Clinical Analysis of a Coaxial Dilator Set Attached to Needle Puncture for Percutaneous Nephrolithotomy

doi:10.4236/oju.2013.36046

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Open Journal of Urology, 2013, 3, 248-252

http://dx.doi.org/10.4236/oju.2013.36046 Published Online October 2013 (http://www.scirp.org/journal/oju)

Clinical Analysis of a Coaxial Dilator Set Attached to

Needle Puncture for Percutaneous Nephrolithotomy*

Evandilson Guenes Campos de Barros1#, Salvador Vilar Correia Lima2, Fabio de Oliveira Vilar3,

Eugenio Soares Lustosa4, Roberto Santos Lima4

1Master’s Program of Post Graduation in Surgery, Center of Health Sciences, Federal University of Pernambuco, Pernambuco, Brazil

2Department of Surgery, Federal University of Pernambuco, Pernambuco, Brazil

3Urology Service of the Hospital das Clinicas, Federal University of Pernambuco, Pernambuco, Brazil

4Member of the Brazilian Society of Urology, Recife, Brazil

Email: #[email protected]

Received August 19, 2013; revised September 17, 2013; accepted September 25, 2013

mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work

is properly cited.

ABSTRACT

Introduction: Percutaneous approach to the kidney is a very useful alternative in renal surgery which minimizes the

morbidity of a variety of procedures. Objectives: To evaluate the efficacy, practicity of a reusable system of metallic

coaxial dilator coupled to a special puncture needle to perform lumbar puncture and dilation of the percutaneous tract.

Methods: A randomized experimental study was carried out involving 50 individuals. These patients were randomized

as follows: Group 1 had the procedure performed with the conventional disposable Amplatz set traditionally used for

this procedure. Patients in Group 2 were operated utilizing the new reusab le coaxial set specially designed for th is pur-

pose. The following parameters were measured to compare the 2 groups: sex Corporeal Mass Index (CMI), Pre and

postoperative hematocrit and hemoglobin. Time interval between the puncture, dilation and access to the renal pelvis

and insertion of the nephroscope were also analyzed. Results: There was no statistical difference between the 2 groups

concerning hematocrit and hemoglobin changes when comparing pre- with postoperative period. Patients in Group 2

required a significant lower time between puncture and final access to the upper collecting system. Conclusion: The

new coaxial dilator set showed to be as safe as the conv entional Amplatz set with the advan tage of reusability and de-

crease of tract dilation time.

Keywords: Percutaneous Nephrolitho tomy; Metallic Coaxial Dilator; Kidney Stone

1. Introduction

Urinary lithiasis is one of the most common diseases af-

fecting the urinary tract with an incidence rate ranging

from 5% to 15% according to world literature [1]. Offi-

cial data from Brazilian health system indicate that over

300.000 hospital admissions occurred between January

and May 2012. From this group, 8.79% were related to

urinary stone disease [2].

The removal of urinary stones has evolved signifi-

cantly in the last 25 years since the introduction of per-

cutaneous nephrolithotomy (PNL) ureterorenoscopy (URS )

and extracorporeal shockwave lithotripsy (ESWL). The

sophistications introduced to these equipments and dif-

ferent sources of energy to destroy stones gave a new

insight to the adequate definition of the type of treatment

to be applied according to stone size and location and as

such represents a significant advance in the treatment of

this disease [3,4]. In an attempt to reduce costs and time

to perform percutaneous approach to the kidney without

increasing morbidity to th e procedure, we propose a new

reusable dilating system, which significantly decreases

these items and offers new possibilities in performing

percutaneous renal surgery. In this procedure, a path is

created for percutaneous removal of stones by using an

association of principles already used for this purpose.

On the other hand, serial or telescopic, pneumatic dila-

tors have shown to require greater surgical time and in-

creased incidence of bleeding [5]. Most surgeons prefer

to use sequential dilators to create access to the kidney.

*I declare that all information shown in this study are results of ou

work and there is no plagiarism.

#Corresponding author.

With the development of more sophisticated devices, it

is possible to promote a gateway to the kidney with

E. G. C. DE BARROS ET AL. 249

lower diameter (11 - 18 French) and consequently less

morbidity to the patient [6].

