Presented by: Sharon Fihsberg MD
Hadassah Medical Center and The Hebrew University of Jerusalem

Introduction

The gold standard study for evaluating suspected obstructed kidney is non contrast computerized tomography (CT).  However, hydronephrosis, especially when the cause can not be identified, is not always a sign of obstruction. Obstructed kidney becomes edematous, a pathological process represented by increasing amount of fluid inside the kidney parenchyma and in the adjacent perirenal fat.  The radiodensity of the obstructed kidney parenchyma and perirenal fat is measured in Hounsfield units.

The objective of this study is to compare the density of an obstructed kidney to the a non-obstructed counterpart during acute one sided ureteral calculi obstruction.

Materials

This is a retrospective comperative study. The study group included patients admitted with renal colic due to one sided obstructing ureteral calculi (group1), and the control group included patients with non-obstructing kidney stone (group 2). In each group clinical and radiological characteristics were collected. The radiodenisty of 3 parenchymal areas (upper pole, interpolar and lower pole) were measured and averaged, and then compared with the contralateral kidney. The average parenchymal density difference was calculated by subtracting the average parenchymal density of the obstructed kidney from the parenchymal density of the non-obstructed kidney, we repeated this process for the perirenal fat.

Results

,

One hundred patients, 50 in each group were included in this study. Femal to male ratio was 11/39 and 13/37 in group 1 and 2 respectively. The average age in group 1 was 47.1 years compared to 52.5 years in the control. The average parenchymal density difference in group 1 was 4.38 HU compared to 1.12 HU in the control group (p value <0.0001). An even more significant difference was found comparing the average perirenal fat density difference – in group 1, the average perirenal fat density difference was 11.13 HU compare to only 2.06 HU in the control group (p value <0.0001).  We didn’t find any significant difference comparing age, gender, stone size and stone location.

Conclusion

In case of a single side ureteral obstruction, the obstructed kidney and the perirenal fat are characterized by a significant lower density than the contralateral kidney. These radiological signs from a non-contract abdominal CT, can help the clinician to differentiate anatomical- hydroneprosis without obstruction from functional obstruction.  This data is usually available on the first admission to emergency department, saving time and expenses when the diagnosis is uncertain.

Funding

No funding was recieved for this work

Co-Authors

Gabriel Molineros, MD
Hadassah Medical Center and The Hebrew University of Jerusalem

Eliyahu Heifetz, PHD
Department of Accounting and Data Management, Lev Academic Center

Amitay Lorber, MD
Hadassah Medical Center and The Hebrew University of Jerusalem

Guy Hidas, MD
Hadassah Medical Center and The Hebrew University of Jerusalem

Ofer Gofrit, MD PHD
Hadassah Medical Center and The Hebrew University of Jerusalem

Mordechai Duvdevani, MD
Hadassah Medical Center and The Hebrew University of Jerusalem