Which is the best method to estimate the actual ureteral length in patients undergoing ureteral stent placement?

Preoperative estimate of natural ureteral length based on computed tomography and/or plain radiography

To predict natural ureter lengths based on clinical images. We reviewed our image database of patients who underwent multiphasic computed tomography urography from January 2019 to April 2020. Natural ureteral length (UL_CTU) was measured using a three-dimensional curved multiplanar reformation technique. Patient parameters including age, height, and height of the lumbar spine, the index of ureteral length using kidney/ureter/bladder (KUB) radiographs (C-P and C-PS) and computed tomography (UL_CT) were collected. UL_CTU correlated most strongly with UL_CT. R square and adjusted R square values from multivariate regression were 0.686 and 0.678 (left side) and 0.516 and 0.503 (right side), respectively. UL_CTU could be estimated by the regression model in three different scenarios as follows:

UL_CT + C-P

UL_CTUL = 0.405 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× UL_CTL\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 0.626 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× C-P_L – 0.508 cm

UL_CTUR = 0.558 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× UL_CTR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 0.218 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× C-P_R + 6.533 cm

UL_CT

UL_CTUL = 0.876 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× UL_CTL\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 6.337 cm

UL_CTUR = 0.710 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× UL_CTR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 9.625 cm

C-P

UL_CTUL = 0.678 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× C-P_L\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 4.836 cm

UL_CTUR = 0.495 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document}× C-P_R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$+$$\end{document}+ 10.353 cm

We provide equations to predict UL_CTU based on CT, KUB or CT plus KUB for different clinical scenarios. The formula based on CT plus KUB provided the most accurate estimation, while the others had lower validation values but could still meet clinical needs.

Management of proximal migration of double-J stents after Anderson-Hynes pyeloplasty in children

INTRODUCTION

Proximal migration of double J stents after pediatric pyeloplasty is rare. Although retrograde removal of migrated stents is more common, the small calibre of the pediatric ureter may necessitate antegrade retrieval. Many techniques are described for the same in adults however, pediatric literature is sparse. We aim to describe the management of proximally displaced stents after pediatric pyeloplasty.

MATERIALS AND METHODS

This retrospective study included all children (<17 years age) who underwent retrieval of proximally displaced DJ stents after pyeloplasty between 2007 and 2019 at a single institution. The retrograde technique employed ureteroscopic retrieval with a grasper while in the antegrade technique, an access sheath was placed percutaneously into a calyx and Nephroscopic retrieval was performed.

RESULTS

There were 8 children (6 boys and 2 girls) of which 4 were infants. Median age was 3.5 (0.5-12) years and median follow-up was 7.5 (4-47) months. Two children had been referred with displaced stents after pyeloplasty from other centres. The incidence of proximal stent migration was 6/1644 (0.4%). Open pyeloplasty had been performed in seven while one child had undergone laparoscopic pyeloplasty. The lower coil of the migrated stent was in the renal pelvis in 6 (complete) and ureter in 2 (partial migration). Those with partial migration underwent successful ureteroscopic retrieval. Three infants required Antegrade stent removal while ureteroscopic retrieval was successful in an older child with complete stent migration. Nephrectomy for loss of function and redo pyeloplasty for pelvi-ureteric stricture was performed in one each. One child had self-limiting fever (Clavien 1) after stent removal. All had normal drainage on renogram after 6 months. The cause of proximal stent migration was likely to be an inadequate lower coil (<180°) in 5 children and a capacious pelvis with narrow ureter in one infant. The cause could not be ascertained in two children who were referred from other centres. The management algorithm for retrieval of proximally migrated DJ stents, is depicted in Fig. 3.

CONCLUSIONS

Proximal migration of DJ stent after pyeloplasty is a rare complication which may be safely managed with a stepwise approach using both Antegrade and retrograde techniques. Accurate stent length, adequate distal coil and appropriate placement are essential to avoid stent migration.

Korean ureter length: A computed tomography-based study

Purpose

We measured ureter length in healthy Koreans using reformatted computed tomography (UL_CT) and found ways to indirectly estimate ureter length by measuring LL_CT, the length between the ureteropelvic junction and the ureterovesical junction, and standing and sitting height.

