In this retrospective review of 141,481 emergency colectomies (2010–2018) in adult patients, 13.22% had emergency readmissions within 6-months for colectomy-related complications. The majority (61.63%) of these occurred in what was defined as the “late” readmission period (> 30 days post-colectomy). A previous study of unplanned readmissions in the 30-days post-discharge from both elective and emergency procedures in 9 common surgical specialties found that 8.8% had unplanned readmissions [8], which is substantially lower than our study (where we found a 22.6% emergency readmission rate in the 6-month post-operative period); however this could be due to the fact that < 7% of these cases were colectomies. Also, having a cohort of only emergency cases, along with a longer follow-up period, may further account for the observed difference. Another study, that explicitly explored follow-up after 30 days, looked at just over 10,000 adults (18–65 years) with a BlueCross BlueShield health plan having undergone a colorectal procedure (elective and emergency) and found that 23.3% had a readmission within 90-days after discharge [9]. Readmissions were similarly subdivided into “early” and “late” readmissions; 52.6% occurred in the first 30 days post-discharge and the remainder between 31 and 90 days post-discharge, proportions that are similar to our study, which only looked at emergency colectomy.

In our study, the three main reasons for readmission in both the “early” and “late” readmission periods were infection, complications related to the gastrointestinal tract (including ileus, persistent vomiting, need for total parenteral nutrition, adhesive bowel obstruction), and bleeding. Interestingly, however, compared to our study, the burden of stoma-related complications and renal complications was 4.97 and 1.48 times greater, respectively, in the “late” readmission group compared to the “early” readmission group. Wong et al. identified similar reasons for emergency readmission in a retrospective review of 1763 colectomies and proctectomies and associated emergency readmissions within the 30-day post-operative period, with the most common reasons for readmission being ileus/nausea and vomiting (12%), intra-abdominal abscess or leak (13%) and superficial surgical site infections (8%) [4].

Predictors of “late” readmission included female gender, open surgery, sigmoidectomy, a history of recent weight loss, and high APR-DRG mortality score (4) when compared to “early” readmission. Wick et al. similarly divided their cohort into “early” (post-discharge days 0–30) and “late” readmissions (post-discharge days 31–90), and only reported on factors associated with “early” readmissions, which included surgical site infection at index admission, primary diagnosis of colon cancer, proctectomy or colectomy, discharge disposition to non-home setting, index admission LOS ≥ 7 days, and APR-DRG severity of illness score 4 [9]. These findings suggest that with respect to emergency colectomies, sicker patients or more complicated procedures put patients at greater risk of having a complication that will require readmission in the “late” post-operative period.

The cost of readmission was slightly greater in the “late” readmission group [$37,936 (IQR $20,464–$73,835)] compared to the “early” group [$34,374 (IQR $18,386–$68,014] and this was also the case on linear regression, accounting for relevant covariates (OR $1717.09 USD; 95%CI $1717.05–$1717.12). While the difference in individual admissions may not be clinically relevant, the fact that more than half of the readmissions for patients who underwent emergency colectomies occur in a time period that is often overlooked by studies reporting on emergency colectomy (i.e., beyond POD30) makes the aforementioned findings impactful. Given the 11,524 patients readmitted in the “late” group, over $437 million would not have been captured for this cohort, which represents approximately $46 million per year over the 9 years represented in the study (half of each year captured).

This study supports the need for attention to longer follow-up post-emergency colectomy, especially since most preventable complications (e.g., stoma- and renal-related-complications) occurred in the “late” readmission group. Given the current state of most healthcare systems, expanding the follow-up for a sub-set of patients at greater risk of having a complication in the “late” post-operative period may be a more effective use of resources. This study demonstrated that patients with recent weight loss and those with higher post-operative risk scores for peri-operative morbidity and mortality were at increased risk of having “late” complications requiring readmission. With the recent adoption of the acute care surgery (ACS) models for emergency general surgery [10,11,12], emergency cases, including the emergency colectomies studied in this paper, are more often performed by on-call surgeons, as opposed to the sub-specialists who typically care for these patients on an elective basis. Anecdotally, the follow-up of patients operated on an emergency basis tends to be limited to the first post-operative visit usually coinciding with POD30, running the risk of missing “early” signs of symptoms that foreshadow preventable readmissions.

Major strengths of our study include cohort size and length of follow-up. The use of data from a large national dataset allows for logistic and linear regression analysis using multiple variables. Moreover, as data originated from all types of centers in the United States, representing patients from a wide variety of sociodemographic backgrounds, the observed findings are generalizable. This study was designed to limit information bias by having a standard follow-up time for all patients (6-month following emergency colectomy). This could also be interpreted as a limitation because it required reducing our cohort to half its original size, although there were no significant differences between our final cohort and the excluded cohort (data not shown). Furthermore, this could have also led to underestimating readmissions, as NRD only captures patients from the same state, meaning that if a patient moved to a different state following their colectomy, readmissions occurring in their new state would not be captured. Finally, the broad eligibility criteria and large size of this cohort also allowed for reduced selection bias in that all individuals originated from the same initial study population.

Several limitations of our study should be noted. First, using diagnostic and procedure codes for identifying post-operative complications does not precisely define colectomy-related complications and thus the list that we used was curated based on expert knowledge and an iterative review of the main diagnosis codes for readmitted patients. It is likely that there were relevant codes that were not used, and that the totality of colectomy-related complications may have been underestimated. Moreover, given the retrospective cohort design of this study, using a large national database, colectomy-related complications can only be associated with the pre-dating emergency colectomy and causation cannot be ensured. Use of another database, for example ACS-NSQIP, could have allowed this to be done, because as of 2012, a variable was included to indicate whether unplanned readmissions were related or unrelated to the index procedure; however, this database limits follow-up to 30-days post-discharge and thus could not be utilized for the long-term follow-up needed to perform the present study.

Second, the inability to review each patient’s chart prevented us from labeling a readmission as preventable or not, an important factor that has been studied in other smaller cohorts [4]. Despite stoma-related complications and dehydration being common reasons for readmission in our study, we could not judge whether these readmissions were indeed preventable. Finally, certain relevant covariates associated with post-operative complication risks (as demonstrated in the literature) such as race, ethnicity, frailty, and primary language spoken were not possible to assess using NRD [4, 13,14,15].

In summary, this study highlights that most complications after emergency colectomy likely occur outside of the POD30 window. Since there is no opportunity for pre-operative patient optimization due to the emergency nature of these colectomies, longer post-operative follow-up beyond 30 days is warranted. This will help to identify those at highest risk of readmission, and therefore, hopefully intervene before they require readmission or suffer secondary sequelae from the delay in addressing the complication. This will be beneficial for patient management, both medically and monetarily, thus helping reduce the burden on an already overstretched healthcare system.