Kidney disorders, Laboratory Investigation and Renal Function Tests

Kidney Disorders, Laboratory Investigation and Renal Function

Tests

Prepared By:V.Madhukar

Content• Kidneys & Functions • Presenting Features of Renal Disease• Kidney Failure/ESRD

– Risk factors– Symptoms– Treatment

• Hemodialysis• Peritoneal Dialysis

• Common Kidney Diseases• Laboratory Investigation of Kidney Disorders Urine Examination -routine -microscopic Renal Function Test -Glomerular Function tests -Renal blood flow test Renal Biopsy• References

The Kidneys

• A pair of bean-shaped organs located at the posterior wall of the abdomen

• Dimensions– 11 cm long, 6 cm wide and 3 cm thick– weighs about 160g

The Kidneys

• Made up of functioning units called nephrons

Nephron

GlomerulusTubules

Functions• Removal of waste and excess water from

body; Regulation of fluid, electrolyte and acid-base balance

Functions

• Normal kidneys release several hormones– Renin (regulates blood pressure)– Erythropoietin (stimulates production of red blood

cells)– Activated form of Vitamin D (maintain normal

bone structure)

Presenting features of renal disease

1. Dysuria - urethritis(inflammation of urethra) and

cystitis(inflammation of bladder due to infection)

- inflammation of vagina and penis2. Polyuria and nocturia(increased urine flow at

night) - > 3 L/ day - solute diuresis, diabetes insipidus, CRF(Chronic

Renal Failure)

3. Oliguria - Decreased urinary output i.e. < 300 ml/ day - hypotension, hypovolaemia(decreased

volume of circulating blood in body) - intrinsic renal disease - urinary tract obstruction

4. Haematuria. - blood in the urine, arises anywhere in renal

tract - micturition- urethral disease- tendency to

urinate

5. Renal pain.- dull constant pain in the loin.- renal obstruction, acute pyelonephritis, acute

nephritic syndrome, polycystic kidney, renal infart.6.Ureteric colic.- Severe loin pain, waxes and wanes, a/w fever,

vomiting, radiate to abdomen, groin, upper thigh.- Renal calculus, clot.

Kidney Failure or End-stage Renal Disease (ESRD)

• Occurs when the kidneys do not function properly or sufficiently, resulting in the accumulation of waste products and toxic materials– may cause permanent and irreversible damage to

body cells, tissues and organs– kidneys that function <20% of required capacity

• need renal replacement therapy

Risk Factors

• Chronic diseases• Inflammatory diseases• Blockage of urinary collecting system• Chronic infections• Rare genetic disorders

Symptoms• Decreased urination• Blood in the urine• Nausea and vomiting• Swollen hands and ankles• Puffiness around the eyes• Itching• Sleep disturbances• High blood pressure• Loss of appetite

Treatment of Kidney Failure

Blood creatinine rises to 900 µmol/ L• Dialysis

– Hemodialysis– Peritoneal Dialysis

• Transplant– the best means of treatment

Hemodialysis

• A process by which excess waste products and water are removed from the blood

• Requires an access to the patient's blood stream and the use of a haemodialysis machine

Hemodialysis

• Vascular Access– arterio-venous (AV) fistula– AV graft

Hemodialysis

• AV grafts

Hemodialysis

• 3 times a week (on alternate days) for 3 to 5 or more hours each visit

Hemodialysis

• “Washout Syndrome”– feels weak, tremulous, extreme fatigue– syndrome may begin toward the end of treatment

or minutes following the treatment– may last 30 minutes or 12-14 hours in a

dissipating form

Hemodialysis

• Advantages– Staff performs treatment in the dialysis centre– Three treatments per week in the dialysis centre– Permanent internal access required – Regular contact with people in the centre

Hemodialysis

• Disadvantages– Requires travel to a dialysis centre – Fixed treatment schedule – Two needle sticks for each treatment; tie onto a

machine and cannot move about during treatment

– Diet and fluid intake restriction

Peritoneal Dialysis• Dialysis solution flow into the peritoneal

(abdominal) cavity through a catheter• Petrionuem acts as a filter

Peritoneal Dialysis

• 2 forms– CAPD (Continuous Ambulatory Peritoneal

Dialysis)• 4 exchanges during the day, 45 min each

– APD (Automated Peritoneal Dialysis)• exchanges are performed by the machine during the

night while the patient is asleep

Peritoneal Dialysis

• Advantages– Patient's involvement in self-care – Control over schedule– Less diet & fluid restriction– More steady physical condition as it provides

slow, continuous therapy – Most similar to original kidneys. Can be done at

night as in automated peritoneal dialysis – Provide less severe cardiovascular instabilities in

patients with underlying heart disease

Peritoneal Dialysis

• Disadvantages– Four exchanges per day– Permanent external catheter– Change of body image– Some risks of infection– If on automated peritoneal dialysis, one will be tie

onto a machine in the night– Storage space is needed for supplies

Kidney Transplant

• A kidney from either a living related or a brain dead person is removed and surgically placed into the kidney failure patient.

• Not all kidney failure patients are fit to undergo transplantation. – Medication to suppress their immunity given for

the transplant may worsen their general health

Kidney Transplant

• Advantages– Absence of need for frequent dialysis treatment– Better quality of life– Better health– Reduced medical cost after first year– No diet and fluid intake restriction– Provide less severe cardiovascular instabilities in

patients with underlying heart disease

Kidney Transplant

• Disadvantages– Need for frequent physician visits – Pain, discomfort of surgery – Risk of transplant rejection – Prone to infections – On lifelong medications

Common Kidney DiseasesPolycystic Kidney Disease

Hypertensive Nephrosclerosis Glomerulonephritis / Glomerulosclerosis

Urinary Tract Infection (UTI) Kidney Stones

Diabetic Kidney DiseaseAnalgesic nephropathy

Polycystic Kidney Disease

• Genetically acquired • 2 forms - dominant and recessive • In the dominant PKD form, one parent has the

disease and passes it to the child. The chance of passing the gene to the offspring is 50%.

• Cysts are abnormal pouches containing fluid. Eventually the cysts replace normal kidney tissue -> suffers ESRD


Signs and Symptoms• Dull pain at the side of the abdomen and back • Blood in the urine • Frequent urine tract infection • High blood pressure (often before cysts appear) • Upper abdominal discomfort (liver and pancreatic cysts)


Treatment• Blood pressure - controlled and treated• Kidney failure - supportive therapy until end-

stage is reached when dialysis or transplantation is then required

• Urine tract infection - treatment with antibiotics

• Pain - analgesics are used. Alternatively, surgery to shrink or resect the cysts.

Hypertensive Nephrosclerosis

• Poorly controlled high blood pressure (hypertension) can lead to kidney failure– Thickening of blood vessels


Signs and Symptoms• Headache • Giddiness (sometimes related to posture) • Neck discomfort • Easily tired • Nauseous and/or vomiting • Protein in urine


Treatment• Medications to control blood pressure (anti-

hypertensive) • Lowering of dietary salt (2g/day) • Exercise regularly

Glomerulonephritis / Glomerulosclerosis

• Glomerulonephritis - An inflammatory condition that affects predominantly the glomeruli.

• Causes– IgA nephropathy– Streptococcus bacteria– Autoimmune

• Glomerulosclerosis - scarring of the glomeruli


Signs and Symptoms• Blood or protein in urine• Frothy urine (signifying protein in urine) • Dark or pink-coloured urine • Leg swelling • Systemic disease like diabetes or autoimmune

disease will have systemic manifestations, e.g. weight loss, arthritis, or skin rash


TreatmentSpecific• Suppression of inflammation may be achieved

by certain medications (eg steroids). General• Medications to decrease excretion of urinary

protein • Control of blood pressure• Dietary modifications

Urinary Tract Infection (UTI)

• Disease of the urinary tract– Infection occurs when microorganisms attach

themselves to the urethra and begins to multiply.• May lead to infection of the kidneys

(pyelonephritis) and cause permanent kidney damage, if left untreated.

