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What is the best test to diagnose urinary tract stones?
Over the past 3 years, helical (or spiral) computerized tomography (CT) has proved the best method of testing for urinary tract stones. All reviewed studies published since mid-1998 found helical CT scan to be the safest and most accurate test. (Grade of recommendation: A, based on independent blind comparison of an appropriate spectrum of patients.)
Evidence summary
Several studies demonstrating the accuracy of helical CT have been published recently.1-3 The most convincing are 2 prospective studies done in emergency departments in Belgium and Australia.1,2 Both compared helical CT with intravenous pyelography (IVP) and used the gold standard of recovery and direct visualization of a stone. The Australian study enrolled 40 consecutive patients; the Belgian study enrolled 53 of 70 consecutive patients. In these 2 studies, helical CT correctly identified every instance of urinary tract stones. In contrast, IVP failed to detect stones in a third of the patients with stones, and 44% of the negative readings were false-negatives. Both tests did well in reporting negative results for those patients without stones (specificity = 97% for both tests). In terms of likelihood ratios, helical CT and IVP had positive likelihood ratios of 29 and 19, respectively, and negative likelihood ratios of 0 and 0.36 (a lower negative likelihood ratio is better). In other words, helical CT appears to be far superior to IVP in ruling out the presence of urinary tract stones. As an additional comparison, another study found that urine dipstick testing for hematuria yielded positive likelihood ratios of 1.25 and a negative likelihood ratio of 0.55.4 The accuracy of ultrasonography appears to fall somewhere in between hematuria testing and IVP.5 The Table shows an overall comparison of these diagnostic tests.
In addition to its better accuracy, several studies discuss the better safety profile and decreased diagnostic time of helical CT than IVP.6-8 The risk of contrast reaction during IVP is between 5% and 10%, with a mortality of approximately 1 in 40,000. Helical CT (when evaluating for stones) does not use contrast, although the radiation exposure is approximately twice that of IVP.6 The costs of helical CT and IVP are comparable, and helical CT becomes more cost effective when the shorter time to discharge with a definitive diagnosis is considered.7,8 Several authors also cite instances when helical CT uncovered a nonurinary cause for patients’ symptoms that IVP would have missed.8,9
Access to helical CT is improving throughout the United States, and individual radiologists can become quickly skilled at helical CT interpretation.10 Physicians should confirm that their local radiologists are comfortable with helical CT readings before incorporating this into their diagnostic routines.
Recommendations from others
Several urology and radiology departments have published reviews lately supporting the use of helical CT over other diagnostic testing for urinary tract stones.9,11 No official recommendations from professional organizations were found.
Sang-Ick Chang, MD
University of California, San Francisco
From a practical point of view, spiral CT has been a far superior modality for diagnosis of urinary tract stones. It is much faster, avoids contrast, renal function is not an issue, and previous bowel preparation is not needed. Given the relatively poor performance of the IVP compared with spiral CT, there is no situation I can think of where IVP would be preferred over the spiral CT. The only caveat is that spiral CT is not practical in all practice settings. Still, the 56% negative predictive value for IVP is much lower than we commonly assume and renders the IVP useful mostly for information it can tell us about the size and location of any stone it finds and relatively useless for ruling out stones.
1. Niall O, Russell J, MacGregor R, Duncan H, Mullins J. A comparison of noncontrast computerized tomography with excretory urography in the assessment of acute flank pain. J Urol 1999;161:534-37.
2. Sourtzis S, Thibaeau J, Damry N, Raslan A, Vandendris M, Bellemans M. Radiologic investigation of renal colic: unenhanced CT compared with excretory urography. Am J Roentgenol 1999;172:1491-94.
3. See the JFP Web site, www.jfponline.com, for of other comparison studies.
4. Bove P, Kaplan D, DalrympleN, et al. Reexamining the value of hematuria testing in patients with acute flank pain. J Urol 1999;162:685-87.
5. 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;217:792-97.
6. Liu W, Esler S, Kenny B, Goh R, Rainbow A, Stevenson G. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-54.
7. Patel M, Han S, Vaux K, Saalfeld J, Alexander J. A protocol of early spiral computed tomography for the detection of stones in patients with renal colic has reduced the time to diagnosis and overall management costs. Aus N Z J Surg 2000;70:39-42.
8. Chen M, Zagoria R. Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic? J Emerg Med 1999;17:299-303.
9. Miller O, Kane C. Unenhanced helical computed tomography in the evaluation of acute flank pain. Curr Op Urol 2000;10:123-29.
10. Rosser C, Zagoria R, Dixon R, et al. Is there a learning curve in diagnosing urolithiasis with noncontrast helical computed tomography? Can Assoc Radiol J 2000;51:177-81.
11. See the JFP Web site, www.jfponline.com, for of several review articles.
Over the past 3 years, helical (or spiral) computerized tomography (CT) has proved the best method of testing for urinary tract stones. All reviewed studies published since mid-1998 found helical CT scan to be the safest and most accurate test. (Grade of recommendation: A, based on independent blind comparison of an appropriate spectrum of patients.)
Evidence summary
Several studies demonstrating the accuracy of helical CT have been published recently.1-3 The most convincing are 2 prospective studies done in emergency departments in Belgium and Australia.1,2 Both compared helical CT with intravenous pyelography (IVP) and used the gold standard of recovery and direct visualization of a stone. The Australian study enrolled 40 consecutive patients; the Belgian study enrolled 53 of 70 consecutive patients. In these 2 studies, helical CT correctly identified every instance of urinary tract stones. In contrast, IVP failed to detect stones in a third of the patients with stones, and 44% of the negative readings were false-negatives. Both tests did well in reporting negative results for those patients without stones (specificity = 97% for both tests). In terms of likelihood ratios, helical CT and IVP had positive likelihood ratios of 29 and 19, respectively, and negative likelihood ratios of 0 and 0.36 (a lower negative likelihood ratio is better). In other words, helical CT appears to be far superior to IVP in ruling out the presence of urinary tract stones. As an additional comparison, another study found that urine dipstick testing for hematuria yielded positive likelihood ratios of 1.25 and a negative likelihood ratio of 0.55.4 The accuracy of ultrasonography appears to fall somewhere in between hematuria testing and IVP.5 The Table shows an overall comparison of these diagnostic tests.
In addition to its better accuracy, several studies discuss the better safety profile and decreased diagnostic time of helical CT than IVP.6-8 The risk of contrast reaction during IVP is between 5% and 10%, with a mortality of approximately 1 in 40,000. Helical CT (when evaluating for stones) does not use contrast, although the radiation exposure is approximately twice that of IVP.6 The costs of helical CT and IVP are comparable, and helical CT becomes more cost effective when the shorter time to discharge with a definitive diagnosis is considered.7,8 Several authors also cite instances when helical CT uncovered a nonurinary cause for patients’ symptoms that IVP would have missed.8,9
Access to helical CT is improving throughout the United States, and individual radiologists can become quickly skilled at helical CT interpretation.10 Physicians should confirm that their local radiologists are comfortable with helical CT readings before incorporating this into their diagnostic routines.
Recommendations from others
Several urology and radiology departments have published reviews lately supporting the use of helical CT over other diagnostic testing for urinary tract stones.9,11 No official recommendations from professional organizations were found.
Sang-Ick Chang, MD
University of California, San Francisco
From a practical point of view, spiral CT has been a far superior modality for diagnosis of urinary tract stones. It is much faster, avoids contrast, renal function is not an issue, and previous bowel preparation is not needed. Given the relatively poor performance of the IVP compared with spiral CT, there is no situation I can think of where IVP would be preferred over the spiral CT. The only caveat is that spiral CT is not practical in all practice settings. Still, the 56% negative predictive value for IVP is much lower than we commonly assume and renders the IVP useful mostly for information it can tell us about the size and location of any stone it finds and relatively useless for ruling out stones.
Over the past 3 years, helical (or spiral) computerized tomography (CT) has proved the best method of testing for urinary tract stones. All reviewed studies published since mid-1998 found helical CT scan to be the safest and most accurate test. (Grade of recommendation: A, based on independent blind comparison of an appropriate spectrum of patients.)
Evidence summary
Several studies demonstrating the accuracy of helical CT have been published recently.1-3 The most convincing are 2 prospective studies done in emergency departments in Belgium and Australia.1,2 Both compared helical CT with intravenous pyelography (IVP) and used the gold standard of recovery and direct visualization of a stone. The Australian study enrolled 40 consecutive patients; the Belgian study enrolled 53 of 70 consecutive patients. In these 2 studies, helical CT correctly identified every instance of urinary tract stones. In contrast, IVP failed to detect stones in a third of the patients with stones, and 44% of the negative readings were false-negatives. Both tests did well in reporting negative results for those patients without stones (specificity = 97% for both tests). In terms of likelihood ratios, helical CT and IVP had positive likelihood ratios of 29 and 19, respectively, and negative likelihood ratios of 0 and 0.36 (a lower negative likelihood ratio is better). In other words, helical CT appears to be far superior to IVP in ruling out the presence of urinary tract stones. As an additional comparison, another study found that urine dipstick testing for hematuria yielded positive likelihood ratios of 1.25 and a negative likelihood ratio of 0.55.4 The accuracy of ultrasonography appears to fall somewhere in between hematuria testing and IVP.5 The Table shows an overall comparison of these diagnostic tests.
In addition to its better accuracy, several studies discuss the better safety profile and decreased diagnostic time of helical CT than IVP.6-8 The risk of contrast reaction during IVP is between 5% and 10%, with a mortality of approximately 1 in 40,000. Helical CT (when evaluating for stones) does not use contrast, although the radiation exposure is approximately twice that of IVP.6 The costs of helical CT and IVP are comparable, and helical CT becomes more cost effective when the shorter time to discharge with a definitive diagnosis is considered.7,8 Several authors also cite instances when helical CT uncovered a nonurinary cause for patients’ symptoms that IVP would have missed.8,9
Access to helical CT is improving throughout the United States, and individual radiologists can become quickly skilled at helical CT interpretation.10 Physicians should confirm that their local radiologists are comfortable with helical CT readings before incorporating this into their diagnostic routines.
Recommendations from others
Several urology and radiology departments have published reviews lately supporting the use of helical CT over other diagnostic testing for urinary tract stones.9,11 No official recommendations from professional organizations were found.
Sang-Ick Chang, MD
University of California, San Francisco
From a practical point of view, spiral CT has been a far superior modality for diagnosis of urinary tract stones. It is much faster, avoids contrast, renal function is not an issue, and previous bowel preparation is not needed. Given the relatively poor performance of the IVP compared with spiral CT, there is no situation I can think of where IVP would be preferred over the spiral CT. The only caveat is that spiral CT is not practical in all practice settings. Still, the 56% negative predictive value for IVP is much lower than we commonly assume and renders the IVP useful mostly for information it can tell us about the size and location of any stone it finds and relatively useless for ruling out stones.
1. Niall O, Russell J, MacGregor R, Duncan H, Mullins J. A comparison of noncontrast computerized tomography with excretory urography in the assessment of acute flank pain. J Urol 1999;161:534-37.
2. Sourtzis S, Thibaeau J, Damry N, Raslan A, Vandendris M, Bellemans M. Radiologic investigation of renal colic: unenhanced CT compared with excretory urography. Am J Roentgenol 1999;172:1491-94.
3. See the JFP Web site, www.jfponline.com, for of other comparison studies.
4. Bove P, Kaplan D, DalrympleN, et al. Reexamining the value of hematuria testing in patients with acute flank pain. J Urol 1999;162:685-87.
5. 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;217:792-97.
6. Liu W, Esler S, Kenny B, Goh R, Rainbow A, Stevenson G. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-54.
7. Patel M, Han S, Vaux K, Saalfeld J, Alexander J. A protocol of early spiral computed tomography for the detection of stones in patients with renal colic has reduced the time to diagnosis and overall management costs. Aus N Z J Surg 2000;70:39-42.
8. Chen M, Zagoria R. Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic? J Emerg Med 1999;17:299-303.
9. Miller O, Kane C. Unenhanced helical computed tomography in the evaluation of acute flank pain. Curr Op Urol 2000;10:123-29.
10. Rosser C, Zagoria R, Dixon R, et al. Is there a learning curve in diagnosing urolithiasis with noncontrast helical computed tomography? Can Assoc Radiol J 2000;51:177-81.
11. See the JFP Web site, www.jfponline.com, for of several review articles.
1. Niall O, Russell J, MacGregor R, Duncan H, Mullins J. A comparison of noncontrast computerized tomography with excretory urography in the assessment of acute flank pain. J Urol 1999;161:534-37.
2. Sourtzis S, Thibaeau J, Damry N, Raslan A, Vandendris M, Bellemans M. Radiologic investigation of renal colic: unenhanced CT compared with excretory urography. Am J Roentgenol 1999;172:1491-94.
