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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2010  |  Volume : 21  |  Issue : 3  |  Page : 488-493
The role of B-Mode ultrasonography in the detection of urolithiasis in patients with acute renal colic


Department of Radiology, Jordan University Hospital, Amman, Jordan

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Date of Web Publication26-Apr-2010
 

   Abstract 

This study was conducted to assess the diagnostic yield of B-Mode Ultrasonogra­phy compared to unenhanced helical CT scan in detecting urinary stones in patients with acute renal colic. This retrospective study comprised of 156 patients who underwent unenhanced uri­nary tract CT scan and ultrasonography for suspicion of urolithiasis. Both techniques were used to determine the presence or absence, site, size, and number of urinary stones, as well as presence of any other intra-abdominal pathology. For statistical analysis, the sensitivity, specificity, predictive values, and diagnostic accuracy of ultrasonography were measured considering unenhanced CT scan as a gold standard. Unpaired two-tailed student's t-test was used for comparison between mean size of true positive, false positive, and false negative stones. There were 68 patients having 115 urinary stones. Ultrasound identified 54 stones, missed 43, and falsely diagnosed 18 stones. The mean size of true positive, false positive, and false negative stones were 4.8 ± 3.3 mm, 6 ± 1.8 mm and 4.18 ± 3 mm, respectively. There were 23 patients with other intra-abdominal patho­logies, equally detected by both techniques. Ultrasound helped in identifying the cause of acute flank pain in 62% of cases. The overall sensitivity, specificity, positive and negative predictive values, and accuracy of ultrasonography in the diagnosis of renal stone disease were 58%, 91%, 79%, 78%, and 78% , respectively. Our study suggests that, despite its limited value in detecting urinary stones, ultrasonography should be performed as an initial assessment in patients with acute flank pain. Unenhanced helical CT should be reserved for patients in whom ultrasonography is inconclusive.

How to cite this article:
Haroun AA, Hadidy AM, Mithqal AM, Mahafza WS, Al-Riyalat NT, Sheikh-Ali RF. The role of B-Mode ultrasonography in the detection of urolithiasis in patients with acute renal colic. Saudi J Kidney Dis Transpl 2010;21:488-93

How to cite this URL:
Haroun AA, Hadidy AM, Mithqal AM, Mahafza WS, Al-Riyalat NT, Sheikh-Ali RF. The role of B-Mode ultrasonography in the detection of urolithiasis in patients with acute renal colic. Saudi J Kidney Dis Transpl [serial online] 2010 [cited 2020 Oct 30];21:488-93. Available from: https://www.sjkdt.org/text.asp?2010/21/3/488/62740

   Introduction Top


Acute renal colic is a common clinical problem and the investigation modalities have under­gone transformation in the last decade, so that the choice of an initial diagnostic method is not always clear, particularly when there is a contraindication to radiation exposure or, to intravenous injection of iodinated contrast ma­terial.

Plain radiograph of the kidney, ureters, and urinary bladder (KUB) lacks sensitivity for ra­diolucent stones, and it is of low specificity particularly when pelvic phleboliths are pre­sent. [1] Intravenous urography (IVU) was consi­dered the radiological method of choice for a long time in patients with acute renal colic as it allows both morphological and functional evaluation of the urinary system. [2],[3],[4],[5] It was con­sidered to carry a low sensitivity in patients with small stones, in stones with low atenua­tion value, and in patients with air-distended bowel. [6]

Urinary tract ultrasonography (US) is a widely used imaging method as it is safe, rapid, com­fortable to patients, and relatively of low cost compared to the IVU and the computerized to­mography (CT) scan. The sensitivity of US for detection of urinary calculi is widely variable in the literature depending on the site and size of calculus, and on the patient morphology. [7],[8]

By the end of last century, unenhanced he­lical CT scan (UHCT) was introduced as a new imaging modality by Smith et al [9] for depiction of urinary stones, and was well accepted as an alternative method to IVU. [10] Nowadays, it is considered as the imaging modality of choice for this clinical entity. [11],[12],[13],[14] Radiation dose, aces­sibility, and high cost compared to US repre­sent main limitations of this technique.

The objectives of our retrospective study were to determine the role of B-Mode US in detecting urinary calculi and to compare its diagnostic accuracy with the UHCT scan.


   Materials and Methods Top


One hundred fifty six patients, who under­went UHCT scan and US for suspicion of uro­lithiasis from January 2008 to August 2008, were retrospectively reviewed. There were 102 male patients with a mean age of 51 ± 16 years, and 54 female patients with a mean age of 46 ± 18 years.

