Physiology of renal medullary tip hyperattenuation at unenhanced CT: Urinary specific gravity and the NaCl concentration gradient
Physiology of renal medullary tip hyperattenuation at unenhanced CT: Urinary specific gravity and the NaCl concentration gradient
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DOI：
10.1148/radiol.2471070585
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发表时间：
2008-04-01
期刊：
影响因子：
19.7
通讯作者：
Yeh, Benjamin M.
中科院分区：
文献类型：
--
作者：
Hsu, Christopher T.;Wang, Zhen J.;Yeh, Benjamin M.
目的：回顾性研究肾髓质尖端高衰减的生理学在未增强的计算机断层扫描（CT）。材料和方法：本回顾性单机构研究IRB批准和健康保险责任法案兼容。放弃知情同意。连续100例单侧输尿管梗阻患者（女性53例，平均年龄52岁;男性47例，平均年龄48岁; P = 0.39）和34例单侧输尿管梗阻患者（女性11例，平均年龄49岁;男性23例，平均年龄45岁; P = 0.54）接受了同期尿分析和非增强CT检查。在CT时，测量膀胱尿液衰减，两名阅片者记录了肾髓质尖端高衰减的存在。对于梗阻的肾脏（n = 34），还记录了肾盂尿衰减。髓尖高密度的存在与尿比重相关。探讨髓尖高衰减的生理基础，（范围，0-2000 mosm/kg）并通过使用线性回归与溶质浓度相关。CT显示肾髓质尖高密度的患者平均尿比重较高阅读者1和阅读者2分别为1.023和1.022，而无阅读者分别为1.015和1.016，P均<0.05。比重与较高的尿衰减相关（r = 0.40，P <0.001）。对于34例单侧尿路梗阻患者，梗阻（两名阅片者各有两个肾脏）的髓尖高衰减较非梗阻（分别为11和15个肾脏，P <0.005）肾脏少见，梗阻肾盂（7.4 HU）的平均尿衰减低于膀胱（11.4 HU）（P <0.005）。结果显示，在不同浓度的NaCl溶液中，每增加100 mosm/kg，尿密度增加3.6 HU（r = 0.99，P <0.001），但在不同浓度的尿素溶液中，尿密度无明显变化。(c)RSNA，2008年。
Purpose: To retrospectively investigate the physiology of renal medullary tip hyperattenuation at unenhanced computed tomography (CT).Materials and Methods: This retrospective single-institution study was IRB approved and HIPAA compliant. Informed consent was waived. One hundred consecutive patients (53 women, mean age, 52 years; 47 men, mean age, 48 years; P = .39) without and 34 (11 women, mean age, 49 years; 23 men, mean age, 45 years; P = .54) with unilateral ureteral obstruction underwent contemporaneous urinalysis and unenhanced CT. At CT, bladder urine attenuation was measured and two readers recorded the presence of renal medullary tip hyperattenuation. For obstructed kidneys (n = 34), renal pelvic urine attenuation was also recorded. The presence of medullary tip hyperattenuation was correlated with urinary specific gravity. To investigate the physiologic basis of medullary tip hyperattenuation, attenuations for NaCl and urea phantoms (range, 0-2000 mosm/kg) were recorded and correlated to solute concentrations by using linear regression.Results: Patients with renal medullary tip hyperattenuation seen at CT had higher mean urinary specific gravity (1.023 and 1.022 for readers 1 and 2, respectively) than those without (1.015 and 1.016, respectively, both P < .05). The specific gravity correlated with higher urine attenuation (r = 0.40, P < .001). For the 34 patients with unilateral urinary obstruction, medullary tip hyperattenuation was less commonly seen in obstructed (two kidneys each for both readers) than nonobstructed (11 and 15 kidneys, respectively, both P < .005) kidneys and mean urine attenuation was lower in the obstructed renal pelvis (7.4 HU) than in the bladder (11.4 HU) (P < .005). Phantoms showed a 3.6-HU increase per 100-mosm/kg increase in NaCl concentration (r = 0.99, P < .001) but no change in attenuation with different urea concentrations.Conclusion: Renal medullary tip hyperattenuation at unenhanced CT reflects increased urinary specific gravity, likely related to high medullary tip NaCl concentrations. (c) RSNA, 2008.