Ureteral Thickness Research Articles

Ureteral wall thickness and distal ureteral density in patients with residual fragments after Ho:YAG laser semi-rigid ureterolithotripsy.

Recent data suggest that greater ureteral density distal to ureteral stones or increased ureteral wall thickness (UWT) can predict impacted stones. The aim of our study was to evaluate if patients with residual fragments present with greater ureteral density and larger UWT when compared to stone-free patients. From January onward, a consecutive series of patients undergoing semi rigid Ho:YAG laser ureterolithotripsy (ULT) for ureteral stones were enrolled. A non-contrast enhanced computed tomography (CT) scan was performed before the procedure to evaluate distal ureteral density (DUD) and wall ureteral thickness (UWT) at the site of ureteral stones. Patients with residual fragments were compared to stone-free patients using a matched-pair analysis (1:1 scenario). Cases were matched sequentially using the following criteria: age, gender, body mass index (BMI), stone length, hydronephrosis, location of stones, and mean Hounsfield unit (HU) of the stone. Overall, 160 patients were enrolled, mean age was 57.9 ± 14years, mean BMI was 25.8 ± 4kg/m2, mean length of the stone was 10.6 ± 4.9mm, and mean UWT was 1.4 ± 1.6mm. A total of 150/160 (94%) patients presented hydronephrosis; mean HU stone was 868 ± 327; mean DUD was 54 ± 17.8 HU. Ureteral distal density (51.7 vs 56.6; p = 0.535) and ureteral distal thickness (1.39 vs 1.54; p = 0.078) were similar in both groups of patients. In our study, the evaluation of distal ureteral density does not predict stone-free rate. Further studies should evaluate the role for preoperative computer tomography in predicting surgery outcome.

SC213 - Ureteral thickness and distal ureteral density do not predict stone free rate in patients treated with HO: laser semi-rigid ureterolithotripsy

SC213 - Ureteral thickness and distal ureteral density do not predict stone free rate in patients treated with HO: laser semi-rigid ureterolithotripsy

Non-invasive preoperative assessment of ureteral stone impaction using peri-calculus ureteral thickness on Non-Contrast CT (NCCT) scan: A prospective Study

Background: Ureteral stone can be measured on the NCCT scan as peri-calculus ureteral thickness. If this depicts significant calculus impaction, the patient could be counseled regarding intra-operative risk and incomplete stone clearance. The present study was planned to evaluate the use of NCCT in patients with ureterolithiasis for the prediction of a favorable clinical outcome. Materials and methods: Patients who underwent ureterorenoscopy for ureteric calculus with pre-operative NCCT scan were included and intraoperative data were recorded. Operating surgeons were blinded for proximal ureteric wall thickness (p-UWT), peri-calculus ureteric wall thickness (p-CUT), and distal ureteric wall thickness (d-UWT) values. The guidewire was negotiated before each URS. Stone was considered impacted if guidewire could not be negotiated in 2 attempts. Intra-operative stone impaction score (SIS) assigned on a scale of 0 (dislodged spontaneously), 1 (dislodged with saline pressure), 2 (dislodged after lithotripsy), 3 (fragments impacted in edema) and 4 (open). Intra-operative findings were correlated to preoperative NCCT measurements of ureteral thickness. Other variables like duration of symptoms, hydronephrosis, stone size in the longest dimension, and stone location were also recorded. Results: Of total patients 108 patients, 70 patients had non-impacted calculus and 38 patients had impacted calculus. Patients with an impacted calculus had significantly higher p-UWT (9.76 ±3.11mm), p-CUT (6.82±2.57mm), and d-UWT (6.26±2.28mm) as compared to non-impacted. There was a positive correlation in SIS with p-UWT, p-CUT, and p-DWT in both impacted and non-impacted groups. Conclusion: Pre-operative ureteric wall thickness in proximal, peri, and distal to calculus can predict intraoperative risk and impaction of calculus.

Peri-Calculus Ureteral Thickness on Computed Tomography Predicts Stone Impaction at Time of Surgery: A Prospective Study.

