Differential density of normal renal parenchyma on nonenhanced CT: a new observation

Reproducibility of a novel computed-tomography based measurement of renal papillary density in the Framingham Heart Study

BACKGROUND

Renal papillary calcification is a compelling candidate risk factor for chronic kidney disease (CKD) and nephrolithiasis. Renal papillary density (RPD), as assessed by computed tomography (CT), is a potential marker for calcification that has not been well studied. We developed a protocol to measure RPD using CT scans and assessed its reproducibility in participants from the Framingham Heart Study.

METHODS

We assessed RPD of right kidneys from a single abdominal CT slice in 100 representative participants from the Framingham Heart Study (47% female, mean age 59.9 years) using a novel protocol. We selected the kidney slice with the most open sinus space and assessed RPD using the average of three 20 mm(2) ellipses from upper, middle and lower papillary regions. Two different readers performed RPD measurements and the first reader repeated all measurements to determine both intra- and inter-reader reproducibility, respectively.

RESULTS

Of 100 total individuals included in the replication dataset, six were excluded for poor scan quality. Average RPD across all individuals was 48.7 ± 4.7 (range 38.7-61.7) Hounsfield Units (HU). The intra- and inter-reader correlation coefficients were 0.86 and 0.79, respectively. Bland-Altman analysis suggested no systematic bias between the different reads.

CONCLUSION

Measuring RPD is practical and reproducible using MDCT scans from a small sample of a community-based cohort.

Visualization of renal medullary hyperattenuation at unenhanced CT: what is the effect of furosemide administration?

PURPOSE

To retrospectively investigate the effects of furosemide on the visualization of renal medullary hyperattenuation at unenhanced computed tomography (CT).

MATERIALS AND METHODS

This retrospective single-institution study was HIPAA compliant and approved by the institutional review board; requirement for informed consent was waived. This study identified 289 consecutive patients (152 men, 137 women; mean age, 59 years) without ureteral obstruction who underwent unenhanced scanning as part of CT urography; of these, 178 patients did not receive intravenous furosemide prior to imaging and 111 did. The presence of renal medullary hyperattenuation, renal stones, and bladder urine attenuation levels were recorded and compared between patients who did not receive furosemide prior to imaging and those who did by using the chi(2) and unpaired Student t tests. A multiple logistic regression model was used to evaluate independent predictors of visualization of renal medullary hyperattenuation.

RESULTS

Renal medullary hyperattenuation was seen less commonly in patients who received furosemide (27 of 111, 24%) than in those who did not receive furosemide prior to imaging (79 of 178, 44%, P = .001). Bladder urine attenuation was lower in patients who received furosemide (-0.1 HU) compared with those who did not (6.4 HU, P < .001). A multiple logistic regression model revealed independent associations between the visualization of renal medullary hyperattenuation and the absence of furosemide administration (P = .002), younger age (P < .001), and presence of renal stones (P = .047).

CONCLUSION

Furosemide administration prior to unenhanced CT is associated with decreased visualization of renal medullary hyperattenuation.

Advances in the imaging of renal infection. Helical CT and modern coordinated imaging

Traditionally, imaging of renal infections was largely through a multimodality approach. Excretory urography, ultrasonography, nuclear scintigraphy, and CT all played major roles; however, in recent years, CT has increased in prominence in the imaging and evaluation of renal infection. Part of the reason for this trend includes improvements in the availability of CT scanners and more timely access to them. Helical scanning technology has also greatly increased the quality and usefulness of the information CT provides. Most uncomplicated cases of acute renal infection in adults do not require imaging for diagnosis and treatment. When imaging is indicated, however, contrast-enhanced CT almost always is the study of choice. For cases in which renal calculi may be present, the study should also include noncontrast images through the kidneys.