Invest Clin 63(1): 70 - 80, 2022 https://doi.org/10.54817/IC.v63n1a06

Corresponding Author: Xing Ai, Department of Urologic Surgery, The Third Medical Center, Chinese PLA (People’s

Liberation Army) General Hospital, No. 5 Nanmencang, Dongcheng District, Beijing, China. Tel: +86010-84008022;

Email: aixing0007@163.com

Efficacy of ultra-mini percutaneous

nephrolithotomy and retrograde intrarenal

surgery in the treatment of 2-3 cm lower

calyceal stones.

Ya-Wei Guan, Xing Ai, Zhi-Hui Li, Guo-Hui Zhang, Zhuo-Min Jia and Jing-Fei Teng

Department of Urologic Surgery, The Third Medical Center, Chinese PLA

(People’s Liberation Army) General Hospital, Beijing, China.

Key words: ultra-mini percutaneous nephrolithotomy; retrograde intrarenal surgery;

kidney stone; efficacy.

Abstract. We aimed to compare the efficacy and safety of ultra-mini per-

cutaneous nephrolithotomy (UMP) and retrograde intrarenal surgery (RIRS)

for the management of lower calyceal stones. A group of 136 patients with a

single lower calyceal stone (2-3 cm in diameter) was divided into the UMP or

RIRS groups. The average operation time in the RIRS group was significantly

longer than that in the UMP group, and the intraoperative blood loss in the

former was markedly less than that in the latter. Besides, in the RIRS group,

the decreased value of postoperative Hb was obviously lower, the postoperative

hospital stay was evidently shorter, and the total hospitalization expenses were

markedly less than those in UMP group were. Moreover, the success rate of the

first-stage lithotripsy in the UMP group was notably higher than that in RIRS

group. The RIRS group had an obviously lower VAS score but a markedly higher

BCS score than the UMP group six hours after surgery. At 24 h after operation,

the levels of serum CRP, TNF-α and IL-6 in patients in both groups were remark-

ably increased, and they were evidently lower in the RIRS group than those in

the UMP group were. Three days after surgery, the levels of serum CRP, TNF-α

and IL-6 were notably lower in the UMP group than those in RIRS group were.

RIRS and UMP are safe and effective in the treatment of 2-3 cm lower calyceal

stones. The first-stage UMP is characterized by a high stone-free rate (SFR),

short operation time and low postoperative infection risk, while RIRS is associ-

ated with less blood loss and low total expenses.

UMP and RIRS in lower calyceal stones 71

Vol. 63(1): 70 - 80, 2022

INTRODUCTION

Urinary calculi are widely prevalent

worldwide. The incidence rate of urinary

calculus in North America, Europe and Asia

is 7~13%, 5~9% and 1~5% respectively. In

southern China, the incidence rate of renal

calculus can reach 28%, which is the most

common urinary disease in young adults.

About 83.2% of renal calculus present in

21~50 years-old-people. The lower calyx

stone is a common type of kidney stone, ac-

counting for 36% of those 1,2. Percutaneous

nephrolithotomy (PCNL) and retrograde

nephrolithotomy (RIRS) are the main surgi-

cal methods for treatment of lower calyceal

calculi. Although the stone-free rate (SFR)

of standard channel and microchannel PCNL

Eficacia de la nefrolitotomía percutánea ultramini y la cirugía

intrarrenal retrógrada en el tratamiento de cálculos caliceales

inferiores de 2-3 cm.

Invest Clin 2022; 63 (1): 70 – 80

Palabras clave: ultra-mini nefrolitotomía percutánea; cirugía intrarrenal retrógrada;

cálculo renal; eficacia.

