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Original Research |
1 Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham & Women's Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115.
Received February 11, 2004;
accepted after revision November 29, 2004.
Address correspondence to K. J. Mortelé
(kmortele{at}partners.org).
Abstract
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MATERIALS AND METHODS. Three hundred forty-four consecutive patients with hematuria were evaluated with MDCT urography. Incidental extraurinary findings were classified into three categories according to their clinical significance (high, moderate, and low). Medical records were reviewed, and the cost of additional imaging examinations was calculated using 2002 Medicare reimbursements.
RESULTS. Extraurinary findings were detected in 259 patients (75.3%). Of these, 62 patients (18.0%) had highly clinically significant findings, including three cancers. Only 20 (32.3%) of the 62 patients with highly clinically significant findings underwent additional imaging for findings of high clinical significance; 10 (16.1%) were followed clinically, and 32 (51.6%) were not evaluated. The most prevalent highly clinically significant findings were pulmonary nodules and lymphadenopathy. Of the 344 patients studied, 116 (33.7%) had findings in which the highest level of clinical significance was moderate; 81 (23.5%) had findings of only low clinical significance. Nine patients (2.6%) underwent additional imaging for findings of moderate or low clinical significance. Overall, 29 patients (8.4%) underwent further imaging at a cost of $14,231 (average of $41.37 per patient).
CONCLUSION. Although incidental extraurinary findings were common at MDCT urography, only a small percentage of patients were imaged further. MDCT urography, when used to evaluate patients with hematuria, detects extraurinary disease without a substantial increase in per-patient imaging costs.
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With the introduction of MDCT, the entire abdomen and pelvis can be imaged in a single breath-hold with thin-collimated images [11]. As a result, the urinary tract can be imaged with a spatial resolution (in both axial and nonaxial planes) that is sufficient to image the urothelium. MDCT has been used to perform CT urography, an examination that includes unenhanced and enhanced images of the urinary tract including IV urography-like coronal images during the excretory phase [11, 12]. MDCT urography has been shown to depict normal ureters [11] and detect urothelial abnormalities [12]. Although not performed with MDCT, a recent study of 115 patients with asymptomatic microscopic hematuria found that CT urography had a better diagnostic yield than excretory urography [13].
As a result of these studies, the American Urological Association has stated that CT urography may be used in the initial evaluation of patients with hematuria [14]. In addition, the American College of Radiology rated CT urography highly as to its appropriateness in evaluating patients with hematuria [15].
In addition, relative to excretory urography, MDCT urography depicts structures outside the urinary tract and may detect extraurinary abnormalities and disease. Although this provides an opportunity to detect unsuspected serious disease, the incidental detection of benign findings may lead to unnecessary imaging tests that increase patient anxiety and imaging costs. Incidental extracolonic findings at CT colonography are common but are rarely evaluated further [16, 17]. As a result, the additional cost incurred by detecting extracolonic findings has been reported to be low [16, 17]. To our knowledge, the prevalence and impact on the additional imaging costs of detecting extraurinary findings at MDCT urography have not been evaluated.
Therefore, we conducted a retrospective noncohort study to assess the prevalence and characteristics of incidental extraurinary findings in patients undergoing MDCT urography for hematuria. We also assessed how often these findings were reevaluated with imaging and determined additional imaging costs incurred as a result of their detection.
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MDCT Urography Technique
MDCT urography was performed using 4-MDCT scanners (Somatom Volume Zoom,
Siemens Medical Solutions). A three-phase MDCT urographic protocol was used.
For the unenhanced phase, the abdomen and pelvis were scanned using 4.0
x 2.5 mm collimation. The kidneys were scanned during the nephrographic
phase, 100 sec after IV administration of 100 mL of 300 mg I/mL iopromide
(Ultravist 300, Berlex Laboratories), injected at a rate of 3 mL/sec, using
4.0 x 2.5 mm collimation. The abdomen and pelvis were scanned during the
pyelographic phase at 10-15 min using 4 x 1.0 mm collimation. The
contrast medium injection was followed by IV administration of 250 mL of
normal saline used to distend the urinary collecting system. For most scans,
165-mAs setting was used (range, 165-200 mAs), and a 120-kVp setting was used
in all patients. The unenhanced scans were reconstructed axially using 5-mm
sections and 5-mm increments. The nephrographic phase images were
reconstructed axially using 3-mm sections and 1.5-mm increments. The
pyelographic phase images were reconstructed axially using 5-mm sections and
5-mm increments and coronally using 3-mm sections and 3-mm increments.
Maximum-intensity-projection images were reconstructed in an anteroposterior
projection.
