Our study presents the first analysis of the predictive value of CT-assessed sarcopenia for complicated appendicitis in the literature. Accordingly, CT-assessed sarcopenia index SMI, muscle volume and BMI can predict complicated appendicitis in geriatric patients.
Geriatric age is amongst the factors associated with complicated appendicitis . Co-morbidities such as anaemia, cardiac disease and chronic renal disease in geriatric patients are also associated with complicated appendicitis .
Higher rates of complicated appendicitis in geriatric patients are attributed to risk factors such as vascular sclerosis, fibrotic narrowing of the lumen and fat infiltration on the muscular layer of the appendix, so complications such as perforation tend to occur more easily . There might also be a diagnostic delay related to an inability to sense pain and laboratory abnormalities of co-morbidities in advanced age [13, 14]. Fifty-two percent of the patients included in this study were in the complicated appendicitis category. The patient population in our study was of geriatric age, so the complicated appendicitis ratio was higher than that seen in the general population.
The term ‘sarcopenia’ has been previously used to describe the loss of muscle with increased age; however, according to new definitions, physical performance and muscle strength are equally important as a decrease in muscle volume. Its pathogenesis is multifactorial and includes chronic metabolic changes, low BMI and reduced activity and protein intake. The factors usually combine, resulting in dysfunction of muscle mass function and strength.
Different research groups’ evolving terminology and definitions of sarcopenia have seen different criteria proposed, including numeric cut-off values that may differ across countries and ethnic groups . Consequently, it may be better interpreted as a syndrome that may be presented in different degrees in different patient cohorts . As the degree of muscle volume decreases, adverse events seem to be more highly related to decreased muscle strength or function .
There are several validated methods to measure sarcopenia, such as dual X-ray absorptiometry, bioelectric impedance analysis, MRI and CT scanning. Of these techniques, CT is considered the gold standard method to diagnose sarcopenia with a range of minimal errors (1% to 4%) [18,19]. Although it is more expensive than anthropometric methods and poses a greater radiation exposure than the other techniques, it provides high accuracy and reproducible results. It also enables the evaluation of lean body mass and visceral and subcutaneous fat tissues at the same time .
In our retrospective study, we chose SMI as a CT-assessed sarcopenia index. In this technique, the psoas muscle at L3 vertebra level on cross-section imaging was analysed as a representative of the total body muscle mass which gave information about muscle quantity and quality. The distinction among different tissues such as muscle and fat was assessed by Hounsfield units .
In general, CT has been widely used in geriatric patients presenting with emergency abdominal pain, especially in differential diagnosis. CT results in the elderly might be highly influential on the direction of the therapeutic process . Thus, analysing the sarcopenia at the same time during an index CT might have several benefits, such as predicting complicated appendicitis. In our study, we used the preoperative contrast-enhanced abdominal CT to differentiate appendicitis status and analyse the sarcopenia as SMI.
Recently, sarcopenia has been analysed on the surgical outcomes of patients who have undergone elective cancer surgery or emergency abdominal surgery. In general, CT-assessed sarcopenia has been shown to be a risk factor in the short- and long-term outcomes of gastrointestinal oncology patients. In geriatric patients with colorectal cancer, sarcopenia has been not only associated with postoperative complications and long-term outcomes but can also predict preoperative nutritional risks. Therefore, it can guide treatment and follow-up strategies. Studies have shown that among patients undergoing exploratory laparotomy, sarcopenia has been associated with higher morbidity, mortality and length of stay as well as undesirable discharge rates . It is also associated with higher mortality rates during the one-year postoperative follow-up period in geriatric patients who underwent emergency abdominal surgery .
Our study result is compatible with the literature and shows the significance of sarcopenia in predicting complicated appendicitis.
In our patient cohort, the mean BMI of geriatric patients with complicated appendicitis was 25,28 kg/m2, while with uncomplicated cases it was 27,29 kg/m2. Although there is statistical significance between the mean BMI levels of the two groups, it might not be interpreted as clinical significance. A BMI level between 25 kg/m2 and 29.9 kg/m2 is accepted as overweight, according to National Institute of Health (NIH) and World Health Organisation (WHO) classifications. BMI is a statistical index for estimating body fat in both genders and is commonly used. However, due to individual and geographical variations, it is still insufficient to classify a person as obese or malnourished . Furthermore, it does not differentiate between body lean mass and body fat mass. It is an easily obtainable metric, but it does not correlate solely with a patient’s morbidity and mortality, considering many variables including genetic and environmental confounders . In the literature, BMI as an indicator of nutritional status is associated with different surgical outcomes in different patient cohorts. Geriatric obese patients who have undergone emergency surgery have higher morbidity and lower mortality rates than their normal-BMI counterparts . In another study, patients who underwent emergency diverting esophagectomy and who had lower BMI tended to have more anastomotic leaks after reconstruction . Another study showed that higher BMI was an independent risk factor for early anastomotic leakage after colorectal surgery . While geriatric obesity is a growing concern worldwide, Turkey has one of the highest obesity risks in Europe, and sarcopenic obesity was seen in 11% of one geriatric patient cohort; however, in our geriatric patients, the mean BMI of the two groups does not support any association between sarcopenia and obesity .
Additionally, our study results show that the mean muscle area assessed by CT between groups was statistically significant. The mean value for the uncomplicated appendicitis group was 125.52 cm2, while for the complicated appendicitis group, it was 116.87 cm2. This significance might be co-related to the significant difference between groups of the sarcopenia index.
Furthermore, there is a statistically significant difference with a 0.10 margin of error between uncomplicated and complicated cases in terms of subcutaneous fatty tissue area values. This significance is correlated with the significant difference of the mean BMI values of geriatric patients with different appendicitis statuses.
In our study, our patient cohort did not differ significantly regarding gender for the prediction of complicated appendicitis, so we did not use previously used cut-off values for the CT-assessed sarcopenia index. The cut-off value of sarcopenia which was assessed by ROC analysis was 41.62 cm2/m2, which has shown 71% sensitivity and 52% specificity.
Moreover, the cut-off value of muscle area assessed by ROC analysis was 115.66 cm2, which has shown 72% sensitivity and 54% specificity.
Finally, when a ROC analysis was performed with the data yielded by BMI results, the cut-off point for BMI was determined as 24.97 kg/m2, with 69% sensitivity and 52% selectivity. The AUC value was also calculated as 0.62 (p=0.010). The three cut-off values have similar sensitivity and specificity.
There are several scoring systems for diagnosing acute appendicitis. One of the most used methods, the Alvarado score, has high sensitivity and specificity values, especially to exclude acute appendicitis when the score is less than 5. However, few studies have analysed the scoring systems in geriatric patients. Hence, there is no specific scoring system to discriminate complicated from uncomplicated appendicitis in such patients. So, in that case; among elderly patients, it is not recommended to diagnose or exclude acute appendicitis solely on the basis of the diagnostic scoring system [1,2]. Recently, a CT-based acute appendicitis severity index has been found a reliable parameter predicting complicated appendicitis . Furthermore, using imaging analysis together with the clinical scoring systems may enable better differentiation of cases of complicated and uncomplicated appendicitis .
According to our study results, CT-assessed sarcopenia might predict complicated appendicitis in geriatric patients with a moderate degree of sensitivity and specificity and be used separately or in combination with diagnostic scoring systems. Nevertheless, prospective studies with large patient cohorts could better evaluate the predictive value of sarcopenia.