Diarrhea ICD-10 Codes: Complete Guide 2026 (with Quick Reference Table)

Last Updated on February 10, 2026 by Grace Oluchi

Quick Answer (TL;DR)

Most Common Diarrhea ICD-10 Codes:

• R19.7 – Diarrhea, unspecified (most frequently used)
• K59.1 – Functional diarrhea
• K58.0 – Irritable bowel syndrome with diarrhea
• P78.3 – Noninfective neonatal diarrhea
• F45.8 – Psychogenic diarrhea

Key Facts: Rotavirus remains the predominant pathogen associated with diarrhea-related mortality globally. Campylobacter was the most common bacterial agent detected in recent hospital studies. The 2026 edition of ICD-10-CM codes became effective on October 1, 2025

Quick Reference: All Diarrhea ICD-10 Codes

Code	Description	When to Use	Excludes	Billable?	DRG
R19.7	Diarrhea, unspecified	Unknown cause, not worked up yet, acute symptom	K59.1, P78.3, F45.8, K58.0	YES	391-392
K59.1	Functional diarrhea	No physical cause found after workup, chronic (>4 weeks)	R19.7, K58.0, IBS diagnosis	YES	391-392
K58.0	IBS with diarrhea	IBS diagnosis confirmed, meets Rome IV criteria	K59.1, R19.7	YES	391-392
P78.3	Neonatal diarrhea, noninfective	Baby <28 days old, non-infectious cause	A04.X (infectious)	YES	Varies
F45.8	Other somatoform disorders (psychogenic)	Stress/anxiety/emotional cause documented	–	YES	Varies
K52.9	Noninfective gastroenteritis, unspecified	Chronic, non-infectious, cause unknown	R19.7, K59.1	YES	391-392
A04.0	Enteropathogenic E. coli infection	Specific E. coli pathogen identified	–	YES	391-392
A04.1	Enterotoxigenic E. coli infection	ETEC identified	–	YES	391-392
A04.2	Enteroinvasive E. coli infection	EIEC identified	–	YES	391-392
A04.3	Enterohemorrhagic E. coli infection	EHEC identified (E. coli O157:H7)	–	YES	391-392
A04.4	Other intestinal E. coli infections	Other E. coli strains	–	YES	391-392
A04.5	Campylobacter enteritis	Campylobacter identified	–	YES	391-392
A04.6	Enteritis due to Yersinia enterocolitica	Yersinia identified	–	YES	391-392
A04.7	Enterocolitis due to Clostridium difficile	C. diff identified	–	YES	371-373
A04.8	Other specified bacterial intestinal infections	Other bacteria identified	–	YES	391-392
A04.9	Bacterial intestinal infection, unspecified	Bacterial suspected but not specified	–	YES	391-392

Understanding ICD-10-CM for Diarrhea

ICD-10-CM codes are codes that name health problems. Doctors, researchers, and policy makers use them to record, report, and study health information. Diarrhea is one of the health problems that can be coded with ICD-10-CM. Diarrhea is when you poop a lot, and your poop is watery. Diarrhea can be short or long, depending on what causes it. It can also affect your work and life. So, it is important for you to find out why you have diarrhea and how to treat it.

Medical Context: The normal water content value in stools is approximately 10 mL/kg/day in infants and young children or 200 g/day in teenagers and adults. When this exceeds normal limits, proper ICD-10-CM coding becomes necessary for medical billing and population health tracking.

What is ICD-10-CM?

ICD-10-CM is a system of codes that name different diseases, symptoms, signs, and problems. It is used by doctors, researchers, and policy makers to record, report, and study health information. ICD-10-CM is based on the ICD-10, which is made by the WHO. But ICD-10-CM has more codes and more details than ICD-10, making it better for the US health care system.

Official Guidelines: These guidelines have been approved by the four organizations that make up the Cooperating Parties for the ICD-10-CM: the American Hospital Association (AHA), the American Health Information Management Association (AHIMA), CMS, and NCHS.

ICD-10-CM codes have 3 to 7 letters and numbers. The first letter and the next two numbers tell you the main group and category of the code. The rest of the letters and numbers tell you more information about the code. For example, the code K52.9 means “Noninfective gastroenteritis and colitis, unspecified”. The letter K means that the code is about the digestive system. The numbers 52 mean that the code is about noninfective gastroenteritis and colitis. The number 9 means that the code is not specific, meaning that there is not enough information to give a more exact code.

Why Accurate Diarrhea Coding Matters

Accurate coding is important for several reasons:

For Healthcare Providers:

• Ensures proper reimbursement from insurance
• Supports quality metrics and reporting
• Helps track treatment outcomes
• Prevents claim denials and audits

For Public Health:

• Tracks disease patterns and outbreaks
• Identifies pathogen trends (like Campylobacter and Rotavirus)
• Guides prevention and intervention strategies
• Supports research and epidemiology

For Patients:

• Accurate medical records for future care
• Proper insurance coverage
• Better continuity of care
• Research contributions

Current Research: Although the global burden of diarrhea in children under five has steadily declined, it remains a significant health threat. Recent studies show geographical variations in pathogen distribution, with bacterial causes being more common in some regions.

Complete List of Diarrhea ICD-10 Codes

There are many ICD-10-CM codes that can be used for diarrhea, depending on the type, cause, and severity of the diarrhea. Here are the most common codes explained in detail:

R19.7: Diarrhea, Unspecified

What it means: This code is used for diarrhea that is not otherwise named. It can be used when there is not enough information to give a more specific code, or when the cause of diarrhea is unknown or not important. This code can be used if the patient is confirmed to have diarrhea, but the specific type is unknown.

When to use R19.7:

• Patient reports diarrhea but hasn’t been fully evaluated yet
• Cause is genuinely unknown after initial assessment
• Acute diarrhea without clear etiology
• First visit before diagnostic workup
• Documentation doesn’t provide enough detail for specific code

When NOT to use R19.7:

• Cause is known (use specific code instead)
• Patient has IBS diagnosis (use K58.0)
• Functional diarrhea confirmed after workup (use K59.1)
• Infectious agent identified (use A04.X)
• Patient is a neonate <28 days (use P78.3)

Excludes:

• Functional diarrhea (K59.1)
• Neonatal diarrhea (P78.3)
• Psychogenic diarrhea (F45.8)

K59.1: Functional Diarrhea

What it means: This code is used for diarrhea that is not caused by any physical or structural problem in the digestive system. It is often related to IBS, stress, anxiety, or food.

When to use K59.1:

• Diagnostic workup completed (colonoscopy, labs normal)
• No organic cause found
• Chronic diarrhea (lasting more than 4 weeks)
• No IBS diagnosis present
• Rome IV criteria for functional diarrhea met

When NOT to use K59.1:

• IBS diagnosis exists (use K58.0 instead)
• Cause unknown without workup (use R19.7)
• Acute diarrhea (use R19.7)
• Psychogenic component documented (consider F45.8)

Documentation requirements:

• Duration of symptoms (>4 weeks)
• Negative diagnostic testing
• Exclusion of organic causes
• Impact on daily functioning

Excludes:

• Diarrhea, unspecified (R19.7)
• Irritable bowel syndrome (K58.0)

K58.0: Irritable Bowel Syndrome with Diarrhea

What it means: This code is used for diarrhea that is caused by IBS, a problem in the digestive system that causes belly pain, bloating, and changes in bowel habits. IBS with diarrhea is one of the types of IBS, and it is more common in women and younger adults.

