Urografi

[Nayra Waddles]

Hvis man fr konstateret mikroskopisk hmaturi, er der en meget lille risiko for, at man har krft og i s fald er det i blren. Hos den slags patienter er det ikke ndvendigt at lave en CT-urografi. I stedet vil man f foretaget en kikkertundersgelse af blren (cystoskopi).

Man lgger sig p lejet og bliver skannet fra mellemgulvet til knsbenet. Derefter fr man kontraststof i en blodre i armen. Hvis ens nyrefunktion er normal, vil der efter 10 minutter vre udskilt s meget kontraststof, at man kan blive scannet igen anden gang og f et samlet billede af urinlederere og blren. Det kan i nogle tilflde vre ndvendigt at blive scannet en tredje gang.

Risikoen for skadevirkninger efter rntgenundersgelser er meget lille, mens der er mange fordele ved at f undersgelsen, fordi undersgelsen danner grundlag for, at man kan f den bedst mulige behandling.

Det er vigtigt, at man fortller den henvisende lge og personalet p radiologisk afdeling, hvis man tidligere er blevet behandlet med medicin for en bivirkning efter at have fet kontraststof. Det er ogs vigtigt, at man fortller, hvis man har ubehandlet allergi eller astma.

Dansk Radiologisk Selskab har valgt at prsentere magnetisk resonans-urografi, der de seneste r er udviklet til et vrdifuldt alternativ til den intravense urografi. Behovet for alternativer til potentielt skadelige rntgenundersgelser blev understreget med den nye rntgenbekendtgrelse, som trdte i kraft den 1. maj 2000, idet bekendtgrelsen fastslr, at berettigelsen af en rntgenundersgelse afhnger af muligheden for anvendelsen af alternative metoder, der ikke er baseret p ioniserende strling. Den praktiske anvendelse af MR-urografi er imidlertid meget begrnset i Danmark, primrt p grund af den lille MR-scanner-kapacitet.

MR-urografi omfatter i virkeligheden to helt forskellige undersgelsesmetoder. Den frste metode kaldes statisk MR-urografi eller MR-hydrografi. Den bygger p billeddannelse af den statiske vske i nyrens hulrum og urinvejene ved hjlp af sekvenser, hvor vsken fremtrder hvid og de omgivende vv mrke. Nye scannere kan danne de enkelte billeder p brkdele af et sekund, s man undgr uro i billederne.

Fordele ved MR-hydrografien er, at den hurtigt giver information om dilaterede urinveje og lokaliserer obstruktion med meget stor prcision. Samtidig er metoden helt uafhngig af nyrefunktionen, s selv svre grader af ikke-fungerende hydronefrose eller dysplastiske nyreanlg kan erkendes visuelt. P den anden side er det ogs metodens svaghed, at den ikke giver noget indtryk af, hvordan nyrerne fungerer. Andre ulemper er en ret lav oplselighed i billederne, s det kan vre svrt at se prcis, hvad der forrsager obstruktionen, og ikke-dilaterede urinveje er kun delvis synlige.

Metoden kan anvendes til undersgelse af dilaterede urinveje fx ved hydronefrose hos gravide eller brn med anomalier som ureteropelvin striktur, megaureter, dilaterede dobbeltanlg eller store ureteroceler. Den er desuden velegnet til undersgelse af brn med ektopisk ureter fra et svagt fungerende eller stumt dobbeltanlg.

Den anden metode kaldes MR-ekskretionsurografi eller MR-kontrasturografi. Ved denne metode gives en lille dosis furosemid intravenst efterfulgt af MR-kontrast i sdvanlig dosis. Herefter flges kontrastudskillelsen i urinvejene ved hjlp af gentagne scanninger med tredimensional billeddannelse af overlappende tynde (ca. 1 mm) snit. P nye hjfeltsscannere tager denne volumenscanning 15-25 sekunder og foregr, mens patienten holder vejret.

Denne metode giver billeder med meget hj oplselighed og giver, ud over oplysning om morfologi ogs en grov vurdering af nyrernes funktion, og ved sm ndringer i metodikken vil man kunne f prcise oplysninger om nyrefunktionen, alts en MR-renografi.

MR-kontrasturografien er at foretrkke, nr urinvejene er normalt kalibrerede. Den giver prcise oplysninger om selv sm fyldningsdefekter og kortlgger meget prcist en stenose og eventuel kontrastpassage gennem denne (Fig. 1). Metoden forudstter en vis nyrefunktion, men da MR-scanningen er uhyre flsom for selv meget sm mngder kontrast, vil man kunne se kontrastudskillelse hos patienter, hvor den konventionelle urografi m give op pga. manglende udskillelse. MR-kontrasten har en meget lille nefrotoksisk effekt og kan uden problemer gives til patienter med nedsat nyrefunktion.

Ved tumorudredning kan MR-urografien indg som en del af den properative kortlgning, evt. i kombination med MR-angiografi, s man ved en enkelt undersgelse fr kortlagt tumorudbredelse, karforhold og urinveje.

Afhngig af indikationen kan en MR-urografi udfres som en hydrografi med en undersgelsestid p ca. 15 min eller suppleres med en funktionel kontrasturografi (i alt ca. 45 min). De konomiske udgifter til MR-urografi er store, hvis afskrivning af apparaturet indgr i prisberegningen, men det skal opvejes mod det faktum, at undersgelsen ofte kan erstatte flere andre undersgelser, nogle af dem invasive, som fx retrograd pyelografi.

Vi har nu en veletableret, nem og uskadelig metode, som ikke br forbeholdes patienter, der ikke kan tle rntgenkontrast pga. allergi eller nedsat nyrefunktion, men ogs br anvendes i de tilflde, hvor ioniserende strling er mest skadelig, dvs. hos brn og gravide.

