- Hydrencephalocele (congenital) 742.0
- Hydrencephalomeningocele (congenital) 742.0
- Hydroa 694.0
- Hydroadenitis 705.83
- Hydrocalycosis (see also Hydronephrosis) 591
- Hydrocalyx (see also Hydronephrosis) 591
- Hydrocele (calcified) (chylous) (idiopathic) (infantile) (inguinal canal) (recurrent) (senile) (spermatic cord) (testis) (tunica vaginalis) 603.9
- Hydrocephalic fetus
- Hydrocephalus (acquired) (external) (internal) (malignant) (noncommunicating) (obstructive) (recurrent) 331.4
- Hydrocolpos (congenital) 623.8
- Hydrocystoma (M8404/0) - see Neoplasm, skin, benign
- Hydroencephalocele (congenital) 742.0
- Hydroencephalomeningocele (congenital) 742.0
- Hydrohematopneumothorax (see also Hemothorax) 511.89
- Hydromeningitis - see Meningitis
- Hydromeningocele (spinal) (see also Spina bifida) 741.9
- Hydrometra 621.8
- Hydrometrocolpos 623.8
- Hydromicrocephaly 742.1
- Hydromphalus (congenital) (since birth) 757.39
- Hydromyelia 742.53
- Hydromyelocele (see also Spina bifida) 741.9