A 5-year-old previously healthy boy presents to the emergency department (ED) with a 2-week history of intermittent left groin pain, usually occurring later in the day. Pain is not related to eating, movement, urination, or stooling. There is no report of trauma or precipitating event. He screams and refuses to stand up during pain episodes, which occur suddenly and last approximately 1 to 2 hours at a time. He otherwise has normal gait and activity when pain free. He does not wake up at night in pain. No recent illnesses or fevers are reported. Review of systems and his examination findings are unremarkable. Two days prior, he was evaluated in the ED for the same issue and had normal urinalysis, urine culture, and scrotal ultrasonogram results. The consulting urologist did not suspect a urologic process. He was discharged home with pain medication. Today, he returns to the ED because of the intense pain. The patient is admitted for further evaluation and pain management. Complete blood cell (CBC) count, C-reactive protein level, urinalysis results, and plain radiographs of the hips are unremarkable. Computed tomography of the abdomen and pelvis reveals a trace amount of nonspecific free fluid in the pelvis. His pain appears to be alleviated with ibuprofen and bed rest. The following day, he has another episode of intense groin pain after returning from the play room. Physical examination at this time demonstrates only point tenderness on palpation over his symphysis pubis area. No swelling, erythema, or increased warmth was noted in that area. An additional imaging study reveals the diagnosis. A 15-year-old girl presents to the clinic with an itchy rash, fever, headache, nausea, and dizziness. A few days earlier she was evaluated for rash on her back and low-grade fevers. She was prescribed amoxicillin clavulanate for suspected streptococcal …