Intestinal Infections by Cytomegalovirus (ICD-11: 1A24)

1. Introduction

Intestinal infections caused by cytomegalovirus (CMV) represent a significant gastrointestinal manifestation caused by a virus from the Herpesviridae family. Cytomegalovirus is an ubiquitous opportunistic pathogen that remains latent in the body after primary infection and can reactivate in situations of immunosuppression. When it affects the gastrointestinal tract, CMV can cause manifestations ranging from mild to severe complications, including intestinal perforation and gastrointestinal hemorrhage.

The clinical importance of this condition resides mainly in its occurrence in vulnerable populations: patients with HIV/AIDS, solid organ or bone marrow transplant recipients, users of immunosuppressive therapies for autoimmune diseases, and cancer patients undergoing chemotherapy. Although CMV seroprevalence is high in the general population, symptomatic intestinal disease occurs predominantly when there is significant compromise of the immune system.

The impact on public health is considerable, especially in transplant units and specialized centers for treatment of immunocompromised patients. CMV colitis can lead to prolonged hospitalizations, need for emergency surgical interventions, and increased morbidity and mortality. Early diagnosis and appropriate institution of specific antiviral therapy are fundamental to prevent potentially fatal complications.

Correct coding using ICD-11 1A24 is critical for epidemiological monitoring of this condition, allowing identification of trends in different at-risk populations, appropriate allocation of resources for diagnosis and treatment, and evaluation of the effectiveness of preventive strategies. Furthermore, accurate documentation facilitates communication among healthcare professionals and ensures appropriate reimbursement by health systems.

2. Correct ICD-11 Code

Code: 1A24

Description: Intestinal infections caused by cytomegalovirus

Parent category: Viral intestinal infections

Official definition: Disease of the gastrointestinal tract caused by cytomegalovirus infection. This condition is characterized by diarrhea, fever, abdominal pain, or hematochezia. Transmission occurs through direct contact with infected body fluids.

This specific code should be used when there is diagnostic confirmation of intestinal involvement by cytomegalovirus, whether through histopathological methods, endoscopy with biopsy, or viral detection by molecular techniques in gastrointestinal tissue. Code 1A24 encompasses manifestations that include esophagitis, gastritis, enteritis, colitis, and proctitis caused by CMV, provided there is evidence of active infection in the digestive tract.

It is essential to understand that this code should not be used for systemic CMV infection without documented gastrointestinal involvement, nor for asymptomatic seropositivity. The presence of gastrointestinal symptoms combined with laboratory or histological evidence of active CMV infection in the digestive tract is essential for the correct application of this code. Documentation should include the diagnostic method used and the anatomical location of intestinal involvement.

3. When to Use This Code

Code 1A24 should be applied in specific clinical scenarios where there is confirmed cytomegalovirus intestinal infection:

Scenario 1: CMV colitis in renal transplant patient A patient who underwent renal transplantation six months ago, on triple immunosuppressive therapy, presents with bloody diarrhea for two weeks, intermittent fever, and diffuse abdominal pain. Colonoscopy reveals deep ulcers in the descending colon and sigmoid. Biopsy demonstrates cells with characteristic viral inclusions ("owl's eye" cells) and immunohistochemistry confirms CMV antigens. CMV viral load in blood is elevated. This is a typical case for coding as 1A24.

Scenario 2: CMV enteritis in patient with AIDS Patient with HIV/AIDS and CD4+ lymphocyte count below 50 cells/mm³ develops voluminous watery diarrhea, significant weight loss, and colicky abdominal pain. Upper endoscopy with duodenal biopsy demonstrates villous atrophy and presence of viral inclusions compatible with CMV. PCR for CMV in duodenal tissue is positive. This presentation justifies the use of code 1A24.

Scenario 3: Severe CMV colitis in patient with inflammatory bowel disease Patient with ulcerative colitis on prolonged corticosteroid and immunobiologic therapy presents with severe exacerbation with profuse bloody diarrhea, abdominal distension, and signs of systemic toxicity. Emergency colonoscopy shows extensive and deep ulcers. Biopsies reveal CMV infection confirmed by immunohistochemistry. Detection of viral DNA by PCR in colonic tissue is positive. Code 1A24 is appropriate for this case.

