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RADIOLOGISTS’ ROLE IN NEPHROLITHIASIS May 2012 Dr W.J. Conradie Department of Diagnostic Radiology • Nephrolithiasis • • • Factors influencing treatment decision • Imaging • • • Adults Children Pregnancy • Role • • • approach in management Antegrade pyelography Percutaneous nephrostomy Percutaneous nephrolithotomy CONTENTS • Definition Incidence Classification 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 DEFINITION 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 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 X-RAY CHARACTERISTICS AETIOLOGY OF STONE FORMATION COMPOSITION RISK GROUPS FOR STONE FORMATION PERCUTANEOUS NEPHROLITHOTOMY ±LASER FACTORS INFLUENCING TREATMENT DECISIONS SIZE AND POSITIO N COMPOSITION, AETIOLOGY HU: <450 - Uric acid 600-900 - Struvite 600-1100 - Cystine 1200-1600 - Hydroxyapetite (Calcium phosphate) 1700-2800 - Clacium oxalate and Brushite (Calcium hydrogenphosphate) 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 ADULTS 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 1. 2. 3. 4. 5. 6. KUB 15sec-1min film = Nephrogram phase 5 min film = Excretion phase 10 min film = Pelvi-ureteral phase Release film = Ureteral phase Coned bladder view/ Post-void KUB (Rapid injection of bolus) (apply band) (release band) (empty bladder) Diagnosis of calculi on IVP Nephrogram: Delayed or persistent due to ureteral obstruction Column of opacified urine proximal to stone Narrow ureter distal to calculus Oedema, inflammation False impression of stricture “Steinstrasse” Minimal dilated Degree not related to stone size German for “stone street” or “street of stones” Several calculi are bunched up along ureter (common after lithotripsy) “Halo appearance” (>2mm) (<2mm = Pseudoureterocele) - oedema around distal ureter IVU 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. 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 MULTIDETECTOR CT Signs of Nephrolithiasis Stone within urethral lumen Dilated proximal- and normal calibre distal lumen Technique No patient preparation Entire urinary tract Dilatation may be absent! Dalrymple et al: Urethral stones more likely in proximal (37%) and distal urethra (33%) in Diagnosis: NCCT Workup: Contrast study acute situation. Secondary signs: Thinner (1–3mm) reconstructions recommended - reduction in partial volume averaging effect. Hydroureter Hydronephrosis Peri-nephric fat stranding Peri-urethral oedema Unilateral renal enlargement Contrast filling defect (Indinavir stones!) 5-mm scans/3-mm coronal reformatted images - been found to improve stone detection while allowing radiation dose benefits Stone within urethral lumen Dilated proximal urethra Secondary signs: Hydronephrosis Fat stranding Renal enlargement CALCULUS OR PHLEBOLITH? CALCULUS PHLEBOLITH ANY SHAPE, HOMOGENOUS, ALONG URETER “SOFT-TISSUE RIM SIGN” ROUND, CENTRAL LUCENCY, IN TRUE PELVIS “COMET TAIL SIGN” STONE OR STENT? FRAGILITY? HOMOGENEOUS VS HETEROGENEOUS COMPOSITION? DUAL-ENERGY CT SCANNER STONE-TO-SKIN DISTANCE 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 MRU 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 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 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 PREGNANCY Remains diagnostic and therapeutic challenge Approach Ultrasound Limited Excretory Urogram (IVU) for symptomatic patients Abdominal Transvaginal Endoluminal Preliminary KUB; 15min; 60min after contrast MRU!! Static T2 images 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 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 2. 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 3. Varma G, Nair N, Salim A, Marickar YM. Investigations for recognizing urinary stone. Urol Res. 2009 Dec;37(6):349-52. 4. Sandhu C, Anson KM, Patel U. Urinary tract stones I. Role of radiological imaging in diagnosis and treatment planning. Clin Radiol 2003;58(6): 415–421. 5. Dalrymple NC, 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. 6. Kluner C, Hein PA, Gralla O, Hein E, Hamm B, Romano V, Rogalla P. Does ultralow-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 7. 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 8. 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 9. Garcia-Valtuille R, Garcia-Valtuille L, Abascal F, Cerezal L, Arguello MC. Magnetic resonance urography: a pictorial overview. BJR 79 (2006), 614-626. 10. A guide to radiological procedures. Fifth edition. Frances Aitchison. Saunders puplishers. 11. Stedman’s concise medical and allied health dictionary. Third edition. Williams and Wilkins publisher. REFERENCES 1.