Abstract
Objective
To compare the effect of body mass index (BMI) on operative time, hospital stay, stone clearance, postoperative complications, and postoperative analgesic requirement in patients undergoing percutaneous nephrolithotomy (PCNL) by comparing three BMI groups.
Material and methods
This is a retrospective analysis of 129 patients who underwent PCNL from January 2010 to August 2013. All the patients underwent PCNL by a standard technique. The patients were divided into three groups: patients having a BMI ≤24 kg/m2 were included in the normal group, those having a BMI of 24.1–30.0 kg/m2 were included in the overweight group, and those having a BMI >30 kg/m2 were included in the obese group. Three groups were compared for operative time, hospital stay, stone clearance, postoperative complications, and postoperative analgesic requirement.
Results
A total of 129 patients including 44 females and 85 males were included with a mean age of 45.00±1.44 years. The mean age in the normal group was 43.29±1.69 years, 47.08±1.29 years in the overweight group, and 43.61±1.25 years in the obese group. The mean stone size in the normal group was 25.46±8.92 mm, 28.01±8.40 mm in the overweight group, and 26.84±7.41 mm in the obese group. Our results showed no statistically significant difference with respect to mean operative time, mean hospital stay, and stone clearance in the normal, obese, and overweight patients undergoing PCNL. Postoperative complications and analgesia requirement were also similar in all the three groups.
Conclusion
There was no effect of BMI on operative time, hospital stay, stone clearance, postoperative complications, and postoperative analgesic requirement in patients undergoing PCNL. PCNL is a safe and effective procedure for the removal of renal stones in obese patients.
Keywords: Body mass index, hospital stay, operative time, PCNL, postoperative analgesic requirement, stone clearance
Introduction
Renal stone disease is one of the most common urological disorders recognized since ancient times, with a prevalence of approximately 2–3% in the general population.[1] The estimated lifetime risk of developing a kidney stone is approximately 12%.[1] Pakistan is located in the stone belt region with a very high incidence of renal stones.[2] Renal stones were classically removed by open surgery, but the advent of minimally invasive, endoscopic techniques and extra-corporeal shock wave lithotripsy (ESWL) have almost replaced the classically performed open surgery for the removal of renal stones.[1] At present, percutaneous nephrolithotomy (PCNL) is accepted as the procedure of choice for renal stones larger than 2 cm.[3] Currently, open stone surgery is rare.[1] In the western community, an increasingly sedentary lifestyle and high-fat diet have resulted in obesity defined as the body weight more than 120% of the ideal body weight,[4] reaching a pandemic status.[5] In USA, approximately one-third (34.9%) of adults were obese in 2011–2012.[6] Obesity is common in the developing world, including Pakistan. There is an alarming rise in obesity; recent data suggests that more than 1 billion adults are overweight, and at least 300 million of them are clinically obese.[7] Obesity is known to be an independent risk factor for surgical and anesthetic complications.[5]. To date, there is no clear evidence as to how much body mass index (BMI) can affect the outcomes in PCNL. We have compared operative time, hospital stay, stone clearance, and postoperative complications in individuals undergoing PCNL by dividing them into normal, overweight, and obese individuals.
Material and methods
The study was conducted after the approval of the ethical committee of Shifa International Hospital. This is a retrospective analysis of 129 patients who underwent PCNL from January 2010 to August 2013. All the patients underwent PCNL by a standard technique. An open-end catheter was passed cystoscopically up to the renal pelvis in the lithotomy position under fluoroscopic guidance. The patient was then placed in the prone position. Under fluoroscopic guidance, the pelvicalyceal system (PCS) was punctured using a 23-Fr spinal needle. The glide wire was passed through the spinal needle into the PCS. The tract was dilated using metallic dilators over the glide wire. A 30-Fr amplatz sheath was introduced over metallic dilators into the PCS under fluoroscopic guidance. A 26 Fr nephroscope was then introduced through the PCNL sheath. A pneumatic lithoclast was used to break the stones, and a three prongs grasper was used to extract the stone fragments. A nephrostomy tube was passed in all patients and was removed on the second postoperative day.
The patients were divided into three groups: patients having a BMI ≤24 kg/m2 were included in the normal group, those having a BMI of 24.1–30.0 kg/m2 were included in the overweight group, and those having a BMI >30 kg/m2 were included in the obese group. All the groups were matched for age, gender, and stone size. Patients with uncontrolled diabetes, hypertension, bleeding disorders, or ischemic heart disease were excluded from the study. All patients received 1 g intravenous (IV) or oral paracetamol at 6-h intervals on the first postoperative day and thereafter on pro re nata (PRN)/as needed basis. Pain not getting relieved by paracetamol was resolved by administering IV Nalbuphine 0.2–0.4 mg/kg body weight with 12.5 mg of dimenhydrinate. All patients received 2 g cefoperazone plus sulbactam on induction and post surgery.