The aim of the present study is to test the efficacy and

practicability of this new reusable set of metallic coaxial

dilating system in comparison with the disposable system

normally used in clinical practice (Figures 1 and 2). As

the basic principles of the surgical technique have not

been modified, an experimental trial of the procedure

was not performed in animals.

2. Patients and Methods

A randomized clinical study, involving 50 patients from

our outpatient clinic suffering from nephrolithiasis with

surgical indication for percutaneous nephrolithotomy was

carried out to prove the feasibility of this method. Pa-

tients were informed about the objectives of the study

and invited to participate.

Patients age ranged between 20 and 60 years and were

Figure 1. Special extra lenght puncturing ne e dle and coupled dilating set.

Figure 2. Schematic drawing of the dilating set and its coupling and operating way.

E. G. C. DE BARROS ET AL.

250

randomized into two groups: Group 1: patients with medi-

cal records ending in ev en numbers who underwent PN L

technique using conventional disposable sequential Am-

platz dilators. Group 2: patients in the records ending in

odd numbers who underwent the procedure use the new

coupled coaxial d ilators.

Two main parameters were analyzed: time spent be-

tween puncturing and dilating the tract and insertion of

the nephroscope confirming access to the renal collecting

system; blood loss was evaluated by checking HT and

HB in the pre-operative period, 24 hours after the proce-

dure and at discharge. Possible complications of dilation

process—like renal pelvis and renal pedicle vessels injury,

puncture of solid organ or bowel were also analyzed.

Statistical analysis was divided into three steps accord-

ing to the objectives previously established: Comparison

of the groups according to sex, age, BMI, Hb and Ht;

comparison of groups of time dilation; intragroup com-

parison (pre X post) and between groups as related to Hb

and Ht.

To compare the distributions by gender we used the

chi-square test, and the Student t test was applied to com-

pare quantitative variables (age, BMI, Hb and Ht) be-

tween groups.

The nonparametric Mann-Whitney test was used to

compare the groups related to time spent to dilation due

to lack of normality of this variable.

To evaluate the differences between both groups (ex-

perimental standard X) and between times (pre X post)

regarding the variables Ht and Hb, we used a model of

analysis of variance (ANOVA) with repeated measure-

ments.

The study was approved by the Ethics Committee for

Clinical Research of the Institution.

3. Results

The results are illustrated in the Tables 1 and 2, which

shows that there was no statistically significant differ-

ence between the groups as related to variables, i.e., the

groups can be cons i dere d h o mogeneous for this pu rp ose.

There is a statistically significant difference between

groups (p < 0.05). The time dilation of the experimental

group was lower than the standard group.

This analysis evaluated the effects of group, time ef-

fects and the interaction effects between groups and time.

Because the interaction was not considered statistically

significant (p > 0.05) for both the Hb and to the Ht, we

evaluated the effect of group (collectively for all times)

and end time (jointly for both groups).

Analyzing the results of ANOVA, it can be stated that:

Hb: no significant difference between groups (p = 0. 4 0 3 )

in the two periods. When analyzing intra-group compari-

son (pre X post) it wa s found that there was a significant

reduction in pre and post results in both groups (p =

0.007).

Ht: no significant difference between groups (p = 0.204)

in the two periods. When analyzing intragroup compari-

son (pre X post), it w as found that there was a significant

reduction from pre to postop results in both groups (p =

0.009).

There was only one complication in one patient in

Group 1 (Amplatz dilators). An inadvertent perforation

of the renal pelvis, leading to the development of ascites

urinosa was found. There were no complications in the

group using the new coaxial dilato r. The presence of this

unique complication was not statistically significant in

the study.

4. Discussion

There are various techniques described to perform access

directly to the collecting system, the most frequent being

Amplatz dilators, coaxial Alken dilators and balloon di-

lators. Such techniques have similar complication rates [7].

The ideal technique for percutaneous access must have

acceptable complication rates, promote easy access to the

renal collecting system and at the same time provide low

economic impact. The number of kidney punctures re-

quired to perform an adequate nephrostomy tract is di-

rectly related to bleeding in percutaneous nephrolith-

otripsy [8] .

Table 1. Results of the analysis of homogeneity between

groups.

