Acute Renal failure

Acute Renal failure : 

Acute Renal failure

classification : 

classification Acute Renal Failure Pre-renal Azotemia Intra-renal Azotemia Post-renal Azotemia

definition : 

definition Acute renal failure (ARF) is a syndrome characterized Rapid decline glomerular filtration rate Retention of nitrogenous waste products Perturbation of extracellular fluid volume electrolyte and acid-base homeostasis

PRERENAL ARF : 

PRERENAL ARF Hypovolemia Hemorrhage, burns, dehydration Vomiting, surgical drainage, diarrhea Renal fluid loss: diuretics, osmotic diuresis (e.g., diabetes mellitus),hypoadrenalism Low cardiac output Diseases of myocardium, valves, and pericardium; arrhythmias, tamponade Pulmonary hypertension, massive pulmonary embolus

Pre-renal ARF cont… : 

Pre-renal ARF cont… Systemic vasodilatation Sepsis, antihypertensives Renal vasoconstriction Hypercalcemia, norepinephrine, epinephrine, cyclosporine, tacrolimus, amphotericin B Hyperviscosity syndrome (rare)

Hepatorenal syndrome : 

Hepatorenal syndrome Irreversible” pre-renal azotemia in the setting of end-stage hepatic disease Pathogenesis: Unrelenting renal vasoconstriction induced by unknown mediators Renin/angiotensis, endothelin, NO, prostanoids, endotoxin, ↑sympathetic tone all implicated; none proven and may reflect secondary phenomena

Etiology of Intrinsic ARF : 

Etiology of Intrinsic ARF

POSTRENAL ARF : 

POSTRENAL ARF

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Ureteric Calculi, blood clot, sloughed papillae, cancer, external compression (e.g., retroperitoneal fibrosis) Bladder neck Neurogenic bladder, prostatic hypertrophy, calculi, cancer, blood clot Urethra Stricture, congenital valve, phimosis

ARF due to nsaids : 

ARF due to nsaids Nonsteroidal anti-inflammatory drugs (NSAID) agents inhibit the synthesis of vasodilatory prostaglandins in the kidney.

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Risk factors: Severe CHF Advanced liver disease Severe atherosclerotic vascular disease CKD

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Elderly patients are at increased risk due to the increased prevalence of cardiac dysfunction, occult renal vascular disease, and subclinical chronic kidney disease.

CLINICAL ASSESSMENT of ARF : 

CLINICAL ASSESSMENT of ARF Urinalysis Renal failure indices Laboratory findings Radiological findings Renal biobsy

urinalysis : 

urinalysis Pre-renal Hyaline casts FENa <1%, UNa <10 mmol/L, SG <1.018 Post-renal Frequently normal Hematuria if stones, hemorrhage, malignancy or prostatic hypertrophy

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Intrinsic ARF Muddy brown” granular casts (ATN and suggest ischemic or nephrotoxic ARF) Hematuria and mild “tubular” proteinuria (impaired reabsorption of filtered proteins by injured proximal tubules) RBC (glomerular injury, acute tubulointerstitial nephritis) WBC nonpigmented granular casts (interstitial nephritis) Lymphocytes (interstitial nephritis by NSAIDs) Heavy proteinuria (interstitial nephritis byNSAIDs) Bilirubinuria (hepatorenal syndrome)

RENAL FAILURE INDICES : 

RENAL FAILURE INDICES Fractional excretion of sodium (FENa) Prerenal ARF typically - <1.0% May be >1.0% if patients are receiving diuretics or have bicarbonaturia, preexisting chronic renal failure complicated by salt wasting, or adrenal insufficiency Ischemic or nephrotoxic ARF - >1.0% FENa is <1.0% due to urinary tract obstruction, glomerulonephritis, and vascular diseases

RADIOLOGIC FINDINGS : 

RADIOLOGIC FINDINGS Renal ultrasound Determines kidney size and presence of masses, cysts, obstruction in upper urinary tract. Computed tomography (CT) scan Cross-sectional view of kidney and urinary tract detects presence/extent of disease. Magnetic resonance imaging (MRI) Provides information about soft tissue damage Pelvicalyceal dilatation Retrograde or anterograde pyelography Provide precise localization of the site of obstruction

RADIOLOGIC FINDINGS cont… : 

RADIOLOGIC FINDINGS cont… Doppler ultrasonography and magnetic resonance angiography Assessment of patency of renal arteries and veins in patients with suspected vascular obstruction Contrast angiography

prevention : 

prevention Maintenance of euvolemia Avoidance of nephrotoxins when possible NSAIDs, aminoglycoside, antibiotics, cyclosporine, tacrolimus, diuretics, cyclooxygenase inhibitors, ACE inhibitors, angiotensin II receptor blockers and other vasodilators Doses of drugs can be adjusted according to patient’s condition BP control--avoidance of excessive hypo- or hypertension

Prevention cont… : 

Prevention cont… Allopurinol and forced alkaline diuresis Uric acid generation and prevent precipitation of urate crystals in renal tubules Dimercaprol (chelating agent) Prevent heavy metal nephrotoxicity Ethanol Inhibits ethylene glycol metabolism to oxalic acid and other toxic Used in emergency management of ethylene glycol intoxication

Treatment : 

Treatment Treatment of hypovolmia Potassium and bicarbonate supplement Large-volume paracentesis increase GFR Lowers intraabdominal pressure and improve flow in renal veins TIPS procedure (Transjugular Intrahepatic Portosystemic Shunting) Increase central blood volume which stimulates release of atrial natriuretic peptides (ANPs) and inhibits secretion of aldosterone and norepinephrine

Treatment : 

Treatment Therapies with Limited Evidence Calcium Channel Blockers Diuretics Atrial Natriuretic Peptide (ANP) Endothelin (ET) Antagonists Prostaglandin E1 ACE Inhibitors Prostaglandin analogues Antioxidants

Treatment cont… : 

Treatment cont… Ureteric obstruction treated initially by percutaneous catheterization of the dilated renal pelvis or ureter

Indication for dialysis : 

Indication for dialysis According to the patient requirement Peritoneal dialysis may be preferable if the patient is hemodynamically unstable Hemodialysis after abdominal surgery involving the peritoneum Clinical evidence (symptoms or signs) of uremia Intractable intravascular volume overload Hyperkalemia or severe acidosis resistant to conservative measures

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