Original Article: Clinical Investigationiju_2791 570..575

Mercaptoacetyltriglycine-3 renogram is not superior toestimated glomerular ltration rate measurement for theprediction of long-term renal function after nephrectomyHiroshi Kanamaru, Masakazu Yamamoto, Kanji Nagahama, Yusuke Yagihashi, Keiji Kato,Tomoyuki Oida, Toru Kannno, Noriyasu Takao, Yusuke Shimizu and Yasumasa ShichiriDepartment of Urology, Kitano Hospital, Tazuke Kofukai Medical Research Institute, Osaka, Japan

Objective: To evaluate the clinical usefulness of effective renal plasma ow (ERPF) measured using preoperativemercaptoacetyltriglycine-3 (MAG3) renogram for the prediction of chronic renal insufciency after nephrectomy.Methods: A total of 47 patients underwent preoperative MAG3 renal scintigraphy and subsequent unilateral nephrec-tomy. Correlations between the 5-year postoperative estimated glomerular ltration rate (eGFR) and the preoperative ERPFof the contralateral kidney (cERPF), ERPF of the diseased kidney (dERPF), total ERPF (tERPF), cERPF to dERPF ratio, serumcreatinine (sCr) level, eGFR, as well as the inuence of preoperative comorbidities (diabetes, hypertension) on the post-operative eGFR, were evaluated with both univariate and multivariate analyses.Results: Multiple linear regression analysis showed that preoperative cERPF signicantly correlated with postoperativeeGFR. However, a much stronger correlation was observed between the preoperative and postoperative eGFR. Multiplelogistic regression analysis showed that only preoperative eGFR was a signicant predicator of the development ofadvanced-stage chronic kidney disease (CKD).Conclusions: PreoperativeMAG3 renogram is not superior to eGFRmeasurement as a prognostic indicator of long-termrenal function after unilateral nephrectomy.

Key words: chronic kidney disease, mercaptoacetyltriglycine-3 renogram, nephrectomy.

Introduction

Surgical treatments for kidney disease are associated withthe risk of postoperative chronic kidney disease (CKD).Among renal surgeries, nephrectomy has the greatest riskfor CKD, because one of the two renal units is permanentlyremoved.16 Therefore, it is important to accurately predictlong-term postoperative renal function before nephrectomy.It is possible to preoperatively assess differential renalfunction using renal scintigraphy and other modalities(computed tomography, magnetic resonance imaging).7,8

However, the predictability of such modalities for CKD aftera long observation period has not been reported. The presentstudy was carried out to evaluate the clinical usefulness ofeffective renal plasma flow (ERPF) measured usingmercaptoacetyltriglycine-3 (MAG3) renogram for the pre-diction of renal function 5 years after nephrectomy, as com-pared with other clinical parameters.

Methods

Patients

Between 2002 and 2005, 88 patients underwent unilateralnephrectomy in Kitano Hospital, Osaka, Japan. MAG3 renalscintigraphy was carried out in 74 of the 88 patients beforesurgery. The present study included 47 out of the 74 patientswho were followed for more than 5 years. The reason forsurgery was as follows: 25 cases of renal cell carcinoma, 16cases of urothelial cancer, two cases of pyonephrosis, twocases of angiomyolipoma, one case of urolithiasis and onecase of oncocytoma. Out of the 37 male and 10 femalepatients, the mean age was 65 years, with a range of 3882.A preoperative medical history of diabetes mellitus andhypertension were noted in eight and 20 patients, respec-tively. The present study was approved by the institutionalethics committee.

MAG3 renogram

After an intravenous injection of 333 MBq of technetium-99m-mercaptoacetyltriglycine (99mTc-MAG3), a renal scanwas carried out using a gamma-camera (Forte; ADAC, Mil-pitas, CA, USA). The MAG3 plasma clearance was calcu-lated based on the renal uptake of 99m-Tc-MAG3 from 1 to

Correspondence: Hiroshi Kanamaru M.D., Ph.D., Department ofUrology, Kitano Hospital, Tazuke Kofukai Medical ResearchInstitute, 2-4-20, Ohgimachi, Kita-ku, Osaka 530-8480, Japan.Email: h-kanamaru@kitano-hp.or.jp

Received 15 November 2010; accepted 14 May 2011.Online publication 12 June 2011

International Journal of Urology (2011) 18, 570574 doi: 10.1111/j.1442-2042.2011.02791.x

570 2011 The Japanese Urological Association

2 min postinjection, according to the method described byOriuchi,9 and effective renal plasma flow (ERPF), whichwas normalized to a body surface area of 1.73 m2, wasdetermined. The ERPF from the kidney that would remainafter nephrectomy was designated the contralateral ERPF(cERPF). The ERPF from the kidney that would be removedon operation was designated the diseased ERPF (dERPF).The sum of ERPF from bilateral kidneys was designatedtotal ERPF (tERPF).

eGFR

Serum creatinine (sCr) was measured before the surgery and5 years later. The eGFR levels were calculated using thefollowing formula, which was developed by the JapaneseSociety of Nephrology:10 eGFR = 194 sCr-1.094 age-0.287

(0.739 if female).