When to use K58.0:

• IBS diagnosis confirmed by physician
• Meets Rome IV diagnostic criteria
• Abdominal pain related to bowel movements
• Pain relieved by defecation
• Change in stool frequency or form

Rome IV Criteria (simplified):

• Recurrent abdominal pain at least 1 day/week for 3 months
• Associated with defecation
• Change in stool frequency
• Change in stool appearance
• Symptoms started at least 6 months ago

When NOT to use K58.0:

• No IBS diagnosis
• Diarrhea without abdominal pain pattern
• Organic disease found

Documentation requirements:

• IBS diagnosis statement
• Diarrhea predominance noted
• Rome criteria elements documented
• Other causes ruled out

P78.3: Noninfective Neonatal Diarrhea

What it means: This code is used for diarrhea that happens in newborns (less than 28 days old) and is not caused by any germ. It may be because of immature gut function, feeding problems, or birth defects.

When to use P78.3:

• Baby is under 28 days old
• Non-infectious cause
• May be related to feeding intolerance
• Immature gut function
• Congenital issues

When NOT to use P78.3:

• Baby is 28 days or older (use appropriate adult code)
• Infectious cause identified (use A04.X)

Common causes in neonates:

• Formula intolerance
• Immature digestive system
• Overfeeding
• Congenital conditions
• Antibiotic exposure (mother or baby)

Documentation requirements:

• Exact age (must be <28 days)
• Non-infectious nature documented
• Feeding history
• Rule out infectious causes

F45.8: Other Somatoform Disorders (Psychogenic Diarrhea)

What it means: This code is used for diarrhea that is caused by psychological factors, such as stress, anxiety, depression, or trauma. This is also called psychogenic diarrhea, and it is a type of somatoform disorder, which is a condition where physical symptoms are caused by mental or emotional problems.

When to use F45.8:

• Clear psychological trigger documented
• Stress, anxiety, depression, or trauma present
• Physical causes ruled out
• Symptoms correlate with emotional state
• Mental health component is primary driver

When NOT to use F45.8:

• Physical cause identified
• IBS diagnosis (use K58.0)
• Functional diarrhea without psych component (use K59.1)

Documentation requirements:

• Psychological assessment or diagnosis
• Temporal relationship to stressors
• Absence of physical pathology
• Mental health professional involvement (helpful)

Note: This code requires careful documentation to support medical necessity and avoid claim denials.

K52.9: Noninfective Gastroenteritis and Colitis, Unspecified

What it means: Used for chronic diarrhea that is not caused by infection and doesn’t fit other specific categories.

When to use K52.9:

• Chronic gastroenteritis/colitis present
• Non-infectious cause
• Doesn’t meet criteria for other codes
• More specific diagnosis not available

When NOT to use K52.9:

• Acute diarrhea (use R19.7)
• Functional diarrhea after workup (use K59.1)
• IBS (use K58.0)
• Infectious cause (use A04.X)

A04.X: Bacterial Intestinal Infections

What they mean: Used for infectious diarrhea with specific bacterial pathogens. Campylobacter was the most common agent detected in recent clinical studies from Lebanese hospitals.

Common bacterial codes:

• A04.0 – Enteropathogenic E. coli
• A04.1 – Enterotoxigenic E. coli (ETEC)
• A04.2 – Enteroinvasive E. coli (EIEC)
• A04.3 – Enterohemorrhagic E. coli (EHEC, O157:H7)
• A04.4 – Other E. coli infections
• A04.5 – Campylobacter enteritis (most common bacterial agent)
• A04.6 – Yersinia enterocolitica
• A04.7 – Clostridium difficile (C. diff)
• A04.8 – Other specified bacteria
• A04.9 – Bacterial infection, unspecified

When to use A04.X:

• Stool culture positive for specific pathogen
• Clinical diagnosis of bacterial diarrhea
• Positive rapid tests (e.g., C. diff)
• Epidemiological evidence (outbreak)

Documentation requirements:

• Stool culture results
• Specific pathogen identified
• Clinical presentation consistent with infection
• Treatment plan for infection

K50-K52: Inflammatory Bowel Conditions

What they mean: Covers IBD-related diarrhea including Crohn’s disease and ulcerative colitis with specific anatomical and complication modifiers.

Common codes in this series:

• K50.X – Crohn’s disease (regional enteritis)
• K51.X – Ulcerative colitis
• K52.X – Other noninfective gastroenteritis and colitis

When to use:

• Confirmed IBD diagnosis
• Specific anatomical location known
• Complications documented

Documentation requirements:

• IBD diagnosis confirmation
• Anatomical location
• Presence of complications
• Current disease activity status

How to Choose the Right Code: Decision Flowchart

Use this step-by-step guide to select the correct ICD-10 code for diarrhea:

Step 1: Check Patient Age

Is the patient under 28 days old?

• YES → Is it infectious?
  • YES → Use A04.X (with specific pathogen)
  • NO → Use P78.3 (Neonatal diarrhea)
• NO → Continue to Step 2

Step 2: Identify If Cause is Known

Is there a confirmed diagnosis?

• Infectious agent identified → Use A04.X (specific pathogen code)
• IBS diagnosis → Use K58.0 (IBS with diarrhea)
• IBD diagnosis → Use K50-K52 series (Crohn’s or UC)
• Psychogenic/stress-related → Use F45.8 (with proper documentation)
• Medication or food allergy → Use K52.X series
• Unknown or multiple causes → Continue to Step 3

Step 3: Determine Duration and Workup Status

How long has diarrhea lasted?

• Acute (<4 weeks), no workup yet → Use R19.7 (Diarrhea, unspecified)
• Chronic (>4 weeks), workup completed → Continue to Step 4

Step 4: Functional vs Unspecified

Was diagnostic workup completed?

• YES, all tests negative, no organic cause → Use K59.1 (Functional diarrhea)
• NO, cause unknown, not fully evaluated → Use R19.7 (Diarrhea, unspecified)
• YES, but doesn’t fit functional criteria → Use K52.9 (Noninfective gastroenteritis, unspecified)

Quick Decision Summary

Patient with diarrhea
    ↓
Age <28 days? → YES → Infectious? → YES → A04.X
                              ↓
                             NO → P78.3
    ↓
   NO
    ↓
Cause known?
    ↓
YES → IBS? → K58.0
     IBD? → K50-K52
     Infectious? → A04.X
     Psychogenic? → F45.8
     Other specific? → Appropriate K52.X
    ↓
   NO
    ↓
Duration >4 weeks + workup done? → YES → Organic cause ruled out? → YES → K59.1
                                                                    ↓
                                                                   NO → K52.9
    ↓
   NO
    ↓
Use R19.7

---

Documentation Requirements by Code

Proper documentation is crucial for accurate coding and reimbursement. Here’s what to document for each code:

What to Document for R19.7 (Unspecified)

Required elements: ✓ “Patient reports loose, watery stools”
✓ Frequency: “4-5 times per day”
✓ Duration: “x3 days” or “since [date]”
✓ Associated symptoms: “No blood, no fever”
✓ Impact: “Affecting work/daily activities”

Good documentation example:

“Patient presents with acute diarrhea x3 days, 5-6 watery bowel movements daily, no fever, no blood in stool. No recent travel or sick contacts. Adequately hydrated. Plan: supportive care, follow up if worsens.”

