In Obese Patients, the Distance Between Skin and Renal Collecting System Changes with the Position of the Patient from Supine to Prone

Effect of Body Mass Index on Outcomes of Percutaneous Nephrolithotomy: A Systematic Review and Meta-Analysis

Objective

The current study aimed to assess the efficacy and safety of percutaneous nephrolithotomy (PCNL) in obese and overweight individuals based on body mass index (BMI).

Methods

We electronically explored the databases of PubMed, CENTRAL, ScienceDirect, Embase, and Google Scholar databases for all types of comparative studies investigating the role of BMI on PCNL outcomes. Only studies defining obesity as >30 kg/m² were included. Efficacy outcomes were stone-free rates and operating time while safety outcomes were complications and length of hospital stay (LOS).

Results

Eighteen studies with 101,363 patients were included. We noted no difference in the stone-free rates after PCNL for morbid obese vs normal BMI patients (OR: 0.78 95% CI, 0.57, 1.08 I²= 7% p = 0.13), overweight vs normal (OR: 1.01 95% CI, 0.89, 1.15 I²= 1% p = 0.83) and obese vs normal patients (OR: 1.00 95% CI, 0.87, 1.16 I²= 0% p = 0.95). PCNL operative time was significantly increased in morbid obese (MD: 9.36 95% CI, 2.85, 15.88 I²= 76% p = 0.005) and obese patients as compared with normal patients (MD: 2.15 95% CI, 1.20, 3.10 I²= 0% p < 0.00001), but not for overweight patients. There was no difference in the odds of complications between morbid obese vs normal (OR: 1.26 95% CI, 0.93, 1.72 I²= 0% p = 0.13), overweight vs normal (OR: 1.11 95% CI, 0.96, 1.28 I²= 0% p = 0.15), and obese vs normal patients (OR: 1.07 95% CI, 0.91, 1.27 I²= 0% p = 0.40). LOS was significantly reduced in obese patients (MD: −0.12 95% CI, −0.20, −0.04 I²= 0% p = 0.004) as compared to normal patients, but not for morbid obese or overweight patients.

Conclusion

PCNL has similar efficacy and safety in morbidly obese, obese, and overweight patients as compared to normal BMI patients with no difference in the stone-free and complication rates. Evidence suggests that operating time is increased in morbidly obese and obese patients and the latter may have shorter LOS.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, identifier: CRD42022313599.

Renal Displacement with Supine to Prone Positional Change: Effect of Sex and BMI

OBJECTIVE

To determine patterns of kidney and retroperitoneal organ movement during positional change between the supine and prone positions as seen on computed tomography (CT) scans.

METHODS

Axial CT scans of 75 subjects who underwent supine and prone were retrospectively analyzed. A total of 1650 measurements were taken for anterior-posterior, medial-lateral, cranial-caudal, skin-to-calyx distance, kidney-to-liver distance, and kidney-to-colon distance in both positions.

RESULTS

Pronation shortens the distance from the skin to renal calyx for both the right (99.62 mm vs. 85.14 mm; p < 0.00001) and left (96.67 mm vs. 90.80 mm; p < 0.00001) sides. The reduction in left-side tract length for obese patients is significantly greater than that of normal weight patients (11.88 mm vs. -5.02 mm; p = 0.001). The left kidney displaces ventrally (11.12 mm vs. 18.59 mm; p < 0.00001) while the right kidney does not (14.26 mm vs. 15.30 mm; p = 0.30). The right kidney displaces cranially (62.76 mm vs. 79.51 mm; p < 0.00001) while the left kidney does not (64.35 mm vs. 66.52 mm; p = 0.14). The left kidney in females moves medially while no change is seen in males (4.22 mm vs. -0.48 mm; p = 0.0004). The left kidney in females displaces towards the descending colon while it moves farther away in males (2.73 mm vs. -2.01 mm; p = 0.011).

CONCLUSIONS

Both sex and BMI had effects on the movement of the kidneys upon pronation. The differences can be clinically useful to help pre and intraoperative planning.