This study shows the great variety of symptoms in this age group. The most frequent symptoms were abdominal pain reported by the parents, pain on abdominal palpation, and clinical criteria of sepsis on admission to the emergency room. In addition, perforated appendices were associated with a longer period since onset at the time the patient was seen, hospital stay, days on antibiotics, ileus, and admission to PICU.
Acute appendicitis is a major cause of morbidity in infants and children under 4 years of age because it is an infrequent condition with nonspecific symptoms, which is why its timely diagnosis is sometimes compromised . Early clinical suspicion by the medical team (pediatrics and pediatric surgery) represents the mainstay for priority management and thus prevents unnecessary requests for ultrasound and CT scans [15,16,17]. Regarding symptoms, abdominal pain continues to be the main symptom in these patients and is associated with other symptoms such as vomiting and fever . At preschool age, the symptoms of acute appendicitis are nonspecific, so the information provided by parents becomes one of the keys to a timely diagnosis . Among the symptoms noted by parents, in order of frequency, were diffuse abdominal pain in 94% of the cases, followed by symptoms such as vomiting, anorexia, diarrhea, fever, and irritability . Signs of peritoneal irritation in infants are difficult to determine. In this series, peritoneal irritation was present in 72% of uncomplicated appendicitis and in 90% of complicated appendicitis. Serial evaluations with abdominal palpation and percussion in the right lower quadrant are sufficient to determine peritoneal irritation [19,20,21,22]. The systemic inflammatory response syndrome (SIRS), associated with an infectious focal point, is suggestive of sepsis . Raines et al. established the presence of SIRS in patients with appendicitis and found it had a prevalence of 30% in children under 17 years of age, and that the presence of SIRS was associated with complicated appendicitis . Other studies have demonstrated the presence of SIRS in patients with higher rates of appendectomy . In our population, the presence of SIRS comes to more than 90% upon admission to the emergency room with high rates of perforation. Therefore, the clinician should look for the presence of SIRS and abdominal pain in young children in order to call in the pediatric surgeon at an early stage.
Diagnosing acute appendicitis is not easy in young pediatric patients. The use of laboratory studies and diagnostic images for these patients is intended to provide a more accurate diagnosis. The recommendation for applying them should be in accordance with the diagnostic impression, the patient’s physical examination, the PAS, and the physician’s judgment [18, 24]. The use of ultrasound for this condition worldwide has revealed that it has a relatively high sensitivity and specificity (90% and 95%, respectively) . However, even though it represents a reproducible and nonionizing diagnostic aid, especially for the age group in question, it is limited by the fact that it is an operator-dependent test, and its sensitivity and specificity are linked to the radiologist’s experience. The study by Mangona et al.  shows how ultrasound scans done in training centers and those done at night alter sensitivity and specificity. Without clinical suspicion, the request for an ultrasound scan could delay the diagnosis. For example, in this series, only 45% of the ultrasound scans were conclusive. In spite of the fact that CTs have demonstrated greater sensitivity and specificity than ultrasound , their use represents exposure to radiation that is sometimes unnecessary for pediatric patients. In addition to delaying timely management of this condition, it is noteworthy how limited the requests for CTs are in our population.
The performance of the hemogram in the present study was similar to that of other case series . This laboratory test is frequently requested for these patients. However, the increase in leukocytes is nonspecific and has little sensitivity since they may have increased in other infectious diseases and do not differentiate between complicated and uncomplicated appendicitis [18, 19]. Neutrophils together with the total leukocyte count improve the sensitivity (60–87%) and specificity (53–100%) for acute appendicitis. However, a low count cannot limit the diagnosis to appendicitis [19, 27]. C-reactive protein (CRP) is still a nonspecific laboratory test for this type of pathology with sensitivity (43 to 92%) and specificity (33–95%). Studies show that an elevated CRP together with the sensitivity of leukocytosis and neutrophilia could approach 98% for the diagnosis of appendicitis [9, 27].
Acute perforated appendicitis is directly related to the onset of symptoms, progression time, delay in diagnosis, and time to surgical management with the risk of complicated appendicitis . This reinforces the concept that poor clinical suspicion, the delay in having inconclusive laboratory tests done, and, therefore, a late diagnosis increase the incidence of complicated appendicitis and complications related to surgical findings [29, 30]. A delay of more than 24 h for patients with symptoms has shown a higher rate of complicated appendicitis not only in children but also in adults . This is relevant when a patient with abdominal pain is admitted to the emergency room because of its direct repercussion on the surgical and postoperative outcome. Perforations are very frequent in younger children and account for up to 80% of children under 3 years of age [5, 32]. There are several theories about this including aspects such as anatomical immaturity, lack of an adequate omental barrier to contain peritonitis, a mobile appendix, the presence of a thin appendiceal wall, and the difficulty of infants to express their symptoms [2, 5].
Regarding the surgical management of these patients, in spite of the large number of complicated appendicitis cases, a significant group of patients underwent laparoscopic surgery. This approach has been gaining ground over open surgery in this population group with a surgical complication rate similar to recent world literature [33,34,35,36,37,38]. It is noteworthy that in spite of being complicated acute appendicitis in 76% of the cases, the need for reoperation was not high, and the most frequent postoperative complication was organ-space type surgical site infection. The vast majority of these were managed with only broad-spectrum antibiotic therapy, mainly upgraded to piperacillin tazobactam [39,40,41]. No carbapenemics were used since they do not fit within the rational use of antibiotics on this population group. These complications continue to represent the greatest risk during the postoperative period due to the high intraperitoneal contamination, especially in complicated appendicitis . The use of minimally invasive methods such as percutaneous drainage could be reevaluated in these cases in subsequent studies.
Recently, the exclusive use of antibiotic therapy for the management of uncomplicated appendicitis has also been studied. This involves the routine use of specialized imaging such as CT for a proper intra-abdominal assessment of appendicitis that has a success rate of 58 to 100% of cases [43, 44]. In spite of these findings and considering the previously mentioned unusual behavior of appendicitis in infants, it is not possible to determine the applicability of this strategy in this population group. More studies and faster diagnosis are required to define the possibility of exclusive use of antibiotic therapy in patients under 5 years of age with uncomplicated appendicitis. Of the appendices evaluated in this study, 81% were perforated. This percentage is comparable to other published series [2, 5] and correlates with the microscopic findings in the present population. In 93% of the microscopic studies, there was acute appendicitis with peri-appendicitis since, in the majority of cases (advanced stages), there would be some degree of ulceration of the mucosa and acute inflammation and, in the most severe cases, transmural compromise with neutrophilic infiltration of the muscularis propria .
The retrospective data collection with respect to the exploration of associations is limited by the fact that no sample size calculation was done, so the measurements of association may be overestimated or underestimated.