Study guide
6.3 AKI, CKD Staging, UTI, and Urinary Stones
Certified Clinical Documentation Specialist CCDS
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Eligibility Pathways and the 2,000-Hour Year 1.3 Allowed Resources and Test-Day Rules 1.4 Recertification, Fees, and How This Guide Maps the Eight Domains
2 IPPS Foundations
2.1 How IPPS Works and How CMS Updates It 2.2 MS-DRG Assignment, Relative Weights, and Grouping 2.3 Provider and Clinical Staff Documentation Duties under IPPS
3 Severity, CMI, Medical Necessity, and Oversight
3.1 CC versus MCC Recognition and CC Exclusion Lists 3.2 Case Mix Index and Why CDI Tracks It 3.3 Two-Midnight Rule, Medical Necessity of Setting, and Principal Diagnosis 3.4 MAC, RAC, CERT, OIG, and Denial-Vulnerable Practices
4 Nervous and Respiratory System CDI
4.1 Nervous System Conditions for CDI 4.2 Acute and Chronic Respiratory Failure, ABGs, and Ventilation Support 4.3 Pneumonia, COPD, PE, Pleural Effusion, and Respiratory Infections
5 Circulatory, Digestive, Hepatobiliary, Musculoskeletal, and Skin CDI
5.1 Circulatory Disorders 5.2 Digestive and Hepatobiliary Disorders 5.3 Musculoskeletal and Skin
6 Endocrine, Nutrition, Kidney, and Hematologic CDI
6.1 Diabetes, Dehydration, and Obesity 6.2 Malnutrition Criteria, Severity, and Audit Risk 6.3 AKI, CKD Staging, UTI, and Urinary Stones 6.4 Anemia, Coagulation, Sickle Cell, Lymphoma, and Leukemia
7 Infectious Disease, Other MDCs, and Clinical Indicator Tools
7.1 Sepsis, Severe Sepsis, Postoperative and Other Infections 7.2 Mental, Substance Use, Injuries/Toxicology, and HIV-Related Conditions 7.3 Medications, Diagnostic Tests, and Abbreviations as Clinical Indicators
8 Health Record Elements and Query Triggers
8.1 Which Record Elements Support Diagnosis and Procedure Codes 8.2 Attending versus Radiologist, Pathologist, and Other Providers 8.3 When a Physician Query Is Warranted 8.4 When Queries Are Not Appropriate
9 Query Timing, Verbal Queries, Formats, and Clinical Indicators
9.1 Concurrent, Retrospective, Pre-Bill, and Prospective Timing 9.2 Verbal Queries and Required Documentation 9.3 Open-Ended, Multiple-Choice, and Yes/No 9.4 Clinical Indicators and How to Source Them
10 Compliant Query Practice and Clinical Validation
10.1 Compliant versus Leading and Other Noncompliant Queries 10.2 ACDIS/AHIMA 2026 Guidelines for Achieving a Compliant Query Practice 10.3 Clinical Validation and Diagnoses without Clinical Support
11 CDI Program Metrics
11.1 Productivity, Query Volume, and Provider Response Rates 11.2 CMI, CC/MCC Capture, and High-Frequency DRGs 11.3 SOI/ROM as CDI Program Performance Metrics
12 Physician Metrics, PEPPER, Forecasting, and Public Data
12.1 Measuring Physician Documentation Performance 12.2 PEPPER, Forecasting, Hospital Financial Data, and Public Reporting
13 CDI Roles, Coder Collaboration, and Physician Education
13.1 Roles and Responsibilities of the CDI Specialist 13.2 Coder Roles Working with a CDI Department 13.3 Physician Education Tools, Forms, and Presentations
14 Provider Communication and DRG Reconciliation
14.1 Non-Confrontational Communication and When Verbal Beats Written 14.2 Working DRG versus Final DRG Reconciliation
15 Official Guidelines, Principal Diagnosis, and Secondary Diagnosis
15.1 Official Guidelines, Cooperating Parties, Updates, and AHA Coding Clinic 15.2 Principal Diagnosis Selection 15.3 Secondary Diagnosis Reporting Criteria
16 Sequencing, Coding Conventions, and POA Indicators
16.1 Sequencing When Two Diagnoses Equally Meet PD; Working DRG with Multiple Diagnoses 16.2 Integral Signs/Symptoms, the With Convention, and Uncertain Diagnoses 16.3 Present-on-Admission Indicator Assignment and Payment Impact
17 Hospital-Acquired Conditions, Disposition, and ICD-10-PCS Essentials
17.1 CMS Hospital-Acquired Condition Payment Provision 17.2 Discharge Disposition, Transfer Payment, Principal Procedure, and ICD-10-PCS Essentials
18 Ethics, Privacy, and Leading Queries as Compliance Failures
18.1 ACDIS Code of Ethics and CDI Goals beyond Reimbursement 18.2 HIPAA, Minimum Necessary, and Record Confidentiality 18.3 Leading Queries as a Compliance Failure
19 DRG Creep, OIG Oversight, PEPPER, and the False Claims Act
19.1 DRG Compliance, DRG Creep, and the OIG Work Plan 19.2 PEPPER Compliance Risks and the False Claims Act
20 Mortality Index, Observed-to-Expected Ratios, and Quality Data Sources
20.1 Documentation Impact on Mortality Index (SOI/ROM) 20.2 Mortality Reviews and Observed-to-Expected Ratios 20.3 Abstracted versus Claims-Based Quality Data
