Renal functional reserve may be improved in patients with simple renal cysts after laparoscopic deroofing.

Simple renal cysts (SRC) are the most frequent type of cystic renal disease. The prevalence rate of SRCs is about 10% and increases with age. Hypertension and decreased renal functions have been reported to occur more commonly among these patients with SRC and there are no clear guidelines for managing asymptomatic SRCs.Renal functional reserve (RFR) describes the capacity of the intact nephron mass to increase glomerular filtration rate(GFR) from baseline in response to stimuli (e.g., protein load).The investigators hypothesized that RFR may be improved in some patients with simple renal cysts after laparoscopic deroofing despite identical resting glomerular filtration rate (rGFR).The aim of this study is to examine whether there is improvement of RFR in patients with simple renal cysts after laparoscopic deroofing.

Inclusion Criteria:

1. Age ≥18
2. Estimated GFR >30 mL/min/1.73m2
3. Subjects who signed informed consent forms

Exclusion Criteria:

1. Allergy to iothalamate, shellfish or iodine
2. Use of metformin or amiodarone
3. Inability to maintain a stable regimen of medications which affect GFR for > one week prior to participation (e.g. non-steroidal anti-inflammatory drugs, angiotensin converting enzyme inhibitors, angiotensin receptor blockers)
4. Use of medications which directly affect elimination of creatinine (e.g. cimetidine and trimethoprim)
5. Acute exacerbation of asthma or chronic obstructive pulmonary disease within 3 months requiring hospitalization or oral steroid therapy
6. Inadequate intravenous access
7. Severe anemia (Hct <21%)
8. Acute kidney injury (rise in creatinine to ≥1.5 times the previous baseline or by ≥ 0.3 mg/dL on most recent labs prior to enrollment)
9. History of contrast-induced nephropathy
10. Hyperthyroidism
11. Pheochromocytoma
12. Sickle cell disease
13. Urinary retention or incontinence
14. Status post organ transplant
15. Pregnancy or active breast feeding
16. Cognitive impairment with inability to give consent
17. Institutionalized status