Resumen. Nuestro objetivo fue comparar la eficacia y seguridad de la ne-

frolitotomía percutánea ultramini (UMP) y la cirugía intrarrenal retrógrada

(CRIR) en el manejo quirúrgico de los cálculos caliceales inferiores. Un grupo

de 136 pacientes con un solo cálculo calicial inferior (2-3 cm de diámetro) se

dividió en un grupo UMP o un grupo CRIR. El tiempo de operación promedio

en el grupo CRIR fue significativamente más largo que en el grupo UMP, y

la pérdida de sangre intraoperatoria en el primero fue marcadamente menor

que en el segundo. Además, en el grupo CRIR, el valor disminuido de la Hb

postoperatoria fue obviamente menor, la estancia hospitalaria postoperatoria

fue evidentemente más corta y los gastos totales de hospitalización fueron no-

tablemente menores que los del grupo UMP. Además, la tasa de éxito de la

litotricia de primera etapa en el grupo UMP fue notablemente más alta que en

el grupo CRIR. El grupo CRIR tuvo una puntuación VAS obviamente más baja

pero una puntuación BCS marcadamente más alta que el grupo UMP a seos

horas después de la operación. A las 24 h después de la operación, los niveles

séricos de PCR, TNF-α e IL-6 en los pacientes de ambos grupos aumentaron

notablemente y fueron evidentemente más bajos en el grupo CRIR que en el

grupo UMP. Tres días después de la operación, los niveles séricos de PCR, TNF-α e

IL-6 fueron notablemente más bajos en el grupo UMP que en el grupo CRIR.

Los procedimientos CRIR y el UMP son seguros y eficaces en el tratamiento de

cálculos caliciales inferiores de 2-3 cm. El UMP de primera etapa se caracteriza

por tener una tasa libre de cálculo (SFR) alta, un tiempo de operación corto

y un riesgo de infección posoperatorio bajo, y el RIRS se caracteriza por una

menor pérdida de sangre y gastos totales bajos.

Received: 07-05-2021 Accepted: 22-09-2021

72 Guan et al.

Investigación Clínica 63(1): 2022

is high, the trauma caused by PCNL is ob-

viously greater than that caused by RIRS 3.

RIRS is considered to be the gold standard

for the treatment of lower calyceal stones,

but it has been discovered in clinical appli-

cation that because of the bending angle,

lower calyceal stones are often in the blind

area of vision and cannot be taken out. Fur-

thermore, as the supporting lithotripsy tool

is only 200 μm holmium laser and the ure-

ter is thin, the lithotripsy efficiency is low,

the stone-free rate is low, and the opera-

tion time is long 4,5. Ultra-mini percutane-

ous nephrolithotomy (UMP) causes smaller

traumas compared with traditional standard

channel and microchannel PCNL (mPCNL),

and UMP has a higher lithotripsy efficiency,

a higher stone-free rate, and more advantag-

es in treating 1-2 cm stones than the RIRS,

so increasingly more attention is being paid

to UMP 6-8. However, there remains a contro-

versy over surgical methods for 2-3 cm lower

calyceal stones.

In this study, the efficacy and safety of

RIRS and UMP in the treatment of 2-3 cm

lower calyceal stones were compared, so as

to provide a strong basis for the surgical

methods for 2-3 cm lower calyceal stones.

MATERIALS AND METHODS

Research objects

Methods: The clinical data of 136 pa-

tients with a single lower calyceal stone (2-3

cm in diameter) were collected. These pa-

tients were admitted to our hospital from

March 2018 to December 2019, and had

indications for RIRS and UMP treatment.

According to the random number table

method, the patients were randomly divided

into two groups, 68 patients in each group

were treated with UMP and RIRS, respec-

tively. The inclusion criteria included: (1)

patients aged 18-71 years old; (2) the di-

ameter of lower calyceal calculi was 2-3cm;

(3) those with no fever or pyuria before op-

eration; (4) those with Visual Analog Scale

(VAS) pain score ≤3 points; (5) those with

stable blood pressure and blood glucose; (6)

those whose examination results of bleeding

time and coagulation time were normal af-

ter they stopped oral anticoagulants such as

aspirin or warfarin for two weeks; (7) those

with no congenital malformations or urinary

obstructions that need to be treated with an

emergency operation. The exclusion crite-

ria were as follows: (1) patients with lower

calyceal stones <2 cm or >3 cm, (2) those

complicated with stones in the renal pel-

vis, middle and upper renal calyx, ureter or

other parts, (3) those with severe hydrone-

phrosis, (4) those complicated with severe

abnormal heart, liver or kidney functions, or

(5) those with severe coagulation disorder

or bleeding tendency. Among the 136 pa-

tients, there were 88 males and 48 females

aged 35-77 years old, with an average age of

52.68±9.49 years old. No statistically sig-

nificant differences were found in the base-

line data between the two groups, which

were comparable (Table 1, p>0.05). All the

subjects signed an informed consent in ac-

cordance with the Helsinki Declaration. This

study was approved by the Ethics Committee

of the Chinese PLA General Hospital.

