2026 ICD-10-CM Diagnosis Code P78.1Other neonatal peritonitis

ICD-10-CM Codes›P00–P96›P76-P78›P78

ICD-10-CM P78.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

P78.1 is a billable ICD-10-CM diagnosis code for other neonatal peritonitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neonatal digestive and feeding disorders.

Code Identity

ICD-10-CM Code
P78.1
Billable Status
Yes — Valid for Submission
Code Describes
Other neonatal peritonitis
Short Description
Other neonatal peritonitis
Same as the full description in the CMS dataset.
Parent Code
P78
Other perinatal digestive system disorders

Code Classification

ChapterP00–P96Certain conditions originating in the perinatal period
SectionP76-P78Digestive system disorders of newborn
CategoryP78Other perinatal digestive system disorders
This CodeP78.1Other neonatal peritonitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute infectious peritonitis
  • Acute localized peritonitis caused by infection
  • Aseptic peritonitis
  • Bacterial peritonitis
  • Fat necrosis of peritoneum
  • Fibrinous peritonitis
  • Infectious peritonitis
  • Mesenteric fat necrosis
  • Mesenteric peritonitis with mesenteric fat necrosis
  • Neonatal peritonitis
  • Peritonitis
  • Pneumococcal peritonitis
  • Primary peritonitis
  • Serositis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Neonatal peritonitis NOS

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • congenital
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • neonatal

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR PNL012
Neonatal digestive and feeding disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Serositis

    inflammation of a serous membrane.

  • Chylous Ascites

    presence of milky lymph (chyle) in the peritoneal cavity, with or without infection.

  • Coronavirus, Feline

    a species of coronavirus infecting cats of all ages and commonly found in catteries and zoos. cats are often found carrying the virus but only a small proportion develop disease. feline coronavirus and feline infectious peritonitis virus (fipv) are virtually the same virus in genetic and antigenetic terms, and are morphologically indistinguishable. since they only differ in their disease potential (with fipv causing a more serious illness), they are considered biotypes of each other.

  • Familial Mediterranean Fever

    a group of hereditary autoinflammation diseases, characterized by recurrent fever, abdominal pain, headache, rash, pleurisy; and arthritis. orchitis; benign meningitis; and amyloidosis may also occur. homozygous or compound heterozygous mutations in marenostrin gene encoding pyrin result in autosomal recessive transmission; simple heterozygous, autosomal dominant form of the disease also exists with mutations in the same gene.

  • Feline Infectious Peritonitis

    common coronavirus infection of cats caused by the feline infectious peritonitis virus (coronavirus, feline). the disease is characterized by a long incubation period, fever, depression, loss of appetite, wasting, and progressive abdominal enlargement. infection of cells of the monocyte-macrophage lineage appears to be essential in fip pathogenesis.

  • Peritonitis

    inflammation of the peritoneum lining the abdominal cavity as the result of infectious, autoimmune, or chemical processes. primary peritonitis is due to infection of the peritoneal cavity via hematogenous or lymphatic spread and without intra-abdominal source. secondary peritonitis arises from the abdominal cavity itself through rupture or abscess of intra-abdominal organs.

  • Peritonitis, Tuberculous

    a form of peritonitis seen in patients with tuberculosis, characterized by lesion either as a miliary form or as a pelvic mass on the peritoneal surfaces. most patients have ascites, abdominal swelling, abdominal pain, and other systemic symptoms such as fever; weight loss; and anemia.

  • Bacterial Peritonitis

    peritonitis that is caused by a bacterial infection.

Patient EducationClinical

Peritoneal Disorders

Your peritoneum is the tissue that lines your abdominal wall and covers most of the organs in your abdomen. A liquid, peritoneal fluid, lubricates the surface of this tissue.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert P78.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
777.8 Perinat GI sys dis NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About P78.1Overview

Is P78.1 (Other perinatal digestive system disorders) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other neonatal peritonitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of P78.1?

Under the General Equivalence Mappings, other neonatal peritonitis converts to ICD-9-CM 777.8 (perinat GI sys dis NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.