Elsevier

European Urology

Volume 41, Issue 4, April 2002, Pages 351-362
European Urology

Modern Approach of Diagnosis and Management of Acute Flank Pain: Review of All Imaging Modalities

https://doi.org/10.1016/S0302-2838(02)00064-7Get rights and content

Abstract

Acute flank pain is a common and complex clinical problem which might be caused by a variety of urinary and extraurinary abnormalities among which ureterolithiasis being the most frequent cause. Plain abdominal radiographs combined with intravenous urography (IVU) have been the standard imaging procedures of choice for the evaluation of acute flank pain over the last decades. Direct detection of even small ureteral calculi is achieved in 40–60%, whereas using indirect signs such as ureteral and renal pelvic dilatation stone detection is possible in up to 80–90% of all cases. However, IVU might be hampered by poor quality due to lack of bowel preparation, by nephrotoxicity of contrast agents, by serious allergic and anaphylactic reactions in 10% and 1% of the patients, respectively, and by significant radiation exposure. The use of ultrasonography (US) in the management of acute flank pain has been growing and when combining the findings of pyeloureteral dilatation, direct visualization of stones, and the absence of ureteral ejaculation, the sensitivity to detect ureteral dilatation can be as high as 96%. Recently, unenhanced helical CT (UHCT) has been introduced as imaging modality with a high sensitivity and specificity for the evaluation of acute flank pain. UHCT has been demonstrated to be superior since (1) it detects ureteral stones with a sensitivity and specificity from 98% to 100% regardless of size, location and chemical composition, (2) it identifies extraurinary causes of flank pain in about one third of all patients presenting with acute flank pain, (3) it does not need contrast agent, and (4) it is a time saving imaging technique being performed within 5 min. Based on the data published, one can predict that UHCT will become the imaging procedure of choice for evaluation of acute flank pain within the next years.

The purpose of this review is to critically evaluate the role all imaging modalities available for a modern approach of diagnosis and management of acute flank pain with regard to their sensitivity, specificity, positive and negative predictive values and their complications, toxicicty and morbidity.

Introduction

Acute flank pain is a common and complex clinical problem which might be caused by a number of urinary and extraurinary abnormalities resulting in a similar clinical picture. Ureterolithiasis appears to be the most frequent cause and affects 3–5% of the entire population in industrialized countries [20]. Renal colic is defined as acute flank pain which might radiate to the groin, lower abdomen or external genitalia due to passage of a ureteral stone, colic might be associated with nausea, vomiting, dysuria and hematuria. Since flank pain due to renal and ureteral stones is the far most common clinical presentation and the correct diagnosis of urolithiasis may not be apparent clinically, the majority of patients is referred to an urologist for further diagnosis and therapy. Following its first description in 1923, plain abdominal radiographs combined with intravenous urography (IVU) have been the standard imaging modalities in uroradiology for the evaluation of acute flank pain [54]. A calcification present on plain radiograph can be identified as ureteral stone due to its intraureteral location as it causes a filling defect or ureteral obstruction. However, IVU might be hampered by poor quality due to the lack of bowel preparation, by nephrotoxicity because of contrast agent, by serious allergic and anaphylactic reactions in 10% and 1% of the patients, respectively, and by significant radiation exposure if delayed films have to be taken [50].

During the last 20 years the place of ultrasonography (US) in the management of acute flank pain has been growing. When combining the detection of pyeloureteral dilatation, the direct visualization of the stone, and the absence of urinary ejaculation from the ureteral orifice into the bladder, the sensitivity of US for the diagnosis of ureteral obstruction is as high as 96.3% with a specificity of 100% when compared to IVU [48].

Since an ideal imaging technique for the evaluation of acute flank pain should provide information about presence or absence of pyeloureteral obstruction, size, site and composition of an ureteral stone, presence or absence of other causes of flank pain if no stone can be detected, Smith et al. [46] introduced unenhanced helical CT (UHCT) as an initial imaging technique for patients with acute flank pain who would otherwise have been referred for IVU (see Fig. 1, Fig. 2). Demonstrating a sensitivity of 100% and a specificity superior to 90% for the detection of ureteral calculi, these authors [46] concluded, that helical CT will be the imaging technique of choice for the future in patients with acute flank pain.

The purpose of this review is to critically evaluate the role of all imaging modalities being available for a modern approach of diagnosis and management of acute flank pain with regard to their sensitivity, specificity, positive and negative predicitve values and their complications, toxicity and morbidity. Furthermore, the clinical value of other diagnostic tools and imaging modalities often used in the differential diagnosis of acute flank pain such as hematuria screening and US will be evaluated.

