The diagnostic value of magnetic resonance urography for detecting ureteric obstruction: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the diagnostic accuracy of magnetic resonance urography (MRU) and determine its value for detecting ureteric obstruction. METHODS: The electronic databases, including PubMed, Embase and the Cochrane library, were systematically searched for studies published throughout September 2018. The summary of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and receiver operating characteristic (ROC) curves was assessed to evaluate the diagnostic accuracy of MRU. Subgroup analyses were conducted based on the mean age of the included patients (adults or children). RESULTS: Eight studies with a total of 594 patients were included. The summary of the sensitivity and specificity of MRU for diagnosing ureteric obstruction was 0.94 and 0.87, respectively. Furthermore, the pooled PLR and NLR were 7.33 and 0.07, respectively. The DOR of MRU for detecting ureteric obstruction was 95.12. In addition, the summary of the area under the ROC of MRU was 0.96. Finally, the specificity, PLR and area under the ROC of MRU for diagnosing ureteric obstruction in adults were higher than children, while the sensitivity of MRU in adults was lower than children. CONCLUSIONS: These findings suggested a relatively high diagnostic value of MRU for detecting ureteric obstruction. Moreover, the diagnostic accuracy of MRU in adults was higher than in children. KEY MESSAGE Magnetic resonance urography (MRU) in detecting ureteric obstruction has relatively better sensitivity, specificity, PLR, NLR, DOR and AUC. The diagnostic value, including specificity, PLR and AUC of MRU in adults, was higher than in children, while the sensitivity of MRU in adults was lower than in children.

Image quality and pathology assessment in CT Urography: when is the low-dose series sufficient?

BACKGROUND: Our aim was to compare CT images from native, nephrographic and excretory phases using image quality criteria as well as the detection of positive pathological findings in CT Urography, to explore if the radiation burden to the younger group of patients or patients with negative outcomes can be reduced. METHODS: This is a retrospective study of 40 patients who underwent a CT Urography examination on a 192-slice dual source scanner. Image quality was assessed for four specific renal image criteria from the European guidelines, together with pathological assessment in three categories: renal, other abdominal, and incidental findings without clinical significance. Each phase was assessed individually by three radiologists with varying experience using a graded scale. Certainty scores were derived based on the graded assessments. Statistical analysis was performed using visual grading regression (VGR). The limit for significance was set at p = 0.05. RESULTS: For visual reproduction of the renal parenchyma and renal arteries, the image quality was judged better for the nephrogram phase (p < 0.001), whereas renal pelvis/calyces and proximal ureters were better reproduced in the excretory phase compared to the native phase (p < 0.001). Similarly, significantly higher certainty scores were obtained in the nephrogram phase for renal parenchyma and renal arteries, but in the excretory phase for renal pelvis/calyxes and proximal ureters. Assessment of pathology in the three categories showed no statistically significant differences between the three phases. Certainty scores for assessment of pathology, however, showed a significantly higher certainty for renal pathology when comparing the native phase to nephrogram and excretory phase and a significantly higher score for nephrographic phase but only for incidental findings. CONCLUSION: Visualisation of renal anatomy was as expected with each post-contrast phase showing favourable scores compared to the native phase. No statistically significant differences in the assessment of pathology were found between the three phases. The low-dose CT (LDCT) seems to be sufficient in differentiating between normal and pathological examinations. To reduce the radiation burden in certain patient groups, the LDCT could be considered a suitable alternative as a first line imaging method. However, radiologists should be aware of its limitations.

