Is infundibuloureteropelvic angle (IUPA) a significant risk factor in formation of inferior calyceal calculi?

Impact of pelvicalyceal anatomical variation on surgical outcomes of endoscopic combined intrarenal surgery

Objectives

The objective of this work is to investigate the impact of the pelvicalyceal anatomical system (PCS) on calyceal stone formation and surgical outcomes of endoscopic combined intrarenal surgery (ECIRS) for renal and/or proximal ureteral stones with a diameter >15 mm.

Patients and methods

PCS was classified as Type I (single pelvis) or Type II (divided pelvis) according to the simple anatomical Takazawa classification. Using prospectively collected data from January 2016 to April 2020, 219 patients were retrospectively reviewed. After excluding patients who underwent a staged procedure, had hydronephrosis greater than grade 2, prior nephrostomy tubes, and failed to access the renal collecting system, 115 patients (Type I: 81, Type II: 34) were included, and the distribution of calyceal stones and surgical outcomes in ECIRS were compared between Types I and II PCS.

Results

The median number of renal stone calyces in the Type II group was significantly more than that in the Type I group (p = 0.016). In particular, the Type II group possessed more upper stone calyces. Multivariate logistic regression analysis revealed that Type II PCS was associated with an increased odds ratio (OR) for the presence of upper stone calyces (OR: 2.93, p = 0.018). The stone-free (SF) status at 1 month after surgery, confirmed by abdominal plain radiography, was significantly higher in the Type I group compared with that in Type II (67.9% vs. 39.4%, respectively; p = 0.006). The requirement for additional surgical interventions was significantly higher in the Type II group compared with that in Type I (35.4% vs. 7.4%, respectively; p < 0.001). Multivariate analysis revealed that the number of stone calyces (OR: 4.26; p = 0.001) and Type II PCS (OR: 3.43; p = 0.009) were independent predictors of residual stones after ECIRS.

Conclusion

We first revealed that the anatomic properties of PCS play a role in both upper calyceal stone formation and in the success of the ECIRS procedure. Because the SF rate in Type II PCS was significantly lower than that in Type I PCS, additional percutaneous nephrolithotomy tracts might be required, even for ECIRS.

InsKid-a new mobile application (app) that measures the infundibulopelvic angle before retrograde intrarenal surgery more reliably than does other approaches: pilot study

OBJECTIVE

This study compared our program's ("InsKid") capability for measuring the infundibulopelvic angle (IPA) with existing ones.

METHODS

Prospectively, data from 50 patients with lower pole kidney stones with indications for retrograde intrarenal surgery (RIRS) were collected. All patients underwent computed tomography (CT)-urography. The IPA of each pelvicalyceal (PCS) unit was measured with the Elbahnasy's, Sampaio's, and "InsKid" methods. Results were compared. Finally, we compared the area under the receiver operating characteristic (ROC) curve (AUC) for predicting stone-free status after RIRS. We defined success as stone fragments ≤ 2 mm on the CT scan on the first postoperative day (POD1). The stone-free rate refers to no identifiable stone fragments on the POD1 CT. Test-retest reliability and face validity were defined to estimate psychometric properties of InsKid.

RESULTS

The success rate after first procedure was 87.5%. The average value of IPA using the Elbahnasy and Sampaio methods and our program were 85.2° ± 11.9°, 95.1° ± 10.1°, and 79.9° ± 13.0, respectively. There was a significant difference among the InsKid, Elbahnasy, and Sampaio (AUC = 0.762, 0.601, and 0.629, respectively) approaches with respect to the capability of predicting the immediate success of RIRS. Repeated measurement did not affect values of IPA (1.3° ± 0.7, p = 0.67). All specialist appreciated proposed software as highly useful (5/5).

CONCLUSION

This new application reproduces the intraoperative aspects of the PCS more clearly than the other methods and also provides an easy solution for clearly defining the IPA without relying on the central axes.

Anatomic predictors of formation of lower caliceal calculi: is it the time for three-dimensional computed tomography urography?

OBJECTIVE

To evaluate the various anatomic factors, using computed tomography urography (CTU), that predispose to a lower-pole kidney stone formation on one side compared with the other.

MATERIALS AND METHODS

The study included 51 patients with a solitary lower-pole stone. Lower-pole infundibulopelvic angle (IPA), infundibular width (IW), infundibular length (IL), caliceal volume (CV), and number of minor calices of the affected lower calyx and normal contralateral kidney were measured based on CTU. The IPA was measured according to the methods of Sampaio and Elbahnasy. A comparison was made using multivariate analysis to determine whether any of these measurements predisposed one side to form stones.

RESULTS

The mean IPA was 80.9 degrees (Sampaio), and 52.3 degrees (Elbahnasy) on the affected kidney and 87.5 degrees (P = 0.39) and 54 degrees (P = 0.36) on the normal side. The mean IW was 2.6 mm on affected side and 3.15 mm on the normal side (P = 0.03). The mean IL was 19.7 mm and 15.3 mm (P < 0.001) on the affected and normal kidneys, respectively. Mean CV was 1123 mm(3) on affected side and 286 mm(3) on the normal side (P < 0.001). The mean number of minor calices was comparable (n = 3) on both sides with no statistical significance. Using multivariate analysis, only caliceal volume and IW sustained their significance in the final model.

