URINARY SYSTEM imaging in Radiology.pptx

Imaging of Urinary Systems

1. URINARY SYSTEM IMAGING TECHNIQUES & PROCEDURES

2. IMAGING MODALITIES Plain film radiography Excretion urography (intravenous urogram (IVU)) Ultrasound (US) Computed tomography (CT) Magnetic resonance imaging (MRI) Renal arteriography Renal scintigraphy Interventional radiology

3. PLAIN FILM RADIOGRAPHY Predominantly to evaluate renal tract calcifications CT is significantly more sensitive (>98% compared with 60% for plain films) Perirenal fat often makes part of or all of the renal outline visible Gas in colon/stomach/duodenum may overlie renal outline

4. Ureter is not visible, but a knowledge of its course is essential when looking for radio-opaque calculi Passes anterior to the tips of transverse processes of L2 to L5 vertebrae, anterior to SIJ, curves laterally at the ischial spines medially again to the urinary bladder.

5. Technical evaluation Ensure visualization of the upper poles of both kidneys even if the diaphragm was not imaged Alignment – vertebral column should be in midline. Ribs, pelvis, and hips should be equidistant. No rotation – spinous processes in the centre of vertebral column and symmetrical iliac wings. No motion – ribs, diaphragm, and gas bubble margins should appear sharp Soft tissue visualization – lower liver margin, kidneys, lateral borders of psoas, and transverse processes of lumbar vertebrae Appropriate markers indication upright or supine position

6. ULTRASOUND Renal mass lesion Renal parenchymal disease Renal obstruction/loin pain Hamaturia Hypertension Renal cystic disease Renal size measurement Bladder outflow obstruction Urinary tract infection Bladder tumour Following renal transplant Obstruction Patency of vessels Perirenal collections To guide needle placement in interventional procedures Renal vascular studies INDICATIONS:

7. CONTRAINDICATIONS: NONE PREPARATIONS Kidneys only – none Kidneys and bladder – prehydrate with oral fluid, patient attends with full bladder Disadvantage: the collecting systems appear mildly hydronephrotic premicturition

8. EQUIPMENT 3.5 to 5 MHz transducer

9. Length measured by US is 1-2cm smaller than that measured at excretion urography, because there is no geometric magnification Range of lengths of normal kidney is 9-12cm (difference each kidney should be less than 1-2cm.

10. Computed tomography INDICATIONS: Renal colic/renal stone disease Renal tumour Renal/perirenal collection Loin mass Staging and follow up of urinary tract malignancy Investigation of renal tract obstruction CTA to assess renal vessels for suspected renal artery stenosis or arterio-venous fistula/malformation, active bleeding

11. TECHNIQUES: STANDARD DIAGNOSTIC CT Venous access is obtained Patient lies supine Scanogram is taken of chest, abdomen, and pelvis as appropriate 100ml IV LOCM given Scans obtained approximately 70s (portal venous phase) after IV contrast

12. Techniques: renal lesion characterization Used to assess renal cysts or masses identified on another imaging modality such as ultrasound Pre and post IV contrast scans are obtained through the kidneys in order to assess precontrast attenuation and subsequent enhancement patterns

13. Plain CT is useful to assess possible stone disease Used in most centres as the primary investigation of renal colic (replacing plain KUB radiograph) No IV or oral contrast is given Patient supine Scan from top of the kidneys to the bladder base

14. CTU- PLAIN Provides a baseline from which to measure the enhancement within the lesion after the administration of IV contrast Important in distinguishing hyperdense cysts from solid tumours, because most tumours will enhance while cysts do not Another reason is that urolithiasis or calcifications are best seen on unenhanced CT

15. CORTICOMEDULLARY PHASE Contrast within cortical capillaries and peritubular spaces Also present in proximal convoluted tubules and columns of Bertin May last longer in patients with renal dysfunction or diminished cardiac output Renal cortex enhances briskly from its unenhanced attenuation (30-40HU) to 70HU at 25-35s, and 145-185HU at 40-50s Medulla enhances minimally Differences in enhancement between cortex and medulla are pronounced (~100HU difference)

16. EXCRETORY PHASE Contrast filters through glomeruli, enters loop of Henle and collecting ducts Onset is delayed in patients with abnormal renal function or compromised cardiac output Renal medullary and cortical enhancements are similar (range between 120-170HU) Best opportunity for discrimination between the normal renal medulla and mass/lesion.

