Anatomy
Pyriform sinus (piriform sinus)
Also written as piriform sinus, pyriform sinuses, pyriform recess, piriform recess, pyriform fossa.
The pyriform sinuses are two small pear-shaped pockets low in the throat, one on each side of the opening to the voice box.
"Pyriform" means pear-shaped, which is what these two pockets look like. They sit lower in the throat than the vallecula, roughly at the level of the Adam's apple, with one on the left and one on the right of the entrance to the larynx (voice box). You may see the spelling "piriform" instead. Both spellings are used for the same structure.
They sit right at the level where the throat divides: the airway (larynx) in front, and the esophagus, or food pipe, behind. Everyone has them, and they are a normal part of throat anatomy.
In a report you may read "residue in the pyriform sinuses" or "piriform residue." That means some food or liquid settled into these side pockets rather than passing straight down.
Because the pyriform sinuses are one of the last places a swallow passes through, clinicians note whether anything is left there afterward and whether it clears with another swallow. This is a standard observation on swallow studies and does not by itself tell you anything about your own diagnosis.
This is a definition, not a reading of your report. What this term means in general and what it means for one specific person are different questions, and only the SLP who ran the study can answer the second one. Write the word down and ask at the follow-up.