3. See the JFP Web site, www.jfponline.com, for of other comparison studies.
4. Bove P, Kaplan D, DalrympleN, et al. Reexamining the value of hematuria testing in patients with acute flank pain. J Urol 1999;162:685-87.
5. 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;217:792-97.
6. Liu W, Esler S, Kenny B, Goh R, Rainbow A, Stevenson G. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-54.
7. Patel M, Han S, Vaux K, Saalfeld J, Alexander J. A protocol of early spiral computed tomography for the detection of stones in patients with renal colic has reduced the time to diagnosis and overall management costs. Aus N Z J Surg 2000;70:39-42.
8. Chen M, Zagoria R. Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic? J Emerg Med 1999;17:299-303.
9. Miller O, Kane C. Unenhanced helical computed tomography in the evaluation of acute flank pain. Curr Op Urol 2000;10:123-29.
10. Rosser C, Zagoria R, Dixon R, et al. Is there a learning curve in diagnosing urolithiasis with noncontrast helical computed tomography? Can Assoc Radiol J 2000;51:177-81.
11. See the JFP Web site, www.jfponline.com, for of several review articles.
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Is low-dose dopamine effective in preventing renal dysfunction in patients in the intensive care unit (ICU)?
BACKGROUND: Low-dose dopamine (2 (mg/kg/min) has long been used in the ICU setting in an attempt to preserve renal function in critically ill patients who are at significant risk for renal failure. This practice is based on evidence in healthy patients that low-dose dopamine increases renal blood flow, induces natriuresis and diuresis, and may prevent acute renal failure.
POPULATION STUDIED: A total of 324 patients from 23 ICUs in Australia and New Zealand who had a central venous catheter, had 2 or more changes of the systemic inflammatory syndrome (SIRS), and had at least one marker of early renal dysfunction (decreased urine output, elevated serum creatinine, or rapidly increasing serum creatinine). SIRS is a common response to a variety of severe clinical insults and is a marker of impending sepsis. One operational definition is 2 or more of the following: temperature greater than 38Þ C or less than 36Þ C, heart rate greater than 90, tachypnea (respiratory rate greater than 20), or hyperventilation (partial pressure of carbon dioxide in the arterial blood <32 mm Hg), WBC greater than 12,000 or less than 4,000 or greater than 10% immature neutrophils (bands), where these alterations represent an acute alteration from baseline without other known causes for such abnormalities.
STUDY DESIGN AND VALIDITY: This was a randomized double-blind study comparing the use of low-dose dopamine (n=161) with placebo (n=163) in patients with renal dysfunction. The patients were randomized to receive dopamine or placebo. ICU nurses, staff, and physicians were blinded to the randomization results. There was concealed allocation. The patients were followed until they died, their renal dysfunction resolved for 24 hours, or they were discharged from the ICU.
OUTCOMES MEASURED: The primary outcome was peak serum creatinine level. The secondary outcomes included duration of mechanical ventilation, length of ICU and hospital stay, and survival to hospital discharge.
RESULTS: After randomization, the 2 groups were similar in all characteristics measured (age, illness severity score, blood pressure, central venous pressure, urinary output, and serum creatinine). The dopamine group had a peak serum creatinine concentration of 245 micromols per L, compared with 249 micromols per L in the placebo group. This difference was not statistically or clinically significant. Survival to hospital discharge, survival to ICU discharge, and all other secondary outcomes were not significantly different. The trial drug and placebo were stopped at the same rate for suspected adverse effects.
Low-dose dopamine does not prevent renal failure in critically ill patients in the ICU. This study does not have enough statistical power to detect small changes in clinical outcomes, such as death or length of hospital stay. The study also does not address the use of low-dose dopamine as a prophylactic agent before the development of renal dysfunction.
BACKGROUND: Low-dose dopamine (2 (mg/kg/min) has long been used in the ICU setting in an attempt to preserve renal function in critically ill patients who are at significant risk for renal failure. This practice is based on evidence in healthy patients that low-dose dopamine increases renal blood flow, induces natriuresis and diuresis, and may prevent acute renal failure.
