K50.113

Crohn's disease of large intestine with fistula

Crohn's disease of the large intestine with fistula is a specific clinical manifestation of Crohn's disease, a chronic inflammatory bowel disease (IBD) that causes transmural inflammation of the digestive tract. In this subtype, the inflammation is localized to the colon (large intestine) and has progressed to form a fistula—an abnormal tunnel-like connection between the intestine and another organ, the skin, or another part of the bowel. These fistulas are a result of deep ulcerations that penetrate through the entire thickness of the intestinal wall. Common types include enteroenteric (between loops of bowel), enterocolic (between small and large intestine), enterovesical (between bowel and bladder), enterovaginal (between bowel and vagina), and enterocutaneous (between bowel and the skin surface). This condition often signifies a more aggressive or penetrating disease phenotype (Montreal Classification B3) and typically requires multidisciplinary management involving gastroenterology and colorectal surgery.

Clinical Symptoms

  • Chronic diarrhea, often with mucus or blood
  • Persistent abdominal pain and cramping, frequently in the lower quadrants
  • Unintentional weight loss and malnutrition
  • Drainage of pus, stool, or gas from a skin opening (enterocutaneous)
  • Recurrent urinary tract infections or passage of gas/feces in urine (enterovesical)
  • Passage of stool or gas from the vagina (enterovaginal)
  • Fever and chills associated with localized inflammation or abscess
  • Fatigue and malaise
  • Tenesmus (frequent urge to evacuate the bowels)
  • Perianal pain or discharge if associated with perianal disease

Common Causes

  • Genetic predisposition involving mutations in genes such as NOD2/CARD15
  • Dysregulated immune system response to commensal gut microbiota
  • Gut microbiome dysbiosis (imbalance of intestinal bacteria)
  • Environmental triggers including tobacco use, which significantly increases the risk of fistula formation
  • High-fat or highly processed Western diets
  • Chronic transmural inflammation leading to deep fissuring ulcers

Documentation & Coding Tips

Explicitly link the fistula to the Crohn's disease of the large intestine to support the K50.113 classification.

Example: Patient with established Crohn's disease localized to the descending colon and rectum presents with a new enterocutaneous fistula. The fistula originates from the inflamed segment of the large intestine. Assessment: Crohn's disease of large intestine with fistula (K50.113), currently in an active flare requiring biologic adjustment. Risk Adjustment: This represents a chronic condition with a major complication (fistula), impacting the Hierarchical Condition Category (HCC 188) and increasing the clinical complexity and medical decision-making for the current encounter.

Billing Focus: Documentation must specify both the site (large intestine) and the complication (fistula) to justify K50.113 over more general codes.

Describe the anatomical origin and terminus of the fistula specifically within the note.

Example: Physical exam and pelvic MRI reveal an enterovaginal fistula originating from the sigmoid colon, which shows significant mural thickening consistent with the patient's Crohn's disease of the large intestine. Diagnosis: Crohn's disease of the large intestine with fistula (K50.113). Plan: Evaluation for surgical seton placement and initiation of Infliximab. Billing: Laterality is not applicable here, but site specificity (large intestine vs. small intestine) is mandatory for 2026 coding standards.

Billing Focus: Identify the large intestine as the primary site of transmural inflammation leading to the fistula.

Document the current state of disease activity, such as active flare versus clinical remission.

Example: Patient with known Crohn's of the large intestine presents with increased drainage from a chronic perianal fistula. Colonoscopy confirms active inflammation in the cecum and ascending colon. Impression: Crohn's disease of the large intestine with fistula, active exacerbation (K50.113). Medical Decision Making: High complexity due to the risk of sepsis from fistula drainage and the need for immunosuppressant modification.

Billing Focus: Activity status (active flare) supports the necessity of more frequent office visits or high-intensity CPT codes.

Include all extraintestinal manifestations and comorbid conditions related to IBD.

Example: Evaluation of Crohn's disease of the large intestine with a persisting enterovesical fistula. Patient also exhibits associated episcleritis and migratory arthralgia. ICD-10 Coding: K50.113 (Crohn's with fistula), L52 (Erythema nodosum), and M02.37 (Reactive arthropathy). Billing: Ensure all secondary codes are linked to the primary diagnosis to demonstrate the systemic nature of the disease.

Billing Focus: Linking comorbidities justifies multi-system reviews during E/M coding.

Clearly document the treatment plan, including biologics and surgical interventions for the fistula.

Example: Management of Crohn's colitis with an internal fistula between the transverse colon and the duodenum. Patient is currently on maintenance Vedolizumab but requires the addition of Ciprofloxacin and Metronidazole for fistula management. Surgical consult for possible bowel resection is requested. Diagnosis: Crohn's disease of the large intestine with fistula (K50.113). Billing: This justifies a 99215 E/M level due to the high risk of morbidity and complex drug management.

Billing Focus: Documentation of complex drug management (biologics/antibiotics) supports higher MDM levels for billing.

Relevant CPT Codes

Related Diagnoses

Hierarchy