"Nephrauxe" is a non-existent word and therefore has no officially recognized spelling. However, it can be phonetically transcribed using the International Phonetic Alphabet (IPA) as [ˈnɛfɹəʊks]. This is a combination of the sounds "n" (as in "no"), "e" (as in "bed"), "f" (as in "fish"), "r" (as in "red"), "əʊ" (as in "go") and "ks" (as in "ticks"). Such transcriptions can help linguists and language learners to study the sounds of different languages and dialects.
Hypertrophy of the kidney.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.