Introduction To Nephrology
Dr. Mohammed Hannon Al Sodani C.A.B.M., F.I.B.M Consultant Nephrologist. Lecturer , College of Medicine, Baghdad University 5th year medial student March 7th,2016Imaging Techniques
Plain X-rays ; - renal outlines - opaque calculi - calcification within the renal tract. Ultrasound - This quick, non-invasive is the first and often the only. - renal size and position, - detect dilatation of the collecting system ( obstruction) - distinguish tumours and cysts. - the prostate and bladder, and estimate completeness of emptying - other abdominal, pelvic and retroperitoneal pathology. - In CKD ,U/S density (echogenicity) of the renal cortex is increased and cortico-medullary differentiation is lost.Normal kidney. The normal cortex is less echo-dense (blacker) than the adjacent liver.
A simple cyst occupies the upper pole of an otherwise normal kidney.The renal pelvis and calyces are dilated by a chronic obstructionto urinary outflow. The thinness and increased density of the remaining renal cortex indicate chronic changes
Doppler techniques - show blood flow in extrarenal & larger intrarenal vessels. -The resistivity index is the ratio of peak systolic and diastolic velocities, and is influenced by the resistance to flow through small intrarenal arteries. may be elevated in various diseases, - acute glomerulonephritis - rejection of a renal transplant. High peak velocities - severe renal artery stenosis. However, renal ultrasound is;- - operator-dependent, - stored images convey only a fraction of the information - it is often less clearin obese patients
Imaging Techniques
Imaging Techniques
Intravenous urography (IVU) ;- X-rays taken at intervals following administration of an IV bolus of an iodine-containing compound that is excreted by the kidney. An early image (1 minute after injection) demonstrates the nephrogram phase of renal perfusion followed by contrast filling the collecting system, ureters& bladder. An excellent definition of the collecting system and ureters, Superior to U/S for examining renal papillae, stones & urothelial malignancy The disadvantages of this technique are the injection of a contrast medium, exposure to irradiation , time requirement, dependence on adequate renal function,
Imaging Techniques
Pyelography direct injection of contrast medium into the collecting system from above or below. best views of the collecting system and upper tract, used to identify the cause of urinary tract obstruction). Antegrade pyelography requires the insertion of a fine needle into the pelvicalyceal system under ultrasound or radiographic control. difficult and hazardous in a non-obstructed kidney. In the presence of obstruction, percutaneous nephrostomy drainage can be established, and often stents can be passed through any obstruction. Retrograde pyelography can be performed by inserting catheters into the ureteric orifices at cystoscopy.Intravenous urography (IVU). A Normal nephrogram phase at 1 minute. B Normal collecting system at 5 minutes. C Bilateral reflux
Retrograde pyelography.. A catheter has been passed into the left renal pelvis at cystoscopy. The anemone-like calyces are sharp-edged and normal
Imaging Techniques
Renal arteriography and venography to investigate suspected renal artery stenosis or haemorrhage. Therapeutic balloon dilatation and stenting of the renal artery bleeding vessels or arteriovenous fistulae occluded. Computed tomography (CT) characterizing masses & cystic lesions within the kidney clear definition of retroperitoneal anatomy regardless of obesity. Even without contrast medium it is better than IVU for demonstrating renal stones. In CT urography, after a first scan without contrast, scans are repeated during nephrogram and excretory phases. This gives more information but entails a substantially larger radiation dose than IVUCT, the Rt kidney is expanded by a low-density tumour which fails to take up contrast material. Tumour is shown extending into the renal vein and inferior vena cava .
Imaging Techniques
. CT arteriograms are reconstructed using a rapid sequence technique in which images are obtained immediately following a large bolus injection of intravenouscontrast medium. This produces high-quality images of the main renal vessels and is of value in trauma, renal haemorrhage and the investigation of possible renal artery stenosis. - enables functional assessment of vascular structures, e.g. angiomyolipomas. However, relatively large doses of contrast are required. Imaging Techniques Magnetic resonance imaging (MRI) excellent resolution and distinction between different tissues A Normal kidneys. B Polycystic kidneys;.
