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Introduction to Renal Failure and Acute Renal Failure Jeffrey T. Reisert, DO University of New England Physician Assistant Program 20-27 JAN 20010.

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Presentation on theme: "Introduction to Renal Failure and Acute Renal Failure Jeffrey T. Reisert, DO University of New England Physician Assistant Program 20-27 JAN 20010."— Presentation transcript:

1 Introduction to Renal Failure and Acute Renal Failure Jeffrey T. Reisert, DO University of New England Physician Assistant Program JAN 20010

2 Contact Information Jeffrey T. Reisert, DO 103 Boulder Point Rd., Suite 3 Plymouth, NH (fax)

3 Genitourinary Section-Part 1 l Male urogenital disorders/Impotence l Nephrolithiasis l Urinary Tract Infections

4 Genitourinary Section-Part 2 l Introduction to Renal Failure l Acute Renal Failure l Chronic Renal Failure l Glomerulopathies (builds on prior topics) l Tubular disorders (builds on prior topics) l Hematuria l Proteinuria

5 Introduction l Two syndromes of renal failure –Acute –Chronic l Diagnosis-2 Patterns –Clinical suspect with signs and symptoms –Found incidentally on lab screen (serum or urine)

6 Agenda l General evaluation of renal failure –Definitions l Acute Renal Failure (ARF) –Etiology –Diagnosis/Evaluation –Treatment l Chronic Renal Failure (CRF) –Pathogenesis –Complications –Treatment of the complications

7 Definition-Renal failure l Spectrum of disease with declining kidney function l Decreased glomerular filtration rate l Resultant increase in nitrogenous waste products in the blood (azotemia) l Alteration in fluid an electrolytes

8 Definitions-Part II l Oliguria=Urine output (UOP) of less than 400 or 500 cc/24 hours l Anuria=No UOP l Uremia –Decreased renal function –Azotemia –Symptoms

9 Definitions-Part III l Polyuria –Excessive or frequent urination –Excessive water intake –Medical conditions? l Diabetes insipidus (Inability to concentrate urine) –Renal disease l Hematuria-blood in urine l Proteinuria-protein in urine

10 Assessment l Labs –Urine –Serum l Radiographic

11 Assessment-Labs I l Blood urea nitrogen-BUN l Creatinine l BUN/Creatinine ratio –>40 in prerenal azotemia –<20 in intrinsic renal failure l Electrolytes –Potassium especially!

12 Creatinine l Goes up quickly in ARF due to ischemia and radio contrast (complication of x-ray dye studies such as IVP, CT scans) –Peaks 3-5d after contrast –Peaks 7-10d after ischemia l Not correlative with symptoms

13 Electrolytes l Sodium reflects volume status l Potassium, phosphate, and uric acid increase

14 Assessment-Labs II l Urine output (UOP)-Monitor Is and Os l Urine sodium (reflects concentrating ability of kidneys) l Body weight l Toxin levels (i.e.: CPK-MM fraction in rhabdomyolysis)

15 Glomerular filtration rate l Collectively, the measure of renal function –If low, leads to azotemia –Can be estimated by serum creatinine –Affected by age, sex, weight, fluid status, and medical condition (illnesses, nutritional status, drugs on board, etc.) –Creatinine used as a surrogate marker as levels vary little day-to-day. l Creatinine is secreted in the proximal tubule

16 Assessment-Labs III l Creatinine clearance –ml/min/1.73 per square meter –Reflects the glomerular filtration rate –Normal –Lower in premies –Measured or Calculated methods (next slides)

17 Creatinine Clearance l [(Urine volume (ml/min) x Urine Creatinine) Divided by Serum Creatinine] x 1.73/Body Surface Area -Involves 24 hour urine test mated with serum creatinine -Fairly accurate and easy -Once a year? l Can be measured accurately by inulin (Usually in research)…..Is filtered but not reabsorbed or secreted in the renal tubules. l Also by radionuclide markers such as I125 iothalamate or EDTA (uncommon use) because……