21 CMS Quality Programs, PSIs, and Infection versus Complication Codes
21.1 HVBP, HAC Reduction Program, HRRP, 30-Day Mortality, and Hospital IQR 21.2 PSI 90 Components and PSIs beyond the Composite 21.3 Healthcare-Associated Infections versus Complication Codes
6.3 AKI, CKD Staging, UTI, and Urinary Stones
Key Takeaways Explain This Topic AI
KDIGO creatinine and urine-output thresholds are clinical indicators you may cite neutrally; they are not automatic AKI codes
Renal insufficiency is nonspecific; query for acute versus chronic versus both, and for CKD stage including ESRD or dialysis when applicable
AKI on CKD is a reportable combination when both are documented and this-stay relevant
CAUTI versus community UTI depends on catheter association plus POA at the inpatient order; N or U on a HAC-listed catheter infection generally prevents CC/MCC payment
Stones need location plus whether obstruction and infection are present; hydronephrosis on imaging is an indicator, not a finished diagnosis
Last updated: September 2026
6.3 AKI, CKD Staging, UTI, and Urinary Stones
Quick Answer: Treat Kidney Disease: Improving Global Outcomes (KDIGO) creatinine and urine-output thresholds as clinical indicators , not as codes. Query unspecified renal insufficiency for acuity and chronic kidney disease (CKD) stage. Document acute kidney injury (AKI) on CKD when both are present. Distinguish catheter-associated urinary tract infection (CAUTI) from community-onset urinary tract infection (UTI) using POA relative to the inpatient order . Specify stones, obstruction, and infection as separate diagnostic questions.
This independent ExamFinch section is for inpatient CDI under IPPS. It cites KDIGO as a publicly used AKI framework. Neutral citation in a query is consistent with the 2026 ACDIS/AHIMA brief. Auto-coding AKI from a creatinine delta is not.
Kidney language is usually too vague
Progress notes recycle “renal insufficiency,” “elevated Cr,” “CKD,” “UTI,” and “kidney stone.” Those phrases do not tell the grouper whether the injury is acute, what CKD stage applies, whether a catheter is implicated, or whether a stone is obstructing or infected. Domain II expects you to know the physiology well enough to recognize indicators and to query for the missing diagnostic pieces.
AKI indicators versus a provider diagnosis
Acute kidney injury (also documented as acute kidney failure) is a sudden decline in glomerular filtration. KDIGO defines AKI using any of:
- Increase in serum creatinine by ≥0.3 mg/dL within 48 hours
- Increase in serum creatinine to ≥1.5 times baseline within the prior 7 days
- Urine volume <0.5 mL/kg/h for 6 hours
Those thresholds are indicators you may cite neutrally at the end of a query template. They are not an instruction to diagnose AKI, and they are not ICD-10-CM codes. A creatinine rise from 1.0 to 1.4 mg/dL in two days is a classic indicator; the diagnosis still belongs to the provider. KDIGO AKI stages 1–3 are additional clinical detail. If the provider documents a stage, capture it. Do not invent a stage from the lab strip.
Acute tubular necrosis (ATN) , prerenal azotemia, and postrenal obstruction are etiologic refinements. If the attending writes “AKI” and nephrology writes “ATN from sepsis,” you have a more specific acute diagnosis. If the chart only shows a bump after diuretics, a query for prerenal injury versus ATN versus unspecified AKI may be warranted—without leading toward the option that yields a CC. Exact CC/MCC assignment depends on the current IPPS tables; this guide does not reprint them. Later-stage CKD and AKI frequently affect MS-DRG severity when they meet UHDDS criteria.
Chronic kidney disease is staged by estimated glomerular filtration rate (commonly stages 1–5 / G1–G5), with end-stage renal disease (ESRD) when the patient is on chronic dialysis. Unspecified CKD and “renal insufficiency” hide whether the patient is stage 3a or stage 5. Query “renal insufficiency” for:
- Acute, chronic, or acute-on-chronic
- CKD stage if chronic disease is present
- Dialysis dependence if applicable
Etiology when it is already in the chart (diabetes, hypertension) and the relationship is not stated, following Official Guidelines on causal language
AKI on CKD is a real and reportable combination when both are documented. Do not let “baseline creatinine 2.4, now 3.8” remain labeled only as CKD. Do not let a transient bump overwrite a long-standing stage 4 diagnosis. Both stories can be true on one stay.
