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The Journal of Emergency Medicine, Vol. 30, No. 2, pp. 137–139, 2006Copyright © 2006 Elsevier Inc.

Printed in the USA. All rights reserved0736-4679/06 $–see front matter

doi:10.1016/j.jemermed.2005.04.016

ClinicalCommunications

ISOLATED OBTURATOR EXTERNUS MUSCLE ABSCESS PRESENTINGAS HIP PAIN

Todd Fowler, MD, and Jared Strote, MD, MS

Division of Emergency Medicine, University of Washington Medical Center, Seattle, Washington

Reprint Address: Jared Strote, MD, Box 356123 UWMC, 1959 NE Pacific Street, Seattle, WA 98195

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Abstract—The case of a 20-year-old diabetic male with 2eeks of hip pain, diagnosed with an isolated obturator

xternus muscle abscess, is reported. Pyomyositis, or ab-cess formation deep within a large striated muscle, is aare but potentially life-threatening disease. © 2006lsevier Inc.

Keywords—infectious disease; pyomyositis; muscle ab-cess; hip pain

INTRODUCTION

ip pain is a common chief complaint by patients pre-enting to the Emergency Department. The differentialiagnosis is broad and includes etiologies associatedith significant morbidity and mortality such as septic

rthritis, avascular necrosis, and osteomyelitis. Pelvicuscle abscesses are an extremely uncommon entity that

an pose a diagnostic challenge resulting in diagnosticelay. The case of an isolated spontaneous obturatorxternus muscle abscess is reported.

CASE REPORT

20-year-old male with type 1 diabetes presented to ourrban, academic Emergency Department complaining ofeft hip pain, progressive over 2 weeks. The pain had

Clinical Communications (Adults) is coordinatedUniversity Medical School, Boston, Massachusetts

ECEIVED: 14 January 2004; FINAL SUBMISSION RECEIVED:

CCEPTED: 1 April 2005

137

ncreased to the point that he had been unable to ambu-ate for the prior 5 days and had pain with movement ofhe lower extremity in any direction. He described theain as constant, “sharp and achy,” and worse when heat up or tried to walk. His thigh felt “swollen and tight.”e had been seen at an outside facility, diagnosed with a

train, and prescribed narcotics, which had not decreasedhe pain significantly.

The patient denied any trauma or prior history of hipain. His blood glucose had been slightly elevated forim, “in the 300s.” His lower back and contralateral kneeere mildly painful as well, which he attributed to fa-oring the affected extremity over the last week. Heenied fever, chills, nausea, vomiting, abdominal pain,enital or urinary symptoms, change in bowel function-ng or habit, weakness, and numbness.

The patient’s past medical history consisted of typediabetes with poor glucose control and a history of

etoacidosis. Medications included insulin, hydroc-done/acetaminophen, and ibuprofen. Family historyas positive for diabetes only. He denied any drugse.

On physical examination, the patient had vital signsithin normal limits, with a blood pressure of 142/78

orr, a pulse of 90 beats/min, and a temperature of 35.8°Ceasured orally. He appeared comfortable. Head, eye,

ar, nose and throat, neck, pulmonary, and cardiovascu-ar examinations were within normal limits. The abdo-

n Walls, MD, of Brigham and Women’s Hospital and Harvard

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138 T. Fowler and J. Strote

en was soft and non-tender, with normal bowel soundsnd no masses. The pelvis was stable and non-tender.enitourinary examination was normal without tender-ess, mass, or hernia. There was focal tenderness alonghe left inguinal ligament but no mass or lymphadenop-thy. His back was non-tender. Extremity examinationevealed decreased range of motion of the left hip sec-ndary to pain with flexion to 90 degrees, extension to 10egrees, abduction to 30 degrees, internal rotation andxternal rotation to 10 degrees. There was no deformity,ruise, warmth, rash, lesion, fluctuance, or point tender-ess. All other joints had full range of motion and wereon-tender. Thigh measurements were equal. Neurologicxamination showed slight decreased strength of the leftip in all directions secondary to pain. Otherwise, motorunction was full. Sensation was normal. All reflexesere full and equal. Rectal examination showed normal

one and sensation, no tenderness, and guaiac negativetool.

