This report identifies patients in a state-wide medical system presenting with diverticulitis in the outpatient setting, and describes the evaluation utilized by providers to support that diagnostic label. These results begin to address several knowledge deficits in understanding the outpatient portion of the diverticulitis spectrum, as prior study has been limited to hospitalized patients or anecdotal evidence from outpatient providers.[4
] The current analysis identified more than 2500 unique outpatient encounters for diverticulitis within a 5 year period, the great majority of which were in a clinic setting, rather than the emergency room. By comparison, we noted a total of 820 inpatient visits for diverticulitis in the same time period, far less than the number of outpatient encounters. With a lack of similar prior published reports, it is impossible to determine if this is comparable to the experience of other medical systems. However, given that only one diverticulitis episode per patient was included to ensure independence in this analysis, these counts are likely to underestimate the true number of visits initiated in the outpatient setting. As one considers the potential number of repeat outpatient visits and associated resources utilized (imaging, laboratory tests, medications etc), not to mention often-overlooked patient factors, such as time lost from work and decreased quality of life due to symptoms, the probable burden of diverticulitis on the health care system becomes quite large. Data from a U.S. survey conducted in 1980 attributed $300 million in annual health care costs to diverticular disease, yet this figure still primarily reflects those costs generated in the inpatient setting.[16
] The impact of the outpatient aspect of this disease process has not been estimated until this analysis, and even this crude measure indicates that the resource drain on providers, patients, and the health care system itself is likely to be quite substantial.
Current practice guidelines state that the diagnosis of diverticulitis may be made on clinical grounds alone, and that imaging should be used in select patients with severe or atypical symptoms as confirmatory tests.[9
] Indeed, the only study which specifically reports attributes and outcomes of “office practice” patients with diverticulitis dates back to the 1950’s and identified patients exclusively through clinical features including abdominal pain, fever, and leukocytosis.[7
] Our analysis focused on the objective measures of abdominal imaging and leukocytosis, due to data limitations preventing assessment of more subjective elements such as pain. We found that, despite being labeled with the ICD-9-CM code for diverticulitis, the overwhelming majority of patients seen in a clinic setting (86%) did not undergo abdominal imaging. In addition, for those with laboratory values recorded in the EMR, most Clinic patients (65%) did not have an abnormal WBC count. The patterns observed in this analysis imply that abdominal imaging and leukocytosis may not drive the diagnostic label of diverticulitis in the clinic setting. Instead, the diagnostic approach to patients presenting in Clinic with possible diverticulitis appears to be based on physical exam characteristics or other clinical evidence not captured in this analysis.
In contrast, patients seen in the emergency room frequently underwent abdominal imaging, especially CT scan. If outpatient practitioners are assumed to choose imaging in accordance with practice guidelines, this suggests that these patients were likely to have evidence of more severe disease, perhaps manifested by an elevated WBC count. However, leukocytosis was only observed in 69% of ER patients in this analysis. Thus, other factors, such as increased pressure to rule out confounding diagnoses and the ready availability of a variety of imaging modalities, likely contribute to the increased utilization of CT scans by ER practitioners. Although CT scan results were not reviewed during this analysis, the fact that all patients were labeled with diverticulitis suggests that the imaging findings were consistent with that diagnosis, and may have proved more influential to the provider’s decision than a lack of elevated WBC count in some cases. Thus, in contrast to the clinic setting, CT scans appear to be a key component of the diagnostic workup for patients presenting with presumed diverticulitis in the ER setting. Leukocytosis does not appear to be essential for diagnosis in either setting, as a significant proportion of patients were found to have normal WBC counts. This is in contrast to published practice guidelines, which indicate that leukocytosis is critical to the clinical diagnosis of diverticulitis, especially in the absence of abdominal imaging.[7
While clinical assessment alone may be sufficient for successful medical management of diverticular disease, and potentially more economical in the short-run, the lack of objective evidence, particularly imaging, is likely to raise concerns and questions should this patient be referred for surgical evaluation and treatment. Most surgeons hesitate to offer an elective operation to a patient whose prior diverticulitis episodes have no confirmatory imaging. The current findings reveal that a substantial number of patients, especially those evaluated in an outpatient clinic, do not receive such imaging as part of their diagnostic workup. By extension, these patients may not be strongly considered for elective colectomy upon initial referral for surgical consultation. While the cost-effectiveness of abdominal imaging for outpatient presentations of diverticulitis is not addressed in this study, the large proportion of patients diagnosed without imaging suggests that such an analysis will be important for future studies investigating the optimal outpatient management of this disease.