- Phrase in the record Problem CDI target
- Renal insufficiency Acuity and stage unknown Acute versus chronic versus both; CKD stage
- CKD, unspecified Stage missing Stage 1–5 or ESRD
- Elevated creatinine Finding, not a diagnosis AKI, CKD, dehydration, medication effect, or other
- UTI Site, catheter, organism, timing Cystitis versus pyelonephritis; CAUTI versus community; POA
- Kidney stone Location and complications Site; obstruction; infection; hydronephrosis
Common adult CKD banding used as indicators (not as codes you assign from eGFR alone): stage 1 GFR ≥90 with kidney damage; stage 2 60–89; stage 3a 45–59; stage 3b 30–44; stage 4 15–29; stage 5 <15. The provider still states the stage.
UTI, CAUTI, and POA
A urinary tract infection may be cystitis, pyelonephritis, or unspecified UTI. Pyelonephritis implies upper-tract involvement and a different picture (fever, flank pain, often a more aggressive treatment plan). Query unspecified “UTI” when imaging, fever, and bacteremia suggest pyelonephritis, or when the organism and site are named in culture but not in the provider assessment.
Catheter-associated UTI is both a clinical diagnosis and a quality construct. For claims, you need provider documentation that the UTI is associated with a urinary catheter. For CMS quality, CAUTI appears in two programs that must not be merged:
HAC payment provision: urinary-catheter infection is one of the fourteen categories. When the condition is not POA, N or U generally prevents CC/MCC payment for that HAC. W is paid like Y .
HAC Reduction Program: NHSN CAUTI is one of the infection measures in the Total HAC Score, alongside central line–associated bloodstream infection, selected surgical site infections, methicillin-resistant Staphylococcus aureus bacteremia, and Clostridioides difficile .
POA is still anchored to the inpatient order . A UTI diagnosed in the emergency department, even if a Foley is placed in the field after symptoms began, is generally POA = Y if the infection was present at the inpatient order. A CAUTI that develops on hospital day six after admission for hip fracture is typically POA = N and is HAC-relevant. Do not assign CAUTI merely because a catheter is present and the urinalysis is abnormal. Colonization and asymptomatic bacteriuria are not the same as a symptomatic UTI, and the provider must make that distinction.
Conditions arising in the emergency department, observation, or outpatient surgery before the inpatient order remain POA = Y . That rule saves many community UTIs from being mislabeled as hospital-acquired simply because the Foley went in during boarding.
Stones, obstruction, and infection
Nephrolithiasis, ureterolithiasis, and bladder stones are location-specific. The CDI questions are whether the stone is causing obstruction (hydronephrosis, forniceal rupture, post-renal AKI) and whether there is infection (pyelonephritis, pyonephrosis, infected hydronephrosis). A computed tomography report of a 7 mm ureteral stone with hydronephrosis is an indicator. “Kidney stone” in the history is not equivalent to acute obstruction.
Query separately when needed: presence of obstruction, presence of infection, and the relationship to AKI. Multiple-choice options must match the imaging. Do not offer “staghorn calculus with xanthogranulomatous pyelonephritis” when the scan shows a non-obstructing lower-pole stone and a bland urinalysis. Include Other, please specify . Yes/no may substantiate a radiologist’s already-documented hydronephrosis if a provider must confirm it; yes/no may not introduce obstruction from the radiology impression if no provider has named a urinary diagnosis.
Pharmacology indicators include angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and nonsteroidal anti-inflammatory drugs in AKI, iodinated contrast exposure, and antibiotics for UTI. They support queries. They do not replace diagnoses.
Loading diagram... Kidney and Urinary Query Path
Exam-style scenarios
Scenario: creatinine 1.0 to 1.5 in 48 hours. The hospitalist writes “renal insufficiency.” KDIGO creatinine change is an indicator, not a code. Query for AKI versus CKD versus AKI on CKD, and for CKD stage if a baseline exists. Do not drop “AKI stage 2” into the record from the calculator.
Scenario: Foley and a positive urinalysis. Day six after hip fracture, the nurse documents cloudy urine. Culture grows Escherichia coli . The attending writes “UTI.” A catheter is present. That is not yet CAUTI. Query for whether the UTI is catheter-associated, for site if pyelonephritis is in play, and for POA. If the infection began after the inpatient order and the provider links it to the catheter, POA N and HAC payment-provision logic may apply. If the same organism was already treated in the emergency department before the order, POA is Y.
Scenario: stone plus rising creatinine. CT shows an obstructing ureteral stone and hydronephrosis. Creatinine doubled. “Kidney stone” as the only diagnosis leaves obstruction and post-renal AKI on the table. Query obstruction and AKI as clinically relevant options; do not lead with an MCC label.
Scenario: mixing HAC programs. NHSN CAUTI surveillance definitions used by infection prevention are not identical to a coded CAUTI on the claim. The exam still expects you to keep HAC payment provision (fourteen categories, POA N/U versus Y/W) separate from HAC Reduction Program scoring (PSI-90 plus NHSN HAIs).
Study habits
For every kidney chart, ask four questions in order: acuity, chronic stage, infection source and POA, stone complications. Cite KDIGO the way you cite Academy/ASPEN: at the end, neutrally, never as a command. Confirm the inpatient-order timestamp before you call a UTI hospital-acquired.