Combined ICD10 codes

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To code some diagnoses as part of ICD10 collection, several lines of entries in the Patient viewer tab ICD10 need to be grouped together.

To group diagnoses together, use the same Dx Priority for all of them.

Combined coding does not apply to CCI Collection (there is no priority), and there is nothing in the data that links a CCI code to the Dx it is related to.

Coding instructions


  • There are numerous situations in which multiple codes need to be listed in order to accurately reflect what's going on medically.
  • For some situations the multiple codes need to be linked together (we use the term "combined").
  • For other situations it's just a matter of ensuring that the multiple codes are all in the diagnosis list -- i.e. they don't need to be combined.
  • There are some Dxs that can only be expressed as combinations, see #Some specific cases

Clinical Situation Plus its Cause

  • Many ICD10 codes are for manifestations of disease, not a specific disorder per se.
  • In their Wiki articles it will say something like "also code cause if known" e.g: Hematemesis
  • If the cause is an infection, the Wiki article will instruct to "also code infection source", e.g: Shock, septic
  • In general, when you have a manifestation and a cause, the two codes should be combined.
    • For example, in Septic Shock that has led to liver failure, the two should be coded with the same priority.

Situations in which linking is completely reasonable:

  • link bugs with an infection,
  • link trauma with its mechanism,
  • link codes to “create” an entity for which no separate ICD10 code exists, such as retroperitoneal hemorrhage,
  • to connect cause with effect(s), e.g. a trauma combined with all the separate fractured bones.

Q&A: Just How Far Should You Go in Linking Cause and Effect Diagnoses?

  • If it is abundantly clear that A caused B that caused C and all of A, B, and C are all Admit or all Acquired, then combine them together. If it is possible but not COMPLETELY clear that the items are causally linked, then do NOT combine them
  • Example#1: Stabbed --> lots of internal organ injuries from the stabbing --> big blood loss ---> hemorrhagic shock --> cardiac arrest.
  • Example #2: Chemotherapy --> N/V as an adverse effect --> dehydration --> orthostatic syncope. But Chemo also caused drug-induced thrombocyotopenia as an adverse effect. And Chemo also caused Skin rash as an adverse effect. And all were present on admission (or all occurred after admission and so are Acquired diagnoses). In this case we have the Chemo causing problems in 3 separate pathways. Here again, we want you to combine all 6 codes together with the same priority number.
   Adverse effect of chemo ---> N/V --> dehydration --> syncope 
   Drug-induced thrombocytopenia
  • What about when there's a diagnosis (A) which is a known risk factor for another diagnosis (B). But in fact B is influenced by other things, not only A. In this case, do NOT combine A and B.
    • Example: Diabetes is a risk factor for MI. But so are hypertension, hyperlipidemia and genetic factors. So here do NOT combine the MI with the diabetes (or the hypertension or hyperlipidemia) because it's not a direct arrow from diabetes to MI. But of course, do code all of these diagnoses that are present (in the example that means code the diabetes and the MI, and hypertension if present, etc).

Thanks for clarifying the diabetes issue. DPageNewton 12:21, 2019 October 10 (CDT)

Primary Admit Diagnosis in Combined Codes

See Primary Admit Diagnosis

Dxs that can only be expressed as combinations

Some entities can only be coded with a combination of two codes.


Some specific cases

Malignancy with Metastasis

Metastasis and their primary tumor should be coded in combination because the codes for mets don't specify the primary site, only the site of the mets.

Codes for the mets can be found at:

Metastasis codes:

Codes for the primary tumors can be found at:

Neoplastic codes:
... further results

Traumas and their Mechanisms

  • In ICD10, traumas need to be combined with separate mechanism codes to fully explain the situation.
  • Here are lists of the codes for "mechanical" injuries to various body parts:
    • some codes are always traumatic and always need a mechanism:
Trauma codes:
... further results
  • Other codes may or may not be of a traumatic nature; these also qualify to be coded with trauma mechanisms listed below:
Category:Potential trauma codes:
  • Here is a list of the external mechanism or agent that caused the trauma:
Mechanism codes:

Regarding Multiple Trauma

Iatrogenic injuries


Infections in ICD10 have combined coding requirements for some of their pathogens. Any that have antibiotic resistances would store those as Combined ICD10 codes as well. If the infection is acquired in the hospital, see Nosocomial infection, NOS. See Infections in ICD10 for more info.

Attribution of infections

See Attribution of infections

Antibiotic resistance

Antibiotic resistance is coded as Combined ICD10 codes of the condition/pathogen and the resistance. See Antibiotic Resistant Organism for more info.

Antibiotic resistance codes:

Symptom/Sign/Test Result not needed when cause known

  • This code identifies a symptom or a sign, or an abnormal test result, not a disorder.
    • So, you must strive to code the cause of the symptom or sign, if known.
    • And if you do know the cause and code it, also coding this symptom/sign as Combined ICD10 codes is OK, but optional.
      • In the case of multi-system diagnoses, where a specific symptom/sign/test result is actually causing the hospital admission, and this would not be clear from just the condition itself, do make sure you code the symptom as well.

Patient who has Wegener's granulomatosis is admitted due to Hemoptysis. Usually coding the Hemoptysis would be optional, but Wegener's granulomatosis doesn't always present with this, and unless it is causing problems it would not alone be a reason to admit the patient, so you should code the Hemoptysis.

  • Sometimes there may be multiple symptom/sign/test result that might or might NOT be related by virtue of having the same underlying cause. Since in the absence of KNOWING that cause, such assumptions may well be incorrect, do NOT combine them together if you are not certain they actually have the same underlying cause.

Other co-codes

  • In addition to the combined coding situations listed above, you can combine codes when it makes sense to you to do so. The general guideline should be that codes be combined (instead of just both listed in the diagnosis list) when they are strongly related to each other.
  • Use your judgement. Either listing them separately, or combined ensures that they're all there.

CCMDB Data Integrity Checks

Some codes always need to be combined with one or more others.

Most infection codes require combined-coding of a pathogen (some have it implied, like Mumps), and some disorders can have a pathogen if their cause is infectious. See Bug required for details.

Transition notes

Yes, this different from how we used to use dx priorities where they had to be unique.


The records are combined by same L_ICD10.Dx Priority.

Related articles

Related articles: