative option is tumor ablation– the application of heat (radio-frequency) or cold (cryosurgery) directly into the SRM–in an effort to destroy the tumor while leaving the remaining kidney intact.  This can be performed percutaneously (using a needle placed through the skin without an incision) via CT imaging.

Wishing you the best of health,

2014-04-23 20:16:29

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Dr. Andrew Siegel is a physician and urological surgeon who is board-certified in urology as well as in female pelvic medicine and reconstructive surgery.  He is an Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and is a Castle Connolly Top Doctor New York Metro Area, Inside Jersey Top Doctor and Inside Jersey Top Doctor for Women’s Health. His mission is to “bridge the gap” between the public and the medical community.

Dr. Siegel has authored the following books that are available on Amazon, iBooks, Nook and Kobo:

MALE PELVIC FITNESS: Optimizing Sexual & Urinary Health

THE KEGEL FIX: Recharging Female Pelvic, Sexual and Urinary Health 

PROMISCUOUS EATING: Understanding and Ending Our Self-Destructive Relationship with Food


These books are written for educated and discerning men and women who care about health, well-being, fitness and nutrition and enjoy feeling confident and strong.

Dr. Siegel is co-creator of the male pelvic floor exercise instructional DVD (the female version is in the works): PelvicRx


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