J Ayub Med Coll Abbottabad 2015;27(2)
ORIGINAL ARTICLE
FREQUENCY AND FACTORS EFFECTING NON CLEARANCE OF
LOWER POLE RENAL STONES
Amin Ullah, Mohammad Zubair, Nouman Khan, Asif Malik
Institute of Kidney Diseases and transplant, Hayatabad Medical Complex, Peshawar-Pakistan
Background: Renal stone disease is a major health hazard in Pakistan and extra-corporeal shockwave
lithotripsy is one of comprehensive method used to treat these stones. The aim of this study is to
determine the frequency of factors affecting the non-clearance of stone fragments of lower pole renal
stone after extra corporeal shockwave lithotripsy. The study was done with the objective to determine
the frequency the spatial anatomical factors which can influence the non-clearance of lower pole stone
fragments after ESWL. Methods: One and nineteen (119) patients with lower pole renal stone less
than10mm were subjected to maximum 3 sessions of extracorporeal shock wave lithotripsy. KUB
radiographs, ultrasonography and intravenous urography were used as investigative tools for lower pole
renal calyceal anatomy. X ray KUB and ultrasound were done after a week for clearance. Data was
analysed with the help of SPSS version 10.0 and presented in the forms of tables and graphs. Results:
There were 77 (64.71%) males and 42 (35.29%) females. Infundibulo-pelvic angle (IPA)>40º was
present in 93 (78.15%), Infundibular length (IL) <22 mm in 107 (89.92%) and Infundibular width (IW)
>4 mm was present in 100 (84.03%) patients. The frequency of stone non clearance was noted in 31
(26.05%). Infundibulo-pelvic angle (IPA)>40º (p=0.000), Infundibular length (IL)<22 mm (p=0.001)
and Infundibular width (IW)>4 mm (p=0.046) were significant variables affecting stone clearance.
Conclusion: The frequency of non-clearance of lower calyx of kidney stone is 26.05%. The clearance
of fragments of the lower calyx kidney stones is affected by three spatial anatomical factors, i.e.,
Infundibulopelvic angle, Infundibular width and infundibular length.
Keywords: Extracorporeal shock wave lithotripsy; non clearance of lower pole kidney stones;
Infundibulopelvic angle; Infundibular width; infundibular length.
J Ayub Med Coll Abbottabad 2015;27(2):384–7
INTRODUCTION
Extra corporeal shock wave lithotripsy (ESWL) is
convenient non-invasive, and safe OPD procedure,
causing fragmentation of stone into minute particles,
by shock waves. These Fragmented particles are
passed in urine, in due course, resulting in a stone-free
patient.1 The treatment of choice for renal stones up to
2cm is ESWL. After introduction of ESWL in 1980’s,
it is the preferred treatment option for the majority of
renal calculi.2,5 The clearance rate of renal calculi after
ESWL varies, ranging between 45–95%.1 Several
factors affect stone integration which includes stone
composition, number of stone and patient factors like
body habitus and obesity. Operator experience, type of
lithotripsy, number of shock wave, location of stone
and pattern of intra-renal collecting system also affect
the outcome.1,4–7 The rate of stone fragments clearance
is worse over lower calyces than the middle and upper
calyces.5
The primary modality for treatment of Lower
Calyceal calculi is retrograde intra-renal surgery in
many centre’s.8 Better stone-free rates can be achieved
by Percutaneous nephrolithotomy (PCNL) which is
associated with higher morbidity though more invasive
and stone size does not affect the outcome.9 Lower
pole calyceal calculi are treated with ESWL as it is
non-invasive with high level of patient acceptance and
384
does not require any anaesthesia.6,7 Stone clearance
rate of 41–73% for stones up to 10 mm has been
quoted in several studies.5,6 The stone free rate is also
influenced by the lower pole infundibulo-pelvic angle
(LIPA), the infundibulum length and infundibulum
width1,2,5 Infundibular height of ≤22 mm had 68.6%
stone-free3 and patients with infundibular width ≥4
mm and infundibulo-pelvic angle ≥40º had stone
clearance rate of 53.8% and 52% respectively.1,7,9
Tight infundibular width, long infundibular length and
acute lower pole infundibulo-pelvic are associated
with a reduced stone-free rate.
This study aimed to determine the frequency
of influence of three spatial anatomical factors, i.e.,
infundibulo-pelvic angle, infundibular width and
infundibular length of the lower calyx of kidney on
stone clearance after extracorporeal shock wave
lithotripsy and to provide local statistics about the
clearance of lower pole calyceal stone after treatment
with ESWL and follow up outcome.
MATERIAL AND METHODS
This cross-sectional study was carried out at Urology
and Transplant Unit at Institute of Kidney Diseases
Hayatabad Medical Complex, Peshawar from Feb
2013 to Feb 2014. Using WHO software for sample
size determination, sample size was calculated to be
119, using 27% proportion of non-clearance of stone27,
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J Ayub Med Coll Abbottabad 2015;27(2)
95% confidence level and 8% margin of error. Nonprobability consecutive sample technique was used.