Displasia renal multiquística segmentaria asociada a ureterocele y quistes renales simples en un recién nacido / Multicystic segmentary renal displasia associated to ureterocele and simple renal cysts in a newborn

No disponible

Cicatrices renales en menores de 36 meses ingresados por pielonefritis aguda / Renal scarring in children under 36 months hospitalised for acute pyelonephritis

INTRODUCCIÓN: Una de las causas más frecuentes de infección bacteriana grave en lactantes es la pielonefritis aguda (PNFA), cuya secuela más prevalente a largo plazo es la instauración de cicatrices renales. OBJETIVOS: Revisar la incidencia de cicatrices renales a los 6 meses de un episodio de PNFA en niños menores de 36 meses y su relación con la clínica, las pruebas de imagen y la bacteriología. MÉTODO: Estudio retrospectivo de pacientes de uno a 36 meses previamente sanos ingresados por un primer episodio de PNFA, con un seguimiento mínimo de 6 meses. Se recogieron las variables demográficas junto con bacteriología, ecografía, cistourografía miccional seriada, recidivas y gammagrafía-DMSA. RESULTADOS: Se incluyeron 125 pacientes, 60% varones, la mayoría febriles al ingreso (92%), debido a E. coli (74,6%). Existía antecedente de alteración ecográfica prenatal solo en el 15,4%. La ecografía detectó dilatación de la vía urinaria en el 22,1%. En 70 pacientes se indicó cistourografía miccional seriada: 54,3% sin anomalías, 12,8% con reflujo vesicoureteral (RVU) grado i-iii y 32,9% con RVU iv-v. Seis pacientes presentaban RVU iv-v con ecografías normales. La adherencia a la gammagrafía DMSA a los 6 meses fue solo del 61% de los indicados. De los efectuados (60 casos), en un 44,3% se hallaron cicatrices renales, relacionadas significativamente con la recurrencia y el RVU iv-v, pero no con la bacteriología ni con la elevación de reactantes. CONCLUSIONES: El 44% de las gammagrafías-DMSA de pacientes de uno a 36 meses hospitalizados por PNFA desarrolla cicatrices renales a los 6 meses. Estas se relacionaron con las recurrencias y el RVU grave, pero no con la bacteriología y los reactantes inflamatorios

INTRODUCTION: Acute pyelonephritis (APN) is one of the most common causes of serious bacterial infection in infants. Renal scarring is the most prevalent long-term complication. OBJECTIVES: To review the incidence of renal scarring within 6 months after an episode of APN in children under 36 months and its relationship with imaging studies, clinical settings, and bacteriology. Method. A retrospective study of previously healthy patients aged one to 36 months, admitted for a first episode of APN, with a minimum follow-up of 6 months. Demographic and clinical variables were collected along with bacteriology, renal and bladder ultrasound scan, voiding cystourethrography, DMSA-scintigraphy, and re-infection events. RESULTS: A total of 125 patients were included in the study, of which 60% were male, the large majority (92%) febrile, and due to E. coli (74.6%). There was a history of prenatal ultrasound scan changes in 15.4%. Ultrasound scan found dilation of the urinary tract in 22.1%. Voiding cystourethrography was performed on 70 patients: 54.3% no abnormalities, 12.8% vesicoureteral reflux (VUR) grade i-iii, and 32.9% iv-v grade VUR. Six patients had iv-v grade VUR with a normal ultrasound scan. Adherence to DMSA-scintigraphy at 6 months was only 61% of that indicated. Renal scarring was found in 44.3% of those in which it was performed (60 cases). CONCLUSIONS: Almost half (44%) DMSA-scintigraphy in children aged one to 36 months hospitalised for APN show renal scarring at 6 months, which was found to be associated with the re-infection events and the iv-v grade VUR. There was no relationship between scarring and the bacteriology or the elevations of inflammatory biochemical markers

Refinamientos prácticos en la pieloplastia laparoscópica simplificada / Practical refinaments in simplified laparoscopic pyeloplasty

