Hip Pain in a Child: Myositis or Appendicitis

1. Hip Pain in a Child: Myositis or Appendicitis Andaleeb Raja MD Muhammad Waseem MD Husayn Al-Husayni MD Lincoln Medical & Mental Health Center Bronx, New York

2. Case Presentation • 11 year old boy presenting with fever & hip pain for 2 days • Denied abdominal pain, vomiting or change in bowel habits • Denied knee pain or history of trauma/falls • Denied recent travel or sick contacts • Denied family history of joint disease • Discharged home after Hip X rays were negative and initial labs were reviewed

3. Pelvis X-Ray

4. Labs • WBC 11,200/mm with 74% Neutrophils • ESR 5 mm/hr • CRP 15.51 mg/L (0.25-3.0) • Blood Culture: Gram (+) cocci in clusters

5. Case Presentation • Recalled to the ER the next day • Blood cultures - Gram (+) cocci in clusters • Still c/o fever, but now walking with a limp • Described right hip and groin pain • Pain was constant in nature, “sharp & achy” • Pain was exacerbated when he walked • He was unable to walk without being supported

6. Physical Exam • Vitals: T100.5 HR 120 RR 20 BP 125/85 • General: ill appearing, but alert, awake • HEENT: dry mucous membranes • Chest: clear to auscultation, B/L breath sounds • CVS: tachycardic • Abd: mild RLQ tenderness initially, but not reproducible. No masses, no guarding • GU: (+) cremasteric reflex, no hernia, no scrotal swelling • Ext: • (+) tenderness over pelvic area and anterior thigh • No deformity, bruising or swelling noted over hip. • Equal thigh measurements. Unable to elicit hop test (patient refused to walk) • ROM hip intact • Palpable small inguinal lymph nodes bilaterally

7. Labs • WBC 13,900/mm with 85% neutrophils • Hemoglobin 14.1 g/dl • Platelets 204/mm • CRP 116.56 mg/L • CK 91 U/L (40-210) • UA specific gravity >1.045, 0-2/hpf WBC & RBC • Electrolytes: WNL

8. Radiology • Plain film Pelvis with Right hip – normal on previous visit • Non-contrast CT scan hip/Lower abdomen • Inflamed tip of the appendix with mild peri-appendiceal fluid

9. CT Scan Hip

10. CT Scan Hip

11. Learning Objectives • Understanding the atypical presentation of acute appendicitis in children • Recognize pyomyositis as a rare but important etiology to be considered in patient with hip pain and fever • Review of the differential diagnoses of hip pain in children

12. Case Discussion • Appendicitis is a difficult diagnosis in children as it may have an atypical presentation • Classic symptoms are often not seen • Can lead to misdiagnosis • High morbidity/mortality • Pathophysiology in children may be different due to the change in anatomic location • Inability to walk/walking with limp reported to be a significant finding • 1/4 of patients may present with a limp or right hip stiffness

13. Case Discussion • Pyomyositis - Rare • Hip pain, limp, fever • Uncommon infectious process involving skeletal muscle • Caused by pus producing bacteria (staph aureus most frequently involved) • This patient had (+) staph aureas in Blood cultures • CK may remain normal, while ESR and CRP are usually elevated • Child had normal CK but elevated CRP, leukocytosis • CT can be used to identify and localize the abscess • No abscess was seen on CT • Large muscle groups (thigh) are likely targets • Correct diagnosis is based on high index of suspicion • Important to recognize to reduce morbidity/mortality associated with the condition

14. Differential Diagnosis • Transient Synovitis • Most common cause of hip pain in children • Consider in absence of trauma history • Self limiting • Usually more frequent in boys • Important to distinguish between this and septic arthritis, which requires drainage and antibiotics

15. Differential Diagnosis • Slipped Capital Femoral Epiphysis • Present with limp or vague thigh/hip pain • Typically involves obese children • Legg-Calve-Perthes Disease • Avascular necrosis of femoral head • Pain localized to hip, limping • Plain films may show epiphyseal fragmentation • MRI more sensitive

16. Differential Diagnosis • Psoas Muscle Abscess • Relatively rare in children • Vague symptoms because of the posterior location of the psoas mucle • Classic symptoms: limp with fever and abdominal pain • Blood cultures often positive • Physical Exam: psoas cannot be examined easily (deep structure) • Psoas sign: pain when the hip is passively extended or actively flexed against resistance • Attributed to inflammation causing spasm of psoas muscle

17. Differential Diagnosis • Pelvic Osteomyelitis • Rare but should be considered in a child who presents with hip pain • MRI should be obtained in presence of suspicion

18. References • Frick SL. Evaluation of the child who has hip pain. Orthop Clin North Am. 2006 Apr;37(2):133-40 • Yang WJ, Im SA, Lim GY, Chun HJ, Jung NY, Sung MS, Choi BG. MR imaging of transient synovitis: differentiation from septic arthritis. Pediatr Radiol. 2006 Nov;36(11):1154-1158 • Katz DA. Slipped capital femoral epiphysis: the importance of early diagnosis. Pediatr Ann. 2006 Feb;35(2):102-111 • Weber-Chrysochoou C, Corti N, Goetschel P, Altermatt S, Huisman TA, Berger C. Pelvic osteomyelitis: a diagnostic challenge in children. J Pediatr Surg. 2007 Mar;42(3):553-557

19. References • Becker T, Kharbanda A, Bachur R. Atypical clinical features of pediatric appendicitis. Acad Emerg Med. 2007 Feb;14(2):124-129 • Reynolds SL. Missed appendicitis in a pediatric emergency department. Pediatr Emerg Care. 1993 Feb;9(1):1-3 • Bundy DG, Byerley JS, Liles EA, Perrin EM, Katznelson J, Rice HE. Does this child have appendicitis? JAMA. 2007 Jul 25;298(4):438-451 • Colvin JM, Bachur R, Kharbanda A. The presentation of appendicitis in preadolescent children. Pediatr Emerg Care. 2007 Dec;23(12):849-855 • Sakellaris G, Tilemis S, Charissis G. Acute appendicitis in preschool-age children. Eur J Pediatr. 2005 Feb;164(2):80-83

20. References • Kumar A, Anderson D. Primary obturator externus pyomyositis in a child presenting as hip pain: a case report. Pediatr Emerg Care. 2008;24:97-98 • Iyer S, Lobo M, Capell W. Obturator internus pyomyositis: a differential diagnosis for septic arthritis of the hip. J Paediatr Child Health. 2005;41:534-535 • Fowler T, Strote J. Isolated obturator externus muscle abscess presenting as hip pain. J Emerg Med. 2006 ;30:137-139

21. Question • A 12 year old male presented to the ED with a 2 day history of fever and right hip pain. He was noted to be limping on arrival. He denied any history of trauma. Abdominal physical examination findings revealed no guarding, but there was minimal tenderness in the right lower quadrant. Laboratory evaluation revealed a WBC 15.2. Hip radiographs were normal. What is the next best step in his management? • Admit for observation • Joint aspiration • CT scan abdomen and pelvis • Pelvic ultrasound • Administer a dose of IV antibiotics, then discharge home with 24-hour follow up

22. Answer - C • Because of the varied location of the appendix, the presentation of pain in a patient with acute appendicitis can be diverse. A patient with a low lying appendix can present with hip pain without significant abdominal findings. • It is important to include appendicitis in the differential diagnosis of hip pain. If the diagnosis is delayed, appendicitis is associated with significant morbidity and mortality. A computed tomography of the abdomen and pelvis is the imaging modality of choice.