• Women are especially prone to get urinary tract infection.


• Conditions that increases risk of UTI– Diabetes– Situations where a urine catheter is needed– Abnormalities of the urinary tract– Obstructed urine flow (large prostate or stone)– Being pregnant

Urinary Tract Infection (UTI)Signs and Symptoms• Painful urination (burning sensation) • Hot and foul smelling urine • Blood in urine • Fever (sometimes with chills) • Painful lower abdomen • Increased urgency/frequency of wanting to

pass urine • Nausea and/or vomiting


Treatment• Appropriate antibiotics • Drink plenty of water

Kidney Stones• Start as salt/chemical crystals that precipitate

out from urine• Occurs when substance in urine that prevents

crystalization are ineffective

Kidney Stones

• Various forms of kidney stones - the most common is calcium in combination with either phosphate or oxalate

• More common in – Males– 20-40 yo

Kidney Stones

Signs and Symptoms• Extreme pain at the site where the stone is

causing the irritation• Blood in the urine (abrasion along the urinary

tract as the stone travels) • Painful and/or difficult urination • Unable to pass urine if the stone is large

enough to obstruct the outlet completely

Kidney Stones

Treatment• With plenty of water, most stones can pass

through if small • Pain-killers (as prescribed by the doctor) • Some medications may help 'breakdown' larger

stone • Shockwave therapy (F-SWL) to break the stone • Surgical intervention - cystoscopy or open surgery

Diabetic Kidney Disease

• Common in chronic and poorly controlled diabetics

• Diabetes damages blood vessels in the kidneys• Occurs in both types of diabetes • Occurrence of high blood pressure in diabetics

is a strong predictor for diabetic nephropathy • Most common cause of ESRD in many

developed countries

Diabetic Kidney DiseaseSigns and Symptoms• Frothy urine (signifying protein in urine) • Leg swelling (worse after walking/standing) • High blood pressure • Itching • Nausea and/or vomiting • Losing weight • Lethargy • Increased need to urinate at night

Diabetic Kidney Disease

Treatment• Good control of diabetes• Good control of blood pressure (aiming for <

130/85 or lower in younger patients) • Medications to decrease protein excretion and

preserve the function of kidneys • Lower protein diet• Treat any urine tract infection (which is

common in diabetics)

Analgesic Nephropathy

• Chronic kidney disease that occurs when there is a long period of painkiller/s ingestion (usually years)

• Associated with conditions which require constant need for painkiller medications

• May lead to ESRD


Signs and Symptoms• Blood in the urine• Protein in the urine• Signs and symptoms related to kidney failure

such as nausea, vomiting, lethargy, swelling, and poor appetite.


Treatment• Avoid long-term consumption of analgesics• Those already with kidney disease of other

kinds should certainly refrain from harmful analgesics as much as possible.

Laboratory Investigation of Kidney Disorders

• Urine Examination -routine -microscopic• Renal Function Test -Glomerular Function tests -Renal blood flow test• Renal Biopsy• Imaging

Urine Examination

• Sample Collection -the 1st morning specimen is preferred -collected in a clean container -for culture, the specimen should be collected in a

sterile container & sent to the lab immediately, where it should be plated within 15minutes or stored in a refrigerator at 4 degree Celsius. Bacteria multiply rapidly at room temp., which may give false positive results.

Methods of Urine Collection• Midstream urine : a clean-catch midstream specimen is widely

used. In older children who can cooperate, midstream specimen is obtained after proper local cleaning .The initial part of urine is discarded.

• Bag collection : in neonates & infants, urine can be collected in sterile bags. Not used for microscopic exam.

• Bladder catheterisation : a urine specimen can also be safely obtained, in infants, by strict bladder catheterisation but requires some skills & experience.