17. CT RENAL 4 PHASE Positioning – supine, arm positioned comfortably above head Topogram – craniocaudal, in inspiration IV contrast 80ml at 4ml/sec Ultravist 300 (LOCM – iopromide) Dose kV:120 Effective mAs: autocalculated by machine depending on patient’s body habitus

18. Plain phase Area scanned: kidneys or kidneys to bladder if haematuria Corticomedullary phase Area scanned: kidney Bolus tracking: 80HU at abdominal aorta at costophrenic angle level Nephrogenic phase Area scanned: abdomen and pelvis Approximately 60 seconds after IV contrast or 15 seconds after cortiomedullary scan Excretory phase Area scanned: kidneys or kidneys to bladder 10 min delay

19. C T angiography renal Indications: Renal artery stenosis Renal artery aneurysm, AVM, dissection, or thrombosis Delineation of vascular anatomy prior to surgery, e.g. nephrectomy, pyeloplasty

20. No oral iodinated contrast used Scan from upper pole of kidneys to the aortic bifurcation Narrow collimation (1mm) 100-150ml of IV contrast injected at 3-4ml/sec Use of bolus tracking/triggering devices or timing test injections is recommended to ensure appropriate timing

21. MRU Indication: To demonstrate the collecting system/determine level of obstruction in a poorly functioning/obstructed kidney Urinary tract obstruction unrelated to urolithiasis Congenital anomalies Renal transplant donor assessment (combined with MR angiography)

22. Static MR urography Independent of renal excretion. Uses urine as contrast 2D cine allows visualization of moving urine 3D sequences best with dilated/obstructed system

23. Excretory MR urography Gadolinium-based contrast agent is administered IV using a dose of 0.1 mmol gadolinium kg-1 body weight Dependent on renal excretion Good for non dilated system Provides function and morphology Able to demonstrate complicated anatomical variants

24. MR renal angiography Gadolinium enhanced Indications: Renal artery anomalies – aneurysm, AVM, stenosis Pre surgery Potential renal transplant donor

25. Renal scintigraphy Static renal radionuclide scintigraphy Also known as renal cortical scan DMSA scan Dynamic renal radionuclide scintigraphy Also known as renal perfusion scan MAG3, DTPA scan

26. STATIC RENAL RADIONUCLIDE SCINTIGRAPHY Indications Assessment of individual and relative renal function Investigation of urinary tract infections, particularly in children for scarring Assessment of reflux nephropathy for scarring Identification of horseshoe, solitary, or ectopic kidney Differentiation of a pseudotumour due to hypertrophied column of Bertin from a true tumour Contraindication Pregnancy

27. Radiopharmaceuticals 99m TC-dimercaptosuccinic acid (DMSA), 80 MBq max (0.7 mSv ED) Bound to plasma proteins Cleared by tubular absorption DMSA is retained in the renal cortex, with an uptake of 40%-65% of the injected dose within 2H and no significant excretion during the imaging period Gives the best morphological images of any renal radiopharmaceutical, and is used for assessment of scarring Gives the most accurate assessment of differential renal function

28. Equipment Gamma-camera with a low-energy, high resolution collimator Technique Radiopharmaceutical is administered IV Images acquired at anytime 1-6H later (imaging in the first hour is to be avoided because of free 99mTC in the urine)

29. Images Posterior, right (RPO) and left posterior oblique (LPO) views Anterior images in cases of suspected pelvic or horseshoe kidney and severe scoliosis, or if relative function is to be calculated by geometric mean method Zoom or pinhole views may be useful in children

30. DYNAMIC RENAL RADIONUCLIDE SCINTIGRAPHY Indications Evaluation of obstruction Assessment of renal function following drainage procedures to the urinary tract Assessment of perfusion in acute native or transplant kidney failure Demonstration of vesicoureteric reflux Renal trauma Diagnosis of renal artery stenosis Contraindication None

31. Radiopharmaceuticals 99mTc-MAG-3 (mercaptoacetyltriglycine) 100MBq max (0.7mSv ED) Highly protein bound 80% cleared by tubular secretion 20% by glomerular filtration Radiopharmaceutical of choice – better image quality, particularly in patients with impaired renal function 99mTc-diethylene triamine-pentaceticacid (DTPA) 150MBq typical (1mSv ED) Cleared by glomerular filtration Poorer image quality due to lower kidney/background ration

