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ICD 10 Coding Alert

General Surgery Coding:

Brush Up on Appendicitis Diagnosis Coding

Hint: Pregnancy affects your code choices.

Coding an appendicitis diagnosis may seem more complicated than the surgeon’s work during the procedure itself.

Remember to follow the ICD-10-CM guidelines and keep these expert tips on hand to simplify the appendicitis coding journey.

Code Symptoms if No Surgery Performed

Sometimes your surgeon will evaluate a patient with suspected appendicitis but decide not to perform surgery. In those cases, without a final diagnosis, you’ll need to know how to corral the best codes to describe the patient’s symptoms.

For instance: Patient presents with right lower quadrant discomfort. Your diagnosis code choices are:

  • R10.31 (Right lower quadrant pain)
  • R10.813 (Right lower quadrant abdominal tenderness)
  • R10.823 (Right lower quadrant rebound abdominal tenderness)

To choose the correct code, you’ll need to distinguish R10.813 and R10.823Rebound tenderness involves pain or tenderness that is more pronounced after a sudden release of pressure, such as when the surgeon presses on the abdomen and then rapidly removes their hand.

Rebound tenderness often indicates an intraperitoneal inflammatory process or a more serious surgical problem, says Michael A. Ferragamo, MD, clinical assistant professor of urology at State University of New York Stony Brook.

Documentation: Your surgeon’s encounter notes should include specific language to differentiate pain, tenderness, or rebound tenderness, as well explicit indication of the site of abdominal discomfort. With that information, you can choose among the following ICD-10-CM options:

  • Right upper quadrant (R10.11, R10.811, R10.821)
  • Left upper quadrant (R10.12, R10.812, R10.822)
  • Right lower quadrant (R10.31, R10.813, R10.823)
  • Left lower quadrant (R10.32, R10.814, R10.824)
  • Periumbilical (in the area of the navel [umbilicus]) (R10.33, R10.815, R10.825)
  • Epigastric (midline above the navel [umbilicus]) (R10.13, R10.816, R10.826)
  • Generalized (R10.817, R10.827)

Because ICD-10-CM does not offer a code for “unspecified” or “other” site, if the patient has pain or tenderness in multiple sites in the abdomen, you will need to report multiple codes, one for each site.

Scrutinize Op Note for Appendicitis Dx

When your surgeon performs an appendectomy for appendicitis, specific information from the op note should guide you to the correct diagnosis code.

Acute: The first information you need is whether the case is acute appendicitis or “other” or “unspecified.” An acute condition is severe, with sudden onset, and leads to the K35 (Acute appendicitis) code family.

If the op note indicates acute appendicitis, you’ll need to decipher the following details from the documentation:

  • Generalized or local peritonitis
  • Rupture
  • Perforation
  • Abscess
  • Gangrene

Armed with that information, you can choose the correct, specific code from the following list:

  • K35.20 (Acute appendicitis with generalized peritonitis, without abscess) (Acute) appendicitis with generalized peritonitis NOS
  • K35.21 (Acute appendicitis with generalized peritonitis, with abscess)
  • K35.30 (Acute appendicitis with localized peritonitis, without perforation or gangrene) Acute appendicitis with localized peritonitis NOS
  • K35.31 (Acute appendicitis with localized peritonitis and gangrene, without perforation)
  • K35.32 (Acute appendicitis with perforation and localized peritonitis, without abscess) (Acute) appendicitis with perforation NOS Perforated appendix NOS Ruptured appendix (with localized peritonitis) NOS
  • K35.33 (Acute appendicitis with perforation and localized peritonitis, with abscess) (Acute) appendicitis with (peritoneal) abscess NOS Ruptured appendix with localized peritonitis and abscess
  • K35.80 (Unspecified acute appendicitis) Acute appendicitis NOS Acute appendicitis without (localized) (generalized) peritonitis
  • K35.890 (Other acute appendicitis without perforation or gangrene)
  • K35.891 (Other acute appendicitis without perforation, with gangrene) (Acute) appendicitis with gangrene NOS

If the appendicitis is not acute, or the op note or pathology report doesn’t specify, look to the following code options:

  • K36 (Other appendicitis) Chronic appendicitis Recurrent appendicitis
  • K37 (Unspecified appendicitis)

Take Pregnancy into Account

If your surgeon performs an appendectomy for a pregnant patient, you may need to skip using a K35-K37 code as the first-listed diagnosis.

Here’s why: The ICD-10-CM guidelines provide instructions under “General Rules for Obstetric Cases” that states the following sequencing priority for codes from Chapter 15 (O00-O9A, Pregnancy, Childbirth and Puerperium):

  • Chapter 15 codes have sequencing priority over codes from other chapters.
  • Additional codes from other chapters may be used in conjunction with chapter 15 codes to further specify conditions.
  • Should the provider document that the pregnancy is incidental to the encounter, then code Z33.1 (Pregnant state, incidental), should be used in place of any chapter 15 codes.
  • It is the provider’s responsibility to state that the condition being treated is not affecting the pregnancy.

Realizing that you should use a chapter 15 code as the principal diagnosis, you should turn to codes from category O99 (Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium) as the first-listed diagnosis for conditions such as appendicitis that could affect the pregnancy.

Do this: When your surgeon performs an appendectomy for a pregnant patient with appendicitis, the first-listed diagnosis should be O99.61- (Diseases of the digestive system complicating pregnancy).

This code requires a sixth digit, says Terri Brame Joy, MBA, CPC, COC, CGSC, CPC-I, billing specialty subject matter expert at Kareo in Irvine, California. If you don’t include the sixth digit, this “could be a reason for a denial,” she adds. The six-digit code choices are O99.611, O99.612, O99.613, or O99.619 for first, second, third, or unspecified trimester.

Following the ICD-10-CM instruction to “Use additional code to identify specific condition,” you should also report the appropriate appendicitis code for the case, such as K35.20.