Spiral Computerized Tomography in the Evaluation of Acute Flank Pain: A Replacement for Excretory Urography

Chapitre A - Lithiase et vessie neurogène

Stones of the upper and lower urinary tract are frequently observed in spinal cord injury patients. In this article, the authors reviewed the literature to identify the most reliable tools for diagnosis and follow-up. A review of recently published series demonstrated an excess risk of kidney and bladder stones in this population. The authors discuss the possible measures of prevention and identification of high-risk groups likely to benefit from more intensive follow-up.

Role of Helical Nonenhanced Computed Tomography in the Evaluation of Acute Flank Pain

OBJECTIVE

To evaluate the role of helical nonenhanced computed tomography (NECT) in the diagnosis of acute flank pain.

METHODS

Seventy-five consecutive patients were analysed retrospectively for profile, loin pain, urine analysis and NECT findings. Diagnostic accuracy of NECT for urolithiaisis was calculated. The value of combined microhaematuria and NECT in the diagnosis of flank pain was also highlighted. The potential for identifying phleboliths and alternative diagnoses on NECT was also explored.

RESULTS

There were 46 males and 29 females with an average age of 42.2 years. Forty-four patients presented with acute left flank pain. NECT carries a sensitivity and specificity of 96% for the diagnosis of stone disease. Combined with microhaematuria, NECT has 100% accuracy in picking up urinary tract stones.

CONCLUSION

NECT is the first imaging investigation of choice for the evaluation of patients presenting to the emergency department with flank pain and suspected renal colic.

Imaging for percutaneous renal access and management of renal calculi

Percutaneous renal stone surgery requires detailed imaging to define stone burden and delineate the anatomy of the kidney and nearby organs. It is also essential to carry out safe percutaneous access and to assess postoperative outcomes. The emergence of CT as the imaging modality of choice for detecting renal calculi and the ability of CT urography with or without three-dimensional reconstruction to delineate the collecting system makes this the most versatile and sensitive imaging modality for pre- and postoperative evaluation. At present, intravenous urogram continues to play an important role in the evaluation of patients considered for percutaneous nephrostolithotomy. Fluoroscopy re-mains the mainstay of intraoperative imaging, although ultrasound is a useful alternative. Selection and application of appropriate imaging modalities for patients undergoing per-cutaneous nephrostolithotomy enhances the safety and success of the procedure.

Alternate or Additional Findings to Stone Disease on Unenhanced Computerized Tomography for Acute Flank Pain Can Impact Management

PURPOSE

We evaluated the incidence and clinical relevance of alternate or additional findings on unenhanced CT in patients with acute flank pain and suspected urinary calculi.

MATERIALS AND METHODS

A consecutive series of 1,500 patients underwent unenhanced CT due to acute flank pain. The absence or presence of urinary tract calculi and their localization were recorded. Alternate or additional CT findings were classified according to whether they required immediate or deferred treatment, or were of little or no clinical importance.

RESULTS

Of the 1,500 patients 1,035 (69%) had urinary tract calculi, including 309 (30%) with nephrolithiasis, 377 (36%) with ureterolithiasis and 349 (34%) with the 2 conditions. Urolithiasis alone was found in 331 of these patients (32%) and additional pathological conditions were noted in 704 (68%). Of all patients 1,064 (71%) had other or additional CT findings. Of all patients 207 (14%) had nonstone related CT findings requiring immediate or deferred treatment, 464 (31%) had pathological conditions of little clinical importance and 393 (26%) had pathological conditions of no clinical relevance. CT was normal in 105 of all patients (7%).

CONCLUSIONS

Unenhanced CT in patients with acute flank pain allows the accurate diagnosis of urinary stone disease and it can also provide further important information leading to emergency or deferred treatment in a substantial number of patients.

Imagerie de la lithiase urinaire : « Trois en un »

Urinary lithiasis is very common among the general population, with a high prevalence level. In rich countries it is mainly located inside the upper urinary tract. Helical CToperated with newer devices is the most accurate modality to provide all needed information: diagnosis of stone without contrast medium injection, morphology (size, number) and localization, diagnosis of urinary obstruction, urinary tract aspect and all kind of differential diagnosis in emergency. It must be used during follow up to diagnose residual fragments. Multiplanar reconstructions are essential for the clinicians; but diagnosis is interpreted by scrolling axial views with dynamic analysis on computer screen. Low-dose helical CT is today available. Helical CT provides an "all-in-one" examination. It should soon replace combined plain film-ultrasonography performed in an emergency context of renal colic and intravenous urography for pre- and post-treatment assessments.

Is there a role for the intravenous urogram in the 21st century?

Over the last two decades, there have been major advances in methods of medical imaging that have brought great benefits to patients both for diagnosis and for treatment. There has been an increasing tendency for some of these new imaging modalities to be dependent on highly sophisticated technology. The belief has developed amongst doctors who use these techniques that newer is necessarily better. Just as patients (and some doctors) now often believe that anything done with a laser represents the best that can be offered, so there is a tendency to demand that newer techniques in imaging should always be offered as the preferred option. In urological practice that philosophy is questionable.

[Imaging techniques and their impact in treatment management of patients with acute flank pain]

The purpose of this overview is to provide a general summary of the imaging techniques applied at the Vienna Hospital for the investigation of acute flank pain and the diagnosis of stone disease and the evaluation of their efficacy and impact on therapy management. The number of publications on the issue of "intravenous urography (IVU) vs computed tomography (CT)" is abundant; in recent years, advocates of CT make up the majority. In the Department of Urology at the Vienna Hospital, conventional techniques such as ultrasound and IVU besides UHCT still play an important role. This overview presents the advantages and disadvantages of the various imaging techniques for diagnosis of stone disease and evaluates their significance regarding therapy management of patients with acute flank pain.

Non-contrast computerized tomography (NCCT) and dynamic renal scintigraphy (DRS) in the patients with refractory renal colic

OBJECTIVES

To assess the importance of combined use of non-contrast computerized tomography (NCCT) and dynamic renal scintigraphy (DRS) in evaluation of patients with refractory flank pain in the emergency department.

METHODS

The study involved 64 consecutive patients with refractory renal colic. All patients were evaluated with plain abdominal films kidneys, ureters and bladder (KUB), NCCT and DRS. We assessed the accuracy of different diagnostic procedures and their combinations; in addition, we determined their importance for different steps of evaluation.

