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Keywords:

  • anthropometric;
  • ureteric length;
  • body habitus

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Authors from the USA describe a method of correlating anthropometric variables of body habitus with ureteric length; they found height to be the variable that correlated most closely with ureteric length, but ureteric length was nevertheless difficult to predict.

OBJECTIVE

To evaluate the association of variables of body habitus with direct measurements of ureteric length, as the correct choice of ureteric stent length might help to prevent complications and improve stent tolerance, and to date there are limited data correlating height or other body variables with ureteric length.

PATIENTS AND METHODS

We prospectively measured pelvi-ureteric junction to vesico-ureteric junction length in 100 patients by placing a ruled 5 F ureteric catheter. Ureteric length was then correlated with patient height, weight, body mass index, and distance from the shoulder (acromium process) to the wrist (head of the ulna; S–W), the elbow (olecranon process) to the wrist (head of the ulna), xyphoid process to umbilicus, xyphoid process to pubis (X–P), umbilicus to pubis, and anterior iliac spine to anterior iliac spine. Patients with pathology affecting the ureteric length were excluded. The results were analysed statistically using a multiple linear regression model with stepwise selection of variables, and a paired t-test.

RESULTS

The mean right and left ureteric lengths were similar (P = 0.61); height (P < 0.01), weight (P = 0.02), X–P (P = 0.01), and S–W (P = 0.02) distances all correlated with ureteric length. On multivariate regression analysis, weight, height and male gender were associated with mean ureteric length. From these data a formula was constructed to predict ureteric length.

CONCLUSIONS

It is a challenge to predict ureteric length from body habitus, but height, X–P distance and S–W distance can be used to predict ureteric length.


Abbreviations
S–W

shoulder (acromium process) to the wrist (head of the ulna)

E-W

elbow (olecranon process) to the wrist (head of the ulna)

X–U

xyphoid process to umbilicus

X–P

xyphoid process to pubis

U–P

umbilicus to pubis

AIS–AIS

anterior superior iliac spine to anterior superior iliac spine

BMI

body mass index.

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Advances in all urological surgery, including open, minimally invasive endoscopic and laparoscopic procedures, has lead to the increased used of ureteric stenting [1]. Ureteric stents are invaluable in the management of ureteric obstruction, urological reconstruction, and complications arising from various open, laparoscopic and endourological procedures.

Ureteric stenting to relieve obstruction was first described in 1967, using straight ureteric catheters that were externalized, usually through the urethra [2]. Seven years later, the distal ‘pigtail memory’ stent was described by McCullough [3]. This stent was popularized 4 years later by Hepperlen et al.[4], who used the pigtail system for polyethylene stents. In 1978, Finney [5] introduced and first described the clinical application of an indwelling ureteric stent, which added a second pigtail to the distal end of the stent to prevent upward migration. Since then, while there have been minimal modifications to indwelling stent design, the basic stent design has remained unchanged.

Despite the utility of the double-pigtail stent there is significant morbidity associated with its use, including significant patient discomfort (urinary frequency and urgency, bladder pain, flank pain, haematuria, intermittent urinary incontinence) [6]. Also, stent migration occurs in 1–8% of stented patients [7–10]. Some of the problems associated with indwelling ureteric stenting have been attributed to poor stent placement or improper stent selection (i.e. a stent that is too short will predispose to stent migration, or a stent that is too long will irritate the bladder wall or trigone). Accurate sizing of stents is needed to minimize patient discomfort arising from improper stent selection [11].

Most manufacturers define the length of stents as the straight portion of the stent between the coils. Ideally, the proximal coil should lie in the renal pelvis or upper pole, and the distal coil should deploy in the bladder next to the ureteric orifice. Thus a correct length of stent will minimize contact of the stent with the urothelium, and the risk of stent migration.

Clinically, the length of the ureteric stent has been selected by arbitrary and inconsistent methods. A prospective series found that the patient’s height best estimated the correct choice of ureteric stent length [12]. However, a recent prospective study of 203 patients showed that patient height did not correlate well with ureteric length [6]. Even so, most urologists estimate the stent length from the patient’s height, but the formula by which the stent length is estimated is different among individual practitioners. Paick et al.[6] recommended selecting stent length based on IVU data correlating actual ureteric length with the linear dimension of the ureter. However, over the last 5 years, CT has largely replaced IVU in the management of urolithiasis, and thus IVU data are not routinely available in most contemporary patients.

Thus in the present study we determined which variables of body habitus correlated best with ureteric length based on direct measurements with a ureteric catheter placed from the PUJ to the ureteric orifice. Also, we evaluated right and left ureteric length to determine if laterality might affect the choice of ureteric stent length.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Permission for the study was obtained from the Institutional Review Boards of our institutions. Between August 2003 and January 2005, 100 patients were included if they were ≥18 years old and undergoing cystoscopy, retrograde pyelography, or ureteroscopy for benign or malignant disease. Patients were excluded if pregnant, or with gross tortuosity or dilation of the ureters, where at least one ureter could not be measured, where head-to-heel measurements could not be obtained, or if there was vaginal vault eversion beyond the introitus, or patients for which the location of the PUJ could not be determined, or with any other gross abnormality of body habitus.

