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Back to Basics Nephrology 2016

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1 Back to Basics Nephrology 2016
Answers to the questions that we will cover during the session are at the end of this file. If you plan to attend the session, please wait till after to look at the answers. The link to the quiz questions will be active at the time of the session (More information for many slides can be found in the notes section of this PPT)

2 Back to Basics Nephrology 2016
This session is a brief review of the top renal issues that are likely to be tested on exams Some extra slides are included at the end of this PPT file. They are not thought to be required study material.


4 Outline Renal failure: Acute Chronic Measuring GFR
Electrolyte and acid-base disorders: Sodium disorders Hyperkalemia Hypomagnesemia and hypophosphatemia Acid-Base disorders Glomerular disorders: Proteinuria Hematuria

5 Renal Failure Acute Chronic Measuring GFR


7 Urine values compatible with pre-renal failure:
Click here with PowerPoint in slide show mode Quiz Question 1 Urine values compatible with pre-renal failure: Osm < 300 mosm/L RBC casts Na+ < 20 mmol/L Fex Na+ > 2%

8 ARF Pre renal and ATN most common causes (quoted at 70% of cases of ARF) DDx: Pre Renal Intra Renal Post Renal The term AKI, (Acute Kidney Injury), is being used in clinical research settings in place of ARF, but not on the MCC I would suggest NOT even thinking of memorizing the AKI criteria, but if you are really interested in them they are on the last slide of this PPT file.

9 Urine: Pre-Renal vs. Renal Assessment of Function
U Na U Osm Fe Na Pre-Renal ATN < 20 > 500 < 1% > 40 < 350 > 2% U/P Na U/P Cr These values have been validated since the 1970s The UNa, Uosm require that the patient be oliguric The FeNa is much more predictive if the patient is oliguric Fe Na = X 100 Pigmented granular casts found in up to 70% of cases of ATN

10 Urine: Pre-Renal vs. Renal Assessment of Function
Fe Urea Pre-Renal ATN < 35 U/P Ur U/P Cr Fe Urea = X 100 > 55 Personally, my take on what is published is that the FeUrea is not predictive for prerenal ARF FeUrea might be useful to Dx pre renal ARF in those who received diuretics…but not all studies support its use.

11 ARF Investigations: Pre Renal: Urine tests as noted and responds to volume Intra-Renal: look for GN, interstitial nephritis as well as ATN Post Renal: Imaging showing bilateral hydronephrosis is highly specific for obstruction causing ARF Although decreased intravascular volume can result in both pre renal ARF and in ATN the way to look at it is as follows: Pre renal ARF means no damage has been done to the nephrons, but the kidneys are not receiving the amount of plasma they need to be able to eliminate the amount of solute produced per day. Once the kidneys are supplied with this volume, they will be able to do their normal job. Ischemic ATN means that renal blood flow has been so low that ischemic damage has occurred to nephrons and even if renal blood flow is restored to normal, the kidneys will not resume normal function, typically for one to 3 weeks.

12 Dialysis: Who Needs It? If cannot control these by other means:
Hyperkalemia Pulmonary edema Acidosis Uremia (GFR < 8-12% for CRF depending on symptoms) NB in practice almost always, volume or hyperkalemia are the usual reasons to start dialysis in ARF In ARF, dialysis has usually been started for volume or K before any uremic indications happen

13 Dialysis: Who Needs It? Hemodialysis is also used for intoxications with: ASA Li Alcohols: i.e. methanol, ethylene glycol Sometimes theophylline


15 K/DOQI Classification of Chronic Kidney Disease
Stage GFR (≥3mo) Description (ml/min/1.73m2)  Damage with normal GFR Mild  GFR Moderate  GFR Severely  GFR < Kidney Failure This definition of CKD is now used by most nephrologists. Clinically, creatinine based estimates of GFR are not accurate above 60 ml/min/1.73m2 so we can only talk about stages 3,4 and 5, (and the formulae are not very good for GFR below 15). Approximately 500,000 Canadians have stage 3 CKD; most of these will not need renal replacement therapy