RESULTS

Urololithiasis was diagnosed in 76.6% (n=49) of the patients. Twenty-nine percent of calculi were > 4 mm. Surgical intervention were performed in 20 patients (40.8%). A combination of NCCT plus DRS yielded the greatest sensitivity (96%) in establishing final diagnosis, however clinical, laboratory and KUB data in combination with DRS, yielded greater specificity (93%) and PPV (97%). Sex (male), WBC (mean 10.2 x 10(3) +/- 3.1) and KUB (calculus > 4 mm) were chosen in the three-step multi-variant analysis, while only male sex was found to be the strongest predictor (p<0.056) of necessity to perform NCCT. In making decision for definitive treatment NCCT and DRS provided the most important information about stone size and obstruction (kappa=0.734, p<0.001 and kappa=0.625, p<0.001), while DRS was selected as the most important diagnostic procedure in the emergency department (kappa=0.527, p<0.001).

CONCLUSIONS

In the emergency department, DRS combined with the results of clinical investigation may indicate candidates for hospitalization with emergency intervention. Immediate NCCT must be strongly considered in men with WBC> or =10 x 10(3) and calculi > 4 mm on the KUB.

Unexplained renal colic: What is the utility of IV contrast?

PURPOSE

The aim of this study was to evaluate the benefit of intravenous (IV) contrast in patients with suspected renal colic and unremarkable unenhanced MDCT.

MATERIALS AND METHODS

One thousand two hundred and four patients with suspected ureterolithiasis were evaluated with unenhanced MDCT. Seven hundred and eight patients that had additional imaging following IV contrast were our study group.

RESULTS

Of the patients, 9.4% (67/708) had abnormalities seen only on contrast-enhanced exams. In 53.1% (376/708) of the patients, no additional finding was identified after IV contrast.

CONCLUSION

IV contrast in patients with renal colic is rarely helpful.

Renal Colic: Comparison of Use and Outcomes of Unenhanced Helical CT for Emergency Investigation in 1998 and 2002

PURPOSE

To determine retrospectively whether there had been any change between 1998 and 2002 in the use and outcome of computed tomography (CT) performed in the emergency department for patients presenting with symptoms of renal colic.

MATERIALS AND METHODS

Approval from the Research Ethics Board was obtained, and informed consent was waived. All CT examinations ordered from the emergency department of a tertiary care hospital and performed from July to December 1998 and July to December 2002 were identified. Reports were reviewed, and results were categorized as either (a) positive for urinary tract calculus disease (category I), (b) indicative of an alternate diagnosis (category II), or (c) negative for findings to account for the patient's symptoms (category III). The corresponding emergency department charts were reviewed for urine dipstick results for hematuria and for patient history of stone disease. For statistical analysis, chi2 testing and odds ratios were used.

RESULTS

During the 6-month period in 1998, 179 CT examinations were performed in patients who were admitted to the emergency department. During the same period in 2002, 234 CT examinations were performed. After correction for the total number of emergency department visits, it was determined that there was a relative increase of 21.3% (95% confidence interval: -0.0009, 0.47) in number of CT examinations performed in the emergency department. A total of 117 (65.4%) of 179 CT studies in 1998 and 153 (65.4%) of 234 CT studies in 2002 demonstrated renal calculus disease (category I), nine (5.0%) of 179 CT studies in 1998 and 17 (7.3%) of 234 CT studies in 2002 were used to identify an alternate diagnosis for patient symptoms (category II), and 53 (29.6%) of 179 CT studies in 1998 and 64 (27.4%) of 234 CT studies in 2002 were negative (category III). There were no significant differences between the rates of category I, II, or III results and the positivity rates for hematuria and urinary tract stone history during 1998 and 2002.

CONCLUSION

Despite a definite trend of increased CT use during 1998 and 2002, there was no significant decrease in the rates of positive renal colic results or alternate diagnoses.

Value of Ultrasonography and Helical Computed Tomography in the Diagnosis of Stone-Free Patients after Extracorporeal Shock Wave Lithotripsy (USG and Helical CT after SWL)

AIM

To define the value of different radiologic modalities in determining the patients who believed to be stone-free after extracorporeal shock wave lithotripsy (SWL) with plain abdominal X-ray, by evaluating the same patients with ultrasonography (USG) and helical computed tomography (CT).

PATIENTS AND METHODS

Between March 2002 and February 2003, 76 patients with urolithiazis who were treated with SWL and considered to be stone-free with plain abdominal X-ray, were evaluated with USG and helical CT. The results were compared for the accuracy of the stone-free diagnosis.

RESULTS

Residual stones were detected in 9 (11.8%) with USG and in 17 (22.3%) with CT of 76 patients who were thought to be stone-free with plain abdominal X-ray alone.

CONCLUSIONS

Although plain abdominal X-ray has been accepted as the first line diagnostic tool in the follow-up after SWL with its cheap and practical use, helical CT was found to be more valuable in diagnosis of residual stone fragments which has not been found in plain abdominal X-ray. If we take these considerations which can change our clinical approach and patient follow-up into account, we believe that the routine use of helical CT can give more accurate information in patient controls after SWL.

Clinical impact of incidental diagnosis of disease on non-contrast-enhanced helical CT for acute ureteral colic

The role of un enhanced helical CT (UHCT) in the evaluation of acute flank pain suggestive of urinary tract calculi is increasingly appreciated in the last few years. Recent studies have identified the advantages of UHCT in recognizing alternative findings within or outside the urinary tract. These incidental diagnoses on UHCT alter a patient's management and demonstrate the pivotal role of UHCT in rapidly triaging these patients for appropriate management. Clinical impact of incidental diagnoses is maximal in identifying alternate emergent conditions mimicking reno-ureteric colic and in identifying malignancies at an early stage when they are potentially curable.

Renal ultrasound

Renal US is one of several imaging modalities available to the EP in the evaluation of patients with acute urologic disorders. It offers excellent anatomic detail without exposure to radiation or contrast agents but is limited in its assessment of renal function. It is an important alternative to helical CT scanning for evaluating renal colic, especially in children and pregnant women. It has an important role in excluding bilateral renal obstruction as the cause of acute renal failure. It is likely that Doppler renal US also will take on a prominent role in the evaluation of renal vascular disorders. It already has become the standard of care in the management of renal transplant patients. Bedside emergency renal US performed and interpreted by EPs with limited training and experience is increasing in use and gaining acceptance. At present, the primary role of renal US is to identify hydronephrosis in patients with renal colic or acute renal failure but, in the future, its role likely will expand as technology advances and its use increases. In many patients, bedside renal US may obviate the need for further diagnostic workup and speed the diagnosis and treatment of an emergency patient.

