K51.312 ICD-10-CM Code: Ulcerative (chronic) rectosigmoiditis with intestinal obstruction
K51.312 maps to CMS-HCC V28 HCCs 78 and 81. Source-labeled RAF references are available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Diseases of the digestive system (K00-K95) / Noninfective enteritis and colitis (K50-K52)
K51.312
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceUlcerative (chronic) rectosigmoiditis with intestinal obstruction
Chronic inflammation with ulcers in the rectum and sigmoid colon that is causing a blockage in the intestines.
Buddy Insight
Ulcerative rectosigmoiditis with intestinal obstruction is a serious mechanical complication where inflammation in the rectum and sigmoid colon causes bowel blockage.
CMS-HCC V28
MappedHCC 78
Coefficient HCC 78: 0.326 (Community Non-Dual Aged (CNA)); HCC 81: 0.244 (Community Non-Dual Aged (CNA))
+ HCC 81
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 045
Code-level coefficient reference
+ HCC 048
ESRD/PACE
MappedHCC 33
Code-level coefficient reference
+ HCC 35
RXHCC
MappedHCC 67
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for K51.312. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from K00-K95
- certain infectious and parasitic diseases (A00-B99)Inherited from K00-K95
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from K00-K95
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from K00-K95
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from K00-K95
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from K00-K95
- neoplasms (C00-D49)Inherited from K00-K95
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from K00-K95
Related Codes
Includes
Official- noninfective inflammatory bowel diseaseInherited from K50-K52
Excludes 1
Official- irritable bowel syndrome (K58.-)Inherited from K50-K52, K51
- megacolon (K59.3-)Inherited from K50-K52, K51
- Crohn's disease [regional enteritis] (K50.-)Inherited from K50-K52, K51
Code First
OfficialNo Code First sequencing instructions are included in this display for K51.312. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify any associated fistulas, if applicable:Inherited from K51
- anal fistula (K60.3-)Inherited from K51
- anorectal fistula (K60.5-)Inherited from K51
- rectal fistula (K60.4-)Inherited from K51
- code to identify manifestations, such as:Inherited from K51
- pyoderma gangrenosum (L88)Inherited from K51
Code Also
OfficialNo Code Also instructions are included in this display for K51.312. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is K51.312 an HCC code?
Yes. K51.312 (Ulcerative (chronic) rectosigmoiditis with intestinal obstruction) maps to HCC 78, Intestinal Obstruction/Perforation and HCC 81, Ulcerative Colitis under the CMS-HCC V28 risk adjustment model, with source-labeled community non-dual aged reference coefficients HCC 78 0.326 and HCC 81 0.244. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: K51.312 is billable and maps to V28 HCC 78, Intestinal Obstruction/Perforation and HCC 81, Ulcerative Colitis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- K51.312
- Description
- Ulcerative (chronic) rectosigmoiditis with intestinal obstruction
- HCC (V28)
- HCC 78 — Intestinal Obstruction/Perforation; HCC 81 — Ulcerative Colitis
- RAF reference coefficient
- HCC 78: 0.326; HCC 81: 0.244
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work K51.312 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for K51.312
For K51.312, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
K51.312 is the ICD-10-CM diagnosis code for ulcerative (chronic) rectosigmoiditis with intestinal obstruction. Chronic inflammation with ulcers in the rectum and sigmoid colon that is causing a blockage in the intestines. K51.312 sits in the ICD-10-CM chapter for diseases of the digestive system (k00-k95), within the section covering noninfective enteritis and colitis (k50-k52).
Under the CMS-HCC V28 risk adjustment model, K51.312 maps to Intestinal Obstruction/Perforation (HCC 78) with a source-labeled community, non-dual, aged reference coefficient of 0.326. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Document evidence of intestinal obstruction in the clinical notes. For K51.312, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for K51.312 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document evidence of intestinal obstruction in the clinical notes
- •Distinguish between partial and complete obstruction if documented
Clinical Significance
Ulcerative rectosigmoiditis with intestinal obstruction is a serious mechanical complication where inflammation in the rectum and sigmoid colon causes bowel blockage. This may occur from stricture formation due to chronic inflammation and often requires hospitalization for bowel rest, decompression, or surgical intervention.
Documentation Requirements
- ✓Confirmed ulcerative colitis of the rectum and sigmoid colon
- ✓Imaging or clinical evidence of intestinal obstruction
- ✓Documentation of obstruction type (partial vs. complete) and location
- ✓Provider statement linking obstruction to the rectosigmoiditis
- ✓Treatment plan including conservative management or surgical consultation
- ✓Assessment for stricture versus inflammatory cause
Commonly Confused Codes
- •K51.312 vs K56.69: K56.69 is other intestinal obstruction unrelated to inflammatory bowel disease
- •K51.312 vs K51.012: K51.012 is pancolitis with obstruction (entire colon involvement)
- •K51.312 vs K51.512: K51.512 is left-sided colitis with obstruction (more extensive)
- •K51.312 vs K51.311: K51.311 is rectosigmoiditis with rectal bleeding, not obstruction