OBJETIVO: La Pieloplastia Laparoscópica (PL) es el tratamiento de elección de la Obstrucción de la Unión Pieloureteral (OUPU). Presentamos la técnica ilustrada de PL con tres trócares con refinamientos y consejos prácticos. MÉTODOS: Se describen varias maniobras paso a paso, para optimizar la exposición y simplificar la ejecución de la cirugía. Un total de trece pacientes con OUPU con criterios para tratamiento quirúrgico fueron incluidos. Todos ellos fueron operados de PL empleando 3 trócares. Los datos demográficos, perioperatorios y de seguimiento fueron recolectados de manera retrospectiva. RESULTADOS: El tiempo operatorio promedio fue de 132 minutos, no hubo conversión a cirugía abierta ni se requirió inserción de trocar adicional en ninguno de los casos. No se reportaron complicaciones perioperatorias ni post-operatorias. Tres casos requirieron inserción de catéter doble J previamente por dolor. Cinco pacientes requirieron nefroscopia flexible con CO2 para la extracción de litiasis caliciales. Todos los casos presentaron desaparición del dolor. Conlcuisones: La PL con tres trocares es una técnica factible y segura en la corrección quirúrgica de la OUPU, y las maniobras presentadas en este estudio simplifican el procedimiento y pueden tener aplicación en otras intervenciones laparoscópicas

OBJECTIVES: Laparoscopic pyeloplasty (LP) is the treatment of choice for ureteropelvic junction obstruction (UPJO). We present the 3-trocars LP technique with several considerations and practical advices. METHODS: Several maneuvers to optimize exposure and simplifying the implementation of the operation were showed. A total of thirteen patients with UPJO and criteria for surgical treatment were included, and were operated using the 3 trocars LP technique. Demographic data, perioperative and follow-up were collected retrospectively. RESULTS: Mean operative time was 132 minutes. No conversion to open surgery was registered and additional trocar insertion was not required. Neither perioperative complications nor postoperative complications were reported. Three patients needed ureteral stenting preoperatively for pain. Five patients required flexible nephroscopy with CO2 for extraction of calyceal stones. The pain was controlled in all cases. CONCLUSIONS: The LP is a feasible and safe technique for the surgical correction of UPJO, and maneuvers presented in this study simplify the procedure and may be applied in other laparoscopic procedures

Vejiga neurógena no neurogénica congénita (VNNN C): estudio evolutivo / Congenital non-neurogenic neurogenic bladder: evolutionary study

Introducción. Dentro de los trastornos funcionales vesicales de vaciado o disfunciones miccionales, uno de los más conocidos es el síndrome de Allen-Hinman, considerado como un proceso adquirido. Recientemente, se han descrito varios casos de aparición congénita, por lo que es una patología muy poco conocida, originando graves errores diagnósticos y terapéuticos. Caso clínico. Niña de 15 años de edad, controlada desde el nacimiento por presentar una gran distensión abdominal, evacuando 400 ml de orina; siendo los estudios realizados compatibles con vejiga neurógena no neurogénica congénita mediante el tratamiento médico y sondajes vesicales intermitentes, se ha conseguido que no exista afectación renal. Conclusiones. Consideramos que la VNNN congénita es excepcional. Gracias al tratamiento seguido, se ha logrado que no exista afectación renal, y ninguna complicación. Desde hace unos 5 años, a veces, presenta deseos de micción, que no se acompaña de la misma, por lo que debemos seguir realizando un control evolutivo preciso (AU)

Introduction. The Allen-Hinman syndrome, considered being a adquired process, is one of the best known within functional disorders of emptying, or voiding dysfunctions. Recently, several cases describing a congenital appearance has been seen. It is a very little-known pathology, resulting in serious diagnostical and therapeutical errors. Clinical case. A 15 year old girl, known since birth to present a great abdominal distension, removing 400 ml of urine; realizing through studies a compatibility with congenital non-neurogenic neurogenic bladder. Medical treatment and intermittent catheterization has come to show no renal involvement or any complications with the treatment. Conclusions. We consider that congenital VNNN is exceptional. Thanks to continued treatment, We have come to conclude there being no renal involvement as well as any complications with the treatment. During the last five years she has occasionally presented the desire to urinate, both by day time and night time, without urination following. Not knowing if it can be a future-related bladder, we have to secure a evolutionary control (AU)

Determination of optimal imaging settings for urolithiasis CT using filtered back projection (FBP), statistical iterative reconstruction (IR) and knowledge-based iterative model reconstruction (IMR): a physical human phantom study.

