Pediatric Coding Alert

Question: A 16-year-old female patient came to our office with infectious mononucleosis and an enlarged spleen, which occurred due to the disease. The B27 (Infectious mononucleosis) code series in the ICD-10-CM includes several codes that use fifth characters to designate complications, but infectious mononucleosis with enlarged spleen is not one of them. Should we document the patient’s spleen condition with a separate code, such as R16.1 (Splenomegaly, not elsewhere classified)?

Vermont Subscriber

Answer: Infectious mononucleosis, caused by the Epstein-Barr virus, has several symptoms: weakness and fatigue, swollen lymph nodes and tonsils, fever, and a severe sore throat are among the most common. A swollen liver or spleen are other, less common complications that may result from the illness.

You correctly point out that there are several codes in the B27 series that document complications with a fifth character: XXX.X1 (… with polyneuropathy); XXX.X2 (… with meningitis); and XXX.X9 (… with other complications). However, an enlarged spleen is not specified with a character, so you would have to code either B27.09 (Gammaherpesviral mononucleosis with other complications) or B27.19 (Cytomegaloviral mononucleosis with other complication) depending on test results or, less specifically, B27.89 (Other infectious mononucleosis with other complication) or B27.99 (Infectious mononucleosis, unspecified with other complication).

Once you have documented the mononucleosis diagnosis, however, you cannot document the enlarged spleen. Sections B5 and B6 of the ICD-10-CM Official Guidelines for Coding and Reporting specifically state that “signs and symptoms that are associated routinely with a disease process should not be assigned as additional codes, unless otherwise instructed by the classification.” CMS goes on to note that the only times symptoms and signs are “acceptable for reporting purposes” are “when a related definitive diagnosis has not been established (confirmed) by the provider.”

So, had your patient reported to your practice complaining of pain from the enlarged spleen before your provider diagnosed the mononucleosis — which is unlikely but not impossible — you could make the case for documenting a code such as R16.1. But as your physician diagnosed the mononucleosis first, then determined the enlarged spleen was a result of the mononucleosis, you would only report a B27 code for this encounter.