INVESTIGATION OF RENAL&UT DISEASES
الدكتور خلدون ذنون- كلية طب نينوى- المرحلة الرابعةObjectives
Pay attention to the following:
1. The tests which are needed to diagnose each renal diseases.
2. The benefits and limitations of each test.
3. The diagnostic test for each disease.
4. Renal biopsy indications, contraindications, and complications.
Urine analysis
● dipsticks: screen for blood and protein, nitrite and leukocyte esterase in UTI , glucose in DM.● Urine microscopy: RBC shape and RBC cast, pus cells, bacteria.
● Flow cytometry: screen for WBC and bacteria.
● Crystals: calcium oxalate, urate, cysteine.
● Urine PH: renal tubular acidosis, stone formation.
● Specific gravity: in diabetes insipidus.
● 24 hour urine collection: excretion rate of Na, urate, Ca, and oxalate in stone formation.
● Dynamic tests: urine concentration, ability to excrete water load, ability to excrete acid.
● Tubular excretory function: comparison of blood and urine ratio of electrolytes to creatinine. E.g urine Na/plasma Naplasma creatinine/urine creatinine. Decreased in volume depletion and increased in tubular damage in renal tubular acidosis.
Urine culture: to detect usual bacteria and TB bacilli.
Blood urea poor guide to renal function. NR 3.5- 6.5mmol/L. It is ( in :
Renal failure.
GIT haemorrhage.
High protein diet.
Trauma, burns.
Serious infection.
Hypovolaemia :(tubular absorption of urea.
It is ( in :
Anorexia & malnutrition.
Liver failure.
High urine flow:(tubular absorption.
Serum creatinine More reliable, produced from muscle at aconstant rate, almost completely filtered at the glomerulus, as very little cr. is secreted by tubular cells, the cr.clearance is nearly equal to GFR. NR: 85(mol/L- 120(mol/L, it is (in:
Renal failure.
Rhabdomyolysis
Large muscle mass.
Drugs e.g trimethoprim, cimetidine (competition for tubular secretion).
(cr. Occurs in small muscle mass.
(excretion does not occur, dietary cr.does not affect serum level much. ( serum cr.does not occur until GFR is ( by about 50% .
Glomerular filtration rate GFR
Measures renal function (120(25ml/min./1.73m2). Men 12% higher than women.
Inulin clearance measurement is difficult&is replaced by 51cr-labelled EDTA which measures GFR more accurately, it is simple,no injection is required.
Creatinine clearance mls/min ( amount of cr.((mols)in 24hr urine (1000
plasma cr.((mol/L) ( 1440
Cockcroft&Gault equation:estimate GFR from s.cr alone
CR.CL ( (140-age)(lean body wt.(kg)(1.22male,1.04female
s.cr((mol/L)
Plain radiograph: show renal outline,opaque calculi &calcification.,
Ultrasound
Quick, non-invasive, assess renal size & position, dilation of the collecting system, tumors & cysts, show other abdominal structures, image prostate & bladder.Images are less clear in obese, disadvantage: operator dependent.
CRF:(density of renal cortex & corticomedullary differentiation is lost.
Doppler study: shows blood flow in renal & extrarenal blood vessels, resistivity index(peak systolic/peak diastolic velocities (in acute GN & renal transplant rejection. Severe renal artery stenosis causes damping of flow in intrarenal vessels with high peak velocities, U/S has not been proved to be reliable for detecting renal artery stenosis.
Intravenous urography IVU
Largely replaced by U/S, provides excellent definition of the collecting system & ureters, superior to U/S for examining renal papillae, stones & urothelial malignancy.
i.v iodine-containing compound that is excreted by the kidneys, the nephrogram phase occur 1min.after injection followed by contrast filling pelvicalaceal system & bladder.
Disadvantages: injection, time factor, needs adequate renal function,risk of contrast.
Contrast nephrotoxicity: occur within 24hrs of i.v contrast. Risk factors: preexisting renal impairment, use of high-osmolality contrast media, diabetes mellitus & metformin, myeloma.
Prevention: hydration by free oral fluids, i.v isotonic saline 500ml
then 250ml/hr during the procedure.
Avoid nephrotoxic drugs e.g NSAIDS, metformin,etc
Diuretics(the risk.If risks are high, consider alternative methods of
imaging.
Pyelography Direct injection of contrast medium in to the collecting system from above or below, best used for UT obstruction .
1.Antegrade pyelography: fine needle is introduced in to the pelvicalyceal system under U/S or radiographic control, contrast outlines the collecting system & localise site of obstruction. Difficult & hazardous in non-obstructed kidney. Percutaneous nephrostomy drainage & stenting can be done at the same time.
2.Retrograde pyelograhy: done by inserting catheters in to the ureteric orifices at cystoscopy.
Renal arteriography&venography Indications: 1.Renal artery stenosis. 2.Haemorrhage. 3.Renal tumors in the absence of CT. Therapeutic balloon dilitation & stenting or occlusion of bleeding vessels& AV fistulae may be done. Complication: cholesterol atheroembolism which occurs days or weeks after intra-arterial investigation.
Computed tomography CT 1. Kidney tumors or cysts. 2. Definition of retroperitoneal structures which is aided by (amount of fat. Spiral CT (rapid sequence technique) ( Images are obtained immediately after alarge bolus injection of i.v
contrast to outline vascular structures, produces high-quality images of
the main renal vessels.
( Spiral CT screens renal artery stenosis in secondary hypertension,
advantage of providing renal & adrenal images at the same time.
( Very useful for demonstrating renal stones.
MRI ( Excellent resolution & distinction between different tissues. ( MR angiography(MRA) uses gadolinium-based contrast media, non
nephrotoxic&avoides atheroemboli, good images of main renal vessels. ( Non-invasive screening for renal artery stenosis(RAS).
Radionuclide studies
Injection of gamma ray-emitting radioisotope, taken up & excreted by the kidney, monitered by gamma camera, thus kidney function is assessed.99mTC-DTPA injection, computer analysis of uptake & excretion regarding arterial perfusion of each kidney, in RAS transit time is prolonged & excretion is (.
Captopril renography, in less severe RAS.
Outflow tract obstruction(persistence of nuclide in renal pelvis & loop diuretic fails to accelerates its disappearance.
99mTC-DMSA filtered by glomeruli after i.v injection( image renal cortex & show shape, size & function of each kidney. Sensitive method of detecting early cortical scarring in children with vesico-ureteric reflux & pyelonephritis & assess each kidney function.
Renal biopsy indications: 1. ARF unexplained. 2. CRF with normal sized kidney. 3. Nephrotic synd.or glomerular proteinuria in adults. 4. Nephrotic synd. in children with atypical features or not responding to
treatment. 5. Isolated renal heamaturia.
Contraindications: 1. Bleeding tendency. 2. Uncontrolled hypertension. 3. Kidney (60% of predicted size. 4. Solitary kidney (relative) except in transplanted kidney. Complications:
Mild pain
heamaturia
clot colic&obstruction
Bleeding around the kidney sometime massive & require intervention.
AV fistula
Endoscopy: urethroscope and cystoscope. Done in cases of hematuria, for diagnosis and therapy.
PAGE
PAGE 4