16 In this K/DOQI staging, “kidney damage” means:
Persistent proteinuria Persistent glomerular hematuria Structural abnormality: such as PCKD, reflux nephropathy The presence of proteinuria is a very important marker that predicts future decrease in GFR and cardiovascular mortality

Diagnosis: Acute vs. chronic: Small kidneys on U/S or unenhanced imaging mean CKD Diabetic CKD may still have normal sized kidneys Very high PTH without hypercalcemia suggestive of secondary, (CKD) cause of increased PTH Some other causes of CKD and normal sized kidneys are myeloma, amyloid, and polycystic kidney disease

Common causes of CKD: Diabetic nephropathy Vascular disease GN PKD GN, (glomerulonephritis) here means glomerular disease due to primary, (idiopathic), causes other than secondary disease such as diabetic nephropathy.

Causes of CKD: Best to divide as proteinuric or non-proteinuric CKD Proteinuric is much more likely to have deterioration in GFR and higher cardiovascular morbidity and mortality

Treatment Rule out acute changes: Pre Renal Intra Renal Post Renal Rule out acute on chronic decrease in GFR using the ARF breakdown of causes. Especially remember: ACEI, ARBs, diuretics and NSAIDs with hypovolemia can cause acute decrease in GFR

Treatment Delay progression: Treat underlying disease i.e. good glucose control for DM BP control to 140/90, (the current target); 130/80 for diabetics ACEI or ARB has extra benefit for proteinuric CKD Lower protein diet…maybe BP target guidelines are constantly changing. These are from 2014 Canadian Hypertension Education Program.

Treatment of the consequences of decreased GFR: PO4: decrease dietary intake PO4 binders such as CaCO3 Hypocalcemia: CaCO3, 1,25 OH D3 Hyperphosphatemia and hypocalcemia typically does not occur until GFR falls below 30 ml/min Typical dietary sources of PO4 are dairy, meat, colas With diet alone, it is difficult to keep PO4 normal as GFR declines toward the need for renal replacement and that is why CaCO3, (and other non calcium substances such as sevalemer), is used to bind PO4 in the GI tract and prevent it from being absorbed. NB: there is some concern that the use of CaCO3 may result in calcific blood vessel changes. Active 1,25 OH D3 is 1 hydroxylated in the kidney, 25 hydroxylated in the liver

Treatment of the consequences of decreased GFR: Anemia: Erythropoetin current target Hb Anemia in CKD does not usually occur till GFR is less than 30 ml/min Studies have shown increased mortality with targeting Hb closer to normal values and opinion re: target Hb varies

Uremic Complications: Major: Pericarditis Encephalopathy Platelet dysfunction Uremic complications that are not life threatening include: nausea, vomiting, anorexia, prutitis

25 Measuring GFR

26 ASSESSMENT OF GFR: Creatinine concentration alone is not the best way to assess GFR

Creatinine clearance formula: 24 hour urine creatinine clearance is not commonly done in 2015 Need a Steady State for these to be valid

28 ASSESSMENT OF GFR: Cockroft-Gault estimated Creatinine clearance:
(140-age) x Kg x x .85 for women Creat Need a Steady State for these to be valid

29 MDRD eGFR Need a Steady State for these to be valid
GFR, in mL/min per 1.73 m2   = (170 x (PCr [mg/dL])exp[-0.999]) x (Age exp[-0.176]) x ((Surea [mg/dL])exp[-0.170]) x ((Albumin [g/dL])exp[+0.318]) where SUrea is the serum urea nitrogen concentration; and exp is the exponential. The value obtained must be multiplied by if the patient is female or by if the patient is black. Simplified: GFR, in mL/min per 1.73 m2 = 186.3 x ((serum creatinine) exp[-1.154]) x (Age exp[-0.203]) x (0.742 if female) x (1.21 if African American) There are apps and online sites that do this calculation Need a Steady State for these to be valid

30 Limitations of GFR estimates: Not reliable for:
extremes of weight or different body composition such as post amputation, paraplegia acute changes in GFR use in pregnancy eGFR greater than 60ml/min/1.73m2 As previously noted, creatinine based estimates of GFR are not accurate when calculation gives a value greater than 60ml/min in which case GFR is assumed to be normal unless there are strong risk factors for renal disease present. A nuclear GFR would be needed to measure GFR more accurately in the 60 to 90 ml/min range, for example, prior to nephrectomy in kidney donation. Even nuclear GFR may not be perfect.

