Volume 42 Issue 5
Oct.  2018
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Ectopic kidney SPECT/CT imaging in a patient with congenital anal atresia

  • Corresponding author: Keyi Lu, lu-ky@163.com
  • Received Date: 2018-03-14
  • SPECT/CT imaging was conducted on an ectopic kidney in a patient with congenital anal atresia. Most cases of ectopic kidney are found by chance during physical examination given the lack of the specific clinical symptoms of this condition during its early stage. At present, the diagnosis of ectopic kidneys mainly depends on ultrasound and CT. Renal dynamic imaging, however, provides advantages for the evaluation of the individual functions of ectopic kidneys. Gate's method was used to detect the glomerular filtration rate of an ectopic kidney. Literature review was performed to obtain a deep understanding of Gate's method. The following guiding conclusions were drawn:1. The co-occurrence of other organ malformations in newborns with kidney malformations should receive close attention. Early detection and intervention are necessary to manage ectopic kidneys. 2. SPECT/CT enables the advantageous one-stop diagnosis of the morphology and function of ectopic kidneys. 3. Gate's method requires proper correction for the glomerular filtration rate determination of kidneys with special characteristics.
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  • [1] Tonnesen KH, Mogensen P, Wolf H, et al. Residual kidney function after unilateral nephrectomy. Pre-and postoperative estimation by renography and clearance measurements[J]. Scand J Urol Nephrol, 1976, 10 (2):130-133. DOI:10.3109/00365597609179672.
    [2] Gehan EA, George SL. Estimation of human body surface area from height and weight[J]. Cancer Chemother Rep, 1970, 54 (4):225-235.
    [3] Blaufox MD, Aurell M, Bubeck B, et al. Report of the Radionuclides in Nephrourology Committee on renal clearance[J]. J Nucl Med, 1996, 37 (11):1883-1890. DOI:10.1016/S0022-5347 (01)62326-7.
    [4] 杨红, 刘育青, 李聪革, 等. γ照相法GFR与双血浆标本法GFR的比较[J].中华核医学杂志, 2000, 20 (2):74. DOI:10.3760/cma.j.issn.0253-9780.2000.02.022.Yang H, Liu YQ, Li CG, et al. Comparison of glomerular filtration rate measurements with gamma camera methods and two plasma sample methods[J]. Chin J Nucl Med, 2000, 20 (2):74. doi: 10.3760/cma.j.issn.0253-9780.2000.02.022
    [5] Joung HS, Guerrero AL, Tomita S, et al. Imperforate Anus with Jejunal Atresia Complicated by Intestinal Volvulus:A Case Report[J]. J Neonatal Surg, 2016, 5 (4):59. DOI:10.21699/jns.v5i4.458.
    [6] Tveter KJ, Fonkalsrud EW, Goodwin WE. Single vaginal ectopic ureter and solitary kidney, associated with imperforate anus and other malformations. A case report[J]. Scand J Urol Nephrol, 1980, 14 (1):119-121. doi: 10.3109/00365598009181203
    [7] Eckford SD, Westgate J. Solitary crossed renal ectopia associated with unicornuate uterus, imperforate anus and congenital scoliosis[J]. J Urol, 1996, 156 (1):221. doi: 10.1016/S0022-5347(01)66005-1
    [8] Gates GF. Computation of glomerular filtration rate with Tc-99m DTPA:an in-house computer program[J]. J Nucl Med, 1984, 25 (5):613-618.
    [9] 麻广宇, 邵明哲, 陈云爽, 等.肾脏深度对SPECT测定肾小球滤过率的影响[J].中国医学影像技术, 2013, 29 (5):800-804. DOI:10.13929/j.1003-3289.2013.05.034.Ma GY, Shao MZ, Chen YS, et al. Impact of kidney depth on the measurement of glomerular filtration rate with SPECT[J]. Chin J Med Imaging Technol, 2013, 29 (5):800-804. doi: 10.13929/j.1003-3289.2013.05.034
    [10] 李乾, 张春丽, 王荣福.肾动态显像测定肾小球滤过率的影响因素[J].中国医学影像技术, 2004, 20 (6):962-964. DOI:10.3321/j.issn:1003-3289.2004.06.046.Li Q, Zhang CL, Wang RF. Influence elements in the process of dynamic renal imaging to measure glomerular filtration rate[J]. Chin J Med Imaging Technol, 2004, 20 (6):962-964. doi: 10.3321/j.issn:1003-3289.2004.06.046
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Ectopic kidney SPECT/CT imaging in a patient with congenital anal atresia

    Corresponding author: Keyi Lu, lu-ky@163.com
  • Department of Nuclear Medicine, the First Hospital of Shanxi Medical University, Molecular Imaging Precision Medicine Collaborative Innovation Center of Shanxi Medical University, Taiyuan 030001, China