Spiral computed tomography: Role in determination of chemical compositions of pure and mixed urinary stones—an in vitro study

OBJECTIVES

To determine the chemical composition of pure and mixed urinary calculi by multislice helical computed tomography (CT) in an in vitro setting. CT is becoming the preferred radiologic examination in diagnosis and management of calculus disease. The management of calculus disease can be facilitated by ascertaining the stone composition. Unnecessary shock wave treatment could be avoided if the fragility of the stones could be predicted at diagnosis.

METHODS

A total of 107 stones (86 pure and 21 mixed) were measured in a multislice helical scanner within an air-filled environment. The scans were performed at two energy levels, 80 kV and 120 kV, with a 1-mm slice thickness. The chemical compositions of the urinary stones were assessed on the basis of the differences in the densities measured in Hounsfield units. The stones were assigned to six different groups according to the density measured in Hounsfield units: uric acid, struvite, cystine, calcium phosphate, calcium oxalate monohydrate, and calcium oxalate dihydrate.

RESULTS

The differences in the density measured by multislice helical CT at 120 kV for the six groups of pure stones were statistically significant. The densities of the different regions within the mixed stones were also significantly different statistically from each other. The densities of the different regions measured in the mixed stones were not different from the densities of the corresponding pure stones. This finding supports the idea that different chemical compositions within a stone can be identified by their densities measured by multislice helical CT.

CONCLUSIONS

The chemical compositions of both pure and mixed stones can be determined by multislice helical CT in an in vitro setting. The feasibility of in vivo determinations remains to be clarified.

DIAGNOSIS OF URETERAL OBSTRUCTION IN PATIENTS WITH COMPROMISED RENAL FUNCTION: THE ROLE OF NONINVASIVE IMAGING MODALITIES

We compared the role of noncontrast computerized tomography (NCCT), magnetic resonance urography (MRU), and combined abdominal radiography (KUB) and ultrasonography (US) in the diagnosis of the cause of ureteral obstruction in patients with compromised renal function.

MATERIALS AND METHODS

The study included 149 patients, of whom 110 had bilateral obstruction and 39 had obstruction of a solitary kidney. Therefore, the total number of renal units was 259. All patients had renal impairment with serum creatinine greater than 2.5 mg/dl. Besides conventional KUB and US all patients underwent NCCT and MRU. The gold standard for diagnosis of the cause of obstruction included retrograde or antegrade ureterogram, ureteroscopy and/or open surgery. The sensitivity, specificity and overall accuracy of NCCT, MRU, and combined KUB and US in the diagnosis of ureteral obstruction were calculated in comparison with the gold standard.

RESULTS

The definitive cause of ureteral obstruction was calculous in 146 and noncalculous in 113 renal units, including ureteral stricture in 65, bladder or ureter in 43, extraurinary collection in 3 and retroperitoneal fibrosis in 2. The site of stone impaction was identified by NCCT in all 146 renal units (100% sensitivity), by MRU in 101 (69.2% sensitivity), and by combined KUB and US in 115 (78.7% sensitivity) with a difference of significant value in favor of NCCT (p <0.001). Ureteral strictures were identified by NCCT in 18 of the 65 cases (28%) and by MRU in 54 of 65 (83%). Bladder and ureteral tumors causing ureteral obstruction could be diagnosed in approximately half of the patients by NCCT (22 of 43) and in all except 1 by MRU (42 of 43). NCCT and MRU could identify all extraurinary causes of obstruction. Overall of the 113 kidneys with noncalculous obstruction the cause could be identified by MRU in 101 (89% sensitivity), by NCCT in 45 (40% sensitivity), and by combined KUB and US in only 20 (18% sensitivity) with a difference of significant value in favor of MRU (p <0.001).

CONCLUSIONS

In patients with renal impairment due to ureteral obstruction NCCT has superior diagnostic accuracy for detecting calculous causes of obstruction but MRU is superior for identifying noncalculous lesions.

Distinguishing stent from stone: use of bone windows

OBJECTIVES

To present a simple method to assist in distinguishing stents or nephrostomy tubes from urinary tract stones. Non-contrast computed tomography (CT) is now routinely used for the diagnosis and follow-up of urinary tract stones. When stents or nephrostomy tubes are in place, it may be difficult to differentiate the stent from the stone.

METHODS

Three representative patients with ureteral stents or nephrostomy drainage catheters (stents/tubes) who were suspected of having residual urinary tract stones were studied by visualizing the suspicious density on CT. Abdominal windows were used for initial viewing, then bone windows were used, and the two techniques were compared. The Hounsfield units (HU) of the various stents/tubes were measured in vitro to establish reference points. The pixel densities of stones have a known range and, in our experience, may be as high as 1600 HU.

RESULTS

Using the abdominal window, no difference was observed in the radiographic appearance of the stents/tubes compared with urinary calculi. However, when viewed in the bone window, the stone appeared less dense than the stent/tube. The in vitro pixel densities of the stents/tubes measured 1600 to 2600 HU compared with the calculi, which do not exceed 1600 HU.

CONCLUSIONS

Using the abdominal window, stents and stones may have the same CT appearance. However, the bone window allows a visual distinction between a stent/tube and a stone. This distinction is accounted for by differences in pixel density. This observation allows one to distinguish a stent/tube from a stone on CT in patients in whom a nephrostomy tube or ureteral stent is present.

Advanced imaging in stone management

PURPOSE OF REVIEW

Stone disease continues to plague humankind. Recent innovations in minimally invasive surgery, however, have decreased morbidity for the treatment of lithiasis, once only amenable to open surgical techniques. These advances in stone management have also been paralleled in the radiographic armamentarium. Herein, we describe the evolution of initial radiographic workup for urolithiasis, from abdominal radiograph to three-dimensional computed tomography and some of the novel applications thereof.

RECENT FINDINGS

Previously, abdominal radiography was the only modality available for the visualization of calculi. Subsequently, the development of intravenous contrast aided in evaluating renal function, detecting the presence and location of obstruction, and in identifying filling defects. Most recently, prospective randomized trials have demonstrated improved sensitivity and specificity using noncontrast helical computed tomography rather than intravenous pyelogram with regard to the initial evaluation of acute flank pain. Further attempts to lower the overall radiation dose without compromising efficacy have also been introduced. Currently, the volume of calculus disease can be better quantified and somewhat qualified from three-dimensional computer software, thereby optimizing stone management.

SUMMARY

Considerable progress has been made using minimally invasive techniques in the treatment of nephrolithiasis. Furthermore, advances in radiographic computer hard- and software applications allow for a rapid acquisition time and improved image quality without sacrificing diagnostic accuracy. In time, it is likely that the combination of these enhanced imaging modalities will lead to an improvement in stone localization, fragmentation and stone-free rates.