Three groups were compared for operative time, hospital stay, stone clearance, postoperative complications, and postoperative analgesic requirement. The operative time (in min) was calculated from the first attempt to puncture the PCS to the placement of the last stitch. Hospital stay (in days) was calculated from zero postoperative day to the day of discharge. Stone clearance was measured in terms of percentage of the primary stone removed using ultrasound, computed tomography (CT) scan, or a kidney, ureter, and bladder (KUB) X-ray, which was performed for initial diagnosis. The postoperative complications include bleeding requiring transfusion, respiratory tract infections (presence of cough, sputum, and fever with radiological evidence of chest infection on X-ray of the chest), sepsis (pulse more than 100, fever more than 38°C, respiratory rate more than 24, and total leukocyte count (TLC) more than 12000/mm3). Postoperative analgesic requirement was measured in terms of the mean number of doses of paracetamol and nalbuphine per patient during hospital stay.
Statistical analysis
The data was collected through chart review and entered on specified performa. Data was analyzed on the Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA) ver. 16.
Results
A total of 129 patients including 44 females and 85 males were included with a mean age of 45.00±1.44 years (Table 1). Forty-seven (36.4%) patients had a BMI of ≤24 kg/m2 and were included in the normal group, 56 (43.4%) had a BMI from 24 to 30 kg/m2 and were included in the overweight group, and 26 (20.2%) with a BMI >30 kg/m2 were included in the obese group. The mean age in the normal group was 43.29±1.69 years, 47.08±1.29 years in the overweight group, and 43.61±1.25 years in the obese group. The mean stone size in the normal group was 25.46±8.92 mm, 28.01±8.40 mm in the overweight group, and 26.84±7.41 mm in the obese group (Table 2). Detailed results are shown in Table 3.
Table 1.
Patient characteristics
| Total no. of patients (n) | 129 | |
| Males | 85 | 65.89% |
| Females | 44 | 34.1% |
| Mean age (years) | 45.00±1.44 | |
| BMI ≤24 kg/m2 (normal) | 47 | 36.4% |
| BMI 24.1–30 kg/m2 (overweight) | 56 | 43.4% |
| BMI >30 kg/m2 (obese) | 26 | 20.2% |
Table 2.
Comparison of three BMI groups with respect to demographic data
| BMI ≤24 kg/m2 (normal) |
BMI 24.1–30 kg/m2 (overweight) |
BMI >30 kg/m2 (obese) |
|
|---|---|---|---|
| No. of patients | 47 | 56 | 26 |
| Mean age (years) | 43.29±1.69 | 47.08±1.29 | 43.61±1.25 |
| Mean stone size (mm) | 25.46±8.92 | 28.01±8.40 | 26.84±7.41 |
Table 3.
Results of the patients
| Normal | Over weight | p | Normal | Obese | p | Over weight | Obese | p | |
|---|---|---|---|---|---|---|---|---|---|
| Mean operative time (min) | 128.40±48.61 | 126.62±59.75 | 0.8703 | 128.40±48.61 | 129.42±58.86 | 0.9368 | 126.62±59.75 | 129.42±58.86 | 0.9344 |
| Mean hospital stay (days) | 3.00±1.04 | 3.00±1.17 | 1.0000 | 3.00±1.04 | 3.03±1.82 | 0.9287 | 3.00±1.17 | 3.03±1.82 | 0.9286 |
| Stone clearance | 91.18±10.83 | 89.62±11.00 | 0.4720 | 91.18±10.83 | 90.23±11.89 | 0.7299 | 89.62±11.00 | 90.23±11.89 | 0.8204 |
| Sepsis | 1 | 1 | 0.9003 | 1 | 1 | 0.6667 | 1 | 1 | 0.5643 |
| Blood transfusions | nil | nil | nil | nil | nil | nil | |||
| RTIs | 2 | 4 | 0.8752 | 2 | 5 | 0.0957 | 4 | 5 | 0.2113 |
| Mean no of doses of paracetamol | 5.85±2.61 | 5.39±2.11 | 0.3250 | 5.85±2.61 | 6.61±5.11 | 0.4021 | 5.39±2.11 | 6.61±5.11 | 0.1288 |
| Mean no of doses nalbuphine | 2.27±1.58 | 2.55±1.76 | 0.3851 | 2.27±1.58 | 3.03±2.25 | 0.0961 | 2.55±1.76 | 3.03±2.25 | 0.2969 |
RTIS: respiratory tract infections
Mean operative time
There was no significant difference in the mean operative time in the three groups, i.e., normal versus overweight (128.40±48.61 vs. 126.62±59.75 min, p-value=0.8703), normal versus obese (128.40±48.61 vs. 129.42±58.86 min, p-value=0.9368), and overweight versus obese patients (126.62±59.75 vs. 129.42±58.86 min, p-value=0.9344).