The present study was conducted to compare the imaging quality of non-ionic (iohexol) and ionic (sodium and meglumine diatrizoate) contrast agents for intravenous urography in dogs. Twelve clinically healthy adult dogs were randomly divided into two groups I and II, consisting six dogs of either sex in each. Two relevant radiographic exposures i.e. ventro-dorsal and right lateral views were obtained in survey following intravenous urography to evaluate the effectiveness of imaging quality using both non-ionic and ionic contrast agents @ 1100 mg I/kg body weight respectively under general anaesthesia. The radiographic examination of the contrast agent in both groups was assessed immediately after their administration and then at 5, 15, 30 minutes interval by taking ventro-dorsal/lateral radiograph of abdomen. The obtained urograms were evaluated on the basis of nephrogram, pyelogram and cystogram phases. Nephrogram phase showed good visualization (2+) in animals group I as compared to group II which was slightly visualized (1+). The nephrogram phase persisted for a period of 15 minutes in ventro-dorsal radiograph in group I whereas; it was clearly visible upto 5 minute duration in group II. The pyelogram phase was visible upto 5 to 15 minutes time interval in both the groups. Cystogram phase showed good visualization between 15 to 30 minute interval in both the groups. It was concluded that intravenous urography using non-ionic low osmolar iohexol at dose rate of 1100 mg I/kg produced better image quality as compared to ionic high osmolar sodium and meglumine diatrizoate following administration of same dose rate.

Urinary tract infections and mainly urolithiasis are the most routine urological complications encountered in canines which are clinically characterized by haematuria, dysuria or stranguria1 and are difficult to diagnose with plain radiography which is considered to be first investigative tool after clinical examination. Due to minimum differential contrast between abdominal and pelvic organs, it limits the diagnostic precision which can be overcome using contrast agents which specifically further enhance visualization and provide additional information regarding the functional status of the urinary system.

Intravenous urography is an improved radiographic contrast procedure used to enhance visualization of the renal parenchyma, pelvis, ureter as well as urinary bladder2 which are viewed by obtaining a timed series of imaging of abdomen and pelvis after administering intravenous positive contrast media i.e. water soluble iodinated contrast agent. In intravenous urography, the contrast agent is injected into the convenient vein and a series of radiographs are taken. Iodinated contrast agents are ionic high osmolar (sodium and meglumine diatrizoate; sodium and meglumine iothalamate) and non-ionic low osmolar (iohexol and iopamidol) contrast agents. Both these agent are same except that non-ionic do not dissociate in solution and therefore, has less osmotic pressure. Since, the information on the comparison between non-ionic and ionic contrast agents for intravenous urography in dogs is scanty, therefore, the present study was conducted for comparing the imaging quality of non-ionic (iohexol) and ionic (sodium and meglumine diatrizoate) contrast agents for intravenous urography in dogs.

The present study was conducted during April 2020 to September 2020 on 12 apparently healthy adult dogs presented for routine health checkup and vaccination to the Department of Veterinary Surgery and Radiology and Teaching Veterinary Clinical Complex, College of Veterinary Science & A.H. Anjora, Durg (C.G.) India. Twelve dogs were randomly divided into two groups I and II, consisting 6 animals of either sex in each. The animals of group I underwent intravenous urography with non-ionic low osmolar agent (Iohexol) @ 1100mg I/kg body weight while animals of group II received ionic high osmolar agent (sodium and meglumine diatrizoate) @ 1100mg I/kg body weight. The contrast agent in both groups was diluted with an equal amount of 5% dextrose saline solution and infused intravenously over a period of 10-15 minutes under general anaesthesia without abdominal compression. For intravenous urography study, the dogs were kept off feed for 12 hours before the commencement of the radiography. Free access to water was allowed before the start of study. Laxative, Bisacodyl (Dulcolax) 2ml was given to each dog of both the groups, a day before the study. Prior to administration of contrast agents, chlorpheniramine maleate @ 1mg/kg body wt. intramuscularly was administered to animals of group I and group II. In both groups, intravenous urography was done under general anaesthesia using atropine sulphate @ 0.04mg/kg body wt., xylazine hydrochloride @ 1mg/kg body wt. and ketamine hydrochloride @ 15mg/kg body wt. administered intramuscularly followed by maintenance with xylazine and ketamine (1:2) intravenously. Before administration of contrast agents two abdominal survey radiographs (ventro-dorsal and right lateral) were taken. The animal was restraint in dorsal recumbency on X-ray table and cephalic vein of animal was catheterized using 20 gauge butterfly needle for administration of contrast agent which was held in place with adhesive tape. Contrast agents (ionic and non-ionic) @ 1100mg Iodine/kg body wt. was diluted with an equal amount of 5% dextrose saline solution and infused intravenously over a period of 10-15 minutes without abdominal compression. Care was taken that the dose did not exceeded 35gm of iodine as reported by Kealy et al.3 After administration of contrast agents ventro-dorsal/lateral radiograph were taken immediately after infusion and then at 5, 15, 30 minutes intervals.4 The radiograph Machine of 100 mA was used for exposure with CR system (FUJI COMPUTED RADIOGRAPHY) with factors 12mA, 55kV and 100cm FFD. The visibility of the radiographs obtained in both groups were assessed and compared immediately after infusion of contrast agents and also at 5, 15, and 30 minutes intervals. Intravenous urograms were evaluated in three phases: nephrogram, pyelogram and cystogram which indicated sequential phases of contrast medium passing physiologically through the urinary system. Intravenous urogram obtained after infusion of contrast agents were graded using scale : 0-absence of visibility, 1+- slight visibility, 2+- good visibility, 3+- especially good visibility as given by Velesova and Ledecky.5

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