• Suprapubic bladder aspiration : the only reliable way to obtain reliable urine specimen in neonates & young infants. In children <2 yrs of age it is most suitable method for a definitive diagnosis of UTI

• SPECIFIC GRAVITY : full term infants have a limited concentrating ability with a maximum sp.gravity of 1.021 – 1.025. It is measured with clinical Hydrometer. Increase in sp.gravity may be ass. with dehydration, diarrhoea, emesis, excessive sweating etc. while decrease in sp.gravity may be ass. with renal failure, interstitial nephritis & excessive fluid

intake.• pH : tested with pH meter. UTI with urea splitting organisms

make urine highly Alkaline. Normal pH ranges from 4.6 -8.0. In fasting, the concentrated urine sample is highly Acidic

-A high urine may be due to RTA(Renal Tubular Acidosis type I),UTI, Vomitng & a low urinary pH may be due to DKA(Diabetic Keto-Acidosis), diarrhea & starvation.

Urine Routine Examination:

• PROTEIN : Boiling test : satisfactory but

cumbersome.10-15 ml of urine is taken in a test tube & upper portion is boiled. If turbidity appears 3 drops of concentrated acetic acid are added & specimen is boiled again. A zero to +4 grading is used.

+1 Presence of slight turbidity,through which print can be read

30-100mg of protein/dl

+2 Turbidity with slight precipitates

100-300mg of protein/dl

+3 White cloudiness with fine precipitate

300-1000mg protein/dl

+4 Large clumps of white precipitates

>1mg of protein/dl

Cont.

Dipstick methods(e.g uristix) : widely used test for Proteinuria, more convenient &equally reliable.-Colour changes from yellow to green.-light chain proteins & LMW tubular proteins are not detected by this method.-Trace react. 5 to 20 mg/dl urinary prtn +1 30 mg/dl +2 100 mg/dl +3 300 mg/dl +4 > 1000 mg/dl

• Proteinuria in patients with Nephrotic Syndrome is massive (+3 or +4 by dipstick) & selective, constituted predominantly

of Albumin, without loss of proteins of higher molecular wt.• In the presence of tubular damage or physical injury to the

glomerular barrier, the proteinuria is non selective.• In renal parenchymal diseases,proteinuria is often quantified

to assess degree of glomerular injury.• Selective Proteinuria : intermediate sized(<1000kDa)

proteins(albumin,transferrin) leaks through glomerulus.• Nonselective proteinuria : range of different sized proteins

leak through,including larger proteins(immunoglobulin)

• Quantitative Measurement of Urine Protein -Accurate collection of urine over 24hr period is required to

quantitate protein excretion. -A value of >4mg/m22/hr is considered abnormal, & >40/m22/hr

indicates heavy proteinuria. -The range proteinuria in nephrotic syndrome is massive

proteinuria(>3.5gm/24hrs) while the range in nephritic syndrome is mild to moderate

proteinuria(<3gm/24hrs)

• Urine Protein/Creatinine Ratio : an approx. estimate of the severity of proteinuria also can be made by measurement of urine protein & urine creatinine on random urine sample.

-Values >2 indicate Heavy Proteinuria <0.2 are insignificant. -Such measurements are of use in following response to therapy in various disorders, but seldom necessary in children with nephrotic syndrome.

• GLUCOSE :the older methods(e.g benedict test) that detected reducing substance have mostly been replaced by Dipstick test,which is based on Glucose Oxidase Peroxidase linked reaction.• BLOOD :detection of Hb by dipstick is based on an reaction,

with a spotted +ve reaction indicating intact red blood cells & uniform +vity suggesting presence of free Hb. However the use of dipstick to detect hematuria is discouraged, b’coz reactions may often be false +ve(e.g myoglobinuria,oxidising substances, bacterial colonisation) or false –ve (e.g ascorbic acid, other reducing substances)

• A fresh,well mixed specimen should be examined.• Presence of cellular elements & casts should be noted.• Red cell casts : indicate glomerular inflammation.

Red cell casts & red cells in a pateint with glomerulonephritis

Microscopic Examination

White cell casts :clumping of neutrophils suggests acute pyelonephritis

Epithelial cell cast :are noted in patients recovering from Acute tubular necrosis

Hyaline or Fatty casts : may be +nt in proteinuric states or in normal in normal individuals with concenterated urine.

• Red blood cells & leukocytes can be counted under the high power field & more accurately in a counting chamber.

