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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE Table of Contents   
Year : 2010  |  Volume : 21  |  Issue : 4  |  Page : 666-672
Anatomy of the collecting system of lower pole of the kidney in patients with a single renal stone: a comparative study with individuals with normal kidneys


Urology Department, Imam Hospital, Tabriz Medical Science University, Tabriz, Iran

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Date of Web Publication26-Jun-2010
 

   Abstract 

At least 5% of women and 12% of men during their lives will experience renal colic, at least once. Many theories have been suggested for the etiology of renal stones and va­riations in the anatomy of the collecting system have been suggested to have a role in stone formation. This study was conducted to examine the role of variation of lower pole collecting system in patients with lower pole kidney stone and compared the same in normal persons (kidney donors). Investigation for the anatomy of the lower pole of the kidney (angle between lower infundibulum and pelvis, length and diameter of the infundibulum and number and pattern distribution of calyces) was carried out using intravenous pyelogram (IVP) in 100 cases with urinary stone (study cases) and 400 persons with normal kidneys (control subjects). The study was a retrospective cross-sectional case control study. Results were analyzed by Mann-Whiteny and independent sample chi square tests. The mean infundibulum-pelvic angle (IPA) in control subjects and in patients was 112.5 ± 10.7 and 96.6 ± 28.8, respectively. There was significant correlation between reduced angle and stone formation (P= < 0.001). The mean infundibulum­uretero-pelvic angle (IUPA) in control subjects and study cases was 53.5 ± 12.7 and 42.6 ± 13.4, respectively. There was significant correlation between decreased angle and stone formation (P= < 0.001). The mean length of infundibulum of lower pole of kidney (IPIL) in controls and study patients was 22.5 ± 4.1 and 27.5 ± 7.7, respectively, which was statistically significant (P< 0.001). The mean number of calyces in lower pole of the kidney (LPCN) in controls and study patients was 2.6 ± 0.6 and 3 ± 0.9, respectively, which was statistically significant (P= < 0.002). There was no significant correlation between distribution of calyces and stone formation (P= 0.366). Our study suggests that abnormal renal anatomy was more common in patients with lower pole kidney stone and should be considered a risk factor for forming lower pole kidney stone.

How to cite this article:
Zomorrodi A, Buhluli A, Fathi S. Anatomy of the collecting system of lower pole of the kidney in patients with a single renal stone: a comparative study with individuals with normal kidneys. Saudi J Kidney Dis Transpl 2010;21:666-72

How to cite this URL:
Zomorrodi A, Buhluli A, Fathi S. Anatomy of the collecting system of lower pole of the kidney in patients with a single renal stone: a comparative study with individuals with normal kidneys. Saudi J Kidney Dis Transpl [serial online] 2010 [cited 2019 Jul 20];21:666-72. Available from: http://www.sjkdt.org/text.asp?2010/21/4/666/64640

   Introduction Top


Urinary stone is the third most common di­sease of the urinary system in humans with the reported life-time incidence being 10-15%. [1] Ad­ditionally, urinary stone has a 50% chance of recurrence over 5 to 7 years. [2] At least 5% of women and 12% of men, during their life, will experience renal colic, at least once. The incidence of urinary stones is increasing in both genders; this increase coincides with the increasing incidence of artherosclerosis. [3] Many theories have been suggested to account for the etiology of urinary stones; anatomic abnormality of the collecting system has been suggested as one of the causes. [1] The role of anomalies of the collecting system of the lower pole of the kidney in clearance of urinary stone post-ESWL, has been suggested by Sampaio and Aragao in 1992. [4] We studied the anatomy of the collecting system in 400 normal persons without urinary stone (kidney donors) and compared the results with the findings in 100 patients with lower pole kidney stone.