Mean hospital stay
No significant difference in the mean hospital stay was observed in the three groups, i.e., normal versus overweight (3.00±1.04 vs. 3.00±1.17 day, p-value=1.000), normal versus obese (3.00±1.04 vs. 3.03±1.82, p-value=0.9287), and overweight versus obese patients (3.00±1.17 vs. 3.03±1.82, p-value=0.9286).
Stone clearance
Intraoperative stone clearance was almost equal in the three groups, i.e., normal versus overweight (91.18±10.83% vs. 89.62±11.00%, p-value=0.4720), normal versus obese (91.18±10.83% vs. 90.23±11.89%, p-value=0.7299), and overweight versus obese patients (89.62±11.00% vs. 90.23 ±11.89%, p-value=0.8204).
Post operative complication
There was no significant difference in postoperative complication in the three groups. No blood transfusion was performed in any group. One patient in each group developed urosepsis. Two patients in the normal group, four in the overweight group, and five in the obese group developed respiratory tract infection.
Postoperative analgesia requirement
There was no statistically significant difference with respect to postoperative analgesia requirement in the three groups.
Discussion
Obesity is known to be associated with poorer surgical outcomes and increased operative morbidity and mortality.[4] PCNL in obese patients poses the similar treatment challenge because they cannot easily tolerate the prone position, and the thicker subcutaneous fat renders the nephroscope too short, thus leading to operative difficulties, longer operative time, longer hospital stay, poorer stone clearance, and increased risk of postoperative complications.[5]
Sergeyev et al.[8] found a significantly longer length of hospital stay for the group with a BMI <25 kg/m2; however, there was no difference in the stone-free rate, postoperative fever, or change in hemoglobin in different BMI groups. To overcome the shorter length of sheath, Giblin et al.[9] employed larger and longer amplatz access sheaths and a 30-F gynecologic laparoscope. There was complete stone clearance and no additional perioperative morbidity. Bagrodia et al.[10] in USA and El-Assmy et al.[11] in Egypt also found no significant differences among groups with respect to stone-free and complication rates, operative time, length of hospital stay, or need for multiple accesses. Stone-free rate and complication rates were found to be independent of BMI by Tomaszewski et al.[12] and Pearle et al.[13]
On the other hand there are reports of longer operative time, poorer stone clearance, and increase risk of postoperative complications in obese patients undergoing PCNL. Faerber and Goh found a longer hospital stay (3.5 days vs. 4.4 days) and a higher rate of complications (16% vs. 37%) in the morbidly obese group than the normal weight group.[14] Fuller et al.[15] in a retrospective analysis of 5803 patients found a significantly longer operative time, an inferior stone-free rate, and a higher re-intervention rate; however, there was no difference with respect to the length of hospital stay or the transfusion rate and complication rates in obese patients.
Our results showed no statistically significant difference with respect to mean operative time, mean hospital stay, and stone clearance in normal obese and overweight patients undergoing PCNL. Postoperative complications and analgesia requirement were also similar in all the three groups. This is similar to most of the recently published literature. Older studies showed a poorer outcome; however, the improvement of instruments, experience, and better surgical techniques has made the procedure safe and effective for obese patients as well.
In conclusion, there was no effect of BMI on operative time, hospital stay, stone clearance, postoperative complications, and postoperative analgesic requirement in patients undergoing PCNL. PCNL is a safe and effective procedure for the removal of renal stones in overweight and obese patients.
Footnotes
Ethics Committee Approval: Ethics committee approval was obtained.
Informed Consent: Due to the retrospective nature of this study, informed consent was waived.
Peer-review: Externally peer-reviewed.
Author Contributions: Concept - D.S., R.A.; Design - D.S.; Supervision - S.A.; Data Collection and/or Processing - R.A., S.S., S.A., A.B.; Analysis and/or Interpretation - D.S., M.U.A.; Literature Review - D.S., R.A.; Writer - D.S.; Critical Review - S.A.
Conflict of Interest: The authors declared no conflict of interest.
Financial Disclosure: The authors declared that this study has received no financial support.