Materials and Methods

A total of 508 ureters of 254 healthy patients (median age, 55.0 years; 148 males and 106 females) were included in this retrospective study. UL_CT, LL_CT, and sitting and standing body height were measured.

Results

The mean left and right UL_CT were 25.2±2.2 and 25.0±2.2 cm, respectively. The mean left and right LL_CT were 21.1±1.8 and 20.3±1.9 cm, respectively. Standing and sitting body height were 164.1±8.9 and 88.3±4.3 cm, respectively. Height was significantly correlated with UL_CT, but this relation was not linear (r²=0.064 standing height, 0.062 sitting height). However, LL_CT showed a significant linear correlation with UL_CT (r²=0.485). UL_CT can be estimated indirectly by the following equation: UL_CT=0.823×LL_CT+8.093.

Conclusions

We could measure the ureteral length of healthy Koreans by UL_CT. UL_CT could be estimated indirectly by LL_CT and standing and sitting height. Of these variables, LL_CT provided the most accurate estimate of ureteral length.

Computed tomograpy evaluation of ureteral length in children

INTRODUCTION

Although ureteral length (UL) is highly variable in children, reliable data on this topic are scarce. During urinary tract surgery, the use of an inappropriately dimensioned ureteral stent is associated with adverse effects. This study aimed to evaluate UL as a function of the child's age, using contrast-enhanced computed tomography (CT) of the abdomen and pelvis, and to calculate a new equation for predicting UL (and thus the optimal length of ureteral stents) in children.

MATERIAL AND METHODS

A retrospective, single-centre study of children (younger than 16 years) who are free of abdominal mass syndrome and severe scoliosis was conducted. After three-dimensional reconstruction of the CT data, the ureter was measured between the ureteropelvic junction and ureterovesical junction by two observers. The lengths of the right and left ureters were analyzed by age, with at least 10 CT measurements per age class.

RESULTS

The mean ULs on the right and left were, respectively, 9.7 and 9.91 cm before the age of 1 year, 20.10 and 21.08 cm at the age of 7 and 26.55 and 27.46 cm at the age of 16. The interobserver reproducibility of UL determination was high (intraclass correlation coefficient [95% confidence interval]: 0.97 [0.94-0.99]). On the basis of these results, the length of the double-J catheter should be equal to the child's age +12 cm (Table 1).

CONCLUSION

Computed tomography measurement of the UL in healthy children is reproducible and reliable and enabled the estimation of the UL by age group. This knowledge should facilitate the choice of the stent used in ureteral surgery. To confirm the study results, the stent size suggested here should be evaluated in routine practice.

[Is the ureteral length associated with the patient's size?]

OBJECTIVE

To assess the relation between the ureteral length and the patients' size.

PATIENTS AND METHOD

Prospective study made between September 2012 and May 2014, on 87 patients with 42 men and 45 women, in whom the ureteral measure was performed during the various procedures that require the use of a pigtail stent. The average age of the population was 53 years old (±15.9) with an average height of 168.3cm (±8.4). This has been achieved through ureteral catheter combining fluoroscopy and endoscopy.

RESULTS

The ureteral average length was 23.5cm (±2.33). The ureteral average length was 23.8cm (±2.18) for man and 23.2cm (±2.44) for women. In this population, there were a positive correlation between the size of the patients and the length of the ureters (r=0.75; P=0.01). However, this correlation was not found in all subgroups, particularly among women (r=0.16; P=0.30) and on the right side of men (r=0.34; P=0.12). This correlation was still true for the left side in the men's group (r=0.50; P=0.02).

CONCLUSION

In this study, there is a positive correlation between the patients' size and the ureteral length. But this correlation is not found in some subgroups. It is better to perform in vivo the ureteral measurement to have the precise length in order to set up a pigtail stent adapted to the patient.

LEVEL OF EVIDENCE

3.

Cystoscopic ureteral stent placement: techniques and tips

INTRODUCTION AND HYPOTHESIS

We present a video demonstrating technical considerations and tips for cystoscopic placement of external, lighted, and internal ureteral stents.