Impact of multislice CT on imaging of acute abdominal disease

The increased speed, greater coverage, and thinner slices of MSCT are exciting developments in radiology, and these feature should only improve with newer generation multislice scanners. The impact of this technology on abdominal imaging has just begun.

Acute Ureterolithiasis: Incidence of Secondary Signs on Unenhanced Helical CT and Influence on Patient Management

AIM

The purpose of this study was to determine the incidence of secondary signs associated with ureteral stones on unenhanced helical computed tomography (CT) of patients with acute renal colic, and to correlate these with patient management and outcome.

MATERIALS AND METHODS

One hundred and ten patients with ureterolithiasis were evaluated prospectively for the secondary signs of obstruction on unenhanced helical CT. Our attention was focused primarily on the presence or absence of seven secondary signs on unenhanced helical CT, including hydronephrosis, unilateral renal enlargement, perinephric oedema, unilateral absence of the white pyramid, hydroureter, periureteral oedema and lateroconal fascial thickening.

RESULTS

Of the 110 patients, 91 (82.7%) had hydroureter, 88 (80%) had hydronephrosis, 65 (59%) had periureteric oedema and 63 (57.2%) had unilateral renal enlargement. Ninety stones passed spontaneously and 21 required intervention.

CONCLUSION

Secondary signs of urinary tract obstruction are useful and supportive findings in interpretation of the CT examination. In our experience, the most reliable signs indicating ureteral obstruction are hydroureter, hydronephrosis, periureteral oedema and unilateral renal enlargement, respectively. In addition, stones larger than 6 mm, located within the proximal two thirds of the ureter, and seen associated with five or more the secondary signs of obstruction, are more likely to require endoscopic removal and/or lithotripsy.

Impact of date of onset on the absence of hematuria in patients with acute renal colic

PURPOSE

Hematuria is absent in a significant proportion of patients with acute ureterolithiasis. We determined whether time from pain onset has any impact on the sensitivity of hematuria tests in the diagnosis of ureterolithiasis.

MATERIALS AND METHODS

We retrospectively reviewed the records of 537 patients with suspected acute unilateral renal colic during a 29-month period with regard to the interval between pain onset and urinalysis, including the dipstick test and microscopic red blood cell count as well as other clinical findings. Although ureterolithiasis was determined by plain x-ray and ultrasonography primarily, stone absence was diagnosed by computerized tomography.

RESULTS

Ureterolithiasis was diagnosed in 452 patients (84.2%). The dipstick test had higher sensitivity (0.780 vs 0.718) but it was equivalent on ROC analysis compared with microscopic examination (area under the curve 0.696 vs 0.694, p = 0.92). Hematuria test sensitivity was 0.95, 0.83, 0.65, 0.68, 0.77, 0.86 and 0.68 on days 0, 1, 2, 3, 4, 5 to 7 and 8 or more from pain onset, respectively (ANOVA p = 0.004). On logistic regression analysis including hydronephrosis grade, and stone size and location the interval between onset and urinalysis was the only independent factor affecting the incidence of negative hematuria in patients with ureterolithiasis (p = 0.03, 95% CI 0.89 to 0.99).

CONCLUSIONS

The interval between pain onset and urine collection has a significant impact on the diagnostic performance of hematuria tests. The incidence of negative hematuria is highest on the days 3 and 4.

Unenhanced helical computed tomography vs intravenous urography in patients with acute flank pain: accuracy and economic impact in a randomized prospective trial

Unenhanced helical computed tomography (UHCT) has evolved into a well-accepted alternative to intravenous urography (IVU) in patients with acute flank pain and suspected ureterolithiasis. The purpose of our randomized prospective study was to analyse the diagnostic accuracy of UHCT vs IVU in the normal clinical setting with special interest on economic impact, applied radiation dose and time savings in patient management. A total of 122 consecutive patients with acute flank pain suggestive of urolithiasis were randomized for UHCT ( n=59) or IVU ( n=63). Patient management (time, contrast media), costs and radiation dose were analysed. The films were independently interpreted by four radiologists, unaware of previous findings, clinical history and clinical outcome. Alternative diagnoses if present were assessed. Direct costs of UHCT and IVU are nearly identical (310/309 Euro). Indirect costs are much lower for UHCT because it saves examination time and when performed immediately initial abdominal plain film (KUB) and sonography are not necessary. Time delay between access to the emergency room and start of the imaging procedure was 32 h 7 min for UHCT and 36 h 55 min for IVU. The UHCT took an average in-room time of 23 min vs 1 h 21 min for IVU. Mild to moderate adverse reactions for contrast material were seen in 3 (5%) patients. The UHCT was safe, as no contrast material was needed. The mean applied radiation dose was 3.3 mSv for IVU and 6.5 mSv for UHCT. Alternative diagnoses were identified in 4 (7%) UHCT patients and 3 (5%) IVU patients. Sensitivity and specificity of UHCT and IVU was 94.1 and 94.2%, and 85.2 and 90.4%, respectively. In patients with suspected renal colic KUB and US may be the least expensive and most easily accessable modalities; however, if needed and available, UHCT can be considered a better alternative than IVU because it has a higher diagnostic accuracy and a better economic impact since it is more effective, faster, less expensive and less risky than IVU. In addition, it also has the capability of detecting various additional renal and extrarenal pathologies.

CT evaluation of urinary lithiasis

Unenhanced CT has been demonstrated to be the most accurate and efficient diagnostic imaging means to evaluate urinary lithiasis, with capability of directing management, and has become well accepted by radiologists, urologists, and emergency department physicians such that it is now the standard of practice. It is the duty of the radiologist to be aware of proper technique and the details of interpretation. The radiologist also has a duty to be aware of the limitations of unenhanced CT for detection and evaluation of various nonstone disorders, particularly with poor patient selection, and to extend the examination if appropriate. Controversies and future developments include cost containment with care for the selection of patients. Further attempts to reduce radiation exposure should be made. Optimal CT technique is not needed in general merely to detect urinary lithiasis. A consensus should be developed regarding use of CT in pregnant patients. Further improvements in the digital scout view would be useful for following patients.

Clinical characteristics of ureteral calculi detected by nonenhanced computerized tomography after unclear results of plain radiography and ultrasonography

PURPOSE

Prospective non-enhanced computerized tomography (CT) was performed for patients presenting with renal colic and showing negative or equivocal results on plain x-ray of the kidneys, ureters and bladder (KUB) as well as ultrasonography (US) to evaluate the usefulness of plain CT. We also evaluated the clinical characteristics of urinary calculi detected under such conditions.

