| K65 | Peritonitis |
| K65.0 | Generalized (acute) peritonitis |
| K65.1 | Peritoneal abscess |
| K65.2 | Spontaneous bacterial peritonitis |
| K65.3 | Choleperitonitis |
| K65.4 | Sclerosing mesenteritis |
| K65.8 | Other peritonitis |
| K65.9 | Peritonitis, unspecified |
| K66 | Other disorders of peritoneum |
| K66.0 | Peritoneal adhesions (postprocedural) (postinfection) |
| K66.1 | Hemoperitoneum |
| K66.8 | Other specified disorders of peritoneum |
| K66.9 | Disorder of peritoneum, unspecified |
| K67 | Disorders of peritoneum in infectious diseases classified elsewhere |
| K68 | Disorders of retroperitoneum |
| K68.1 | Retroperitoneal abscess |
| K68.11 | Postprocedural retroperitoneal abscess |
| K68.12 | Psoas muscle abscess |
| K68.19 | Other retroperitoneal abscess |
| K68.9 | Other disorders of retroperitoneum |