Poor documentation example:

“Diarrhea”

Why R19.7 might be denied:

• Cause is actually known but not documented
• Should be more specific code (IBS, functional)
• Insufficient detail about symptom

What to Document for K59.1 (Functional)

Required elements: ✓ Duration: “Chronic diarrhea >4 weeks”
✓ Workup completed: “Colonoscopy normal [date]”
✓ Labs negative: “Stool studies negative, CBC normal”
✓ Diagnosis statement: “Functional diarrhea”
✓ Exclusions noted: “No IBS, no organic cause found”

Good documentation example:

“Patient with chronic diarrhea >6 months. Colonoscopy [date] normal. Stool culture negative. CBC, CMP normal. No alarm symptoms. Rome IV criteria do not meet IBS. Diagnosis: Functional diarrhea. Plan: dietary modification, follow-up 3 months.”

Poor documentation example:

“Chronic diarrhea, no cause found”

Why K59.1 might be denied:

• Workup not documented
• Could be R19.7 (insufficient workup)
• Could be K58.0 (meets IBS criteria)

What to Document for K58.0 (IBS-D)

Required elements: ✓ IBS diagnosis: “Irritable bowel syndrome with diarrhea”
✓ Rome criteria elements: “Abdominal pain relieved by defecation”
✓ Pattern: “Symptoms >6 months, pain at least 1x/week”
✓ Stool characteristics: “Loose/watery stools”
✓ Exclusions: “Colonoscopy normal, celiac serology negative”

Good documentation example:

“IBS with diarrhea per Rome IV criteria. Recurrent abdominal pain for 8 months, at least 2x/week, associated with bowel movements. Pain relieved by defecation. Loose stools 4-5x/day. Colonoscopy [date] normal. Diagnosis confirmed. Plan: dietary FODMAP restriction, loperamide as needed.”

Poor documentation example:

“IBS, diarrhea”

Why K58.0 might be denied:

• IBS diagnosis not clearly stated
• Rome criteria elements missing
• Could be functional (no pain pattern)

What to Document for P78.3 (Neonatal)

Required elements: ✓ Age: “18-day-old infant” (must be <28 days)
✓ Stool description: “Loose, watery stools x6/day”
✓ Non-infectious: “Stool culture pending/negative”
✓ Potential cause: “Formula intolerance suspected” or “immature gut function”
✓ Hydration status: “Well hydrated” or “mild dehydration”

Good documentation example:

“21-day-old infant with loose stools x5 days, 8-10 watery diapers/day. Formula-fed. No fever, no blood in stool. Well hydrated, active, feeding well. Stool culture sent. Suspect formula intolerance vs. immature gut. Plan: Trial different formula, monitor hydration.”

Poor documentation example:

“Baby has diarrhea”

What to Document for F45.8 (Psychogenic)

Required elements: ✓ Psychological assessment: “Patient reports stress/anxiety”
✓ Temporal relationship: “Symptoms worsen during stressful periods”
✓ Physical workup: “Colonoscopy, labs normal”
✓ Mental health component: “Seeing therapist for anxiety”
✓ Diagnosis: “Psychogenic diarrhea” or “somatoform disorder”

Good documentation example:

“Patient with chronic diarrhea coinciding with major life stressors. Symptoms began after job loss. Colonoscopy normal. Stool studies negative. Currently in therapy for anxiety disorder. Diarrhea frequency correlates with anxiety levels. Diagnosis: Psychogenic diarrhea. Plan: Continue therapy, consider anti-anxiety medication.”

Poor documentation example:

“Stress diarrhea”

Why F45.8 might be denied:

• Insufficient psychological documentation
• Physical causes not adequately ruled out
• Requires mental health professional involvement

What to Document for A04.X (Infectious)

Required elements: ✓ Stool culture results: “Stool culture positive for Campylobacter”
✓ Clinical presentation: “Fever 101.5°F, abdominal cramping, watery diarrhea”
✓ Onset and exposure: “Symptoms began 48 hours after restaurant meal”
✓ Specific pathogen: Name exact bacteria
✓ Treatment: “Started on azithromycin”

Good documentation example:

“Acute diarrhea x2 days with fever, cramping. Stool culture positive for Campylobacter jejuni. Recent travel to Mexico. Dehydration mild. Started azithromycin 500mg daily x3 days, oral rehydration. Follow up in 1 week.”

Poor documentation example:

“Bacterial diarrhea”

Why A04.X might be denied:

• Specific pathogen not identified
• Culture results not documented
• Could be viral (different code needed)

Common Coding Mistakes & How to Avoid Them

Learn from these common errors to improve coding accuracy and prevent claim denials:

Mistake #1: Using R19.7 When Cause is Known

Wrong:
Patient has confirmed Campylobacter from stool culture → Coder uses R19.7

Right:
Use A04.5 (Campylobacter enteritis)

Why it’s wrong:
R19.7 is for unspecified diarrhea. When you know the specific cause (bacterial infection), you must use the specific code.

How to avoid:
Always check if stool culture results are available. If pathogen is identified, use A04.X series with specific fourth character.

Mistake #2: Confusing Functional (K59.1) vs Unspecified (R19.7)

Wrong:
Patient has chronic diarrhea for 6 months, no workup done → Coder uses K59.1

Right:
Use R19.7 (insufficient workup) or complete workup first then use K59.1

Why it’s wrong:
K59.1 requires diagnostic workup showing no organic cause. Without workup, you can’t confirm “functional.”

The key difference:

• R19.7 = Cause unknown because not investigated yet
• K59.1 = Cause investigated and confirmed to be functional (no organic disease)

How to avoid:
Check documentation for: colonoscopy report, stool studies, labs. If workup missing, use R19.7.

Mistake #3: Using Adult Codes for Neonates

Wrong:
2-week-old baby with diarrhea → Coder uses R19.7

Right:
Use P78.3 (Neonatal diarrhea, noninfective) if non-infectious
OR A04.X if infectious cause identified

Why it’s wrong:
Neonates (<28 days) have specific codes. Using adult codes loses important age-specific information.

How to avoid:
Always check patient age. If under 28 days old, look for P-codes first.

Mistake #4: Not Coding the Infection Specifically

Wrong:
Documentation says “bacterial diarrhea” → Coder uses A04.9 (bacterial infection, unspecified)

Right:
If documentation specifies “E. coli O157:H7” → Use A04.3
If documentation specifies “Campylobacter” → Use A04.5

Why it’s wrong:
Missing the fourth character loses specificity. Specific codes support better epidemiology tracking and may affect reimbursement.

How to avoid:
Check stool culture report for specific pathogen. Use most specific code available.

Mistake #5: Missing IBS Diagnosis and Using K59.1

Wrong:
Patient has documented IBS with diarrhea → Coder uses K59.1

Right:
Use K58.0 (IBS with diarrhea)

Why it’s wrong:
IBS has its own code. K59.1 excludes IBS.

How to avoid:
Search documentation for “IBS” or “irritable bowel syndrome.” If present, use K58.0 instead of K59.1.

Mistake #6: Using Psychogenic Code Without Proper Documentation

Wrong:
Patient mentions “stress” in passing → Coder uses F45.8

Right:
Only use F45.8 if psychological causation is clearly documented with:

• Psychological assessment
• Temporal correlation with stressors
• Physical causes ruled out
• Mental health professional involvement

Why it’s wrong:
F45.8 is a psychiatric code requiring substantial documentation. Insufficient support leads to denials.

How to avoid:
Look for mental health diagnoses, therapy notes, or psychiatry/psychology consultations. Without these, use R19.7 or K59.1.

Mistake #7: Not Updating Codes as Diagnosis Changes

Wrong:
First visit coded as R19.7 → Follow-up confirms IBS → Coder continues using R19.7

Right:
Update to K58.0 once IBS is diagnosed

Why it’s wrong:
Codes should reflect current, most accurate diagnosis. Using outdated codes affects quality metrics.

How to avoid:
Review previous visits when coding. Update codes as new information becomes available.

Mistake #8: Confusing Acute vs Chronic Criteria

Wrong:
Patient has diarrhea x5 weeks → Coder uses R19.7 (thinking it’s “acute”)

Right:
After 4 weeks, it’s chronic. Should consider K59.1 (if workup done) or K52.9

Why it’s wrong:
Duration criteria matter. Chronic diarrhea suggests need for more specific diagnosis.

How to avoid:
Note symptom duration. If >4 weeks, consider chronic codes (K59.1, K52.9) instead of R19.7.

Mistake #9: Using F45.8 Instead of K58.0 for Stress-Related IBS

Wrong:
Patient has IBS that worsens with stress → Coder uses F45.8

Right:
Use K58.0 (IBS is the primary diagnosis, even if stress exacerbates it)

Why it’s wrong:
IBS is a GI diagnosis, not psychiatric. Even though stress affects it, K58.0 is the correct code.

How to avoid:
If IBS diagnosis exists, use K58.0. F45.8 is only for purely psychogenic diarrhea without IBS.

Mistake #10: Not Checking Excludes Notes

Wrong:
Using multiple codes that exclude each other (e.g., R19.7 and K59.1 together)

Right:
Use only one code that best fits the clinical picture

Why it’s wrong:
ICD-10-CM has exclusion rules. Some codes cannot be used together.

How to avoid:
Always check “Excludes1” and “Excludes2” notes in ICD-10-CM manual before finalizing codes.

2026 ICD-10-CM Updates for Diarrhea

The 2026 edition of ICD-10-CM codes became effective on October 1, 2025. Healthcare professionals need to stay current with these updates for accurate billing and compliance.

Key Changes for 2026:

Updated Guidelines:

• Updated coding guidelines from CMS and CDC
• New specificity requirements for certain diarrheal conditions
• Changes to excluded conditions and cross-references
• Updated documentation requirements

What Changed Specifically:

1. Enhanced Excludes Notes for R19.7
   • More specific exclusions added
   • Clearer guidance on when NOT to use R19.7
   • Cross-references to functional codes updated
2. New Specificity Requirements for K52 Series
   • More anatomical detail required
   • New modifiers for severity
   • Updated complication codes
3. Changed Cross-References for Functional Disorders
   • Better differentiation between K59.1 and R19.7
   • Updated IBS coding guidance
   • Clarified overlap with other conditions
4. Updated DRG Assignments
   • Some codes moved to different DRG categories
   • Impacts reimbursement rates
   • Requires verification with current MAC guidelines

Action Items for Healthcare Facilities:

By [Date]:

1. ✓ Review all standing orders using old codes
2. ✓ Update EHR templates with 2026 codes
3. ✓ Train coding staff on new excludes
4. ✓ Verify payer requirements for new codes
5. ✓ Update billing software
6. ✓ Review documentation templates
7. ✓ Audit recent claims for compliance

Staying Updated: Staying current with these updates is crucial for healthcare professionals, providers, and payers to ensure accurate and efficient billing. The updates reflect the latest advancements in healthcare and clinical understanding.

Resources:

• CMS annual updates: www.cms.gov
• CDC ICD-10-CM guidelines: www.cdc.gov/nchs/icd
• AHIMA coding clinics: www.ahima.org
• AAPC forums: www.aapc.com

Billing & Reimbursement Guide

Understanding how diarrhea codes affect billing and reimbursement helps providers optimize revenue while maintaining compliance.

DRG Assignments for Diarrhea Codes

Most Common DRGs:

Code	Primary DRG	With MCC	Without MCC
R19.7	391-392	391	392
K59.1	391-392	391	392
K58.0	391-392	391	392
K52.9	391-392	391	392
A04.7 (C. diff)	371-373	371	373
A04.X (other bacterial)	391-392	391	392

Note: DRG assignments may vary based on:

• Principal diagnosis
• Comorbidities and complications (CC/MCC)
• Procedures performed
• Length of stay

Medicare Reimbursement Considerations

General Guidelines:

• Requires supporting documentation for all codes
• May request medical records for R19.7 (unspecified codes)
• Prefers specific codes over unspecified when possible
• Audits frequently for upcoding or incorrect code selection

Documentation Best Practices for Reimbursement:

1. Support medical necessity
2. Include all relevant symptoms
3. Document workup performed
4. Justify testing ordered
5. Show treatment rationale

Commercial Payer Requirements

Most Follow Medicare Guidelines, But:

• Some require specific modifiers
• Prior authorization for certain tests
• Step therapy requirements
• Documentation of failed conservative management

Verify with Each Payer:

• Medical policy for GI conditions
• Prior authorization requirements
• Documentation requirements
• Appeals process

Coding for Outpatient vs Inpatient

Outpatient Settings:

• Use symptom codes (R19.7) more frequently
• Focus on reason for visit
• Document presenting complaint
• May use multiple codes for complete picture

Inpatient Settings:

• More specific codes required (K59.1, K58.0, A04.X)
• Principal diagnosis drives DRG
• Comprehensive workup expected
• Document severity and complications

Common Billing Denials and How to Prevent Them

Denial Reason #1: “Insufficient Documentation”

• Prevention: Follow documentation guidelines above
• Appeal: Submit complete medical records showing medical necessity

Denial Reason #2: “Unspecified Code Used When Specific Available”

• Prevention: Check if cause is known; use specific code
• Appeal: Explain why specific code wasn’t appropriate

Denial Reason #3: “Medical Necessity Not Established”

• Prevention: Document symptoms, impact, failed conservative treatment
• Appeal: Provide literature supporting testing/treatment

Denial Reason #4: “Incorrect Code Selection”

• Prevention: Use decision flowchart; verify excludes notes
• Appeal: Show coding rationale from ICD-10-CM manual

Real-World Coding Examples

Learn from these realistic scenarios to improve your coding accuracy:

Example 1: Acute Diarrhea, Unknown Cause

Clinical Scenario: 35-year-old male presents to clinic with complaint of “diarrhea x3 days.” Reports 5-6 watery bowel movements per day. No fever, no blood in stool. No recent travel. No sick contacts. Eating normally. Hydration adequate. No abdominal pain. No vomiting.

