Max Rady College of Medicine

Concept: Day Surgery Hospitalizations

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Concept Description

Last Updated: 2011-12-06


    This concept discusses the methods used at MCHP to identify day surgery cases that can be used for further analyses. The identification of day surgery cases is primarily used in the counting of hospital separations, where only inpatient and outpatient (day) surgery cases are counted. The number of hospital separations is a commonly used measure of the utilization of hospital services. In Manitoba, hospitals are not required to submit hospital discharge abstracts for all medical outpatients, but an abstract is required for inpatient separations and most outpatient surgical cases.


  • Day surgery hospitalizations are those where patients receive "surgical" services in hospital without being admitted to the hospital. It is important to define day surgery hospitalizations consistently overtime in order to accurately count hospital separations in Manitoba hospitals, otherwise changes in coding practices could result in fluctuations that are not a reflection of actual changes to hospital utilization.

  • In Manitoba, hospitals are not required to file a hospital discharge abstract for all medical outpatients. Thus, only surgery outpatient claims are consistently defined in the hospital discharge abstracts data. For this reason, only inpatient and day surgery claims are typically counted when measuring hospital utilization. Admission Status is only recorded for Manitoba Hospital admissions.

  • The number of day surgeries seen over time may vary because of changes in reporting requirements in the hospital discharge abstract. This means that simply using admission status or institution level of Care to identify day surgery for comparisons across time can be misleading. Several methods have been used in the past to minimize the effect of changes in reporting requirements.

    EXAMPLE: Biopsies

    The excision or destruction of lesion or tissue of skin and subcutaneous tissue (ICD-9-CM procedure code 86.2) provides an example of how changes in reporting requirements can cause significant changes in the number of day surgery cases. As of April 2001, the 'removal/biopsy of lumps and bumps' has been removed from the required codes for recording day surgery events in the Hospital Abstracts User's Manual (HAUM). This includes mostly ICD-9-CM procedure code 86.3, but also 86.1, 86.2 (associated with tariff code 0253 (0254 0116 0112); 0253 is Excision and simple closure). This caused a very significant decrease in day surgery events as defined by surgical Diagnosis Related Group (DRG™) and possibly Day Procedure Group (DPG™) from 2001/02 onward.

Current Method for Identifying Day Surgery Hospitalizations

    The appropriate method for identifying day surgery cases depends on the years of data used in the project.

2003/04 and Earlier: Identify Day Surgery Using Diagnosis Related Groups (DRGs)

    Since 1989, DRGs and related codes have been assigned to each case in the Hospital Discharge Abstracts data, based on ICD-9-CM diagnosis and procedure codes. Charlyn Black and Marni Brownell developed a list of DRGs that had higher resource use, likely required an operating room. Cases with these surgical DRGs were considered less likely to fluctuate in the reporting requirements over time.

    An advantage to using DRGs to identify Day Surgery cases is that while the DRG revision may change from year to year, the DRG surgical/medical formats (DRGSM) are consistent.

    NOTE: Although DRGs are not strictly designed for use with outpatient cases, they do provide a reasonable method of identifying surgical/medical cases.


    MCHP uses SAS® formats to assist in the identification of medical/surgical cases. These formats identify the surgical/medical designation for each DRG code value. An example of a DRG Surgical/Medical format is available for downloading: drg13sm.txt . The content of this format is based on information from the Diagnosis Related Groups (DRG) Definitions Manual (version 13.0).


    Several DRG Surgical/Medical formats exist. Each file is designed specifically for the corresponding DRG version (year) used to code the abstract file. Ensure that you are using the appropriate formats.

    The excision of destruction of lesion or tissue of skin and subcutaneous tissue (ICD-9-CM procedure codes 86.1, 86.2, 86.3) were no longer required to be reported in the hospital discharge abstract system as of April 1, 2001. If day surgeries are reported across this time period these procedures should be removed from earlier years.

    See SAS code below for more information.

2004/05-2008/09: Identify Day Surgery Using Day Procedure Groups (DPGs)

    DPGs are assigned to each day procedure in the hospital discharge abstract. DPGs are used to categorize similar day surgery cases and are an extension of the CIHI Case Mix Groups (CMG™) patient classification system.