Scenario 4: CMV proctitis in post-chemotherapy patient Patient undergoing intensive chemotherapy for acute leukemia develops proctorrhagia, tenesmus, and severe rectal pain. Rectosigmoidoscopy identifies deep ulcers in the rectal mucosa. Biopsy with specific staining demonstrates CMV viral inclusions and qualitative PCR for CMV is positive in tissue. This presentation should be coded as 1A24.

Scenario 5: CMV gastroenteritis in hematopoietic stem cell transplant recipient Patient who underwent allogeneic hematopoietic stem cell transplantation develops nausea, vomiting, epigastric pain, and diarrhea during the period of profound neutropenia. Upper endoscopy reveals gastric and duodenal ulcers. Biopsies show CMV-infected cells confirmed by immunohistochemistry. CMV viremia is detected by antigenemia or quantitative PCR. Code 1A24 is appropriate.

Scenario 6: CMV esophagitis with intestinal extension Immunocompromised patient with dysphagia, odynophagia, and concurrent diarrhea. Upper endoscopy shows extensive esophageal ulcers and also duodenal ulcers. Biopsies from both locations confirm CMV infection. In this case, code 1A24 is appropriate and may be complemented with additional codes if necessary to specify multiple sites of involvement.

4. When NOT to Use This Code

It is essential to recognize situations in which code 1A24 should not be applied:

Asymptomatic CMV seropositivity: Mere detection of IgG antibodies against CMV, indicating prior exposure to the virus, does not justify the use of this code. The majority of the adult population worldwide has antibodies against CMV without ever developing active disease.

CMV viremia without gastrointestinal manifestation: Immunocompromised patients may present with detection of CMV in the blood (by pp65 antigenemia or quantitative PCR) without gastrointestinal symptoms or evidence of intestinal disease. In these cases, codes related to systemic CMV infection should be used, not 1A24.

Gastrointestinal infections by other viral agents: Gastroenteritis caused by rotavirus, norovirus, adenovirus, or astrovirus require specific codes (1A22, 1A20, 1A21, respectively), even if the patient is seropositive for CMV. Identification of the specific etiologic agent is essential.

Extraintestinal manifestations of CMV: CMV retinitis, CMV pneumonitis, CMV encephalitis, or CMV hepatitis should be coded with specific codes for these manifestations, not with 1A24, which is exclusive for gastrointestinal involvement.

Inflammatory bowel disease without CMV infection: Patients with Crohn's disease or ulcerative proctocolitis in active phase, but without evidence of CMV superinfection on biopsies, should receive only codes corresponding to inflammatory bowel diseases.

Nonspecific diarrhea in immunocompromised patient: Not all diarrhea in patients with immunosuppression is caused by CMV. The differential diagnosis includes multiple bacterial, parasitic, fungal, and viral pathogens, in addition to noninfectious causes. Specific confirmation of CMV is mandatory before applying code 1A24.

5. Step-by-Step Coding Process

Step 1: Assess diagnostic criteria

The diagnosis of cytomegalovirus intestinal infection requires the combination of clinical manifestations compatible with laboratory or histopathological evidence of active infection. The essential criteria include:

Clinical manifestations: Presence of gastrointestinal symptoms such as diarrhea (watery or bloody), abdominal pain, fever, nausea, vomiting, hematochezia, or melena. The intensity of symptoms ranges from mild presentations to severe manifestations with intestinal perforation or massive hemorrhage.

Diagnostic confirmation: The gold standard is histopathological demonstration of characteristic viral inclusions in endoscopic biopsies. Infected cells present basophilic intranuclear inclusions surrounded by a clear halo (appearance of "owl's eye"). Immunohistochemistry for CMV antigens increases diagnostic sensitivity. Molecular methods such as PCR for detection of viral DNA in intestinal tissue are also accepted.

Necessary evaluations: Digestive endoscopy (upper or lower, depending on symptom location) with obtaining multiple biopsies, laboratory tests including complete blood count, renal and hepatic function, detection of CMV viremia (pp65 antigenemia or quantitative PCR in blood), and assessment of the patient's immunological status.

Step 2: Verify specifiers

Severity: CMV intestinal infection can be classified as mild (symptoms controlled on an outpatient basis), moderate (requiring hospitalization), or severe (complications such as perforation, massive hemorrhage, or toxic megacolon).

Anatomical location: Documenting the affected intestinal segment (esophagus, stomach, duodenum, jejunum, ileum, colon, rectum) is important for therapeutic planning, although code 1A24 encompasses all locations.

Duration: Distinguish between acute infection (primary or recent reactivation) and chronic or recurrent infection, especially in patients with maintained immunosuppression.

Clinical context: Identifying the predisposing factor (organ transplantation, HIV/AIDS, immunosuppressive therapy, inflammatory bowel disease, chemotherapy) is relevant for prognosis and treatment.

Step 3: Differentiate from other codes

1A20 - Adenovirus Enteritis: Differentiation is based on identification of the etiological agent. Adenovirus causes gastroenteritis mainly in children and immunocompromised patients, but the clinical presentation may be similar. Differential diagnosis requires specific detection of adenovirus by PCR, viral culture, or immunofluorescence in stool or intestinal tissue, whereas CMV is identified by characteristic viral inclusions in biopsies or tissue PCR.

1A21 - Astrovirus Gastroenteritis: Astrovirus causes self-limited watery gastroenteritis, more common in children and elderly patients. The main difference lies in the etiological agent identified by specific stool tests. Astrovirus rarely causes invasive disease with deep ulcers, unlike CMV which frequently presents with ulcerated lesions on endoscopy.

1A22 - Rotavirus Gastroenteritis: Rotavirus is a common cause of acute gastroenteritis in infants and children, characterized by profuse watery diarrhea, vomiting, and dehydration. Detection of rotavirus in stool by rapid antigen tests or PCR differentiates from this condition. CMV, on the other hand, occurs predominantly in immunocompromised adults with characteristic endoscopic and histological findings.

Step 4: Necessary documentation

Checklist of mandatory information:

Detailed description of gastrointestinal symptoms and their duration
Patient's immunological status and predisposing factors
Results of endoscopic examinations with macroscopic description of lesions
Anatomopathological report of biopsies with identification of viral inclusions or positive immunohistochemistry for CMV
Results of PCR for CMV in intestinal tissue, if performed
Results of CMV viremia (antigenemia or quantitative PCR in blood)
Exclusion of other infectious agents through cultures, parasite research, and specific viral tests
Treatment instituted (specific antiviral, adjustment of immunosuppression)

Appropriate documentation: The documentation should clearly specify that it is cytomegalovirus intestinal infection, mentioning the diagnostic method used and the anatomical location. For example: "Cytomegalovirus colitis confirmed by colonoscopic biopsy with positive immunohistochemistry, in a renal transplant patient".

6. Complete Practical Example

Clinical Case

A 45-year-old patient, liver transplant recipient 18 months ago due to cirrhosis from hepatitis C, on immunosuppressive therapy with tacrolimus, mycophenolate, and low-dose prednisone. Presents to the emergency department with bloody diarrhea for 10 days, initially with three daily bowel movements, progressing to eight to ten liquid evacuations with bright red blood in the last 48 hours. Reports diffuse abdominal pain of colic type, intermittent fever (up to 38.5°C), and weight loss of 4 kg during this period.

On physical examination, the patient appears pale and dehydrated, with heart rate of 110 bpm and blood pressure of 100/60 mmHg. The abdomen is slightly distended, diffusely tender on palpation, without signs of peritoneal irritation. Laboratory tests show hemoglobin of 9.2 g/dL (previous 13.5 g/dL), white blood cells 3,200/mm³, platelets 145,000/mm³, creatinine 1.8 mg/dL (baseline 1.1 mg/dL), elevated C-reactive protein.

Urgent colonoscopy was requested, which revealed diffusely edematous and friable colonic mucosa, with multiple deep ulcers with irregular borders, some confluent, distributed from the cecum to the rectum, with areas of necrosis and fibrin. Multiple biopsies were collected from the ulcers and adjacent mucosa.

Histopathological examination demonstrated mucosal ulceration with mixed inflammatory infiltrate, necrosis, and crucially, increased endothelial and stromal cells with basophilic intranuclear inclusions surrounded by a clear halo, characteristic of cytomegalovirus infection. Immunohistochemistry for CMV was strongly positive. PCR for CMV in colonic tissue detected high viral load. Quantitative PCR for CMV in blood was also positive with 15,000 copies/mL.

Other infectious causes were excluded through negative stool cultures, negative Clostridium difficile toxin testing, and negative parasite screening. The patient was admitted and started on intravenous ganciclovir, with reduction of immunosuppression (temporary discontinuation of mycophenolate).

Coding Step by Step

Criteria analysis:

Presence of characteristic gastrointestinal symptoms: bloody diarrhea, fever, abdominal pain
Immunocompromised patient (transplant recipient on immunosuppression)
Compatible endoscopic findings: deep ulcers in colon
Histopathological confirmation: characteristic viral inclusions on biopsies
Confirmation by immunohistochemistry: positive for CMV antigens
Molecular confirmation: positive PCR for CMV in intestinal tissue
CMV viremia detected
Exclusion of other infectious agents

Code selected: 1A24 - Intestinal infections due to cytomegalovirus

Complete justification: Code 1A24 is the most appropriate because the patient presents with documented cytomegalovirus infection of the gastrointestinal tract. All diagnostic criteria were met: compatible clinical manifestations, histopathological confirmation with visualization of characteristic viral inclusions, confirmation by immunohistochemistry, and molecular detection of the virus in intestinal tissue. The anatomical location (colitis) is included in the definition of code 1A24. The context of post-transplant immunosuppression is the typical predisposing factor for this condition.

Applicable complementary codes:

Code for prior liver transplant (history)
Code for secondary anemia (if necessary to specify complication)
Code for acute kidney injury (if necessary to specify complication)

Documentation should record: "Severe cytomegalovirus colitis (ICD-11: 1A24) confirmed by colonoscopy with biopsies showing viral inclusions and positive immunohistochemistry, in a liver transplant patient on immunosuppression."

7. Related Codes and Differentiation

Within the Same Category

1A20: Adenovirus Enteritis

When to use 1A20: Use this code when there is confirmation of intestinal adenovirus infection, identified through PCR in stool or intestinal tissue, viral culture, or immunofluorescence. Enteric adenovirus (serotypes 40 and 41) causes watery diarrhea in children, while other serotypes may cause disease in immunocompromised individuals.
Main difference vs. 1A24: The distinction is based on the identified etiologic agent. Adenovirus is detected by specific methods different from those used for CMV. Histologically, viral inclusions of adenovirus are different from those of CMV. Adenovirus rarely causes deep ulcers like CMV.

1A21: Astrovirus Gastroenteritis

When to use 1A21: Apply this code when astrovirus is identified as the causative agent of gastroenteritis, usually through PCR in stool or electron microscopy. Astrovirus causes mild to moderate gastroenteritis, primarily in children, elderly, and immunocompromised individuals.
Main difference vs. 1A24: Astrovirus causes self-limited disease with watery diarrhea, without significant ulcerative lesions on endoscopy. CMV, in contrast, frequently presents with deep ulcers visible on endoscopy. Astrovirus diagnosis is made by stool tests, while CMV requires tissue biopsy.

1A22: Rotavirus Gastroenteritis

When to use 1A22: Use this code when rotavirus is identified as the cause of acute gastroenteritis, typically through rapid antigen testing in stool or PCR. Rotavirus is the leading cause of severe gastroenteritis in infants and children, characterized by profuse watery diarrhea and dehydration.
Main difference vs. 1A24: Rotavirus predominantly affects immunocompetent pediatric populations, while intestinal CMV occurs mainly in immunocompromised adults. Rotavirus does not cause deep ulcerative lesions. Rotavirus diagnosis is non-invasive (stool testing), while intestinal CMV usually requires endoscopy with biopsy.

Differential Diagnoses

Inflammatory bowel disease (Crohn's disease or Ulcerative colitis): May present with similar symptoms including bloody diarrhea and colonoscopic ulcers. Distinction is made by the absence of viral inclusions on biopsies and by the clinical history of prior inflammatory disease. It is important to note that patients with inflammatory bowel disease may develop CMV superinfection, a situation in which both codes may be applied.

Pseudomembranous colitis due to Clostridium difficile: Presents with watery or bloody diarrhea in hospitalized patients or those on antibiotics. Differentiation is made by detection of C. difficile toxins in stool and colonoscopic findings of pseudomembranes. CMV shows characteristic viral inclusions on biopsies.

Ischemic colitis: May present with abdominal pain and bloody diarrhea, especially in elderly patients with cardiovascular risk factors. Colonoscopy shows typical segmental involvement pattern (watershed areas). There are no viral inclusions on biopsies and the clinical context is different.

Other opportunistic intestinal infections: In immunocompromised patients, consider cryptosporidiosis, microsporidiosis, Mycobacterium avium complex infection. Differentiation requires specific testing for each pathogen.

8. Differences with ICD-10

In the International Classification of Diseases - 10th Revision (ICD-10), intestinal infection by cytomegalovirus does not have a specific code within the chapter of infectious intestinal diseases. Typically, it was coded as B25.8 (Other cytomegalovirus diseases) or, less specifically, as A08.8 (Other specified viral intestinal infections), depending on the emphasis the coder wished to place on the etiologic agent versus the anatomical location.

The main change in ICD-11 is the creation of the specific code 1A24 exclusively for cytomegalovirus intestinal infections, providing greater granularity and precision in coding. This specificity allows better epidemiological tracking of this particular condition, which has significant clinical importance in immunocompromised populations.

The practical impact of these changes is substantial for epidemiological surveillance systems, clinical research, and hospital management. With a specific code, it becomes possible to precisely identify the incidence of CMV colitis in different populations, evaluate specific clinical outcomes of this condition, and allocate adequate resources for its diagnosis and treatment. Furthermore, it facilitates medical audit and appropriate reimbursement by health systems, since intestinal infection by CMV frequently requires prolonged hospitalization, high-cost specific antiviral therapy, and intensive monitoring.

For professionals accustomed to coding in ICD-10, it is important to adapt to the new structure, using code 1A24 whenever there is confirmation of intestinal infection by CMV, abandoning the practice of using generic or nonspecific codes for this condition.

9. Frequently Asked Questions

How is the diagnosis of cytomegalovirus intestinal infection made?

The diagnosis requires a combination of clinical suspicion with laboratory confirmation. Clinically, one should suspect in immunocompromised patients with persistent diarrhea, abdominal pain, fever, or gastrointestinal bleeding. Confirmation is made through digestive endoscopy (upper or lower, depending on symptoms) with biopsy sampling. Histopathological examination seeks to identify cells with characteristic viral inclusions (enlarged nucleus with basophilic inclusion surrounded by clear halo). Immunohistochemistry for CMV antigens increases diagnostic sensitivity. Molecular methods such as PCR for detection of viral DNA in intestinal tissue are also used. Detection of CMV viremia in blood (pp65 antigenemia or quantitative PCR) is complementary but does not replace tissue confirmation, as viremia can occur without intestinal disease.

Is treatment available in public health systems?

Treatment of cytomegalovirus intestinal infection is based on specific antivirals, mainly intravenous ganciclovir or its oral prodrug valganciclovir. These medications are available in many public health systems around the world, especially in transplant centers and hospitals serving immunocompromised patients. However, availability may vary depending on the country and the structure of the local health system. In some locations, these medications may be restricted to specific protocols or require special authorization due to high cost. Foscarnet is an alternative for resistant cases or ganciclovir intolerance, but also has variable availability. Patients should consult their physicians about options available in their region.

How long does treatment last?

The duration of treatment for CMV intestinal infection varies depending on disease severity, clinical response, and the degree of immunosuppression of the patient. Typically, induction treatment with intravenous ganciclovir lasts 3 to 6 weeks, until symptom resolution and viremia negativization. In severe cases or with slow response, longer treatment may be necessary. After the induction phase, some patients may require maintenance therapy with oral valganciclovir, especially if immunosuppression cannot be reduced. Treatment response is monitored through clinical improvement, reduction of viral load in blood, and in some cases, follow-up endoscopy. The decision regarding treatment duration should be individualized by the attending physician.