Groups

Standard Experimental

Variable p-valor

Females 13 (52%) 13 (52%) 1.00

Age (years) - Mean (SD)

Min imum - Ma xi mum 42.3 (11.5)

24 - 66 37.6 (10.9)

22 - 58 0.146

BMI - Mean (SD)

Min imum - Ma xi mum 28.3 (4.5)

21.6 - 41.0 29.6 (4.1)

23.1 - 38.20.282

Hb - Mean (SD)

Min imum - Ma xi mum 13.9 (1.4)

11.4 - 17.5 13.76 (1.2)

11.7 - 16.40.387

Ht - Mean (SD)

Min imum - Ma xi mum 42.0 (4.2)

35 - 51 40.4 (3.1)

35.8 - 46.50.134

SD = standard deviation; BMI = body mass index.

Table 2. Results of the comparison between the groups with

respect to tim e dilation.

Groups

Standard Experimental

Dilation Time (minut es) p-valor

Median 12 2.2

P25 - P75 8.6 - 12.5 1.5 - 2.4 <0.001

P25: Percentile 25, P75: Percentile 75.

E. G. C. DE BARROS ET AL. 251

The preference for the comparative study between the

coaxial dilator and coupled sequential dilators refers to

the failure rate of inflatable dilators (17%). This rate rises

to 25% when applied to patients with previous surgery

[9]. Pneumatic dilators have not shown better results than

the Amplatz dilators concerning decreased surgical time

and decreased postoperative complications and a higher

cost [10].

According to data collected, there was homogeneity

between groups A and B, related to gender, age, body

mass index (BMI), and hematological: hemoglobin (Hb)

and hematocrit (Ht).

The concern about having homogeneous groups refers

to the possibility of difficulty in performing the proce-

dure on specific groups, mainly related to BMI. This

confirmation supports the reduction rates of research

biases. Kessaris et al. [11] analyzed 2200 percutaneous

renal procedures and stated that it was not a risk factor

for renal bleeding: age, sex, number of punctures renal

and procedure duration.

The measurement of efficacy in performing the ne-

phrostomy tract was defined as the time required estab-

lishing the path after percutaneous puncture of the col-

lecting system and insertion of the nephroscope. The

time dilation was lower in the group that used the new

coaxial dilator: The mean time spent with the standard

technique 12 was minutes, and 2.2 minutes with the new

set (p < 0.001). This can be explained by the elimination

of some steps in the dilating processs, which leads to

savings in time such as switching stabilizer using a punc-

ture needle as a guide; stabilizer safety valve “stop”,

which prevents the progression of the device in addition

to the limit established by the surgeon, decreasing com-

plication rates; sequential dilators and coupled to the

system in monoblock; stabilizer removed en bloc and

dilator set, maintaining 30 French (F) sheath and guide

wire.

The level of bleeding caused by the dilato r was similar

in both groups, as shown by comparing drop in Hb and

Ht between groups and within groups. No patient in both

groups required blood transfusion. These data confirm

reports of the literature [12]. Michel et al. [13] in a series

of 315 cases reported 17.5% of bloo d transfusion.

Bleeding is the most common complication and is as-

sociated with the number of punctures, stone volume and

diameter of the surgical material [8]. All patients under-

went only one puncture per treatment session, the di-

ameter of the material used was 30 F in the two groups.

As described before the bleeding rates are similar to the

reports by others [13].

The overall rate of complications in percutaneous ne-

phrolithotomy can reach up to 83% [14]; however, the

vast majority of these complications are minor, such as

bleeding or fever without further repercussions. Major

complications occur between 0.4% - 4.7% to sepsis and

0.6% - 4% to renal bleeding needing surgical interven-

tion [6]. In the present study, one lesion of the renal pel-

vis was observed in the control group. No complications

were seen in the study group.

When considering costs to perform perctaneous neph-

rolitotripsy, although no specific studies were performed

specifically considering this item the new set of dialato rs

promotes significant savings according to the literature

without increasing the surgical risks to patients and

maintaining similar efficacy [15].

5. Conclusion

Data obtained in the present stu dy support the idea that a

reusable coaxial metallic set may represent a feasible

option in the percutaneous approach to the kidney and

produces significant savings especially for institutional

use without increasing surgical risks.

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List of Abreviations

PNL: Percutaneous nephrolithotomy

URS: Ureterorenoscopy

ESWL: Extracorporeal shockwave lithotripsy

BMI: Body mass index

Hb: Hemogl o bin

Ht: Hematocrit

ANOVA: Analysis of varianc e

F: French