The Kidney Disease Acronym Spectrum ARI CKD AKI

The Kidney Disease Acronym Spectrum: ARI, CKD, AKI, ARF, and ESRD Trey La Charité, MD Physician Advisor, Clinical Documentation Integrity Project and Coding University Health Systems Knoxville, TN Cell: 865/250 -9625 Office: 865/305 -9081 Clachari@mc. utmck. edu

Topic Outline • Basic renal anatomy/physiology • Clinical and CDI implications of BUN & Cr • Renal disease definitions with CDI applications – ARF/AKI – CKD – ARI – ESRD – Emergent HD indications • Query opportunity examples

Kidney Facts • Each kidney about size of computer mouse or • • closed fist Nephron is functional unit of kidney – Each kidney contains ~ 1 million nephrons Number of nephrons naturally decreases by ~ 10% every decade of life ☻Everybody gets CKD if live long enough! Clinicians monitor blood urea nitrogen (BUN) & serum creatinine (Cr) to assess renal function Patients may not show any clinical signs of disease until only 20% of nephrons remain

Kidney Structure Nephron

Nephron Structure

Basic Renal Physiology • Glomerular filtration rate (GFR) = amount of blood filtered through all nephrons in 1 hour – “Normal” GFR (e. Cr. Cl) ~ 125 cc/hr • Ultrafiltrate moves into and through Bowman’s capsule into nephron tubule system: Proximal convoluted tubule Loop of Henle Distal convoluted tubule • Ultrafiltrate modified in nephron tubule system via reabsorption, secretion, and concentration – Only 1% of initial ultrafiltrate excreted as urine

Renal Physiology Facts • Ultrafiltrate in Bowman’s capsule contains • • ‼ • • everything (BUN & Cr) but cells & large proteins +, Cl-, H 0, AAs, glucose, vits PCT reabsorbs Na 2 Loop of Henle reabsorbs H 20 concentrating fluid DCT reabsorbs urea back into blood (BUN) Collecting duct reabsorbs H 20 for further fluid concentration & urea into blood (BUN) Creatinine filtered & secreted in PCT (only 5%– 10%), but not reabsorbed Normal serum BUN ~ 10– 20 Normal serum creatinine ~ 1. 0

What About the BUN/Cr Ratio? • Understanding BUN/Cr ratio significance can lead clinician to potential cause(s) of kidney function abnormalities ☻Leads CDI personnel to query opportunities for POA indicators, cause & effect relationships, and missed diagnoses – Normal BUN/Cr ratio = 10: 1 to 20: 1 • In assessing abnormal kidney function, clinicians review the BUN/Cr ratio to discern if lower, equal to, or higher than normal – Helps suggest cause, guide needed workup, and determine best treatment approach

Clinician Kidney Disease Thinking • Clinicians are taught to divide kidney disease into 3 broad categories: – Prerenal = problem occurs before nephron – Intrarenal = problem occurs within nephron – Post-renal = problem occurs after nephron • BUN/Cr ratio suggests which category current kidney problem likely falls into • Knowing which category kidney abnormality falls into can drive your query process

BUN/Cr Ratio Utility for CDI • Prerenal ~ BUN/Cr ratio GREATER than 20: 1 – Reduced blood flow equally decreases both BUN & creatinine filtration at glomerulus – However, urea reabsorption in DCT and collecting duct now increases as pumps have longer time to work on slower moving fluid – Therefore, both values rise but BUN rises faster than creatinine increasing their ratio • Additional findings in prerenal pathology – Urine Na+ < 20 – Fe. Na+ < 1% – Fe. Urea < 35%

BUN/Cr Query Opportunities • If prerenal (50%– 70% of AKI), CDI personnel should then be asking “Why? ” 1. Volume problem – DKA/HHNC – Hemorrhage – Cirrhosis/burns – Vomiting/diarrhea 2. Perfusion problem – CHF – Shock (septic/cardiogenic)

BUN/Cr Ratio Utility • Intrarenal ~ BUN/Cr ratio LESS than 10: 1 – If glomeruli are damaged, BUN & creatinine filtered less but both equally reduced – Nephron tubule damage decreases urea reabsorption as pumps are broken • Serum BUN rises much slower – Therefore, both levels rise but their ratio actually decreases • Additional findings in intrarenal pathology – Urine Na+ > 40 – Fe. Na+ >> 1% – Fe. Urea > 50%