Evaluation for hematuria is most commonly performed in patients with acute flank pain and suspected urolithiasis [5]. Studies using IVU as gold standard demonstrated a 86–100% sensitivity of hematuria screening for the detection of urinary tract calculi in patients with acute flank pain. Recently, however, studies including UHCT as gold standard, have challenged the role of hematuria screening in the diagnosis of urolithiasis [5]. Using a cut-off of more than one red blood cell (RBC) per high power field, the sensitivity of hematuria for ureterolithiasis was only 81% (Table 1). On the other hand, 40% of patients with acute flank pain and hematuria did not have urolithiasis if a definition of hematuria of greater than one RBC per high power field was used. Even if more than five RBCs were used for the definition of hematuria, 35% of the patients did not have a renal or ureteral stone. Based on the results obtained by Bove et al. [5], the clinical utility of hematuria screening is limited and the decision to perform more definitive evaluation of the patient should not be based on the presence or absence of hematuria.

US is commonly performed as primary imaging modality in patients with acute flank pain since it is a safe, rapid, inexpensive, noninvasive and repeatable technique allowing the identification of stones located in the renal pelvis and calices, at the pyelo-ureteral junction (PUJ) and at the ureterovesical junction (UVJ). Furthermore, US can detect calyceal or renal pelvic dilatation and other renal pathologies than stones. However, stones located between the PUJ and the UVJ are extremely difficult to diagnose because of technical limitations. Besides, US provides no information on calcium content of stones and is suboptimal to evaluate stone size which both are important parameters in the therapeutic decision. Therefore, the question remains open if US is helpful in the diagnostic evaluation of patients with acute flank pain and if it adds significant information not obtained by other imaging procedures.

Recently, a variety of studies have compared spiral CT, US and IVU with regard to the diagnostic accuracy to detect ureteral stones [13], [27], [32], [34], [42], [46], [47], [53]. Considering the direct visualization of ureteral stones, the sensitivity was 94%, 52% and 19% for helical CT, IVU and US, respectively [40]. Considering secondary signs of ureteral stones such as calyceal dilatation and ureteral dilatation the sensitivity of US increased to 73%. However, one has to take into account that these signs only indicate ureteral obstruction and that they are not specific for ureteral stones. Previous studies have indicated that other conditions than stone disease, may cause flank pain mimicking renal colic in up to 50% of patients [7], [10], [24], [32], [46].

On the other hand, specificity and positive predictive values of IVU and US were comparable to that of spiral CT suggesting that CT evaluation for flank pain might not be indicated to confirm the diagnosis. Sensitivity and negative predictive value, however, were quite low as compared to helical CT indicating that both techniques are not ideal to exclude ureterolithiasis and suggesting the need for helical CT to confirm the absence of stones.

A scout film of the abdomen including kidney, ureter and bladder (KUB) has a central place in the management of acute renal colic. KUB is usually taken prior to the application of intravenous contrast agents for various reasons: (1) detection of calcified stones which could be masked by the opacified urine, (2) location and size of stones, (3) assessment of bowel gas and faecal debris in the unprepared patient to decide if preparation is necessary for improvement of diagnostic accuracy. Moreover, KUB is used for the follow-up of patients presenting with small ureteral stone, which might pass spontaneously [28].

The sensitivity and specificity of KUB in stone detection ranges from 44% to 77% and from 80% to 87%, respectively, as it has been shown in a number of series comparing KUB, IVU and US [31], [40], [55]. However, with the use of UHCT these numbers have to be reassessed since CT scans detect ureterolithiasis with a sensitivity of 95–98% and a specificity of 96–100%. In this context, Levine et al. [24] correlated the findings of KUB with UHCT in patients with ureteral stone causing flank pain. In order to evaluate the value of KUB for detecting ureteral stones, the films were read under three different conditions: (a) original reading, (b) blinded retrospective reading and (c) unblinded retrospective reading comparing positive CT exams with the KUB. The highest sensitivity for stone detection obtained with KUB was 59% in the unblinded retrospective reading. The accuracy of the primary interpretation was, however, only 40% (Table 2), furthermore, it was demonstrated that the mean size of stones visualized on KUB was 4.2 mm being significantly larger than the mean size of 3.1 mm of stones not detected on KUB. The authors conclude, that KUB is of limited value for the diagnosis of ureteral stones and suggest that all patients with acute flank pain should undergo helical CT. However, the study is hampered by the fact that US did not play a role in the diagnostic evaluation of the patients. As it has been shown by Yilmaz et al. [55] the combination of US and KUB reaches sensitivity comparable to UHCT.

