3 Aims Anatomy Function Definitions History Examination Investigation eGFR, CKD, CreatinineHistoryExaminationInvestigationLikely Cases
4 Theme of Lecture: Basic Renal Principles Assessment of a renal patient is not that complicated, need to be methodical ..History, esp DRUGSExamination, esp fluid stateCareful analysis of dataExclusion of non-renal causes of symptomsRe-assess patients daily (fluid state)Some technical knowledge of dialysis/Tx etc
9 Normal (Basics) Normal bladder size Normal urine output 300-400 mls 2L/day (urinate 8x in day, 1x/night ≈ 200 mls)Oliguria < 400 ml/dayOligo-anuria < 200ml/dayAnuria = zero ml/day
10 Kidney Size 12 (10-14) x 6 x 3 cm, 150g, retroperitoneal How does that affect palpation?
11 Kidney Palpation Normal kidneys are not usually palpable However, in some slim women, lower pole of the right kidney can occasionally be felt during deep inspirationLarge kidneys or masses can sometimes be felt
13 Functions of Kidney Execretory (3) Metabolic/endocrine (4) Excretion of waste productsRegulation of fluid state and electrolytesAcid-base balanceMetabolic/endocrine (4)ErythropoiteinReninProstagladinsActivation of vitamin DConsequences?
14 How Hard do 2 Kidneys Work? 25% cardiac outputGFR 120 mls/min =~ 170 L /dayIe blood volume passes through kidneys 35x/day
15 What is GFR? Why Measure it? Glomerular filtration rate (GFR) is the rate (volume per unit of time) at which ultrafiltrate is formed by the glomerulus. Approximately 120 mL are formed per minuteWe use GFR to estimate renal functionGFR α 1/creatinine, ie mathematically linkedWhats wrong with creatinine?A normal creatinine concentration can occur even when the GFR has dropped by 50%So creatinine is a fairly insensitive indicator of early renal impairementCreatinine clearance and the assessment of renal function Nankivell, BJ. Aust Prescr 2001; 24: 15-7
16 CKD: GFR α 1/creatinineWhy GFR? Creatinine is rel specific but not very sensitive120 mls/minCreatinineCreat GFR/% DoPrepare ThinkGFRCreat <120 mcmol/L
18 Other Problems with Creatinine Creatinine is an imperfect filtration marker, because it is secreted by the tubular cells into the tubular lumen, especially if renal function is impairedThe amount excreted exceeds the amount filtered by 10-20%Fortunately this is balanced by a similar error in the chemical assay used which overestimates serum creatinineSo. Above 40 mls/min, the serum creatinine is accurate and good reflection of GFR. Under this level, it tends to overestimate GFRNote: some drugs (such as cimetidine or trimethoprim) have the effect of reducing tubular secretion of creatinine. This increases the serum creatinine. These drugs are not often used now
19 Can Urea Be Used?Measuring the blood urea concentration has limitations because, as well as renal impairment, it is increased by:Increased protein metabolism (raised in catabolic states, and high protein diet)DehydrationHeart failureRVDSteroidsAnd, conversely, patients with renal impairment can have relatively normal blood urea concentrations if they are grossly malnourished and not eating
20 What About Tubular Function? Although glomeruli control the GFR, damage to the tubulointerstitium is also an important predictor of GFR and progression towards renal failureRenal tubules make up 95% of the renal mass, do the bulk of the metabolic work and modify the ultrafiltrate into urineThey control a number of kidney functions including acid-base balance, sodium excretion, urine concentration or dilution, water balance, potassium excretion and small molecule metabolism (such as insulin clearance)Measurement of tubular function is impractical for daily clinical use, so we usually use the GFR to assess renal function
30 Anuria V rare Only 3 causes Obstruction Vascular catastrophe Severe acute glomerulonephritis
31 Macroscopic Haematuria Recurrent visible haematuriaAge > 40 years, presume neoplasiaSmokingUTI/stones or other urological disordersOccupational exposure to chemicals or dyesPelvic irradiationExcessive analgesic useCyclophosphamide
37 General Examination “Observation is 90% of Medicine” Prof Dan Hoyte Walk into the room (DM?)Face (eg SCCs (Tx-related), SLE)Hands (radial/brachial fistula)Skin (excoriation)Uraemic frost = deposition of white/tan urea crystals on the skin after sweat evaporation (v rare)Pulse (sign of LVF)
38 Cardiorespiratory = Limited cardiorespiratory BP BP BP JVP JVP JVP Auscultation (pericardial rub)Pulmonary oedema (± pleural rub)Sacral oedemaLeg oedema
39 GI+ Observation (state the obvious, eg .. ) Light palpation Deep palpationLiverSpleenKidneys + BladderBruits (epigastric, femoral)
40 Technical Signs (relating to HD, PD and Tx) Dialysis catheterAVF (radial/brachial)PD catheterUrinary catheter/nephrostomyTx scarsTx-related problems (eg NODAT, BCC/SCC)