Treatment methods

RIRS: Before operation, a F6 double

J stent was used routinely for two weeks.

Then, the patient was placed in lithotomy

position under general anesthesia, and the

double-J tube was removed under rigid ure-

teroscope. Guided by a zebra guide wire, it

was observed whether there was distortion,

stenosis or calculus of the ureter in the re-

nal pelvis under the ureteroscope. Later, the

zebra guide wire was indwelt and the rigid

ureteroscope was removed. Next, a soft ure-

teroscope sheath was placed along the zebra

guide wire, and a soft ureteroscope was in-

serted along the sheath, which was pushed

up to the ureteropelvic junction to enter the

renal pelvis. First, the upper calyx and the

middle and lower calyces of the kidney were

observed in succession. After the stones

UMP and RIRS in lower calyceal stones 73

Vol. 63(1): 70 - 80, 2022

were found, the scope was retreated into the

sheath, and a 200 μm holmium laser fiber

was inserted to powder the stones from the

periphery to the center in the “worm-eaten”

form with 8-15 W power. Then the larger

stones were taken out through a stone-tak-

ing basket, and careful checking was per-

formed to ensure that there was no residual

stones ≥3 mm. Besides, the zebra guide wire

was indwelt, and the F6 double-J stent cath-

eter was placed under the guidance of the

guide wire.

UMP: Under general anesthesia, the

patients were firstly placed in the lithotomy

position. Next, a F5 ureteral catheter was

retrogradely indwelt under a cystoscope to

establish an artificial hydronephrosis by con-

tinuous water injection at the tail end. Then

the patients were placed in the prone posi-

tion, and a 16G puncture needle was utilized

to puncture the target renal calyx under the

location of color Doppler ultrasound. The

smooth outflow of urine indicated a success-

ful puncture. Subsequently, a J stent metal

guide wire at the head end was indwelt, and

it was observed from a color Doppler ultra-

sound that the tail end of the wire reached

the kidney collecting system. Later, a 4 mm

incision was made on the skin at the punc-

ture site, and the channel was dilated using

F10 and F14 fascia dilators in turn along

the guide wire. After that, the F13 UMP

Table 1

Demographics and general clinical data of all studied patients.

Parameters RIRS group

n=68

UMP group

n=68 p-value

Gender (Male/Female) 41/27 47/21 0.370

Age (years) 51.41±9.35 53.03±9.68 0.323

BMI (kg/m2) 23.25±3.54 23.79±3.29 0.359

Stone location 0.732

Left kidney 32 (47.1%) 35 (51.5%)

Right kidney 36 (52.9%) 33 (48.5%)

Stone diameter (cm) 2.60±1.61 2.51±1.47 0.734

Degree of hydronephrosis 0.500

Mild 58 (85.3%) 54 (79.4%)

Moderate 10 (14.7%) 14 (20.6%)

Preoperative use of double J tube 12 (17.6%) 6 (8.8%) 0.310

Stone CT value (Hu) 823.65±646.72 983.39±704.73 0.171

Systemic disease

Hypertension 15 (22.1%) 18 (26.5%) 0.690

Coronary heart disease 4 (5.9%) 7 (10.3%) 0.531

Diabetes mellitus 9 (13.2%) 6 (8.8%) 0.585

Notes: RIRS: Retrograde intrarenal surgery; UMP: Ultra-mini percutaneous nephrolithotomy; BMI: Body Mass Index.

74 Guan et al.

Investigación Clínica 63(1): 2022

sheath was pushed along the guide wire, and

the UMP nephroscope was inserted to ob-

serve the renal collecting system and look

for stones. Thereafter, lithotripsy was car-

ried out using a 200 μm holmium laser un-

der the lithotripsy power of 10-20 w, during

which stones were broken into fragments <3

mm. After flushing in the ureteral catheter

combined with the inner wall of the outer

sheath, the stone fragments were washed

out using the endoscope sheath through the

vortex formed at the head end of the endo-

scope. At the end of lithotripsy, nephrostomy

fistula and double-J stent catheters were not

indwelt.