Statistics

We used the paired t-test to compare the differences betweenpreoperative and postoperative renal parameters (sCr andeGFR). Students t-test was used to compare postoperativeeGFR between patients with and without preoperativecomorbidities. The correlations between preoperative renalparameters and postoperative eGFR were analyzed usingPearsons correlation test. Multiple linear regression analy-sis was carried out to evaluate the contribution of preopera-tive renal parameters to predicting postoperative eGFR.Logistic regression analysis was carried out to evaluate thepreoperative parameters used to predict advanced-stageCKD (eGFR

Postop eGFR (mL/min/1.73m2)

(a)

Preop cERPF (mL/min/1.73m2)

80

60

40

20

0100 200 300

r = 0.421P = 0.003

400

Postop eGFR (mL/min/1.73m2)

(b)

Preop dERPF (mL/min/1.73m2)

80

60

40

20

01000 200 300

r = 0.515P = 0.0001

400

Postop eGFR (mL/min/1.73m2)

(c)

Preop tERPF (mL/min/1.73m2)

80

60

40

20

0100 200 300

r = 0.566P = 0.0001

600500 800400 700

Postop eGFR (mL/min/1.73m2)

(d)

Preop cERPF to dERPF ratio

80

60

40

20

020 4 6

r = 0.260P = 0.077

8

Postop eGFR (mL/min/1.73m2)

(e)

Preop sCr (mg/dL)

80

60

40

20

00 1

r = 0.672P = 0.0001

2 3

Postop eGFR (mL/min/1.73m2)

(f)

Preop eGFR (mL/min/1.73m2)

80

60

40

20

0200 40 60 80 100

r = 0.798P = 0.0001

120

Fig. 1 (a) Correlation between preoperative effective renal plasma ow (ERPF) of the contralateral kidney (cERPF) and 5-yearpostoperative estimated glomerular ltration rate (eGFR). (b) Correlation between preoperative ERPF of the diseased kidney (dERPF)and 5-year postoperative eGFR. (c) Correlation between preoperative total ERPF (tERPF) and 5-year postoperative eGFR. (d) Corre-lation between preoperative cERPF to dERPF ratio and 5-year postoperative eGFR. (e) Correlation between preoperative serumcreatinine (sCr) and 5-year postoperative eGFR. (f) Correlation between preoperative eGFR and 5-year postoperative eGFR.

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572 2011 The Japanese Urological Association

There were six patients who developed advanced-stageCKD (eGFR less than 30 mL/min/1.73 m2) 5 years after theoperation. A multiple logistic regression analysis includingpreoperative eGFR, cERPF and hypertension showed thatonly preoperative eGFR was a significant predictor foradvanced-stage CKD (Table 3).

We divided the patients into two subgroups according tothe preoperative eGFR using the cut-off value of 60 mL/min/1.73 m2. The 5-year postoperative eGFR remained>30 mL/min/1.73 m2 in all the patients whose preoperativeeGFR were >60 mL/min/1.73 m2. By contrast, 5-year post-operative eGFR were less than 30 mL/min/1.73 m2 in 27%(6/22) of the patients whose preoperative eGFR were

preoperative function of the resected (diseased) kidney onthe postoperative compensatory response of the contralat-eral kidney. Funahashi18 studied the change in renal paren-chymal volume (RPV) after unilateral nephrectomy andreported that the increase in RPV of the contralateral kidneywas positively associated with preoperative DMSA uptakeof the diseased kidney. We therefore analyzed the impact oftwo diseased kidney-related parameters (cERPF to dERPFratio and dERPF) on postoperative eGFR. However, cERPFto dERPF ratio did not show a significant correlation withpostoperative eGFR. Although dERPF was significantly cor-related with postoperative eGFR on univariate analysis, itfailed to be an independent predictor of postoperative eGFRon multivariate analysis.

The other possible explanation is that RPF is closelyrelated, but physiologically not equivalent, to GFR. Thelimitations of the present study are the relatively smallsample size and the fact that we did not assess postoperativeERPF. If we could include both eGFR and ERPF as postop-erative renal parameters, a more detailed analysis would bepossible.

In conclusion, the present study showed that a preopera-tive MAG3 renogram is not superior to simple and inexpen-sive eGFR measurements as a prognostic indicator of futurerenal function after unilateral nephrectomy.

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