Renal Anatomical Factors for the Lower Calyceal Stone Formation

Do the variations in renal pelvic angles play a role in the formation of renal stone? A computed tomography study

OBJECTIVE

In this study, we aimed to investigate the effect of variations in renal pelvic angle on urinary calculi development.

MATERIALS AND METHODS

A total of 2456 unenhanced abdominal CT scans were retrospectively evaluated and 262 kidneys of 131 patients were compared. Patients included in this study were identified and qualified as follows: Having unilateral calculi, having no calculi or a history of calculi in contra-lateral side and having totally normal renal morphology.

RESULTS

The mean angle of kidneys with calculi was 55 ± 9°, while the average angle measurement was 61 ± 11° in kidneys without calculi. The mean angle measured from the kidneys with calculi was statistically smaller (p < 0.001).

CONCLUSION

Our study suggests that the possibility of calculi development in kidneys, which have more anteriorly localized pelvic angulation tends to be significantly higher in individuals, who did not have any congenital or acquired renal pathology before.

Renal axis deviation in urinary tract abnormalities of children: the role of renal scintigraphy

BACKGROUND

Urinary tract pathologies are common in children. Previous reports suggested a relationship between some renal pathologies and renal anatomic variations. This study evaluates the effect of different urinary tract abnormalities on scintigraphic renal long axis.

METHODS

Children referred to our nuclear medicine department for Tc-99m dimercaptosuccinic acid and/or Tc-99m N,N-ethylenedicysteine renal scintigraphies were entered consecutively. Presence of single, ectopic, or fused kidneys, extrarenal pathologies altering renal long axis, and history of renal surgery or advanced renal disease were used as exclusion criteria. If indicated, patients were assessed for vesicoureteral reflux (VUR). Long renal axis of each kidney was drawn with a line passing through the kidney's upper and lower poles using posterior image. The angle between this axis and patient's longitudinal body axis was defined as "renal angle." After defining age-groups, "age-corrected renal angle" was calculated.

RESULTS

A total of 311 cases (622 kidney units) entered the study (183 females, 128 males). Mean age was 41.8 months. Mean "renal angle" was 11.7, 11.9, 14.1, 17.6, 28.5, 16.7, and 19.2 degrees in normal, mild, moderate, and severe VUR, high-grade ureteropelvic junction (UPJ) obstruction, nonobstructive pelvic dilatation, and ureterovesical junction obstruction, respectively (P = 0.000). Applying receiver operating characteristic analysis and using ultrasonography as the gold standard, renal angle deviation of 13.75 degrees led to the sensitivity of 74.6% and specificity of 70.7% to detect pyelocalyceal system dilatation. Using a "renal angle" cutoff value of 18.7 degrees, 85% sensitivity and 85% specificity were achieved for the diagnosis of high-grade UPJ obstruction. Using "age-corrected renal angle," a cutoff value of 3.9 degrees was consistent with 60% sensitivity and 73% specificity for the diagnosis of severe VUR.

CONCLUSION

Considerable renal axis deviation is noted in patients with UPJ obstruction and severe VUR in children. Measurement of "renal angle" provides indirect but useful clues to the presence of urinary tract pathologies. Renal scintigraphy is a useful tool for drawing renal axis and measuring "renal angle," potentially making it useful for prediction of urinary tract system abnormalities.

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.

Lithiasis and Risk Factors

Nephrolithiasis is a worldwide disease with high clinical and economic costs. The increasing incidence in industrialized countries seems to be related to several risk factors, which are partly inherited and partly acquired. Although risk factors in urolithiasis are still under discussion, their identification would provide a notable gain for the patient in terms of stone episodes, and for the health service in terms of costs. This article presents an easy classification of risk factors based on clinical background.