The appendix testis is a small remnant at the upper pole of the testis. When it twists, it causes pain, swelling and redness which can look as dramatic as testicular torsion. It is most common in boys of about 7 to 14 years, and it settles with rest and analgesia. Testicular torsion does not. The scan helps tell them apart, but only after the clinical picture has been weighed.
Scan images in the graphic are illustrations, not patient scans.
The scan
- Explain the scan, offer a chaperone and record the offer.
- Support the scrotum on a rolled towel. Use the linear probe with warm gel.
- Start on the painless side to set the grey-scale and colour settings.
- Look at each testis in two planes and compare the flow with the same colour settings.
- Scan the upper pole slowly, between the top of the testis and the head of the epididymis. This is where the point of tenderness usually is.
- Follow the spermatic cord up towards the groin in short axis.
Reading the view
- Torsion of the appendix testis: a small round nodule at the upper pole, with no flow inside it and often increased flow around it. The testis itself has normal echoes and normal flow.
- Reactive changes: a small hydrocele and a thickened scrotal wall are common. They can make the painful side look worse than the tiny appendage.
- Testicular torsion: reduced or absent flow in the testis compared with the other side, and a twisted cord, the whirlpool sign. See the testicular torsion pearl.
- Epididymo-orchitis: an enlarged epididymis with increased flow and a straight cord.
Action
Never delay urology review for a scan when testicular torsion is possible. If the clinical picture and the scan agree on a twisted appendix testis, it is usually managed with rest and analgesia, with safety-netting and a clear plan to return if the pain worsens. Follow your local paediatric and urology pathways.