Introduction and Objectives: Ureteroscopic management of impacted ureteral stones poses multiple challenges. We examined whether ureteral thickness measured on preoperative noncontrast computed tomography (CT) is predictive of stone impaction at the time of ureteroscopy (URS). Methods: Thirty-eight patients with preoperative CT scan and undergoing URS for ureteral stones were prospectively studied. Ureteral thickness directly above, around (peri-calculus ureteral thickness [P-CUT]), and below the calculus were determined on CT scan. The cross-sectional surface area around the stone (P-CUT) was also calculated. Stones were considered impacted at surgery if contrast had difficulty passing, a guidewire could not pass, and the stone was visually impacted >5 on a Likert scale. The surgeon determining intraoperative impaction and the individual measuring the ureteral thickness on CT were blinded. Results: Fourteen of the 38 patients were found to have an impacted ureteral stone at the time of surgery. Patients with an intraoperative finding of an impacted stone had significantly higher ureteral thickness above, around (P-CUT), below the calculus, and P-CUT surface area with all four p-values <0.001. P-CUT surface area was independently predictive of impaction at the time of surgery on multivariate analysis. A mean P-CUT of 6.1 and 1.6 mm and P-CUT surface area of 92.6 and 15.4 mm2 were noted for the impacted and nonimpacted stones, respectively. Conclusion: Ureteral thicknesses above, around (P-CUT), and below the calculus are readily measurable on CT scan. P-CUT surface area can also be calculated for a stronger representation of ureteral thickness. These four parameters are predictive of ureteral stone impaction and useful for surgical planning and patient counseling.

SC245 - Ureteral thickness and distal ureteral density do not predict stone free rate in patients treated with ho: Yag laser semi rigid ureterolithotripsy

SC245 - Ureteral thickness and distal ureteral density do not predict stone free rate in patients treated with ho: Yag laser semi rigid ureterolithotripsy

Intravesical tunnel length to ureteral diameter ratio insufficiently explains ureterovesical junction competence: A parametric simulation study

In 1959, Paquin recommended a tunnel length five times the diameter of the ureter to prevent vesicoureteral reflux (VUR) during ureteral reimplants. In 1969, Lyon et al. challenged Paquin's conclusions and proposed that the ureteral orifice was more important than the intravesical tunnel for UVJ competence. It is not known if the two mechanisms of UVJ competence (tunnel length and UO spatial orientation) are interdependent or if one is more critical. Although in clinical practice Paquin's rule has stood the test of time, classical mechanics of materials would predict more coaptation (less reflux) with larger diameter ureters and this contradicts Paquin's rule. The aim of this study was to test Paquin's tunnel length theory by parametrically modeling the ureterovesical junction (UVJ) to determine variables critical for ureteral closure. LS-DYNA finite-element simulation software was use to model ureteral collapse (Figure). Intravesical tunnel length, ureteral diameter, ureteral thickness and ureteral stiffness were all modeled. Changes in the pressure required to collapse the ureter were studied as each variable was changed on the model. The modeled ureteral orifice was not affected by changes in bladder volume (in a real bladder, bladder distention would pull the ureteral office open) and had no constraints (which could occur by suturing the ureteral orifice to a stiff bladder). As predicted by classical mechanics of materials, the pressure required to collapse the ureter was inversely related to its diameter. Above 1 cm tunnel length, pressures required to collapse a ureter did not decrease by any significant amount. Increasing ureteral thickness or ureteral stiffness did increase the pressure required to collapse the ureter, but only significantly for ureteral thicknesses not commonly seen in practice (i.e. wall thickness of 2.5 mm in a 6.4 mm ureter). Our model showed that for most ureters seen in clinical practice (3-30 mm in diameter), and when the ureteral orifice is not constrained by the bladder mucosa, a 1 cm tunnel would allow the ureter to collapse under low pressures. Contrary to Paquin's belief, larger diameter ureters collapsed more easily. It is important to understand that our model's main limitation was that it did not study the effects of the ureteral orifice, which in light of our findings must play an important role in preventing reflux as suggested by Lyon et al., in 1969. For example, a 3 cm ureteral orifice sutured to the bladder mucosa would be difficult to collapse as the bladder distends and pulls open the orifice. One way of compensating for a difficult to collapse ureteral orifice would be creating a larger diameter tunnel, but another would be to create a better ureteral orifice, perhaps by narrowing the diameter of the UO (distal ureteral tapering) and making it protrude into the bladder like a volcano (i.e. advancement sutures, or creating an intravesical nipple). We hope that this new understanding of the variables involved in ureterovesical junction competence can lead to further refinement in our surgical techniques to correct vesicoureteral reflux.