Original Contribution

Does diagnosis change as a result of repeat renal colic computed tomography scan in patients with a history of Kidney stones?

Adam Goldstone MD^a,b,?, Andrew Bushnell MD^c

^aUniversity of Vermont College of Medicine, Burlington, VT 05405, USA

^bDepartment of Emergency Medicine, North Shore University Hospital, Manhasset, NY 11030, USA ^cDivision of Emergency Medicine, Department of Surgery, University of Vermont College of Medicine, Burlington, VT 05401, USA

Received 13 September 2008; revised 26 November 2008; accepted 28 November 2008

Abstract

Study objective: We sought to determine the incidence of alternative diagnosis in patients with a history of kidney stones who experience recurrent symptoms and undergo repeat computed tomography (CT) imaging at their return to the emergency department (ED).

Methods: This was a retrospective chart review of ED patients at a tertiary care hospital. Inclusion criteria were all adult ED patients who received a repeat CT for renal colic, after having previously received the diagnosis of obstructive kidney stone confirmed by CT, in our ED. Patients were identified by reviewing the charts of those patients with repeat visits to the ED after January 1, 2004, in which they complained of symptoms suggestive of renal colic and received a CT scan. We determined the frequency of the same diagnosis on repeat CT scan in this population compared with the frequency of alternative diagnosis.

Results: Two hundred thirty-one patients met criteria for the study. Fifty-nine percent were male. One hundred eighty-nine (81.8%) patients had no change in diagnosis as a result of a repeat renal colic CT scan. Twenty-seven (11.6%) patients received an alternative diagnosis that did not require urgent intervention, and 15 (6.5%) patients received a diagnosis that did require an urgent intervention.

Conclusion: Repeat CT imaging of patients with known nephrolithiasis changed management in a minority of patients (6.5%). Knowing the frequency of alternative diagnosis in this population may help clinicians and patients balance the risks and benefits of repeat renal colic CT scans in patients with a history of kidney stones who return to the ED with similar symptoms.

(C) 2010

* Corresponding author. North Shore University Hospital, Department of Emergency Medicine, 300 Community Drive, Manhasset, NY 11030, USA. Tel.: +1 301 785 4531.

E-mail address: [email protected] (A. Goldstone).

Background

It has been shown in previous studies that computed tomography (CT) scans are the most accurate and definitive way to detect renal stones in patients presenting with flank

0735-6757/$ - see front matter (C) 2010 doi:10.1016/j.ajem.2008.11.024

pain [1]. These exams, however, are not without potential harm [2,3]. It is estimated that the risk of fatal cancer from an abdominal CT scan is approximately 0.05% per scan. At 10 mSv, an abdominal CT scan is equivalent to about 500 chest radiographs [4]. Furthermore, CT scans constitute a sub- stantial cost burden to the patient, hospital, and health care system. Previous studies have looked at patients presenting to the emergency department (ED) with flank pain and noted significant findings other than nephrolithiasis. Hoppe et al in 2006 found that of 1500 patients presenting to the ED with acute flank pain, 360 patients had alternate findings without nephrolithiasis or ureterolithiasis. Twenty-four percent of those patients had findings that required immediate attention such as appendicitis and cholecystitis [5].

These studies, however, do not address the population of patients who present with a history of CT-proven kidney stones. Because repeat CT imaging of the abdomen and pelvis increases the risks, it is important to understand the likelihood that repeat CT scans will have a clinical impact in the ED. We reviewed cases in which patients diagnosed with nephrolithiasis returned with recurrent symptoms and received a repeat CT scan. We determined the frequency of the same diagnosis on repeat CT scan in this population compared with the frequency of alternative diagnosis.

Methods

This was a retrospective chart review of ED patients at an academic, tertiary care hospital with 55,000 visits per year. Approval was attained from the human research review board at our institution. Charts were selected for review by performing a search of the hospital electronic billing database for all patients 18 years or older with an ED visit between the dates of January 1, 1997, and December 31, 2007, who met the following inclusion criteria: billed for a visit to the ED; billed for noncontrast abdominal and pelvic CT scan (renal colic CT); and received a diagnosis of renal colic, ureterolithiasis, or urolithiasis. A patient’s history of CT-proven kidney stones was confirmed by reviewing the patient’s CT scan report during their initial ED visit. All CT reports were read by board-certified radiologists.. The results of that initial search were then filtered for those patients who had a subsequent visit to the ED, between January 1, 2004, and December 31, 2007, in which they were billed for another noncontrast abdominal and pelvic CT scan..

