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Radiologists’ role in nephrolithiasis

Radiologists’ role in nephrolithiasis. May 2012 Dr W.J. Conradie Department of Diagnostic Radiology. Nephrolithiasis Definition Incidence Classification Factors influencing treatment decision Imaging approach Adults Children Pregnancy R ole in management Antegrade pyelography

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Radiologists’ role in nephrolithiasis

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  1. Radiologists’ role in nephrolithiasis May 2012 Dr W.J. Conradie Department of Diagnostic Radiology

  2. Nephrolithiasis • Definition • Incidence • Classification • Factors influencing treatment decision • Imaging approach • Adults • Children • Pregnancy • Role in management • Antegrade pyelography • Percutaneous nephrostomy • Percutaneous nephrolithotomy Contents

  3. DEFINITION • Nephrolithiasis • Presence of renal calculi. • Nephrocalcinosis • Form of nephrolithiasis, characterised by diffusely scattered foci of calcification in the renal parenchyma. • Stedman’s Concise Medical and Allied health dictionary. Third edition • “Kidney Stones” or “calculi” • Composed of a combination of crystals (organic and inorganic) and proteins nehrolithiasis

  4. Incidence • 1.2 million Americans affected annually • Up to 14% of men and 6% of woman (M:V 3:1) • Any age: More than 1% < 18 years of age • Recurrence rate • 50 % in 5-10 years • 75% in 20 years • Annual health care burden (USA) • $1.83 billion in 1993 • $5.3 billion in 2000

  5. CLASSIFICATION OF STONES • Main role of Radiologist!! • Important: will impact patient treatment and outcome! • Stone size • <5mm; 5-10mm; 10-20mm; >20mm • Stone location • Upper-,middle- or lower calyx • Renal pelvis • Upper-, middle- or distal ureter • Bladder • X-ray characteristics • Aetiology • Stone composition • Risk groups for stone formation

  6. X-ray characteristics

  7. Aetiology of stone formation

  8. Composition

  9. Risk groups for stone formation

  10. SIZE AND POSITION PERCUTANEOUS NEPHROLITHOTOMY Factors influencing treatment decisions ±LASER

  11. HU:<450 - Uric acid 600-900 - Struvite 600-1100 - Cystine 1200-1600 - Hydroxyapetite(Calcium phosphate) 1700-2800 - Clacium oxalate and Brushite(Calcium hydrogenphosphate) COMPOSITION, AETIOLOGY

  12. ADULTS Ultrasound • Primary investigation? • Varma G et al: • Renal stones > 5mm - sensitivity 96%; specificity nearly 100% • All stone locations - reduces to 78% and 31%. • Sandu et al: • “US has limited diagnostic value in the assessment of patients with suspected renal stones…. particularly in the evaluation of distal ureteral calculi “ Kidney-Ureter-Bladder radiograph (KUB) • Sensitivity 44% to 77% and specificity 80% to 87%, • KUB not be done if NCCT considered. • Value: • ?Radiopaque/radiolucent • Follow up Imaging approach

  13. Intravenous urography (IVU) • Largely replaced by CT, MRI and US • Contraindications: • General precautions to radiation and contrast agents (LOCM 370) • Dosages • Adult: 50-100ml • Paediatric: 1ml per kg • Technique • KUB (Rapid injection of bolus) • 15sec-1min film = Nephrogram phase • 5 min film = Excretion phase (apply band) • 10 min film = Pelvi-ureteral phase (release band) • Release film = Ureteral phase (empty bladder) • Coned bladder view/ Post-void KUB

  14. Diagnosis of calculi on IVP • Nephrogram: Delayed or persistent due to ureteral obstruction • Column of opacified urine proximal to stone • Minimal dilated • Degree not related to stone size • Narrow ureter distal to calculus • Oedema, inflammation • False impression of stricture • “Steinstrasse” • German for “stone street” or “street of stones” • Several calculi are bunched up along ureter (common after lithotripsy) • “Halo appearance” - oedema around distal ureter (>2mm) • (<2mm = Pseudoureterocele)

  15. IVU

  16. Non Contrast-enhanced CT (NCCT) • Modality of choice • sensitivity (95%–98%) and specificity (96%–100%) • Superior to IVU in diagnosis of stones. • Multidetector and Dual energy CT • Multiplanar and 3D imaging – better accuracy • All stones (except Indinavir and pure matrix stones) • Density, size, position, tissue differentiation • Stone-to-skin distance (ESWL) • Identify other causes for pain. • Dalrymple et al - 55% of patients undergoing CT for acute flank pain did not have stones; 15% other abnormalities that was detected.

  17. Drawback (NCCT) • Renal function? • Anatomy of collecting system? • Radiation • Reduce radiation by low-dose CT • 100mAs; 120kv • BMI <30 or weight <90 kg • Dose similar to KUB study • -Kluner et al • -Heneghan et al • Renal contrast study (CT or IVU) recommended when surgery is planned. • CT preferred • Enables 3D reconstruction • Density/size • Stone-to-skin distance

  18. Multidetector CT • Technique • No patient preparation • Entire urinary tract • Diagnosis: NCCT • Workup: Contrast study • Thinner (1–3mm) reconstructions recommended - reduction in partial volume averaging effect. • 5-mm scans/3-mm coronal reformatted images - been found to improve stone detection while allowing radiation dose benefits • Signs of Nephrolithiasis • Stone within urethral lumen • Dilated proximal- and normal calibre distal lumen • Dilatation may be absent! • Dalrymple et al: Urethral stones more likely in proximal (37%) and distal urethra (33%) in acute situation. • Secondary signs: • Hydroureter • Hydronephrosis • Peri-nephric fat stranding • Peri-urethral oedema • Unilateral renal enlargement • Contrast filling defect (Indinavir stones!)