In another investigation, Assi et al. [1] directly compared the sensitivity of KUB with that of CT scout radiography (CT image obtained with a fixed position of the X-ray tube and similar in general appearance to a conventional projection radiography) obtained prior to helical CT scan in the same cohort of 60 patients with a single ureteral stone. Thirty-six (60%) stones were visualized on KUB whereas only 28 (47%) stones were identified on CT scout films. Furthermore, the authors demonstrated a clinically important relationship between detection rate and size on one hand, and location of a ureteral stone on the other hand (Table 3). The mean size of stones detected by KUB or CT scout films was 3.5±1.45 mm and 3.7±1.4 mm, respectively, as compared to a mean stone size of 2.2±1.2 mm and 2.3±1.3 mm, respectively, of stones not visualized. Calculus detection was strongly dependent on stone location with 86% of mid ureteral stones and about 60% of other stones being visualized by KUB, with regard to CT scout films 57% of mid ureteral stones and only about 40% of other stones were detected (Table 3). These data are substantiated by Chu et al. [8] who reported a 49% sensitivity of CT scout films to detect ureteral stones. One reason for the lower sensitivity of CT scout films might be its lower spatial resolution compared to KUB and the relatively high kilovoltage settings of 120–140 kVp used on CT scout radiography reducing the contrast between stone and soft tissue [1], [7]. It will be the task of the future to optimize CT scout radiography so that it approaches the accuracy of a KUB.

Intravenous urography has been and is still the imaging technique of choice for the evaluation of patients with renal colic [13]. Recently, the use of IVU in the diagnostic approach of acute flank pain has been challenged by a number of studies being in favor of helical CT scans as the initial diagnostic tool.

IVU has the advantage to reveal important information with regard to (1) rough estimation of renal function, (2) estimation of the degree of ureteral obstruction and demonstrating delay or absence of renal excretion as an argument for endoluminal or percutaneous drainage, (3) localization of a calculus, (4) detection of anatomical abnormalities of the collecting system and the ureter having direct impact on further management of stones, (5) detection of collecting system or ureteral tumors (see Table 4).

However, IVU also has its limitations such as (1) difficult visualization of radiolucent stones and their differentiation from other filling defects such as tumors, (2) necessity to obtain delayed films in case of severe obstruction, (3) contrast medium reactions which are reported on 5–10% of the general population and anaphylactic reactions in about one in 100,000 individuals and (4) contrast medium induced nephrotoxicity. Another shortcoming of IVU is due to the fact that contrast medium administration, because of its diuretic effect, might cause a forniceal rupture if given during an acute colic, a complication which can necessitate the placement of an endoluminal urinary diversion.

Helical CT was introduced into clinical practice in 1989 [46] In contradiction to incremental CT in which image acquisition and patient translocation occur separately, in helical CT, they occur simultaneously allowing faster acquisition of truly volumetric data thus eliminating problems with skip areas and misregistrations due to breathing as data acquisition can be performed in a single breathhold. This technique is termed helical CT because during scanning the X-ray focus describes a helical path around the patient. An important technical parameter when considering an imaging protocol using helical CT is the “pitch” (p) defined as the quotient between table motion per rotation (d) and slice collimation (s): p=d(mm)/s(mm). The higher the pitch, the larger the volume covered along the patient’s long axis during a given time interval (e.g. during one period of apnea). Indeed, it is very attractive to increase the pitch (which is similar to stretching the helix) from the theoretical value of 0 (dynamic scanning in one single scan in conventional CT) to 1 (one slice thickness per rotation) and to the most frequently used range of 1.25–2.0 or even higher. In that way a longer volume coverage and a reduced radiation dose per volume unit are obtained, however, at the expense of image quality.

