Introduction

Acute appendicitis (AA) is one of the main surgical conditions nationally and worldwide¹, with an incidence in our country -Mexico- of 110 cases per 100 000 inhabitants². Appendectomy is still considered to be the gold standard for the management of AA, although conservative approaches have also been described. Despite being a common disorder, surgical management reports a rate of 10-20% of negative appendicitis (NA) or lymphoid hyperplasia (LHP) by histopathology³.

Different scales are used to diagnose AA, such as the AIR (Appendicitis Inflammatory Response) scale and the Alvarado score⁴. It has been reported that the Alvarado score can have a sensitivity of 97.2% and a specificity of 27.6%, while the AIR scale has a sensitivity of 81.9% and a specificity of 89.5%⁵. The sensitivity and specificity of imaging studies for the diagnosis of this disorder has also been studied⁶.

To support the diagnosis of AA, paraclinical tests are considered, specifically leukocytosis and neutrophilia (> 75%) on the Alvarado score⁷ and the Pediatric Appendicitis Score (PAS)⁸. The AIR scale includes cutoff points that generates a probability score of AA⁹.

Other parameters considered to identify their diagnostic value in AA are platelet count, mean platelet volume, and platelet distribution width (PDW)¹⁰.

The purpose of our study is to compare the clinical, laboratory, and radiological findings in patients with suspected AA.

Material and methods

A retrospective, observational, cross-sectional study was conducted, using data collected from the records that included the words “cecal appendix” within the histopathological reports of the Pathology Service from February 2013 to December 2017. Data included age, sex, histopathology diagnosis, stage of the condition, and progression time. Reports on lab tests and imaging studies were obtained from the medical records.

Total leukocyte count, absolute and relative neutrophils, and mean platelet volume and platelet count were obtained from lab tests. Data from abdominal ultrasound (US) and/or computed tomography scan (CT scan) were collected from the imaging studies, and direct and indirect signs of appendicitis were taken into account. US revealed location of the appendix, increased flow, presence of “ring of fire” sign, inability to compress the appendix, fat effacement, increased local perfusion, presence of free peritoneal fluid, and visualization of appendicolith. CT scan reported enlarged appendix, pericecal inflammation, effacement of fat planes, presence of appendicolith, free peritoneal air, abscess, free peritoneal fluid, and appendicular wall enhancement.

In our analysis, patients diagnosed with AA vs LHP, as well as uncomplicated vs complicated AA, were compared. In addition, participants were grouped into pediatric or adult patients.

A descriptive analysis was carried out using frequencies and percentages, and median and interquartile range (IQR), given the non-parametric distribution of these variables. Laboratory findings were compared using the Mann Whitney test. A P value < 0.05 was considered statistically significant. Data were analyzed with the IBM SPSS 25® statistical package (Armonk, NY; IBM Corp.).

Results

A total of 1676 appendectomies were performed on patients with suspected AA; 839 (50.1%) of them were female patients and 837 (49.9%) were male subjects. The age group with the most appendectomies performed was the 21-30-year-old group, 524 (31.2%) patients (Table 1). The median progression time was 48 hours (IQR 24-72). LHP was reported in 12% of the patients. Most LHP patients were from the 11-20-year-old group, showing progressive decrease with increasing age. According to the histopathology report, the median thickness of the appendicular wall was 2 mm (2-3 mm) and the median appendicular lumen was 3 mm (1-5 mm).

Of the 1475 (88%) patients with AA, 704 (47.7%) showed uncomplicated evolution, classified as congestive or suppurative AA in 398 (56.5%) and 306 (43.5%) patients, respectively; the remaining 771 (52.3%) showed complicated evolution, classified as abscessed or perforated AA in 470 (60.9%) and 301 (39.1%) patients, respectively.

Data were from 647 (38.6%) patients were collected from the imaging study reports. Radiography (87.7%) was the most used study, followed by US (53%) and CT scan (19.6%). Two subsequent studies were reported in 46.2% of patients, and three in 7.4%. Table 1 shows the frequency of ultrasound (n=341) and CT scan (n=73) findings.

For the analysis of laboratory findings, 774 patients were included: 393 (51%) men and 381 (49%) women. Of these patients, 200 (25.8%) were pediatric patients (< 18 years). By pathology, 63 (8.1%) corresponded to LHP, and 711 (91.9%) to AA, 312 (53.8%) of whom had uncomplicated AA (206 [66%] as congestive appendicitis and 106 [34%] as suppurative appendicitis), and the rest (399, 46.2%) had complicated AA (248 [79.4%] as abscessed appendicitis and 151 [21.6%] as perforated appendicitis).

In the group of pediatric patients, 16 (8%) corresponded to LHP, and 184 (92%) to AA, 82 (44.5%) of whom had uncomplicated AA (36 [43.9%] as congestive appendicitis and 46 [56.1%] as suppurative appendicitis), and 118 (55.5%) had complicated AA (69 [58.4%] as abscessed appendicitis and 49 [41.6%] as perforated appendicitis).

