Working Diagnosis:
Muscle Strain

Treatment:
After examination and imaging, it was recommended that he continue with PT for muscle injury and return to the clinic if symptoms worsened.

Outcome:
Three days later the patient developed fever, chills, and worsening pain. He went to the ER and was hospitalized for suspected infection and started on broad-spectrum antibiotics. CT-guided aspiration of the sartorius was positive for MRSA. Infectious Disease was consulted and switched him to vancomycin IV. He continued to be febrile and required an I&D. Patient was discharged with a PICC line to finish IV vancomycin.

Follow up:
He followed up with Infectious Disease. He completed 14 days of Vancomycin followed by 14 days of Bactrim. His examination showed markedly improved pain without fluctuance. At the 1-month follow-up, the only residual was some mild induration.

Author's Comments:
Sartorius abscesses are very rare and there are minimal studies in the literature about this condition. One study reported the presence of a sartorius abscess after sigmoid colon perforation [1] which was not present in our case. The more common iliopsoas abscess has been reported in various pathologic processes, including inflammatory, hemorrhagic, and neoplastic conditions [2]. Primary psoas abscess is often caused by Staphylococcus aureus infection, with the incidence of methicillin-resistant S. aureus increasing in these patients [3].

Prior to being evaluated in the orthopedic urgent care, the patient had completed his MRI and ultrasound and was about to start PT. He did not initially present with the concerning symptoms of fever, chills, erythema, warmth, or purulent drainage about the thigh. His sartorius may have been strained while moving boxes. His history of eczema (and multiple courses of oral steroids) may have predisposed him to abscess formation. This risk factor, along with the MRI and ultrasound findings of a questionable hematoma within the sartorius could have heightened suspicion for abscess during the earlier stages of his evaluation.

This case illustrates that in patients with or without underlying disease or immunocompromised conditions, primary sartorius muscle abscess may develop. Any patient with groin pain and fever may require further workup including blood cultures and MRI studies for precise diagnosis and appropriate management.

Editor's Comments:
Sartorius abscesses are rare; iliopsoas abscess are far more common. In fact, most sartorius abscesses are an extension of iliopsoas abscesses.

This case highlights the need to maintain a broad differential diagnosis, particularly when patients have repeat visits for an evolving condition. Furthermore, this case also illustrates the role of patient education and the need to provide patients with thorough discharge instructions.

References:
1. Wadded A et al. A Rare Case Of Sigmoid Colon Perforation With Subsequent Psoas Abscess Collection With Extensive Involvement Of The Sartorius Muscle. BMJ Case Reports. 2017.

2. Iemura S et al. Treatment of thigh abscess caused by retroperitoneal perforation of cecal cancer: A case report. Annals Med Surg. 79. 2022

3. https://www.aliem.com/erem-pitfalls-and-perils-of-emergency-department-discharge-instructions/

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