In 1995, Smith et al. [46] introduced UHCT (without intravenous administration of iodinated contrast agent) as initial imaging technique for patients with acute flank pain whom would have undergone IVU. The area of examination of UHCT was specifically designed to detect urinary tract stones and extends from the upper renal poles to the vesicoprostatic junction. In their initial study comprising 20 patients, the authors achieved a direct visualization of a ureteral stone in 12 patients with UHCT and in five patients with IVU, another seven patients had ureteral obstruction on IVU without identification of a calculus. Based on these data, Smith et al. [46] suggested UHCT as the initial diagnostic imaging modality of choice, only if interventions are planned for the management of urolithiasis, an IVU should be performed to obtain additional anatomic and physiologic information. Due to this first report, a number of studies have been published investigating the clinical role of UHCT in the differential diagnosis of acute flank pain. Some of these studies were retrospective in nature [1], [2], [3], [4], [10], [11], [21], [32], [47], [53] whereas a variety of investigations have been performed as prospective evaluations comparing CT and IVU thereby better assessing the true value of UHCT versus IVU [7], [17], [27], [34], [42].

When comparing IVU with UHCT there is still an ongoing debate over the radiation dose. Whereas, some authors [10], [46] have suggested that there are no significant differences in the radiation dose between both techniques, Denton et al. have calculated that helical CT exposes the patient to radiation levels three times greater than a three-film IVU (effective radiation does of 4.7 mSv versus 1.5 mSv) [11]. Radiation dose of a CT exam will greatly vary depending on the imaging protocol used [33]. In general, the multiple scan average dose varies between 1 and 4 rad (10–40 mGy) for body scans, the acquisition of a scout scan results in a surface dose of approximately 1 mGy. Thus addition of a sequence after i.v. contrast agent administration doubles the radiation dose. Increasing the pitch from 1 to 1.5 decreases the radiation dose by one third. In a pregnant woman, concerns about a possible teratogenic effect of ionizing radiation should arise at a dose to the uterus above 20 mSv, whereas the level at which the risk of such an effect is definitively present is believed to lie between 50 and 100 mSv.

When performing UHCT to diagnose ureterolithiasis, one has to consider primary and secondary signs of urolithiasis. The identification of a calcification within the ureteral lumen or at the ureterovesical junction represents the primary sign which, however, might not be identified due to small stone diameter, volume averaging, respiratory misregistrations or due to difficult differentiation from a phlebolith [52]. Therefore, secondary signs have been described to aid the diagnosis of a ureteral stone, dilatation of the collecting system and ureter above the stone and normal ureter diameter below it, the presence of a thin circumferential rim of soft tissue (“tissue rim sign”) around the calcification (representing the ureteral wall) infiltration (“stranding”) of the perinephric and ureteral fat (representing inflammation, edema, or urinary leackage) and unilateral nephromegaly (representing renal edema) [8], [27], [42], [46]. In select cases, in which the distinction between ureteral stone and other calcifications (phlebolith or atherosclerotic plaque) is equivocal on axial images, image reformation in a curved frontal plane (following the course of the ureter) is useful to confirm that the calcification lies within the ureter. Intravenous administration of contrast agent is rarely needed to reach a conclusive diagnosis.

Miller et al. [27] prospectively compared the findings of helical CT with those of IVU in 106 patients presenting with acute flank pain (see Table 5). Stones were identified in 75 (71%) patients whereas 31 (29%) patients did have other causes contributing to acute flank pain such as musculoskeletal pain, prostatitis, renal or pelvic mass, or pyelonephritis. UHCT demonstrated a ureteral calculus either by direct identification or by secondary signs in 72/75 (96%) cases whereas the IVU was positive in only 65/75 (87%) cases. Mean size of stones not identified was 2.7 mm (2–5) and most commonly the stones were located at the ureterovesical junction. Sensitivity and specificity for the detection of ureterolithiasis were 96 and 100% for UHCT and 87 and 94% for IVU, respectively. Based on Fisher’s exact test UHCT was significantly better to predict ureteral calculi than IVU (p=0.015).

In another study, Niall et al. [34] evaluated 40 consecutive patients with acute flank pain using UHCT and IVU. A total of 28 stones were confirmed and all stones were diagnosed by UHCT whereas only 18/28 (64.2%) stones were diagnosed by IVU. However, all 28 patients demonstrated ureteral dilatation on IVU indicating ureteral obstruction as the underlying cause of flank pain. The third prospective study comparing UHCT and IVU was reported by Ruppert-Kohlmayr et al. [42] evaluating 66 consecutive patients with acute flank pain. The authors described similar results with all 52 renal and ureteral stones being correctly diagnosed by UHCT whereas only 42/52 (81%) stones were diagnosed by IVU. With regard to primary and secondary CT signs to identify ureteral stones direct detection of intraluminal calcifications and the periureteral rim sign were the most sensitive and specific parameters. Recently, Hamm et al. [17] prospectively evaluated the diagnostic value of UHCT in 125 consecutive patients with acute flank pain. Flank pain was caused by ureterolithiasis in 91 patients (72.8%), UHCT precisely identified 90/91 stones (98.9%) resulting in a sensitivity and specificity of 99% and 97%, respectively. KUB and ultrasonography had a low detection rate of ureteral stones resulting in a sensitivity and specificity of 47% and 76 as well as 11 and 97%, respectively.