MATERIALS AND METHODS

Between January 2000 and June 2002, 560 patients presented with acute unilateral renal colic. Of these patients 238 negative or equivocal for ureteral calculus on KUB and US underwent non-enhanced CT. The diagnostic value of plain CT in patients with negative or equivocal KUB and US was determined, and results and other clinical findings were compared. Clinical characteristics of ureteral stones detected by plain CT were compared with those of stones diagnosed by KUB and US.

RESULTS

By plain CT 143 (60.1%) and 6 (2.5%) cases of pain were determined to have been caused by ureteral stones and other pathogeneses, respectively. No definitive diagnosis was obtained in 89 (37.4%). Stone size detected by plain CT was significantly smaller than controls (3.77 vs 6.37 mm, p <0.0001) and tended to be located in the middle or lower ureter (76.2% or 109 of 143 vs 52.2% or 168 of 322, p <0.0001). Symptoms spontaneously improved in 137 (95.8%) after conservative therapy while 6 underwent intervention, a rate significantly lower (p <0.0001) than controls (32.9% or 106 of 322).

CONCLUSIONS

Non-enhanced CT is a useful modality for diagnosis of patients presenting with acute renal colic but whose results are negative or equivocal on KUB and US. Excretory urography is rarely needed because stones undetected on KUB and US tend to be small and in the middle or lower ureter, and spontaneous passage is expected.

Unenhanced helical computed tomography in the evaluation of acute flank pain

OBJECTIVES

The purpose of this study was to determine the value of unenhanced helical computed tomography (UHCT) in the diagnosis of acute flank pain at our institution.

METHODS

Two hundred and thirty-three consecutive UHCT examinations, performed for suspected renal/ureteral colic between July 2000 and August 2001 were reviewed, along with pertinent medical records.

RESULTS

Ureteral calculi were identified in 148 (64%) examinations, evidence of recent passage of calculi was found in 10 (4%) and no calculi were found in 75 (32%). Thirty-two of the conservatively managed patients were excluded for inadequate follow-up. In the remaining 201 patients, sensitivity of UHCT in diagnosing calculi was 99% and specificity was 98%, while the positive predictive value was 99% and negative positive predictive value was 98%. Overall, an alternative or additional diagnosis was established in 28 (12%) patients. Upon diagnosis of ureterolithiasis on UHCT, none of the patients required additional imaging studies for confirmation.

CONCLUSION

UHCT is a highly sensitive imaging modality for the detection of urinary tract calculi and obstruction.

Incidental diagnosis of diseases on un-enhanced helical computed tomography performed for ureteric colic

BACKGROUND

Patients presenting in the emergency room with flank pain suggestive of acute ureteric colic may have alternative underlying conditions mimicking ureteric stones. An early diagnosis and appropriate treatment for other causes of flank pain is important. The majority of centers around the world are increasingly using un-enhanced helical CT (UHCT) for evaluation of ureteric colic. This study was conducted to determine the incidence and spectrum of significant incidental diagnoses established or suggested on UHCT performed for suspected renal/ureteric colic.

METHODS

Urologist and radiologist reviewed 233 consecutive UHCT, performed for suspected renal/ureteral colic along with assessment of the medical records. Radiological diagnoses of clinical entities not suspected otherwise were analyzed. All other relevant radiological, biochemical and serological investigations and per-operative findings were also noted.

RESULTS

Ureteral calculi were identified in 148 examinations (64%), findings of recent passage of calculi in 10 (4%) and no calculus in 75 examinations (32%). Overall the incidental findings (additional or alternative diagnosis) were found in 28 (12%) CT scans. Twenty (71%) of these diagnoses were confirmed by per-operative findings, biopsy, and other radiological and biochemical investigations or on clinical follow up.

CONCLUSION

A wide spectrum of significant incidental diagnoses can be identified on UHCT performed for suspected renal/ureteral colic. In the present series of 233 consecutive CT examinations, the incidence of incidental diagnosis was 12%.

Renal colic: a prospective evaluation of non-enhanced spiral CT versus intravenous pyelography

The aim of this study was to compare non-enhanced spiral CT (NECT) and intravenous pyelography (IVP) in patients with suspected acute renal colic. Two-hundred patients presenting to the Emergency Department with suspected acute renal colic were randomized into groups undergoing NECT or IVP. The main outcome measures were diagnostic utility, incidence of alternative diagnoses, requirement for further imaging, length of hospital stay, urological intervention rates, radiation dosage and costs. Non-enhanced spiral CT was better than IVP in making a definitive diagnosis of ureteric calculus or of recent calculus passage (65/102 or 66% vs 42/98 or 41%; P = 0.003). Calculi were missed in two patients in the IVP group. Two patients in each group had alternative diagnoses by initial imaging. There was no difference in the length of hospital stay or intervention rate. More plain X-rays during admission and more IVPs during follow up were performed in the NECT group. Effective radiation dosages were 2.97 mSv (IVP) and up to 5 mSv (NECT). Non-enhanced spiral CT provided greater diagnostic utility in this randomized comparison but no difference in measured outcomes. The incidence of alternative diagnoses was low, probably due to patient selection. Financial costs for each modality are comparable in a public tertiary hospital. Radiation dosages are higher for NECT and, for this reason, it might be appropriate to consider limiting NECT use to patients who have do not have classical symptoms of renal colic, to older patients and those with a contraindication to the administration of intravenous contrast media.

The efficacy of non-contrast helical computed tomography in the prediction of urinary stone composition in vivo

The composition of urinary stones was predicted on the basis of the differences in their Hounsfield unit (HU) densities as detected by in vivo non-contrast helical computed tomography (NCHCT). A total of 87 stones, which had been obtained from patients admitted to the emergency department with acute flank pain, were analysed biochemically. These stones had been visualized by NCHCT before spontaneous passage, ureteroscopic extraction or surgical removal, and their HU densities had been recorded. The HU densities of the stones were compared with the results of biochemical analysis. The mean HU densities of the stones composed of calcium oxalate (n = 54), struvite (n = 19) and uric acid (n = 14) were 812 +/- 135, 614 +/- 121 and 413 +/- 143, respectively. The differences between the mean HU densities of these three stone types were statistically significant. This initial clinical study demonstrated that in vivo NCHCT analysis may be used to predict the composition of urinary stones.

The accuracy of noncontrast helical computed tomography versus intravenous pyelography in the diagnosis of suspected acute urolithiasis: a meta-analysis

STUDY OBJECTIVES

We determine the accuracy of noncontrast helical computed tomography (NHCT) compared with that of intravenous pyelography (IVP) in diagnosing acute urolithiasis.

METHODS

Computerized searches of MEDLINE and EMBASE were combined with hand reviews of major journals and of articles from reference lists. Articles were assessed according to a priori criteria for inclusion. Study eligibility was independently assessed by 2 reviewers in a blinded fashion. Test results were combined and analysis of log-transformed data was conducted by using general linear models.

