Z18.31 Retained animal quills or spines

Billable ICD-10-CM code, FY2026. Exempt from present-on-admission (POA) reporting.

Applies from Z18 Retained foreign body fragments

Includes

• embedded fragment (status)
• embedded splinter (status)
• retained foreign body status

Excludes1 (never code together)

• artificial joint prosthesis status (Z96.6-)
• foreign body accidentally left during a procedure (T81.5-)
• foreign body entering through orifice (T15-T19)
• in situ cardiac device (Z95.-)
• organ or tissue replaced by means other than transplant (Z96.-, Z97.-)
• organ or tissue replaced by transplant (Z94.-)
• personal history of retained foreign body fully removed Z87.821
• superficial foreign body (non-embedded splinter) - code to superficial foreign body, by site

MS-DRG index

Defines the logic of DRG(s) 951 in MDC 23.

Approximate ICD-9-CM (GEMs)

• V90.31 Retained animal quills or spines

Medicare Code Edits (MCE v43.1 (April 2026))

• Unacceptable principal diagnosis: These codes describe a circumstance which influences care but is not a current illness or injury, or capture only an underlying condition, and are unacceptable as principal diagnosis.

Code annotations containing back-references to Z18.31

Back-references to Z18.3

• Use Additional: H44.7 Retained (old) intraocular foreign body, nonmagnetic ("code to identify nonmagnetic foreign body (Z18.01-Z18.10, Z18.12, Z18.2-Z18.9)")

Back-references to Z18

• Use Additional: H02.81 Retained foreign body in eyelid ("code to identify the type of retained foreign body (Z18.-)")
• Use Additional: H05.5 Retained (old) foreign body following penetrating wound of orbit ("code to identify the type of retained foreign body (Z18.-)")
• Use Additional: L92.3 Foreign body granuloma of the skin and subcutaneous tissue ("code to identify the type of retained foreign body (Z18.-)")
• Use Additional: M60.2 Foreign body granuloma of soft tissue, not elsewhere classified ("code to identify the type of retained foreign body (Z18.-)")
• Use Additional: R78 Findings of drugs and other substances, not normally found in blood ("code to identify the any retained foreign body, if applicable (Z18.-)")
• Use Additional: R79 Other abnormal findings of blood chemistry ("code to identify any retained foreign body, if applicable (Z18.-)")
• Use Additional: R82 Other and unspecified abnormal findings in urine ("code to identify any retained foreign body, if applicable (Z18.-)")
• Type 1 Excludes: Z03.82 Encounter for observation for suspected foreign body ruled out ("retained foreign body (Z18.-)")
• Type 2 Excludes: Z77 Other contact with and (suspected) exposures hazardous to health ("retained foreign body (Z18.-)")

Diagnosis Index entries for Z18.31

• Retained › foreign body fragments (type of) › animal quill (s) or spines
• Retained › foreign body fragments (type of) › quill (s) (animal)
• Retained › foreign body fragments (type of) › spine (s) (animal)
• Retained › fragments (type of ) › animal quill (s) or spines
• Retained › fragments (type of ) › quill (s) (animal)
• Retained › fragments (type of ) › spine (s) (animal)

Nearby codes

• Z18.10 Retained metal fragments, unspecified
• Z18.11 Retained magnetic metal fragments
• Z18.12 Retained nonmagnetic metal fragments
• Z18.2 Retained plastic fragments
• Z18.3 Retained organic fragments
• Z18.31 Retained animal quills or spines (this code)
• Z18.32 Retained tooth
• Z18.33 Retained wood fragments
• Z18.39 Other retained organic fragments
• Z18.8 Other specified retained foreign body
• Z18.81 Retained glass fragments