Uniform Hospital Discharge Data Set

Uniform Hospital Discharge Data Set

The UHDDS is a data set used by acute care hospitals to report inpatient data elements. These elements are standardized, which means that these same data elements are required for all acute care hospitals that receive Medicare and Medicaid funding. The UHDDS has elements that are used in the calculation of MS-DRGs (the inpatient payment system). They include things such as which diagnosis are to be reported, what should be considered the principal diagnosis and which procedures should be reported. It is also important to point that that, as is often the case, other insurance agencies may very well use this same set of data requirements.

UHDDS Data Elements

The following table shows all the data elements contained in the UHDDS. I have highlighted the ones that pertain specifically to coding of the chart.

Data Elements

UHDDS (Uniform Hospital Discharge Data Set )


Personal Identifier


A unique number identifying the patient, applicable to the individual regardless of health care source or third-party arrangement.


Date of Birth


4 digits for year of birth but 3 digits are adequate to capture the century









Race : American Indian/Eskimo/Aleut

Asian or Pacific Islander

Black         White       Other Race       Unknown

Ethnicity : Spanish/Hispanic Origin Not of Spanish/Hispanic Origin Unknown




Usual residence, full address and zip code (nine digit zip code, if available)


Hospital Identification


A unique institutional number across data systems, to allow for tracking and linkage of multiple records; preferably the Medicare provider number


Admission Date


Month , day, and year. Clarification is added to this data item to note that for emergency and observation type patients, the time of admission is guided by the time that the physician gives the order to admit the patient as an inpatient.


Type of Admission


Scheduled : defined as an arrangement with the admissions office at least 24 hours prior to admission. Unscheduled: all other admissions


Discharge Date


Month , day and year.


Physician Identification: Attending


Each physician should have a unique identification number across all hospitals and data systems. The

Medicare Unique Physician Identification (UPIN) is recommended.


Physician Identification: Operating


As above


Principal Diagnosis


The condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.

Qualifier : All substantiated diagnoses that affect the current hospital stay. Code to the highest degree of certainty.


Other Diagnoses


All conditions that coexist at the time of admission, or develop subsequently, which affect the treatment received and/or the length of stay.   Diagnoses that relate to an earlier episode which have no bearing on the current hospital stay are to be excluded.

Qualifier : All substantiated diagnoses that affect the current hospital stay. Code to the highest degree of certainty.


Qualifier for other diagnoses


A qualifier is given for each diagnosis coded under " other diagnoses " to indicate whether the onset of the diagnosis preceded or followed admission to the hospital. The option " uncertain " is permitted


External Cause of Injury



The ICD-9-CM code for the external cause of injury, poisoning, or adverse effect. Hospitals should complete this item whenever there is a diagnosis of an injury, poisoning or adverse effect.


Official Coding Guidelines

The Official Coding Guidelines address the required use of the UHDDS guidelines in Section II. Selection of Principal Diagnosis "The circumstances of inpatient admission always govern the selection of principal diagnosis. The principal diagnosis is defined in the Uniform Hospital Discharge Data Set (UHDDS) as "that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care."

The UHDDS definitions are used by hospitals to report inpatient data elements in a standardized manner. These data elements and their definitions can be found in the July 31, 1985, Federal Register (Vol. 50, No, 147), pp. 31038-40.

Since that time the application of the UHDDS definitions has been expanded to include all non-outpatient settings (acute care, short term, long term care and psychiatric hospitals; home health agencies; rehab facilities; nursing homes, etc)."

The UHDDS guidelines DO NOT apply to the outpatient environment.

 Can you tell me?


Principal Diagnosis

We just discussed how one of the required UHDDS elements is the principal diagnosis. The definition for principal diagnosis is "the condition established after student to be chiefly responsible for occasioning admission to the hospital". This definition is VITAL and you must know it.