• >5 leukocytes/HPF(High Power Field) along with bacteruria suggests urinary tract infection.

• Neutrophils may also be detected in proliferative glomerulonephritis & interstitial nephritis, while the presence of Eosinophils in urine is specific of acute interstitial nephritis

• Hematuria is defined as presence of >5RBC/HPF in a centrifuged specimen.

• RBC morphology is useful in distinguishing Glomerular & non glomerular causes of hematuria.

• The site of injury is likely to be the lower urinary tract if <25% urine correlates well with a colony count of over 1055 organisms/ml indicating significant bacteriuria.

Renal Function Evaluation• Various aspects of renal function are -GFR(Glomerular Filtration Rate) -RPF(Renal Plasma Flow) -Reabsorption & Excretion of various substances like Na+, K+,

Ca+2, inorganic phosphate, glucose, urea, a.a, H2O & osmoles.• In clinical practice -determination of Creatinine Clearance is a measure of GFR -water deprivation & vasopressin administration tests to determine urinary concentrating ability, & -bicarbonate & ammonium chloride loading test to examine urinary acidification are usually sufficient for diagnostic evaluation & measurement of kidney function. • The results of these tests are important in assessing the

excretory function of the kidneys. For example, grading of chronic renal insufficiency and dosage of drugs that are excreted primarily via urine are based on GFR (or creatinine clearance).

• The concept of clearance is based upon the fact that the rate of removal of a substance from the plasma must equal its simultaneous rate of excretion in urine.

• Thus if the urinary excretion rate & plasma concentration of a substance are known, we can calculate the volume of plasma from which that substance would have been completely removed. INULIN has been taken as a reference substance.

• The standard formula for clearance is : C = U x V PC = clearence/min(ml/min)U = urinary concenteration(mg/dl)P = plasma concenteration(mg/dl)V = urine volume/min(ml/min)

Glomerular Function Test

• If a given substance is freely filtered & neither reabsorbed nor excreted, its clearance rate would accurately reflect GFR.

• The GFR can be estimated by measuring s.creatinine level & height. The formula proposed by SCHWARTZ is useful for children :

• GFR(ml/min/1.73m2) = K x Height(cm) S.Creatinine(mg/dl) K = 0.34 (in preterm infant) = 0.45 (in term infants) = 0.55 (in children & adolescent girls) & = 0.7 (in adolescent males)

Serum Creatinine & Creatinine Clearance :• Creatinine is derived from the metabolism of creatine &

phosphocreatine,the bulk of which is in muscle.• Since creatinine is chiefly excreted by glomerular

filteration,S.creatinine levels reflects changes in GFR.• S.creatinine values are low when the muscle mass is

decreased, as in malnutrition.• Bilirubin interferes with creatinine measurements.

• The normal values of S.creatinine are :

AGE RANGE(mg/dl)Cord 0.6-1.2

Newborn 0.3-1.0

<3 years 0.17-0.35

3-5 years 0.26-0.42

5-7 years 0.29-0.48

7-9 years 0.34-0.55

9-11 years 0.35-0.64

11-13 years 0.42-0.71

13-15 years 0.46-0.81

Adult Male 0.7-1.3

Adult Female 0.6-1.1

• CYSTATIN C : It is a LMW nonglycosylated protein produced at a constant rate by all nucleated cells in the body, freely filtered by the glomeruli, not secreted, but totally reabsorbed by the renal tubules.

• Little or no cystatin is excreted in urine.• Normal adults have circulating level of approx. 1mg/l.• This is better indicator of renal function as compared to

creatinine in early stages of GFR impairment as it is independent of age,gender,body composition & muscle mass.

• Cystatin C can be estimated in blood by enzyme immunoassays or immunoturbidometry. Both techniques are currently kit based & expensive.

• SINGLE INJECTION TECHNIQUE : In clinical practice, radionuclides are often used to estimate total GFR or to measure difference in clearance bet. one kidney compared to other in the same patient.

• The technique is based on use of a single injection, plasma disappearance curves to estimate the true GFR.