OBJECTIVE: The purpose of this study was to compare CT image quality for evaluating urolithiasis using filtered back projection (FBP), statistical iterative reconstruction (IR) and knowledge-based iterative model reconstruction (IMR) according to various scan parameters and radiation doses. METHODS: A 5 × 5 × 5 mm(3) uric acid stone was placed in a physical human phantom at the level of the pelvis. 3 tube voltages (120, 100 and 80 kV) and 4 current-time products (100, 70, 30 and 15 mAs) were implemented in 12 scans. Each scan was reconstructed with FBP, statistical IR (Levels 5-7) and knowledge-based IMR (soft-tissue Levels 1-3). The radiation dose, objective image quality and signal-to-noise ratio (SNR) were evaluated, and subjective assessments were performed. RESULTS: The effective doses ranged from 0.095 to 2.621 mSv. Knowledge-based IMR showed better objective image noise and SNR than did FBP and statistical IR. The subjective image noise of FBP was worse than that of statistical IR and knowledge-based IMR. The subjective assessment scores deteriorated after a break point of 100 kV and 30 mAs. CONCLUSION: At the setting of 100 kV and 30 mAs, the radiation dose can be decreased by approximately 84% while keeping the subjective image assessment. ADVANCES IN KNOWLEDGE: Patients with urolithiasis can be evaluated with ultralow-dose non-enhanced CT using a knowledge-based IMR algorithm at a substantially reduced radiation dose with the imaging quality preserved, thereby minimizing the risks of radiation exposure while providing clinically relevant diagnostic benefits for patients.

Ultra low-dose VCUG in children using a modern flat detectorunit.

OBJECTIVES: To assess dose area products (DAP) and effective doses (ED) of voiding cystourethrography (VCUG) in children using optimized protocols on a modern flat detector unit. METHODS: DAP and ED were evaluated in 651 VCUG (316 girls, median age: 2.25 years) between 2009 and 2012. DAP was analyzed in relation to patient characteristics (gender, age, presence of pathological findings) and experience of performing physician using analysis of variance. ED values were estimated using adapted conversion factors from the literature. Diagnostic image quality was validated by two experienced physicians using a 3-point scale. RESULTS: Median DAP/ED was 0.5 cGycm(2)/4.56 µSv (boys: 0.6 cGycm(2)/6.16 µSv; girls: 0.4 cGycm(2)/3.54 µSv). In 300 studies without pathologic findings DAP was 0.35 cGycm(2), whereas 351 studies with pathologic findings had a median DAP of 0.7 cGycm(2). No significant relationship between DAP and experience of radiologist was observed. Image validation resulted in an overall good to excellent rating. CONCLUSIONS: DAP and ED can be markedly reduced in paediatric VCUG performed with optimized protocols on modern equipment without a noticeable decrease in diagnostic image quality. KEY POINTS: • Voiding cystourethrography is a comprehensive examination in diagnosing vesicoureteral reflux (VUR). • Radiation reduction is achieved in VCUG through modern equipment and optimized protocols. • Low-dose VCUG is possible without noticeable decrease in diagnostic image quality.

Uréter retrocavo no obstructivo junto con megauréter terminal. Aporte de un caso / Retrocaval non-obstructive ureter and terminal megaureter. Case report

No disponible

Expulsión espontánea de litiasis de gran tamaño / Spontaneous expulsion of large ureteral lithiasis

No disponible

Diagnostic imaging of lower urinary tract disease.

Diagnostic imaging is routinely performed in small animals with lower urinary tract disease. Survey radiographs allow identification of radiopaque calculi, gas within the urinary tract, and lymph node or bone metastases. Cystography and urethrography remain useful in the evaluation of bladder or urethral rupture, abnormal communication with other organs, and lesions of the pelvic or penile urethra. Ultrasonography is the modality of choice for the diagnosis of most disorders. Computed tomography and magnetic resonance imaging are useful in evaluating the ureterovesical junction and intrapelvic lesions, monitoring the size of lesions, and evaluating lymph nodes and osseous structures for metastases.