    When the Discharge Abstract Database / Manitoba Abstract Data Elements (DAD/MADE) hospital discharge abstract was introduced in 2004/05, the DRG software could no longer be used to define day surgery. The hospital separations in 2003/04 were used as a cross-walk year to see which DPGs aligned with the DRGs we normally used to identify day surgery cases.

    CIHI tends to change how interventions are grouped into DPGs every two years, and in 2007 CIHI did a complete overhaul on the coding of DPGS: DPGs changed from two digit codes to four digits, and many more codes were added. Again, a cross-walk was provided between the two and four digit codes so we could look back and see what DPGs were included from day surgery previously.


    The format identifies CIHI 2009 Version DPGs that should not be considered day surgery cases. This format can be used with 2004/05-2008/09 hospital discharge abstracts data and the corresponding CIHI CMG extras file that contains the 2009 Version DPGs.


    CIHI changes the meaning of the DPG codes nearly every year, so identifying the codes to include/exclude has to be revisited annually.

    Similar to earlier years, changes in reporting requirements may impact the number of day surgeries reported. Excluding the DPG codes in the format above will give a consistent definition to the DRG definition used above. Please NOTE that this is only valid for 2004/05-2008/09. Prior to these years and afterwards, DPG codes may change meaning and this list will need to be re-visited.

    In addition, there may be changes to abstract requirements over time that will affect the selection of specific interventions.

    See SAS code below for more information.

OLDER Method: Identify Day Surgery Using ICD-9-CM Codes

    NOTE: This method is OUTDATED - DO NOT USE !!

    This method was used in the 1995 project Health Reform in Three Provinces: A Comparative, Longitudinal Study. Since Manitoba was the only province in this study that used Diagnosis Related Group (DRGs) to identify surgical outpatient cases, a DRG proxy was developed that uses ICD-9-CM procedure codes.

    • An ICD-9-CM procedure code was considered surgical if over five years of Manitoba outpatient hospital discharge abstracts (91/92 to 95/96) it was most likely associated with a surgical DRG, otherwise it was considered medical.
    • A large majority of ICD-9-CM outpatient procedures were either exclusively surgical or medical or had at least a 10 to 1 ratio in favour of either.
    • The DRG ICD-9-CM "crosswalk" is implemented in a SAS format $SURGMED which categorizes a 4 digit ICD-9-CM outpatient procedure as either 'S'urgical,'M'edical, or 'X' unknown. When evaluated against the gold standard of DRG, the format was able to identify surgical and medical outpatient with at least 96% accuracy in any one year between 91/92 and 95/96.
    • See ICD-9 / DRG Crosswalk from the Health Reform in Three Provinces: A Comparative, Longitudinal Study for more information on this method.


      MCHP uses SAS® formats to assist in the identification of surgical cases. These formats identify the surgical/medical/other designation for each case. The Outpatient Surgical/Medical format used in this project is available for downloading: surgmed.txt

      CAUTION: This format was designed specifically to identify outpatient surgical cases for this project.

      NOTE: A similar crosswalk was created to identify inpatient surgical and obstetrical cases for this project. (see Method 3 in the concept titled: Identifying Obstetrical / Surgical Inpatients Using ICD-9-CM Codes ).

      See SAS code below for more information.

Day Care Definitions from HAUM and DAD Overtime

    The following information is provided for historical perspective.

HAUM (1995)

    The definition of Day Surgery from the 1995 HAUM is: Admission Status 4 (Day Care) following the HAUM Appendix G (Reportable Same Day Cases). Note that the definition has changed several times.

    Hospitals must use the Abstract Program (MHSC Form 48A) to report on all Surgical Day Care Cases as defined below:

    • A patient who attends a hospital same day program with pre- and post-interventional protocols for a scheduled elective surgical, diagnostic and/or therapeutic procedure under sedation or a local, regional or general anesthetic. The patient would be registered, but not admitted. Entry Code '1' (Direct) must be recorded.

      Note: A surgical Day Care Visit can occur in the surgical suite, emergency unit or other area like an endoscopy unit.