• Briefly, the radionuclide dye is injected & the signal from radiolabelled form is used to obtain measurment.

• The most commonly used Radionuclides for GFR are -DTPA (Diethyl triamine Penta-acetic acid) -EDTA (ethylene diamine tetra acetic acid) & -Iothalamate• Iohexol,a non ionic non radioactive LMW radiocontrast

agent,as an alternative to inulin,measured easily by HPLC(high performance liquid chromatography)

• BLOOD UREA : A normal level of blood urea is often mistakenly regarded to indicate normal kidney function.

• In a steady state the blood urea may not rise beyond the upper range of normal(40mg/dl) even when 75% of the renal function is lost.

• On the other hand, prerenal factors that decreases renal perfusion & GFR, such as dehydration, causes an increase in blood urea levels.

• There may be transient rise in blood urea level due to : -high protein intake & excessive protein catabolism( e.g with

severe infections, tissue break down, trauma, use of large doses of corticosteroids or tetracyclines)

-gastrointestinal bleeding & inhibition of anabolism.

• Renal blood flow measurements are performed using the clearance of PAH(para aminohippurate)

• >90% PAH is extracted from the plasma during the 1st pass through the kidneys.Therefore, renal clearance of PAH is commonly used as an estimate of renal plasma flow(RPF).

• Plasma clearance following single injection of 131I-hippuran or 99mTc-mercaptoacetyltriglycine(MAG-3)is an alternative method.

• Renal Blood Flow is calculated by dividing RPF by [1-hematocrit].

• Normal value ranges from 500 to 600 ml/min(abt. 1200ml/min/1.73m2).

• Other methods-Color Doppler US,Contrast Enhanced US & MRI.

Renal Blood Flow

• Expert evaluation of renal histology is important in the diagnosis of various renal parenchymal disease involving glomeruli, tubulo-interstitium & small blood vessels.

• The procedure has become has become much simpler with the use of automatic (biopsy gun, tru cut) devices & ultrasono -graphic visualization of kidney.

Renal Biopsy

• BIOPSY PROCEDURE-A renal biopsy is usually made percutaneously-A history of bleeding & clotting disorders should be obtained.-PT, BT, Coagulation time & Platelet count is measured.-BP should be in normal range-In Patients with acute renal failure,dialysis should be done to

reduce azotemia & correct biochemical abnormalities before the biopsy.

-Renal size & location are confirmed with an US before biopsy.-The Patient should be kept fasting for abt 3-4 hrs.-Local anaesthesia can be used

-The child lies in prone position with a folded towel or bed sheet placed under his lower ribs & epigastrium to push the kidneys posteriorly & stabilize their position.-The entry of biopsy needle into the kidney, when it pierces the renal capsule, is indicated by slight resistance & once in kidney it moves with respiratory excrusions -2 core of tissue(abt. 8-10 mm long) are needed for adequate histological examination.

-One core is fixed in buffered formaline & other in saline(for immunofluorescence study)

Interpretation of Renal Biopsy• The histology should be examined by light microscopy using

Hematoxylin & eosin(H & E),Periodic Schiff (PAS) & Silver Methanamine staining In all cases, & special stains as necessary.

• Electron microscopy is very useful in several disorders e.g Alport So, Membranoproliferative GN & thin Basement Membrane Disease.

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ReferencesBooks:•M.N. Chaterjee, Clinical Chemistry (Organ Function Tests and Laboratory Investigations), Jaypee Brothers Medical Publishers (1999)

•Ambika Shanmugam, Fundamentals of Biochemistry for Medical Students, Revised Edition(2005)

Links:

•Kidney Dialysis Foundation (2007). Normal Kidney Functions. Health Guide[Online]. Available: http://www.kdf.org.sg/health.php (2008, June 01).

•National Kidney Foundation (2007). Common Kidney Diseases. Education[Online]. Available: http://www.nkfs.org/index.php (2008, June 01).

Kidney disorders, Laboratory Investigation and Renal Function Tests

Education

Transcript of Kidney disorders, Laboratory Investigation and Renal Function Tests