UHCT scan was performed with a Somatom Plus 4 machine (Siemens, Germany). The ima­ges were obtained with the patient in supine position during breath-hold plus quiet brea­thing. The explored area extended from the up­per poles of both kidneys down to pubic sym­physis using five mm collimation with a table speed of 7.5 mm/second giving a pitch of 1.5:1. The images were obtained with a 0.75-second gantry rotation using 120 KVp and 206 mA giving 155 mAs. Multiplanar reformation (MPR) in coronal oblique direction was used when the location of stone was uncertain. CT scan ima­ges were reported by consultant radiologists on hard copy films.

Ultrasound examinations were performed by the trans-abdominal approach for all patients, after ensuring a full urinary bladder, using 3.5 or 5MHz probes. The kidneys were evaluated in the longitudinal and transverse projections. Whenever possible, the course of ureters was also followed down to the urinary bladder with special attention to the uretero-vesical junc­tion. The urinary bladder was also examined in both planes.

Both UHCT and US were performed to de­termine the presence or absence, site, size, and number of urinary stones as well as presence of ureteric and/or pelvicalyceal system dilata­tion. Any other renal or extra-renal pathology was also registered.

The patients were classified into three groups according to visualization of urolithiasis: Group­A with urolithiasis seen on both UHCT and US, Group-B with urolithiasis seen only on CT scan, and Group-C with urolithiasis seen only on US.

The sensitivity, specificity, positive and ne­gative predictive values, and diagnostic accu­racy of US were measured considering UHCT as a gold standard. Unpaired two-tailed student's t-test was used to determine the presence of statistically significant difference in the mean size of true positive, false negative, and false positive stones as demonstrated on UHCT.


   Results Top


There were 68 patients having 115 renal stones seen on either, or both techniques. There were 47 male patients with mean age of 50 ± 17 years, and 21 female patients with a mean age of 46 ± 19 years. The number of patients in Groups-A, B, and C were 34 (66 stones), 25 (33 stones), and nine patients (16 stones), res­pectively. Ultrasound allowed identification of 54 stones (47%): 19 out of 34 right renal stones, 24 out of 30 left renal stones, one out of 11 right ureteral stones, zero out of eight left ureteral stones, and 10 out of 14 urinary bladder stones. Ultrasound falsely demonstrated 18 stones in 11 patients: 12 stones in the right kidney, five stones in the left kidney, and one in the left ureter. The mean size of true positive, false negative, and false positive urinary stones were 4.8 ± 3.3 mm, 4.18 ± 3 mm and 6 ± 1.8 mm, respectively.

Among patients in Group-A, US detected 54 stones in 21 patients, missed 13 stones in 11 patients and falsely diagnosed two stones in two patients. The site and size of true positive stones included: 19 stones of 5.6 ± 3.2 mm in the right kidney, 24 stones of 4.8 ± 2.8 mm in the left kidney, one stone of 3 mm in the right ureter, and 10 stones of 7.9 ± 2.4 mm in the urinary bladder. The site and the mean size of missed stones were: two stones of 5 ± 4 mm in the right kidney, five stones of 4 ± 2 mm in the left kidney, four stones of 6 ± 2 mm in the right ureter, and two stones of 4 mm in the left ureter. The site and mean size of falsely diag­nosed stones were one stone of 7 mm in the right kidney, and one stone of 5 mm in the left kidney. Regarding dilatation of the ureter and/ or pelvicalyceal (PC) system, both techniques were similarly effective in all cases. They were normal and dilated in 28 and six patients, res­pectively.

Among patients in Group-B, US missed 33 stones in 25 patients. The site and mean size of the missed stones were: 11 stones of 4.6 ± 4 mm in the right kidney, eight stones of 5 ± 4.5 mm in the left kidney, six stones of 3.5 ± 2 mm in the right ureter, five stones of 3 mm in the left ureter, and three stones of 7 ± 4 mm in the urinary bladder. No false positive stones were registered in this group.

Regarding dilatation of the ureter and/or PC system, both techniques demonstrated dilated PC system in four patients and ureteral dilata­tion in one patient. UHCT scan only showed dilated PC system in two patients while US only showed dilated PC systems in three pa­tients without demonstrating the cause of obs­truction.

Among patients in Group-C, US falsely de­monstrated 12 stones in nine patients. The site and size of these stones were: seven stones of 4 ± 2.5 mm in the right kidney, four stones of 3 ± 0.5 mm in the left kidney, and one stone of 8 mm in the left ureter.