32. Equipment Gamma-camera with a low-energy general purpose collimator Preparation Patient should be well hydrated with around 500ml of fluid immediately before administration of tracer Bladder should be voided before injection

33. Technique Supine or sits reclining with their back against the camera Radiopharmaceutical is injected IV and image acquisition is started simultaneously Perform dynamic acquisition with 10-15s frames for 30-40min If poor drainage from one or both kidneys after 10-20min: Give IV frusemide 40mg Continue imaging for further 15min If significant retention in the kidneys is apparent at the end of the imaging period: Ask patient to void and Walk around for a minute before further short acquisition is taken

34. Right pelvic kidney, an anatomical variant and the most common form of renal ectopia.

35. RENAL ARTERIOGRAPHY INDICATIONS Renal artery stenosis prior to angioplasty or stent placement Diagnostic arteriography has been replaced generally by MRA or CTA Assessment of living related renal transplant donors Replaced generally by MRA or CTA Embolization of vascular renal tumour prior to surgery Haematuria particularly following trauma, including biopsy Prior to prophylactic embolization of an angiomyolipoma (AML) or therapeutic embolization of a bleeding AML

36. Renal arteriography: contrast medium Flush aortic injection LOCM 300/320 mgI/mL, 45mL at 15mL/s Selective renal artery injection LOCM 300 mgI/mL, 10mL at 5mL/s, or by hand injection

37. EQUIPMENT: Digital fluoroscopy unit Pump injector Catheters: Flush aortic injection – pigtail 4F Selection injection – Sidewinder or Cobra catheter

38. Start with flush aortogram, To assess normal anatomy/variants Selective renal arteriogram may miss lesions at origin of renal artery Place tip of pigtail catheter proximal to renal vessels (T12 level) Contrast: 40-50ml, 20-25mls/sec Perform angiographic (digital subtraction) runs: AP & oblique

39. SELECTIVE RENAL ARTERIOGRAM Better assessment of renal vasculature Place tip of catheter at the selected renal artery (L1/L2 level) Contrast: 10ml, 5ml/sec Perform angiographic runs (digital subtraction)

40. INTERVENTIONAL RADIOLOGY Can be done under fluoroscopy, ultrasound, CT, and angiography Percutaneous renal biopsy Percutaneous nephrostomy

41. ANATOMY: Posterior relationship of the diaphragm Kidney moves with respiration Posterior relationship of pleura – lower pole safer than upper pole Puncture at midlateral border – Brodel bloodless line of incision Represents the plane where the anterior and posterior segmental renal artery branches meet The avascular plane of the kidney is approximately between 2/3 anterior and 1/3 posterior kidney

42. PERCUTANEOUS RENAL BIOPSY Indication Diagnostic biopsy: unexplained renal failure, mass Contraindication Bleeding diathesis Equipment USG or CT guidance Bard gun with core biopsy needle Patient preparation Fasting for 4 hours Blood parameters Premedication/sedation as required

44. Complications Bleeding Arteriovenous fistula Pseudoaneurysm

45. Percutaneous nephrostomy Indications Renal tract obstruction Pyonephrosis Prior to percutaneous nephrolithotomy Ureteric or bladder fistula: external drainage, i.e. urine diversion may allow closure Contraindication Uncontrolled bleeding diasthesis

46. Contrast medium LOCM Equipment Puncture needle/coaxial needle Drainage catheter J-guidewire USG and/or fluoroscopy Patient preparation Fasting for 4 hours Blood parameters Premedication/sedation as required May need prophylactic antibiotics

47. Technique Prone oblique Identify collecting system with USG guidance Plane of puncture – posterior axillary line below 12th rib LA infiltrated with spinal needle, under US guidance Insert puncture needle, advance towards mid/lower pole of kidney and into pelvicalyceal system Aspirate urine to confirm position Insert guidewire through needle, into pelvicalyceal system Remove puncture needle, dilate the tract with dilators Insert pigtail catheter, till its tip within pelvicalyceal system, remove guidewire Inject contrast media while screening Secure catheter to the skin with suture

48. Complications Septicemia Hemorrhage Perforation of collecting system with urine leak Unsuccessful drainage Injury to adjacent organs Catheter dislodgement