Percutaneous Lithotripsy in Morbid Obesity

0022-5347 /88/:C392-0243$02,00/0 Vol. 139 February Printed in U3-k

THE JOURNAL OF UROLOGY

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Copyright© 1988 by The Williams & VVilkins Co.

PERCUTANEOUS LITHOTRIPSY IN MORBID OBESITY CULLEY C. CARSON, HI,* JOHN E. DANNEBERGER

AND

JOHN L. WEINERTH

From the Division of Urologic Surgery, Duke University Medical Center, Durham, North Carolina

ABSTRACT

Percutaneous lithotripsy is an established, safe, effective method for the management of renal calculi. Obesity long has been associated with increased surgical morbidity and may eliminate a patient from shock wave treatment. We compared 44 obese patients to 226 nonobese patients undergoing percutaneous stone management. Stone number, location and total stone burden were comparable in the obese and nonobese groups. There was no significant difference between the groups in hospital time, operative time, fragment rate, access success rate or morbidity. Percutaneous procedures offer successful alternatives with low morbidity for patients with renal calculous disease. (J. Ural., 139: 243-245, 1988) Successful percutaneous removal of renal calculi is a result of recent technological advances and it is well established. 1- 5 The procedure is associated with high success rates, few early or delayed complications and only rare sequelae. Newer modalities, including extraco:rporeal shock wave lithotripsy (ESWL t), have supplanted percutaneous procedures in some patients. However, the limitations of patient size for the current ESWL machines produce a dilemma for urologists treating patients with renal calculi who weigh more than 280 pounds. Since current ESWL technology is not acceptable for patients with massive morbid obesity, percutaneous procedures may be used best to remove stones in this patient population. The risks of medical complications of morbid obesity have been well defined but the risks of obesity and surgical procedures are less clear, although they usually are accepted as high. 6 • 7 Despite the prevalence of obesity and the impression that excessive surgical risk in obese patients is present, few studies of the extent of this risk have been performed. We compared the results of percutaneous stone removal in 226 patients in a computer data base with a group of 44 obese patients. PATIENTS AND METHODS

The 226 patients who had undergone percutaneous stone manipulation and whose records were contained in a computer data base were compared to 2 groups of patients varying from at least 20 to greater than 50 per cent over ideal body weight. Ideal body weights were obtained from the upper limit of weights provided by the standard 1985 Metropolitan height and weight tables. 8 Obese patients were divided into 2 groups, weight including 30 patients 20 to 50 per cent over ideal (group A, 12 men and 18 women) and 14 patients more than 50 per cent over ideal body weight (group B, 8 men and 6 women). These patients varied in weight from 185 to 384 pounds. The average age of the control population (132 men and 50 women) was 47.8 years compared to 52 years in group A and 41. 7 years in group B. When the characteristics of the calculi in each group were evaluated no significant difference was observed (table 1). The numbers of stones present and treated were 1. 7 in the control group compared to 1.8 in group A and 1.7 in group B. Total stone burden was equivalent, with 1.6 cm. stones in each group. There were no significant differences among the groups in regard to stones within the renal pelvis, renal calices and ureter. Similarly, the percentage of patients with staghorn calculi was similar in each group: 7.5 per cent in the control group, 0 per Accepted for publication June 22, 1987. * Requests for reprints: Box 3274, Duke University Medical Center, Durham, North Carolina 27710. t Dornier Medical Systems, Inc., Marietta, Georgia. 243

cent in group A and 7.1 per cent in group B. These percentages were not statistically significantly different. Our technique of percutaneous nephrolithotripsy has been described in detail previously. 1· 3 At the conclusion of the procedure we routinely position a straight 5F catheter with multiple side holes in the distal ureter. Since this 5F stent only remains for 24 hours, urete:ral stenosis or edema has not been observed. A nephrostomy tube then is positioned within the renal pelvis and confirmed fluoroscopically. A simple, straightforward procedure requires a lOF polyurethane self-retaining nephrostomy tube, while the more challenging procedure, which may require further manipulation, is drained with a 22F Councill catheter to maintain tract size and patency. Plain radiographs, tomograms and nephrostograms are obtained within 48 hours postoperatively. If no stone fragments are demonstrated and the collecting system is intact, the ureteral stent is removed and the nephrostomy tube is clamped. This tube in turn is removed once the patient has tolerated internal drainage for 24 hours. An attempt is made to extract any retained fragments with the patient under local anesthesia under fluoroscopic control. If extraction is impossible we either perform an additional procedure at that time or decide that the stone is clinically insignificant and that no further attempt should be made. Clinically insignificant fragments are less than 3 mm. in size, requiring additional percutaneous access as has been reported previously. 2 In such an event and after the situation is discussed with the patient the neph:rostomy catheter is clamped. Results of treatment in each group were evaluated by endoscopy and fluoroscopy at the end of the procedure, and plain films, contrast films and tomograms immediately postoperatively, during hospitalization and after the patient is discharged from the hospital. RESULTS

