Watch tricky hierarchy switch from ICD-9 to ICD-10.
You'll have the same number of code choices and the same diagnostic distinctions for coding inguinal hernias when ICD-9 becomes ICD-10 in 2013. But elevating the bilateral/unilateral distinction from the fifth digit in ICD-9 to the fourth digit in ICD-10 confounds the one-to-one code correspondence.
ICD-9 Prioritizes Gangrene, Obstruction
ICD-9 lists three, four-digit codes for inguinal hernia:
550.0 -- Inguinal hernia with gangrene
550.1 -- Inguinal hernia, with obstruction, without mention of gangrene
550.9 -- Inguinal hernia, without mention of obstruction or gangrene.
You should append a fifth digit to each of these codes to distinguish bilateral/unilateral and recurrent or not, as follows:
0 -- unilateral or unspecified (not specified as recurrent)
1 -- unilateral or unspecified, recurrent
2 -- bilateral (not specified as recurrent)
3 -- bilateral, recurrent.
ICD-10 Prioritizes Gangrene, Obstruction, and Unilateral/Bilateral
ICD-10 lists six, four digit codes for inguinal hernia:
K40.0 -- Bilateral inguinal hernia, with obstruction, without gangrene
K40.1 -- Bilateral inguinal hernia, with gangrene
K40.2 -- Bilateral inguinal hernia, without obstruction or gangrene
K40.3 -- Unilateral inguinal hernia, with obstruction, without gangrene
K40.4 -- Unilateral inguinal hernia, with gangrene
K40.9 -- Unilateral inguinal hernia, without obstruction or gangrene.
You should append a fifth digit to each of these codes to distinguish recurrent or not as follows:
0 -- not specified as recurrent
1 -- recurrent.
Put Them Together for 12 Codes
Because of the hierarchy difference, you can't find a direct correspondence for the four-digit codes. For instance, 550.0 could be K40.1 or K40.4.
Crosswalk: You do have a one-to-one crosswalk of the five-digit inguinal hernia codes from ICD-9 to ICD-10, as follows:
550.00 - K40.40
550.01 - K40.41
550.02 - K40.10
550.03 - K40.11
550.10 - K40.30
550.11 - K40.31
550.12 - K40.00
550.13 - K40.01
550.90 - K40.90
550.91 - K40.91
550.92 - K40.20
550.93 - K40.21