CONCLUSIONS

CTU is a very useful imaging modality in the diagnosis of intrarenal anatomic variation. Larger caliceal volume and narrower IW are associated with stone formation in lower calyx.

Do Anatomic Factors Pose a Significant Risk in the Formation of Lower Pole Stones?

OBJECTIVES

To determine whether various anatomic factors predispose to a lower pole stone on one side compared with the other.

METHODS

We analyzed the intravenous urography pictures of 40 consecutive patients presenting with a single lower pole stone. Measurements were taken of the infundibulopelvic angle (IPA), ureteroinfundibular angle, infundibular width, pelvicaliceal height, infundibular length, and pelvicaliceal angle of the affected and normal kidney. The IPA was measured according to the methods of Sampaio, Bagley, and Elbahnasy. A comparison was made to determine whether any of these measurements predisposed one side to form stones.

RESULTS

The mean age was 47 years (range 20 to 80). The mean stone size was 9.2 mm (range 5 to 20). The mean IPA was 94.82 degrees (Sampaio), 56.17 degrees (Bagley), 60.40 degrees (Elbahnasy), and 49.15 degrees (Sampaio) on the affected kidney and 95.97 degrees (P = 0.66), 57.47 degrees (P = 0.57), 65.9 degrees (P = 0.04), and 54 degrees (P = 0.07) on the normal side. A statistically significant difference was found only when we measured the IPA as described by Elbahnasy. The mean infundibular width was 4.4 mm on both sides (P = 0.99). The caliceopelvic height was 21.6 mm on the affected side and 22.6 mm on the normal side (P = 0.30). The infundibular length was 28.6 mm and 27.4 mm (P = 0.16) and the caliceopelvic angle was 48 degrees and 47.6 degrees (P = 0.8) on the affected and normal kidneys, respectively

CONCLUSIONS

Lower pole anatomy as a risk factor for stones depends on the type of measurement used. A consensus should be reached to define how exactly the IPA should be measured. Other anatomic factors were not significantly different between the affected and normal side in our study.

The impact of pelvicaliceal anatomical variation between the stone-bearing and normal contralateral kidney on stone formation in adult patients with lower caliceal stones

OBJECTIVE

We aimed to investigate the effect of pelvicaliceal anatomical differences on the etiology of lower caliceal stones.

MATERIALS AND METHODS

Records of adult patients between January 1996 and December 2005 with solitary lower caliceal stone were reviewed. After exclusion of patients with hydronephrosis, major renal anatomic anomalies, non-calcium stones, history of recurrent stone disease and previous renal surgery, 78 patients were enrolled into the study. Lower pole infundibulopelvic angle (IPA), infundibulovertebral angle (IVA), infundibular length (IL), width (IW), number of minor calices and cortical thickness of the lower pole together with other caliceal variables obtained from the whole pelvicaliceal anatomy of both stone-bearing and contralateral normal kidneys were measured from intravenous pyelogram of the patients. Total pelvicaliceal volume was also calculated by a previously described formula for both kidneys.

RESULTS

There were statistically significant difference between two kidneys in terms of IW (p < 0.001) and IL (p = 0.002) of the upper calyx, IW (p = 0.001) and IVA (p < 0.001) of the lower calyx), pelvicaliceal volume (p < 0.001), IPA of middle calyx (p = 0.006) and cortical thickness over the lower pole (p < 0.001). However there was no difference between stone-bearing and contralateral normal kidneys in terms of lower pole IPA (p = 0.864) and IL (p = 0.568).

CONCLUSION

Pelvicaliceal volume but not lower caliceal properties seem to be a risk factor for stone formation in lower calyx.

Is pelvicaliceal anatomy a risk factor for stone formation in patients with solitary upper caliceal stone?

OBJECTIVES

To investigate the effect of pelvicaliceal anatomy on stone formation in patients with solitary upper caliceal stones.

METHODS

The records of patients with solitary upper caliceal stones between 1996 and 2004 were reviewed. After the exclusion of patients with hydronephrosis, major anatomic abnormalities, noncalcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones, and previous renal surgery, 42 patients (24 male, 18 female) and 42 healthy subjects (22 male, 20 female) with normal results on intravenous pyelography (IVP) were enrolled into the study. With a previously described formula, upper pole infundibulopelvic angle (IPA), infundibular length (IL) and width (IW), and pelvicaliceal volume of the stone-bearing and contralateral normal kidney of patients and bilateral normal kidneys of healthy subjects were measured from IVP.