Observational indicators

The operation time, intraoperative

blood loss, postoperative hospital stay, to-

tal hospitalization expenses, incidence rate

of postoperative complications and other

indicators were compared between the two

groups of patients. Hemoglobin (Hb) was de-

termined one day before and one day after

operation, and the decreased value of Hb was

evaluated by comparing the preoperative and

the postoperative Hb levels. The pain of pa-

tients was evaluated using the VAS scale (0-

10 points), in which 0 point = no pain at all,

1-3 points = tolerable slight pain, and for

those with ≥4 points, pethidine hydrochlo-

ride (1 mg/kg) was intramuscularly injected

for analgesia at an interval of more than four

hours. The complications of patients were

recorded according to the modified Clavien

classification system. In the meantime, the

Bruggrmann comfort scale (BCS) was also

recorded. Five ml fasting venous blood was

collected before operation, 24 hours after

operation and three days after operation.

The serum levels of CRP, IL-6 and TNF in the

two groups were compared and analyzed by

ELISA.

The early postoperative lithotripsy and

the SFR were evaluated based on the kidney

ureter bladder (KUB) on the first day after

operation. According to the diameter of re-

sidual stones, the next treatment plan was

decided. Physical vibration lithotripsy was

used to treat residual stones whose diam-

eter was 4 mm; the patients with residual

stone diameter ≥ 5mm were treated with

extracorporeal shock ultrasonic lithotripsy.

Double-J catheters were taken out 2-4 weeks

after operation. In the follow-up, renal CT

plain scan was performed to re-evaluate the

SFR 3-4 weeks after operation. Standards for

stone-free state were as follows: There was

no residual stone or the diameter of the re-

sidual stone was ≤2 mm, and the stone was

asymptomatic, non-obstructive and non-in-

fectious 9.

Statistical methods

SPSS 22.0 was adopted for statistical

analysis. Measurement data were expressed

as mean ± standard deviation (x±s). Inter-

group comparisons and pairwise intragroup

comparisons were conducted by the t test.

Count data were expressed as percentage

(%) and compared using the χ2 test or Fish-

er’s Exact Test. p<0.05 represented that the

difference was statistically significant.

RESULTS

Operation of the two groups of patients

The average operation time in RIRS

group was significantly longer than that in

UMP group [(50.4±9.8) min vs. (42.4±8.3)

min, p<0.001], and the intraoperative blood

loss in the former was markedly less than that

in the latter [(7.2±2.7) mL vs. (17.5±4.6)

mL, p<0.001]. Besides, in RIRS group,

the decreased value of postoperative Hb

[(5.0±3.4) g/L vs. (7.9±3.7) g/L, p=0.003]

was obviously lower, the postoperative hospi-

tal stay [(2.6±1.4) days vs. (3.8±1.6) days,

p=0.006] was evidently shorter, and the total

hospitalization expenses [(17,300±1,300)

Yuan vs. (24,700±1,800) Yuan, p<0.001]

were notably less than those in UMP group.

Moreover, the success rate of the first-stage

lithotripsy in UMP group [94.1% (64/68)]

was higher than that in RIRS group [77.9%

UMP and RIRS in lower calyceal stones 75

Vol. 63(1): 70 - 80, 2022

(53/68)], showing a statistically significant

difference (p=0.012).

The RIRS group had an obviously low-

er VAS pain score [(2.8±0.8) points vs.

(4.6±1.1) points, p=0.011] but a mark-

edly higher BCS score [(2.5±0.8) points vs.

(1.8±0.7) points, p=0.026] than the UMP

group 6 h after operation. However, there

were no statistically significant differences

in VAS score [(1.5±0.7) points vs. (1.9±0.7)

points, p=0.258] and BCS score [(3.4±0.6)

points vs. (2.9±0.5) points, p=0.317)] at

24 h after operation between the two groups

of patients (p>0.317) (Table 2).

Incidence rate of related surgical

complications of the two groups

of patients

The incidence rate of the complications

of patients was recorded according to the

modified Clavien complication classification

system. No complications of grade 3 or above

occurred in both groups, and there were no

patients needing blood transfusion due to

massive hemorrhage or sharp decrease in Hb

in the two groups. Six patients in RIRS group

and four patients in UMP group had fever, with

the body temperature of <38.5°C and blood

routine showed only a slight increase in white

blood cell count, and no bacteria were de-

tected in blood and urine culture. The patient

only received physical cooling treatment.