Comparison between laboratory findings in patients with AA and LHP (Table 2) showed higher levels of total leukocyte and neutrophil count (and percentage of neutrophils), as well as platelet count, in patients with AA (p < 0.05). When comparing the same data by age groups, the same parameters remained elevated in the group of adults with AA (compared to patients with LHP) (p < 0.05). However, no significant difference was found in pediatric patients (Table 3).

We found that leukocytosis greater than 11 x 103/μL is not significant to differentiate between LHP or AA (P = 0.102; OR, 1.64, 95% CI, 0.92-2.91). This finding (WBC > 11) shows 80.3% sensitivity, 28.5% specificity, PPV = 92.7%, and NPV = 11.3% to identify AA (vs LHP). Of the patients with laboratory results, 578 were AA with WBC > 11; 141 were AA with WBC < 11; 45 were no AA with WBC > 11; and 18 patients were no AA with WBC < 11.

Neutrophilia > 7 is significant (P = 0.017) in AA vs LHP, so the OR risk of AA for a subject with neutrophilia is 2.29 (95%, CI 1.23-4.27). This cutoff point (NEU > 7) shows 87.7% sensitivity, 24.1% specificity, PPV = 93%, and NPV = 14.7% to identify AA (vs LHP). Of the patients with laboratory results, 625 were AA with NEU > 7; 87 were AA with NEU < 7; 47 were no AA with NEU > 7; and 15 patients were no AA with NEU < 7.

Higher levels in the total leukocyte and neutrophil count (and percentage of neutrophils) were found in patients with complicated AA (p < 0.05) vs. uncomplicated AA; however, total platelet count remained similar (Table 4). When comparing adult vs. pediatric patients, findings in adults were the same as those in the general population, but no differences were found in pediatric patients (Table 5).

To differentiate complicated from uncomplicated AA, the analysis shows that total neutrophil count > 7 is significant (p <0.001), with risk OR 2.77 (95% CI 1.73-4.43). This criterion (NEU > 7) shows 92.4% sensitivity, 18.5% specificity, PPV = 59.3%, and NPV = 65.5% to identify complicated AA (vs uncomplicated AA). Of the patients with laboratory results, 366 were complicated AA with NEU > 7; 30 were complicated AA with NEU < 7; 251 were uncomplicated AA with NEU > 7; and 57 patients were uncomplicated AA with NEU < 7.

Discussion

According to the literature, AA is more common in male patients¹¹; however, AA affected both genders equally in our population. As for the age groups, this condition is more common in adolescents and young adults, since 72% of patients in our group were 11-40 years. Nonetheless, its range of presentation continues to be extremely wide (between 0 and 97 years in our population).

The percentage of surgeries reporting LHP or NA is 10-20% worldwide¹². Based on those standards, our hospital is within that range, since 14% is our highest NA prevalence when adjusted by age groups. However, in age groups with lower frequency of this condition, this number decreases to 4-5%, so efforts to reduce this rate should be focused on the 11-40 age groups, who show the highest frequency of presentation.

In our patients, the median progression time was 48 hours, showing that most (53%) of the patients with AA were delayed in seeking medical care, and were operated on when the appendicitis was worse. This is a challenge for medical care to achieve a timely surgery and prevent major surgical and infectious complications, including wound infections, abdominal abscesses, and bleeding^13,14.

Paraclinical studies showed the expected increase in total leukocyte count and total and percentage neutrophils, which are part of the scales that help diagnosing both adult¹⁵ and pediatric patients¹⁶. Mean platelet volume was associated with complicated appendicitis¹⁰; however, no association was found in our study.

In the studied population, typical laboratory values for AA diagnosis are relevant in AA vs LHP. However, this only occurs in adults, since no parameter is significant to differentiate AA from LHP or uncomplicated and complicated AA in pediatric patients.

When comparing uncomplicated and complicated AA, the three data of the white series showed significant increase, while PLT and MPV showed no difference (p < 0.05).

Other studies reported that MPV values in cases of uncomplicated AA were lower than in patients with complicated AA, and that MPV is a predictor of the development of complication¹⁷. In our study, MPV showed no significant change in AA vs LHP or uncomplicated vs complicated AA. Only platelet count showed a significant increase for AA vs LHP; however, further research on the platelets role in AA is needed, to assess its possible value as an indicator of AA and its usefulness associated with abscess formation in appendicular pathology.

Finally, although leukocytosis and percentage neutrophilia¹⁶ are also considered within the PAS scale for the diagnosis of AA in pediatric patients, none of those values reviewed in our study changed significantly, suggesting that those lab tests can be used as indicators of AA associated with LHP, or complicated AA associated with uncomplicated AA; therefore, AA behavior is different in pediatric patients.

As for imaging studies, indirect characteristics of appendicitis -such as effacement of fat planes and free peritoneal fluid- were the most commonly reported data in these patients.

In conclusion, AA occurs with the same frequency in both sexes in our setting. Progression time is an important factor in the frequent presentation of complicated AA, demanding fast and effective one-time medical attention.

There is also an association between leukocytosis, total and percentage neutrophilia, and higher platelet count in the presence of AA, compared to patients with lymphoid hyperplasia. The lab tests reviewed show no statistically significant changes in pediatric patients with AA. In adults with uncomplicated AA vs. complicated appendicitis, increased WBC, NEU and NEU% are statistically significant.