Why is it so important to get this right? I mean if you at least make sure that you are coding everything wrong with the patient then that is all that should really matter right? Wrong - the Principal Diagnosis (PDX) drives the MS-DRG - and remember the MS-DRG is how we get paid as an inpatient. So what you put first matters - it matters a lot. Not only does it drive the payment, but it tells an important picture of the patient - it tells us what was so wrong with them that you could not be managed as an outpatient anymore.

Not only does the PDX determine the MS-DRG for payment, but the MS-DRG is also used to calculate a hospitals case-mix. A case-mix is the mix of patients that are treated by the hospital. The case mix shows how sick a hospitals patients are.

 True or false?

 "The condition established after study to be chiefly responsible for occasioning admis soin to the hospital."

After Study

After Study means that the patient has to be worked up before they can be sure what is wrong with them. To work a patient up means that you do tests - could be lab tests, x-rays, CT scans, scopes, exploratory surgeries, or medication trials. It might take a while before we are sure what the PDX is - it could be a couple of days even! It is not necessarily what the doctor initially thought was wrong with the patient and it is not necessarily the worst thing that happened during their hospital stay. It is the disease/syndrome/injury that made them be admitted - after all tests were done.

For example: The patient may come in with fever and cough and the physician may start with an admitting diagnosis of pneumonia. Then they start running tests and doing x-rays and they finally determine the patient really has tuberculosis.  Well, AFTER STUDY they found TB, not pneumonia so the principal diagnosis would be TB. The diagnosis may shift and change over the course of the visit - that is why it is important to review the ENTIRE medical record to determine the condition that should be designated the principal diagnosis.

Chiefly responsible for occasioning admission to the hospital

People can have lots of things wrong with them – what we are searching for is the thing that took them over the edge and made them come to the hospital.  It does not have to even be the worst thing they have wrong with them – just the one that caused the admission.  People can have many debilitating chronic diseases (like diabetes, congestive heart failure, COPD, etc) - and while those diseases make the patient's life a daily struggle, they are not always the reason they had to be admitted to the hospital this time.

For example, let's say a patient has congestive heart failure (CHF)– now this is a debilitating disease.  For the most part, people can be on meds and are able to stay at home and go about their business (although somewhat slower).  Let's say this person ends up getting acute gastroenteritis (AGE) and they have severe nausea and vomiting with dehydration and need to be admitted for IV fluid rehydration. The gastroenteritis and dehydration probably also make the CHF worse because you are messing with your body's fluid system. So always ask yourself these two questions

  1. What made them get off the couch and come in?
  2. Where is the doctor focusing his treatment?

They were perfectly content sitting on their couch with their CHF and the drugs they were on for it. It was not until they got sick from the AGE which led to dehydration that they moved off the couch. On top of that they are on IV fluids. You do not treat CHF with IV fluids - in CHF you have too much fluid already - you treat dehydration with IV fluids. Therefore the dehydration is the principal diagnosis.

Let's do another one. A patient has chronic kidney failure and is on dialysis. They start running a fever and feel weak. They are admitted to the hospital. After testing the physician determines the patient has pneumonia. They begin IV antibiotics. On the third day of their hospital stay the patient's BUN spikes and the patient becomes very ill and goes into end stage kidney failure. They fall into a coma and never recover. They expire in the hospital. In this case, even though the kidney failure was clearly the most severe thing wrong with the patient, and ultimately caused their death, it was the pneumonia that necessitated their admission into the hospital. Focus on what got them out of the chair and into the hospital.

Reading through these two scenarios also hopefully underlines how important it is that you understand the pathology of disease and how diseases are treated. You have to understand what symptoms are integral to which disease so you know what conditions are receiving the focus of treatment.

To recap:

By the way, and admitting diagnosis is the condition the physician thinks the patient may have - it is similar to the Patient Reason for Visit in the hospital outpatient world - or the "chief complaint". It is a best guess on first look.

 True or false?

 True or false?



Let's practice picking the Principal Diagnosis

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