RESULTS

No disagreement was found between the 2 investigators in terms of articles that met the inclusion criteria or between the results of the studies. Four studies involving a total of 296 patients met all of the a priori criteria. The pooled positive likelihood ratios (LR+) for NHCT and IVP are 23.15 (95% confidence interval [CI] 11.53 to 47.23) and 9.32 (95% CI 5.23 to 16.61), respectively. The pooled negative likelihood ratios (LR-) for NHCT and IVP are 0.05 (95% CI 0.02 to 0.15) and 0.33 (95% CI 0.23 to 0.48), respectively. The differences between NHCT and IVP were statistically significant for both LR+ (P =.046) and LR- (P =.013). Differences among trials were not statistically significant in either analysis (P =.125 for LR+; P =.114 for LR-).

CONCLUSION

The studies analyzed consistently demonstrated NHCT to be superior to IVP in accurately diagnosing acute urolithiasis, and differences between the 2 tests for both LR+ and LR- were statistically significant.

Non contrast computerized tomography and dynamic renal scintigraphy in the evaluation of patients with renal colic: are both necessary?

OBJECTIVES

To determine the value of the combined use of non contrast computerized tomography (NCCT) and dynamic renal scintigraphy (DRS) in the evaluation of patients with renal colic.

METHODS

Forty-nine consecutive patients with renal colic were evaluated with abdominal plain films (KUB), NCCT and DRS with Tc-99m DTPA or MAG-3. NCCT results showed size and location of the urolithiasis, as well as secondary signs of obstruction. DRS was used to determine the degree of obstruction in the affected renal unit. Patients were submitted to urologic intervention or followed, decision made on the basis of clinical symptoms, degree of obstruction, size, and location of the stone.

RESULTS

Three patients had other etiologies than stone for their symptoms and were excluded from the study. Of the remaining 46 patients, KUB detected stones in 24 (52.2%), while NCCT in all. NCCT showed secondary signs of obstruction in 35 patients (76%). Seven patients in this group (15%) had severe hydronephrosis on NCCT and complete obstruction on DRS. Twenty-eight patients (61%) showed moderate hydronephrosis and/or peri-renal and peri-ureteral stranding on the NCCT. In this latter group, DRS diagnosed complete obstruction in 5 (18%) patients, partial obstruction in 16 (57%) and no signs of obstruction in 7 (25%) patients. Overall 34% (12/35) of the patients with secondary signs of obstruction on NCCT had complete obstruction on DRS. NCCT revealed no secondary signs of obstruction in 11 patients (24%) with partial obstruction diagnosed by DRS in one of them (9%). All 12 patients with complete obstruction on the DRS underwent early intervention. Of the 16 patients with partial obstruction of the DRS, two patients (12.5%) necessitated ureteric stent insertion. Three patients with no obstruction on the RNS underwent elective extracorporal shock wave lithotripsy (ESWL) while the rest of the patients were followed and passed their stones spontaneously.

CONCLUSIONS

The combination of non-enhanced helical CT and DRS assesses both anatomy and function. When NCCT shows no secondary signs of obstruction, NCCT as the sole imaging study performed may be adequate. If there are secondary signs of obstruction on NCCT, DRS can distinguish patients with different degrees of obstruction and together with the clinical course, size, and location of the lithiasis may help in selecting patients who need earlier intervention from those who may be safely observed.

Noncontrast computed tomography in obstructive anuria: a prospective study

OBJECTIVES

To evaluate the role of noncontrast computed tomography (NCCT) in the determination of the cause of obstructive anuria and to compare its accuracy with that of the traditional methods of combined plain abdominal x-ray (KUB) and gray-scale abdominal ultrasonography (US).

METHODS

The study included 40 consecutive patients with obstructive anuria. In addition to the routine evaluation, which included history, clinical examination, biochemical profile, KUB, and US, all patients underwent NCCT. The study patients were tested against an age and sex-matched control group that included the normal contralateral kidneys of 57 consecutive patients who underwent KUB, US, and NCCT for acute flank pain during the same study period. The reference standard for the determination of the cause of obstruction was retrograde or antegrade ureterography with or without ureteroscopy or open surgery. The absence of obstruction in the control group was confirmed by nonequivocal normal intravenous urography of the side free of flank pain. Both NCCT and combined KUB and US were compared regarding the sensitivity, specificity, and overall accuracy.

RESULTS

The study group had 48 renal units, because obstruction was bilateral in 8 patients and of a solitary kidney in 32. Of the 42 renal units with calculus obstruction, the site of stone impaction was identified in all renal units by NCCT (sensitivity 100%) and in only 25 by combined KUB and US (sensitivity 59.5%)-a significant difference (P = 0.0001). Of the 6 renal units with noncalcular obstruction, both NCCT and US diagnosed the cause of obstruction in 3. The overall sensitivity of NCCT in the determination of the cause of obstructive anuria was 94% and that of combined KUB and US was 58%-a significant difference (P = 0.0001). The specificity of NCCT was not significantly different from that of combined KUB and US (96.5% versus 93%, respectively). The overall accuracy of NCCT was 95% and that of combined KUB and US was 77%-a significant difference (P = 0.0003).

CONCLUSIONS

In patients with obstructive anuria, conventional KUB and US could not identify the cause of ureteral obstruction in about 40% of the patients. Under such conditions, NCCT can accurately provide the diagnosis, obviating the need of invasive and expensive diagnostic procedures.

Unenhanced helical CT in the investigation of acute flank pain

Unenhanced helical CT has emerged as the imaging technique of choice for the investigation of patients presenting with acute flank pain and suspected nephroureteric stone disease. There are several signs identifiable on unenhanced CT that support a diagnosis of stone disease. However, there are many pitfalls, that may confound a correct diagnosis. Some of the common pitfalls, together with methods to avoid such occurrences, will be discussed. A review of some of the common alternative diagnoses that may mimic the symptoms of nephroureteric stone disease is illustrated.

Low dose unenhanced helical computerized tomography for the evaluation of acute flank pain

PURPOSE

Unenhanced helical computerized tomography (CT) has proved to be an excellent diagnostic tool for evaluating acute flank pain with reported 95% to 100% sensitivity, 92% to 100% specificity, 96% to 100% positive and 91% to 100% negative predictive values. The diagnostic value of a new low dose protocol was prospectively studied and compared with the results of conventional unenhanced helical CT in a previous series with an effective dose equivalent (HE) of 3.1 to 4.3 mSv. and in current literature with an estimated HE of 4.3 to 4.7 mSv.