Average hospitalization was 6.8 days in the control group, 6.2 days in group A and 6.9 days in group B. These numbers were not statistically significantly different. Success of access placement was 96 per cent in the control patients, compared to 100 per cent in group A and 92.9 per cent in group B. While not statistically significant, loss or displacement of the nephrostomy tube occurred more frequently in obese than in control patients. Operating time also was not statistically significantly different: 53.5 minutes in the controls, 52.8 minutes in group A and 55.4 minutes in group B. Secondary procedures were necessary in 31.3 per cent of the controls, 33 per cent of group A and 21.4 per cent of group B patients. These differences also were not statistically significantly different. There also were no statistically significant differences among the groups in

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CARSON, DANNEBERGER AND WEINERTH TABLE

1. Obesity and outcome of percutaneous procedures Control

No. pts. Wt. (pounds) Calculi:* Av. No. Size (cm.) No. staghorn (%) No. access success(%)* Operating time (mins.)* No. secondary procedures (%)* Hospital stay (days)* No. retained fragments (%):* No. clinically insignificant(%)

226 34-185

Group A 30 152-210 1.8 1.6

14 187-384

1.7 1.6 17 (7.5) 209 (96) 53.5 64 (28.6)

30 (100) 52.8 13 (43.3)

1.7 1.8 1 (7.1) 13 (92.9) 55.4 3 (21.4)

6.8 36 (16.1)

6.2 5 (16.7)

6.9 2 (14.3)

30 (13.3)

5 (16.7)

1 (7.2)

0

(0)

TABLE

2. Complications in obese stone patients treated percutaneously

Group B

* No statistical difference among groups.

regard to medical complications, including cardiac, pulmonary and infectious complications, and ileus (table 2). The unplanned fragment rate was similar, with 16.1 per cent of the control group demonstrating unplanned fragments compared to 16.7 and 14.3 per cent for groups A and B, respectively. Two per cent of the control patients required an open operation to complete the therapeutic goal, while none in the obese groups required open surgery. DISCUSSION

Most series on percutaneous nephrolithotripsy describe high success rates without evaluating patients for body morphology.1-5 As the percutaneous approach to upper urinary tract calculi becomes more common and is supplemented by ESWL, more selection must be performed to identify appropriate patients for each of these procedures. Since body weight is a criterion for exclusion from ESWL with current technology, alternate treatment of obese patients via current methods must be considered. To this end percutaneous nephrolithotripsy is an appropriate and effective method to remove stones in patients who are too heavy or too large for the ESWL machine. The incidence of significant complications and difficulty with percutaneous tube placement in our patients was not different from the patients with normal body weight and size. Access placement was equally as successful in all groups of patients, requiring no more second attempts, no more ureteral catheters and no special procedures to position an access tract for optimal stone removal despite excessive body weight and size. While some consideration must be given to the distance between the skin surface and the interior of the kidney, since instrumentation available for percutaneous nephrolithotripsy may be too short to access long percutaneous tracts, this was not an exclusion factor nor a cause of percutaneous procedure failure in any of our patients. However, we do recommend that the distances between the skin and stone to be manipulated should be measured with ultrasound in patients in whom there is a significant question of the distance to be traversed during extraction. Our obese patients further demonstrated no increase in hospital stay, medical complications, bleeding, retained stone fragments or nephrostomy tube drainage despite body weights in some cases or more than 300 pounds. The most significant problem with management of these patients was the increased nephrostomy tube displacement that occurred in the obese patients. All of the nephrostomy tubes that were dislodged were small, lOF self-retaining catheters and not the larger 22F balloon type catheters. Similarly, no tubes that were passed to the bladder were lost. Therefore, it is important to choose a substantial nephrostomy tube that can be secured at the kidney and skin levels. Furthermore, an access that is long enough to pass into the bladder may be helpful for re-entry if the nephrostomy tube becomes dislodged. These data demonstrate the effectiveness, safety and success rates to be expected from percutaneous procedures despite adverse body morphology.

Pulmonary Urinary infection Hemorrhage Tube loss

Control No.(%)

Group A No.(%)

15 (6.9) 3 (1.3) 11 (4.9) 8 (3.6)

2 1 0 3

(6.7) (3.3) (0) (10)

Group B No.(%) 0 0 0 1

(0) (0) (0) (7.1)

There were no statistical differences among the groups.