An intravenous (i.v.) line was placed and the patienteceived morphine and promethazine with good pain con-rol. Finger stick glucose was 337, and i.v. hydration wastarted. Complete blood count was normal with a whitelood count of 7500 and hematocrit of 41%. Erythrocyteedimentation rate (ESR) and C-reactive protein (CRP)ere elevated at 49 and 31, respectively. Urinalysis wasositive for glucose and trace ketones. Left hip and pelvisadiographs were normal. A magnetic resonance imagingtudy (MRI) of the pelvis and hip, obtained to rule outvascular necrosis or osteomyelitis, revealed a 3.0 � 3.0 �.2 cm abscess in the left obturator externus muscle (Figure). There was no evidence of adjoining inflammation or any

igure 1. T1-weighted MRI showing abscess in left obturato

ource for the abscess. t

The patient was admitted to the orthopedic surgeryervice and underwent percutaneous computed tomogra-hy (CT)-guided drainage of 6 cc of purulent fluid. Heas started on i.v. cefazolin. Cultures of the fluid grewtaphylococcus aureus, resistant only to penicillin. An-ibiotics were changed to oral cephalexin. White bloodount remained normal and blood cultures were negativehroughout his hospital course. ESR and CRP levelseaked at 82 and 35, respectively. He became asymp-omatic and was able to ambulate without difficulty,rompting discharge on hospital day 5. The patient con-inued oral cephalexin until it was stopped 6 days afterischarge due to diarrhea, for a total 10-day course. Heemains asymptomatic 8 months after discharge.

DISCUSSION

ip pain is a common complaint with many possibletiologies. During evaluation, it is critical to rule outore serious conditions such as acute fracture, septic

rthritis, avascular necrosis, osteomyelitis, and slippedapital femoral epiphysis before considering lessmergent entities such as muscle strain, bursitis, andsteoarthritis.

Pyomyositis, or intramuscular abscess, is a rare butotentially life-threatening cause of hip pain. Both pri-ary (spontaneous) and secondary (adjacent or distal

rimary infection site) forms have been described. Thetiology of primary pyomyositis is poorly understood.ocal mechanical trauma coincident with transient bac-

eremia is thought to be a mechanism causing seeding ofhe muscle and subsequent infection (1–3). For reasons

rnus muscle.

hat remain unclear, this entity is uncommon in temper-

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Obturator Pyomyositis 139

te climates. In tropical climates, pyomyositis incidences as high as 1/1000 and can account for up to 4% ofurgical hospital admissions (4). Temperate incidence isnknown but significantly less and usually associatedith co-morbidity: a significant percentage of these pa-

ients have underlying conditions such as diabetes mel-itus, HIV, alcoholic liver disease, intravenous drug use,mmunosuppression, or a hematologic disorder (2).here are some reports that temperate pyomyositis is on

he rise, although that may be due to increased recogni-ion from improved imaging techniques (3).

Staphylococcus aureus is the most common pathogen,ccounting for 50–95% of cases (2,5). Other causesnclude Streptococcus species, and in immunocompro-ised patients, Gram-negative organisms, anaerobes,

ungi, and tuberculosis (2). Pyomyositis can occur in anyuscle but is most frequently found in the pelvic mus-

les (2,6). We have found obturator externus muscleOEM) abscess reported only six times in the literaturend always associated with an abscess of the adjoiningbturator internus muscle (OIM). There are no knowneports of primary or isolated OEM abscess. The OEMriginates from the ischial ramus and inserts on theedial aspect of the greater trochanter of the femur,

ausing external rotation of the hip joint.Diagnosing pyomyositis can be a challenge due to its

arity, indolent presentation, and clinical findings that areimilar to other processes such as deep venous thrombo-is, septic arthritis, avascular necrosis, or malignancy3,7). The natural history of pyomyositis involves threetages. The first stage presents variably with fever, localwelling, induration, mild pain, minimal tenderness, andrythema. Onset is subacute, and aspiration of the muscleields no pus. The second stage occurs 10–21 days laterhen an abscess has developed in the muscle and theatient usually presents with fever, tenderness, andwelling in the affected area. Skin erythema is commonlybsent. The late stage consists of systemic illness withxquisite tenderness, fluctuance, high fever, and ulti-ately, septic shock (1,8). Pelvic muscle abscesses clas-

ically present with flank, hip or abdominal pain, fever,nd a limp (2,3).