All charts for the filtered group of patients were reviewed to determine whether they met the following final criteria for the study. First, the patient’s renal colic CT scan had to be ordered by a physician or mid-level staff working in the ED. computed tomography scans ordered by a urologist or after the patient had been admitted were not included to limit the study to only patients presenting to the ED. Second, the renal colic CT scan had to be ordered as a result of clinical

suspicion for kidney stones. This was confirmed by both reviewing the patients’ ED notes and the documented indication for the CT scan. Patients, for example, who presented with clinical suspicion for appendicitis but received a renal colic CT because of an intravenous contrast allergy were not included in the study. Finally, patients who had had ureteral stents placed before their return ED visit were not included as the indication for the CT scans tended not to confirm kidney stones but to evaluate the function of the stents and the progress of the obstructing stones.

Relevant ED notes and Radiology reports were reviewed either electronically or on paper through the medical records department at our institution. One abstractor reviewed all patient data and was not blinded to the hypothesis of the study. The same standardized data abstraction form was used for all charts reviewed. Meetings took place throughout the chart review to verify the accuracy and standardization of data abstraction.

Charts of patients were reviewed to obtain laboratory values, initial vital signs, and Physical exam findings. Patient outcomes were divided into 3 categories. The first category included those patients whose diagnosis did not change as a result of their CT scan during their return ED visit. These patients received a diagnosis describing an obstructive kidney stone or received a diagnosis of abdominal pain of unknown etiology via the International Classification of Diseases, Ninth Revision, Coding system. The second category included patients who had a change in diagnosis, but that change did not require any intervention other than pain control. The third category included patients who did have a change in diagnosis and that diagnosis required an intervention including surgery, admission, or administration of antibiotics.

Results

An initial search of the database yielded 310 patients who met the inclusion criteria. Review of individual records eliminated a total of 79 patients. Eighteen patients were eliminated because there was no stone seen on their initial CT scan. An additional 40 patients did not meet criteria for a subsequent visit to the ED with recurrent symptoms. Twelve more patients were removed because their initial CT was not ordered by ED staff. We were unable to locate records of 7 patients to verify a stone had been seen on their initial CT scan. Finally, 2 more patients were eliminated because their subsequent visit to the ED was due to complications of recently placed ureteral stents. 231 patients met full criteria for the study (Chart 1). Of the 231 patients, 59% (137/231) were male (95% confidence interval [CI], 53%-65%). The mean age for males was 44 years among all patients and 45 years for females (Table 1). Eighty-two percent (189/231) of the patients did not receive an alternative diagnosis after repeat renal colic CT (95% CI, 76%-86%). We found 42

Chart 1 Patients eliminated from the study after initial database search.

(18%) patients who upon their return visit to the ED with symptoms suggestive of renal colic received an alternative diagnosis after a repeat CT scan (95% CI, 14%-24%).

There were 15 (6%) patients who received an alternative diagnosis that required an intervention (Table 2) (95% CI, 4%-11%). The most common alternative diagnosis (7/15 patients) was acute pyelonephritis. The remaining 8 (3.5%) included 2 patients with diverticulitis; 2 had appendicitis; and the remaining 4 patients had pneumonia, Small bowel obstruction, cholecystitis, and Pelvic inflammatory disease. There were 27 patients who received an alternative diagnosis that did not require an urgent intervention (Table 2). Eighteen of these patients had musculoskeletal

Table 1 Results

pain. The remaining diagnoses were hematuria, ovarian cyst (2 patients), dysuria (2 patients), fever, viral syndrome, female genital symptoms, and zoster infection.

Among the 189 patients who did not receive an alternative diagnosis as a result of repeat CT scan during a subsequent visit to the ED, 63% (119/189) were male (95% CI, 56%- 70%). Twenty-seven patients (12%) received an alternative diagnosis that did not require an intervention; 33% were male (95% CI, 18%-52%). Fifteen patients received an alternative diagnosis that did require an intervention. Sixty percent (9/15) of these were male (95% CI, 33%-83%).

The mean age for patients who received no change in diagnosis as a result of repeat CT scan during a subsequent

Diagnosis category		No.	of patients (%)	No. of ED visits	No.	of males (%)	Mean age (y)
All categories		231		288	137	(59.3)	M: 44, F: 45
No change in diagnosis as a		189	(81.8)		119	(62.9)	44.5
result of repeat CT scan
	Received a diagnosis of renal	147	(63.6)	165
	colic or ureterolithiasis
	Received a diagnosis of	25	(10.8)	28
	abdominal pain of unclear
	etiology
	Have received both a diagnosis	17	(7.3)	35
	of renal colic and a diagnosis
	of abdominal pain of unclear
	etiology on separate visits
Patients who have received		27	(11.6)		9	(33.3)	43.7
an alternative diagnosis not
requiring urgent intervention
Patients who have received an		15	(6.5)		9	(60)	49.3
alternative diagnosis requiring
urgent intervention
	Non-pyelo significant	7	(3.5)		7	(88)	50.3
	Alternative diagnoses

