Since the initial report in 1991 by Clayman et al,1 laparoscopic nephrectomy has been popularized for various kidney diseases. The major advantages of laparoscopic nephrectomy over open nephrectomy include decreased perioperative morbidity, less blood loss, shorter hospital stays, and quicker convalescence.2,3

While complication rates from laparoscopic procedures are comparable to those of open procedures,4-6 the presentation of these complications can be quite different following laparoscopic versus open nephrectomy. Intraoperative oliguria is common during laparoscopy, but is transient and resolves after desufflation.7,8 The effects of pneumoperitoneum at 15 mmHg on renal function during short laparoscopic operations has been shown to be minimal, but patients with pre-existing renal dysfunction or patients undergoing prolonged laparoscopic operations might be at risk for postoperative renal impairment.9

Laparoscopic surgeries commonly increase the operative time and there are adverse effects of a pneumoperitoneum on urine output and renal function; however, there are no long-term studies regarding renal function after laparoscopic surgery. The purpose of our trial was to compare the renal function outcomes in patients undergoing open and laparoscopic radical nephrectomy.

Seventy-one patients between January 2004 and December 2007 undergoing open or laparoscopic radical nephrectomy for kidney disease were identified. The operations included open radical and laparoscopic radical nephrectomies. Intraabdominal gas pressure was 15 mmHg during laparoscopic operation. Preoperative data, including patient co-morbidities, such as hypertension, diabetes mellitus, cerebrovascular disease, renal mass characteristics, body mass index, and intraoperative data, including operative time, estimated blood loss, approach method were obtained retrospectively.

The contralateral kidney was assessed on computed tomography (CT scan) and excluded if abnormal findings were present. Exclusion criteria were pre-existing renal insufficiency (glomerular filtration rate <60 ml/min.), uncontrolled diabetes mellitus, urinary stone disease, contralateral ureteropelvic junction stricture, liver disorders, conversion to open surgery, and intraoperative complications such as pancreatic, bowel, splenic injury. The glomerular filtration rate as renal function was obtained using serum creatinine on the day prior to surgery, the day of surgery, and postoperative days 1, 2, 3, 7, 30, 90, 180, and 360. The glomerular filtration rate was calculated using the Cockcroft-Gault formula (creatinine clearance [ml/min]=[140-age]xlean body weight [kg]/plasma creatinine [ml/dl])×72×[0.85 if women]).

The groups were compared to determine whether there was a significant difference between changes in renal function following open and laparoscopic radical nephrectomy. The mean differences between the two independent groups with nonparametric data were analyzed using Mann-Whitney U tests and the sex and co-morbidities were analyzed using Fisher's exact test. All analyses were performed with SPSS 13.0. p-value of less than 0.05 was considered statistically significant.

Forty-one and 30 patients were treated with open and laparoscopic radical nephrectomy, respectively. The number and types of nephrectomies were as follows: open radical (41 cases) and laparoscopic radical (30 cases). The median ages of the patients were 56 years (range, 43-74 years) and 54 years (range, 48-68 years) for open and laparoscopic surgery, respectively. Operation times were 211 minutes (range, 130-395 minutes) and 330 minutes (range, 145-475 minutes), and urine outputs were 196 ml/hr (range, 85-350 ml/hr) and 130 ml/hr (range, 55-195 ml/hr) and estimated blood losses were 729 ml (range, 350-2,600 ml) and 645 ml (range, 260-950 ml), open and laparoscopic nephrectomy, respectively (p=0.001, p=0.013, p=0.139). Table 1 shows the patient and operative data for each of these procedure groups.

On postoperative days 3 and 7, the glomerular filtration rates of patients who underwent open and laparoscopic nephrectomy were 68.24 and 59.70 ml/min., and 70.17 and 59.75 ml/min., respectively. On postoperative day 360, the glomerular filtration rates of patients who underwent open and laparoscopic nephrectomy were 61.44 and 60.51 ml/min., respectively. Table 2 presents the serial glomerular filtration rates differences from the baseline of the two groups. In process of time, the differences of glomerular filtration rates increased, but there was no statistical significance (p<0.05). These results indicate that the pneumoperitoneum did not affect a decline in renal function for a short and long period.