BUN/Cr Query Opportunities • If intrarenal (25% of AKI), why? 1. Vascular – Vasculitis (Wegner’s) – Renal atherosclerosis – Nephrosclerosis – RAS 2. Glomerular – RPG – Ig. A nephropathy – Postinfectious – SLE – Membranoproliferative 3. Tubular – Acute tubular necrosis – Autoimmune – Acute interstitial nephritis – MM

Intrarenal Pathology and CDI • Acute kidney failure codes (584. X) partially differentiated by underlying etiology – 584. 9 = Acute kidney failure, unspecified – 584. 5 = Acute kidney failure w/ lesion of tubular necrosis – 584. 6 = Acute kidney failure w/ lesion of renal cortical necrosis – 584. 7 = Acute kidney failure w/ lesion of renal medullary necrosis – 584. 8 = Acute kidney failure w/ other specified lesion in kidney • 584. 9 is a CC while rest are MCCs

BUN/Cr Ratio Utility • Post-renal ~ BUN/Cr ratio EQUAL TO normal – “Normal” range = 10: 1 to 20: 1 – Nephron works fine but urine can’t get out of body due to obstruction distal to kidney – Therefore, both levels rise but rise equivalently preserving a relatively normal ratio between them • Additional findings in post-renal physiology – Renal US or CT scan ABD/Pelvis with significant hydronephrosis proximal to obstruction

BUN/Cr Query Opportunities • If post-renal (5%– 10% of AKI), why? – BPH – Prostate CA – Bladder CA – Metastatic malignancy (cervical/ovarian) – Retroperitoneal fibrosis – Retroperitoneal hemorrhage/hematoma – Nephrolithiasis

ARF/AKI and CDI • When a patient’s serum creatinine dramatically rises above their baseline level, it is more than just “dehydration” or “azotemia” or “acute renal insufficiency” • This is “acute renal/kidney failure” LNot “acute on chronic kidney disease” • Must write out what “ARF/AKI” means at least once in the chart! – Auditors may question what ARF or AKI means without writing out acronym one time • ARF/AKI definition revised 8/11 by KDIGO

Acute Kidney Injury Definition 1. Any rise in serum creatinine of 0. 3 mg/dl or more above patient’s baseline. . . -Either/Or 2. Any rise greater than or equal to 1. 5 times patient’s baseline serum creatinine ‼ “Baseline” = lowest recorded creatinine value for patient in preceding 3 months www. renal. org/Clinical/Guidelines. Section/Acute. Kidney. Injury. aspx* *Note: This was updated in March 2012

ARF/AKI Query Strategy • First, decide/verify whether patient meets criteria of ARF/AKI – If no, yet clinician has called this in chart, will need clarification prior to coding LCoders not allowed to question physicians’ judgment while post-discharge auditors are allowed – If yes, go to next step • Second, calculate the BUN/Cr ratio – Is problem pre-, intra-, or post-renal? • Third, is the urinalysis helpful? ☻With this information, is there now opportunity to further clarify why patient has ARF/AKI?

What About the Urinalysis? • Prerenal – Hyaline casts • Intrarenal 1. Proteinuria 2. Cells (WBCs & RBCs) 3. Cell casts: • WBC (AIN) • RBC (glomerulonephritis) • Epithelial (ATN) • Post-renal – Benign/no significant abnormalities – Hematuria

Current ARF/AKI Coding • Per KDIGO, “acute renal failure” terminology to be replaced by “acute kidney injury” • Problem: “AKI” currently codes to “ARF” Problem • Therefore, physicians should not document AKI unless they truly mean ARF L Watch for clinicians using AKI to describe any acute renal abnormality even if does not meet ARF criteria • Some physicians will adopt this new terminology regardless of coding implications – May increase need for query clarifications, so do not report ARF when not actually present

Future ARK/AKI Coding? • Presently, no documentation benefit for physicians documenting stage of AKI • Hopefully … ICD-9 or ICD-10 codes will be created for AKI stages • Suspect … Stages 1 & 2 will be CCs while Stage 3 will be an MCC • Start medical staff education of stages when AKI codes definitively arrive – Teaching new failure definitions tough enough without confusing issue with stages