All the patients of both genders with lower
pole renal stone ≤10 mm with age group 18–60 years
were included in the study. While patients with acute
urinary tract infection, blood coagulopathies,
Pregnancy and Uncorrected obstruction distal to the
stone were excluded.
During study a complete history and patient
data was obtained followed by examination, Complete
blood count, serum urea, serum creatinine and
urinalysis were performed in all patients and were
recorded. The X-ray KUB, ultrasonography and
intravenous urography were used as an investigative
tool for lower pole renal calyceal anatomy. The Oral
analgesics were given to all patients an hour before the
ESWL treatment. Maximum 3 sessions of
extracorporeal shock wave lithotripsy were given. The
patients were followed by X-ray KUB and ultrasound
for stone clearance after a week. Factors leading to
non-clearance of stone were assessed in patients with
residual stones as per operational definition.
Statistical analysis was done using SPSS-10.
Frequencies and percentages were computed for
categorical variables like gender, non-clearance of
stone and lower pole renal anatomical factors, i.e.,
IPA, IL and IW. Stratification of age, gender and size
of stone were done to see the effect of that on nonclearance and factors leading to it. Chi square test was
applied to it and p≤ 0.05 was taken as significant. The
logistic regression analysis was applied to compare the
groups and control the confounding variables. The
results were presented in the form of tables and graphs.
RESULTS
The total number of patients was 119 including 77
(64.71%) males and 42 (35.29%) females. According
to age distribution there were 33 (27.73%) from the
age group of 18–30 years, 26 (21.85%) between the
ages of 31–40, 30 (25.21%) patients in 41–50 years
and 27 (22.69%) were 51 years old and above. Mean
age of male and females were 39.5065 years±11.8562
SD and 39.6190 years ±12.3426 SD respectively with
an overall mean age of 39.5462 years±11.9779 SD
The mean size of stone in males and females
was 8.3636 mm±1.2764 SD and 8.3571 mm±1.0317
SD respectively with overall mean size of kidney stone
of 8.3613 mm±1.1913 SD.
Infundibulo-pelvic angle (IPA) >40º was
present in 93 (78.15%), Infundibular length (IL) <22
mm in 107 (89.92%) and Infundibular width (IW) >4
mm was present in 100 (84.03%) patients
The frequency of stone non clearance was
noted in 31 (26.05%) while stone clearance was noted
in 88 (73.95%) patients after extracorporeal shock
wave lithotripsy.
According to age wise distribution, maximum
stone non clearance was noted in the age group of 18–
30 years which was 11 (9.24%) followed by 10
(8.40%) in 31–40 years while it was in 5 (4.20%)
patients in each age groups of 41–50 years and 50 and
above. The difference between different groups was
statistically insignificant as shown by chi square of
33.670 and p-value of 0.246. According to gender wise
distribution, stone non clearance in males was noted in
19 (15.97%) and 12 (10.08%) in females the difference
was statistically insignificant as shown by p-value of
0.323
Stone non clearance distribution according to
size of stone was noted maximum in 11 (9.24%) in
patients having 10mm stone while it was minimum in
patients having 9mm stone, i.e., 5 (4.20%) as shown in
table-2.
According to anatomical variables, stone non
clearance was noted in 17 (14.29%) patients having
Infundibulo-pelvic angle (IPA) >40º, in 21 (17.65%)
patients having Infundibular length(IL) <22 mm and in
27 (22.69%) patients having Infundibular width (IW)
>4 mm as shown table-3.
Table-1: Frequency of anatomical variables of
lower pole of kidney in patients having lower calyx
kidney stone ≤10mm treated with extracorporeal
shock wave lithotripsy
Anatomical factors
IW>4mm
IL<22mm
IPA >40º
No. of patients
100
107
93
Total percentage
84.03%
89.92%
78.15%
Table-2: Stone non clearance according to size of
stone from lower calyx of kidney treated with
extracorporeal shock wave lithotripsy
Size of stone
(mm)
7.00
8.00
9.00
10.00
Total
Clearance of Stone
Yes
No
31 (26.05%) 8 (6.72%)
22 (18.49%) 7 (5.88%)
15 (12.60%) 5 (4.20%)
20 (16.81%) 11 (9.24%)
88 (73.95%) 31 (26.05%)
X2=2.119
Confidence
Interval=0.471–1.183
p-value= 0.213
Table-3: Stone non clearance according to
anatomical variables of lower pole of kidney
treated with extracorporeal shock wave lithotripsy
Anatomical
Clearance of Stone
Variables
Yes
No
Infundibulo
83
X2=26.631,
17 (14.29%)
Yes
pelvic angle
(69.75%)
Confidence
(IPA) >40º
Interval=0.012-0.236,
No 5 (4.20%) 14 (11.76%)
p-value=0.000
Infundibular
86
X2=22.732,
21 (17.65%)
Yes
length(IL) <
(72.27%)
Confidence
22 mm
Interval=3.943No 2 (1.68%) 10 (8.40%) 171.204,
p-value=0.001
Infundibular
66
X2=1.965,Confidence
27 (22.69%)
Yes
width (IW)
(55.46%)
Interval=1.032-23.903,
>4mm
p-value=0.046
22
4 (3.36%)
No
(18.49%)
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J Ayub Med Coll Abbottabad 2015;27(2)
DISCUSSION
In the recent decade, various treatment options have
been evolved for lower-pole kidney stones and among
these ESWL is considered as one of the best and least
invasive procedures.10 ESWL is commonly used and
accepted worldwide treatment option for urinary
lithiasis. It is easy to use, non-invasive, highly
affective and widely available. It acts by number of
mechanical and dynamic forces e.g. cavitation, shear
and spalling.11 In our study, the frequency of stone non
clearance was 26.05% while stone clearance was noted
in 88 (73.95%) patients after extracorporeal shock
wave lithotripsy. However, several recent studies has
shown12 variable clearance rate using ESWL. In our
patients, Infundibulo-pelvic angle (IPA) >40º was
present 78.15%, Infundibular length(IL) <22 mm in
89.92% and Infundibular width (IW) >4 mm was
84.03% patients. Gender, age groups and size of stone
were insignificant for the non-clearance of lower pole
kidney stone while the three anatomical variables i.e.