Removal of one kidney increases the serum creatinine by up to 20%, with functional hypertrophy of the remaining normal contralateral kidney.10 So, we excluded pre-existing renal insufficiency, uncontrolled diabetes mellitus, urinary stone disease, contralateral ureteropelvic junction strictures, liver disorders, and conversion to open surgery, and assessed the contralateral kidney using CT scan to obtain a pure glomerular filtration rate. According to our results, a significant decline in renal function was detected in the group of patients undergoing laparoscopic nephrectomy rather than open nephrectomy in the short-term, but there was no difference in renal function between the two groups in the long-term.

Commonly, acute increased intraabdominal pressure has an adverse effect on renal function. Rapid elevation of intraabdominal pressure (>25 mmHg) can result in acute renal insufficiency and abdominal decompression causes immediate improvement.11 Increasing intraabdominal pressure from 0-20 mmHg decreases the glomerular filtration rate by 21% and increases renal vascular resistance by 555%.12 Urinary N-acetyl-B-D-glucosaminidase is an indicator of potential renal tubular damage, and a pneumoperitonem results in a considerably higher excretion of N-acetyl-B-D-glucosaminidase in patients who underwent laparoscopic cholecystectomy compared with patients who underwent cholecystectomy performed by an abdominal wall lift method.13 The adverse effects of increased intraabdominal pressure on intraoperative urine output have been reported during laparoscopic surgery.7,8,13 If abdominal pressure is maintained constantly at 15 mmHg, oliguria has been reported, even during short laparoscopic procedures.8

The mechanism for intraoperative oliguria during laparoscopy has been implicated with increased intraabdominal pressure, which has a direct compressive effect on the kidney parenchyma and renal vessels. The direct pressure effect on the renal vasculature results in decreased renal blood flow.14 In a swine study, elevated intraabdominal pressure increased plasma renin activation and aldosterone levels and abdominal decompression decreased both of these levels.15 But the reduction in intraoperative urinary output did not adversely affect renal function.16 No change in BUN or serum creatinine levels was observed after laparoscopic surgery. In addition, creatinine clearance was in the normal range after laparoscopic surgery on both postoperative days 1 and 2. After laparoscopic adrenalectomy, when compared with gasless laparoscopic adrenalectomy, there was no change in serum creatinine.17

In our study, hourly urine output was decreased in the laparoscopic surgery group compared to the open surgery group, but a significant decline in the glomerular filtration rate was not detected in the group of patients who underwent laparoscopic surgery. A pneumoperitoneum does not affect renal function in the short-term and the long-term follow-up period. Despite the intraoperative oliguria, a prolonged pneumoperitoneum was clinically safe with respect to renal function as there was no alteration in postoperative renal function including chronic kidney disease patients.18-20

Colombo et al10 reviewed renal function outcomes retrospectively after laparoscopic or open radical nephrectomy. They concluded that there was no difference in renal functional outcomes between the groups who underwent unilateral laparoscopic and open radical nephrectomy at a median follow-up of 51 months. The serum creatinine increased by up to 20%, with functional hypertrophy of the remaining kidney, which can compensate for the decrease in the overall glomerular filtration rate after removal of one kidney. Baseline risk factors, such as age, hypertension, diabetes, and obesity were not significantly associated with postoperative renal function based on univariate analysis. McKiernan et al21 showed a mean increase in serum creatinine of 0.5 mg/dl in 173 patients who had undergone radical nephrectomy after a follow-up of 25 months.

The limitations of Cockcroft-Gault formula using serum creatinine as opposed to timed urine collections are that the equation systemically underestimates glomerular filtration rate in healthy persons with high-normal serum creatinine levels, and overestimates the prevalence of a reduced glomerular filtration rate in the general population. And even though glomerular filtration rate estimating equations contain a variable for sex, it remains unclear whether men or women are at higher risk for a reduced glomerular filtration rate. The weaknesses of this study include its retrospective design, small sample size, effect of one kidney removal, and lack of other laboratory findings, such as renin and aldosterone. Further studies are required to examine other mechanisms that might account for the decreased renal function and reduced urine output during laparoscopic surgery, such as reduced renal blood flow, decreased perfusion of the renal cortex and medulla, or perhaps an alteration in the expression of mediators related to renal blood flow.

A significant difference in renal function was not detected in the group of patients who underwent open and laparoscopic radical nephrectomy from baseline to long-term follow-up.