Fourteen patients in the RIRS group and 19

patients in the UMP group had postoperative

pain with the VAS score >6 points, and they

were treated with analgesic drugs. Besides,

nausea and discomfort occurred in three

patients and one patient in the two groups,

respectively, and they underwent treatment

with antiemetic drugs. There were two pa-

tients and cero patient had low serum sodium

in the two groups, respectively, and they were

supplemented with sodium. Moreover, the

urinary tract infection rate of the UMP group

was significantly lower than that of the RIRS

group (P<0.05). The examinations showed

that the two patients with urinary tract infec-

tion in the UMP group had blood leukocytes

>10×109/L and urine leukocytes >90/μL.

After the application of antibacterial drugs

Table 2

Comparison of surgery parameters and postoperative vas, bcs scores of patients

in the two studied groups.

Parameters RIRS group

n=68

UMP group

n=68

p-value

Operation time (min) 50.4±9.8 42.4±8.3 0.001

Blood loss (mL) 7.2±2.7 17.5±4.6 0.001

Postoperative Hb decrease (g/L) 5.0±3.4 7.9±3.7 0.003

Postoperative hospital stay time (day) 2.6±1.4 3.8±1.6 0.006

Hospitalization expenses (ten thousands yuan) 1.73±0.13 2.47±0.18 0.001

VAS score (points)

6 h postoperative 2.8±0.8 4.6±1.1 0.011

24 h postoperative 1.5±0.7 1.9±0.7 0.258

BCS score (points)

6 h postoperative 2.5±0.8 1.8±0.7 0.026

24 h postoperative 3.4±0.6 2.9±0.5 0.317

Notes: RIRS: Retrograde intrarenal surgery; UMP: Ultra-mini percutaneous nephrolithotomy; VAS: Visual analogue

scale; BCS: Bruggrmann comfort scale.

76 Guan et al.

Investigación Clínica 63(1): 2022

for three days, the blood and urine routine

returned to normal in reexaminations. In ad-

dition, there were three patients and one pa-

tient suffered from hypertension in the RIRS

and UMP groups, respectively, and they took

oral nicardipine tablets. All complications

returned to normal after symptomatic treat-

ment. No complications such as impairment

of renal function, serious urinary system inju-

ry and urinary sepsis occurred in any patient

after operation. There was significant differ-

ence in the incidence of urinary tract infec-

tion between the two groups(p<0.05), and

there was no significant difference in the risk

of fever, pain, nausea and vomiting, electro-

lyte disorder, hypertension, blood transfusion

and complications above grade 3 (p>0.05).

(Table 3).

Expression levels of serum inflammatory

factors in patients before and after

treatment

Immediately before operation, there

were no statistically significant differences

in the levels of serum C-reactive protein

(CRP), tumor necrosis factor-alpha (TNF-α)

and interleukin-6 (IL-6) between the two

groups (p>0.05). At 24 h after operation,

the levels of serum CRP, TNF-α and IL-6 in

the two groups of patients were remarkably

increased, and they were evidently lower

in RIRS group than those in UMP group

(p<0.001). At 3 days after operation, the

levels of serum CRP, TNF-α and IL-6 in the

two groups of patients remarkably declined

compared with those at one day after opera-

tion, and they were notably lower in UMP

group than those in RIRS group (p<0.05)

(Table 4).

Postoperative follow-up results of patients

In the UMP group, KUB was reexamined

on the first day after operation, and it was

found that the diameter of residual stones

was ≤4 mm in four cases, and physical vibra-

tion lithotripsy was given one week after op-

eration. On the first day after operation, the

KUB showed that 15 patients had residual

stones, and two patients had residual stones

≥5 mm in diameter in RIRS group. On the

third day after operation, they were given

extracorporeal shock wave lithotripsy as an

auxiliary treatment combined with stone re-

moval using the lithotripter. In RIRS group,

there were 11 cases of small residual stones

(stone diameter ≤4 mm) after operation, all

of which were treated by physical vibration

in vitro. No UMP or RIRS treatment were

Table 3

Comparison of postoperative complications of patients in the two studied groups.