Abstract: SPECT/CT imaging was conducted on an ectopic kidney in a patient with congenital anal atresia. Most cases of ectopic kidney are found by chance during physical examination given the lack of the specific clinical symptoms of this condition during its early stage. At present, the diagnosis of ectopic kidneys mainly depends on ultrasound and CT. Renal dynamic imaging, however, provides advantages for the evaluation of the individual functions of ectopic kidneys. Gate's method was used to detect the glomerular filtration rate of an ectopic kidney. Literature review was performed to obtain a deep understanding of Gate's method. The following guiding conclusions were drawn:1. The co-occurrence of other organ malformations in newborns with kidney malformations should receive close attention. Early detection and intervention are necessary to manage ectopic kidneys. 2. SPECT/CT enables the advantageous one-stop diagnosis of the morphology and function of ectopic kidneys. 3. Gate's method requires proper correction for the glomerular filtration rate determination of kidneys with special characteristics.

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  • 异位肾是肾脏定位出现异常,可异位于骨盆、髂窝、腹部、胸腔或双肾交叉异位。异位肾常伴肾旋转不良及其他畸形,如尿道下裂、隐睾等,但合并肛门闭锁较罕见。部分异位肾形态不规则,在临床上易被误认为是肿瘤而被切除,从而给患者造成伤害。肾动态显像不但可以反映肾血流灌注情况、上尿路引流排泄情况,还可以采用Gate′s法测定总肾及分肾肾小球滤过率(glomerular filtration rate,GFR),结合SPECT/CT融合显像,可以从解剖结构及功能方面对异位肾进行多方面地诊断及鉴别诊断。Gate′s法测定GFR的影响因素较多,如肾脏深度,但通过矫正,不管是从后位还是从前位进行矫正,都获得了较满意的GFR。笔者报道了先天性肛门闭锁患者成年后体检偶然发现异位肾,并通过查阅文献,对Gate′s法进行了较深入的分析学习。

1.   患者资料
  • 患者男性,19岁,身高175 cm,体重63 kg,出生时肛门闭锁,出生后第3天在山西省儿童医院行肛门成形术。2016年9月17日因碰撞后出现左侧睾丸肿胀、触痛,于当地医院就诊,检查发现尿蛋白“++”,血肌酐、血尿酸水平稍高(具体数值不详)。2016年10月13日在我院复查,尿蛋白“++”、血肌酐水平为98.8 μmol/L(参考范围49.0~90.0 μmol/L)、血尿酸水平为446 μmol/L(参考范围210~440 μmol/L),泌尿系超声检查结果显示双肾区未探及肾脏轮廓,左下腹腹腔内可见一肾脏回声,大小约10.2 cm×5.1 cm,被膜光整,皮质回声均匀,肾窦居中未见分离,双侧输尿管未见扩张。提示:左下腹异位肾可能。

    为进一步评估肾功能,2016年10月20日在我院行99Tcm-DTPA肾动态显像(采用德国西门子公司生产的Symbia T16型双探头SPECT/CT,配低能高分辨率平行孔准直器,能峰140 keV,窗宽±20%;99Tcm-DTPA由北京欣科思达医药科技有限公司提供),并采用双血浆法测定GFR。肾动态显像结果(后位图像):血流灌注相示正常双肾区未见血流灌注影,左下腹可见一较大团块状显像剂分布异常浓聚影;功能相(图 1中A)示双肾区未见双肾影,左下腹可见一具有肾脏功能组织的巨大显像剂分布异常增高影,考虑为腹腔内异位肾脏组织,双侧输尿管隐约显影。双血浆法GFR与Gate′s法GFR矫正前(后位图像勾画ROI,肾脏深度采用Tonnesen公式[1]计算)统一采用Gehan和George推导的体表面积公式[2]进行标化。最终结果:Gate′s法GFR矫正前为14.4 mL·min-1·1.73 m-2;双血浆法GFR为66.0 mL·min-1·1.73 m-2

    重新处理了前位图像(图 1中B)后发现肾脏轮廓在前位图像上明显比在后位图像上清晰,考虑异位肾位置靠前,明显偏离了肾脏的正常位置,根据Gate′s法的原理,需要对肾脏深度进行矫正。