Before any intervention, the variables of body habitus were measured: weight, height, distance from the shoulder (acromium process) to the head of the ulna (S–W), elbow (olecranon process) to the wrist (head of the ulna, E–W), xyphoid process to umbilicus (X–U), xyphoid process to pubis (X–P), umbilicus to pubis (U–P), and anterior superior iliac spine to anterior superior iliac spine (AIS–AIS) (Fig. 1). Before surgery a ruled 5 F ureteric catheter (Boston Scientific, Natick, MA, USA) was used to measure both ureters in each patient. The ureteric length was defined as the length between the PUJ (which was defined fluoroscopically after a gentle retrograde ureteropyelogram) and the ureteric orifices (which were directly visible on cystoscopy); during each measurement the bladder was minimally full.

image

Figure 1. Body habitus values measured and correlated with ureteric length. Image adapted from Leonardo da Vinci’s Vetruvian man.

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All measurements of body habitus were assessed for any association with ureteric length in a multiple regression model with a stepwise selection procedure. Residual plots from the final model were used to examine distributional assumptions (normality and constant variance). Partial residual plots were used to examine the functional relationship between body habitus values and ureteric length in the final model. In addition, left and right ureteric lengths were compared to determine if there was a significant difference between them within individuals, using a paired t-test.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

In all, 100 patients were included (50 women and 50 men); 90 were Caucasian, nine were African-American and one was Asian. The mean patient height and weight were 168 cm and 90 kg, respectively. The mean computed body mass index (BMI) was 31 kg/m2. The mean distances from S–W, E–W, X–U, X–P, U–P, and AIS–AIS were 55, 26, 19, 34, 17, and 35 cm, respectively. The mean length of the right and left ureter was 26 cm (P = 0.63).

As the mean of the left and right ureters were not significantly different, multiple regression analysis was based on the mean ureteric length of both. Table 1 lists all variables with their Spearman correlation coefficients and P value. Patient height, weight, X–P and S–W correlated best with ureteric length, as predicted by the Spearman correlation. In addition, a multivariate regression analysis determined weight and height as the most reliable variables for predicting mean ureteric length. From this analysis a formula was derived for predicting the mean ureteric length:

Table 1.  The correlation of mean ureteric length with the other variables
VariableSpearman correlationP
Age0.180.07
Height0.290.002
Weight0.230.02
BMI0.100.29
X–P0.250.01
X–U0.150.12
U–P0.140.16
S–W0.230.01
E–W0.110.20
AIS–AIS0.110.26

2.76 + 0.14 (height) + 0.02 (weight) − 2.44 (gender)

where gender is male = 1 and female = 0. The partial R2 values for height, weight and male sex value in this equation were 0.12, 0.25, and 0.26, and that for the final model with the three measurements was 0.63. Figure 2 shows the correlation of ureteric length with patient height.

image

Figure 2. Ureteric length correlated with measured patient height for A, women and B, men.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

The most famous study of anthropometric variables was that by Marcus Vitruvius; he believed the proportions of the human body to be perfect. An understanding of these proportions led to his three architectural principles that a structure must have: strong, useful and beautiful; architecture must mimic the perfect proportions of the human body [13]. Leonardo da Vinci’s illustration of the Vitruvian man, which we have adapted in Fig. 1, is both a combination of Vitruvius’ original description of proportions, with the addition of da Vinci’s studies of human anatomy. However, da Vinci’s Vetruvian man of proportions, while brilliant, is not an accurate depiction of true human body proportions. For example, in many cases, the human arm span is greater than a person’s height [14–16].

In the present study, we correlated values of body habitus with ureteric lengths based on Vitruvius’ and da Vinci’s theories of proportion. To minimize the patient morbidity associated with indwelling ureteric stents, both correct placing and selection of stent length are necessary. While determining the correct length of stent and stent deployment are important skills, predicting ureteric length should not rely on arbitrary variables. We found that predicting ureteric length was difficult. Gender and body variables such as height, weight, X–P and S–W distances significantly correlated with ureteric length. Although these variables correlated with ureteric length we were unable to develop a highly predictive formula for mean ureteric length that explained the variation in the mean ureteric length. However, height remained the best predictive factor for ureteric length. Unfortunately, the equation we established only predicts the correct ureteric length 26% of the time.

There was no difference between the length of the right and left ureter in the present study. This was surprising, as typically the right kidney is caudal to the left kidney, both on radiographic evaluation and during surgical and anatomical dissection [17]. By contrast with our findings, Paick et al.[6] showed a statistically significant difference of 1 cm between the right and left ureters in their 406 patients. A factor which might have contributed to these disparate findings was that in the present patients the mean BMI was 31 kg/m2; obesity might have an unforeseen effect on ureteric length. Also in the present study the ureters were measured with a ruled catheter accurate to only 1 cm; perhaps there would have been a difference if a more accurate ureteric measuring device had been used.

In most studies evaluating the ureter the optimum technique for measuring ureteric length has been debated. Using a wire or ureteric catheter has been criticised due to possible ‘bunching up’ of the redundant ureter, as described by Shah and Kulkarni [9] and Bigongiari [18]. We think that the use of a ruled ureteric catheter to measure ureteric length for the purposes of ureteric stenting is ideal, as the JJ stent itself will probably result in an equivalent ureteric contraction.

Other challenges with studies on human anthropometric measurements include established racial differences. While Asian populations might be less tall than Caucasians, the Asian trunk is longer than that of the Caucasian [19]. Indeed, the present study was limited, as 90% of the patients were Caucasian. Further investigation is needed to determine if there is a difference in mean ureteric length between ethnic groups. Until differences, if any, in ureteric length between ethnic groups are defined, the predictive formula for ureteric length is at best only valid for Caucasian men and women.

In conclusion, ureteric length is difficult to predict; in the present study, height correlated most closely with ureteric length, but height, X–P and S–W distances all significantly correlated with ureteric length. There was no difference between the length of the right and left ureter.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES