December 9, 2025
Symptoms of PRES: Diagnosis, Treatment, and ICD-10-CM Coding Guidance
December 9, 2025
Introduction to PRES Symptoms, Causes, and Coding
Posterior Reversible Encephalopathy Syndrome (PRES), also known in clinical literature as reversible posterior leukoencephalopathy syndrome, is a neurologic condition characterized by acute changes in mental status, seizures, headaches, and visual disturbances. Because the symptoms of PRES can overlap with other encephalopathic presentations, accurate documentation is essential for correct ICD-10-CM coding, DRG assignment, severity capture, and CDI review.
What Is PRES? Understanding the Medical Term and Clinical Features
PRES is a clinical radiographic syndrome defined by a constellation of neurologic symptoms and characteristic imaging findings. Alternate terminology includes:
- Reversible posterior leukoencephalopathy syndrome (RPLS)
- Reversible posterior cerebral edema syndrome
- Hyperperfusion encephalopathy
- Brain capillary leak syndrome
Common clinical presentations include:
- Headache
- Seizures
- Altered mental status or confusion
- Visual disturbances (blurred vision, cortical blindness, visual field loss)
Clinical settings commonly associated with PRES include hypertensive crisis, cytotoxic immunosuppressive therapy, pre-eclampsia/eclampsia, and other conditions that cause endothelial injury.
Imaging Findings That Support a Diagnosis of PRES
Neuroimaging, particularly MRI, typically shows:
- Vasogenic edema
- Predominant involvement of posterior cerebral regions
- Symmetric white matter changes
These imaging features are foundational in differentiating PRES from other encephalopathies.
Treatment of PRES and Key Management Principles
The treatment of PRES focuses on addressing the underlying cause and preventing further neurologic injury. Management strategies include:
- Tight blood pressure control
- Discontinuation of offending agents (especially cytotoxic medications)
- Seizure management
- Obstetric protocols when PRES occurs during pregnancy (treated as pre-eclampsia or eclampsia)
Most patients recover within two weeks; however, some may experience persistent neurologic deficits or, in severe cases, complications such as intracranial hemorrhage or cerebral infarction.
ICD-10-CM Coding for PRES (I67.83) and CDI Considerations
The ICD-10-CM code for PRES is I67.83.
Key coding and CDI notes:
- PRES is classified as an MCC when assigned as a secondary diagnosis.
- When PRES is the principal diagnosis, it groups to MS-DRG 070, 071, or 072 (Other cerebrovascular disorders).
- Cerebral edema is not coded separately, as it is inherent to PRES.
- PRES is a recognized risk-adjusting condition demonstrating severity of illness.
- Documentation must clearly link PRES to the underlying cause when clinically supported.
- Documentation of “encephalopathy” alone does not support coding PRES; a CDI query is indicated if the diagnosis is unclear or inconsistently documented.
Secondary Diagnoses That Impact DRG and Severity Capture
When reviewing documentation, CDI specialists should assess for commonly associated secondary diagnoses, including:
- Acidosis
- Acute renal failure
- Coma
- Cerebral infarction or stroke
- ESRD
- Secondary hyperparathyroidism
These conditions may significantly impact DRG assignment and severity reporting.
Query Opportunities for PRES Documentation
A CDI query may be appropriate when:
- “Encephalopathy” is documented without clarification of the type
- Imaging findings are consistent with PRES but the provider does not document the diagnosis
- The underlying cause (e.g., hypertensive crisis, cytotoxic drug use, pre-eclampsia) is not explicitly linked to PRES
- Conflicting terminology appears in the record
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Alyce Reavis, RN,MSN,CCDS,CCS
Senior CDI Educator, Consulting Services at UASI
Drawing on clinical experience in adult, pediatric, and neonatal acute care, Alyce brings valuable insight to CDI education and documentation improvement. She holds an MSN in Leadership/Education along with CCDS, CCS, and AHIMA’s outpatient CDI micro credential, supporting health systems in strengthening documentation accuracy, quality reporting, and reimbursement integrity. Passionate about truthful, clinically aligned health records, she helps organizations ensure documentation reflects true patient acuity. She is a past presenter for the ACDIS National Convention, Local chapter meetings, and the ACDIS Virtual Best Practices conference.
Works Cited
Centers for Medicare & Medicaid Services. (2025). FY 2026 Official Guidelines for Coding and Reporting.
Available at
https://www.cms.gov
Centers for Medicare & Medicaid Services. (2025). IPPS Final Rule for Fiscal Year 2026.
Available at
https://www.cms.gov
Neill, T. (2025). Posterior reversible encephalopathy syndrome. UpToDate.
Available at
https://www.uptodate.com/contents/posterior-reversible-encephalopathy-syndrome
Understand ICANS documentation and ICD-10 coding with guidance on the ICANS grading system, ICE score, clinical indicators, and CAR T-cell neurotoxicity.
Gestational Diabetes definition : Any pregnant person that shows abnormal glucose tolerance that was not present prior to the pregnancy. The American College of Obstetricians and Gynecologists (ACOG) define GDM as "a condition in which carbohydrate intolerance develops during pregnancy.” Preexisting (pregestational) diabetes refers to type 1 or 2 diabetes diagnosed before pregnancy. Common Risk Factors: GDM in a prior pregnancy Family history of diabetes Pre-pregnancy BMI ≥30 kg/m2, significant weight gain in early adulthood or between pregnancies, or excessive gestational weight gain during the first 18 to 24 weeks of pregnancy Maternal age >/=35 years of age Key Points for Accurate Documentation Specify Diagnosis Clearly Use the term “Gestational Diabetes Mellitus (GDM)” and indicate if it is diet-controlled (A1) or insulin/medication-controlled (A2). Avoid vague terms like “borderline diabetes” or “glucose intolerance.” Document Diagnostic Basis Include OGTT results or note that diagnosis was based on ADA/ACOG criteria (e.g., abnormal 1-hour or 3-hour glucose tolerance test). Capture Clinical Significance Note any maternal or fetal complications (e.g., polyhydramnios, macrosomia, preeclampsia). Document treatment plan: diet modification, insulin, oral agents, or glucose monitoring. Differentiate from Pre-existing Diabetes Confirm that hyperglycemia was first recognized during pregnancy. If diabetes existed before pregnancy, code as pre-gestational diabetes. Postpartum Follow-up Indicate if postpartum glucose testing or counseling for future diabetes risk was provided. Why It Matters: Precise documentation supports accurate ICD-10 coding (e.g., O24.41–O24.43), reflects severity of illness, and impacts quality metrics and reimbursement. AHRQ’s Maternity Care Measure Set includes post-partum glucose careening for gestational diabetes patients in Measure 10 – Post-Partum Follow-up and Care Coordination. This measure applies to all patients regardless of age, who gave birth during a 12-month period seen for post-partum care visit before or at 8-weeks of giving birth. There are no exceptions. References: ACOG/National Committee or Quality Assurance. (2012). Maternity Care Performance Measures Set. Maternity Care Performance Measurement Set American College of Obstetricians and Gynecologists. (2018). Gestational Diabetes Mellitus. Practice Bulletin Number 190. Gestational Diabetes Mellitus | ACOG Centers for Medicare and Medicaid Services. (2025). Official Guidelines for Coding and Reporting. ICD-10-CM October 2025 FY26Guidelines Diabetes Care 2025;48(Supplement_1):S306–S320 https://doi.org/10.2337/dc25-S015 Durnwald, C. (2025). Gestational diabetes mellitus: Screening, diagnosis, and prevention. UpToDate.
Definition : Acute Kidney Injury (AKI) is an abrupt decline in kidney function, leading to retention of waste products, electrolyte imbalance, and fluid dysregulation. It is classified based on etiology and severity. 1. Types of AKI by Etiology Pre-Renal AKI Cause: Decreased renal perfusion without intrinsic kidney damage. Examples: Hypovolemia (dehydration, hemorrhage). Hypotension/shock (sepsis, cardiogenic shock) Heart failure, liver failure Documentation Tip: Specify underlying cause (e.g., “AKI due to hypovolemia from GI bleed”). Intrinsic (Intra-Renal) AKI Cause: Direct damage to kidney tissue. Examples: Acute Tubular Necrosis (ATN\) – ischemia or nephrotoxins Acute Interstitial Nephritis (AIN) – drug-induced, autoimmune Glomerulonephritis Documentation Tip: If ATN or AIN is suspected, document specifically (e.g., “AKI secondary to ATN from contrast exposure”). Post-Renal AKI Cause: Obstruction of urine flow. Examples: Ureteral obstruction (stones, tumors) Bladder outlet obstruction (BPH, neurogenic bladder) Documentation Tip: State the obstructive cause (e.g., “AKI due to bilateral ureteral obstruction from stones”). 2. Diagnostic Criteria (KDIGO) Increase in serum creatinine by ≥ 0.3 mg/dL within 48 hrs, OR Increase in serum creatinine to ≥ 1.5 times baseline within 7 days, OR Urine output < 0.5 mL/kg/hr for 6 hrs 3. Severity Staging Stage 1: 1.5–1.9 × baseline creatinine or ≥ 0.3 mg/dL rise Stage 2: 2.0–2.9 × baseline Stage 3: ≥ 3 × baseline or creatinine ≥ 4.0 mg/dL or dialysis required 4. CDI and Current Coding Guidance Avoid vague terms like “renal insufficiency”; use “acute kidney injury” or “acute renal failure” (interchangeable per coding). Always link AKI to the underlying cause (e.g., sepsis, dehydration, obstruction). If ATN or AIN are present, document explicitly (these are MCCs). Do not abbreviate AKI without context; clarify in the first mention. Trend labs and urine output to support diagnosis before querying. Assign code N17.0, Acute kidney failure with tubular necrosis, with a POA of N for documentation of a patient with AKI on admission who then develops ATN after admission. For a case of acute kidney injury (AKI) due to acute tubular necrosis (ATN) secondary to contrast-induced nephropathy, the correct coding assignment is N17.0 for acute kidney failure with tubular necrosis, N14.11 for contrast-induced nephropathy, and T50.8X5A for adverse effect of diagnostic agents, initial encounter. This combination accurately reflects the underlying cause, the specific kidney injury type, and the adverse effect of the contrast agent. Pro Tip: AKI impacts severity of illness and quality metrics (e.g., PSI-10 Post-Op AKI). Accurate documentation ensures correct DRG assignment and patient safety. References: AHA Coding Clinic, Third Quarter 2025, p. 22 AHA Coding Clinic, Fourth Quarter 2022, p. 33 Centers for Medicare and Medicaid Services. (2025). Official Guidelines for Coding and Reporting. www.cms.gov. Fatehi, P., & Hsu, C-Y. (2024). Evaluation of acute kidney injury among hospitalized adult patients. UpToDate. Palevsky, P. M. (2025). Definition and staging criteria of acute kidney injury in adults. UpToDate. Prescott, L., Manz, J. (2025). The ACDIS Inpatient CDI Pocket Guide. www.acdis.org
CDI Tip: Capturing Firearm Injury Intent from Other Clinicians’ Documentation What’s New in FY 2026? CMS and ICD-10-CM guidelines now allow documentation by clinicians other than the patient’s provider (e.g., nurses, social workers, trauma team) to be used for assigning external cause codes, including firearm injury intent. This change supports more accurate public health reporting and injury surveillance Key Actions for CDI Specialists Review All Clinical Notes Check ED notes, nursing assessments, social work documentation, and EMS reports for statements about firearm injury intent (e.g., accidental, assault, self-harm, undetermined). Apply the New Intent Hierarchy If intent is clearly documented by any clinician, code accordingly: Accidental: W34 series Assault: X93–X95 series Self-harm: X72–X74 series Undetermined: Y22–Y24 series If no intent is documented, follow the updated guideline: default to undetermined intent for firearm injuries (Y24.9), unless otherwise specified. Query When Needed If conflicting documentation exists (e.g., ED note states “possible assault,” nursing note says “accidental”), query the provider for clarification. Document Source When coding based on another clinician’s note, ensure the documentation is clearly attributed in the record. Pro Tip: Incorporate firearm injury intent review into your trauma and ED CDI workflows. Educate providers that intent matters for coding, quality metrics, and injury prevention programs. Example Clinical Scenario with Query: Setting: ED, trauma bay Patient: 28-year-old male with a through and through gunshot wound of the left thigh; hemodynamically stable. Documentation in record: ED triage RN note: “Pt states he was shot by someone outside a bar.” EMS run sheet: “Bystanders report drive by shooting; single GSW to L thigh.” ED SW note: “Patient reports unknown assailant; denies self-harm.” ED provider note: “GSW L thigh; hemorrhage controlled; analgesia given.” Intent not specified in provider note or discharge summary Query: Documentation in the medical record shows that the patient was injured by a firearm. Please clarify the intent of the firearm injury for this encounter, based on your clinical judgment and the medical record. Assault (injury inflicted by another person) Accidental/unintentional Intentional self-harm Undetermined (unable to determine intent from available information) Other (please specify): _______________________
What is ventricular standstill? SA node is functioning, and P waves are present on EKG. There is no ventricular response, no contractions of the muscle. The presence of complete heart block with no escape rhythm. No cardiac output with the patient in full arrest. May be paroxysmal or prolonged.
What does it mean when “neurostorming” is documented? “Neuro storm” and other similar terms such as autonomic storms, hypothalamic dysregulation syndrome and sympathetic storms all equate to the condition paroxysmal sympathetic hyperactivity (PSH). This syndrome was formally named in 2014 by an international panel looking at preferred nomenclature, definition and diagnostic criteria. PSH is defined as a disorder in the regulation of autonomic function most observed in patients with acute brain injury, most notably severe traumatic brain injury. What are the risk factors for PSH? Traumatic brain injury (TBI) Hypoxic ischemic injury What are the clinical indicators of PSH? Sinus tachycardia Elevated systolic blood pressure Tachypnea associated with respiratory alkalosis Diaphoresis that can progress to dehydration Hyperthermia in some cases Severe cases may have dystonic posturing How is PSH treated? Reducing stimulation Managing hyperthermia and hyperventilation Medications IV Morphine Gabapentin Beta blockers Baclofen Precedex infusion Dantrolene Coding and CDI considerations for the documentation of “neurostorming” The ICD-10-CM condition code most appropriate for reporting of PSH is G90.89, Other disorders of autonomic nervous system. There is no specific code to identify neurostorm or PSH. There are also no instructional notes for the code G90.89. Per the ICD10-CM Official Coding Guidelines, “ If a main term cannot be located, consider a synonym, an eponym, or another alternative term. Once the main term is located, search for subterms, notes, or cross-references. Subterms provide many types of more specific information and must be checked carefully, following all the rules of alphabetization. The main term code entry should not be assigned until all subterm possibilities have been exhausted. During this process, it may be necessary to refer again to the medical record to determine whether any additional information is available to permit assignment of a more specific code. If a subterm cannot be located, the nonessential modifiers following the main term should be reviewed to see whether the subterm may be included there. If not, alternative terms should be considered” Current coding advice notes that when the index is confusing, leading to an inappropriate code, further research is needed when the title of the code suggested by the index clearly does not identify the condition correctly. Regarding the CDI professional, it is allowable to report code G90.89, Other disorders of autonomic nervous system in the instance where “neurostorm” is documented by the provider. A query would not be needed for clarification. References: American Hospital Association (AHA). ICD-10-CM Coding Clinic, Second Quarter 2025, p. 4. Available from: AHA Coding Clinic Centers for Medicare & Medicaid Services (CMS). (2025). ICD-10-CM Official Guidelines for Coding and Reporting. Available from: CMS ICD-10-CM Guidelines Rabinstein, A. (2024). Paroxysmal sympathetic hyperactivity. UpToDate. Available from: UpToDate – Paroxysmal sympathetic hyperactivity
Background: With the 2026 IPPS Proposed Final Rule comes a new diabetes code, E11.A, Type II diabetes mellitus without complications in remission. This is a non-CC/MCC and is assigned to MDC 10. ICD-10-CM Official Guidelines for Coding and Reporting 2026: Section I.C.4.a.1.(b) - “Code E11.A, Type 2 diabetes mellitus without complications in remission, is assigned based on provider documentation that the diabetes mellitus is in remission. If the documentation is unclear as to whether the Type 2 diabetes mellitus has achieved remission, the provider should be queried. For example, the term “resolved” is not synonymous with remission.” Clinical criteria for diabetes in remission: Note* - Remission does not mean cure. Ongoing monitoring is essential as relapse is possible. 1. Prior Diagnosis of Diabetes Mellitus Documented history of type 2 diabetes mellitus, diagnosed using standard criteria: HbA1c ≥ 6.5% Fasting plasma glucose ≥ 126 mg/dL 2-hour plasma glucose ≥ 200 mg/dL during an OGTT Random plasma glucose ≥ 200 mg/dL with classic symptoms 2. Normal or Controlled Glucose Levels Without Medications The patient is not taking any antidiabetic medications (oral agents, insulin, or non-insulin injectables). Glycemic control is sustained through lifestyle modifications, such as diet and exercise. HbA1c < 6.5%, and sometimes < 6.0%, on two occasions at least 6 months apart without pharmacologic therapy. 3. Duration of Remission Partial remission: HbA1c < 6.5% and fasting glucose 100–125 mg/dL for at least 1 year without medications. Complete remission: HbA1c in the normal range (<5.7%) and fasting glucose <100 mg/dL for at least 1 year. Prolonged remission: Complete remission lasting ≥5 years. 4. Documentation Must Include Clear statement that diabetes is in remission or resolution. No current use of diabetes medications. Current HbA1c values. Lifestyle interventions being used. Absence of ongoing diabetic complications (or if present, they are noted as sequelae) 5. What about Type I diabetes? Is remission associated? “Honeymoon Phase” vs. Remission Some individuals newly diagnosed with type 1 diabetes may experience a "honeymoon phase": This is a temporary period (weeks to months) where insulin needs to decrease and blood glucose levels may normalize. However, this is not true remission, as the autoimmune process continues and insulin dependence eventually returns. Clinical Scenario Dr. Doctor, Documentation in your visit note indicates the patient has a documented history of type 2 diabetes mellitus, but current labs show: HbA1c: 5.6% No diabetes medications (e.g., insulin, metformin) currently prescribed Patient reports lifestyle changes (e.g., diet and weight loss) No hyperglycemia documented during this admission or recent visits Query Based on the clinical picture, can you please clarify the patient’s current diabetic status? ☐ Type 2 diabetes mellitus – continue to document and treat as active ☐ History of type 2 diabetes mellitus, currently in remission (no medications, normal glucose values) ☐ Other: ________________
Definition: Neonatal encephalopathy (NE) is a clinically defined syndrome of disturbed neurologic function in the earliest days of life in a term or late preterm infant, manifested by difficulty with initiating and maintaining respiration, depression of tone and reflexes, subnormal level of consciousness, and often seizures. Clinical presentation: Low APGAR scores and/or weak/absent cry in the delivery room. Hyperalert, irritable, lethargic, obtunded. Decreased spontaneous movements, poor tone, blunted or absent primitive reflexes, seizure activity. Breathing and/or feeding difficulties. Documentation Tips: The CDS should review to identify the underlying etiology . (e.g., hypoxic-ischemic event, infection, metabolic disorder). Review clinical indicators that may indicate associated conditions , such as seizures, abnormal imaging, acidosis, or multi-organ dysfunction. Review the documentation for the timing of onset (e.g., at birth, delayed). Common clinical indicators include low APGAR scores, need for resuscitation, abnormal tone, or altered level of consciousness. ICD-10-CM Coding: P91.811, Neonatal encephalopathy in diseases classified elsewhere P91.819, Neonatal encephalopathy, unspecified Use when the type or etiology of NE is not documented Query Example: To the Attending Neonatologist: Documentation in the medical record indicates the newborn infant delivered from mother with placental abruption demonstrates seizures, abnormal muscle tone, low APGAR scores, and required resuscitation at birth. Imaging showed evidence of cerebral edema. The diagnosis of “neonatal encephalopathy” was documented in the assessment. Query: Based on the clinical indicators, can you clarify the type and cause of the encephalopathy in this newborn? Please select the most appropriate option below or specify another diagnosis: Neonatal encephalopathy due to Hypoxic-ischemic encephalopathy (HIE) Neonatal encephalopathy due to other etiology (please specify) Other (please specify): __________
Definition: Tumor lysis syndrome (TLS) is an oncologic emergency caused by massive tumor cell lysis and the release of large amounts of potassium, phosphate, and uric acid into the systemic circulation. Deposition of uric acid and/or calcium phosphate crystals in the renal tubules can result in acute kidney injury.
Syndrome of Inappropriate Antidiuretic Hormone (SIADH) occurs when the pituitary gland releases excessive antidiuretic hormone (ADH) , leading the body to retain fluid and dilute sodium levels in the bloodstream. This condition causes hyponatremia and hypo-osmolality , often triggering a complex clinical picture. What Causes SIADH? SIADH can develop in response to several underlying conditions or external factors: CNS disturbances: Stroke, hemorrhage, infection, and trauma can trigger abnormal ADH release. Cancer: Especially small cell lung cancer, extrapulmonary small cell carcinomas, head and neck cancers, and olfactory neuroblastomas. Medications: SSRIs, NSAIDs, opiates, some antineoplastic drugs, ciprofloxacin, haloperidol, and high-dose imatinib. Surgery: Often linked to pain response. Hormonal deficiencies: Including hypothyroidism and hypopituitarism. Exogenous hormone use: Vasopressin, desmopressin, and oxytocin. HIV infection Hereditary SIADH Diagnostic Criteria: Schwartz and Bartter Clinical Framework A diagnosis of SIADH typically includes: Serum sodium < 135 mEq/L Serum osmolality < 275 mOsm/kg Urine sodium > 40 mEq/L Urine osmolality > 100 mOsm/kg Normal skin turgor and blood pressure (absence of clinical volume depletion) Exclusion of other hyponatremia causes Correction of sodium levels via fluid restriction Important Note: Code only the SIADH, not the hyponatremia, as hyponatremia is considered integral to the disease process . Clinical Scenario A 68-year-old male presents to the ED with confusion , nausea , and a 12-pound weight gain over the past week. He was diagnosed with small cell lung cancer two months ago. Vitals: BP: 160/90 mmHg HR: 110 bpm Labs: Serum sodium: 122 mEq/L Serum osmolality: Decreased Urine: Elevated osmolality and high sodium concentration Indicators Suggestive of SIADH Hyponatremia: Sodium level of 122 mEq/L Diluted Serum Osmolality: From water retention Concentrated Urine: High osmolality and sodium levels despite low serum sodium Recent Weight Gain: 12 lbs in one week, pointing to fluid overload Underlying Malignancy: Small cell lung cancer is a well-known cause of ectopic ADH production Documentation Tips 1. Accurate Diagnosis Clearly state “SIADH” and link it to the underlying cause , such as cancer. 2. Clinical Findings Review provider and nursing notes for symptoms like confusion, nausea, and fluid retention. Confirm vital signs and weight gain. Include lab values: sodium, serum/urine osmolality, and urine sodium. 3. Treatment Plan Document fluid restriction orders . Check MAR for medications such as vasopressin receptor antagonists . Note any improvements in symptoms and lab values after treatment. Tip: High blood glucose can artificially lower serum sodium levels. Use a sodium correction calculator to determine the true sodium level. References Centers for Medicare and Medicaid Services. (2024). ICD-10-CM Official Coding Guidelines. Available here: cms.gov Pinson, R., & Tang, C. (2024). The CDI Pocket Guide. Available here: cdiplus.com Prescott, L., & Manz, J. (2024). ACDIS CDI Pocket Guide. Available here: https://acdis.org/ Sterns, R. (2024). Pathophysiology and etiology of SIADH. UpToDate. Yasir, M., & Mechanic, O.J. (2023). Syndrome of Inappropriate Antidiuretic Hormone Secretion. StatPearls Publishing.