POPULATION STUDIED: A total of 324 patients from 23 ICUs in Australia and New Zealand who had a central venous catheter, had 2 or more changes of the systemic inflammatory syndrome (SIRS), and had at least one marker of early renal dysfunction (decreased urine output, elevated serum creatinine, or rapidly increasing serum creatinine). SIRS is a common response to a variety of severe clinical insults and is a marker of impending sepsis. One operational definition is 2 or more of the following: temperature greater than 38Þ C or less than 36Þ C, heart rate greater than 90, tachypnea (respiratory rate greater than 20), or hyperventilation (partial pressure of carbon dioxide in the arterial blood <32 mm Hg), WBC greater than 12,000 or less than 4,000 or greater than 10% immature neutrophils (bands), where these alterations represent an acute alteration from baseline without other known causes for such abnormalities.
STUDY DESIGN AND VALIDITY: This was a randomized double-blind study comparing the use of low-dose dopamine (n=161) with placebo (n=163) in patients with renal dysfunction. The patients were randomized to receive dopamine or placebo. ICU nurses, staff, and physicians were blinded to the randomization results. There was concealed allocation. The patients were followed until they died, their renal dysfunction resolved for 24 hours, or they were discharged from the ICU.
OUTCOMES MEASURED: The primary outcome was peak serum creatinine level. The secondary outcomes included duration of mechanical ventilation, length of ICU and hospital stay, and survival to hospital discharge.
RESULTS: After randomization, the 2 groups were similar in all characteristics measured (age, illness severity score, blood pressure, central venous pressure, urinary output, and serum creatinine). The dopamine group had a peak serum creatinine concentration of 245 micromols per L, compared with 249 micromols per L in the placebo group. This difference was not statistically or clinically significant. Survival to hospital discharge, survival to ICU discharge, and all other secondary outcomes were not significantly different. The trial drug and placebo were stopped at the same rate for suspected adverse effects.
Low-dose dopamine does not prevent renal failure in critically ill patients in the ICU. This study does not have enough statistical power to detect small changes in clinical outcomes, such as death or length of hospital stay. The study also does not address the use of low-dose dopamine as a prophylactic agent before the development of renal dysfunction.
BACKGROUND: Low-dose dopamine (2 (mg/kg/min) has long been used in the ICU setting in an attempt to preserve renal function in critically ill patients who are at significant risk for renal failure. This practice is based on evidence in healthy patients that low-dose dopamine increases renal blood flow, induces natriuresis and diuresis, and may prevent acute renal failure.
POPULATION STUDIED: A total of 324 patients from 23 ICUs in Australia and New Zealand who had a central venous catheter, had 2 or more changes of the systemic inflammatory syndrome (SIRS), and had at least one marker of early renal dysfunction (decreased urine output, elevated serum creatinine, or rapidly increasing serum creatinine). SIRS is a common response to a variety of severe clinical insults and is a marker of impending sepsis. One operational definition is 2 or more of the following: temperature greater than 38Þ C or less than 36Þ C, heart rate greater than 90, tachypnea (respiratory rate greater than 20), or hyperventilation (partial pressure of carbon dioxide in the arterial blood <32 mm Hg), WBC greater than 12,000 or less than 4,000 or greater than 10% immature neutrophils (bands), where these alterations represent an acute alteration from baseline without other known causes for such abnormalities.
STUDY DESIGN AND VALIDITY: This was a randomized double-blind study comparing the use of low-dose dopamine (n=161) with placebo (n=163) in patients with renal dysfunction. The patients were randomized to receive dopamine or placebo. ICU nurses, staff, and physicians were blinded to the randomization results. There was concealed allocation. The patients were followed until they died, their renal dysfunction resolved for 24 hours, or they were discharged from the ICU.
OUTCOMES MEASURED: The primary outcome was peak serum creatinine level. The secondary outcomes included duration of mechanical ventilation, length of ICU and hospital stay, and survival to hospital discharge.
RESULTS: After randomization, the 2 groups were similar in all characteristics measured (age, illness severity score, blood pressure, central venous pressure, urinary output, and serum creatinine). The dopamine group had a peak serum creatinine concentration of 245 micromols per L, compared with 249 micromols per L in the placebo group. This difference was not statistically or clinically significant. Survival to hospital discharge, survival to ICU discharge, and all other secondary outcomes were not significantly different. The trial drug and placebo were stopped at the same rate for suspected adverse effects.
Low-dose dopamine does not prevent renal failure in critically ill patients in the ICU. This study does not have enough statistical power to detect small changes in clinical outcomes, such as death or length of hospital stay. The study also does not address the use of low-dose dopamine as a prophylactic agent before the development of renal dysfunction.