    若仅对肾脏深度进行矫正,只行CT扫描即可,但为了更好地观察异位肾的肾盂、输尿管集合及排泄情况,笔者做了SPECT/CT局部断层融合显像。经患者及家属知情同意,患者于常规肾动态显像检查的次日静脉注射179.5 MBq 99Tcm-DTPA,5 min后行SPECT/CT局部断层融合显像,结果(图 1中CD)显示:双肾区未见肾组织,第3至5腰椎左前方可见单一肾影,大小约为8.8 cm×5.4 cm×9.6 cm(左右径×前后径×上下径),边界清楚,呈分叶状,其内可见显像剂分布弥漫性增高,并于左右两分叶内可见显像剂局灶性浓聚影,左侧明显,两者下极可见条状显像剂摄取影。考虑腹腔交叉融合异位肾,含有两个肾盂及两条输尿管,左肾体积基本正常,右肾体积缩小,发育不全。

    根据CT断层图像,采用异位肾的最大横断面(图 1中E)测量了肾脏的后位深度H(肾脏的中心到后背体表皮肤的垂直距离)和前位深度H(肾脏的中心到腹部体表皮肤的垂直距离)。依据Gate′s法基本原理测得GFR(处理前位图像且以肾脏的前位深度进行校正后获得的GFR)和GFR(处理后位图像且以肾脏的后位深度进行校正后获得的GFR)。结果如下。

    前位矫正:

    后位矫正:

    其中,a为肾脏的前缘到腹部体表皮肤的垂直距离,b为肾脏的后缘到腹部体表皮肤的垂直距离,c为肾脏的前缘到背部体表皮肤的垂直距离,d为肾脏的后缘到背部体表皮肤的垂直距离。肾脏深度经过矫正后,前位、后位测得的GFR数值非常接近,并与目前国际公认的“金标准”双血浆法[3]测得的GFR数值差别不大,误差在可接受范围内[4]。本例患者最后诊断为腹腔交叉融合异位肾,肾功能轻度受损。

2.   讨论
  • 胎儿期肾脏胚芽位于盆腔内,随着胎儿生长,肾脏逐渐上升到正常位置,如果肾血管发育发生障碍或引向错误,阻碍了肾脏上升或上升到异常位置,即形成异位肾。异位肾以单侧居多,单侧者又以左侧为多,大多发育差,输尿管较短,常伴旋转不良。少数异位肾横过中线异位至对侧,称交叉异位肾。新生儿异位肾的临床表现各异,没有特征性的临床症状,绝大多数患者为偶然发现。在活产新生儿中,肛门直肠畸形的发生率约为1/5000,大约50%的肛门直肠畸形的新生儿中伴有一个或多个其他器官畸形[5]。然而,在同一例患者中出现肛门闭锁合并交叉融合异位肾极为罕见,国内尚没有相关报道,国外仅有2篇相关报道[6-7]。本病例的报道提醒临床医师,对发现有一器官畸形的新生儿,应该留意其是否合并其他器官的畸形,应做到早发现早干预。

    Gate′s法测定GFR是一种以肾脏摄取99Tcm-DTPA后的放射性计数来评价肾功能的方法。该法的影响因素较多,如:肾脏ROI确定、肾脏深度测定、本底校正、衰减校正、注射质量、注射前后注射器放射性计数的测定及肾脏本身结构的改变等。Gates[8]认为肾脏深度的校正较其他因素更为重要。肾脏深度的测定方法常用的有4种:①利用核医学侧位显像进行测量;②Tonnesen法,该方法是在患者坐位时,B超探头以倾斜的角度从脊柱两侧测量双肾深度,然后用测定值推导出肾脏深度估算公式,该法容易低估肾脏深度,德国SIEMENS公司Symbia T16 SPECT/CT默认的肾脏深度估算公式正是Tonnesen公式;③利用超声测定;④利用CT测定。其中,CT测定的方法较为准确[9]。当肾脏深度误差为1 cm时,GFR就会产生14%的偏差,临床上认为这种偏差是可以接受的,所以左右两侧肾脏深度的差异小于1 cm时,可以认为两肾深度近似[10]。对于异位肾、移植肾等肾脏位置明显失常的病例需要对肾脏深度进行矫正,以求获得更准确的GFR结果。

    目前确诊异位肾主要依赖影像学检查,如CT、静脉肾盂造影、MRI、超声等,其中,CT的诊断价值尤为突出,CT平扫加增强扫描可清楚显示异位肾与正常肾、肾蒂及其他周围结构的关系,CT血管成像及CT尿路成像可直观显示肾血管的起源、走行及集合系统。随着SPECT/CT的逐渐普及,其优势也在逐渐显现,异位肾的形态及功能诊断可以一站式解决,这对于临床医师正确诊断异位肾及评估肾功能皆具有非常重要的意义。本病例的报道旨在提醒临床医师对该种病例进行适当关注,以及进一步认识异位肾SPECT/CT肾动态显像,另外,也在某些方面对核医学科医师正确、灵活应用Gate′s法评估肾功能提供了指导。

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