Parameters RIRS group

n=68

UMP group

n=68

p-value

Clavien grade 1

Fever, >38.5°C 6 (8.8%) 4 (5.9%) 0.744

Pain, VAS score>6 points 14 (20.6%) 19 (27.9%) 0.424

Nausea / vomiting 3 (4.4%) 1 (1.5%) 0.619

Transient electrolyte disturbance 2 (2.9%) 0 (0%) 0.496

Clavien grade 2

Hypertension 3 (4.4%) 1 (1.5%) 0.619

Urinary system infection 13 (19.1%) 2 (2.9%) 0.003

Blood transfusion 0 (0%) 0 (0%) 1.000

Clavien grade 3 0 (0%) 0 (0%) 1.000

Notes: RIRS: Retrograde intrarenal surgery; UMP: Ultra-mini percutaneous nephrolithotomy.

UMP and RIRS in lower calyceal stones 77

Vol. 63(1): 70 - 80, 2022

performed in both groups. At 3-4 weeks af-

ter operation, renal CT was applied for re-

examinations to evaluate the SFR, which

was 97.1% (66/68) in UMP group and 91.2%

(62/68) in RIRS group, with no statistically

significant difference (p=0.274).

DISCUSSION

Kidney stones are the most common

type of urinary calculi, and 36% of them

are lower calyceal stones 10. Lower calyceal

stones are often surgically treated, and RIRS

and PCNL are the main surgical methods at

present. Through PCNL, SFR can reach more

than 90%, so it has become the first choice to

treat kidney stones with a diameter greater

than 2 cm 11. However, PCNL will inevitably

damage renal parenchyma and surrounding

tissue structures, and easily lead to serious

complications 12. The traditional standard

PCNL puncture channel is F22-26, the mi-

crochannel percutaneous nephrolithotomy

(mPCNL) puncture channel is generally

F16-20, and the UMP puncture channel is

only F12-14, so the trauma caused by UMP is

smaller, with less blood loss and faster post-

operative recovery. However, UMP requires

higher precision of puncture and expansion.

In addition, UMP is generally only suitable

for 1-2 cm medium stones because of the

thinner channel, and as the stones in the up-

per ureter, upper calyx and middle calyx can

be treated by RIRS, UPM is the most suitable

for treating 1-2 cm lower calyceal stones,

and the lower calyx is the least accessible

part in RIRS 13, 14.

However, it is difficult to treat lower caly-

ceal stones with a diameter greater than 2 cm.

Studies in other countries have shown that

ureteroscopic holmium laser lithotripsy can

achieve the same SFR as mPCNL with a low in-

cidence rate of complications in the treatment

of kidney stones with a diameter greater than 2

cm 15. Aboumarzouk et al. 16 used ureteroscopy

to treat lower calyceal stones with an average

diameter of 3 cm. The SFR in the first stage

was 75%, while that in the second stage was

nearly 90%. Koyuncu et al. 17 used ureteroscopy

and percutaneous nephroscopy to treat lower

Table 4

Comparison of inflammatory factors of patients in the two studied groups.

RIRS group

n=68

UMP group

n=68 p-value

CRP (mg/L)

Immediate postoperative 4.21 ± 1.57 4.11 ± 1.33 0.689

1 day postoperative 25.68 ± 4.59 18.52 ± 5.28 0.001

3 days postoperative 19.83 ± 2.42 15.61 ± 2.74 0.001

TNF-α (pg/mL)

Immediate postoperative 1.97 ± 0.79 1.88 ± 0.73 0.491

1 day postoperative 12.35 ± 2.54 9.84 ± 3.16 0.001

3 days postoperative 9.76 ± 1.31 7.79 ± 1.39 0.017

IL-6 (pg/mL)

Immediate postoperative 5.85 ± 1.78 5.96 ± 1.91 0.729

1 day postoperative 28.74 ± 2.02 22.28 ± 2.12 0.001

3 days postoperative 23.58 ± 1.37 20.16 ± 1.72 0.003

Notes: RIRS: Retrograde intrarenal surgery; UMP: Ultra-mini percutaneous nephrolithotomy; CRP: C-reactive pro-

tein; TNF: Tumor Necrosis Factor; IL: Interleukin.

