K59.1 — Functional diarrhea
Is K59.1 billable?
Yes — K59.1 is billable for FY2027. K59.1 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. K59.1 may be submitted for encounters from October 1, 2026 through September 30, 2027.
K59.1 at a glance
| Code | K59.1 |
|---|---|
| Description | Functional diarrhea |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does K59.1 group to?
K59.1 sits in MDC 06 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 391Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders with MCCmedical
- 392Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders without MCCmedical
How is K59.1 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to K59.1. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Diarrhea, diarrheal › functional (disease) (infantile) (inflammatory)
- Diarrhea, diarrheal › neurogenic (disease) (infantile) (inflammatory)
Excludes1 — never code together
The conditions below can never be reported together with K59.1 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes1 — never code together — inherited from K59
The conditions below can never be reported together with K59.1 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes2 — not included here — inherited from Chapter 11
The conditions below are not part of K59.1, but a patient may have both at the same time. When documentation supports it, K59.1 and the excluded code may both be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Excludes2 — not included here — inherited from K59
The conditions below are not part of K59.1, but a patient may have both at the same time. When documentation supports it, K59.1 and the excluded code may both be reported.
- functional disorders of stomach (K31.-)
How long has K59.1 existed?
K59.1 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with K59.1?
ICD-10-CM declares these codes mutually exclusive with K59.1 — exactly one of each pair can be correct for a given encounter.