Assessment: Acute diarrhea, likely viral or dietary.

Plan: Supportive care, oral rehydration, follow up if worsens or persists >1 week.

Correct Code: R19.7 (Diarrhea, unspecified)

Rationale:

• Acute presentation (<4 weeks)
• Cause unknown
• No diagnostic workup performed yet
• Symptom-based visit
• R19.7 is appropriate for initial presentation

Example 2: IBS with Diarrhea

Clinical Scenario: 28-year-old female with history of IBS presents for follow-up. Reports ongoing loose stools 3-4 times daily for past 8 months. Abdominal cramping 2-3x per week, relieved by bowel movement. Symptoms worse with stress. Previous colonoscopy [6 months ago] normal. Celiac panel negative. Tried FODMAP diet with partial improvement.

Assessment: Irritable bowel syndrome with diarrhea, stable.

Plan: Continue FODMAP diet, loperamide as needed, stress management.

Correct Code: K58.0 (Irritable bowel syndrome with diarrhea)

Rationale:

• IBS diagnosis previously established
• Meets Rome IV criteria (pain + bowel changes >6 months)
• Diarrhea-predominant type
• Workup completed (colonoscopy, celiac testing)
• K58.0 is specific diagnosis code

Example 3: Post-Infectious Functional Diarrhea

Clinical Scenario: 42-year-old male with diarrhea x12 weeks. Started after trip to Mexico where he had acute gastroenteritis. Initial illness resolved after 1 week, but loose stools persisted. Now 3 months later, still has 3-4 loose stools daily. Recent colonoscopy normal. Stool studies negative for ova, parasites, and bacterial pathogens. No abdominal pain. No weight loss. No alarm symptoms.

Assessment: Post-infectious functional diarrhea.

Plan: Trial of loperamide, probiotics, dietary modification. Follow up 6 weeks.

Correct Code: K59.1 (Functional diarrhea)

Rationale:

• Chronic duration (>4 weeks)
• Comprehensive workup completed
• No organic cause found
• Doesn’t meet IBS criteria (no abdominal pain pattern)
• K59.1 is appropriate for functional diarrhea without IBS

Example 4: Campylobacter Enteritis

Clinical Scenario: 22-year-old female presents to ED with severe diarrhea x2 days. Reports 10+ watery bowel movements with blood and mucus. Fever 102.1°F. Severe abdominal cramping. Ate at seafood restaurant 3 days ago. Dehydration moderate. Stool culture sent.

Follow-up: Stool culture returns positive for Campylobacter jejuni.

Assessment: Campylobacter enteritis with dehydration.

Plan: IV fluids, azithromycin 500mg daily x3 days, supportive care.

Correct Codes:

• A04.5 (Campylobacter enteritis) – primary
• E86.0 (Dehydration) – secondary

Rationale:

• Specific pathogen identified on stool culture
• A04.5 is the specific code for Campylobacter
• Dehydration coded separately as it impacts treatment
• Infectious cause requires A04.X series, not R19.7

Example 5: Neonatal Diarrhea

Clinical Scenario: 18-day-old infant brought to pediatrician by worried mother. Reports baby has had loose, watery stools for 3 days. 8-10 diapers per day. Formula-fed (started new formula 5 days ago). No fever. Baby feeding well, alert, active. Weight gain appropriate. No vomiting. Stool sample sent to rule out infection.

Assessment: Probable formula intolerance vs. infectious diarrhea. Hydration adequate.

Plan: Trial different formula. If stools don’t improve in 48 hours or if culture positive, re-evaluate.

Initial Code (Before Culture Results): P78.3 (Noninfective neonatal diarrhea)

Rationale:

• Age <28 days requires P-code
• Non-infectious suspected (formula change timing)
• Awaiting culture results
• P78.3 used pending confirmation

If Culture Positive: Change to A04.X (with specific pathogen)

Example 6: C. diff Colitis

Clinical Scenario: 68-year-old female hospitalized for pneumonia, treated with broad-spectrum antibiotics x7 days. On day 9 of hospitalization, develops profuse watery diarrhea, 12+ bowel movements in 24 hours. Abdominal distension and cramping. Fever 100.9°F. WBC elevated to 18,000. C. diff toxin assay positive.

Assessment: Clostridium difficile colitis, healthcare-associated.

Plan: Discontinue causative antibiotics. Start oral vancomycin. Contact isolation.

Correct Codes:

• A04.7 (Enterocolitis due to Clostridium difficile) – primary
• J18.9 (Pneumonia, unspecified) – secondary
• E87.1 (Hyponatremia) – if present

Rationale:

• Specific pathogen (C. diff) identified
• A04.7 is specific code for C. diff
• Different DRG than other diarrhea codes (371-373)
• Hospital-acquired infection reporting implications

Example 7: Medication-Induced Diarrhea

Clinical Scenario: 55-year-old male started metformin 2 weeks ago for diabetes. Since starting medication, has loose stools 4-5 times daily. No fever. No blood. No abdominal pain. No other recent medication or dietary changes. Otherwise feeling well.

Assessment: Metformin-induced diarrhea.

Plan: Reduce metformin dose, take with meals. If persists, switch to extended-release formulation.

Correct Codes:

• K52.1 (Toxic gastroenteritis and colitis) – primary
• T38.3X5A (Adverse effect of insulin and oral hypoglycemic drugs, initial encounter) – secondary
• E11.9 (Type 2 diabetes mellitus without complications) – tertiary

Rationale:

• Medication-induced requires K52.1 plus adverse effect code
• T-code captures which medication caused it
• Diabetes coded as it’s reason for metformin

Example 8: Stress-Exacerbated IBS vs Psychogenic

Clinical Scenario: 32-year-old female with documented IBS-D for 3 years. Recently went through divorce and reports symptoms significantly worsened. Now having 6-7 loose stools daily (up from usual 3-4). Abdominal pain more frequent. Seeing therapist for anxiety. Prior colonoscopy normal. No alarm symptoms.

Assessment: IBS with diarrhea, exacerbation related to life stress.

Plan: Continue current IBS management, increase therapy frequency, consider anti-anxiety medication.

Correct Code: K58.0 (IBS with diarrhea)

NOT: F45.8 (Psychogenic diarrhea)

Rationale:

• Primary diagnosis is IBS (organic GI disorder)
• Even though stress worsens symptoms, IBS is the correct code
• F45.8 is only for purely psychogenic diarrhea without IBS
• Anxiety can be coded separately if documented as comorbidity

Example 9: Chronic Diarrhea, Incomplete Workup

Clinical Scenario: 48-year-old male with loose stools x8 weeks. Patient delayed seeking care. First visit today. Reports 3-4 loose stools daily. No blood. No weight loss. No fever. Appetite normal. No recent travel. Physical exam unremarkable.

Assessment: Chronic diarrhea, etiology unknown. Need diagnostic workup.

Plan: Order CBC, CMP, TSH, stool culture, stool O&P, celiac panel. Schedule colonoscopy.