MATERIALS AND METHODS

In 109 patients 18 to 86 years old with acute flank pain we performed low dose unenhanced helical CT in addition to abdominal ultrasound and urinalysis with new CT parameters (120 kV. 70 mA., 5 mm. collimation, pitch 2 and incremental reconstruction each 5 mm.) that led to a more than 50% decrease in radiation exposure to 1.50 mSv. in females and 0.98 mSv. in males. Ureteral calculi were confirmed or excluded by retrograde ureteropyelography in 51 cases. In the other cases the diagnosis was verified by the clinical and ultrasound course, and/or stone asservation.

RESULTS

In 80 of the 109 patients the flank pain was caused by a ureteral calculus. Low dose unenhanced helical CT precisely identified 77 ureteral calculi with 1 false-positive finding. Thus, the sensitivity and specificity of low dose unenhanced helical CT were 96% and 97% with a 99% positive and 90% negative predictive value. In 15 of 29 patients with CT findings negative for stone disease different causes of pain were established by low dose unenhanced helical CT.

CONCLUSIONS

Even with the significantly decreased radiation exposure of the low dose protocol unenhanced helical CT is still an excellent and rapid diagnostic tool for evaluating acute flank pain with lower radiation exposure than excretory urography (HE 1.3 to 2.3 mSv.) at our departments. Only in obese patients with a body mass index of greater than 31 kg./m.2 is conventional unenhanced helical CT with higher radiation exposure recommended to achieve adequate image quality.

Urinary tract abnormalities: initial experience with multi-detector row CT urography

PURPOSE

To evaluate multi-detector row computed tomographic (CT) urography for detection of urinary tract abnormalities.

MATERIALS AND METHODS

Sixty-five patients referred from the urology service, in whom urinary tract abnormalities were strongly suspected, underwent multi-detector row CT urography. The technique included unenhanced, nephrographic, compression, and excretory-phase images through the abdomen and pelvis. Transverse images and three-dimensional reformations were reviewed by one of two radiologists. Findings were retrospectively compared with results of urinalysis, cystoscopy and/or ureteroscopy, and/or surgery.

RESULTS

Multi-detector row CT urography depicted many clinically diagnosed urinary tract abnormalities, including 15 of 16 uroepithelial malignancies, five congenital anomalies, five urinary tract calculi, and 18 calyceal and/or papillary, 30 renal pelvic and/or ureteral, and 25 bladder abnormalities. All abnormalities were detected on transverse images. These abnormalities included diffuse urothelial wall thickening in four patients (three of whom had transitional cell carcinoma), a renal abscess, a colovesical fistula, and incidentally detected extrarenal disease (a liver mass, hepatic metastases, lymph node metastases, an aortic dissection, and a pheochromocytoma; each of these findings was seen in one patient).

CONCLUSION

Multi-detector row CT urography is a useful method for detecting urinary tract abnormalities.

Unenhanced spiral CT for the assessment of renal colic. How does limiting the referral base affect the discovery of additional findings not related to urinary tract calculi?

The value of unenhanced spiral CT (UESCT) for investigating acute flank pain suggestive of urinary tract calculi is increasingly appreciated in the last few years. Recent studies have identified the advantages of UESCT in recognizing alternative findings within or outside the urinary tract. We sought to determine how narrowing the referral base for the UESCT would affect the discovery of potentially significant alternative findings in patients with acute flank pain suggestive of renal colic. Between January 1999 and December 1999, 425 patients, 271 (63.8%) men and 154 (36.2%) women who were 1-90 years old (mean 45.7 years old) with acute flank pain were studied with UESCT. CT studies were solely ordered by urologists, and only patients with intractable renal colic or patients that returned more than once to the emergency room with the complaint of acute flank pain were studied. A calculus within the ureter was diagnostic of an obstructive stone. Any other abnormality within the abdomen and pelvis was reported. A ureteral calculus was detected on 251 (59%) CT scans. Nineteen (4.5%) CT scans were consistent with recent excretion of a stone. In 112 (26.3%) CT scans, the cause for the patient's acute flank pain could not be explained. Forty-three (10.1%) alternative significant diagnoses that explain the patient's complaints were found. Nineteen (44%) were findings related to the urinary tract, and 24 (56%) were not related to the urinary tract. Ninety-seven (22.3%) additional findings not significant to the patient's current complaint were also reported. Even when narrowing the indications for the UESCT, about 10% of significant alternative findings to urinary stones were encountered. The variety of diagnoses found unexpectedly on the UESCT that alter a patient's management demonstrates the pivotal role of UESCT in triaging these patients rapidly towards optimal therapy. The UESCT can be used as a useful screening tool, sometimes revealing the exact pathology and sometimes directing the radiologist to the modality by which to continue.

Assessment of the clinical utility of the rim and comet-tail signs in differentiating ureteral stones from phleboliths

OBJECTIVE

This study was designed to assess interobserver variability in identifying the rim and comet-tail signs and to determine the clinical utility of these signs in determining whether or not the calcifications with which they are associated represent ureteral calculi.

MATERIALS AND METHODS

Two radiologists and a radiology resident, unaware of the final diagnosis, reviewed preselected helical CT images from renal stone examinations in patients with 65 indeterminate pelvic calcifications. Assessment of calcifications for rim or comet-tail signs was performed independently of an assessment for the following five secondary signs of urinary tract obstruction: caliectasis, pelviectasis, ureterectasis, perinephric stranding, and renal enlargement. Agreement in identifying rim and comet-tail signs was assessed by obtaining kappa statistics. The utility the of rim or comet-tail signs in determining whether ureterolithiasis was present in patients in whom perinephric stranding and ureterectasis were present or absent was determined. The frequency with which one or more of each of the five assessed secondary signs was identified ipsilateral to a calcification having rim or comet-tail signs was also tabulated.

RESULTS

Kappa values for interobserver agreement ranged from 0.49 to 0.73. In only one patient was a rim sign detected in the absence of ureterectasis and perinephric stranding. Reviewers identified at least three of the five assessed secondary signs ipsilateral to calcifications showing a rim sign in all but one patient (by each radiologist) and four patients (by the resident). When three or more secondary signs of obstruction were seen ipsilateral to a calcification having a comet-tail sign, in all but one instance, this was because the calcification was a ureteral calculus or because there was a separate ipsilateral ureteral calculus.

CONCLUSION

In many instances, observers did not agree about whether the rim and comet-tail signs were present. The rim sign was observed in the absence of any secondary signs of urinary tract obstruction in only one (1.5%) of the 65 patients in our series (95% confidence interval, 0-5.3%). The comet-tail sign, when accompanied by secondary signs of obstruction, should indicate that an ipsilateral ureteral stone is present and not the reverse.

Low dose computed tomography in suspected acute renal colic

AIM

To evaluate whether computed tomography (CT) of the renal tract in suspected renal colic using reduced exposure factors maintains diagnostic accuracy.

METHODS

Prospective multi-centre cohort study. Patients with suspected renal colic were examined using computed tomography (CT) of the renal tract followed by intravenous urography (IVU) in four different centres with five different CT systems.

RESULTS

Sixty-nine patients with suspected renal colic had CT of the renal tract followed by IVU. CT was performed with reduced exposure factors, giving a mean CT effective dose of 3.5 (range 2.8-4.5) mSv compared with 1.5 mSv for IVU. Ureteric calculi were detected in 43 patients: CT and IVU detected 40 (93%) ureteric calculi. CT identified other lesions causing symptoms in five patients and identified renal calculi in 24 patients. IVU identified renal calculi in six patients and made false positive diagnosis of renal calculi in seven patients. Mean examination time for CT was 5 minutes and for IVU was 80 minutes.

CONCLUSION

CT examination at reduced exposure factors maintains the diagnostic accuracy recorded in other series.

Image quality and dose comparison among screen-film, computed, and CT scanned projection radiography: applications to CT urography

PURPOSE

To evaluate image quality and dose for abdominal imaging techniques that could be used as part of a computed tomographic (CT) urographic examination: screen-film (S-F) radiography or computed radiography (CR), performed with moving and stationary grids, and CT scanned projection radiography (CT SPR).

MATERIALS AND METHODS

An image quality phantom underwent imaging with moving and stationary grids with both a clinical S-F combination and CR plate. CT SPR was performed with six CT scanners at various milliampere second and kilovolt peak settings. Entrance skin exposure (ESE); spatial, contrast, and temporal resolutions; geometric accuracy; and artifacts were assessed.

RESULTS

S-F or CR images, with either grid, provided image quality equivalent to that with the clinical standard, S-F with a moving grid. ESE values for both S-F and CR were 435 mR (112.2 microC/kg [1 mR = 0.258 microC/kg]) with a moving grid and 226 mR (58.3 microC/kg) with a stationary grid. All CT SPR images provided inferior spatial resolution compared with S-F or CR images. High-contrast objects generated substantial artifacts on CT SPR images. Compared with S-F, CR and CT SPR provided improved resolution of small low-contrast objects. The contrast between iodine and soft-tissue-mimicking structures on CT SPR images acquired at 80 kVp was twice that at 120 kVp. CT SPR images with acceptable noise levels required a midline ESE value of approximately 300 mR (77.4 microC/kg) at 80 kVp.

CONCLUSION

S-F and CR provided better spatial resolution than did CT SPR. However, CT SPR provided improved low-contrast resolution compared with S-F, at exposures comparable to those used for S-F or CR.

Emergency department time for evaluation of patients discharged with a diagnosis of renal colic: unenhanced helical computed tomography versus intravenous urography

The objective of this study was to determine whether patients discharged from the Emergency Department (ED) with a proven diagnosis of renal colic require less total evaluation and treatment time if unenhanced helical computed tomography (CT) rather than intravenous urography (IVU) was the diagnostic imaging study used. A retrospective review was undertaken of the medical records of 98 consecutive patients with a final diagnosis of urolithiasis or renal colic evaluated with an unenhanced helical CT scan or an IVU between January 1, 1999, and December 31, 1999. All patients were managed by Emergency Physicians and discharged from the ED. The time the patient was brought to the treatment area, the time the imaging study was ordered, and the time the patient was discharged were recorded. There were 75 patients evaluated with CT scan and 23 patients with an IVU. Patients who underwent unenhanced helical CT scan were in the ED for a mean time of 291 min [95% confidence interval (CI) 266-316] and those who had an IVU were in the ED for an average of 410 min (95% CI 340-481). Use of unenhanced helical CT scan was associated with less total time in the ED compared to IVU for patients with renal colic by a significant mean of 119 min. It is concluded that ED evaluation and treatment time of patients ultimately discharged with a proven diagnosis of renal colic is significantly less when evaluated with unenhanced helical CT scan compared to IVU.

Effect of radiographic contrast material exposure on spiral CT attenuation of renal calculi

RATIONALE AND OBJECTIVES

The authors performed this study to determine whether exposure of renal calculi to radiographic contrast material has an effect on the attenuation values at computed tomography (CT) performed with varying collimation widths.

MATERIALS AND METHODS

Renal calculi (23 stones of various composition) were scanned with 1-, 3-, and 10-mm collimation. Stones were then exposed to a solution of radiographic contrast material for 5 minutes, washed with water, and rescanned 36 hours later. The reproducibility of the CT attenuation measurements on different days was evaluated by obtaining measurements in a subset of 16 renal stones on 4 different days.

RESULTS

There was no statistically significant change in attenuation after contrast material exposure at narrow collimation. At wider collimation, statistically significant increases were noted in both attenuation and standard deviation. A small amount of variability between readings was noted on different days, with a minimal increase in attenuation each day. Correlation between readings remained very high.

CONCLUSION

Exposure of stones to a radiographic contrast material had a statistically significant effect on CT attenuation values only at wide collimation. This may be related to technical factors including volume averaging. Absence of an effect at narrow collimation suggests that the attenuation values of renal stones do not significantly change after exposure to contrast material.

[Contrast-free helical computerized tomography compared with ultrasonography and simple abdominal radiography in the study of patients with acute lumbar pain]

OBJECTIVE

Evaluation the diagnostic ability of unenhanced helical computed tomography in the evaluation of patients with acute flank pain.

PATIENTS AND METHODS

Prospectively evaluation of 82 patients referred for acute flank pain between january 1999 and june 2000. 78 patients were imaged with, 73 abdominal ultrasound and 46 with TCHNC.

RESULTS

Plain radiography shows 49.1% of diagnosed lithiasis. Ultrasound was 48% sensitive and 96% specific. TCHNC was 100% sensitive and 84% specific in the diagnosis of lithiasis, allowing in 11 patients a diagnosis unrelated to stone disease.

CONCLUSIONS

TCHNC is a valuable radiologic technique for patients presenting with acute flank pain and consider the TCHNC as initial evaluation technique in patients with acute flank pain, allowing not only the localization of the stone as well as the diagnosis of extraurinary pathologies.

Nephrolithiasis

This article covers the diagnosis and management of renal colic. New imaging modalities will be reviewed using evidence-based medicine. The disposition of the patient with renal colic will be addressed. Additionally, special groups with nephrolithiasis will be discussed.