18 Creatinine Clearance Estimates l Cockcroft-Gault equation l Men:(140-age) x (wt in kg) divided by 72 x serum creatine l For women multiply by 85% to account for smaller muscle mass (0.85 of mens estimate) l Use in hospitals with IV antibiotic dosing

19 Assessment-Labs III l Fractional excretion of Na+ –(Urinary Na+ x Plasma Creatinine x 100%) divided by (Plasma Na+ x Urinary Creatinine)

20 Azotemia l Defined as excess of urea and nitrogenous compounds in blood l Due to breakdown of protein l (Metabolism of carbohydrates and fats yields water and CO2) l If symptoms, use term uremia

21 Assessment-Radiographic l Ultrasound –Excludes obstruction –?Small kidneys--->CRF –Advantages l Non invasive l No risky contrast dye l Readily available

22 Assessment-Radiographic II l Plain x-Ray –Flat plate (?stone) –Pyelogram-Inject a dye, cleared through kidney –Retrograde pyelogram-Inject dye inside urinary collection system (intravesicular, using cystoscope) l CT –Probably better but dye risk in face of rising creatinine l MRI

23 Assessment-Wrap up l Avoid contrast in ARF or CRF not on dialysis l Biopsy may be needed in ARF for intrinsic disease l Ultrasound is easy and helpful

24 Complications of ARF l Volume overload –Decreased sodium and water excretion –Resultant weight gain, heart failure, and edema l Hyponatremia l Hypocalcemia –Paresthesias, cramps, seizures, confusion

25 Complications of ARF II l Hyperkalemia, phosphatemia, magnesemia –Potassium increases 0.5mmol/l/d in uremia –Treat hyperphosphatemia with calcium or aluminum l Metabolic acidosis l Hypertension (Moreso in CRF)

26 General treatment of ARF l Prevention!!! (Avoid nephrotoxins, diabetes control, etc.) l Reverse poisons (ETOH in ethylene glycol, bicarbonate in acidosis) l Restore fluid volume and electrolyte balance (Saline/crystalloids, colloids, blood) l Dialysis when needed (Acute if responsive (i.e.: dialyzable toxin) or in CRF) l Relieve obstruction (Easiest way to fix ARF!)

27 Acute renal failure l Definitions l Classifications/Types l Treatment

28 Defined l Renal failure of recent onset (hours to days to weeks) l Typically little symptoms –Can be found on random lab test or when suspect –If acute obstruction, symptoms (below)

29 Classification l Prerenal renal failure (Renal hypoperfusion)-55% l Renal/Parenchymal/Intrinsic-45% l Post renal (Obstructive)-5%

30 Outcome l Usually reversible l Can recover even if almost no function l Nephrology opinion?

31 Prerenal azotemia l Due to renal hypoperfusion l Usually reversible if restoring renal blood flow (RBF) l Parenchyma usually not damaged l In severe cases, ischemia/injury

32 Etiology l Hypovolemia –Fluid loss –Decreased cardiac output –Decreased systemic vascular resistance l Renal hypoperfusion –See next slides

33 Fluid or blood loss l Dehydration l GI bleeds l Burns l Osmotic diuresis (i.e.: diabetes) l Sequestration (i.e.: pancreatitis)

34 Decreased Cardiac Output l Acute MI l CHF (perhaps most common among hospital patients) l Arrhythmias l Pulmonary embolism (PE) l Mechanical ventilator

35 Altered systemic vascular resistance l Sepsis, antihypertensives, anesthetics, anaphylaxis

36 Hypovolemia l Leads to epinephrine release and subsequent vasoconstriction l Also activations of renin angiotensin system-->Vasoconstriction l Release of arginine vasopressin (AVP)

37 Renal hypoperfusion l Renal vasoconstriction due to epinephrine l ACE inhibitors l Cyclooxygenase inhibitors (i.e.: NSAIDs)- Also lead to volume depletion l Hyperviscosity syndromes

38 Hepatorenal syndrome l Cirrhosis leads to intrarenal vasoconstriction l Sodium retention l Precipitated by bleeding, paracentesis, diuretics, vasodilation, cyclooxygenase inhibitors

