S10C91 - Acute Renal Failure Flashcards
1
Q
Renal Failure: Approach
A
Prerenal – Intrinsic – Postrenal
Prerenal : decreased perfusion
Intrinsic: pathology in the kidney
Postrenal: obstructive
Community-acquired tends to be prerenal
Hospital-acquired tends to be intrinsic (ATN)
2
Q
GFR
A
- 120ml/min/1.73m2 in early adulthood
- decreases by 8 every decade after
3
Q
ATN
A
- form of intrinsic kidney injury
- decreased renal perfusion causes ischemic injury to the parenchyma
4
Q
Postrenal failure
A
- obstruction initially causes a rise in tubular pressure and thus a decreased driving force for filtration, however the pressure equalizes and after that it is vasoconstrictor properties that continue to depress the GFR
- relief of obstruction decreases the vasoconstriction
5
Q
ARF - recovery
A
- once insult to kidney has been removed, whatever remaining surviving nephrons will hypertrophy to try to boost the GFR, how much the GFR recovers depends on how many nephrons remain
- if not enough nephrons remain, the hyperfiltration results in sclerosis and actual worsening of function
6
Q
ARF: Sx
A
- symptoms are a late finding and are caused by the increased uremia
- n/v, drowsy, fatigue, confusion, coma
7
Q
Pre-renal: symptoms and causes
A
- -pre-renal: thirst, orthostatic light-headedness, decreased u/o
- causes: n/v/d, excessive urination, hemorrhage, fever, excessive sweating (reduced circulating volume)
- third spacing causes: sepsis, pancreatitis, burns, heaptic failure
- overdiuresis: CHF
- decreased fluid intake
8
Q
Intrinsic renal failure: symptoms and causes
A
- flank pain and hematuria: crystal-induced nephropathy, nephrolithiasis, papillary necrosis
- ischemic AKI: cardiac arrest, severe sepsis, hypotension
- pigment-induced ARF: rhabdomyolysis, hemolysis (recent TFN) (rhabdo from coma, seizures, intoxication, exercise)
- myalgias, dark urine, edema, malaise, fever think: glomerulonephritis from previous pharyngitis infxn or skin infxn
- fever, arthralgia, rash: interstitial nephritis
- acute renal arterial occlusion: flank pain
- cough, dyspnea, hemoptysis: pulmonary-renal syndrome (good pasture syndrome, wegener granulomatosis)
9
Q
Post-renal: symptoms and causes:
A
- previous prostat dz
- indwelling bladder catheters are a risk
- anuria
- alternating oliguria and polyuria are pathognomonic of obsruction
10
Q
Pre-renal: DDx
A
Hypovolemia:
- GI: decreased intake, vomiting, diarrhea
- diuretics
- third spacing
- skin loss: fever, burn
- other: hypoaldosteronsim, salt-losing nephropathy, post-obstructive diuresis
Hypotension:
- septic vasodilation
- hemorrhage
- decreased CO: ischemic/infarct, valvulopathy, cardiomyopathy, tamponade
- drugs: BB, CCB
- high-output failure: thyrotoxicosis, thiamine deficiency, paget dz, AV fistula
Renal artery and small vessel dz:
- ebolism
- thrombosis: atherosclerosis, vasculitis, SCD
- dissection
- drugs: NSAID, ACEi, ARB, cyclosporine, tacrolimus
- microvascular thrombosis: preeclampsia, HUS, DIC, vasculitis, SCD
- hypercalcemia
11
Q
Postrenal ARF: DDx
A
- malignancy
- nephrolithiasis
- reteroperitoneal dz
- GU surgery
- indwelling catheters
Infants/Children:
- urethra and bladder outlet: anatomic malformations (urethral atresia, meatal stenosis, urethral valves in boys)
- ureter: anatomic malformations: vesicoureteral reflux (females), ureterovesical jxn obstruction, ureterocele, megaureter (prune belly) syndrome, retrocaval ureter
- retroperitoneal tumor
All ages:
- trauma
- blood clot
- urethra/bladder outlet: phimosis, urethral stricture, neurogenic bladder (DM, SC dz, MS, parkinson’s), stone, meds (anticholinergics, alpha-adrenergic antagonists, opiates)
Adults:
- urethra/bladder outlet: BPH, obstructed catheters, cancer (prostate, bladder, Cx, colon)
- ureter: stones, papillary necrosis (SCD, DM, pyelonephritis), tumor (carcinoma of ureter, uterus, prostate, bladder, colon, rectum, retro-peritoneal lymphoma, uterine leiomyomata), retroperitoneal fibrosis (TB, sarcoid, methylsergie, propranolol, idiopathic), stricutre (TB, radiation, schestosomiasis, NSAIDs), miscellaneous (aortic aneurysm, pregnant uterus, IBD, clot, trauma, surgical accident)
12
Q
Intrinsic renal failure: Ddx
A
Tubular dz:
- ischemic ATN
- nephrotoxins: aminoglycosides, contrast, cisplatin, amphotericin B, heme pigments (rhabdo, hemolysis)
- obstruction: uric acid, calcium oxalate, myeloma light chains, amyloid
- obstructive meds: sulfonamide, triamterene, acyclovir, indinavir
Interstitial dz:
- acute interstitial nephritis: drug rxn (NSAID, Abx, diuretics, phenytoin allopurinol, rifampin)
- infxn: b/l pyelonephritis, legionnaire dz, hantavirus infxn
- infiltrative dz: sarcoidosis, lyphoma
- autoimmune dz: SLE
- toxins: aristolochic acid (used for wt loss)
Glomerular dz:
-rapidly progressive glomerulonephritis: goodpasture syndrome, wegener granulomatosis, HSP, SLE, membranoproliferative glomerulonephritis, postinfectious glomerulonephritis
Small-vessel dz:
- microvascular thrombosis: preeclampsia, HUS, DIC, thrombotic thrombocytopenic purpura, vasculitis (polyarteritis nodosa, SCD, atheroembolism)
- malignant HTN
- scleroderma
- renal vein thrombosis
13
Q
Creatinine
A
- a pt with a low baseline Cr can lose 1/2 of their functioning nephrons before the develop an elevated Cr level
- Cr is a breakdown product of muscle protein creatine, therefore the level is linked to muscle mass
14
Q
urinalysis
A
- RBC enter filtrate in glomerulonephritis and form casts
- in ATN, tubular epithelium breaks down and allows pretein to leak into the filtrate and tubular epithelial cells in the sediment
- hyaline casts are commin in prerenal failure
- pigmented granular casts are common in ischemic or toxic tubular injury
- brown granular casts are common in pigment nephropathy (myoglobinuria/hemoglobinuria)
15
Q
Imaging in ARF
A
- osbtruction below bladder should be investigate with u/s
- renal u/s has 90% sensitivity and specificity for identifying hydronephrosis d/t mechanical obstruction
- noncontrast CT has same sensitivity for hydronephrosis as u/s and can identify the sit and cause of obstruction
