Can Simple Renal Cysts Cause Microscopic Hematuria?
Simple renal cysts do not directly cause microscopic hematuria and should be considered an incidental finding when both are present together. When hematuria and simple renal cysts coexist, the hematuria warrants independent evaluation to identify its true cause.
Evidence Against Causation
The strongest evidence demonstrates that simple renal cysts are coincidental findings rather than causes of hematuria:
A prospective study of 93 patients with simple renal cysts found that when proteinuria and/or hematuria were present, an alternative cause was always identified (IgA nephropathy, vesical carcinoma, renal lithiasis, or nephroangiosclerosis), leading investigators to conclude these alterations should be considered coincidental rather than caused by the cysts 1
In a large series of 743 patients with asymptomatic microscopic hematuria who underwent ultrasonography, the degree of hematuria did not correlate with the incidence of renal cysts (P = 0.9044), and the presence of microhematuria in 40% of patients with simple cysts was not attributed to the cysts themselves 2
A Japanese study of 170 patients with simple renal cysts found microhematuria in 40% of cases, but the grade of microhematuria was not correlated with cyst size, suggesting the hematuria had other etiologies 3
Clinical Implications for Workup
When microscopic hematuria is discovered in a patient with simple renal cysts, proceed with standard hematuria evaluation:
Do not attribute the hematuria to the cyst without completing a full urologic evaluation, which should include comprehensive urine examination, assessment for dysmorphic red blood cells or red cell casts, testing for proteinuria and urinary tract infection, measurement of serum creatinine, radiologic imaging of the upper urinary tract, and cystoscopic examination 4
The ACR Appropriateness Criteria note that while ultrasound may be used to evaluate for occult anatomic abnormalities including cystic renal disease in cases of persistent unexplained microhematuria, the yield of these examinations is low and imaging findings are usually not specific for any underlying pathology 5
Anticoagulation therapy, BPH, and simple renal cysts are common findings that should not preclude thorough evaluation of persistent microscopic hematuria, as other significant pathology may be present 4, 6
Risk Stratification and Follow-Up
Patients should be stratified based on actual risk factors for urologic malignancy (age, smoking history, degree of hematuria >25 RBC/HPF), not on the presence of simple renal cysts 4, 6
For patients with persistent hematuria after negative initial evaluation, repeat urinalysis, urine cytology, and blood pressure determination at 6,12,24, and 36 months is recommended, with nephrology referral if hematuria persists with development of hypertension, proteinuria, or evidence of glomerular bleeding 4, 7
Common Pitfalls to Avoid
Do not assume simple renal cysts explain the hematuria—this can lead to missed diagnoses of malignancy, glomerulonephritis, urolithiasis, or other significant pathology 1
The presence of simple renal cysts in a patient with hematuria represents two common findings occurring together by chance, particularly in older patients where cyst incidence increases with age 3, 2
While renal cysts can rarely cause symptoms (pain, collecting system compression, secondary infection), hematuria from cysts is not a recognized clinical presentation 8