   Materials and Methods Top


In this cross-sectional case control study, the anatomy of the lower pole of the kidney was evaluated by measuring the following para­meters: the infundibulum-pelvic angle (IPA), the infundibulum-uretero-pelvic angle (IUPA), the length and diameter of the infundibulum and the number and position of calyces. The measurements were made on a standard intra­venous pyelogram (IVP) of 400 kidney donors (controls) and 100 patients with stone in the lower pole of the kidney.

Of the 100 cases with lower pole kidney stone, there were 50 males and 50 females; all had single stone in the lower pole. The mean age was 35 ± 9.9 years and all patients were among those referred to the ESWL department over a ten-year period (1997-2007). The mean age of the 400 kidney donors (controls) was 27.8 ± 5.5 years; all underwent donor nephrectomy at the Imam Hospital between the years 1999 and 2007. After the measurements were obtained, the data were analyzed with software SPSS. Statistical analysis was performed using Mann­Whitney, independent sample T-test, paired sample T-test and chi-square test. A P value < 0.05 was considered significant.

The IPA was measured from junction of two axes, first from the lower pole infundibulum and second from the kidney pelvis [Figure 1]. The IUPA was measured from two axes; the first axis was from the infundibulum to the lower pole, while the second axis was from the center of the pelvis of the kidney [Figure 1] and [Figure 2]. The length of the lower pole infundi­bulum (mm) was measured from the lowest point of the infundibulum to the middle point in the lower edge of kidney pelvis [Figure 3]. The diameter of the infundibulum (mm) was measured in the narrowest part of the infundi­bulum [Figure 4]. All four measurements were carried out according to the method of Elbah­nasy and colleagues. [5]

The number of calyces was obtained from counting the minor calyces. Simple minor ca­lyces drain into major calyces; at times, com­plex calyceal pattern may exist in which some minor calyces connect together and then drain into major calyces and finally drain into the pelvis. [6]


   Results Top


The overall values of the various measure­ments taken are given in [Table 1]. The mean IPA was measured in both kidneys. The mean angle of control subjects was as follows: on the right side, it was 114.8 ± 12.4 degrees and on the left side, it was 110.2 ± 12.8 degrees. The difference between the two sides was significant (P< 0.001) [Table 2]. The IPA in the study patients (patients with single lower pole stone) was as follows: the mean angle in the right kidney with stone was 98 ± 29 degrees and in the left kidney with stone, it was 95.2 ± 28.4 degrees [Table 2].

In 1.8% of control subjects (donor cases with­out stone) and 38% of the study cases (cases with stone), the IPA was equal to, or less than 90 degrees. In controls, 98.2% and in study cases, 62% had angle more than 90 degrees. The overall mean angle in controls and study cases was 112.5 ± 10.7 and 96.6 ± 28.8 deg­rees, respectively. The correlation between de­creased angle (equal to, or less than 90 deg­rees) and formation of stone in lower pole was significant (P< 0.001).

The mean IUPA in the control subjects was 54.7 ± 14.7 degrees on the right side and 52.1 ± 14 degrees on the left side; the difference was significant (P= < 0.001). In the study cases, among patients with lower pole stone on the right side, the mean angle was 44.1 ± 14.3 degrees, and among patients with lower pole stone on the left side, the mean angle was 41.24 ± 12.3 degrees. In 22% of the controls and 48% of study cases, this angle was equal to, or less than 40 degrees.

Over 78% of control subjects and 52% of study cases had IUPA more than 40 degrees. Overall, the mean angle in control and study cases was 53.5 ± 12.7 and 42.6 ± 13.4 degrees, respectively. The correlation between decrease in the IUPA and stone formation in lower pole of kidney was significant (P= < 0.001).

