The incidence of acute pericarditis is low, according to the literature about 1 per 850 inpatients with pericarditis, slightly more men than women. The common causes are mainly: bacterial and viral infections, connective tissue or collagen vascular diseases, metabolic diseases, tumors, post-pericardiotomy syndrome and idiopathic diseases. Its clinical features include fever, chest pain, shortness of breath, tachycardia, pericardial friction sounds and some abnormalities of the electrocardiogram. Cardiac ultrasound is the most effective method to diagnose pericardial effusion, while pericardial drainage is commonly used to diagnose and treat patients with pericardial effusion and to relieve the symptoms of concurrent pericardial tamponade. The majority of patients are currently treated with good outcomes and have a good prognosis. This study was conducted to clarify the etiology, clinical features, treatment and outcome of those children admitted with acute pericarditis. Data and Methods The clinical data of all 20 children with acute pericarditis admitted between 1987 and 1997 were confirmed, and the presence of pericardial effusion was detected on ultrasound. There were 11 males and 9 females with a mean age of 7.4 years (6 months to 13 years). The clinical presentation was fever, chest pain, shortness of breath, and physical examination revealed tachycardia, low heart sounds or pericardial fricative sounds, while blood pressure was normal and none of the patients had symptoms of pericardial tamponade. 17 cases were treated with pericardiocentesis, and blood and effusion samples were sent for microscopic examination and culture tests, and aspirates were also subjected to Gram staining and bacterial culture (except for Mycobacterium tuberculosis), as well as sugar, protein levels and cytology. Protein levels were determined and cytology counted. In addition, some samples from synovial joint cavities and osteomyelitis abscesses were examined accordingly. Of these, 8 cases were confirmed to be septic pericarditis and were treated with a combination of antimicrobials (usually anti-golden glucose drugs such as vancomycin + third-generation cephalosporins) for 4 weeks. 6 patients with connective tissue disease were treated with steroidal compounds, while 4 cases of viral pericarditis were treated with nonsteroidal anti-inflammatory drugs. 2 patients with mediastinal masses had pericardial effusion on physical examination and ultrasound, and CT scans showed The tumors were surgically removed in two cases, one of whom died and the other began chemotherapy after surgery. The ECG showed low voltage in 13 cases and ST-segment elevation in 5 cases, while the ECG was normal in 2 patients with early childhood rheumatoid disease. The etiology of pericarditis was summarized according to the incidence as follows: septic pericarditis in 8 cases (40%), connective tissue disease in 6 cases (30%), viral pericarditis in 4 cases (20%), and secondary mediastinal tumor in 2 cases (10%). Other sites of infection were also found in patients with purulent pericarditis: septic arthritis (n=5), osteomyelitis (n=2), pneumonia (n=1), septic chest (n=1) and pyelonephritis (n=1), with evidence of other sites of infection not found in only 2 cases; blood cultures isolated Staphylococcus aureus in 7 cases, of which 4 were also positive for pericardial fluid and 3 for synovial cavity fluid, and the other 1 for The other case was negative because antimicrobial agents had been used before admission. Of the 6 patients with connective tissue disease, 3 had early childhood rheumatoid disease, 2 had SLE, and 1 had rheumatic fever. Of the four patients with viral pericarditis, one was treated with a subxiphoid pericardiotomy to aspirate nonpurulent fluid due to deterioration, and all of them improved with nonsteroidal anti-inflammatory drugs. The other was a 9-month-old boy who died 6 hours after surgery due to a primitive lymphocytoma of the middle mediastinum involving the pericardium and brain. Overall, all but 2 of the 20 children recovered well and no patients with recurrent or constrictive pericarditis were identified at follow-up. Discussion Primary septic pericarditis is rare and often occurs secondary to infection from other sites, reaching the pericardium by hematogenous and direct spread. The common organs are the lungs, particularly Staphylococcus aureus pneumonia, Haemophilus influenzae pneumonia and Streptococcus pneumonia. In those patients with septic arthritis, osteomyelitis or cutaneous aureus infection, these foci of infection often become the primary cause of pericarditis. In several literature reports from all over the world, Staphylococcus aureus was shown to be the most common infecting organism, while tuberculous pericarditis was rarely reported. In this group, purulent exudate was the most common form of pericarditis and the infecting organism was mostly S. aureus, septic arthritis was the most common concomitant disease, while not a single case of tuberculosis infection was found in all cases. Connective tissue disease is another cause of pericardial involvement in children, and pericarditis is a common cardiac impairment in early childhood rheumatoid disease and SLE, and occasionally occurs in acute rheumatic fever as part of a generalized carditis. This type of pericarditis does not require surgical drainage and is often cured by medication alone. All six patients in our group recovered gradually with steroidal anti-inflammatory drugs. In children, viral pericarditis is less likely to occur, and the common viruses are group B coxsackievirus and echovirus type 8, which are clinically difficult to distinguish from idiopathic pericarditis, and the pathogens of the four patients with viral pericarditis in our group remain unclear to date. In contrast, tumorigenic pericardial effusion is the result of direct pericardial invasion and is commonly associated with Hodgkin’s tumor, lymphoma, leukemia, and the two cases in this group were patients with mid mediastinal tumors. Pericardial drainage is valuable in the diagnosis and treatment of patients with pericardial effusion complicated by pericardial tamponade, and appropriate surgical drainage combined with antimicrobial therapy is much more effective than antimicrobial therapy alone in septic pericarditis, as has been demonstrated in previous clinical management. Among the various effective pericardial drainage procedures, subxiphoid pericardial puncture and drainage provides a simple, safe, and quick procedure for most patients with pericardial effusion, and is particularly suitable and effective for drainage of dilute pus. Recently, the modification of the beginning of the drainage tube into a wide port has been effective in preventing the development of constrictive pericarditis. None of the patients in this group developed constrictive pericarditis. Although some patients with acute pericarditis can be treated with an anterior thoracic pericardiostomy, we recommend subxiphoid pericardiocentesis because it is a very safe and effective procedure for most patients and can be easily performed in pediatric surgery.