31 Electrolyte and Acid-Base Disorders
Sodium disorders Hyperkalemia Hypomagnesemia and hypophosphatemia Acid-Base disorders

32 Na+ Disorders

33 Hyponatremia Pseudo: If total osmolality is high: hyperglycemia/ mannitol If total osmolality is normal, could be due to very high serum lipoprotein or protein The normal osmolality hyponatremia will happen only if Na is measured by the lab in a certain way, for example a flame photometer

34 Hyponatremia Volume status:
Hypovolemic: high ADH despite low plasma osmolality High total volume: CHF/ cirrhosis have decreased effective circulating volume and high ADH despite low plasma osmolality Since we cannot get lab measurement of ADH, we use urine osmolality as a proxy. High urine osmolality tells us there is ADH present

35 Hyponatremia Volume status: If volume status appears normal:
If urine osmolality is low: normal response to too much water intake…”psychogenic polydipsia” If urine osmolality is high: inappropriate ADH If you see a hypo osmotic patient with a very low urine Osm of 50 mOsm/L, that patient has lowered their urine Osm appropriately in response to the hypo osmotic plasma and a high water intake is the likely problem Normally, people can drink 10 to 15 L of water per day without causing hypo Osmotic plasma, but I would not recommend anyone try this

36 Hyponatremia Treatment: Hypovolemic: Decreased effective volume:
Replace volume Decreased effective volume: Improve cardiac output if possible Water restrict SIADH:

37 Hyponatremia Treatment: Rate of correction of Na:
Not more than 8-10 mmol in first 24 h and not more than 18 mmol over first 48 h of treatment Or Central Pontine Myelinosis may occur There is some reason, based on animal models, to think that if the Na has corrected too quickly, attempts to lower it back down with D5W and or ADH would have some benefit. Some of those at most risk for CPM are those with hypokalemia, alcoholism and females

38 Hypernatremia

39 Hypernatremia Usually decreased total body water:
GI losses such as non secretory diarrhea Renal losses such as osmotic diuresis or lack of ADH secretion or lack of tubular effect of ADH Lack of access to or ability to drink water Rarely from massive Na ingestion po or IV hypertonic saline Non secretory diarrhea: viral, bacterial, lactulose

40 Hypernatremia No matter where the water loss occurs, thirst normally prevents hypernatremia Need a combination of lack of thirst and loss of water or hypotonic fluid to result in hypernatremia

41 Hypernatremia Management:
Administration of hypotonic fluid and treating the underlying condition Calculation of free water deficit gives an idea of how much water is needed, but need to check serum Na frequently to see if remain on target. Free water deficit (in litres) = Total body water x [(current serum Na/140) -1]

42 Hypernatremia Management:
For chronic hypernatremia, (present for longer than 48 hours), do not correct more than 10 mmol/L per 24 hours, (this pertains most to pediatric patients, to prevent cerebral edema) For acute hypernatremia lower Na to close to normal within 24 hours Calculation of free water deficit gives an idea of how much water is needed, but need to check serum Na frequently to see if remain on target. Free water deficit (in litres) = Total body water x [(current serum Na/140) -1]

43 Hyperkalemia

44 Hyperkalemia Is it Real or Not: Hemolysis of sample Very high WBC, PLT
Prolonged tourniquet time ECG changes such as peaked T waves, then flattened P waves and prolonged QRS may be seen with true hyperkalemia but are not always present with true hyperkalemia.

45 Hyperkalemia Shift of K from cells: Insulin lack
High plasma osmolality Acidosis Beta blockers in massive doses

46 Hyperkalemia Increased total body K: Decreased GFR plus:
High diet K KCl supplements ACEI/ARB K sparing diuretics Decreased Tubular K secretion

47 TTKG? No longer used Second last slide of this PPT has information for those who still want to read about it. “Trans tubular potassium gradient” This formula relates to the basic physiology of K secretion from principal cells. In the past was interesting to use it clinically but it is no longer regarded as being helpful.