METHODS

Cystoscopic ureteral stent placement is useful in cases where difficult pelvic periureter dissection is expected or encountered. In this video, we review cystoscopy basics, our approach to various types of retrograde stent placement, and performing retrograde pyelograms. Traditional external ureteral stent and lighted stent placement for prophylactic purposes are discussed, with attention to understanding stent markings, appropriate resistance, and steps for externalization. Internal, double-J ureteral stent placement with the use of fluoroscopy is initiated with placement of a guidewire. An open-ended ureteral catheter is advanced over the wire in the pelvic portion of the ureter, and a retrograde pyelogram is performed. The wire is reintroduced and the stent advanced to the renal pelvis under fluoroscopy. The proximal curl is confirmed to be in the appropriate position with fluoroscopy. The string attached to the stent is then cut and removed, the guidewire is removed, and the stent is deployed with the distal curl in the bladder.

CONCLUSIONS

This video reviews key steps for cystoscopic ureteral stent placement in a prophylactic setting, cases of challenging anatomy, or ureteral injury.

Intraoperative Radiographic Determination of Ureteral Length as a Method of Determining Ideal Stent Length

INTRODUCTION

Accurate determination of ureteral length (UL) and appropriate stent length remains a challenge. The objective of this study was to describe an intraoperative technique to measure UL and determine appropriate stent length, and to compare this technique with other methods of determining appropriate stent length.

METHODS

Patients undergoing ureteroscopy requiring postoperative stenting and who had a preoperative CT were prospectively identified. Gender, age, height, body mass index, L1 to L5 lumbar height on CT, and surgeon's estimate of UL were recorded. UL was measured using four methods: direct measurement with a ureteral catheter, ureteropelvic junction (UPJ) to ureterovesical junction distance on axial and coronal CT, and using a novel intraoperative radiographic technique. Radiographic measurement was performed using a radiographic nipple marker affixed to the skin over the ureteral orifice (UO) and an angiographic catheter with radiopaque markings at 1 cm intervals. UL was the distance from the UPJ to the marker at the UO measured using the catheter markers. Correlation between direct measurement and the recorded variables and methods of ureteral measurement were calculated. Stent length was chosen based on radiographic measurement. Stents were deemed of appropriate length if they showed a proximal coil in the renal pelvis and a distal coil in the bladder without crossing midline.

RESULTS

Twenty-five ureters from 23 patients were included. Radiographically measured UL was strongly correlated with direct measurement. (r = 0.873, p < 0.01). Coronal and axial CT ULs were significantly associated with direct measurement (p < 0.05). Height, lumbar height, and surgeon's estimate of UL were not. Stents were deemed of appropriate length in 23/25 cases (92%).

CONCLUSIONS

This new method for radiographic UL measurement is strongly correlated with directly measured UL. A length of stent chosen based on radiographic UL resulted in an appropriate stent length.

Developing a preoperative predictive model for ureteral length for ureteral stent insertion

BACKGROUND

Ureteral stenting has been a fundamental part of various urological procedures. Selecting a ureteral stent of optimal length is important for decreasing the incidence of stent migration and complications. The aim of the present study was to develop and internally validate a model for predicting the ureteral length for ureteral stent insertion.

METHODS

This study included a total of 127 patients whose ureters had previously been assessed by both intravenous urography (IVU) and CT scan. The actual ureteral length was determined by direct measurement using a 5-Fr ureteral catheter. Multiple linear regression analysis with backward selection was used to model the relationship between the factors analyzed and actual ureteral length. Bootstrapping was used to internally validate the predictive model.

RESULTS

Patients all of whom had stone disease included 76 men (59.8%) and 51 women (40.2%), with the median and mean (± SD) ages of 60 and 58.7 (±14.2) years. In these patients, 53 (41.7%) right and 74 (58.3%) left ureters were analyzed. The median and mean (± SD) actual ureteral lengths were 24.0 and 23.3 (±2.0) cm, respectively. Using the bootstrap methods for internal validation, the correlation coefficient (R2) was 0.57 ± 0.07.

CONCLUSION

We have developed a predictive model, for the first time, which predicts ureteral length using the following five preoperative characteristics: age, side, sex, IVU measurement, and CT calculation. This predictive model can be used to reliably predict ureteral length based on clinical and radiological factors and may thus be a useful tool to help determining the optimal length of ureteral stent.

