Comments: Most of the forms are quoted from Лексика 1971; they seem, however, well recorded (except Tind. raχir which is obviously a misspelling instead of *raχ:ir). The Av. parallel to PA *r-iχ:V-r 'diarrhea' is Av. ríχ:e-l id., which was borrowed in Tsezian languages (Tsez. reχel, Gin. reχel / riχel, Gunz. riχil).
There exists also a PA form *ʔinχ:u (Tind. unχ:i 'faeces', Akhv. ĩχ:u 'diarrhea') which indicates that the root once had a medial resonant, that was lost in the verbal stem.