Data Acquisition
Soft-copy imaging data were evaluated using commercially available PACS
workstations. These images were reviewed using preset lung, soft-tissue, and
bone window settings, which could also be interactively adjusted by the
observer. Faculty in our division of abdominal imaging and intervention, which
consists of six abdominal radiologists with a minimum of 6 years' experience
with abdominal and pelvic CT scans, interpreted all CT urograms. All are
certified by the American Board of Radiology except one who trained abroad and
is board-certified in his country of origin. The radiologists examined the
images and generated clinical reports that included both urinary and
extraurinary findings. All extraurinary findings were tabulated by reviewing
the reports stored on our radiology information system.
Data Analysis
We considered abnormalities of the kidneys, intrarenal collecting system,
ureters, bladder, prostate gland, and seminal vesicles as urinary findings. We
considered abnormalities of all other structures, including the adrenal glands
and male and female reproductive systems (e.g., uterus, ovary, and testis), as
extraurinary findings. Incidental extraurinary findings were classified using
a modified version of a system used in a study of incidental extracolonic
findings at CT colonography
[17]. Findings were considered
incidental if there were no known symptoms related to the finding and if the
findings were not known at the time of MDCT urography study. Extraurinary
findings were divided into three categories on the basis of clinical
significance: high, moderate, or low. Patients were classified into four
categories: those who had findings of high clinical significance, those who
had findings that were at most of moderate clinical significance, those who
had findings of only low clinical significance, and those who had no
incidental extraurinary findings.
Findings were classified as highly clinically significant if they required prompt medical or surgical intervention or further workup. These findings included indeterminate masses (i.e., masses that could not be characterized confidently by the reviewers) of at least 1 cm in diameter in a solid organ (e.g., liver, spleen, pancreas), indeterminate lung nodules, indeterminate adrenal masses of any size, cystic ovarian masses, indeterminate bone lesions, abdominal lymph nodes measuring 1 cm or larger along their short axis, and masses or lesions that were considered likely malignant (e.g., lytic bone lesions).
Findings were classified as moderately clinically significant if they were benign but required evaluation or treatment at a later time. Examples of moderately clinically significant findings included gallstones, diverticulosis, atherosclerotic disease, uterine fibroids, adrenal hyperplasia or thickening, and pleural and pericardial effusions.
Findings of low clinical significance were benign findings unlikely to require further imaging or intervention. Examples included liver cysts, fatty liver, splenic and hepatic calcified granulomas, and hiatal hernias.
The type and number of incidental extraurinary findings were tabulated and categorized. Using our electronic hospital information system, we recorded the clinical follow-up, radiologic testing, and subsequent surgical procedures performed for extraurinary findings through August 2003 (minimum of 1 year after MDCT urography).
To assess false-negative extraurinary findings (e.g., missed malignancies) at MDCT urography, we reviewed all patients' records to determine whether subsequent abdominal or pelvic imaging (CT, MRI, or sonography) performed up to 1 year later reported a serious condition, such as a primary malignancy or a metastasis that was not detected at MDCT urography. In addition, medical records were reviewed up to 1 year later to determine whether subsequent complications resulted from cases in which extraurinary findings were not evaluated further.
The cost of subsequent imaging workup for the extraurinary findings was calculated using 2002 Medicare reimbursements, which included professional and technical components [18]. The cost of the workup of all findings was estimated [18].
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Highly clinical significant findings were found in 62 (18.0%) of the 344 patients. The most common findings were indeterminate lung masses (n = 15; size range, 1-15 mm across the short axis) and lymphadenopathy (n = 14). Less common were indeterminate liver lesions (n =5), ascites (n = 5), indeterminate adrenal nodules (n = 4), and abdominal aortic aneurysms (n =3) (Table 1). Nine patients (14.5%) had more than one highly clinically significant finding.
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Of the 62 patients with findings of high clinical significance, 20 underwent subsequent imaging for these findings. The time between MDCT urography and follow-up imaging studies ranged from 9 to 391 days with an average of 110 days. Forty-two patients did not undergo further imaging workup. Fourteen patients were followed clinically by either focused clinic visits or directed consultations. In 12 patients, the extraurinary findings were ignored, and the remaining 16 patients were patients for whom follow-up information could not be obtained from outside hospitals. The imaging workup of patients with findings of high clinical significance included 24 CT scans, five conventional radiographs, three SPECT scans, two sonograms, and one MRI examination.