Best Stent Length Predicted by Simple CT Measurement Rather than Patient Height

INTRODUCTION AND OBJECTIVES

Ureteral stent length is important, as stents that are too long might worsen symptoms and too short are at higher risk of migration. The purpose of this study was to determine if patient or radiologic parameters correlate with directly measured ureteral length and if directly measured ureteral length predicts proper stent positioning.

METHODS

During stent placement, ureteral length (ureteropelvic junction to ureterovesical junction distance) was directly measured by endoscopically viewing a ureteral catheter (with 1-cm marking) emanating from the ureteral orifice. A 22, 24, or 26 cm stent was chosen to be closest to the measured ureteral length. For ureters >26 cm, a 26 cm stent was chosen. Ends of an "ideally positioned" stent were fully curled in the renal pelvis and bladder, without crossing the bladder midline. Rates of ideal stent position were compared between patients with matching stent and ureteral lengths and those with stent lengths differing by ≥1 cm (mismatched). The measured ureteral length was correlated with patient height, L1-L5 height, and length measured on CT.

RESULTS

Fifty-nine ureters from 57 patients were included. Height was reasonably correlated with L1-L5 height (Spearman correlation coefficient [rho] = 0.79), although both were poorly correlated with directly measured ureteral length (rho = 0.18 for height and 0.32 for lumbar height). Ureteral lengths measured on CT correlated well with direct measurement (rho = 0.63 for axial cuts and rho = 0.64 for coronal cuts). Matched stent length was associated with higher rates of ideal stent position than mismatched (100% vs 70.9%, p = 0.006).

CONCLUSIONS

CT measurements, rather than height, correlate well with measured length and could be used to choose the appropriate stent length. Stents matching directly measured ureteral lengths are associated with high rates of ideal stent position.

Verification of relationships between anthropometric variables among ureteral stents recipients and ureteric lengths: a challenge for Vitruvian-da Vinci theory

Objective

To determine and verify how anthropometric variables correlate to ureteric lengths and how well statistical models approximate the actual ureteric lengths.

Materials and methods

In this work, 129 charts of endourological patients (71 females and 58 males) were studied retrospectively. Data were gathered from various research centers from North and South America. Continuous data were studied using descriptive statistics. Anthropometric variables (age, body surface area, body weight, obesity, and stature) were utilized as predictors of ureteric lengths. Linear regressions and correlations were used for studying relationships between the predictors and the outcome variables (ureteric lengths); P-value was set at 0.05. To assess how well statistical models were capable of predicting the actual ureteric lengths, percentages (or ratios of matched to mismatched results) were employed.

Results

The results of the study show that anthropometric variables do not correlate well to ureteric lengths. Statistical models can partially estimate ureteric lengths. Out of the five anthropometric variables studied, three of them: body frame, stature, and weight, each with a P<0.0001, were significant. Two of the variables: age (R²=0.01; P=0.20) and obesity (R²=0.03; P=0.06), were found to be poor estimators of ureteric lengths. None of the predictors reached the expected (match:above:below) ratio of 1:0:0 to qualify as reliable predictors of ureteric lengths.

Conclusion

There is not sufficient evidence to conclude that anthropometric variables can reliably predict ureteric lengths. These variables appear to lack adequate specificity as they failed to reach the expected (match:above:below) ratio of 1:0:0. Consequently, selections of ureteral stents continue to remain a challenge. However, height (R²=0.68) with the (match:above:below) ratio of 3:3:4 appears suited for use as estimator, but on the basis of decision rule. Additional research is recommended for stent improvements and ureteric length determinations.

Office-based stone management

As hospital resources are becoming strained, ambulatory surgical centers and day hospitals are being increasingly utilized. For the urologist, a working knowledge of local anesthetics and conscious sedation protocols are important, as many surgical kidney-stone procedures can be performed without general anesthetic. With any anesthesia, the key goal is to maximize patient comfort while minimizing respiratory depression and avoiding prolonged sedation. When using these medications, a working knowledge of emergency reversal, ventilation (bag mask/laryngeal mask airway/intubation), and cardiopulmonary resuscitation is recommended.