Chronic Kidney Disease Def: Presence of kidney damage or decreased kidney function persisting for at least 3 months regardless of cause • • • Stage III GFR = > 90 ml/min GFR = 60– 89 GFR = 30– 59 Stage IV Stage V GFR = 15– 29 CC GFR < 15 (but no HD/PD) CC

Chronic Kidney Disease • In order to properly stage CKD, physicians must either calculate Cr. Cl or have it provided for them • e. Cr. Cl estimates GFR via Cockcroft-Gault eq e. Cr. Cl = (140 - patient’s age) x patient’s wt in Kgs 72 x patient’s baseline serum creatinine X 0. 85 for women patient’s ideal weight = 60 Kgs for women and 70 Kgs for men • Reduced credit given if physician documents “CKD” only without stage

CKD Query Opportunities • Most important determinants of Cockcroft-Gault equation estimation: 1. Patient’s age 2. Patient’s serum creatinine ‼ Serum creatinine greater effect than age • Calculate Cr. Cl for anybody with. . . – Serum creatinine > 1. 0 – Age of 50 years or older regardless of serum creatinine level • Why?

What if Acute Rise But Not ARF? • In the acute setting, what does one call the “noman’s land” between a patient’s baseline creatinine and ARF/AKI? Patient’s baseline creatinine (normal or CKD) ? Increasing serum creatinine ARF AKI

No ‘Great’ Answers • “Azotemia” or “uremia” = 790. 6, Other abnormal blood chemistry • “Dehydration” = 276. 51 – Not accurate for creatinine rises due to intraor post-renal etiologies • “Acute nephropathy” = 580. 9, Acute glomerulonephritis with unspecified pathologic lesion in kidney ☻“Acute renal insufficiency” = 593. 9, Unspecified disorder of kidney and ureter

End-Stage Renal Disease • Failure of kidneys to perform functions necessary to support daily life – Usually occurs when less then 10% of renal function remains • Patients cannot survive without routine dialysis or a kidney transplant – Patients qualify for permanent dialysis when their measured Cr. Cl is 10 mg/dl or less ☻Query opportunity for ESRD when here – Your nephrologists may start preparing patient for HD/PD when Cr. Cl = 15 mg/dl • ESRD (585. 6) is an MCC

Emergent HD Query Opportunities • Indications for emergent dialysis: A = Acidosis E = Electrolytes (i. e. , hyperkalemia causing cardiac arrhythmias) I = Ingestion (beware of psychiatric codes as principal dx) O = Overload (Is there really acute CHF? ) U = Uremia (not really done anymore) Y = Why? Why not because nobody understands nephrology or nephrologists!

Renal Disease CDI Pocket Card

Example #1 • 48 yo WF comes to ED with complaints of fever, chills, cough w/ green sputum, myalgias, and weakness. She is tachycardic w/ T = 102. 7. She is hypotensive & requires 4 liters IVF to normalize BP. Initial WBC = 28. 7. Initial workup reveals sepsis due to multilobar pneumonia. Patient did notice her urine had been very dark. Initial BUN & Cr are 32 & 3. 8. Last recorded BUN & Cr were 19 & 0. 8 in PCP’s office 2 months ago. UA reveals large amount of protein and numerous epithelial cell casts. BUN & Cr almost normalize by time of discharge.

Example #1 • Patient initially admitted to ICU for “sepsis” and “acute renal failure. ” • Does the patient have acute renal failure? – Absolutely! 1. 5 x 0. 8 = 1. 2 • What’s the BUN/Cr ratio? = Intrarenal – 32/3. 8 = 8. 42 • Does the urinalysis help? – Epithelial cell casts and large proteinuria consistent with ATN ☻Query opportunity for ARF due to ATN (POA) potentially giving case an MCC

Example #2 • 87 yo WM w/ Alzheimer’s dementia, CHF, CAD, & PVD sent to ED from NH for lethargy & unresponsiveness. Initial workup reveals Na+ = 167, Cl- = 118, K+ = 5. 5, BUN = 89, Cr = 2. 8. Lowest recorded BUN & Cr = 29 & 2. 1 at recent discharge for diastolic CHF exacerbation 6 weeks earlier. CBC essentially WNL while had always been anemic during previous admissions. Urinalysis significant for numerous hyaline casts. Patient aggressively hydrated and BUN & Cr return to his baseline. Patient eventually discharged to a different nursing home.

