Diverticulitis is classically described along a spectrum of presentations, yet there is currently a lack of rigorous investigation in outpatients who are thought to present with a less severe form of this disease. While practice guidelines present the standard diagnostic criteria of left lower quadrant abdominal pain, fever, and leukocytosis, there has been little attempt to determine whether these features are actually used by providers to define a mild case of diverticulitis [7
]. The present analysis uniquely examines outpatients with a possible diagnosis of diverticulitis, and demonstrates that many of them (>75%) lack one or more of these expected diagnostic criteria. As has been demonstrated for other diagnostic codes, this result indicates that the diverticulitis diagnostic code is applied independently of the expected diagnostic criteria in the outpatient setting, calling into question the accuracy of the diagnosis [16
]. Consequently, the outpatient population with diverticulitis as it is currently defined may be much smaller than previously perceived.
In order to maximize our capture of patients with a possible diagnosis of diverticulitis, we chose to select patients with the encounter diagnosis code for LLQ pain in addition to those with the diverticulitis code, hypothesizing that some providers might elect to use a less specific code in these presumably mild presentations. The absence of expected diagnostic criteria seen in patients with the diverticulitis code was also observed among those with the more general label of “LLQ pain.” Given the multiple diagnostic possibilities incorporated in this code, this may reflects appropriate diagnostic labeling by providers, as corroborated by our conclusion that a diverticulitis label was more correct in only 5% of these cases. However, the use of antibiotics among one-quarter of patients coded with LLQ pain suggests that a diagnosis of diverticulitis or other infectious etiology may be entertained in some cases, although perhaps with some hesitancy.
Our results raise initial concern that the entity of outpatient diverticulitis is much rarer than previously expected. However, despite a frequent lack of laboratory data and other elements of the classic diagnostic criteria, most patients labeled with diverticulitis (>80%) are still treated with antibiotics, raising questions about additional clinical factors which may contribute to providers’ implied diagnostic confidence. Perhaps the recommended diagnostic criteria do not apply to an outpatient population who may manifest an even milder form of the disease process than was originally perceived. In this setting, a different set of clinical elements may be required to make this diagnosis accurately, in order to justify the treatment decisions currently implemented by practitioners, including the decision to refer a patient for surgical consideration after multiple episodes of “uncomplicated diverticulitis”. Surgeons and primary care providers rely on the accuracy of diagnostic labels to facilitate good communication about the patient’s need for surgical intervention. The present findings thus hold significant importance for both parties in this diagnostic and management dilemma.
Some may interpret the practice patterns exposed in this analysis as inappropriate, resulting in over-labeling of outpatients presenting with a range of complaints with a common diagnosis of diverticulitis. In the clinical arena, the implications of over-diagnosis can be variable. Although it is unlikely to negatively affect the patient’s short-term outcome, it does result in a diagnostic label that is likely to be utilized repeatedly in future visits, potentially without further work-up. The questionable accuracy of the diagnosis will likely translate into repeated and possibly excessive antibiotic use. Regardless, the fact that none of these cases went on to require early emergent procedures or other operative interventions may attest to the benefits of overly aggressive intervention. Future analyses which improve our understanding of the rates of recurrence and complication in this population will enhance our ability to judge the risk of over-treatment against any possible benefit with regards to time, cost, and patient morbidity.
The present study examined patients and providers within a single academic medical center and its associated clinics, which may limit the generalizability of its findings to other patient populations. The frequency of missing data elements, particularly WBC count and temperature, are a potential limitation in interpreting our results. However, prior analysis of the electronic medical record in our system suggests these are “true missings,” i.e., data elements not ordered or obtained by the practitioner, rather than an error in information retrieval. Our conclusions presume that practitioners did not systematically neglect to order laboratory tests or record clinical data in patients more likely to have abnormal results. The accuracy of the diverticulitis diagnosis was rated by a single abstractor, who generally required the presence of at least 2 of the three expected diagnostic criteria in order to achieve a “Likely/Yes” rating. It is not known whether this decision rule in fact selects the “true” diverticulitis cases, as it is unique to the present analysis, and may be biased by the surgical background of the two abstractors. In addition, a rating of “Possible” was given to another third of these patients who were lacking even more diagnostic evidence, yet retained some possibility of a diverticulitis diagnosis. Given the recommendations presented in practice guidelines from multiple disciplines, we believe this strategy is likely to exclude few “true” cases.
Despite our anticipation that patients with outpatient diverticulitis might be found among those with a diagnostic code for either diverticulitis or LLQ pain, we found that only a small proportion of patients in either group had clinical data sufficient to convince the abstractor of the diverticulitis diagnosis. Without these classic diagnostic criteria (fever, leukocytosis, LLQ pain), abdominal imaging may play an important role in differentiating diverticulitis from other causes of abdominal pain such as irritable bowel syndrome [19
]. Despite this presumption, a minority of patients in our investigation had an abdominal/pelvic CT scan within 30 days of the studied encounter, with fewer than one-third of these scans demonstrating findings consistent with the diagnosis of diverticulitis. Future work will aim to examine the combinations of clinical features, imaging findings, and diagnosis codes which will most reliably select an accurate cohort of diverticulitis outpatients to address remaining questions concerning natural history, recurrence, complications, and optimal management.