The mean length of the infundibulum in the right and left kidneys of the controls was 22.8 ± 4.4 mm and 22.2 ± 5 mm, respectively and the difference between the two sides was significant (P= 0.008). There was no signifi­cant correlation between gender and length of the infundibulum on the right side (P= 0.74) and the left side (P= 0.833). The mean length of the infundibulum in patients with stone in the lower pole of the right kidney was 27.9 ± 9 mm and in those with stone in the lower pole of left kidney was 28.3 ± 7.4 mm. The length of the infundibulum was equal to, or more than 30 mm in 8.5% of the controls and 40% of the study cases. Overall, the mean length in con­trols and in study cases was 22.5 ± 4.1 mm and 27.5 ± 7.7, respectively and there was corre­lation between increase in the length and stone formation in lower pole of the kidney (P= 0.001).

The mean width of the infundibulum in the right and left kidneys in control subjects was 7.2 ± 1.8 mm and 6.6 ± 2 mm, respectively. Difference of size between right and left kid­neys was significant (P= < 0.001). The mean width in the right kidney of males was 7.1 ± 1.8 mm and in females was 8 ± 2 mm P= 0.036). The mean width of the infundibulum in the left kidney in males was 6.6 ± 2 mm and in females, was 7.1 ± 2 mm. On the left side, the correlation between gender and width was not significant (P= 0.93).

The mean width of the lower pole infundi­bulum in study cases with lower pole stone in the right kidney was 6.5 ± 3.4 mm and in pa­tients with stone in the left kidney, it was 6.2 ± 3.3 mm. There was no correlation between the width of the lower pole infundibulum and gender of the patients; left side stone, P= 0.741 and in patients with right side stone, P= 0.741. In 61% of the control subjects and 32% of study cases, the width was equal or less than 4 mm. Overall, the mean width in control sub­jects and study cases was 6.9 ± 1.6 mm and 6.3 ± 3.3 mm, respectively. There was significant correlation between decrease in the width of the infundibulum of the lower pole of the kid­ney and stone formation (P< 0.001).

The mean number of calyces in the control subjects was 2.6 ± 0.7 and there was no diffe­rence between kidneys on either side. The mean number of calyces of lower pole in pa­tients with right and left lower pole stone was 3 ± 1 and 30 ± 0.9, respectively. In 14% of con­trol subjects and in 23% of the study cases, the number of lower pole calyces was equal to, or more than four. Overall, the mean number of lower pole calyces in control subjects and study cases was 2.6 ± 0.6 and 3 ± 0.9, res­pectively. There was a significant correlation between the number of calyces in the lower pole of the kidney and stone formation (P= 0.002).

About 74% of control subjects had simple calyces and 26% of study cases had complex calyces; this finding was similar in the left and right kidneys. Among the study cases, 68% had simple distribution and 32% had complex distribution. Overall, 26% of control subjects and 32% of study cases had complex pattern and there was no correlation between calyceal pattern and stone formation in infundibulum of lower pole (P= 0.366).

Thus, our study revealed that four factors may have a role in stone formation in lower pole of the kidney. Of them, the IPA and dia­meter of the infundibulum were more domi­nant in the left kidney; hence, the left kidney may be more involved with stone disease. All findings are presented in [Table 1], [Table 2] and [Table 3].


   Discussion Top


Many theories have been suggested for etio­logy of kidney stone, but until this time the cause is not clear. The incidence of stones in persons with anatomic anomalies of the uri­nary tract causing obstruction or stasis of urine is high. [1] Gravity-dependent situation and unfa­vorable anatomy of the lower pole of the kidney (acute angle of the IPA and the IUPA, long length and narrow infundibulum and larger number of calyces) cause delay in transit of urine from nephron to the ureter, thus pre­disposing precipitation and crystal and stone formation. The role of the anatomy of the lo­wer pole collecting system in clearance of stone was first suggested by Sampaio and Aragao, [4] who reported that in addition to gravity, cer­tain specific anatomic conditions of lower pole of the kidney are responsible for retention of debris post-ESWL.

