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2025 ICD-10-CM code K35.21

Acute appendicitis with generalized peritonitis and abscess.

Appropriate coding requires precise documentation of all findings and procedures.Detailed descriptions of the extent of peritonitis and the presence or absence of complications (such as perforation or gangrene) are crucial for accurate code selection.

Modifiers may be applicable depending on the circumstances of the case.Consult the latest CPT and/or HCPCS coding guidelines for appropriate modifier usage.

Medical necessity for treatment is established by the presence of clinical symptoms and imaging findings consistent with acute appendicitis.Generalized peritonitis and abscess formation represent a serious threat to the patient's health requiring prompt surgical intervention or drainage and antibiotic treatment to prevent sepsis and other life-threatening complications.

The clinical responsibility for this diagnosis and subsequent treatment rests primarily with a surgeon.Pre-operative assessment and post-operative care may involve other specialists, such as internists or infectious disease specialists, depending on the patient's comorbidities and the course of their recovery.

IMPORTANT:Related codes include K35.20 (acute appendicitis with generalized peritonitis, without abscess), K35.30-K35.33 (acute appendicitis with localized peritonitis, with various specifications of perforation and abscess), and K35.8 (other and unspecified acute appendicitis).

In simple words: This code describes a serious infection of the appendix causing inflammation of the abdominal lining and a pus-filled pocket.

This code signifies acute inflammation of the vermiform appendix, accompanied by generalized peritonitis (inflammation of the peritoneum, the membrane lining the abdominal cavity) and the presence of an abscess (a localized collection of pus).

Example 1: A 25-year-old female presents to the emergency department with severe right lower quadrant abdominal pain, fever, and nausea. Physical examination reveals tenderness to palpation in the right lower quadrant. Imaging studies (CT scan) confirm acute appendicitis with generalized peritonitis and an abscess. The patient undergoes emergency appendectomy and abscess drainage., A 16-year-old male is admitted with symptoms consistent with acute appendicitis. He has a history of Crohn's disease.Laparoscopic appendectomy reveals diffuse peritonitis and an abscess formation in the appendix.He receives intravenous antibiotics, drainage, and close monitoring postoperatively. Due to his Crohn's disease, his post-operative care involves a gastroenterologist in collaboration with the surgical team., A 60-year-old male with a history of diabetes presents with abdominal pain, fever, and leukocytosis.Examination reveals guarding and rebound tenderness.CT scan shows an appendiceal abscess with surrounding inflammatory changes consistent with generalized peritonitis.He is treated with intravenous antibiotics and percutaneous drainage of the abscess under CT guidance. Due to comorbid diabetes, his recovery period is closely monitored by a physician and diabetes care specialist.

Complete medical history including onset, location, and characteristics of abdominal pain, fever, nausea, vomiting, anorexia; Physical examination documenting tenderness, guarding, rebound, and other relevant findings; Laboratory results including complete blood count (CBC) with differential, inflammatory markers (CRP, ESR), and other relevant tests; Imaging studies (CT scan or ultrasound) demonstrating appendicitis with peritonitis and abscess; Operative report detailing surgical procedure (appendectomy, abscess drainage); Pathology report; Postoperative progress notes; Discharge summary.

** Always refer to the most current ICD-10-CM coding guidelines for accurate coding and reimbursement.This information is for guidance only and should not be considered a substitute for professional medical coding advice.

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