The value UHCT in the management of patients with acute flank pain was furthermore evaluated in some studies without correlation to IVP findings [10], [32], [53]. All authors described UHCT as a sensitive imaging modality for the detection of urinary tract calculi and obstruction. In the study published by Dalrymphe et al. [10] among 417 patients who underwent UHCT for the evaluation of acute flank pain, 188 patients were diagnosed to have a ureteral stone. Despite the diagnosis of ureteral calculi, 90 patients (48%) had to undergo confirmatory imaging studies such as plain radiographs, retrograde urography, nephrostography or IVU to verify urolithiasis. In addition, 65 diagnoses unrelated to stone disease were found by UHCT including 22 urinary tract abnormalities and 43 abnormalities not related to the urinary tract. Vieweg et al. [53] described the results of 105 consecutive patients with acute flank pain and identified 49 patients with urolithiasis, 29 patients with other intra-abdominal findings and 21 patients with no pathological findings. The most stringent advantages of UHCT when compared to IVU appear to be its high diagnostic accuracy for the detection of urinary tract stones, its ability to diagnose other intra-abdominal diseases, and its time-saving aspect requiring only 5 minutes to establish an adequate diagnosis. Even calculi which are radiolucent on KUB such as uric acid calculi have considerably higher CT attenuation values than soft tissue and are therefore easily identified as ureteral stones. Similarily, Nachmann et al. [32] demonstrated that UHCT is accurate and rapid in detecting urinary calculus disease in patients with acute flank pain and it additionally provides the benefit of detecting noncalculous causes of flank pain in about 30% of the patients.

Besides the mere detection of ureterolithiasis, it might be possible to accurately predict the stone composition as demonstrated by Mostafavi et al. [28]. One hundred and two chemically pure stones were studied by UHCT using 1 mm thickness scanning at 2 energy levels of 80 and 120 kV. It was possible to differentiate to some extent the different stone types with uric acid stones being the only calculi, which could be distinguished without overlap from all other stones. The UHCT-based predicition of stone composition would have direct impact on further treatment, e.g. uric acid stones might be treated by urinary alkalinisation alone or by a combination therapy of ESWL and alkalinisation. However, the cited study was an ex vivo experiment so that these data have to be confirmed in clinical studies.

Based on the studies performed, there is no doubt that UHCT offers a greater accuracy and more advantages than IVU in the diagnosis of acute flank pain. However, a number of pitfalls have to be considered and there is a learning curve with the interpretation of UHCT scans in the diagnosis of acute flank pain. Especially, pelvic phleboliths are sometimes difficult to distinguish from distal ureteral stones [39], [52]. Due to their chemical composition [9], most phleboliths demonstrate a characteristic radiolucent center on abdominal radiography which, however, cannot be reproduced on UHCT scans as demonstrated recently [52]. Comparing 116 pelvic phleboliths by radiography and UHCT, 66% of the calcifications exhibited a radiolucent center on the KUB which was only the case in 1/116 phleboliths investigated by UHCT using standard soft tissue window settings, bone window settings and even pixel mapping.

Introducing UHCT into clinical practice for evaluating patients with acute flank pain, there is a small and rapid but real learning curve resulting in an approximately 5% lower sensitivity and specificity in the beginning. However, in our personal experience radiologists rapidly gain confidence in differentiating ureteral stones from vascular calicifications and arterioscloertic plaques.

Whenever a new imaging method is introduced in the routine diagnostic approach, the question of additional costs for the general health care system arises. Recently, a detailed analysis of costs for equipment, materials and related services, medical, technical and nursing staff were calculated for the different diagnostic approaches (1) UHCT as first choice, (2) KUB, IVU and US, (3) KUB, US and UHCT, and (4) IVU as first choice [16]. It was demonstrated that IVU was the most expensive procedure with 80.90 Euro followed by options (2), (3) and (1) with costs of 66.89 Euro, 64.93 Euro and 74 Euro, respectively. The authors conclude, that IVU should be abandoned as imaging modality of first choice in patients with acute flank pain. UHCT should represent the first line method not only because of lower costs but also because of the advantage to diagnose alternative diseases for acute flank pain.