Laboratory tests are generally nonspecific. Erythro-yte sedimentation rate is frequently elevated (3). Whitelood count is elevated in only 50–60% of cases. Serumreatine kinase is frequently normal (1). Blood culturesre positive in only 5–36% of the cases at the time oflinical manifestation (2,5).

Imaging studies are the primary means of diagnosingyomyositis. Plain films have little value, except to ruleut fracture. Ultrasound (US), computed tomographyCT), or magnetic resonance imaging (MRI) is usuallyecessary to identify the abscess. With US, abscesses

sually appear as complex, cystic structures containing

nternal echogenicity. CT can demonstrate focal musclewelling and well-delineated areas of fluid attenuation9). MRI is more sensitive than US and CT for detectingarly inflammatory changes and can demonstrate foci ofyomyositis that are occult to CT (7,9). MRI can alsoetter delineate the extent of adjacent soft tissue changesnd is the best study for detecting intraosseous vascularisorders and osteomyelitis, which are both commonlyncluded in the differential diagnosis (7,9,10). In thebsence of emergent MRI availability, both CT and USre recommended alternatives when pyomyositis is sus-ected; no comparisons looking at relative sensitivitiesnd specificities have been done (10).

Treatment of pyomyositis usually involves both intra-enous antibiotics and drainage (11). Due to the ana-omic location of the pelvic muscles, surgical drainage inhese cases may be difficult, thus requiring percutaneousnterventional radiologic techniques. Some reports havehown resolution of infection with antibiotic therapylone (9,10). Antibiotic choice is variable but must in-lude coverage for Staphylococcus aureus; Gram-egative coverage should be initiated in immunocompro-ised patients (1,2). Length of antibiotic therapy also

aries but is usually continued at least 3 to 4 weeks (2).We report here an isolated obturator externus muscle

bscess. The case presents typically for pyomyositis, withelayed presentation and non-specific findings on history,hysical examination, and initial studies. It illustrates theifficulty of diagnosis and adds a further reason to considerarly three-dimensional imaging techniques for unex-lained hip pain, especially in high-risk populations.

REFERENCES

1. Gubbay AJ, Isaacs D. Pyomyositis in children. Pediatr Infect Dis J2000;19:1009–12.

2. Crum NF. Bacterial pyositis in the United States. Am J Med2004;117:420–8.

3. King R, Laugharne D, Kerslake R, Holdsworth B. Primary obtu-rator pyomyositis: a diagnostic challenge. J Bone Joint Surg 2003;85B:895–8.

4. Shepherd JJ. Tropical myositis: is it an entity and what is its cause?Lancet 1983;2:1240–2.

5. Mandell G, Bennett J, Dollin R. Principles and practices of infec-tious diseases, 5th edn. London: Churchill Livingstone, Inc.; 2000.

6. Bickels J, Ben-Sira I, Kessler A, Wientraub S. Primary pyomyo-sitis. J Bone Joint Surg Am 2002;84:A2277–86.

7. Struk DW. Imaging of soft tissue infections. Radiol Clin North Am2001;39:277–303.

8. Chiedozi I. Pyomyositis: review of 205 cases in 112 patients. Am JSurg 1979;137: 255–9.

9. Orlicek SL, Abramson JS, Woods CR, Givner LB. Obturatorinternus muscle abscess in children. J Pediatr Orthop 2001;21:744–8.

0. Yu CW, Hsiao JK, Hsu CY, Shih TT. Bacterial pyomyositis: MRIand clinical correlation. Magn Resin Imaging 2004;22:1233–41.

1. Song J, Letts M, Monson R. Differentiation of psoas muscle

abscess from septic arthritis of the hip in children. Clin OrthopRelat Res 2001;(391):258–65.