Approach to Kidney Disease

burden of AKI, CKD, and ESKD

renal failure confers

-high risk of mortality

renal failure as a multiorgan, systemic condition

complications of severe renal failure: pathophysiology → clinical manifestation

uremia

natural history of acute renal failure

-AKI is common

-severe AKI has ~50% in-hospital mortality

-of survivors to discharge, an additional 50% mortality in 3 months after discharge

-majority of survivors who come off of dialysis go on to develop significant CKD or ESRD

serum creatinine as a biomarker of filtration

acute kidney injury (AKI)

-relies on EITHER an absolute or relative change in serum creatinine OR on a decrease in urine output over a short period of time

biomarkers in AKI

improving AKI definitions

-true AKI can be present without a change in Cr (“subclinical AKI”)

-Cr can be elevated without any tubular injury (“pre-renal physiology”)

chronic kidney disease (CKD)

-decreased GFR or kidney damage for >3 months

-progressive stages with more severe loss of kidney function

-upcoming dedicated lecture on CKD and complications

AKI to CKD continuum

AKI v CKD- chronicity

framework for approaching renal failure

determining the cause of AKI

-history

-BUN:Cr ratio

-urinalysis and urine sediment

-urine protein and urine albumin to urine Cr ratios

-FENa or FEUrea (select cases)

-imaging (select cases)

-serologies (select cases)- complement levels, ANCA, anti-GBM, ANA, ENAs, cryoglobulins, SPEP/UPEP with IFE, SFLC, hep serologies, HIV, ASLOP

-kidney biopsy (select cases)

urinalysis- color

-light yellow (dilute) to dark yellow (concentrated)

-red urine should prompt an evaluation for red blood cells, hemoglobin, or myoglobin in the urine

-various medications, genetic disorders, foods, and medical conditions can change the color

urinalysis

-specific gravity

-pH

-leukocytes

-blood/hemoglobin

-nitrites

-ketones

-bilirubin

-urobilinogen

-glucose

-protein

urinalysis- specific gravity

urinalysis- specific gravity: decreased SG, normal range, increased

urinalysis- blood

-hematuria = RBCs in the urine

-hemoglobinuria = free hemoglobin in urine (normally present INSIDE RBCs)- intravascular hemolysis or lysis of RBCs in urine

-myoglobinuria = free myoglobin in urine (normally in intact muscle cells)- rhabdomyolysis (muscle breakdown)

proteinuria estimation

-gold standard is 24 hours urine collection (cumbersome)

-a spot urine protein in isolation is meaningless

-normalizing it to spot urinary Cr is used clinically (assuming average muscle mass where daily Cr production ~1000 mg/day)

urine sediment

urinary sediment constituents

urine sediment- cells

urinary sediment- casts

urinary sediment- crystals

urinary sediment- differential diagnosis

fractional excretion of sodium

urinalysis and urine chemistries- etiology, dipstick, micro, Uosm, FENa

framework for approaching renal failure

urinary tract obstruction and AKI

-ureteral: bilateral stones, papillary necrosis, blood clots, external compression from malignancies, RP fibrosis (IgG4), iatrogenic ligation

-bladder: stones, blood clots, BPH, bladder cancer, prostate cancer, neuropathic

-urethral: stricture, phimosis

-urinary obstruction on imaging