Ruptured Appendicitis masquerading as Knee Pain in pediatric patient: A Case Report

Dr Alan G. Shamrock at Department of Orthopaedics and Rehabilitation, The University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, and colleagues have reported a rare case of ruptured Appendicitis masquerading as Knee Pain in pediatric patient. The case has appeared in the Journal of Emergency Medicine.

Knee pain has a variety of etiologies in the pediatric population, including septic arthritis, osteomyelitis, fracture, ligamentous injury, and neoplasms. Extrinsic sources of knee pain may also be intra-abdominal, although abdominal pathology is much more likely to manifest as hip or proximal thigh musculature pain.

Abdominal pain is the most common reason for consultation in the emergency department, and most of the times, its cause is an episode of acute appendicitis. Acute appendicitis is an acute inflammation of the vermiform appendix, most likely due to obstruction of the lumen of the appendix (by fecalith, normal stool, infective agents, or lymphoid hyperplasia). However, the misdiagnosis rate of acute appendicitis is high due to the unusual presentation of the symptoms.Once the diagnosis of acute appendicitis is made, patients should be given nothing by mouth. Intravenous fluids, such as lactated Ringer solution, should be started.Appendectomy should be performed without delay, as early appendectomy reduces the chances of perforation and intra-abdominal abscess.

A 5-year-old healthy male presented with atraumatic right knee pain, discomfort with weight-bearing, fever, and elevated inflammatory laboratory markers. Physical examination and magnetic resonance imaging findings of the knee were benign, leading to low clinical suspicion for knee septic arthritis. Blood cultures were positive for a gastrointestinal organism, Granulicatella adiacens, suggesting abdominal pathology leading to referred pain. Ultrasound evaluation and computed tomography (CT) of the abdomen revealed a large abscess secondary to perforated appendicitis, which was treated with CT-guided drainage and i.v. antibiotics. The patient's musculoskeletal pain subsided with the treatment of appendicitis.

Acute appendicitis may present as knee pain, with other signs and symptoms mimicking septic arthritis, such as fever, inability to bear weight, and elevated inflammatory markers. Considering an array of differential diagnoses in pediatric patients with apparent knee septic arthritis is crucial to prevent delay in diagnosis of alternative infectious sources.