Symptom To Diagnosis - Acute Renal Failure Flashcards
Time frame of ARF?
Occurs over hours or days and can occur in the presence of previously normal kidney function or in patients with CKD.
Is there a standard definition of ARF?
No. Criteria include:
- Increase in serum Cr >0.5.
- Increase of more than 20% above baseline Cr.
- Decrease of GFR of at least 50%.
Prerenal causes of ARF - 3 general categories:
- Hypovolemia.
- Hypotension.
- Changes in renal hemodynamics.
Prerenal ARF - Hypovolemia:
- GI fluid loss.
- Renal loss.
- Hemorrhage.
- 3rd spacing.
- Decrease in effective circulating volume: HF, Cirrhosis.
Prerenal ARF - Hypotension:
- Sepsis.
- Cardiogenic shock.
- Anaphylaxis.
- Anesthesia- and medication-induced.
- Relative hypotension below patient’s autoregulatory level.
Prerenal ARF - Changes in renal hemodynamics:
- NSAIDs/ COX2.
- ACEIs/ARBs.
- Renal artery thrombosis or embolism.
- AAA.
Intrarenal ARF - 4 general etiologies:
- Vascular.
- Glomerular.
- Tubular.
- Interstitial.
Intrarenal ARF - Vascular etiology:
- Vasculitis.
- Malignant HTN.
- Cholesterol emboli.
- Thrombotic microangiopathies –> TTP, HUS, DIC.
Intrarenal ARF - Glomerular etiologies:
Inflammatory: 1. Post infectious GN. 2. Cryoglobulinemia. 3. Henoch-Schönlein purpura. 4. SLE. 5. ANCA GN. 6. Anti-BM disease. \+ Thrombotic microangiopathies.
Intrarenal ARF - Tubular etiologies:
- Ischemic due to prolonged renal hypoperfusion.
- Toxin induced:
a. Medications (aminoglycosides).
b. Radiocontrast media.
c. Heavy metals (cisplatinum).
d. Intratubular pigments (myoglobin, Hb).
e. Crystals (uric acid, oxalate) or proteins (myeloma).
Intrarenal ARF - Interstitial etiologies:
- Acute interstitial nephritis.
- Bilateral nephritis.
- Infiltration (lymphoma, sarcoidosis).
Postrenal ARF - mechanical causes from ureter:
Must be BILATERAL to cause ARF.
- Stones.
- Tumors.
- Hematoma.
- Retroperitoneal adenopathy or fibrosis.
Postrenal ARF - Mechanical causes from the bladder neck:
- BPH/Prostate cancer.
- Tumors.
- Stones.
Postrenal ARF - Mechanical causes from the urethra:
- Strictures.
- Tumors.
- Obstructed indwelling catheters.
A neurogenic cause of Postrenal ARF:
Neurogenic bladder.
Best overall measure of kidney function:
GFR (difficult to accurately measure in clinical practice).
Relationship between GFR and creatinine:
Varies inversely and exponentially, so that relatively small changes changes in serum serum creatinine may reflect significant decreases in GFR.
Creatinine clearance is lower or higher than GFR?
Higher because creatinine is also secreted in the urine.
Cystatin C as a measure of kidney function:
- Freely filtered by glomerulus.
- Less variable than creatinine.
- Not yet in widespread use.
Estimating GFR using the … formula?
Cockcroft-Gault.
[(140-age)x weight in kg]/ 72x creatinine in mg/dL.
Must not miss diagnoses in ARF:
Hypovolemia and obstruction.
The evaluation of ARF always begins with?
- Urine electrolytes.
2. Urinalysis.
ATN - Textbook presentation:
Presentation ranges from ASYMPTOMATIC (with discovery of an increased creatinine on routine laboratory testing) to symptoms of uremia (eg lethargy, nausea, delirium, seizures, edema, and dyspnea).
Inability to DECREASE AFFERENT arteriolar resistance:
- Older age.
- Atherosclerosis.
- Chronic HTN.
- CKD.
- Malignant HTN.
- NSAIDs/COX2.
- Sepsis.
- Hypercalcemia.
- Cyclosporine/Tacrolimus.
- Renal artery stenosis.
Inability to INCREASE EFFERENT arteriolar resistance:
- ACEIs.
2. ARBs.
ATN accounts for …-…% of ARF in hospitalized patients and for …% in outpatients.
55-60%.
11%.
MCC of ATN:
Post operative ATN and contrast-induced nephropathy (CIN).
Mortality in HOSPITALIZED patients with ATN is about …%.
In ICU patients, mortality is about …%.
37%.
78%.
Risk factors for increased mortality in ARF:
- Male sex.
- Advanced age.
- Comorbid illness.
- Malignancy.
- Oliguria.
- Sepsis.
- Mechanical ventilation.
- Multiorgan failure.
- Severity of illness.
ATN - Full recovery occurs?
Over 1-2 weeks in about 60% of survivors.
A post ATN diuresis, during which urinary output transiently increases, may be seen.
Overall, …-…% of patients with ATN require long-term dialysis.
5-10%.
…% of patients in whom ATN develops in the ICU and who survive require dialysis.
33%.