  19. Stone within urethral lumen Dilated proximal urethra Secondary signs: Hydronephrosis Fat stranding Renal enlargement

  20. Calculus or phlebolith? CALCULUS ANY SHAPE, HOMOGENOUS, ALONG URETER “SOFT-TISSUE RIM SIGN” PHLEBOLITH ROUND, CENTRAL LUCENCY, IN TRUE PELVIS “COMET TAIL SIGN”

  21. Stone or stent?

  22. Fragility? Homogeneous vs heterogeneous

  23. Composition? Dual-energy CT scanner

  24. Stone-to-skin distance

  25. Magnetic Resonance urography (MRU) • Relative insensitive for detection of calcification • Relies on secondary signs of obstruction • Ureteral dilatation • Perinephric fluid • Persistant “filling defect” • Technique dependant • Excretory MR urography • IV gadolinium • Sensitivities up to 90% reported • Static-fluid T2-weighted images • T2 weighted technique • Sequences • HASTE • RARE

  26. mru

  27. Children • Ultrasound • First line imaging modality • Practical technique • No radiation or sedation • Information: • Presence and size of stones • Location • Degree of dilatation and obstruction • Cause • Nevertheless: • Fail to identify stones in 40 % of patients • No information on kidney function

  28. children • Plain films(KUB) • Identify stones • Radio-opacity • Facilitate follow up • Intravenous urography (IVU) • Can be important tool • Drawback: IV contrast • Magnetic resonance urography (MRU) • “Filling defect” in T2 images • Information: • Anatomy of collecting system • Level of obstruction • Morphology of renal parenchyma

  29. children • Helical CT • Radiation risk • Low-dose CT • Reduced slices • 5% of stones escape detection by non-enhanced helical CT • Sedation or anaesthesia - rarely needed with modern high-speed CT apparatus. • Nuclear medicine • 99mTc-dimercaptosuccinyl acid scanning • information about cortical abnormalities (such as scarring) • not for primary diagnosis of nephrolithiasis • Diuretic renogram • Radiotracer (MAG3 or DPTA) and furosemide - used to demonstrate: • renal function • identify obstruction • indicate the anatomical level of the obstruction

  30. pregnancy • Remains diagnostic and therapeutic challenge • Approach • Ultrasound • Abdominal • Transvaginal • Endoluminal • Limited Excretory Urogram (IVU) for symptomatic patients • Preliminary KUB; • 15min; • 60min after contrast • MRU!! • Static T2 images

  31. Antegrade pyelography • Needle through renal parenchyma into minor calyx (posterior lower pole preferred) • Inject contrast to demonstrate obstruction. • Percutaneous nephrostomy • Introduction of drainage catheter into collecting system of kidney. • obstruction due to stone • prior to percutaneous nephrolithotomy. • Percutaneous nephrolithotomy • Removal of larger renal calculi through a nephrostomy line. • After series of dilatations; nephroscope inserted • Direct removal of stones <1cm • Stone disintegration with US or electrohydraulic disintegrator. Role in management

  32. http://www.uroweb.org/guidelines/online-guidelines/Guidelines on Urolithiasis. European Association of Urology 2011. C. Türk(chairman), T. Knoll (vice-chairman), A. Petrik, K. Sarica, M. Straub, C. Seitz • Kambadakone A, Eisner B, Catalano O, Sahani D. New and evolving concepts in the imaging and management of urolithiasis: Urologists’ Persapective.Radiographics 2010. 30: 603-623 • VarmaG, Nair N, Salim A, Marickar YM. Investigations for recognizing urinary stone.Urol Res. 2009 Dec;37(6):349-52. • Sandhu C, Anson KM, Patel U. Urinary tract stones I. Role of radiological imaging in diagnosis and treatment planning. ClinRadiol 2003;58(6): 415–421. • DalrympleNC, Verga M, Anderson KR, et al. The value of unenhanced helical computerized tomography in the management of acute flank pain. J Urol 1998;159(3):735–740. • Kluner C, Hein PA, Gralla O, Hein E, Hamm B, Romano V, Rogalla P. Does ultra-low-dose CT with a radiation dose equivalent to that of KUB suffice to detect renal and ureteral calculi? J Comput Assist tomog.2006 Jan-Feb; 30(1):44-50 • Heneghan P, McGuire KA, Leder RA, DeLong DM, Yoshizumi T, Nelson RC. Helical CT for Nephrolithiasis and Ureterolithiasis: Comparison of Conventional and Reduced Radiation-Dose Techniques. Radiology. 2003: 229:575–580 • Silverman SD, Leyendecker JR, Amis ES. What is the current role of CT urography and MR urography in the evaluation of the renal tract? Radiology 2009; 250: 309-323 • Garcia-Valtuille R, Garcia-Valtuille L, Abascal F, Cerezal L, Arguello MC. Magnetic resonance urography: a pictorial overview. BJR 79 (2006), 614-626. • A guide to radiological procedures. Fifth edition. Frances Aitchison. Saunders puplishers. • Stedman’s concise medical and allied health dictionary. Third edition. Williams and Wilkins publisher. References

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