Differentials
Benign renal cyst
SIGNS / SYMPTOMS
Typically asymptomatic.
INVESTIGATIONS
Bosniak classification on imaging: low score (if questionable, interval change on imaging and/or pathology is distinguishing).[69]
Ureteric cancer
SIGNS / SYMPTOMS
Visible (gross) hematuria more common.
INVESTIGATIONS
Ureteroscopy: ureteric mass.
Bladder cancer
SIGNS / SYMPTOMS
Visible (gross) hematuria more common. Dysuria.
INVESTIGATIONS
Urine cytology: positive in up to 90% of patients with carcinoma in situ or high-grade tumors; positive in <33% of patients with low-grade transitional cell cancer.
Upper urinary tract urothelial tumor
SIGNS / SYMPTOMS
Visible (gross) hematuria more common.
INVESTIGATIONS
Gross pathology: transitional cell carcinoma histology.
Ureteroscopy: central renal mass (pelvis).
MRI: central pelvic/urethral location of mass.
Angiomyolipoma
SIGNS / SYMPTOMS
Clinically indistinguishable.
Often too small to present with palpable masses, and usually asymptomatic. May grow to cause pain and hematuria.
INVESTIGATIONS
CT/MRI: small (<1 cm); characteristic features (particular fat distribution). If questionable on imaging, and especially if 1-3 cm in size, percutaneous biopsy indicated.[69]
Oncocytoma
SIGNS / SYMPTOMS
Clinically indistinguishable.
Typically asymptomatic; often small.
INVESTIGATIONS
CT/MRI: small (1-3 cm), may have characteristic features (almost always solid, and nonenhancing). If questionable on imaging, percutaneous biopsy may be indicated.[69]
Secondary metastases
SIGNS / SYMPTOMS
Symptoms consistent with other primary tumors may point toward secondary metastatic renal lesions. Symptoms from local disease burden less likely (the masses are generally smaller but multifocal).[68]
Congenital renal parenchymal abnormalities
SIGNS / SYMPTOMS
Often no distinguishing symptoms or signs.
INVESTIGATIONS
CT and MRI (especially the latter) can usually help distinguish.
Renal infarction
SIGNS / SYMPTOMS
Clinical history of vascular risk factors may raise suspicion of infarction (especially poorly controlled hypertension/hypertensive crisis).
INVESTIGATIONS
MRI: assesses kidney and determines likelihood of infarction.
Magnetic resonance angiogram: assesses local vessels.
Renal infection
SIGNS / SYMPTOMS
Clinical history of fever or sepsis.
INVESTIGATIONS
CBC: leukocytosis.
Blood culture: bacteremia. Urine culture: bacteriuria.
Serial imaging (CT/MRI) may be needed to ensure resolution of renal mass after treatment for infection.
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