A 45-year-old female accidentally fell at home and started to feel pain over the right posterior hip. The pain worsened with prolonged sitting, lying, and postural change. Ambulation had become more diffi - cult and thus she visited our outpatient clinic for evaluation. Upon physical examination, focal swelling over the buttock with tenderness and muscle guarding was found. There was a limited active range of hip extension because of aggravated pain. Sensation and deep tendon refl exes of the lower limbs were normal. Plain radiographs of bilateral hip joints were unremarkable. With the patient in the prone position, an ultrasound scan revealed an irregular, anechoic, compressible mass between the gluteus maximus and ischial tuberosity (Figure 1). Ultrasound-guided needle aspiration was performed and dark-reddish synovial fluid was withdrawn, compatible with hemorrhagic bursitis. The patient received analgesics and another aspiration two weeks later. Symptoms resolved completely thereafter.

Ischiogluteal bursitis, also known as Weaver’s bottom, refers to inflammation of the ischiogluteal bursa. The synovial bursa is situated superficial to the ischial tuberosity. While she was standing, it was shielded by the gluteus maximus muscle; but while she was sitting, the muscle slid upwards, leaving the bursa susceptible to external pressure and irritation [1]. This anatomical characteristic makes ischiogluteal bursitis more often seen in people with sedentary jobs. Repetitive movements such as cycling are a risk factor as well. Other causes of bursitis include trauma, arthritis, infection, autoimmune disease, and crystal deposition. Patients mostly complain of moderate, pinpoint pain over the gluteal and posterior upper thigh region intensified by sitting down or stretching the gluteus maximus. Sleep and mobility may be hampered because of pain and swelling. In addition to tenderness around the ischial tuberosity, similar to symptoms of sciatica, radiating pain may appear as the bursa is near the sciatic and posterior femoral cutaneous nerve [2]. It can also raise suspicion of neoplasms in chronic cases [3]. Because of its uncommon nature and unspecific presentation, accurate diagnosis can pose a serious clinical challenge. Physicians must be careful in differentiating bursitis with lumbosacral radiculopathy, muscle tear, arthritis, and degenerative joint disease. Ultrasound, magnetic resonance imaging, and computed tomography have been used to diagnose bursitis. Ultrasound has the advantage of being portable, cost-efficient, and radiation-free. Moreover, it can test compressibility by dynamic imaging. By visualizing a thin-walled, compressible, cystic lesion which might contain internal septa and mural nodules, ischiogluteal bursitis can be identified efficiently with ultrasound. The real-time examination also provides the opportunity to perform safe aspiration for both diagnosis and treatment. Intrabursal injection with corticosteroid or lidocaine can be beneficial in patients with unrelenting pain.

In summary, our case highlights the value of ultrasound examination for the diagnosis and guided intervention of ischiogluteal bursitis.

(A) Ultrasound imaging at the right lower buttock region disclosed anechoic fl uid collection (asterisk) containing hyper-echoic mural nodules (arrowhead). (B) Ischiogluteal bursitis (asterisk) is sandwiched between the gluteus maximus muscle and the ischial tuberosity.

The authors declare no conflicts of interest.

This work was funded by National Taiwan University Hospital, Bei-Hu Branch; Ministry of Science and Technology (MOST 106-2314-B-002-180-MY3 and 109-2314-B-002-114-MY3); and the Taiwan Society of Ultrasound in Medicine.