78 Guan et al.

Investigación Clínica 63(1): 2022

calyceal stones with a diameter greater than 2

cm. The SFR was as high as 90% one month af-

ter operation. Compared with that in the PCNL

group in the same period, the SFR was as high

as 90.6% one month after operation, displaying

no statistically significant difference. Zeng et

al. 18 applied UMP to treat lower calyceal stones

with a diameter smaller than 25 mm, and the

channel size was F12-14. The SFR could reach

95.8% three months after operation, and the

incidence rate of postoperative complications,

especially the blood loss, was significantly re-

duced, suggesting that UMP has a good applica-

tion prospect in the treatment of kidney stones.

The results of this study showed that compared

with those in UMP, the average operation time

was obviously prolonged, the postoperative

hospital stay was markedly shortened, and the

total hospitalization expenses were remarkably

reduced in the RIRS group. However, the loss of

Hb after operation in the UMP group was only

(7.9±3.7) g/L due to the thinner operation

channel, which was higher than that in RIRS

group (5.0±3.4) g/L, but it notably declined in

comparison with that after PCNL (9.6 g/L on

average) reported in the literature 19, indicat-

ing that the effect of UMP in reducing blood

loss is satisfactory. In addition, there were no

statistically significant differences in the VAS

score and BCS score between the two groups of

patients 24 h after operation, and the pain did

not increase because of the puncture, implying

that UMP has a slight impact on patients due

to the small puncture channel.

The incidence rate of systemic inflam-

matory response syndromes after endoscop-

ic stone surgery was 8.6-11.4%, and without

timely treatment, the syndromes in some

patients will develop into urinary sepsis and

even cause death. It is reported that exces-

sive intrapelvic pressure [>30 mmHg (1

mmHg=0. 133 kPa)] and long accumula-

tion time (>50 s) can evidently increase the

incidence rates of postoperative fever and

urinary sepsis 20, 21. The results of this study

manifested that the postoperative fever rate

was 8.8% in the RIRS group and 5.9% in the

UMP group. Besides, the level of inflamma-

tory factors in the UMP group was also mark-

edly lower than that in the RIRS group. This

may be due to the fact that negative pres-

sure suction was utilized during UMP, which

reduced the pressure in the renal pelvis and

the risk of infection.

SFR is an important indicator for evalu-

ating the effectiveness of lithotripsy. Accord-

ing to a report, the included angle between

the infundibulum of the lower calyx and pelvis

affects the SFR of RIRS in treating lower caly-

ceal stones. The smaller the included angle

is, the lower the SFR will be 22. In the treat-

ment of lower calyceal stones using UMP, the

lower calyx can be directly punctured, thus

avoiding this effect. The results of this study

illustrated that the SFR after the first-stage

surgery in UMP group was significantly high-

er than that in RIRS group. It is believed that

if the stone hardness is high and bleeding

during operation affects the visual field, the

operation time will be too long. Besides, if

there is urinary tract infection before opera-

tion, secondary surgery or postoperative as-

sisted lithotripsy should be considered, and

the double-J stent catheter can be indwelt

after operation, which is beneficial to both

the first-stage RIRS and the postoperative

lithotripsy.

This study was a retrospective study. The

number of enrolled patients was limited, the

follow-up time was short, the follow-up con-

tent was not comprehensive, and the long-

term prognosis of patients was not analyzed.

In the future, long-term follow-up multi-cen-

ter studies with large sample sizes are needed

to verify the conclusions of this study.

As a conclusion, RIRS and UMP are

safe and effective in the treatment of 2-3 cm

lower calyceal stones. The first-stage UMP is

characterized by a high SFR, short operation

time and low postoperative infection risk,

while RIRS is featured with less blood loss

and low total expenses.

UMP and RIRS in lower calyceal stones 79

Vol. 63(1): 70 - 80, 2022

Funding

None.

Declaration of conflict of interest

No conflict of interest.

Authors’ ORCID numbers

• Yawei Guan: 0000-0001-7960-3135

• Xing Ai: 0000-0001-9043-4918

• Zhihui Li: 0000-0002-6282-1475

• Guohui Zhang: 0000-0003-1050-247X

• Zhuomin Jia: 0000-0002-1474-0128

• Jingfei Teng: 0000-0001-5294-3914

Authorship contribution

• YG, XA , ZL: planning, results and fi-

nal editing.

• YG ,XA: writing of the paper.

• ZL, GZ, ZJ, JT: data collection and

analyses.

• All authors approved the final ver-

sion of the manuscript.

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