Magnetic resonanceangiography (MRA) uses gadolinium-based contrast media, which may carry risks for patients with very low GFR . good images of main renal vessels but may miss branch artery stenosis
Renal artery stenosis. MRA following injection of contrast. The abdominal aorta is severely irregular and atheromatous. The left renal artery is stenosed
Radionuclide studies;-
- A functional studies requiring the injection of gamma ray-emitting radiopharmaceuticals which are taken up and excreted by the kidney, monitored by an external gamma camera. (99mTc-DTPA) Diethylenetriamine-pentaacetic acid labelled with technetium is excreted by glomerular filtration. provides information regarding the arterial perfusion of each kidne Delayed peak activity and reduced excretion is seen in RAS. In patients with significant obstruction of the outflow tract, DTPA persists in the renal pelvis, and a loop diuretic fails to accelerate its disappearance.Radionuclide studies;-
(99mTc-DMSA) technetium labelled Dimercaptosuccinic acid is filtered by glomeruli and partially bound to proximal tubular cells. Following intravenous injection, images of the renal cortex show the shape, size and relative function of each kidney. sensitive method for showing cortical scarring that is of particular value in children with vesico-ureteric reflux and pyelonephritis.Renal complications of radiological investigations
Contrast nephrotoxicity ;-An acute deterioration in renal function, commencing < 48 hrs after of i.v. radiographic contrast mediaRisk factors- Pre-existing renal impairment - Use of high-osmolality, ionic contrast media and repetitive dosing in short time periods Diabetes mellitus MyelomaDehydartion – Drugs ACEI ARBs NSAIDsContrast nephrotoxicity ;-
Prevention•• If the risks are high, consider alternative methods of imaging- Hydration, e.g. free oral fluids plus i.v. isotonic saline 500 mLthen 250 mL/hr during procedure- Avoid nephrotoxic drugs; withhold (NSAIDs). Omit metformin for 48 hrs after procedure in case renal impairment occurs- N-acetyl cysteine may provide weak additional protectionCholesterol atheroembolism
Days to weeks after intra-arterial investigations or interventions. caused by showers of cholesterol-containing microemboli, arising in atheromatous plaques in major arteries. in patients with widespread atheromatous disease, usually after interventions such as surgery or arteriography but sometimes after anticoagulation. loss of renal function, haematuria ,proteinuria, eosinophilia and inflammatory features ( mimic a small-vessel vasculitis.) Accompanying signs of microvascular occlusion in the lower limbs (e.g. ischaemic toes, livedo reticularis) are common There is no specific treatment but anticoagulation may be detrimental.The foot of a patient who suffered extensive atheroembolism following coronary artery stenting.
Renal complications of radiologicalinvestigations
Nephrogenic sclerosing fibrosis after MRI contrast agents - Chronic progressive sclerosis of skin, deeper tissues and other organs, associated with gadolinium-based contrast agents • Only reported in patients with renal impairment, typically on dialysis or with GFR < 1mL/min/1.73m2. caution is advised in patients with GFR < 30 mL/min/1.73m2Renal biopsy;-
Renal biopsy is used to establish the nature and extent of renal disease in order to judge need for treatment & the prognosis. Transcutaneous, with U/S or contrast radiography guidance to ensure accurate needle placement into a renal pole. -Specimens are divided into 3 samples and placed in - formalin for light microscopy, - normal saline for subsequent snap-freezing in liquid nitrogen for immunofluorescence, glutaraldehyde for electron microscopy -.Renal Biopsy ;- Indications
• ARF , not adequately explained (after exclusion of obstruction, reduced renal perfusion and ATN .• CKD with normal-sized kidneys or unexplained ,may be diagnostic, (e.g., identify IgA nephropathy )• Nephrotic syndrome or glomerular proteinuria in adults• Nephrotic syndrome in children with atypical features or is not responding to treatment• Isolated haematuria • Non Nephrotic range proteinuria >1g/24hr with renal characteristics or associated abnormalities • Familial Renal Disease Biopsy of one affected member • Renal Transplant Dysfunction .Renal biopsy;-Contraindications
Pateint related ;- - Disordered coagulation or thrombocytopenia. Aspirin and other antiplatelet agents increase bleeding risk- Uncontrolled hypertension - Uremia - Obesity - Uncooperative patient• Kidney related- Kidneys < 60% predicted size- Solitary kidney (except transplants) (relative contraindication)-Acute pyelonephritis/ perinephric abscess -Renal neoplasmMost contraindications are relative rather than absolute; when clinical circumstances necessitate urgent biopsy, they may be overridden, apart from uncontrolled bleeding diathesis.Renal Biopsy;- Complications;-
• Pain, usually mild• Bleeding into urine hematurea , usually minor / clot colic and obstruction• Bleeding around the kidney hematoma, occasionally massive and requiring angiography with intervention, or surgery• Arteriovenous fistula, rarely significant clinicallyHematurea
Haematuria ;- indicates bleeding from anywhere in the renal tract. macroscopic;- - visible and reported by the patient - tumors (most). - severe infections or -renal infarction usually accompanied by pain. microscopic ;- invisible and detected on dipstick testing of urineMicroscopy shows that normal individuals have occasional red blood cells (RBC) in the urine (up to 12 500 RBC/mL). The detection limit for dipstick testing is 15–20 000 RBC/mL,. However, dipstick tests are also positive in the presence of free haemoglobin or myoglobin.Interpretation of dipstick-positive haematuria
Urine microscopy Suggested cause --------------------------------------------------------------------------------------------------- - Menstruation, strenuous exercise, Haematuria - White blood cells - Infection - Abnormal epithelial cells - Tumour - Red cell casts with Dysmorphic RBC Glomerular bleeding ------------------------------------------------------------------------------------------------ Haemoglobinuria No red cells Intravascular haemolysis ----------------------------------------------------------------------------------------------- Myoglobinuria (brown urine) No red cells Rhabdomyolysis