Gupta and colleagues reported that the unfa­vorable anatomic conditions including acute angle (less than 90 degrees), diameter of infun­dibulum less than 4 mm, and long length of infundibulum can hinder drainage of debris. [7] Elbahnasy and colleagues reported on the role of anatomy of the lower pole of the kidney in the rate of causing stone-free state post-ESWL, with IVP study. [5] We evaluated the anatomy of the lower pole collecting system in the kidney by method described by Elbahnasy and col­leagues. Sabnis and colleagues reported that infundibulum angle more than 90 degrees and width of infundibulum more than 4 mm and simple pattern of calyces are ideal for ESWL in patients with lower pole kidney stone. [6] Madbouly and colleagues, in their report, did not agree that anatomy of the lower pole had any role in clearance of stone post-ESWL. [8]

As shown in [Table 3], there was a significant difference between mean IPA, mean IUPA, mean length of lower pole infundibulum and mean width of lower pole infundibulum in normal kidney donors and patients with single lower pole kidney stone. As shown in [Table 4], the results of the study of Sampaio (study in cadavers with cause of death other than urinary system disease) were compared with our study (normal kidney donors); in both studies, more than 70% of cases had favorable anatomic con­dition. In [Table 5], the study results of Elbah­nasy (21 patients with lower pole stone) and our study (100 patients with lower pole stone) are compared; the mean IUPA was below 67 degrees, the length of lower pole infundibulum was below 35.5 mm and the mean width of lower pole infundibulum was below 8.3 mm in both studies.

Considering all these studies, in most of the patients with lower pole stone, unfavorable anatomic conditions were dominant as causa­tive factors.

In conclusion, our study showed that unfa­vorable anatomic condition is more common in patients with lower pole stone than in nor­mal persons without stone (kidney donors) thus raising the question as to whether unfavorable anatomic condition in collecting system of lo­wer pole of the kidney should be considered a risk factor for stone formation. Further studies of the lower pole collecting system with tri dimension-CT and metabolic evaluation, in larger number cases are recommended.

 
   References Top

1.Wein JA, Kavoussi RL, Novick CA, Partin WA, Peters CA. Urinary lithiasis. In: Margaret SP: Campbell-Walsh Urology, 9 th edition. Saunders, Philadelphia, 2007:1363-92.  Back to cited text no. 1      
2.Asplin JR, Favus MJ, Coe FL. Nephrolithiasis. In: Brenner BM: Brenner and Rector's the kid­ney, 5th edition. Saunders, Philadelphia, 1996: 1893-5.  Back to cited text no. 2      
3.Stoller ML, Meng MV, Abraham HM, Kane JP. The primary stone event: a new hypothesis involving a vascular etiology. J Urol 2004;171: 1920-4.  Back to cited text no. 3      
4.Sampaio FJ, Aragao AH. Inferior pole collec­ting system anatomy: its probable role in extracorporeal shock wave lithotripsy. J Urol 1992;147:322-4.  Back to cited text no. 4  [PUBMED]    
5.Elbahnasy AM, Shalhav AL, Hoenig DM, et al. Lower calyceal stone clearance after shock wave lithotripsy or ureteroscopy: the impact of lower pole radiographic anatomy. J Urol 1998; 159:676-82.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]  
6.Sabnis RB, Naik K, Patel SH, et al. Extracorporeal shockwave lithotripsy for lower calyceal stones: can clearance be predicted? Br J Urol 1997;80:853-7.  Back to cited text no. 6  [PUBMED]    
7.Gupta NP, Singh DV, Hemal AK, Mandal S. Infundibulopelvic anatomy and Clearance of calyceal with shockwave lithotripsy. J Urol 2000;163:24-7.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]  
8.Madbouly KH, Sheir KZ, Elsobky E. Impact of lower pole renal anatomy on stone clearance after shock wave lithotripsy: fact or fiction? J Urol 2001;165:1415-8.  Back to cited text no. 8      

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Correspondence Address:
Afshar Zomorrodi
Urology Department, Imam Hospital, Tabriz Medical Science University, Tabriz
Iran
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PMID: 20587870

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

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