ICD-10-CM and CPT Codes for Diverticulitis with Abscess
For diverticulitis with abscess, use ICD-10-CM code K57.2 (diverticulitis of large intestine with perforation and abscess) or K57.8 (diverticulitis of intestine with perforation and abscess), and for percutaneous drainage, use CPT code 49405 (image-guided percutaneous drainage of appendiceal or other intra-abdominal, pelvic, or retroperitoneal abscess).
ICD-10-CM Diagnosis Coding
The appropriate diagnosis code depends on the specific anatomic location and whether perforation is documented:
- K57.20: Diverticulitis of large intestine with perforation and abscess without bleeding
- K57.21: Diverticulitis of large intestine with perforation and abscess with bleeding
- K57.80: Diverticulitis of intestine, part unspecified, with perforation and abscess without bleeding
- K57.81: Diverticulitis of intestine, part unspecified, with perforation and abscess with bleeding
The presence of an abscess in diverticulitis is coded as "complicated diverticulitis" and falls under the K57.2x or K57.8x series 1. Research confirms that these codes have a positive predictive value of 0.98 for identifying diverticular disease overall, though specificity for complications varies 2.
CPT Procedure Coding for Abscess Drainage
When percutaneous drainage is performed, the appropriate CPT code is:
- 49405: Image-guided percutaneous drainage of appendiceal or other intra-abdominal, pelvic, or retroperitoneal abscess
This code applies when drainage is performed under ultrasound, CT, or fluoroscopic guidance 3.
Clinical Context for Coding
Size-based treatment determines whether drainage is coded:
- Small abscesses (≤4 cm): Typically managed with antibiotics alone for 7 days—no drainage procedure to code 3
- Large abscesses (>4 cm): Percutaneous drainage combined with antibiotics for 4 days—code both diagnosis and drainage procedure 3
The 2024 Italian guidelines specify that percutaneous drainage should be combined with antibiotic therapy for large diverticular abscesses, with treatment duration of 4 days in immunocompetent, non-critically ill patients if source control is adequate 3.
Important Coding Considerations
Common pitfalls to avoid:
- Do not use uncomplicated diverticulitis codes (K57.3x series) when an abscess is present
- The presence of any abscess automatically classifies the condition as complicated diverticulitis
- If surgical intervention is required instead of percutaneous drainage, different CPT codes apply (colectomy codes 44140-44160)
- For patients requiring emergency surgery due to failed drainage or peritonitis, add appropriate surgical procedure codes 3, 1
The WSES classification system divides complicated diverticulitis into stages, with abscesses ≤4 cm classified as Stage 2B and abscesses >4 cm as Stage 3A 1. This staging helps guide both treatment decisions and appropriate coding.