A patient who has colon adenocarcinoma undergoes an open partial colectomy.

1. Procedure and CPT® Code Selection:

The patient underwent an open partial colectomy involving the removal of the proximal colon and terminal ileum with reconnection of the distal ileum to the remaining colon.

CPT® Code 44160 is specific for an open partial colectomy with removal of a portion of the colon and the terminal ileum with an ileocolostomy (reconnection of the ileum to the colon). This accurately describes the procedure performed.

Code 44140 is for a partial colectomy without removal of the terminal ileum, making it inappropriate in this case.

Codes 44205 and 44204 involve laparoscopic approaches for colectomy procedures, but since this procedure was open, these codes are not suitable.

2. Diagnosis and ICD-10-CM Code Selection:

ICD-10-CM Code C18.2 is for a malignant neoplasm of the ascending colon, which is specified in this case as colon adenocarcinoma.

Code C18.9 represents an unspecified malignant neoplasm of the colon, which is less specific than C18.2. Therefore, C18.2 is the most accurate choice based on the location of the adenocarcinoma.

3. AAPC and CPT® Coding Guidelines:

Per AAPC guidelines, selecting the correct colectomy code involves identifying the specific approach (open vs. laparoscopic) and anatomical structures resected, both of which align with 44160 for this open ileocolic resection.

Thus, the correct answer, based on CPT® and ICD-10-CM guidelines, is D. 44160, C18.2.