48 Hyperkalemia Treatment IV Ca Temporarily shift K into cells: Remove K
Insulin and glucose Beta 2 agonists (not as reliable as insulin) HCO3 if acidosis present Remove K For modest hyperkalemia, many use kayexalate po given with a non absorbable sugar such as lactulose or sorbitol or just water. Others argue that there is little evidence that it works. If kayexalate is given as an enema, do not use lactulose or sorbitol as these can damage colonic mucosa.

49 Hypomagnesemia and Hypophosphatemia

50 Magnesium Hypomagnesemia: GI loss/lack of dietary Mg Renal loss:
Diuretics Toxins esp cisplatin

51 Is hypoMg due to renal loss?
Fractional excretion of Mg: FEMg= UMg/(0.7xPMg) X 100 UCr/PCr Should be below 2% if Mg loss is extrarenal

52 Consequences of Hypomagnesemia
Severe: Tetany, ventricular arrhythmias Also due to co-existent hypocalcemia Hypocalcemia Hypokalemia TRIVIA: Hypomagnesemia causes hypocalcemia mostly by causing hypo responsiveness to PTH

53 Hypophosphatemia Shift: Refeeding with insulin release
Hungry bones post parathyroidectomy Resp alkalosis

54 Hypophosphatemia Decreased total body PO4 Renal loss GI loss
Decreased intake, (rare) Vitamin D deficiency Renal loss Diuretics, primary hyperparathyroidism Fanconi Syndrome? Very rare renal tubular loss of: PO4, amino acids, glucose, HCO3- Fanconi syndrome appears more often on exams than in real life. In children usual cause is rare autosomal recessive disorder: cystinosis In adults rarely caused by myeloma

55 Acid-Base Disorders

56 Quiz Question 2 Most likely cause of Na 140 Cl 110 HCO3 10 : RTA
serum albumin 20 resp alkalosis ketoacidosis

57 Acid-Base Approach to: Resp or metabolic Compensated or not
If metabolic: anion gap or not Anion gap = Na - (Cl + HCO3) Remember that full compensation does not result in normal pH except in chronic respiratory alkalosis and perhaps chronic respiratory acidosis. So if it looks like predominately a metabolic acidosis or metabolic alkalosis, but if the pH is normal, there is likely another acid base disorder present

58 Acid-Base Increased anion Gap acidosis: “MUDPILES”: Methanol Uremia
Diabetic/alcoholic ketosis Paraldehyde Isopropyl alcohol Lactic acid Ethylene glycol Salicylate

59 Acid-Base Metabolic acidosis with normal serum anion gap can be due to: 1) GI losses of HCO3 2) Renal tubular acidosis

60 Renal Tubular Acidosis
Hopefully will not need this. Normal renal response to acidosis is to increase ammoniagenesis and more NH4+ will be found in the urine For those with close to normal GFR, the “urine anion gap” is a way to estimate urinary NH4+ Urine anion gap = urine (Na+ + K+ – Cl-) If it is positive there is decreased NH4+ production and likely a renal component to the acidosis Since NH4+ is positively charged, each molecule of NH4+ must be accompanied by a negative charge which is almost always Cl-. In the case of a normal renal response to acidosis: A large amount of Cl- will accompany a large amount of NH4+ Since NH4+ is not measured, the high Cl- will give a negative answer to the equation

61 Glomerular disease Proteinuria Hematuria

62 Proteinuria

63 Proteinuria Albumin vs. other protein Dipstick tests albumin
Light chain is not detected by dipstick

64 PROTEINURIA Quantitative: 24 hour collection
ACR: random albumin to creatinine ratio PCR: random protein to creatinine ratio Many use ACR and PCR instead of 24 h urine for urinary protein quantification because 24h collection can be inaccurate and is cumbersome, but these ratios may also be unreliable.

