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Kidney Diseases

Large simple cyst, eGFR below 60

07/08/2010

Question:

A recent lumbar MRI gave an incidental finding of a large (7 cm) left kidney cyst, slightly larger than the kidney itself. Follow-up ultrasound showed a simple cyst, no stones or other findings.

Symptoms have included occasionally higher blood pressure eg 145/84, eGFR below 60, flank pain now lessened but with a feeling fullness and pressure, and some discomfort in the left leg. I seem to be reacting poorly to some to medications now, eg a trial of felodipine resulted in tea-colored urine and fatigue; a second MRI with gadolinium contrast within 6 months of the first MRI with contrast resulted in frothy urine, metallic taste, could not bend index finger where contrast had been injected into forearm, slept 20 hrs, eGFR went to 45.

How do large simple cysts affect kidney function? How large is large? Does a cyst like this increase risk of infection? When should surgery be considered? I have an autoimmune condition (UCTD) and want to preserve as much kidney function as possible, and avoid additional medications if possible.

Female, 56, 5`9, 155 lbs.

Answer:

The cyst on your left kidney is unlikely to be responsible for any of the symptoms or lab values that you have.  Such cysts are common, especially in people over the age of 50 who have hypertension and/or underlying kidney disease.  These cysts can occasionally become quite large (even larger than yours).  Your cyst should not cause pain, should not become malignant, and should not have a risk of becoming infected. 

It does sound like you have significant underlying kidney disease.  It is interesting that you say that your 7-cm cyst is larger than the kidney itself; normal kidney size is 10-13 cm, so yours is small presumably because of scarring due to underlying disease, most likely hypertension and/or the connective tissue disorder.  You are right to be concerned about preserving your remaining kidney function, which you can help to do by taking your blood pressure meds religiously, avoiding salt in your diet, taking cholesterol-lowering meds if needed, and not smoking.  It would also be advisable to avoid gadolinium if your eGFR goes any lower, as gadolinium use can be associated with adverse effects in patients with advanced renal failure.  However, if for instance a followup kidney MRI is needed, this can be done without gad and can still provide a lot of information.

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Response by:

Mildred   Lam, MD Mildred Lam, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University