Regarding ureteric and/or PC system dilata­tion; US showed dilated PC system in one pa­tient, and dilated ureteral and PC system in one other patient. In the first patient, US demons­trated a stone of 5 mm in the right kidney, and in the second patient, a stone of 8 mm at the left uretero-vesical junction. UHCT was nor­mal in these two cases.

Both techniques were equally effective in de­monstrating associated intra-abdominal patho­logy in the three patient-groups. Renal patho­logy other than renal stone disease was found in 11 patients: four patients had renal mass, five patients had urinary bladder tumor, one patient had pyelo-ureteric junction obstruction, and one patient had urinoma.

Extra-renal pathology was incidentally detec­ted in 12 patients. There were seven patients with gallstones, two patients with rectal tumor, one patient with splenic infarction, one patient with ovarian cyst, and one patient with pan­creatic pseudocyst.

The sensitivity, specificity, predictive values, and accuracy of B-mode US in detecting uri­nary stones are shown in [Table 1]. The sensiti­vity, specificity, and accuracy of US in detecting ureteral calculi were 6%, 99%, and 88%, respectively. For renal stones, these rates were 49%, 89%, and 76%, respectively.

Statistical analysis revealed a significant dif­ference between false positive and false nega­tive stones (P = 0.04), while no significant dif­ference was found between true positive and false negative stones, and true positive and false positive stones (P= 0.3, and 0.16, respectively).


   Discussion Top


The diagnosis of acute renal colic is usually based on clinical history, and physical and la­boratory examinations. Radiological investiga­tions are reserved for those with atypical his­tory or when interventional procedure or fol­low-up examinations are required.

In this decade, UHCT has gained a large ac­ceptance and is considered the imaging me­thod of choice in many centers in patients with suspected urinary calculus. The published sen­sitivity and specificity of UHCT in acute ure­teral colic were 96% and 100%, respectively. [15] On the other hand, the use of US as a scree­ning test in these patients has become less practiced. [16]

Our results and other published reports de­monstrated that the sensitivity and specificity of US in detecting urolithiasis were better for renal than for ureteral calculi. [7],[16],[17] These rates in our study were 49% and 89% for renal cal­culi, and 6% and 99% for ureteric calculi, res­pectively.

The US identified 64% and 59%, of right and left renal stones with a corresponding specifi­city of 95% and 97%, respectively and, that was higher than other reports. [7],[18] The better vi­sualization of right than left renal stones could be related to the lower position of the left kidney and to the interposition of splenic fle­xure, that may represent a barrier to a satisfac­tory visualization of the left kidney.

Although US missed 38% of renal stones and was falsely positive in 12.5% of cases, we did not find a statistically significant difference between the mean size of true positive and false negative renal stones (P = 0.3). Some au­thors [7] found that the sensitivity of US is de­pendent on the size of the calculus, as the mean size of stones detected on US in their patients was higher than that in our patients (7 versus 4.8 mm). Renal calculi can be missed on US because of absence of the characteristic associated acoustic shadowing; the mean size of renal stones in our study was relatively small. Indeed, five stones larger than 10 mm were not visualized on US and this could be related to either patient being overweight or, to the presence of bowel distension. Thirteen of 14 falsely diagnosed urinary stones were pro­ved to be located in the kidneys; we think that was also related to the presence of hyper­echoic foci without acoustic shadowing.

We found that US is of limited value in de­tecting ureteral calculi and that was in agree­ment with other studies. [14],[19] The major weak­ ness of US is its inability to examine the entire course of the ureter particularly in the absence of ureteral dilatation. However, US allowed ex­clusion of renal stone disease in 88 patients (56%) yielding a 91% specificity, and 78% accuracy.

Dilated ureteric and or PC system was identi­fied in two patients on US without direct visua­lization of the obstructive agent. In these pa­tients, UHCT scan demonstrated ureteral stones in both patients. On the other hand, dilated PC system on UHCT was shown in four patients with no evidence of obstructing agent. In one patient, US performed one week after the UH­CT scan demonstrated one stone in the urinary bladder; in another patient, PUJ obstruction was diagnosed, and in the other three patients the causative agent was not identified. It is well known that dilated ureteric and PC sys­tem could be related to other non-obstructive diseases such as vesico-ureteral reflux, and malignant or inflammatory ureteral stricture.