Section snippets

Acute flank pain and pregnancy

Approximately 90% of pregnant women develop unilateral or bilateral ureteral obstruction by the third trimester which is asymptomatic in the majority of cases. Acute flank pain occurs in about 3% of all pregnant women [36] and might be due to various renal parenchymatous diseases, renal vascular disease, urinary calculi, pyelonephritis and pyonephrosis necessitating adequate diagnosis and therapy [14], [25]. This finding is highlighted by the fact that an incorrect diagnosis of appendicitis,

Conclusions

Based on the critical review of IVU and UHCT, the diagnostic accuracy of UHCT is significantly better than that of IVU to detect ureteral stones. Furthermore, associated contrast agent induced toxicity does not exist, radiation exposure is not significantly higher (provided care is taken to adapt the imaging protocol consequently), time to perform the imaging study is significantly less and other pathologic conditions can be detected in about one third of the patients. There is a small learning

References (55)

  • O. Niall et al.

    A comparison of noncontrast computerized tomography with excretory urography in the assessment of acute flank pain

    J. Urol.

    (1999)
  • C.S. Roth et al.

    Utility of the plain abdominal radiograph for diagnosing ureteral calculi

    Ann. Emerg. Med.

    (1985)
  • F.J.B. Sampaio et al.

    Anatomical relationship between the intrarenal arteries and the kidney collecting system

    J. Urol.

    (1990)
  • F.J.B. Sampaio et al.

    Anatomical relationship between the renal venous arrangement and the kidney collecting system

    J. Urol.

    (1990)
  • F.J.B. Sampaio et al.

    Intrarenal access: 3-dimensional anatomical study

    J. Urol.

    (1992)
  • L. Stothers et al.

    Renal colic in pregnancy

    J. Urol.

    (1992)
  • E. Svedstrom et al.

    Radiologic diagnosis of renal colic: The role of plain films, excretory urography and sonography

    Eur. Radiol.

    (1990)
  • S. Takebayashi et al.

    Computerized tomography nephrocopic images of renal pelvic carcinomas

    J. Urol.

    (1999)
  • J. Vieweg et al.

    Unenhanced helical computerized tomography for the evaluation of patients with acute flank pain

    J. Urol.

    (1998)
  • Z. Assi et al.

    Sensitivity of CT scout radiography and abdominal radiography for revealing ureteral calculi on helical CT: Implications for radiologic follow-up

    Am. J. Roentgenol

    (2000)
  • I.C. Boridy et al.

    Suspected urolithiasis in pregnant women: Imaging algorithm and literature review

    AJR

    (1996)
  • I.C. Boridy et al.

    Noncontrast helical CT for ureteral stones

    World J. Urol.

    (1998)
  • I. Boulay et al.

    Ureteral calculi: Diagnostic efficacy of helical CT and implications for treatment of patients

    Am. J. Roentgenol.

    (1999)
  • M.Y.M. Chen et al.

    Trends in the use of unenhanced helical CT for acute urinary colic

    Am. J. Roentgenol

    (1999)
  • G. Chu et al.

    Sensitivity and value of digital CT radiography for detecting ureteral stones in patients with ureterolithiasis diagnosed on unenhanced CT

    Am. J. Roentgenol

    (1999)
  • J.M. Culligan

    Phleboliths

    J. Urol.

    (1925)
  • N.C. Dalrymphe et al.

    The value of unenhanced helical computerized tomography in the management of acute flank pain

    J. Urol.

    (1998)
  • Cited by (177)

    • Management of urolithiasis

      2022, Surgery (United Kingdom)
      Citation Excerpt :

      In the acute setting, a non-contrast CT scan of the kidneys, ureter and bladder is almost always indicated, except during pregnancy or in children. Plain abdominal radiography, of kidneys, ureter and bladder (X-ray KUB): The traditional imaging modality of plain film radiography had a sensitivity and specificity of 44%–77%,6 due to the variation in the density of differing stone compositions (Table 1) and bony landmarks obscuring the stones. It cannot assess the degree of obstruction caused by the stone, and phleboliths or vascular calcifications can be confused for ureteric calculi.

    • Prevention and diagnosis of neurodegenerative diseases using machine learning models

      2022, Artificial Intelligence for Neurological Disorders
    View all citing articles on Scopus
    View full text