Endometriosis ureteral en paciente monorrena. Presentación del caso y revisión de la literatura / Ureteral endometriosis in a single-kidney patient. Case report and literatura review

La endometriosis se define como la presencia de tejido endometrial funcionante localizado de manera ectópica fuera de la cavidad uterina. La afectación del aparato urinario es poco frecuente evidenciándose únicamente en el 5% de las pacientes con endometriosis. Presentamos el caso de una paciente de 44 años monorrena izquierda, que ingresa en el servicio de urología por hidronefrosis y dolor en fosa renal de un mes de evolución. Se realiza estudio de uropatía obstructiva izquierda evidenciándose efecto masa en uréter distal izquierdo. Dados los hallazgos y los antecedentes de la paciente (monorrena izquierda) se decide realizar ureterectomía y vejiga psoica, con toma de biopsia intraoperatoria. El estudio histopatológico de la pieza reveló el diagnóstico de endometriosis ureteral. La paciente en la actualidad se encuentra asintomática y con función renal normal (AU)

Endometriosis is defined as the presence of ectopic endometrial tissue outside the normal confines of the uterine cavity. Urinary tract involvement is uncommon, its incidence being about 5%. We report the case of a 44 year-old patient with a single left kidney admitted to the urology department of our hospital diagnosed with left-sided hydronephrosis. She also complained of pain in the left renal fossa for more than a month. A study of left obstructive uropathy was performed, revealing a mass effect in the left distal ureter. Given the findings and the patient's history (a single left kidney), we decided to perform ureterectomy and to fix the bladder to the psoas, as well as to perform an intraoperative biopsy. The histopathological report of the surgical specimen confirmed the previous diagnosis of ureteral endometriosis. The patient is currently asymptomatic and has normal renal function (AU)

Riñón en herradura, enfermedad litiásica y adenocarcinoma de próstata. Presentación de un caso clínico / Horseshoe kidney, stone disease and prostate cancer: a case presentation

El riñón en herradura es la anomalía congénita de fusión más frecuente. Se presenta en el 0,25% de la población ó en 1 de cada 400. Más frecuente en el varón (proporción de 2:1). La litiasis es una de las complicaciones más frecuentes del riñón en herradura, aunque puede haber otras como: dolor abdominal, infecciones urinarias, hematuria, hidronefrosis, traumatismos y aparición de tumores, siendo los más comúnmente asociados el hipernefroma y el tumor de Wilms. Describimos el caso de un varón portador de riñón en herradura, enfermedad litiásica y adenocarcinoma de la próstata. En la literatura médica revisada encontramos un caso portador de esta entidad que presentó un carcinoma transicional de próstata (AU)

The horseshoe kidney is the most common congenital renal fusion anomalies. It occurs in 0.25% of the population, or 1 in every 400 people. It is more frequent in males (ratio 2:1). The most observed complication of horseshoe kidney is stone disease, although there may be others such as, abdominal pain, urinary infections, haematuria, hydronephrosis, trauma and tumours (most commonly associated with hypernephroma and Wilms tumour). We describe a case of a male patient with horseshoe kidney, stone disease and adenocarcinoma of the prostate. One carrier of this condition who suffered a transitional cell carcinoma of the prostate was found in a review of the literature (AU)

Computed tomography urography 1: techniques and technology.

Contrast-enhanced computed tomography urography has become possible because of the development of multidetector technology, which has evolved to try and increase its diagnostic efficacy and reduce the radiation exposure. This review highlights important aspects of computed tomography urography as an imaging technique.

