2027 ICD-10-CM Diagnosis Code G57.91Unspecified mononeuropathy of right lower limb

ICD-10-CM Codes›G00–G99›G50-G59›G57

ICD-10-CM G57.91
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G57.91 is a billable ICD-10-CM diagnosis code for unspecified mononeuropathy of right lower limb. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74. Coders also document this condition as disorder of right ilioinguinal nerve. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nerve and nerve root disorders.

Code Identity

ICD-10-CM Code
G57.91
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified mononeuropathy of right lower limb
Short Description
Unspecified mononeuropathy of right lower limb
Same as the full description in the CMS dataset.
Parent Code
G57.9
Unspecified mononeuropathy of lower limb

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG50-G59Nerve, nerve root and plexus disorders
CategoryG57Mononeuropathies of lower limb
This CodeG57.91Unspecified mononeuropathy of right lower limb

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Disorder of right ilioinguinal nerve
  • Genitofemoral neuropathy
  • Neuralgia of nerve of right lower limb
  • Neuroma of right lower limb following surgery
  • Post surgical neuroma of lower limb
  • Right genitofemoral neuropathy
  • Right obturator neuropathy

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G57.91: its own notes plus those printed at G57, block G50-G59, and Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From G57 Mononeuropathies of lower limb applies to 40 codes
  • current traumatic nerve disorder - see nerve injury by body region
From Block G50-G59 Nerve, nerve root and plexus disorders applies to 106 codes
  • current traumatic nerve, nerve root and plexus disorders - see Injury, nerve by body region
  • neuralgia NOS (M79.2)
  • neuritis NOS (M79.2)
  • peripheral neuritis in pregnancy (O26.82-)
  • radiculitis NOS (M54.1-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • 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)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G57.91, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G57.91: they are not reported together with it, unless the two conditions are unrelated.

  • M79.2 Neuralgia and neuritis, unspecified
    mononeuropathies (G56-G58) names G56-G58, which includes this code

Clinical ClassificationClinical

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

CCSR NVS017
Nerve and nerve root disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Peripheral Nerve Disorders

Nerves are like wires that carry messages back and forth between your brain and your body. Your peripheral nerves branch off from your brain and spinal cord and connect to all parts of your body, including your muscles and organs.

The full article covers:

  • What are peripheral nerves?
  • What are peripheral nerve disorders?
  • What causes peripheral nerve disorders?
  • What are the symptoms of peripheral nerve disorders?
  • How are peripheral nerve disorders diagnosed?
  • What are the treatments for peripheral nerve disorders?
  • Can peripheral nerve disorders be prevented?

Read the full article at MedlinePlus

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

Convert G57.91 to ICD-9-CMHistory

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

ICD-9-CM
355.8 Mononeuritis leg NOS
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G57.91Overview

What is the ICD-10 code for unspecified mononeuropathy of right lower limb?

The ICD-10-CM code for unspecified mononeuropathy of right lower limb is G57.91 (sometimes written as G5791). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G57.91 (Unspecified mononeuropathy of lower limb) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified mononeuropathy of right lower limb on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G57.91 group to?

When unspecified mononeuropathy of right lower limb is the principal diagnosis on an inpatient stay, it groups to MS-DRG 74, 73, with relative weights from 1.0172 to 1.5773 depending on complications. Higher weights mean higher Medicare reimbursement.

Can G57.91 be reported with M79.2?

Not as a rule. The Excludes1 note at block G50-G59, which applies to G57.91, lists "neuralgia NOS (M79.2)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of G57.91?

Under the General Equivalence Mappings, unspecified mononeuropathy of right lower limb converts to ICD-9-CM 355.8 (mononeuritis leg NOS). The mapping is approximate, so confirm the match fits the documentation.