Part B Insider (Multispecialty) Coding Alert

Question: How do I code for multiple mosquito bites on a patient? Is there one code I can use?

Louisiana Subscriber

Answer: Unlike venomous insect bites, which are coded to one single code in the T63.4- (Toxic effect of venom of other arthropods) code block, the ICD-10 index instructs you to code nonvenomous insect bites “by site, superficial, insect.” In other words, you would use the insect bite code that is associated with the specific superficial anatomical location of the bites.

So, if the patient has multiple mosquito bites on the cheek, shoulders, and lower back, you would code the following:

• S00.86- - Insect bite (nonvenomous) of other part of head
• S40.26- - Insect bite (nonvenomous) of shoulder
• S30.860- - Insect bite (nonvenomous) of lower back and pelvis.

For each of these codes, you will need to apply the appropriate sixth or seventh digit to indicate whether the physician is treating the patient for an initial encounter (A), a subsequent encounter (D), or sequela (S) of the condition.

You will also need to provide the appropriate external cause code which, in this case, would be W57.XXXA- (Bitten or stung by nonvenomous insect and other nonvenomous arthropods, initial encounter), again adding the appropriate seventh digit depending on the nature of the encounter. Per ICD-10-CM guidelines, this code will be sequenced after the injury code as, like all external cause codes, it “should never be sequenced as the first-listed or principle diagnosis.”  

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