43 Urine - MSU <5 WC <25 RC No casts (esp red cell) No growth “Mixed growth”?.. which UTIs to investigate?
44 Dipstick – Blood, WC, Glucose Haematuria 2+ (ie microscopic) = ?80% sensitive, 65-99% specificNeed? ..Leucocytes 1+ ≠ UTI (need? ..)Nitrites - produced when bacteria reduce urinary nitrates derived from amino acid metabolismGlucose - usually appears in urine when serum glucose increases to > 10 mmol/L) and renal function is normalUseful screening test, not diagnostic
45 Microscopic Haematuria – Who to Investigate If associated with:Stage 4 or 5 CKDWorsening CKDSignificant proteinuria (PCR ≥ 50, ACR ≥ 30 mg/mmol (≥ 0.5 g/24h))Uncontrolled BP ≥ 140/90 mmHg (3+ drugs)Or unexplained microhaematuria following urological assessment where no cause was found
46 Dipstick - ProteinDetects albumin but not other proteins, such as immunoglobulin light chains (consequence? ..)Like creatinine, his test is specific(ish), but not very sensitive for the detection of proteinuriaIe, it becomes positive (1+) only when protein excretion exceeds 0.5 g/L (upto 0.2g/L is normal). This is quite a lotHence, concept of microalbuminuria developed
47 Dipstick – Protein (Other Problems) Semi-quantitative categories on the dipsticks should be used with caution (esp ‘proteinuria’ = albuminuria)Only a rough guide sinceAlbumin conc varies with urine volume, ieDilute urine underestimates degree of proteinuriaConcentrated urine may show ‘3+ proteinuria’Different products
48 Proteinuria (quantification) Eat 80g /dayHeavy proteinuria is the hallmark of glomerular diseaseNormal = <0.2 g/L, ie <0.4g/day, if 2L urineOr PCR <15 mg/mmol (ACR <3 mg/mmol)PCR/100 ≈ g/24hACR 3-30 mg/mmol = microalbuminuriaDipstick specific but not very sensitive (like creatinine)Dipstick g/L g/24h PCR (ACR) 0 <0.2 <0.4g <15 (<3) Trace (ACR 30)(ACR 70) lowmod nephrotic rangehigh nephroticv high
60 Investigation – Specialised (Renal Biopsy) AKI, normal sized kidneys,no obvious cause = biopsyCKD, normal sized kidneys,Proteinuria (>1g/L = 2g/24h = ‘nephrotic range’), no obvious causeTransplant dysfunction
61 Investigation – Specialised (Renal Angiogram) Rarely performed (now always with a review to intervention)Hypertension (RVD)with poor BP control on 4 drugs‘Flash’ pulmonary oedemaAKI in single (or single effective kidney)Fibromuscular dysplasia
63 Case One 47y year old Asian male Presents 2 wks SOB and SOA, O/E fluid overloadDM2 2 yearsIHD/CCFSerum albumin 40 g/LUrinary protein 0.15 g/L1. Other information?2. Diagnosis?
64 Case Two 35y old female Investigated for BP Creat 68 mcmol/L FH grandfather died of kidney problemO/E large liver? 2 large kidneys? (both?)1. Next investigation?2. Diagnosis?
65 Case Three 23 year old female 2 weeks SOA O/E SOA Serum albumin 25 g/L Urinary protein 4.3 g/LCreat 87 mcmol/L1. Renal syndrome?2. Diagnosis?
66 Case Four 67 year old Asian male PMH DM2 (20y), TURP C/O 6 mths SOB, O/E fluid overload, R fem bruitCreat 465 mcmol/L (198 mcmol/L, 2012)Urinary protein 0.1 g/L1. Next investigation?2. Diagnosis?
67 Case Five 87y old male C/O tiredness ESKF (2009) On CAPD (4 x 2L bags a day)Creat 877 mcmol/L and stable1. Other information?2. Diagnosis?
68 SummaryAssessment of a Renal Patient is not that complicated, need to be methodical ..History, esp DRUGSExamination, esp fluid stateCareful analysis of dataExclusion of non-renal causes of symptomsRe-assess patients daily (fluid state)Some technical knowledge of dialysis/Tx etc