This study assessed postoperative outcomes, including length of admission, readmission rates and serious complications, in a cohort of patients with IBD undergoing resection surgery, stratifying patients based on the presence of sarcopenia and myosteatosis. The results add to existing evidence indicating that patients who suffer from IBD requiring resection surgery who also have perioperative sarcopenia, and in particular myosteatosis, require increased postoperative care. The importance of myosteatosis in relation to postoperative outcomes is gaining increasing recognition  and this study provides new evidence in this regard.
These findings may form the basis for further assessment of the timing of surgery in such patients, taking into consideration the influence of pre- and postoperative nutritional status. In fact, many of the surgeries in IBD patients are performed as emergencies and offer little potential to optimise nutritional status prior to surgery. Nevertheless, patients with myosteatosis, despite spending longer in hospital, were also more likely to require readmission.
It has been previously demonstrated that hospitalised patients with IBD have a greater protein-calorie deficiency compared with non-IBD patients . Investigation of methods for improving the nutritional and functional status of IBD patients prior to discharge following resection surgery, or also efforts on an outpatient basis, would help reduce readmission rates. Increased home visits or earlier review at outpatient clinics could work in this direction.
Patient selection is a potential confounding factor. However, the incidence of sarcopenia and postoperative complications in the present study were within expected limits. For example, the incidence of sarcopenia in patients with IBD has been reported to range from 26 to 60% [27,28,29]. The incidence of sarcopenia in the present cohort was 39% and, therefore, within this range.
On the other side, patients with ulcerative colitis were reported to have a lower incidence of sarcopenia when compared with those with those with Crohn disease , a difference which could potentially affect outcomes. However, patients with Crohn disease accounted for the greater proportion of patients in the present paper.
Almost 60% of patients in the present study underwent emergency surgery, which would have the potential to increase complication rates. The incidence of postoperative complications in the present paper was 21%, which was also within expected practice as complication rates of up to 27% have been reported in IBD patients . A recent study by Pederson et al.  reported a similar incidence of Clavien-Dindo type-3a complications (25%) and similar length of hospital admission (8 days) compared with the present study. Six patients (8%) required reoperation in the present study, which is again comparable with published data [4, 5, 31].
The present study demonstrated no significant difference in the incidence of type-3a or greater Clavien-Dindo complications between sarcopenia and non-sarcopenia patient groups. Other studies reported differed data in this regard. Zhang et al.  found a decreased incidence of complications in non-sarcopenia patients (2.3 compared with 15.7%). However, when comparing this data with our results, we should consider that the patients were ten years younger, the definition of sarcopenia was slightly different, and the prevalence of sarcopenia was more than double.
Patients with IBD are prone to preoperative sarcopenia and myosteatosis due to a combination of chronic illness, abdominal pain hindering oral intake, malabsorption and the effects of medications . In addition, disease activity and the pro-inflammatory state of IBD patients was perioperatively attested to in the present study by the increased incidence of clinically relevant complications with a NLR greater than five. This has been noted previously in the setting of colorectal carcinoma . The treatment of postoperative leaks is very challenging in IBD patients due to the frequent presence of a hostile abdominal status, resulting in a preference for non-surgical drainage by interventional radiology approaches .
The impact of sarcopenia and myosteatosis on postoperative outcome has been examined to a greater extent in patients with colorectal cancer; however, there is a substantial variability in study methodology and results. In some reports the presence of sarcopenia and myosteatosis failed to show an association with the occurrence of intra-abdominal leaks or abscesses in patients undergoing colorectal cancer surgical resection, which concurs with the results of the present study [11, 20]. On the other hand, Huang et al.  found an association between sarcopenia and postoperative complications: 10 of 17 patients with sarcopenia had a grade 2 or greater CCI complication following surgery for colorectal cancer. This cohort therefore included patients with less complex complications in comparison with the present study.
The aetiology of sarcopenia and myosteatosis in cancer, which contribute to the cancer cachexia state, may differ from that of a benign condition, such as IBD, in which the processes causing the altered inflammatory state are more likely to be reversible either medically by immunosuppression or by surgical means. In the setting of cancer, it is generally believed that treating the disease will reduce the pro-inflammatory drive, but this goal is often not achievable . Recent papers have reported that recovery of skeletal muscle volume tends to follow after induction of infliximab in Crohn disease patients  or after colectomy in ulcerative colitis patients . In the present study, there was no significant difference in the complication rates between patients with ulcerative colitis and those with Crohn disease.
The classification of patients as affected with sarcopenia has been re-examined in recent years. An initial study by Prado et al.  provided cutoff values calculated in a population of obese patients, which may have caused skewing of results when applied to the general population. A follow-up study by Martin et al.  provided updated cutoff values with more heterogeneity in the cohort. In the present study, no association was demonstrated between sarcopenia or myosteatosis and postoperative complications when both the cutoff values published by Martin et al. or the lowest gender-specific cutoff were used.
The advent of low-dose CT has assisted in the assessment of acutely unwell patients with IBD who are at increased risk of high cumulative radiation exposure from diagnostic imaging . This is the first paper to examine the roles of both sarcopenia and myosteatosis, as measured by CT, in patients with IBD with respect to postoperative outcomes. The aetiology of the findings is less clear due to its retrospective design. The inclusion of a preoperative quality of life questionnaire and a short nutritional assessment questionnaire should be considered in a prospective study. Other methods of investigating the role of nutritional assessment of patients with IBD have also been described in the literature. The volumetric assessment of visceral fat has been shown to be associated with postoperative complications and this could be correlated with CT-derived data . The addition of preoperative measurements of muscle function, such as grip strength, could also be considered as direct comparisons with studies of postoperative outcomes in older patients with colorectal cancer are likely to be limited [9, 35].
In conclusion, the present study demonstrated an association between myosteatosis and increased hospital stay in addition to an increased 30-day readmission rate for patients with IBD undergoing resection. Given the treatable nature of IBD, there is a potential for sarcopenia and myosteatosis to be assessed in terms of potentially modifiable risk factors for adverse postoperative outcomes and, therefore, for being the target of future therapeutic targets.