IPA >40º (p=0.000), IL <22 mm (p=0.001) and IW >4
mm (p=0.046) are significant independent variables.
Wazir BG13, reported safe and effective use of ESWL
in treating upper ureteric and kidney stones. In his
study Stone free rate of 89% with 7% stone fragments
less than 4 mm were reported in patient with stone size
up to 1cm. In another local study by Ashraf HS14,
single successful treatment session after ESWL was
44%, two session treatment was 36% while 20%
required three sessions for successful stone
fragmentation. Stone non clearance was noted in 34%
patients even after three sessions within three months
follow-up.
No statistically significant effect of stone
size, anatomy of the lower calyx and BMI on stone
clearance after ESWL of lower calyceal stones was
found in a retrospective study by Azab S.15 Stone
clearance was 52% in patient with lower pole IPA ≥45
and 32% in patients with IPA <45◦ which was not
statistically significant. No statistical difference was
noted in patient with IL <35 mm vs. ≥35 mm and
width <4 mm vs. ≥4 mm.
Extracorporeal shock wave lithotripsy was
used to treat lower pole stone of <20 mm in
prospective study by Deenari R, et al.16 The clearance
rate for stones <10 mm was 93% and 86% for stone
size 11–20 mm. Patients with LPC angle of <90° and
angle of >90° had stone clearance of 92% and 97%
respectively. The stone clearance was 93% for IW >4
mm.
In Patients with LPC of <90° and IW of <4
mm for stone size of <20 mm, more ESWL session
and shocks were used in a study by Ather MH, et al.17
After follow up of three months, the clearance for
stone size ≤10 mm was 93%, for stone sizes of 11–15
386
mm was 96% and for stone size of 16–20 mm was
90%, which was not statically significant. The LPC
<90 had clearance rate of 94% and > 90 has clearance
of 100%. And IW <4 mm had clearance of 93% and
100% for IW of >4 mm.
ESWL was compared with mini-PCNL for
managing patients with residual stone after Intra
corporeal lithotripsy(ICL) in patient in a study by
Huang Z, et al.18 The stone-free rates was 97.3% with
ICL and 82.4% undergone mini PCNL, respectively
with overall stone free rate of 90.1%.
Various favorable anatomical factors as
predictors of lower pole stone clearance were analysed
by Sumino Y, et al19 (lower infundibular length-todiameter ratio >7, infundibular diameter >4 mm. and a
single minor calix). Patient with all three favourable
factors had clearance rate of 86.4% and with one or
two favourable factors has clearance rate of 60% and
6.7% in patient with none of these favourable factors.
Ruggera L, et al20 found that narrowed LPC and long
IL and smaller IW were unfavourable factors for stone
clearance after ESWL for lower stones.
In our study stone size <10mm was
insignificant (p=0.213) in stone clearance but some
authors have reported opposite to this. In a study by
Sorensen CM, et al21 he reported that stone size rather
than caliceal anatomy is predictive of treatment
outcome. ESWL for primary lower pole renal stones
≤20 mm was studied Excretory urogram in this study
The stone-free rate was reported 78% for stones of ≤5
mm , 73% for stones of 6-10 mm, 43% for stones of
11-15 mm and 30% for stones of 16–20 mm. The
favourable anatomical factors (lower pole LPC of ≥
70, lower pole IL ≤30 mm. and lower pole IW ≥5
mm.) were also not predictive of success. The
frequency of non-clearance of lower calyx of kidney
stone after ESWL is 26.05%.
CONCLUSION
The clearance of fragments of the lower calyx kidney
stones is affected by three spatial anatomical factors
i.e., Infundibulo-pelvic angle, Infundibular width and
Infundibular lenth.
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Address for Correspondence:
Dr Aminullah, Institute of Kidney Diseases and transplant, Hayatabad Medical Complex, Peshawar-Pakistan
Cell: +92 333 918 5114
Email: drjamrud@gmail.com
http://www.jamc.ayubmed.edu.pk
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