RESULTS

Forty-two stone-bearing and 126 normal kidneys (42 contralateral, 84 healthy) were assessed. The mean stone size was 153.47 mm2 (range, 20 to 896 mm2). There were no statistically significant differences in terms of upper caliceal specifications between stone-bearing and normal kidneys. The mean (+/- standard deviation) pelvicaliceal volume of 42 stone-bearing and 126 normal kidneys was 2455.2 +/- 1380.2 mm3 and 1845.7 +/- 1454.8 mm3, respectively (P = 0.019). These values were 2114 +/- 2081.5 mm3 (P = 0.34) and 1709.5 +/- 989.1 mm3 (P = 0.001) for contralateral normal kidneys (n = 42) and normal kidneys of healthy subjects (n = 84), respectively.

CONCLUSIONS

Explanation of the etiology of the upper caliceal stone by the anatomic features is very difficult, and these caliceal anatomic variables (IPA, IL, IW) seem not to be a significant risk factor for stone formation in the upper calyx.

Renal Anatomical Factors for the Lower Calyceal Stone Formation

PURPOSE

The pathogenesis of urolithiasis is mainly explained with metabolic disorders. However metabolic disorders alone are not sufficient to explain this pathology. In the present study the anatomical differences in the lower calyceal stone formers were examined on both the stone forming and contralateral normal side. The objective was to assess the effect of lower pole renal anatomy on the lower calyceal stone formation.

MATERIALS AND METHODS

Between July 1999 and July 2004 39 patients with non-obstructed solitary lower pole stones were studied. Mean age was 47.02 years. The anatomic factors were determined on intravenous urograms (IVU). The renal length and width and the number of major and minor calices were noted. Lower pole infundibular calyceal length (ICL) and width (IW), lower infundibular length-to-width ratio were measured. The infundibulo-ureteropelvic angle (IUPA) was measured by two methods using the angle between infundibular and ureteral axes (IUPA-1), and between infundibular and ureteropelvic axes (IUPA-2). We examined a new parameter: Renal longitudinal axis-infundibulum angle (RIA) for renal stone formation. RIA was determined between two axes, including the axis connecting the central point of the pelvis opposite the margins of inferior and superior renal sinus to midpoint of renal axis and the longitudinal renal axis (Figure 2). The data of the stone forming and non-stone forming contralateral side were compared. Statistical analysis was performed by paired-t-test.

RESULTS

The IUPA-1 of the stone forming side was more acute than the non-stone forming side, in 77% of cases. The UIPA-2 of the stone forming side was more acute than the non-stone forming side, in 72% of cases. The differences with both methods between the stone forming and contralateral normal side were statistically significant (p < 0.05). Mean ICL of stone forming side was 30.20 mm whereas it was 25.51 mm in non-stone forming contralateral side. The difference between mean ICL values was statistically significant (p < 0.05). The mean infundibular length-to-width ratio was 8.55 +/- 3.25 on the stone forming side and 7.09 +/- 2.90 on the non-stone forming contralateral side. The difference between two groups was statistically significant (p < 0.05). The differences in RIA, infundibular width (IW), renal length, renal width and the number of major and minor calyces between stone forming and non-stone forming contralateral side were not statistically significant.

CONCLUSION

Anatomical disorders of lower pole collecting system may be considered as factors contributing to stone formation. IUPA (1 and 2), ICL and ICL-to-IW ratio are significantly differing factors that might predispose to lower calyceal stone formation.

Pelvicaliceal Anatomical Variation Between Stone Bearing and Normal Contralateral Kidneys—Does it Have an Impact on Stone Formation in Pediatric Patients With a Solitary Lower Caliceal Stone?

PURPOSE

We aimed to investigate the probable effect of pelvicaliceal anatomical differences between stone bearing and normal contralateral kidneys on the etiology of stone formation in children with a solitary lower pole caliceal stone.

MATERIALS AND METHODS

We reviewed the clinical records of 25 pediatric patients who underwent SWL for a solitary lower caliceal stone and 15 healthy pediatric patients who served as controls. Lower pole IPA, IL and IW, together with other caliceal variables obtained from the pelvicaliceal anatomy of the stone bearing and contralateral normal kidneys of patients with urolithiasis, and both kidneys of the control group were measured based on excretory urography. Also, total pelvicaliceal volume for both kidneys was calculated.

RESULTS

Mean LIPAs of stone bearing kidneys compared to the normal contralateral kidneys was more acute, equal and wider in 52%, 16% and 32% of the patients, respectively. Mean pelvicaliceal volumes of the stone forming and normal kidneys were 1,553.8 mm(3) (range 242 to 7,107) and 581.0 mm(3) (90 to 2,662), respectively, and there was statistical significance only in pelvicaliceal volumes between the stone bearing and contralateral normal kidneys (p <0.001).

CONCLUSIONS

Our results reveal that IPA, IL and IW of calices do not have an effect on stone formation in pediatric patients. However, large pelvicaliceal volume seems to be a significant risk factor for stone formation in the lower calix, probably because it creates abnormal urodynamic and morphological features, especially when accompanied by other metabolic abnormalities.