July 21, 2008

Coding for Gastroenteritis
For The Record
Vol. 20 No. 15. P. 28

Gastroenteritis, a nonspecific condition causing the stomach and intestines to become irritated and inflamed, is referred to as diarrhea associated with nausea and vomiting and may be classified as inflammatory, secretory, osmotic, or motile. The small intestines are primarily affected because of increased levels of diarrheal fluids and a greater loss of electrolytes and nutrients.

The most common cause of gastroenteritis is viral, and it typically lasts for one to two days. Gastroenteritis due to a virus is classified to ICD-9-CM subcategory 008.6. Some common viruses include the following:

• norovirus, also called Norwalklike virus (008.63);

• rotavirus (008.61);

• adenovirus (008.62); and

• astrovirus (008.66).

Bacteria is another common cause, and symptoms typically last longer than two days. Code assignment for bacterial gastroenteritis depends on the organism involved. Gastroenteritis due to Escherichia coli is most common and is classified to subcategory 008.0. A fifth-digit subclassification is needed as follows:

• 008.00, E. coli unspecified;

• 008.01, Enteropathogenic E. coli;

• 008.02, Enterotoxigenic E. coli;

• 008.03, Enteroinvasive E. coli;

• 008.04, Enterohemorrhagic E. coli; or

• 008.09, Other intestinal E. coli infections.

Other bacterial gastroenteritis include the following:

• Aerobacter aerogenes (008.2);

• Proteus (mirabilis) (morganii) (008.3);

• Staphylococcus (008.41);

• Pseudomonas (008.42);

• Campylobacter (008.43);

• Yersinia enterocolitica (008.44);

• Anaerobic enteritis, not otherwise specified (008.46);

• Gram-negative bacteria (008.47); and

• Unspecified bacterial gastroenteritis (008.5).

Gastroenteritis due to Clostridium difficile (008.45) occurs in the large intestine after a patient has taken antibiotics for an extended period of time. Gastroenteritis due to Shigella is classified to category 004, with a fourth-digit subcategory needed to identify the type.

Gastroenteritis due to food poisoning is caused by the following:

• Staphylococcal food poisoning (005.0);

• Botulism food poisoning (005.1); or

• Salmonella gastroenteritis (003.0).

Gastroenteritis documented as infectious but with an unspecified organism is classified to code 009.0. If the gastroenteritis is not further specified and noninfectious, assign code 558.9. In ICD-9-CM, the terms gastroenteritis, colitis, and enteritis are used interchangeably.

Dehydration
Dehydration may be caused by inadequate fluid intake, vomiting, diarrhea, sweating, or polyuria. Signs include weakness, lightheadedness, decreased urination, dry skin, dry mucous membranes, poor skin turgor, and a lack of sweat and tears. Increased lab values that may be present with dehydration include hematocrit, blood urea nitrogen (BUN) to creatinine ratio (usually greater than 20 to 1), urine specific gravity (1.020 to 1.032), total protein, and serum osmolality and electrolytes.

When examining these lab values to confirm a dehydration diagnosis, the coder must be aware of the patient’s other current diagnoses. Congestive heart failure and syndrome of inappropriate secretion of antidiuretic hormone may also affect the lab values in the same way.

Treatment includes oral or IV fluid administrations. When rehydrated, a patient’s weight should increase within 24 to 48 hours because the input will be greater than the output. Also, a patient’s hemoglobin and hematocrit levels will decrease, along with the total protein level. The BUN to creatinine ratio will also decrease to a normal 10 to 1 ratio.

For coding purposes, dehydration may be sequenced as the principal or secondary diagnosis, depending on the circumstances of admission and the attending physician’s judgment. Dehydration is the principal diagnosis if it is the condition established after study to be chiefly responsible for the hospital admission. If both infectious gastroenteritis and dehydration are present on admission and are being treated equally, the infectious gastroenteritis (009.0) must be sequenced as the principal diagnosis. However, if the treatment is directed toward the dehydration only, with the infectious gastroenteritis already treated on an outpatient basis or the condition subsided, then the dehydration may then be the principal diagnosis (AHA Coding Clinic for ICD-9-CM, 1988, second quarter, pages 9-10).

Treatment
Treatment is usually directed at controlling the symptoms of dehydration, and antiemetics may be used to stop vomiting. Most patients with gastroenteritis do not warrant acute care admission unless they require IV antibiotics. In most cases, inpatient admission is required to treat the dehydration. Review the record completely to sequence the most appropriate principal diagnosis.

Coding and sequencing for gastroenteritis are dependent on the physician documentation in the medical record and application of the Official Coding Guidelines for inpatient care. Also, use specific AHA Coding Clinic for ICD-9-CM and American Medical Association CPT Assistant references to ensure complete and accurate coding.

— This information was prepared by Audrey Howard, RHIA, of 3M Consulting Services. 3M Consulting Services is a business of 3M Health Information Systems, a supplier of coding and classification systems to nearly 5,000 healthcare providers. The company and its representatives do not assume any responsibility for reimbursement decisions or claims denials made by providers or payers as the result of the misuse of this coding information. More information about 3M Health Information Systems is available at www.3mhis.com or by calling 800-367-2447.