    • A patient who attends the Emergency Department with a condition which necessitates a surgical procedure in the surgical suite but for whom an admission to an in-patient bed is not required (e.g. D & C and open reduction fracture). Entry Code '2' (Emergency) must be recorded.


    • If a procedure listed on the Same Day Case Procedure Code Reference List falls into either case (as defined above), a Day Care abstract must be submitted.
    • Hospital discharge abstract submission is not required for: hemodialysis, chemotherapy, intravenous therapy, blood transfusions and preadmission clinics.

HAUM (2001)

    These guidelines are to be used to determine Day/Night Care visits that should be reported using the Hospital Discharge Abstract Program. These guidelines consider the location of the surgery, type of anesthetic used, length of stay, length of recovery period, use of special equipment or specially trained staff:

    1. All procedures done in an operating room suite regardless of anesthetic technique should be reported as Day/Night Care visits.

    2. All procedures performed under general anesthetic, regardless of location, should be reported as Day/Night Care visits.

    3. The following criteria define a Day/Night Care scheduled procedure when three (3) or more of the criteria generally apply:

        3.1 - Attends for 3 to 12 hours on average; stay does not exceed 24-hours.
        3.2 - Uses a designated suite, e.g. Endoscopy Suite, Cath Lab, Angiography Suite. Note: Emergency Room is not considered to be a designated suite.
        3.3 - Requires spinal or epidural anesthetic, conscious sedation or anesthetic standby.
        3.4 - Requires a monitored recovery period within the hospital, which on average is longer than one hour.
        3.5 - Requires special equipment and/or specially trained staff that are not typically found in a clinic/physician's office (i.e.: high capital cost or complex equipment).

    4. Procedures in the "No" category on the attached list (see link to file below), performed on Pediatric patients, may sometimes be exceptions and reported as Day/Night Care visits, due to the requirement of specially trained staff or additional monitoring required.

    5. A malignant diagnosis does not automatically mean the case has to be coded and abstracted as a Day/Night Care visit. Malignancies are reported to CancerCare Manitoba via pathology reports.

    6. Other risk factors such as existing comorbidities or mental disability may be a valid reason for performing and reporting a scheduled procedure as a Day/Night Care visit.

    7. All other scheduled procedures regardless of time, location or duration should be classified as non-abstractable outpatient or clinic visits.

    NOTE: Click here to open a list of example procedures that would qualify as Day/Night Care visits and examples of those procedures that would be excluded according to the above criteria. These are not exhaustive lists but they are meant to provide additional guidance in applying the guidelines.

DAD (2004/05)

    Institution Level of Care 1 or 7 (equivalent to transact = "3"). Manitoba has adopted the name of Day/Night Care to identify their Day Surgery Cases. Hospitals should report cases as day/night care if the patient is not admitted to an inpatient bed and is discharged within a 24-hour period and three (3) or more of the following criteria are met:

    1. Attends for 3 to 12 hours on average; stay does not exceed 24-hours.
    2. Uses a designated suite, e.g. endoscopy suite, Cath lab, angiography suite. Note: Emergency Room is not considered to be a designated suite.
    3. Requires a monitored recovery period within the hospital, which on average is longer than one hour.
    4. Requires special equipment and/or specially trained staff that are not typically found in a clinic/physician's office (i.e. high capital cost or complex equipment).

      Note: if a stay continues for longer than 24 hours then the patient will be admitted under a second abstract.

    Similar to the HAUM 2001 version, this criterion considers the location of the surgery, length of stay, length of recovery period, and use of special equipment/staff; however it does not consider the type of anesthetic used.

    Cancelled Day Surgery: The data elements to be recorded on a cancelled day surgery abstract are: date of intervention, word CANCELLED, intervention provider number/service* and anesthetic technique of 8. For any cancelled case, regardless of level of care, record a code from rubric Z53 to indicate the reason the intervention was cancelled. An additional code (diagnosis type 3--secondary) may be assigned to identify the condition the patient was originally admitted for.


SAS code and formats 

Related concepts 

Related terms 


  • Diagnosis-Related Groups
  • hospital utilization

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Manitoba Centre for Health Policy
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Rady Faculty of Health Sciences,
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