Three patients had extraurinary malignant lesions discovered at MDCT urography. Of these, two were found to have enlarged retroperitoneal lymph nodes. In one of these patients, subsequent CT scans revealed no change. The patient underwent percutaneous biopsy of the enlarged lymph nodes and was diagnosed with a low-grade non-Hodgkin's lymphoma. The second patient with retroperitoneal lymphadenopathy was diagnosed with a low-grade non-Hodgkin's lymphoma after lymph node and bone marrow biopsies. One patient, who had a 1.5-cm lung nodule found at MDCT urography, subsequently underwent a dedicated chest CT examination and bronchoscopy with biopsy that revealed a stage IA (T1 N0 M0) adenocarcinoma of the lung. The tumor was resected, and the patient showed no signs or symptoms of recurrence at 12 months. Discovery of abdominal ascites in a patient with ovarian cancer, initially thought to be in remission, prompted an additional CT examination that confirmed peritoneal carcinomatosis.
Of the 42 patients (67.7%) with highly clinically significant findings who had no imaging follow-up for these findings, two patients were found to have subacute or acute appendicitis at MDCT urography. In one patient, there was no clinical or imaging workup. In the other, the patient presented again 3 months later with right lower quadrant pain, was diagnosed with chronic appendicitis on sonography, and underwent subsequent appendectomy. One patient was found to have sigmoid diverticulitis at MDCT urography, and clinical follow-up was recommended. One month later, the patient presented again with abdominal pain. CT scan at the time revealed a new large peri-sigmoid diverticular abscess. The patient underwent exploratory laparotomy with drainage of the abscess. At surgery, the abscess was found to have ruptured, with fecal matter in the peritoneal cavity. Sigmoid colectomy, right hemicolectomy, and small-bowel resection were performed. Unfortunately, the patient died 1 week later.
One hundred sixteen (33.7%) of the 344 patients had findings in which the highest level of clinical significance was moderate. Two hundred twenty-two moderately clinically significant findings were found in 147 patients (42.7%) (Table 2). This included 31 patients who also had highly clinically significant findings. The most common findings were diverticulosis, cholelithiasis, atherosclerosis, adrenal adenoma, inguinal hernia, fibroid uterus, pleural effusion, biliary dilatation, and cardiomegaly. Only six (5.2%) of the 116 patients with at most moderately clinically significant findings underwent subsequent imaging workup. These examinations included MRI with MR cholangiopancreatography (MRCP) for biliary dilatation, pelvic CT for a sclerotic bone lesion (confirmed to be a bone island), radiography of the chest for pleural effusion, pelvic sonography for suspected uterine fibroids, and two abdominal CT studies for adrenal lesions that were likely adenomas. Subsequent imaging confirmed the original impression in all cases. In the patient with biliary dilatation, a cystic pancreatic mass was found at MRI with MRCP and subsequently was diagnosed as a serous cystadenoma on the basis of the imaging findings and a low carcinoembryonic antigen level of 24 ng/mL in the cyst fluid.
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Eighty-one patients (23.5%) had findings of only low clinical significance. Two hundred seventy-five findings of low clinical significance were found in 190 patients (55.2%) (Table 3). This included 109 patients who also had highly or moderately clinically significant findings. The most common of these were cysts or small (< 1 cm) lesions in the liver, degenerative changes of the spine, minimally enlarged (< 1 cm) abdominal lymph nodes, hernias, fatty liver, pulmonary atelectasis and scarring, and splenic and hepatic granulomas. Only three (3.7%) of the 81 patientswho had only findings of low clinical significance underwent subsequent follow-up imaging for these findings. One patient had an abdominal sonogram for a liver lesion that was found to be a cyst. Another underwent CT for evaluation of a liver lesion that was also determined to be a cyst. The third patient had a chest CT scan to confirm that a lung base lesion was a granuloma. In all cases, subsequent imaging workup revealed benign findings.
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Of all findings that were not imaged further, neither adverse sequelae nor clinically significant disease related to these findings developed. In addition, review of reports of subsequent imaging tests performed within a year of MDCT urography yielded no serious conditions that were not detected at MDCT urography, such as a primary malignancy or a metastasis.
Considering all the findings in all three clinical significance categories, a total of 29 patients (8.4%) had follow-up imaging tests performed. Based on Medicare reimbursements, including professional and technical fees, the total cost of all follow-up imaging studies was $14,231 (average of $41.37 per patient in 344 patients); $10,974 was spent for high, $2,403 for moderate, and $854 for low clinical significance findings. Of the patients in the high clinical significance category, had all the recommendations in the radiology reports been followed, an additional 12 patients would have undergone additional imaging—adding $3,779 to the overall follow-up imaging cost.