Requiring urgent Intervention No. of patients
Acute Pyelonephritis	7
Diverticulitis	2
Appendicitis	2
Small bowel obstruction	1
Pneumonia	1
Female pelvic inflammatory disease	1
Cholecystitis	1
Total	15
Nonurgent diagnoses Musculoskeletal pain	18
Dysuria	2
Ovarian cyst	2
Hematuria	1
Fever	1
Female genital symptoms NOS	1
Viral syndrome NOS	1
Zoster infection	1
Total	27

visit to the ED was 44.5 years (95% CI, 42.2-46.9). The mean age for patients within the category that had an alternative diagnosis that did not require urgent intervention was 43.7 (95% CI, 37.2-50.0) years, and the mean age was

Table 2 Alternative diagnoses

49.3 (95% CI, 40.2-58.4) years for patients who required an urgent intervention as a result of an alternative diagnosis.

Discussion

The use of computed tomography has increased significantly as its availability and its accuracy in diagnos- ing pathology has become better [6]. There are approxi- mately 62 million CT scans conducted per year [7]. And although the use of noncontrast abdominal and pelvic CT scans to diagnose kidney stones has become the new gold standard with both high specificity and sensitivity, it does not come without risk [2,3,8]. Our study showed that among patients with a history of CT-proven kidney stones, most of the patients who are scanned again because of recurrent symptoms will have no change from their prior diagnosis. Furthermore, among those patients who did receive an alternative diagnosis, an even smaller fraction had a change that would require an acute intervention. Our study suggests that EDs could greatly reduce the number of CT scans ordered for patients with a history of kidney stones, but there is a small but not negligible risk of missing a more serious diagnosis such as pyelonephritis appendicitis or diverticulitis. The number of patients with an alternative diagnosis requiring a Change in management can be further reduced to 3.5% by attaining a urinalysis of every patient that should be done anyway. Knowing the chief offenders in this group of diagnoses should help with decisions about

using safer alternative imaging tests such as ultrasound as well as laboratory tests initially in patients with a prior recent CT.

Our study population visited our institution’s ED 288 times. A number of patients were found during chart review to have had numerous renal colic CT scans with multiple patients having 5 scans in the last 10 years. This does not include visits to surrounding community hospitals, CT scans ordered by primary care physicians or urologists, and other types of CT scans. The number is undoubtedly higher for some patients.

The effective dose delivered by a multidetector CT scanner using a conventional unenhanced abdomen and pelvis CT scan has been found to be more than 12 times more than a KUB with sonography. Katz et al studied the effective radiation dose of repeated unenhanced CT scans and found a number of patients accumulating an effective dose of ionizing radiation of more than 100 mSv. Studies based on atomic bomb victims and radiation workers show a significantly increased risk of fatal cancer in patients with a protracted exposure of 50 to 100 mSv or more [9]. Although there have not been any large studies directly looking at cancer risk from CT scans specifically, there is certainly convincing indirect evidence that CT scans are not completely harmless.

Our study had significantly more men than women, which reflects the overall higher incidence of kidney stones in men. Within the group that did have a change in diagnosis as a result of repeat CT scan, there was no significant difference in the number of males vs females. This suggests that one sex is no more likely to have a change in diagnosis than another given they present with symptoms of renal colic. No single age group was more likely to have an alternative diagnosis after a repeat CT scan because there was no significant difference among the mean ages between those who had a change in diagnosis and those who did not.

A similar study was done by Hoppe et al (2006) that looked at the rate of alternative diagnosis among patients presenting with flank pain. Hoppe divided the diagnoses into

3 categories: those that required immediate intervention, those that required close follow-up, and those that had little clinical significance. He found that there was a large enough percentage of patients with flank pain that had an emergent alternative diagnosis that a CT scan was the modality of choice to evaluate this chief complaint [5].

The study of Hoppe et al, however, evaluated any patient presenting with flank pain regardless of their medical history. Our study looked only at the subset of the population who had CT-proven kidney stones during a prior visit to the ED. Our study reflects a population of patients already prone to kidney stones, which in effect increases their risk of being diagnosed with another, especially when they are experiencing similar symptoms. Also, many patients who have had kidney stones in the past are able to give the history during subsequent episodes that their pain is familiar. Patients with a history of kidney

stones also might report that their symptoms are different from their prior episode and thus lead the physician toward an alternative workup.