Our results demonstrated that 67% of ureteral stones detected on UHCT and/or US were not associated with dilated PC system. It had been reported that in early obstructive uropathy, no

dilatation of PC system could be found, [19],[20],[21] and a lag period of three hours is usually re­quired to build-up a significant back pressure to induce PC system dilatation. [19] The intro­duction of Duplex Doppler US may improve identification of ureteral obstruction by measu­ring the intra-renal resistive index. In a pre­vious study, it was found that the resistive in­dex was related to excretion delay in cases of complete obstruction, for which it was higher in non-excreting than in delayed-excreting kid­neys. [21] In addition, Duplex Doppler US can depict urinary obstruction earlier than B-mode US, which can miss cases of urinary obstruc­ tion without PC system dilatation. [21],[22],[23],[24]

The limitations of the present study were re­lated to its retrospective nature and to absence of a fixed imaging protocol. We think that this was responsible for high false negative rate in our study; thus, stones detected on UHCT might have been passed spontaneously at the time of US; particularly because, the mean size of uri-nary stones in our patients was less than 5 mm and studies have demonstrated that ureteral stones less than 5 mm may pass spon­ taneously. [12],[25]

Both techniques were similar in identifying the presence of extra-urinary pathology, and that was in agreement with other studies. [11],[12],[26] The prevalence of intra-abdominal pathology other than renal stone disease was 15% and that was within the wide reported range (2.5% - 57%). [6],[8],[27],[28]

Five of 14 urinary bladder stones were mis­sed on US, and this could be related to hyper­distended urinary bladder that could not be completely explored, presence of reverbation artefacts, or to small size of stones. In our study, the mean size of missed and truly diag­nosed stones was 3 mm, and 9.8 mm, respec­tively.


   Conclusion Top


Ultrasonography is less accurate than UHCT scan in detecting renal stone disease, and both techniques have a similar ability to detect other intra-abdominal pathology. US can depict causes of acute flank pain in 62% of cases, is usually available in any radiology center and allows a safe and non-invasive examination, particularly in children and in pregnant pa­tients. It is relatively inexpensive compared to UHCT. In our hospital, the cost of UHCT scan is five times that of US. Despite its limited value in detecting urinary stones, we advocate the use of US as an initial screening exami­nation in patients with acute flank pain as it permits reducing the cost of radiological inves­tigations by 50%. UHCT should be reserved for patients in whom US is inconclusive.

