A diverticulum is a herniation through a weak site of the bowel wall that produces a small outpouching [14]. When the diverticular wall is eroded by increased intraluminal pressure or inspissated food particles, diverticulitis may occur [15].
Diverticulitis is classified into simple (uncomplicated) and complicated types. Simple acute diverticulitis is a self-limiting and mild disease. It is defined as localized inflammation without any abscess or perforation [16]. Outpatient treatment is required for patients who have simple nonseptic diverticulitis, are immunocompetent, and can tolerate oral intake. However, patients with complicated diverticulitis must receive treatment specific to their complications, such as bowel obstruction, abscess, fistula, and perforation. When diffuse peritonitis is suspected given the findings of a physical examination, emergency surgery may be required even if imaging shows that the abscess is localized [17].
The gold standard diagnostic tool for acute diverticulitis is CT, in which complications can also be visualized. However, the schedule of CT at an ED may be delayed because of the high number of patients. The optimal use of CT for patients in whom complicated diverticulitis is suspected should be based on clinical and laboratory findings to minimize treatment costs and radiation hazards [18]. Therefore, recognizing the risk factors of complicated diverticulitis and providing the right treatment before CT imaging are crucial.
Some findings of the present study are in accordance with previous findings. In particular, right-sided diverticulitis was more prevalent than left-sided diverticulitis (70% versus 30%); this finding is compatible with reports from other Asian countries [19-21]. However, a higher number of patients with complicated diverticulitis had left-sided diverticulitis than right-sided diverticulitis (61.905% versus 38.095%); this finding is similar to the findings of previous Japanese and Korean studies [1, 19]. We also found that patients with complicated diverticulitis were older than those with simple diverticulitis (median age, 58 versus 44 years); this finding is also compatible with previous findings. For instance, in a Japanese retrospective multicenter study involving 1,112 patients, although right-sided colonic diverticulitis was more prevalent among the study population (70.1%), left-sided colonic diverticulitis was significantly more common among elderly patients (61.0%) [22]. Right-sided diverticulitis differs from left-sided diverticulitis in many respects. While right-sided diverticulitis is usually congenital and solitary [23, 24], left-sided diverticulitis is usually associated with secondary causes, including dietary factors, constipation, increased colonic pressure, defecation habits, and an irritable bowel. Consequently, left-sided diverticulitis more commonly occurs in older patients [25].
In our study, the WBC and neutrophil counts, MDW, and CRP level were higher in the complicated colonic diverticulitis group (p < 0.05, Supplementary Table 1); however, only the MDW was found to have a statistically significant association with complicated diverticulitis in the multivariate binary logistic regression analysis (p < 0.001, Table 1). The WBC count and CRP level are the most common indicators of the severity of intra-abdominal inflammation in the ED. A higher WBC count or CRP level usually indicates a higher level of inflammation. Several studies [18, 26-28] have attempted to calculate the optimal threshold for the WBC count and CRP level in distinguishing complicated diverticulitis from simple diverticulitis; however, so far, no consensus has been reached.
In addition to the WBC count and CRP level, two easily accessible hemogram-derived parameters, namely the NLR and PLR, have been used to predict complicated diverticulitis [29-31]. One study reported that the NLR could predict the need for surgical intervention more accurately than the CRP level and WBC count [29]. Palacios Huatuco et al. recently found that the NLR cutoff of 4.2 to be the best diagnostic approach, with sensitivity of 80% and specificity of 64%, for detecting complicated diverticulitis [30]. Mari et al. found that the PLR had a lower diagnostic accuracy than the NLR (AUC values, 0.67% and 0.75%, respectively) [31].
Circulating neutrophils and monocytes are the first response to pathogenic organisms. The MDW is a parameter that describes the size distribution of circulating monocytes. Several studies have reported that the MDW can be used for the early diagnosis of sepsis in the ED [7, 8, 32, 33]. Similarly, Şenlikci et al. found that the MDW can be used to differentiate mild pancreatitis from nonmild pancreatitis [13]. However, little known is about the efficacy of the MDW in detecting acute complicated diverticulitis. In our cohort, the MDW cutoff of 20.38 had sensitivity of 90.5% and specificity of up to 80.6%. Moreover, it had the largest AUC value (0.870) for the diagnosis of acute complicated diverticulitis. The AUC value of the MDW for complicated diverticulitis was higher than those of other inflammatory biomarkers—CRP (0.800), NLR (0.724), WBC (0.679), and PLR (0.662; Table 2 and Fig. 2).
The diagnostic accuracy of the MDW for complicated diverticulitis noted in our study was comparable with that of procalcitonin. In a previous study, the AUC of procalcitonin for complicated diverticulitis was 0.867, with sensitivity of 81% and specificity of 91% [34]. However, procalcitonin is not routinely used as a biomarker in EDs. In Taiwan, the national health insurance reimbursement price for procalcitonin tests is 1,000 New Taiwan dollars (NT$) [35], which is approximately four times the price for CBC determination (NT$270, including differential WBC count and MDW) [36,37]. Therefore, procalcitonin testing is preserved as an auxiliary test for patients with ambiguous diagnoses of sepsis or bacterial infection, which cannot be verified on the basis of the WBC count, NLR, or CRP level.
In our study, the MDW was the only inflammatory biomarker that was found to be a significant predictor of complicated colonic diverticulitis after adjusting for other covariables in multivariate binary logistic regression analysis (p < 0.001, Table 1). In previous studies, the MDW was found to have some advantages over other biomarkers. In particular, the MDW can be easily measured from the CBC through a blood test in the ED. In addition, the results are obtained faster than those of a biochemistry panel. Use of the MDW has been reported to improve both the clinical and economic outcomes of patients with sepsis in the ED, with the estimated time to antibiotic administration being reduced from 3.98 h to 2.07 h and US$3,460 being saved per hospitalization (US$23,466 versus US$26,926) [38]. By using a combination of the MDW and advanced imaging (CT), ED physicians will be able to diagnose complicated diverticulitis more accurately and in a timely manner, to initiate antibiotic therapy, and to convince surgeons regarding early intervention. However, recent guidelines have recommended avoiding the use of antibiotics for otherwise healthy patients with simple diverticulitis [39]. Hence, early and accurate diagnosis of simple diverticulitis by using the MDW will help reduce the use of antibiotics.
Limitations
To our knowledge, this is the first study to evaluate the utility of the MDW for diagnosing colonic diverticulitis in the ED. However, our study has some limitations. First, the MDW cannot be measured when the peripheral blood sample for a patient has a monocyte count < 100/μL. In our study, the MDW data of three patients were not available; these patients had simple diverticulitis. Second, because this was a retrospective study, medical records were not designed for research purposes and did not contain all parameters of interest to the investigators. For instance, the procalcitonin level was not measured for comparison with the MDW. Third, our classification of colonic diverticulitis was based on CT findings. CT has an accuracy of 98% in diagnosing acute diverticulitis; thus, misdiagnosis may occur in 2% of cases [40]. Nevertheless, abdominal CT imaging is still considered the gold standard for diagnosing acute diverticulitis and its complications [41]. Finally, this was a single-center study conducted in only one ED in East Asia; therefore, our finding that diverticulitis was more prevalent in the right colon may not be generalizable to all EDs and other populations. Further prospective studies with larger numbers of patients from multiple centers are needed to more accurately assess the role of the MDW in differentiating simple from complicated colonic diverticulitis.