Correct Code: R19.7 (Diarrhea, unspecified)

NOT: K59.1 (Functional diarrhea)

Rationale:

• Even though chronic (>4 weeks), workup not yet completed
• Can’t diagnose “functional” without ruling out organic causes
• R19.7 appropriate until diagnostic testing done
• Will update code once results available

Example 10: Traveler’s Diarrhea, Pathogen Unknown

Clinical Scenario: 29-year-old female returns from India 3 days ago. Developed diarrhea last day of trip. Now 5 days of watery diarrhea, 6-7 times daily. Low-grade fever. Mild abdominal cramping. Some dehydration. Stool culture sent but won’t result for 48 hours.

Assessment: Acute infectious diarrhea, likely traveler’s diarrhea. Awaiting culture.

Plan: Oral rehydration, ciprofloxacin empirically. Re-assess when culture results.

Initial Code: R19.7 (Diarrhea, unspecified) or A09 (Infectious gastroenteritis and colitis, unspecified)

After Positive Culture: Update to A04.X (specific pathogen)

Rationale:

• Before culture results, use unspecified code
• Travel history suggests infectious cause
• Once pathogen identified, update to specific A04.X code
• R19.7 is acceptable pending culture; A09 also reasonable for presumed infection

For Medical Coders: Tips & Resources

Specialized guidance for professional coders working with diarrhea diagnoses:

Coding Best Practices

1. Always Check Lab Results

• Don’t code before stool culture results available
• Specific pathogen = specific code
• Update codes when results return

2. Review Previous Visits

• Has diagnosis changed?
• Was workup completed since last visit?
• Update codes to reflect current status

3. Use Query Process

• If documentation unclear, query provider
• Don’t assume or guess codes
• Get clarification in writing

4. Document Your Rationale

• Keep notes on why you chose specific code
• Helpful for audits and appeals
• Shows due diligence

5. Stay Current

• Annual ICD-10-CM updates
• CMS quarterly coding clinics
• AHIMA coding guidelines
• AAPC updates

Common Coder Questions Answered

Can I use R19.7 and K59.1 together?
No. These codes have an Excludes1 note. Use one or the other based on clinical picture.

When do I use A04.9 vs R19.7?
Use A04.9 when infection is suspected/documented but specific pathogen unknown. Use R19.7 when cause is completely unknown.

How specific do I need to be with A04 codes?
Use most specific code available. If culture says “E. coli O157:H7” use A04.3, not A04.4 or A04.9.

Can I code chronic and acute diarrhea together?
No. Choose the code that best represents current status. Acute vs chronic is a key distinction.

What if documentation says “functional” but no workup is documented?
Query provider. True functional diarrhea requires workup. Without it, use R19.7.

Recommended Resources for Coders

Official Resources:

• CMS ICD-10-CM Official Guidelines: https://www.cms.gov/medicare/coding-billing/icd-10-codes
• CDC ICD-10-CM Files: https://www.cdc.gov/nchs/icd/icd-10-cm.htm
• WHO ICD Information: https://www.who.int/standards/classifications

Professional Organizations:

• AAPC (American Academy of Professional Coders): www.aapc.com
• AHIMA (American Health Information Management Association): www.ahima.org

Coding Tools:

• ICD10Data.com (free code lookup)
• Encoder software (various vendors)
• EHR-integrated coding assistance

Continuing Education:

• AAPC webinars and local chapter meetings
• AHIMA coding clinics
• Specialty coding certifications (CPC, CCS, etc.)

For Healthcare Providers: Documentation Best Practices

Guidance for physicians, NPs, PAs, and other clinicians to improve coding accuracy through better documentation:

Documentation Essentials

Every Diarrhea Visit Should Include:

1. Duration and Frequency
   • How long? (days, weeks, months)
   • How many bowel movements per day?
   • When did it start?
2. Stool Characteristics
   • Consistency (watery, loose, formed)
   • Color (brown, green, yellow, bloody)
   • Presence of blood or mucus
3. Associated Symptoms
   • Fever? (record temperature)
   • Abdominal pain? (location, severity, character)
   • Nausea/vomiting?
   • Weight loss?
4. Exposures and Risk Factors
   • Recent travel?
   • Food history?
   • Sick contacts?
   • New medications?
   • Antibiotic use?
5. Previous Workup
   • Prior colonoscopy (date and results)
   • Previous stool studies
   • Lab work completed
   • Imaging studies
6. Diagnosis Statement
   • Be specific: “IBS with diarrhea” not “IBS”
   • State if cause is unknown: “Diarrhea, cause unknown”
   • Document when functional: “Functional diarrhea, organic causes ruled out”

Phrases That Support Accurate Coding

For R19.7 (Unspecified):

• “Acute diarrhea, cause unknown”
• “Diarrhea x3 days, awaiting stool culture results”
• “New onset diarrhea, needs diagnostic workup”

For K59.1 (Functional):

• “Functional diarrhea, colonoscopy [date] normal, labs negative”
• “Chronic diarrhea >8 weeks, extensive workup negative for organic cause”
• “Diagnosis: Functional diarrhea per Rome IV criteria”

For K58.0 (IBS-D):

• “IBS with diarrhea per Rome IV criteria”
• “Recurrent abdominal pain with diarrhea, relieved by defecation”
• “IBS-D, stable on current management”

For P78.3 (Neonatal):

• “18-day-old infant with noninfectious diarrhea”
• “Neonatal diarrhea, likely formula intolerance”
• “Age 21 days, loose stools, stool culture pending”

For F45.8 (Psychogenic):

• “Psychogenic diarrhea related to anxiety disorder”
• “Diarrhea temporally related to psychological stressors”
• “Physical workup negative, symptoms correlate with stress levels”

For A04.X (Infectious):

• “Stool culture positive for [specific pathogen]”
• “Campylobacter enteritis confirmed”
• “C. diff toxin positive, healthcare-associated”

What Coders Need From Your Documentation

To Differentiate Between Codes, Document:

1. R19.7 vs K59.1:
   • Was workup done? (colonoscopy, labs)
   • What were the results?
   • Duration of symptoms
2. K59.1 vs K58.0:
   • Is abdominal pain present?
   • Does defecation relieve pain?
   • Is there a formal IBS diagnosis?
3. Any code vs A04.X:
   • Are stool culture results available?
   • What pathogen was identified?
   • Is infection documented?
4. Adult codes vs P78.3:
   • Patient age (if <28 days, use P78.3)

Common Documentation Pitfalls

Pitfall #1: Vague Diagnosis

• Bad: “Diarrhea”
• Good: “Acute diarrhea, likely viral, cause unknown pending stool culture”

Pitfall #2: Missing Workup Details

• Bad: “Functional diarrhea”
• Good: “Functional diarrhea, colonoscopy [date] normal, celiac panel negative, symptom duration 6 months”

Pitfall #3: Not Updating Diagnosis

• Bad: Keeps coding R19.7 even after IBS diagnosed
• Good: Updates to K58.0 once diagnosis confirmed

Pitfall #4: Incomplete Infection Documentation

• Bad: “Bacterial diarrhea”
• Good: “Campylobacter enteritis per stool culture [date]”

Documentation Templates

Acute Diarrhea Template:

Chief Complaint: Diarrhea x[duration]
HPI: [Age/gender] with [#] loose, watery stools per day x [duration]. 
[Fever Y/N, blood Y/N, abdominal pain Y/N]. 
[Recent travel, food exposures, sick contacts, new medications]. 
Hydration status: [adequate/dehydrated].