65 PROTEINURIA Microalbuminuria: less than dipstick albumin
Can use albumin to creatinine ratio on random urine sample… best done with morning urine sample

66 Random Urine 24h Urine ACR (g/mol) Albumin (mg/24h) PCR Protein Normal
F <2.0 <2.8 <30 <20 <200 Micro-albuminuria 2.0-30 2.8-30 30-300 Macro-albuminuria >30 >300 In practise, most nephrologists are of the opinion that microalbuminuria in the absence of diabetes does not indicate significant renal disease On the other hand, microalbuminuria is a marker for cardiovascular mortality in population based studies

67 PROTEINURIA Is there persistent proteinuria or transient?
Need to rule out transient proteinuria as it is common and does not usually develop into anything. Orthostatic proteinuria, (proteinuria only when upright, no significant protein when supine), can occur in young people, (<25 years old), and is also not usually indicative of any renal disease.

68 Quiz Question 3 The definition of nephrotic syndrome includes: :
Hypolipidemia Lipiduria 24 hr protein ≥2g hypertension

69 Nephrotic Syndrome Definition: > 3 g proteinuria per day Edema
Hypoalbuminemia Hyperlipidemia and lipiduria are also usually present

70 Nephrotic Syndrome Causes: Secondary: DM, lupus Primary:
Minimal change disease FSGS Membranous nephropathy Nephrotic Syndrome tells you that you are dealing with glomerular disease

71 Nephrotic Syndrome Complications: Edema Hyperlipidemia
Thrombosis…esp with membranous GN and very low serum albumin Most do not prophylactically anticoagulate for membranous GN In those with membranous nephropathy who have a sudden severe and unexpected decrease in GFR, many experts think renal vein thrombosis should be ruled out usually with doppler studies.

72 Nephrotic Syndrome Treatment: Treat cause if possible
Treat edema, lipids Try to decrease proteinuria General measures to decrease proteinuria would be: BP control, use of ACE or ARB

73 Hematuria

74 Hematuria Significance: ≥3 RBC's per hpf DDx: Is it glomerular or not?
RBC casts Dysmorphic RBCs in urine Coinciding albuminuria may indicate glomerular disease

75 Hematuria Other investigation: Imaging of kidneys Serum creatinine
Age over rule out urologic bleeding, i.e. urine cytology and referral for cystoscopy Also need to rule out TCC of collecting system with risk factors such as smoking, previous cyclophoshamide

76 Hematuria For glomerular hematuria without proteinuria DDx includes:
IgA nephropathy Thin GBM disease Hereditary nephritis IgA is not usually inherited. If proteinuria, hypertension or decreased GFR is present will likely be future deterioration in GFR. Thin GBM disease is often autosomal dominant. Usually does not cause any drop in GFR but does in some families. Hereditary nephritis is most often X-linked recessive and called Alport syndrome: affected males usually need renal replacement therapy by age 50. Associations are sensorineural deafness, eye changes.

77 Questions and Answers

78 What are strategies shown to delay the progression of CKD?
ACE inhibitors and possibly protein restriction in maybe some circumstances ? What are strategies shown to delay the progression of CKD?

79 The formula for estimated creatinine clearance
? (140-age) x Kg x x .85 for women Creat

80 What are lab values compatible
Serum Na+ 120, Serum Osm 250, Urine Osm 50 ? What are lab values compatible With polydipsia?

81 ACEIs, ARBs, NSAIDs, Spironolactone
? What are causes of hyperkalemia in patients with stable GFR of 30 ml/min?

82 The two most common causes of Hypomagnesemia
? What are GI losses and renal tubular losses of Mg?

83 urine dip negative for protein,
24 hour urine 2g protein ? What is the presence of light chain proteinuria?

84 What test result is highly specific for glomerular hematuria?
RBC casts ? What test result is highly specific for glomerular hematuria?

85 Extra Slides

86 TTKG? Requirements: [urine K+  (urine osmol/serum osmol)] serum K+
Urine osmolality > 300 Urine Na+ > 25 Reasonable GFR TTKG = U/P K+/U/P Osm [urine K+  (urine osmol/serum osmol)] “Trans tubular potassium gradient” This formula relates to the basic physiology of K secretion from principal cells. It is interesting to use it clinically if GFR is relatively normal but it is no longer regarded as being valid or helpful. serum K+ <7, esp < 5 = hypoaldosteronism

87 AKI Even the term ‘AKI’ should not be on the exam…..

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