Example #2 • Patient initially admitted for “acute renal failure. ” • Does the patient have acute renal failure? – NO! 2. 1 + 1. 0 = 3. 1 • What’s the BUN/Cr ratio? = Prerenal – 89/2. 8 = 31. 79 • Does the urinalysis help? – Hyaline casts consistent with prerenal cause ☻Clarification opportunity for ARI on CKD stage 4 possibly preventing an incorrect coding submission of ARF

Example #3 • 63 yo WM comes to ED for painful urination, difficulty initiating stream, hematuria, weakness, & 4 months wt. loss w/out effort. Not seen physician since 1976. CT scan of urinary tract reveals bilateral hydronephrosis w/ markedly enlarged & necroticappearing prostate w/ pelvic lymphadenopathy. Initial BUN & Cr noted to be 55 & 3. 3. Foley catheter insertion results in significant diuresis & eventual normalization of BUN & Cr. UA WNL except for hematuria. After biopsy, principal diagnosis established as “metastatic prostate cancer” & radical prostatectomy is performed.

Example #3 • Primary service repeatedly documents “obstructive uropathy” to describe renal function. • Does the patient have acute renal failure? – Absolutely! BUN & Cr normalized • What’s the BUN/Cr ratio? = Post-renal – 55/3. 3 = 15. 71 • Does the urinalysis help? – Hematuria only not much help ☻Query opportunity for acute renal failure (POA) potentially giving case a CC

Example #4 • 27 yo AA male comes to ED complaining of hard & painful inguinal lesions, recurrent fevers w/ chills, weakness, & fatigue. Initial VS reveal BP = 88/45, HR = 113, T = 101. 9, RR = 28, RA O 2 sat = 98%. Initial BUN & Cr = 31 & 1. 4, which improve to 21 & 1. 1 w/ hydration. Patient diagnosed w/ sepsis & requires several abscess I&D procedures. Blood cxs & abscess cxs repeatedly grow streptococcal species despite broad spectrum ABX. On hospital day 9, BUN & Cr start to rise. By day 13, BUN & Cr = 34 & 4. 3 despite aggressive IVF & numerous medication adjustments.

Example #4 • Does the patient have acute renal failure? – Absolutely! 1. 1 x 1. 5 = 1. 65 • What’s the BUN/Cr ratio? – 34/4. 3 = 7. 9 = Intrarenal • Is the urinalysis helpful? – Proteinuria consistent w/ intrarenal pathology • ASO titer returns positive & renal biopsy reveals postinfectious glomerulonephritis ☻Query opportunity for ARF & acute poststreptococcal glomerulonephritis (POA) potentially giving case 1 CC & 1 MCC

Example #5 • 67 yo WM comes to ED w/ complaints of SOB, swelling, & weakness. Neighbor found him after being in shower for 6 hours because too weak to get out. Patient has severe anasarca w/ BUN & Cr of 94 & 2. 9. UA w/ 3– 5 hyaline casts. CXR shows pulmonary edema & ECHO reveals EF ~ 15% w/ global hypokinesis. CHF medication optimization & aggressive IV diuretic regimen do not produce significant urine output. Natricor & Bumex drip finally produce results. Patient also hypotensive throughout hospitalization. Patient goes home w/ BUN & Cr down to 53 & 1. 7.

Example #5 • Patient initially admitted for “anasarca” only. • Does the patient have acute renal failure? – Absolutely! 1. 7 x 1. 5 = 2. 55 • What’s the BUN/Cr ratio? – 94/2. 9 = 32. 4 = Prerenal • Does the urinalysis help? – Hyaline casts consistent with prerenal cause ☻Query opportunities for establishing acute systolic CHF exacerbation (POA) as principal diagnosis and for ARF & cardiogenic shock potentially giving case 1 CC & 1 MCC

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