Assessment: Acute diarrhea, [suspected cause or "cause unknown"]
Plan: [Supportive care/testing/medications]. Stool culture sent [if applicable].

Code Support: R19.7 (if cause unknown) or A04.X (if pathogen identified)

Chronic Diarrhea Template:

Chief Complaint: Chronic diarrhea x[duration]
HPI: [Age/gender] with loose stools [#] per day for [weeks/months]. 
Previous workup: [Colonoscopy date/results, lab results, imaging]. 
[Alarm symptoms Y/N: weight loss, blood, nocturnal symptoms].
[IBS criteria assessment: abdominal pain, relationship to defecation].

Assessment: [Functional diarrhea/IBS-D/other specific diagnosis]
Plan: [Management plan]

Code Support: K59.1 (functional) or K58.0 (IBS-D) with documentation of workup

For Patients: Understanding Your Medical Bill

Simplified explanation for patients trying to understand diarrhea-related medical coding and billing:

What Are These Codes on My Bill?

When you see your doctor for diarrhea, they use special codes to describe your condition. These codes help:

• Your insurance company understand what was treated
• Your doctor get paid correctly
• Public health officials track disease patterns
• Researchers study health trends

Common Codes You Might See

R19.7 – “Diarrhea, unspecified”

• What it means: You have diarrhea but the cause isn’t known yet
• When it’s used: First visit, before testing is done
• This is normal for initial visits

K59.1 – “Functional diarrhea”

• What it means: You have chronic diarrhea but tests show no disease
• When it’s used: After colonoscopy and other tests come back normal
• This means your digestive system works differently, not that it’s “all in your head”

K58.0 – “IBS with diarrhea”

• What it means: You have Irritable Bowel Syndrome with diarrhea as the main symptom
• When it’s used: After diagnosis of IBS is confirmed
• This is a real medical condition affecting how your gut works

A04.X – “Bacterial infection”

• What it means: Your diarrhea is caused by a specific germ/bacteria
• When it’s used: After stool test identifies the bacteria
• Examples: Food poisoning, traveler’s diarrhea

Why Your Code Might Change

It’s normal for your diagnosis code to change between visits:

• First visit: R19.7 (cause unknown)
• After testing: K59.1 (functional) or K58.0 (IBS) or A04.5 (infection identified)

This doesn’t mean the first doctor was wrong – it just means more information became available.

Will My Insurance Cover It?

Most insurance plans cover:

• Office visits for diarrhea evaluation
• Basic lab tests (stool culture, blood work)
• Treatment medications

Some plans require:

• Copays for office visits
• Preauthorization for colonoscopy
• Step therapy (trying basic treatments first)

Tip: Call your insurance company before expensive tests to check coverage.

What If My Claim is Denied?

Common reasons for denial:

1. “Not medically necessary”
   • Solution: Ask your doctor to write a letter explaining why testing was needed
2. “Needs preauthorization”
   • Solution: Doctor’s office should get approval before procedure
3. “Wrong code used”
   • Solution: Ask billing department to review and resubmit with correct code

You have the right to appeal denied claims!

Questions to Ask Your Doctor

To make sure billing is accurate, ask:

• “What is my specific diagnosis?”
• “What code will be used for billing?”
• “Do I need any testing?”
• “Will my insurance cover this?”
• “Should we get preauthorization?”

Red Flags for Billing Errors

Watch out for:

• Being charged for tests you didn’t have
• Multiple charges for same visit
• Codes that don’t match your diagnosis
• Surprise bills for “out of network” providers

If something looks wrong, call the billing department to ask for clarification.

Frequently Asked Questions

What is the ICD-10 code for diarrhea?

The most common ICD-10 code for diarrhea is R19.7 (Diarrhea, unspecified). However, more specific codes should be used when the cause is known:

• K59.1 for functional diarrhea (no organic cause)
• K58.0 for IBS with diarrhea
• P78.3 for neonatal diarrhea (babies under 28 days)
• A04.X for infectious diarrhea with a known pathogen

Use R19.7 only when the cause is unknown or not specified in documentation.

What is the difference between acute and chronic diarrhea in terms of ICD-10 codes?

Acute diarrhea is diarrhea that lasts for a short time, usually less than 3 to 4 weeks. Chronic diarrhea is diarrhea that lasts for a long time, usually more than 3 to 4 weeks.

The ICD-10 code for acute diarrhea is R19.7, which means diarrhea, unspecified. The ICD-10 code for chronic diarrhea depends on the workup:

• K59.1 if workup completed and functional cause confirmed
• K52.9 for noninfective gastroenteritis, unspecified
• R19.7 if chronic but not yet worked up

These codes are used when there is not enough information to assign a more specific code, or when the cause of diarrhea is unknown or irrelevant.

What are the ICD-10 codes for diarrhea caused by infections?

Diarrhea caused by infections can be coded with the category A04, which means other bacterial intestinal infections. This category includes codes for diarrhea caused by various bacteria, such as:

• A04.0-A04.4 – Various E. coli infections
• A04.5 – Campylobacter (most common bacterial agent)
• A04.6 – Yersinia enterocolitica
• A04.7 – Clostridium difficile (C. diff)
• A04.8 – Other specified bacterial infections
• A04.9 – Bacterial infection, unspecified

The codes in this category have four to six characters, depending on the type and severity of the infection.

What are the ICD-10 codes for diarrhea caused by conditions like IBD or IBS?

Diarrhea caused by conditions like inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS) can be coded with different categories:

For IBS:

• K58.0 – Irritable bowel syndrome with diarrhea

For IBD:

• K50.X – Crohn’s disease (with specific anatomical modifiers)
• K51.X – Ulcerative colitis (with specific anatomical modifiers)

The codes in the K50-K52 category have four to seven characters, depending on the type, location, and complication of the condition.

What are the ICD-10 codes for diarrhea caused by medications or food?

Diarrhea caused by medications or food can be coded with the category K52, which means other noninfective gastroenteritis and colitis. This category includes:

• K52.1 – Toxic gastroenteritis and colitis (for medication-induced)
• K52.2 – Allergic and dietetic gastroenteritis and colitis (for food allergies)
• K52.8X – Other specified noninfective gastroenteritis and colitis

Additionally, for medication-induced diarrhea, you should also code:

• The adverse effect code from the T36-T50 series
• The condition being treated

The codes in this category have four to six characters, depending on the type and cause of the diarrhea.

What are the ICD-10 codes for diarrhea caused by psychological factors?

Diarrhea caused by psychological factors can be coded with F45.8, which means other somatoform disorders. This can be used for psychogenic diarrhea.

However, this code requires:

• Clear documentation of psychological causation
• Physical causes ruled out
• Mental health component documented
• Often requires mental health professional involvement

Important: If patient has IBS that worsens with stress, use K58.0 (not F45.8), as IBS is the primary diagnosis even when stress-related.