39 Prerenal azotemia- Assessment l Symptoms –Thirst, dizzy l Signs –Low blood pressure, tachycardia, orthostasis –Low UOP

40 Lab evaluation l Urine volume l Urine microscopy –Hyaline/bland casts due to concentrated urine

41 Intrinsic renal failure l Renovascular obstruction-Large vessel disease l Glomerular or microvascular diseases

42 Renovascular obstruction l Obstructed renal artery (Atherosclerosis, thrombus) l Renal vein obstruction (Thrombosis, external compression)

43 Glomerular diseases l Glomerulonephritis l Vasculitis l Acute tubular necrosis l Ischemic or nephrotoxic l Interstitial nephritis l Renal allograft rejection l Will expand in later section

44 Vasculitis l Kidneys are one of several very vascular organs l Hemolytic uremic syndrome l Thrombotic thrombocytopenic purpura l Disseminated intravascular coagulation l Toxemia l Accelerated HTN l Lupus l ?Include sickle cell disease

45 Acute tubular necrosis l Most susceptible area of the nephron to ischemia is the renal tubule l Ischemia from prerenal azotemia (Most common) –Prerenal azotemia is the most common cause of intrinsic renal failure l Toxin induced l Often see casts (covered later)

46 Ischemia l Hypoperfusion l Resultant injury or ischemia l Cortical necrosis l Either recover (tubules regenerate) or develop irreversible failure

47 Nephrotoxins l Radiocontrast (Intrarenal vasoconstriction) l Aminoglycosides (Decrease GFR) l Cyclosporin l Chemotherapy (Cisplatin) l Solvents (ethylene glycol) l Others

48 Endogenous nephrotoxins l Rhabdomyolysis (Due to crush, injury, ETOH) l Hemolysis (toxic to renal tubule) l Uric acid (Same thing that causes gout) l Myeloma (Plasma cell malignancy) l Hypercalcemia (Causes renal vasoconstriction)

49 Interstitial Nephritis l Allergic (Antibiotics such as beta-lactams), NSAIDs, diuretics l Infection (Bacterial-pyelonephritis, viral- CMV, Fungus-Candidiasis) l Infiltration (Lymphoma, leukemia, sarcoidosis) l Idiopathic

50 Intrinsic renal failure l Symptoms-Often none l May have history of nephrotoxin exposure l Signs-Azotemia on lab testing l Nephritic syndrome (Oliguria, edema, HTN, Urine sediment) –This suggests a glomerulonephritis or vasculitis

51 Intrinsic renal failure-Lab evaluation l Microscopy –Muddy brown casts (ischemia and nephrotoxic) –Red cell casts (acute glomerular injury or nephritis) –White cell casts (interstitial nephritis) –Eosinophilic casts (allergic nephritis) –Often no casts –Hematuria

52 Intrinsic renal failure-Lab evaluation l Proteinuria due to impaired reabsorption at the proximal tubules l Guided by etiology (i.e.: sedimentation rate if vasculitis)

53 Intrinsic renal failure- Treatment l Treat cause l Remove insult l Support, hope, and pray

54 Examples l Glucocorticoids in vasculitis and allergic interstitial nephritis) l Control blood pressure

55 Postrenal renal failure l Urinary outflow obstruction l Single kidney or urethral obstruction-- >Anuria

56 Etiologies of postrenal azotemia l Prostate disease l Neurogenic bladder –I.e.: spinal cord injuries l Anticholinergics l Blood clots l Stones l Tumor or other extrarenal obstruction

57 Postrenal signs and symptoms l Bladder distension l Abdominal pain-colic l Renal distension (ultrasound) l History of risk factors (prostate disease, stones, etc.)

58 Treatment of obstruction l Urologist l Fix plumbing l May need nephrostomy tube or suprapubic catheter placed

59 Miscellaneous treatment wrap-up l Loop diuretics may restore diuresis l Dopamine may promote sodium and water excretion l Dialysis when needed

60 Wrap-up II--Dialysis Use l ?BUN > 100 l Uremia l Hypervolemia l Hyperkalemia l Acidosis l Toxins –Multiple –Include digoxin, others

61 More…… l …to come in next slide set

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