Hematoma escrotal idiopático / Idiopathic scrotal hematoma

Los hematomas escrotales son entidades patológicas frecuentes en la práctica clínica habitual. La relativa exposición del escroto a potenciales traumatismos (accidentes de tráfico, deportes violentos, agresiones intencionadas, etc.), la no despreciable cifra de iatrogenia quirúrgica (en relación con la gran cantidad de cirugías locorregionales que se realizan diariamente: vasectomías, cirugía herniaria, cirugía del varicocele, del escroto, etc.) y la cada vez mayor utilización de terapias anticoagulantes, así lo demuestran. Lo que ya no es tan frecuente es la aparición de lo que proponemos denominar hematomas escrotales criptogenéticos. Estas entidades forman una abigarrada miscelánea debida a afecciones infrecuentes, e incluso idiopáticas (de causas imposibles de filiar), como los 2 casos objeto de esta comunicación. Su diagnóstico es difícil y debe ser preciso para un correcto abordaje de su tratamiento, evitando cirugías innecesarias o llevando a cabo aquellas que estén indicadas, ya que en no pocos casos puede tratarse de una enfermedad grave. Los hematomas escrotales idiopáticos o criptogenéticos suelen ser manifestaciones locales de complejas dolencias sistémicas o asociaciones de ellas en un mismo paciente y momento. Por todo lo anteriormente expuesto, un enfoque multidisciplinar se impone, así como la utilización de todos los medios diagnósticos disponibles y una vigilancia estrecha hasta la resolución. Los 2 casos que comunicamos intentan ilustrar lo dicho y ayudar, a través de su conocimiento, a resolver posibles futuras situaciones similares(AU)

Scrotal hematomas are frequent pathological conditions in the usual clinical practice. These include the relative exposition of the scrotum to potential traumatisms (traffic accidents, violent sports, intentional aggressions, etc.), the large number of surgical iatrogenia (in relation to the large number of locoregional surgeries performed daily: vasectomies, hernia surgery, varicocele surgery, scrotal surgery, etc.) and the increasingly greater use of anticoagulant therapies. However, the appearance of what we propose to call cryptogenic scrotal hematomas is not so frequent. These conditions form a miscellaneous collection due to infrequent, and even idiopathic conditions (with causes that are impossible to classify) such as the 2 cases being reported herein. They are difficult to diagnose, and this diagnosis should be precise in order to correctly approach their treatment and to avoid unnecessary surgeries or to carry out those indicated, since it may be a serious condition in many cases. Idiopathic or cryptogenic scrotal hematomas are generally local manifestations of complex systemic conditions or associations of them in a single patient and time. Due to the above, a multidisciplinary approach must be made, using all the diagnostic means available, along with close monitoring until their resolution. An attempt is made in both cases reported to illustrate the above and to help, through their knowledge, to resolve possible future similar situations(AU)

CT of urolithiasis: comparison of image quality and diagnostic confidence using filtered back projection and iterative reconstruction techniques.

RATIONALE AND OBJECTIVES: To compare the image quality and diagnostic confidence of low-dose computed tomography (CT) of urololithiasis using filtered back projection (FBP) and iterative reconstruction techniques (IRT). MATERIALS AND METHODS: A 4.8 × 4.3 × 5.2 mm(3) uric acid ureteral stone was placed inside an anthropomorphic Alderson phantom at the pelvic level. Fifteen scans were performed on a 64-row dual-source CT system using different tube voltages (80, 100, and 120 kV) and current-time products (8, 15, 30, 70, and 100 mAs). Image reconstruction using FBP and IRT (iterative reconstruction in image space) resulted in 30 data sets. Objective image quality was evaluated by noise measurements. Effective doses were estimated for each data set with use of an established dosimetry program. Subjective image quality and confidence level were rated by two radiologists. RESULTS: Noise was systematically lower for images reconstructed with IRT compared to FBP (55 ± 30 vs 65 ± 26 Hounsfield units; P = .004) for volume CT dose index values above about 0.6 mGy (or an effective dose of about 0.4 mSv for both sexes). For the 14 scans rated to have diagnostic image quality, the estimated effective doses ranged from 0.3 to 2.5 mSv for males and from 0.4 to 3.1 mSv for females. Subjective image quality and diagnostic confidence for IRT was not significantly better than those for FBP. CONCLUSIONS: In a phantom study for CT of urolithiasis, IRT improves objective image quality compared to FBP above a certain dose threshold. However, this does not translate into improved subjective image quality or a higher degree of confidence for the diagnosis of high-contrast urinary stones.

Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT.

PURPOSE: The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. MATERIALS AND METHODS: Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, digital fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. RESULTS: There were basically no limitations regarding image quality in digital fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. CONCLUSIONS: The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.