What’s the difference between R19.7 and K59.1?

This is one of the most common questions, and it’s crucial to understand:

R19.7 (Diarrhea, unspecified) is used when:

• Cause is unknown because workup hasn’t been done yet
• Initial presentation of acute diarrhea
• Insufficient documentation to assign specific code
• Temporary code pending diagnostic results

K59.1 (Functional diarrhea) is used when:

• Diagnostic workup HAS been completed
• All tests came back negative (no organic disease found)
• Chronic diarrhea (typically >4 weeks)
• Functional diagnosis confirmed

Key difference: R19.7 = unknown without investigation; K59.1 = investigated and confirmed to be functional.

How do the 2026 ICD-10-CM updates affect diarrhea coding?

The 2026 edition of ICD-10-CM codes became effective on October 1, 2025, bringing:

• Updated coding guidelines from CMS and CDC
• New specificity requirements for certain diarrheal conditions
• Changes to excluded conditions and cross-references
• Updated documentation requirements

Healthcare providers should:

• Review the latest coding guidelines
• Update EHR templates
• Train coding staff on new excludes
• Verify payer requirements for new codes

The updates reflect the latest advancements in healthcare and clinical understanding.

What does recent research tell us about diarrhea patterns?

Recent studies from 2024-2025 show:

• Rotavirus remains the predominant pathogen globally
• Campylobacter is the most common bacterial agent in recent hospital studies
• Global burden of diarrhea in children under five continues to decline but remains significant
• Geographical variations in pathogen distribution exist
• Traveler’s diarrhea patterns are evolving (US military and traveler studies 2018-2023)
• Global incidence projections available for 2020-2040

This research supports the importance of accurate coding for public health surveillance and intervention planning.

Can I use multiple diarrhea codes together?

Generally, no. Most diarrhea codes have “Excludes1” notes that prevent using them together. For example:

• Cannot use R19.7 and K59.1 together
• Cannot use K59.1 and K58.0 together

However, you CAN:

• Use a diarrhea code with complication codes (dehydration E86.0)
• Use infectious code (A04.X) with complication codes
• Add symptom codes if they provide additional clinically relevant information

Rule of thumb: Choose the ONE code that best describes the patient’s condition.

What if the stool culture is pending?

If stool culture is pending:

• Initially code: R19.7 (Diarrhea, unspecified) or A04.9 (Bacterial infection, unspecified) if infection strongly suspected
• After results: Update to specific A04.X code if pathogen identified
• If negative: Update to appropriate code based on clinical picture (R19.7, K59.1, etc.)

Never wait to bill – use the information available at time of visit, then update when results return.

How do I code diarrhea in a nursing home patient on antibiotics?

This scenario often involves C. difficile. Code as:

• A04.7 if C. diff toxin positive
• R19.7 if testing pending
• May also code the condition being treated with antibiotics
• May code healthcare-associated infection indicators per facility protocol

Always document:

• Antibiotic use (name, duration)
• Onset of diarrhea relative to antibiotic start
• C. diff testing ordered/results
• Infection control measures

References and Research

Official ICD-10-CM Resources

1. CDC ICD-10-CM Guidelines FY26 – Official coding guidelines approved by cooperating parties
   https://stacks.cdc.gov/view/cdc/158747
2. CMS FY-2026 ICD-10-CM Guidelines – Updated coding requirements
   https://www.cms.gov/files/document/fy-2026-icd-10-cm-coding-guidelines.pdf
3. ICD-10 Data R19.7 – 2026 edition effective October 1, 2025
   https://www.icd10data.com/ICD10CM/Codes/R00-R99/R10-R19/R19-/R19.7
4. ICD-10 Data K58.0 – IBS with diarrhea coding guidelines
   https://www.icd10data.com/ICD10CM/Codes/K00-K95/K55-K64/K58-/K58.0
5. ICD-10 Data K59.1 – Functional diarrhea
   https://www.icd10data.com/ICD10CM/Codes/K00-K95/K55-K64/K59-/K59.1
6. ICD-10 Data P78.3 – Neonatal diarrhea
   https://www.icd10data.com/ICD10CM/Codes/P00-P96/P75-P78/P78-/P78.3
7. ICD-10 Data F45.8 – Other somatoform disorders
   https://www.icd10data.com/ICD10CM/Codes/F01-F99/F40-F48/F45-/F45.8
8. ICD-10 Data A04 – Bacterial intestinal infections
   https://www.icd10data.com/ICD10CM/Codes/A00-B99/A00-A09/A04-
9. AAPC Coding Resources – Professional coding guidance
   https://www.aapc.com/codes/icd-10-codes/R19.7
10. WHO ICD-10 – International Classification of Diseases
    https://www.who.int/standards/classifications/classification-of-diseases

Current Research Studies

11. Global Burden Study 2024 – Trends in epidemiological characteristics and etiologies of diarrheal disease in children under five
    https://www.sciencedirect.com/science/article/pii/S2949704324000258
12. PMC Global Incidence Analysis – Predictive model for diarrhea incidence 2020-2040
    https://pmc.ncbi.nlm.nih.gov/articles/PMC11434730/
13. CDC Travelers’ Diarrhea Study – Etiology and epidemiology among US military personnel 2018-2023
    https://wwwnc.cdc.gov/eid/article/30/14/24-0308_article
14. Lebanese Hospital Study – Epidemiology of pathogens causing acute diarrhea
    https://journals.lww.com/md-journal/fulltext/2024/03010/epidemiology_of_pathogens_causing_acute_diarrhea.26.aspx
15. NCBI Clinical Reference – Comprehensive diarrhea clinical guidelines
    https://www.ncbi.nlm.nih.gov/books/NBK448082/
16. BMC Public Health Study – African region diarrheal disease analysis
    https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-024-19334-8

Additional Resources

17. Carepatron ICD Codes – Most common ICD codes for diarrhea billing
    https://www.carepatron.com/icd/diarrhea
18. Coverself 2026 Updates – Key changes to ICD-10-CM coding in 2026
    https://www.coverself.com/blog/key-changes-to-icd-10-cm-coding-in-2026
19. AHIMA – American Health Information Management Association
    https://www.ahima.org
20. AHA Coding Clinic – Official coding guidance
    https://www.codingclinicadvisor.com

About the Author

Grace Oluchi Anugwa is a medical graduate from All Saints University School of Medicine, Dominica, where she served as SBC welfare coordinator (2017-2018). She is currently a doctor in training at Cumberland Infirmary Carlisle, England, with aspirations in cardiology. Grace focuses on making medical coding and health education accessible to both healthcare professionals and patients.

Clinical Impact: Rotavirus is the leading pathogen, highlighting the importance of accurate coding for public health surveillance and intervention planning. Proper coding supports both individual patient care and population health monitoring.

Key Takeaway: Diarrhea is a common problem that can have different causes and effects. ICD-10-CM is a system of codes that can help with finding out and treating diarrhea and related problems. ICD-10-CM codes for diarrhea can be used for different purposes, such as writing, talking, finding out, checking, and doing research. But it is important to use the codes correctly and carefully, following the rules and symbols of ICD-10-CM