The rate of alternative diagnosis in the study of Hoppe et al (24%) was similar to ours (22%). Significant alternative diagnosis was also comparable (5% vs 6.5%). The study of Hoppe et al focused on patients presenting with acute flank pain, whereas our study broadened the inclusion criteria based on the clinician’s clinical suspicion for kidney stone. It is unclear how our results would differ if we further filtered our patient population to those only presenting with flank pain. It must be acknowledged, however, that there is still a risk of missing a potentially dangerous diagnosis by not performing a CT scan even if a patient has a history of kidney stones.

Our findings are limited by the methodology, as a retrospective chart review study at a single institution. Chart review techniques in emergency medicine research have been well described, and we were careful to use a standardized methodology [10-13]. Accuracy in the elec- tronic patient billing record including the International Classification of Diseases, Ninth Revision, codes for diagnosis was assumed as this was how we identified our patient population. For patients discharged from the ED with an unclear diagnosis, no follow-up data were attained to see whether or not they returned to ED later and subsequently received an alternative diagnosis. The study was limited by including only patients presenting to the ED and CT scans ordered by emergency physicians or mid- level ED staff. It does not reflect patients who present to their primary care physicians or follow-ups with urology. Furthermore, it does not reflect those patients who did not have repeat CT scan imaging, so we are not able to compare outcomes with a control group. In addition, our study did not take into account provider variability; for example, some providers may order repeat CT scans frequently while others may not. Finally, as a retrospective study, we are unable to query providers as to the particular reasons for repeat CT scan, besides the written indication provided on the medical record.

Patients who experience multiple episodes of renal colic are exposed to significant amounts of radiation throughout their life. Among male and female adults with a history of CT-proven kidney stones who present to the ED with symptoms suggestive of renal colic, a noncontrast abdomen and pelvic CT scan will yield a significant alternative diagnosis in few but not negligible number of patients. Our study should help clinicians understand the risks and benefits of performing a repeat CT scan in the subset of patients who have a history of kidney stones and return to the ED with recurrent symptoms. Further prospective evaluation could be

used to develop rules about when to order repeat CT scanning in a patient with a history of kidney stones including the use of alternative tests such as ultrasound. This would not only reduce radiation exposure.in patients who frequently experience renal colic but also reduce health care costs for patients and EDs.

Acknowledgments

Kalev Freeman, MD, PhD (University of Vermont College of Medicine Department of Surgery): manuscript revision.

Alan Howard (University of Vermont-Academic Com- puting Services, Burlington, Vt): technical assistance in data collection.

References

1. Catalano O, Nunziata A, Altei F, Siani A. suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography. AJR Am J Roentgenol 2002;178:379-87.
2. Katz SI, Saluja S, Brink JA, et al. Radiation dose associated with unenhanced CT for suspected renal colic: impact of repetitive studies. AJR Am J Roentgenol 2006;186:1120-4.
3. Denton ER, Mackenzie A, Greenwell T. Unenhanced helical CT for renal colic-is the radiation dose justifiable? Clin Radiol 1999;54: 444-7.
4. Dixon AK, Dendy P, Greenwell T. Sprial CT: how much does radiation dose matter? Lancet 1998;352(9134):1082-3.
5. Hoppe H, Studer R, Kessler TM, Vock P, Studer UE, Thoeny HE. Alternate or additional findings to stone disease on unenhanced computerized tomography for acute flank pain can impact manage- ment. J Urol 2006;175:1725-30.
6. Tack D, Sourtzis S, Delpierre I, et al. Low dose unenhanced multidetector ct of patients with suspected renal colic. AJR Am J Roentgenol 2003;180:305-11.
7. Brenner DJ, Hall DP. Computed tomography-an increasing source of radiation exposure. N Engl J Med 2007;357:2277-84.
8. Hamm M, Knopfle E, Wartenberg S, et al. Low dose unenhanced helical computerized tomography for the evaluation of acute flank pain. J Urol 2002;167:1687-91.
9. Brenner DJ, Doll R, Goodhead DT, et al. Cancer risks attributable to low doses of ionizing radiation: assessing what we really know. Proc Natl Acad Sci U S A 2003;100:13761-6.
10. Gilbert EH, Lowenstein SR, Koziol-McLain J, et al. Chart reviews in emergency medicine: where are the methods? Ann Emerg Med 1996; 27:305-8.
11. Badcock D, Kelly AM, Kerr D, et al. The quality of medical record review studies in the international emergency medicine literature. Ann Emerg Med 2005;45:444-7.
12. Worster A, Bledsoe RD, Cleve P, et al. Reassessing the methods of medical record review studies in emergency medicine research. Ann Emerg Med 2005;45:448-51.
13. Lowenstein SR. Medical record reviews in emergency medicine: the blessing and the curse. Ann Emerg Med 2005;45:452-5.