Bowel /ˈbaʊəl/: spelled b-o-w-e-l. A commonly confused word is bowl /bəʊl/, one letter shorter and a different word entirely.
The ow here says /aʊ/, and there is a small extra syllable, unlike bowl, where the l sound follows the diphthong directly. The doctor examined his bowel.
Same sounds, different words
The ache was deep in his bowels. Say it as two beats, /ˈbaʊ.əl/, so the extra syllable is audible.
She served soup in a bowl. One beat, /bəʊl/. If you hear that extra little syllable, the spelling needs the e: b-o-w-e-l.
The two words are near-homophones in some accents, so trust the context, not the ear alone: intestines take bowel, dishes and games take bowl.