References
- 1.Gupta R, Gupta A, Singh G, Suri A, Mohan SK, Gupta CL. PCNL- -A comparative study in nonoperated and in previously operated (open nephrolithotomy/pyelolithotomy) patients a single surgeon experience. Int Braz J Urol. 2011;37:739–44. doi: 10.1590/s1677-55382011000600009. http://dx.doi.org/10.1590/S1677-55382011000600009. [DOI] [PubMed] [Google Scholar]
- 2.Jan H, Akbar I, Kamran H, Khan J. Frequency of renal stone disease in patients with urinary tract infection. J Ayub Med Coll Abbottabad. 2008;20:60–2. [PubMed] [Google Scholar]
- 3.Lim SH, Jeong BC, Seo SI, Jeon SS, Han DH. Treatment outcomes of retrograde intrarenal surgery for renal stones and predictive factors of stone-free. Korean J Urol. 2010;51:777–82. doi: 10.4111/kju.2010.51.11.777. http://dx.doi.org/10.4111/kju.2010.51.11.777. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Choban PS, Flancbaum L. The impact of obesity on surgical outcomes: a review. J Am Coll Surg. 1997;185:593–603. doi: 10.1016/s1072-7515(97)00109-9. http://dx.doi.org/10.1016/S1072-7515(97)00109-9. [DOI] [PubMed] [Google Scholar]
- 5.Alyami FA, Skinner TA, Norman RW. Impact of body mass index on clinical outcomes associated with percutaneous nephrolithotomy. Can Urol Assoc J. 2012;15:1–5. doi: 10.5489/cuaj.11229. http://dx.doi.org/10.5489/cuaj.11229. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Ogden CL, Carroll MD, Kit BK, Flegal KM. NCHS data brief No. 131. Hyattsville, MD: National Center for Health Statistics; 2013. Prevalence of obesity among adults: United States, 2011–2012. [PubMed] [Google Scholar]
- 7.Nur T, Shah U, Zehra N. Majority of the population disregards obesity as a health risk: obesity among different socioeconomic strata in karachi a hospital case study. Pakistan J Med Dent. 2013;2:43–8. [Google Scholar]
- 8.Sergeyev I, Koi PT, Jacobs SL, Godelman A, Hoenig DM. Outcome of percutaneous surgery stratified according to body mass index and kidney stone size. Surg Laparosc Endosc Percutan Tech. 2007;17:179–83. doi: 10.1097/SLE.0b013e318051543d. http://dx.doi.org/10.1097/SLE.0b013e318051543d. [DOI] [PubMed] [Google Scholar]
- 9.Giblin JG, Lossef S, Pahira JJ. A modification of standard percutaneous nephrolithotripsy technique for the morbidly obese patient. Urology. 1995;46:491–3. doi: 10.1016/S0090-4295(99)80260-X. http://dx.doi.org/10.1016/S0090-4295(99)80260-X. [DOI] [PubMed] [Google Scholar]
- 10.Bagrodia A, Gupta A, Raman JD, Bensalah K, Pearle MS, Lotan Y. Impact of body mass index on cost and clinical outcomes after percutaneous nephrostolithotomy. Urology. 2008;72:756–60. doi: 10.1016/j.urology.2008.06.054. http://dx.doi.org/10.1016/j.urology.2008.06.054. [DOI] [PubMed] [Google Scholar]
- 11.El-Assmy AM, Shokeir AA, El-Nahas AR, Shoma AM, Eraky I, El-Kenawy MR, El-Kappany HA. Outcome of percutaneous nephrolithotomy: effect of body mass index. Eur Urol. 2007;52:199–204. doi: 10.1016/j.eururo.2006.11.049. http://dx.doi.org/10.1016/j.eururo.2006.11.049. [DOI] [PubMed] [Google Scholar]
- 12.Tomaszewski JJ, Smaldone MC, Schuster T, Jackman SV, Averch TD. Outcomes of percutaneous nephrolithotomy stratified by body mass index. J Endourol. 2010;24:547–50. doi: 10.1089/end.2009.0431. http://dx.doi.org/10.1089/end.2009.0431. [DOI] [PubMed] [Google Scholar]
- 13.Pearle MS, Nakada SY, Womack JS, Kryger JV. Outcomes of contemporary percutaneous nephrostolithotomy in morbidly obese patients. J Urol. 1998;160:669–73. doi: 10.1016/S0022-5347(01)62750-2. http://dx.doi.org/10.1016/S0022-5347(01)62750-2. [DOI] [PubMed] [Google Scholar]
- 14.Faerber GJ, Goh M. Percutaneous nephrolithotripsy in the morbidly obese patient. Tech Urol. 1997;3:89–95. [PubMed] [Google Scholar]
- 15.Fuller A, Razvi H, Denstedt JD, Nott L, Pearle M, Cauda F, et al. The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome. J Urol. 2012;188:138–44. doi: 10.1016/j.juro.2012.03.013. http://dx.doi.org/10.1016/j.juro.2012.03.013. [DOI] [PubMed] [Google Scholar]