Introduction:
Sciatica is a common reason for a medical consultation throughout the population. Piriformis pyomyositis is a rare cause of these symptoms. Its probable etiology is transient bacteraemia co-existing temporarily with a muscle injury.

Aim:
The aim of the study is to present a method for treating a piriformis muscle abscess with transabdominal ultrasound-guided transrectal drainage.

Case study:
A 14-year old boy, previously healthy, was admitted with symptoms of sciatica that appeared after intense physical exertion. Laboratory tests revealed elevated inflammatory parameters and positive blood culture results indicating Staphylococcus aureus. Antibiotic therapy was implemented. MRI of the small pelvis revealed a forming abscess of the right piriformis muscle. On day 6 of the antibiotic therapy, in the absence of improvement, it was decided to perform transrectal drainage under ultrasound guidance. Clinical improvement was achieved, and the inflammatory parameters decreased.

Results and discussion:
Co-existence of sciatica symptoms and signs of an inflammatory condition should prompt the consideration of piriformis pyomyositis. The mainstay of treatment for piriformis pyomyositis is antibiotic therapy. The abscess formation reduces its effectiveness, which necessitates surgical intervention. The authors present the application of transrectal drainage under transabdominal ultrasound guidance as the shortest route of abscess evacuation.

Conclusions:
Transrectal drainage of piriformis pyomyositis is an effective and safe method. Concomitant use of ultrasound scans reduces the patient’s exposure to ionising radiation. However, the widespread use of this method requires more in-depth research and broadened experience.