Totally Ultrasound-Guided Percutaneous Nephrolithotomy: How to Improve Success in Patients with Obesity

Abstract

Introduction:

Percutaneous nephrolithotomy (PCNL) is the treatment of choice for kidney stones greater than 2 cm. ¹ This procedure in patients with obesity is challenging because obesity is a risk factor for complex access and requires more experience to achieve a successful puncture. ^{2 –5} In this video, we demonstrate our technique for totally ultrasound-guided PCNL with two-step tract dilation, our experience, and provide guidance on improving success rates in patients with obesity.

Materials and Methods:

Surgical technique: With the patient in the supine position, we mobilized fatty tissue; after a proper ultrasound configuration, percutaneous access with a longitudinal freehand technique was obtained. Dilation with a two-step technique ⁶ Step 1: Creation of a minitract 14Fr to perform antegrade nephroscopy to check the renal cavities and measure the length of the tract; a pair of guides are placed in the ureter, one for definitive dilatation and the other as a safety guide. Step 2: Definitive tract 26Fr, insert the Amplatz dilator 1 cm in addition to the previously measured length of the tract to avoid a short dilation and advance the sheath. Pneumatic fragmentation is performed. Finally, a JJ stent was placed. Case series: Retrospective review of 54 patients treated with totally ultrasound-guided PCNL from July 2021 to June 2023, and we divided the cases according to their BMI: Group 1 included 27 patients with a BMI ≥30 kg/m2 and Group 2 included 27 patients with a normal BMI.

Results:

Mean age was 46.9 years. The BMI was 36.3 kg/m² (±5.9) and 21.7 kg/m² (±2.4) (p = <0.001), respectively. In Group 1, 57% of our patients had Guy’s 3, and 15% had Guy’s 4; 72% of the cases had complex stones. The stone burden was 10,976.43 mm³ (±11,287.6) and 7,543.0 mm³ (±10,203.6) (p = 0.056), with a mean of 12 cm and 8 cm of tract length (p < 0.001), respectively (Table 1). In the obesity group, the short dilation was more frequent, 63% vs. 26% (p = 0.013). The stone-free rate was 77.8% in both groups (p = 1.000), and we found that the stone burden had a more significant effect on the stone-free rate than the BMI (Fig. 1). In Group 1, the complications were 3 (11.1%); 2 patients had fever (Clavien I), and 1 needed a blood transfusion due to anemia (Clavien II), whereas in Group 2 there were 6 (22.2%); 4 had fever (Clavien I), and 2 had urosepsis (Clavien IV) (p = 0.019).

FIG. 1.

Relation between stone volume (mm³) and body mass index (Kg/m²) in stone-free status: In blue, the patients with stone-free status, and in red, the patients with residual stone.

Table 1.

Preoperative and Postoperative Descriptive Data by Group according to BMI

	Total	Group 1: BMI (≥30 kg/m2)	Group 2: BMI (≤25 kg/m2)	p Value
Number of patients	54	27	27
Age, years	48.4 (±11.9)	49.9 (±11.1)	46.9 (±12.7)	0.36
Gender: n (%)
Male	18 (33.3)	9 (33.3)	9 (33.3)	0.613
Female	36 (66.7)	18 (66.7)	18 (66.7)
BMI (kg/m2)	29.06 (±27.7)	36.3 (±5.9)	21.7 (±2.4)	<0.001
Previous Procedure: n (%)
None	34 (62.9)	18 (66.7)	16 (59.3)	0.976
SWL	2 (3.7)	1 (3.7)	1 (3.7)
Ureteral Stent	10 (18.5)	5 (18.5)	5 (18.5)
Flexible Ureteroscopy	2 (3.7)	1 (3.7)	1 (3.7)
PCNL	5 (9.2)	2 (7.4)	3 (11.1)
Open Surgery	1 (1.8)	0	1 (3.7)
Guy Stone: n (%)
Guy 1	11 (20.3)	4 (14.8)	7 (25.9)	0.047
Guy 2	11 (20.3)	4 (14.8)	7 (25.9)
Guy 3	20 (37)	15 (56.6)	5 (18.5)
Guy 4	12 (22.2)	4 (14.8)	8 (29.6)
Skin-stone distance (cm)	9.8 (±2.5)	11.7 (±2.0)	8.0 (±1.1)	<0.001
Stone burden (mm3)	9259.75 (±10797.2)	10976.43 (±11287.6)	7543.0 (±10203.6)	0.056
Hydronephrosis, n (%)
None	34 (62.9)	19 (70.4)	15 (55.5)	0.494
Mild	10 (18.5)	3 (11.1)	7 (25.9)
Moderate	10 (18.5)	5 (18.5)	5 (18.5)
Tract number: n (%)
One tract: 26Fr	44 (81.4)	22 (81.5)	22 (81.5)	1.000
Two tracts: 26Fr	9 (16.6)	5 (18.5)	4 (14.8)
Three tracts: 26Fr	1 (1.85)	0 (0)	1 (3.7)
Tract loss, n (%)
Yes	4 (7.4)	2 (7.4)	2 (7.4)	1.000
No	50 (92.6)	25 (92.6)	25 (92.6)
Short dilation, n (%)
Yes	24 (44.4)	17 (63)	7 (25.9)	0.013
No	30 (55.4)	10 (37)	20 (74.1)
Complications, Clavien– Dindo, n (%)
Grade 1	6 (11.1)	2 (7.4)	4 (14.8)	0.019
Grade 2	1 (1.8)	1 (3.7)	0
Grade 3	0	0	0
Grade 4	2 (3.7)	0	2 (7.4)
Hemoglobin drop (g/dL)	1.57 (±1.63)	1.62 (±1.71)	1.52 (±1.57)	0.986
Operative time (min)	137.4 (±60.7)	141.6 (±54.6)	133.1 (±67.0)	0.314
Stone free status, n (%)	42 (77.8)	21 (77.8)	21 (77.8)	1.000

p Value of t tests to compare means and Fisher’s exact test p value.

Conclusion:

A proper ultrasound configuration and adipose tissue mobilization increase success in obese patients. This technique offers a good stone-free rate and a safety profile without radiation.

Rutime of video: 7 min 25 sec.

No competing financial interests exist.

Informed consent was obtained to film portions of the procedure from the patient who appeared in this video.