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This study aims to assess both the prevalence of extraurinary findings at CT urography performed with an MDCT scanner and their impact on imaging costs. Extraurinary findings were common, occurring in more than three of every four patients. Most findings were of low (275 findings, 48.4%) or moderate (222 findings, 39.1%) clinical significance. In addition, only nine patients with low or moderately clinically significant findings underwent further imaging workup for these findings. In terms of imaging cost, only $3,257 (22.9% of the total) was spent for findings of low and moderate clinical significance. Therefore, referring physicians considered most incidental extraurinary findings to be benign and further imaging workup unnecessary.
A minority of patients (62, 18.0%) had highly clinically significant findings. Although costs were modestly increased due to subsequent imaging workup of 20 of them, the serendipitous discovery of three cancers prevented future morbidity, mortality, and their attendant costs if they had been diagnosed at a later symptomatic stage. In one patient, for example, a stage IA (T1 N0 M0) adenocarcinoma of the lung was detected at MDCT urography and was subsequently resected. Patients with stage IA (T1 N0 M0) non-small cell carcinoma disease have a favorable prognosis, with a cumulative 5-year survival of 61% [19, 20].
This study illustrates that detecting extraurinary findings may be important because significant morbidity and mortality may be prevented. For example, MDCT urography detected diverticulitis but because it was not treated promptly, complications set in. Studies have shown that conservative treatment with bowel rest and antibiotics is successful in approximately 70-100% of patients with acute uncomplicated diverticulitis [21, 22]. However, perforated diverticulitis has a mortality rate of 6% for purulent peritonitis and 35% for fecal peritonitis [23]. This case points out that although ignoring clinically significant findings at MDCT urography may decrease costs in the short term, the overall cost, morbidity, and mortality may increase due to subsequent complications. However, early detection does not always improve survival. Indeed, a full analysis of the health benefit of detecting extraurinary findings was not part of our study and, therefore, it cannot be assumed that their earlier detection provides a net health benefit. This uncertainty can only be resolved by randomized clinical trials, which eliminate early detection biases.
The rate of highly clinically significant findings (12.5%) at MDCT urography was similar to the 10-11% reported at CT colonography [16, 17]. Rates were likely similar because both examinations used CT and the same body part was imaged. Also, age and sex distributions of the study populations were similar. The mean age of subjects examined with CT colonography was 63 years [16] and 64 years [17], whereas ours was 56 years. The proportion of men varied with one study reporting findings for a study group composed of 55.3% men [16] and the other, 62.6% men [17]. Our study population included 57.6% men.
Our results may not be generalized across all institutions. Results may differ depending on MDCT urography technique, how radiologists report extraurinary findings, and how aggressive radiologists are about recommending follow-up. Also, referring physicians' responses to radiologists' recommendations may differ. Although the relatively low rate of referring physicians' response to our recommendations may be due to the retrospective methodology of the study with no coordination with the referring physician medical staff, lack of compliance with recommended follow-up in medicine has been reported previously [24]. Patient populations also may differ with respect to factors such as age, sex, and comorbidities that may affect the prevalence of clinically significant findings. Also, we understand that the categorization of findings as to their clinical significance was subjective. However, there is no published consensus opinion as to what constitutes "significant" findings, in part because clinical significance varies from patient to patient. We opted to use a previously published and relatively conservative classification so as not to miss serious disease and so our results would be comparable with results obtained from prior studies using CT colonography.
A final limitation of our study is that we analyzed the impact of detecting incidental extraurinary findings only on subsequent imaging costs; we did not analyze additional cost factors, such as clinical and surgical costs, lost time from work, time, and travel expenses. Also, because charges and actual cost of follow-up studies vary among institutions and true cost determination is difficult, we reported the more constant and widely applicable Medicare reimbursement values as estimates of expenses to the health care system. We realize that Medicare reimbursement fees may be a vast underestimation of the real charges and actual costs.
In conclusion, extraurinary findings were common at MDCT urography. Most were of low or moderate clinical significance and were considered benign. Of the patients with only low or at most moderately clinically significant findings, only nine underwent additional imaging studies resulting in an additional $3,257 in imaging cost. Highly clinically significant findings comprised 71 (12.5%) of the findings and added $10,974 (77.1%) to the cost of follow-up imaging. In total, examining 344 patients with hematuria led to spending only $14,231 for imaging workup of extraurinary findings (average of $41.37 per patient). This study shows that MDCT urography can provide valuable additional information regarding extraurinary findings without a substantial increase in perpatient imaging cost.
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3 cm) renal masses: correlation of spiral CT features and
pathologic findings. AJR 1994;163
: 597-605
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