Urgent surgical intervention was rarely needed in our study population, with fewer than 2% of all patients requiring colectomy or abscess drainage in the 48-hour period surrounding diagnosis. This has been suggested previously, as large cohort studies have demonstrated successful non-operative management of acute diverticulitis in approximately 80% of hospitalized patients.[18
] Low rates of emergent operation are expected in the present study, given the less severe disease presentation anticipated in this cohort of outpatients. Inpatient admission rates within 24 hours following outpatient presentation were similarly low, with 30% of ER patients and 3.5% of Clinic patients requiring hospitalization after the encounter of interest. Early admissions were likely initiated for a trial of conservative medical therapy, including intravenous antibiotics, as rates of colectomy within 24 hours of the initial encounter are low. These findings suggest that while diverticulitis in the outpatient setting may be typically considered “uncomplicated” due to the rare need for emergent operation, a subset of patients will require more aggressive medical therapy on the basis of their clinical presentation. Further, as this analysis is limited to examining one outpatient episode and one subsequent inpatient episode, the full extent of the financial and quality of life burdens incurred by outpatients due to recurrence is assuredly underestimated. Although unique medical record numbers were available for all patients, investigation of recurrence events requiring ER evaluation or hospitalization beyond 24 hours was not reliably possible, due to potential losses-to-follow-up as patients might be anticipated to seek urgent or emergent care in facilities not affiliated with our medical system. A more in-depth evaluation as to the recurrence patterns of outpatient diverticulitis will, therefore, be crucial in making optimal management and treatment decisions for these patients, and should be taken into consideration in future analyses.
There are some limitations to this study. Implementation and adoption of the electronic medical record (EMR) has been an ongoing process in our medical system throughout the study period. Use of the EMR may create particular challenges related to missing data, as the absence of a test or other variable of interest may either indicate that the test was never ordered, or that the test results were simply not recorded in the EMR. This is especially true for laboratory data, as clinics have only adopted electronic reporting of results in recent years. Manual chart abstraction could be used to clarify the implications of missing data in future studies, but was not implemented in this analysis. In addition, this EMR-based analysis is limited to variables with discrete coding, and excludes information found in free-text format (i.e. finding of abdominal tenderness during the physical exam) due to the difficulty of exact matches, and thus may not fully capture all clinically relevant elements characterizing the patients seen in various outpatient settings. Finally, this retrospective EMR analysis relies on ICD-9-CM diagnosis codes to identify patients with diverticulitis. Although we presume that this diagnosis is correctly given, the accuracy is unknown, as validated studies on the identification of diverticulitis patients are lacking, and will therefore be the impetus of future study.
In conclusion, this analysis describes the subpopulation of diverticulitis patients presenting in the outpatient setting and the extent to which objective data (abdominal imaging and WBC count) contributes to making this diagnosis. In our medical system, patients labeled with diverticulitis are more commonly seen in an outpatient setting, and rarely require urgent surgical intervention or admission. Consistent with practice guidelines, abdominal CT scans are infrequently used in Clinic patients; in contrast, leukocytosis (when identified) is often absent. Thus, many outpatients are labeled with diverticulitis despite a lack of objective evidence, suggesting that other clinical factors persuade provider decision-making in this setting. These results motivate further investigation into the diagnostic criteria for diverticulitis, as accurate definition of this condition will be essential to answer remaining questions regarding the frequency and timing of recurrence, the influence of elective or emergent surgical management, and the quantifiable impact of outpatient diverticulitis on health care costs and patient quality of life.