Can this code be used in medical certificates?

Yes, code 1A24 can and should be used in medical certificates when appropriate. In certificates for work leave or justification of absences, it is appropriate to mention "cytomegalovirus intestinal infection" or simply "severe viral intestinal infection," depending on the level of detail desired by the patient, always respecting medical confidentiality. The ICD-11 code 1A24 can be included for official documentation purposes. It is important to note that this is a condition that frequently requires hospitalization and prolonged absence from usual activities, justifying certificates of duration compatible with the severity of the condition and the time necessary for recovery.

Are patients with HIV/AIDS more prone to developing this condition?

Yes, patients with HIV/AIDS, especially those with advanced immunosuppression (CD4+ lymphocyte count below 50-100 cells/mm³), have significantly elevated risk of developing cytomegalovirus intestinal infection. Before the era of highly effective antiretroviral therapy, CMV colitis was a common and serious complication in patients with advanced AIDS. With the advent of effective HIV treatments, incidence has substantially decreased in patients with good adherence to antiretroviral therapy and immune reconstitution. However, it still occurs in patients with late HIV diagnosis, treatment failure, or poor treatment adherence. CMV prophylaxis is generally not routinely recommended, with the best preventive strategy being adequate control of HIV infection with maintenance of elevated CD4+ counts.

Is there risk of transmission to other people?

Cytomegalovirus is transmitted through direct contact with infected body fluids, including saliva, urine, blood, tears, semen, and breast milk. In the context of CMV intestinal infection, the virus may be present in gastrointestinal secretions. However, transmission from a patient with CMV colitis to other immunocompetent people is unlikely in everyday situations. The greatest risk of transmission occurs in healthcare settings, through exposure to blood or body secretions, which is why standard precautions should be followed by healthcare professionals. Household contacts of patients with active CMV infection do not require special precautions beyond basic hand hygiene. Pregnant women who are contacts of patients with active CMV should be counseled about rigorous hygiene measures, as primary CMV infection during pregnancy can have consequences for the fetus.

Is it possible to have recurrence of infection after treatment?

Yes, recurrence of cytomegalovirus intestinal infection is possible, especially in patients who maintain significant immunosuppression. CMV remains latent in the body after primary infection and can reactivate when there is immunological compromise. In transplant patients who need to maintain continuous immunosuppression, or in patients with HIV/AIDS without adequate virological control, reactivation can occur even after successful treatment. To minimize the risk of recurrence, it is essential to optimize control of the underlying condition (adjustment of immunosuppression when possible, adequate HIV control), complete the full course of antiviral therapy, and maintain regular monitoring. Some high-risk patients may require prolonged suppressive therapy with oral valganciclovir.

What are the possible complications of this infection?

Cytomegalovirus intestinal infection can lead to serious complications, some potentially fatal. The main ones include: intestinal perforation (rupture of the intestinal wall due to deep ulcers, requiring emergency surgery), massive gastrointestinal hemorrhage (intense bleeding from ulcers, potentially requiring transfusions and endoscopic or surgical intervention), toxic megacolon (extreme colon dilation with risk of perforation), intestinal stenosis (narrowing of the intestine as a sequel of scarred ulcers), sepsis (generalized infection), and severe malnutrition due to prolonged malabsorption. Additionally, CMV infection can disseminate to other organs, causing retinitis (with risk of blindness), pneumonitis, encephalitis, or hepatitis. Early recognition and appropriate treatment are essential to prevent these complications and reduce mortality associated with this condition.

Conclusion

Cytomegalovirus intestinal infection, coded as 1A24 in ICD-11, is a serious condition that primarily affects immunocompromised patients. Accurate coding is fundamental for appropriate management, epidemiological surveillance, and resource allocation. Healthcare professionals should be alert to diagnostic criteria, differentiation from other viral intestinal infections, and appropriate documentation to ensure correct application of this code. Early diagnosis and appropriate treatment with specific antivirals are essential to prevent potentially fatal complications and improve clinical outcomes in these patients.

External References

This article was prepared based on reliable scientific sources:

References verified on 2026-02-04

Intestinal Infections by Cytomegalovirus

Partager