Obese patients also may be poor candidates for classical open operations because of size, postoperative pulmonary complications and previous surgery. 6 • 7 • 9 • 10 It has been well documented that there is an increase in surgical morbidity and mortality rates associated with morbid obesity. 6 • 7 Prem and associates demonstrated a 20 per cent mortality rate in women weighing more than 300 pounds who underwent hysterectomy for endometrial cancer. 10 This mortality was compared to a 5.5 per cent rate in patients between 250 and 300 pounds, and a 1.5 per cent rate in most patients less than 250 pounds. While their series of patients was small the comparison of total mortality strongly suggested an increase in complications in patients with morbid obesity. Postlethwait and Johnson reported complications after duodenal ulcer surgery in 124 patients weighing at least 35 pounds over desirable weight and compared them to a control group of 2,676 nonobese patients. 9 Wound infections were significantly more prevalent in the obese population, and there was an increased incidence of atelectasis, thrombophlebitis and mortality, as well as pneumonia in the obese patients. While theoretical problems with anesthesia in these patients have been described, series in the literature examining anesthesia in obese pi!tients have failed to demonstrate statistically significant increases in morbidity in patients with morbid obesity. 6 Because of body size, however, epidural anesthesia may be more difficult in this patient population and general anesthesia may be a better choice in the morbidly obese patient undergoing percutaneous procedures. Of the reported series describing complications of surgery in obese patients the majority stressed the increased complications associated with wound infection in patients with morbid obesity. 7 • 9 Wound infection and dehiscence have been reported to be more common in patients with significant obesity. However, through the use of percutaneous procedures, wounds are small, infection is unlikely and dehiscence is eliminated. The obese patient often has abnormal respiratory, metabolic and circulatory functions, and he is at increased risk for postoperative complications from any type of su.•gical procedure. 6 • 7 The impact of these physiological abnormalities on the outcome of percutaneous and open operations is difficult to quantify because of the small series that have been reported. However, based on our series the risk of elective percutaneous stone extraction in massively obese patients is not higher than that for a control group undergoing the same procedure with similar stone size and stone distribution. Thus, there is no reason to deny percutaneous surgery to patients based on body weight alone. Patients denied access to ESWL fragmentation of calculi as a result of body size can be treated safely and successfully _,with percutaneous lithotripsy to remove renal calculi. REFERENCES

1. Dunnick, N., Carson, C. C., Moore, A. V., Jr., Ford, K., Miller, G. A., Braun, S. D., Newman, G. E. and Weinerth, J. L.: Percutaneous approach to nephrolithiasis. Amer. J. Roentgen., 144: 451, 1985. 2. Goldwasser, B., Weinerth, J. L., Carson, C. C. and Dunnick, N. R.: Factors affecting the success rate of percutaneous nephrolithotripsy and the incidence of retained fragments. J. Urol., 136: 358, 1986. 3. Carson, C. C., Moore, A. V., Weinerth, J. L., Ford, K. K. and Dunnick, N. R.: Percutaneous dissolution of renal calculi using ultrasonic litholapaxy. South. Med. J., 77: 196, 1984.

PERCUTANI~OU.S LITtIOTRIPSY fN rvIORBID OBESI'T'Y

W., Patterson, D. E., LeRoy, A. Williams, ff D. Benson, D, M., Benson, C., Jr., May, and Bender, E .. Percutaneous removal of kidney stones: review of 1,000 cases. J. UroL, 134: 1077, 1985. 5. Reddy, P. K, Hulbert, J. C., Lange, P. H., Clayman, R. V., Marcuzzi, A., Lapointe, S., Miller, R. P., Hunter, D. W., Castaneda-Zuniga, W. R. and Amplatz, K.: Percutaneous removal of renal and ureteral calculi: experience with 400 cases. J. UroL, 134: 662, 1985. 6. Pasulka, P. S., Bistrian, B. R., Benotti, P. N. and Blackburn, G. L.: The risks of surgery in obese patients. Ann. Intern. Med., 4.

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104: 540, 1986. 7. Strauss, R. J. and Wise, L.: Operative risks of obesity. Surg., Gynec. & Obst., 146: 286, 1978. 8. Metropolitan Height and Weight Tables, Metropolitan Life Insurance Co., New York, New York, 1985. 9. Postlethwait, R. W. and Johnson, W. D.: Complications following surgery for duodenal ulcer in obese patients. Arch. Surg., 105: 438, 1972. 10. Prem, K. A., Mensheha, N. and McKelvey, J. L.: Operative treatment of adenocarcinoma of the endometrium in obese woman. Amer. J. Obst. Gynec., 92: 16, 1965.