 
   References Top

1.Koelliker SL, Cronan JJ, Acute urinary tract obstruction. Imaging update. Urol Clin North Am 1997;24:571-83.  Back to cited text no. 1      
2.Dalla Palma L, Stacul F, Bazzochi M, Pagnan L, Festini G, Marega D. Ultrasonography and plain film versus intravenous urography in ureteric colic. Clin Radiol 1993;47:333-6.  Back to cited text no. 2      
3.Otal Ph, Irsutti M, Murat C, et al. Radiological exploration of renal colic. J Radiol 2001;82:27­-33.  Back to cited text no. 3      
4.Tamm E, Silverman P, Shuman W. Evaluation of the patient with flank pain and possible ureteral calculus. Radiology 2003;228:319-29.  Back to cited text no. 4      
5.Liu W, Esler S, Kenny B, Goh R, Rainbow R, Stevenson G. Low-dose non enhanced helical CT of renal colic: Assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-4.  Back to cited text no. 5      
6.Wang J, Shen S, Huang S, Chang C. Prospec­tive comparison of unenhanced spiral computed tomography and intravenous urography in the evaluation of acute renal colic. J Chin Med Assoc 2008;71:30-6.  Back to cited text no. 6      
7.Fowler K, Locken J, Duchesne J, Williamson M. US for detecting renal calculi with nonenhanced CT as a reference standard. Radiology 2002; 222:109-13.  Back to cited text no. 7      
8.Kobayashi T, Nishizawa K, Watanabe J, Ogura K. Clinical characteristics of ureteral calculi de­tected by nonenhanced computerized tomogra­phy after unclear results of plain radiography and ultrasonography. J Urol 2003;3:799-802.  Back to cited text no. 8      
9.Smith RC, Rosenfield AT, Choe KA, et al. Acute flank pain: Comparison of non-contrast­enhanced CT and intravenous urography. Radiology 1995;194:789-94.  Back to cited text no. 9      
10.Pfister SA, Deckart A, Laschke S, et al. Un­enhanced helical computed vs intravenous uro­graphy in patients with acute flank pain: Accuracy and economic impact in a rando­mized prospective trial.~ Eur Radiol 2003;13 (11):2513-20.  Back to cited text no. 10      
11.Mitterberger M, Pinggerra G, Pallwein L, et al. Plain abdominal radiography with transabdo­minal native tissue harmonic imaging ultras­onography vs unenhanced computed tomo­graphy in renal colic. BJU Int 2007;4:887-90.  Back to cited text no. 11      
12.Ripolles T, Agramunt M, Errando J, Martinez MJ, Coronel B, Morales M. Suspected ureteral colic: Plain film and sonography vs unenhanced helical CT: A prospective study in 66 patients. Eur Radiol 2004;1:129-36.  Back to cited text no. 12      
13.Wong SK, Ng LG, Tan BS, et al. Acute renal colic: Value of unenhanced spiral computed tomography compared with intravenous uro­graphy. Ann Acad Med Singapore 2001;6:568­-72.  Back to cited text no. 13      
14.Yilmaz S, Sindel T, Arslan G, et al. Renal colic: Comparison of spiral CT, US and IVU in the detection of ureteral calculi. Eur Radiol 1998;2:212-7.  Back to cited text no. 14      
15.Ah Ryu J, Kim B, Jeon Y, et al. Unenhanced spiral CT in acute ureteral colic: A replacement for excretory urography? Korean J Radiol 2001;1:14-20.  Back to cited text no. 15      
16.Sheafor D, Hertzberg B, Freed K, et al. Non­enhanced helical CT and US in the emergency evaluation of patients with renal colic: Prospective comparison. Radiology 2000;217: 792-7.  Back to cited text no. 16      
17.Vrtiska TJ, Hattery RR, Charboneau JW, et al. Role of ultrasound in medical management of patients with renal stone disease. Urol Radiol 1992;3:131-8.  Back to cited text no. 17      
18.Ulusan S, Koc Z, Tokmac N. Accuracy of sonography for detecting renal stone: Compa­rison with CT. J Clin Ultrasound 2007;5:256­-61.  Back to cited text no. 18      
19.Haddad M, Sharif H, Shahed M. Renal colic: Diagnosis and outcome. Radiology 1992;184: 83-8.  Back to cited text no. 19      
20.Andersen R, Wegner HE. Intravenous uro­graphy revisited in the age of ultrasound and computerized tomography: Diagnostic yield in cases of renal colic, suspected pelvic and abdominal malignancies, suspected renal mass, and acute pyelonephritis. Urol Int 1997;4:221-6.  Back to cited text no. 20      
21.Haroun A. Duplex Doppler sonography in pa­tients with acute renal colic: Prospective study and literature review. Int Urol Nephrol 2003; 35:135-40.  Back to cited text no. 21  [PUBMED]  [FULLTEXT]  
22.Rodgers PM, Bates JA, Irving HC. Intrarenal Doppler ultrasound studies in normal and acutely obstructed kidneys. Br J Radiol 1992; 771:207-12.  Back to cited text no. 22      
23.Platt JF, Rubin JM, Ellis JH. Acute renal obs­truction: evaluation with intrarenal duplex Doppler and conventional US. Radiology 1993; 3:686-8.  Back to cited text no. 23      
24.Platt JF. Looking for renal obstruction: The view from renal Doppler US. Radiology 1994; 2:143-8.  Back to cited text no. 24      
25.Veno A, Kawamura T, Ogawa A, Takayasu H. Relation of spontaneous passage of ureteral calculi to size. Urology 1977;10:544-6.  Back to cited text no. 25      
26.Patlas M, Farkas A, Fisher D, Zaghal I, Halpern H. Ultrasound vs CT for the detection of ureteric stones in patients with acute renal colic. Br J Radiol 2001;74: 901-4.  Back to cited text no. 26      
27.Ahmad NA, Ather MH, Rees J. incidental diagnosis of disease on un-enhanced helical computed tomography performed for ureteric colic. BMC Urol 2003;3:2-6.  Back to cited text no. 27  [PUBMED]  [FULLTEXT]  
28.Kirpalani A, Khalili K, Lee S, Haider M. Renal colic: Comparison of use and outcomes of un­enhanced helical CT for emergency inves­tigation in 1998 and 2002. Radiology 2005; 236:554-8.  Back to cited text no. 28      

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Correspondence Address:
Azmi A Haroun
Department of Radiology, Jordan University Hospital, P.O. Box 460495, 11946 Amman
Jordan
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    Tables

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