Is K65.9 a billable ICD-10-CM code?

Yes. K65.9 is a billable, specific ICD-10-CM code and is valid for submission on a claim.

Where does K65.9 sit in the tabular list?

Diseases of the digestive system (K00-K95), in the block Diseases of peritoneum and retroperitoneum (K65-K68).

What cannot be coded together with K65.9?

K65.9 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above K65.9 (K65) and apply to it just the same.

K65.9

K65.9 — Peritonitis, unspecified

Billable / specific codeICD-10-CM

K65.9 is a billable, specific ICD-10-CM code for peritonitis, unspecified. It is valid for submission on a claim.

Inclusion terms

Alternative wordings a physician may use in the chart for this same code.

Bacterial peritonitis NOS

Excludes1 inherited from the categories above K65.9

These are not written on K65.9, but they bind it: a note on a category applies to every code beneath it. Billing K65.9 with anything listed here is a denial.

Written on K65 — Peritonitis

acute appendicitis with generalized peritonitis (K35.2-)
aseptic peritonitis (T81.6)
benign paroxysmal peritonitis (E85.0)
chemical peritonitis (T81.6)
gonococcal peritonitis (A54.85)
neonatal peritonitis (P78.0-P78.1)
pelvic peritonitis, female (N73.3-N73.5)
periodic familial peritonitis (E85.0)
peritonitis due to talc or other foreign substance (T81.6)
peritonitis in chlamydia (A74.81)
peritonitis in diphtheria (A36.89)
peritonitis in syphilis (late) (A52.74)
peritonitis in tuberculosis (A18.31)
peritonitis with or following abortion or ectopic or molar pregnancy (O00-O07, O08.0)
peritonitis with or following appendicitis (K35.-)
puerperal peritonitis (O85)
retroperitoneal infections (K68.-)

Other codes that can never be billed with K65.9

These codes carry an Excludes1 note pointing at K65.9. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading K65.9 alone.

K65.2Spontaneous bacterial peritonitis

Risk adjustment

K65.9 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:

HCC 78 Intestinal Obstruction/Perforation0.326 RAF

Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.

Medicare coverage

K65.9 is named in 2 Medicare coverage policies — 2 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

A56421Billing and Coding: CT of the Abdomen and Pelvis
A56580Billing and Coding: Computerized Axial Tomography (CT), Thorax

How K65.9 is indexed

Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to K65.9.

Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
Fistula›peritoneum
Hemoperitoneum›infectional

Code history

K65.9 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.

Related codes at this level

Codes that share K65. If K65.9 is not quite right, the correct code is usually one of these.

Questions about K65.9

Is K65.9 a billable ICD-10-CM code?: Yes. K65.9 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does K65.9 sit in the tabular list?: Diseases of the digestive system (K00-K95), in the block Diseases of peritoneum and retroperitoneum (K65-K68).
What cannot be coded together with K65.9?: K65.9 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above K65.9 (K65) and apply to it just the same.